blob: e438a1fca55488e1cc9d24b5bcb924ef43dd33d5 [file] [log] [blame]
Al Stoneb10d79f2015-03-24 14:02:41 +00001 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -08002 Advanced Configuration and Power Interface
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02003 Format: { force | on | off | strict | noirq | rsdt |
Rami Rosene58d1542015-09-26 19:27:57 +03004 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 force -- enable ACPI if default was off
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02006 on -- enable ACPI but allow fallback to DT [arm64]
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07009 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +080011 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +080012 copy_dsdt -- copy DSDT to memory
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +020013 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14 are available
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Paul Bolle395cf962011-08-15 02:02:26 +020016 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
Len Browna1fdcc02007-03-11 03:26:14 -040018 acpi_apic_instance= [ACPI, IOAPIC]
19 Format: <int>
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -040022 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -040023
Thomas Renningerc3d6de62008-08-01 17:37:55 +020024 acpi_backlight= [HW,ACPI]
25 acpi_backlight=vendor
26 acpi_backlight=video
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
30
Colin Ian Kingb2ca5da2016-01-21 17:05:47 +000031 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
36
Dominik Brodowskief694492015-05-14 15:31:28 +020037 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
44
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070045 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070048 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -060055 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Bjorn Helgaase76f4272008-11-13 17:30:13 -060059 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070063 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070066 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +020068
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070069 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +080072
Dominik Brodowskief694492015-05-14 15:31:28 +020073 acpi_enforce_resources= [ACPI]
74 { strict | lax | no }
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
88
Lv Zheng4fc0a7e2014-05-31 08:15:02 +080089 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
92 size limitation.
93
Randy Dunlap0cb55ad2009-04-05 15:55:22 -070094 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
96 default in APIC mode
97
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
100 default in PIC mode
101
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
104
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
106 use by PCI
107 Format: <irq>,<irq>...
108
Lv Zheng9c4aa1e2016-12-16 12:07:57 +0800109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
113 the GPE dispatcher.
114 This facility can be used to prevent such uncontrolled
115 GPE floodings.
116 Format: <int>
117 Support masking of GPEs numbered from 0x00 to 0x7f.
118
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800124 This feature is enabled by default.
125 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800126
Dominik Brodowskief694492015-05-14 15:31:28 +0200127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
128 kernels.
129
Lv Zhenga94e88c2014-04-04 12:39:11 +0800130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700139
Dominik Brodowskief694492015-05-14 15:31:28 +0200140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800144
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
147
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
153
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800157 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800158 acpi_osi=! # disable all built-in OS vendor
159 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800160 acpi_osi=!! # enable all built-in OS vendor
161 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700162 acpi_osi= # disable all strings
163
Lv Zheng5dc17982013-07-22 16:08:25 +0800164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800174 Examples:
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
178
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
184 meaningless.
185 Examples:
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
187 FALSE.
188
Lv Zheng741d8122013-07-22 16:08:36 +0800189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
199 the OSPM features.
200 Examples:
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 equivalent to
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 and
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
211
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530212 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
216
Randy Dunlap4af94f32009-04-17 18:30:28 -0700217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
219
Randy Dunlap4af94f32009-04-17 18:30:28 -0700220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
223
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200226 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700227 See Documentation/power/video.txt for information on
228 s3_bios and s3_mode.
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700242
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
246
Randy Dunlap4af94f32009-04-17 18:30:28 -0700247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
249
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700250 agp= [AGP]
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
255
Randy Dunlapbcfde332010-06-07 17:10:38 -0700256 ALSA [HW,ALSA]
257 See Documentation/sound/alsa/alsa-parameters.txt
258
Russell Kingd944d542010-02-20 16:13:29 +0000259 alignment= [KNL,ARM]
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
263
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
271
Borislav Petkov8360ee22011-11-21 12:10:19 +0100272 32: only for 32-bit processes
273 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
276
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
283
Sedat Dilek89e0b9a32011-12-05 23:08:32 +0100284 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200285 Pass parameters to the AMD IOMMU driver in the system.
286 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
290 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200291 off - do not initialize any AMD IOMMU found in
292 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900298
Shuah Khanc099cf12012-05-24 15:58:25 -0600299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
304
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
307 remapping modes:
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
313
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
316 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200317 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
323
Randy Dunlapa9913042005-10-23 12:57:11 -0700324 apc= [HW,SPARC]
325 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 Format: noidle
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
330
Randy Dunlapca1eda22009-05-06 16:02:58 -0700331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700332 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700336
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
341 backup of CPU 0
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
344 shot down by NMI
345
Brian Haleyb0f83b22010-02-04 13:36:50 -0800346 autoconf= [IPV6]
347 See Documentation/networking/ipv6.txt.
348
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
357
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700359 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
363
364 ataflop= [HW,M68k]
365
366 atarimouse= [HW,MOUSE] Atari Mouse
367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
370
371 atkbd.reset= [HW] Reset keyboard during initialization
372
Randy Dunlapa9913042005-10-23 12:57:11 -0700373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
378
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700381
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
394 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400395 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400396
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
399 Default: 64
400
Alex Thorlton1c532e02016-03-31 14:18:29 -0500401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
404 0 - Disable the BAU.
405 1 - Enable the BAU.
406 unset - Disable the BAU.
407
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 baycom_epp= [HW,AX25]
409 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700410
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
412 Format: <io>,<mode>
413 See header of drivers/net/hamradio/baycom_par.c.
414
Randy Dunlapa9913042005-10-23 12:57:11 -0700415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
419
Randy Dunlapa9913042005-10-23 12:57:11 -0700420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
424
Paul Gortmaker080506a2013-09-30 13:45:19 -0700425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
428
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
431 no delay (0).
432 Format: integer
433
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
435
Huang Yinga3e2acc2016-06-29 13:04:29 -0700436 bert_disable [ACPI]
437 Disable BERT OS support on buggy BIOSes.
438
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700440 bttv.radio= Most important insmod options are available as
441 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200443 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
447 at a time.
448
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 c101= [NET] Moxa C101 synchronous serial card
450
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
457
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
460 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300461 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300462
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
467 others).
468
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
Paul Menage8bab8dd2008-04-04 14:29:57 -0700472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
476 a single hierarchy
477 - foo isn't visible as an individually mountable
478 subsystem
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700482
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
487
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
489 Format: <string>
490 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800491 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700500 Value can be changed at runtime via
501 /selinux/checkreqprot.
502
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100503 cio_ignore= [S390]
504 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700505 clk_ignore_unused
506 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100516
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700518 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200519 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700520 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200521 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 Format: { pit | tsc | cyclone | pmtmr }
523
John Stultz592913e2010-07-13 17:56:20 -0700524 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700525 Format: <string>
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
529 the platform:
530 [all] jiffies (this is the base, fallback clocksource)
531 [ACPI] acpi_pm
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
Alok Kataria9863c902010-08-23 14:49:11 -0700534 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700535 scx200_hrt on Geode; cyclone on IBM x440
536 [MIPS] MIPS
537 [PARISC] cr16
538 [S390] tod
539 [SH] SuperH
540 [SPARC64] tick
541 [X86-64] hpet,tsc
542
Will Deacon46fd5c62016-06-27 17:30:13 +0100543 clocksource.arm_arch_timer.evtstrm=
544 [ARM,ARM64]
545 Format: <bool>
546 Enable/disable the eventstream feature of the ARM
547 architected timer so that code using WFE-based polling
548 loops can be debugged more effectively on production
549 systems.
550
Andi Kleenac72e782008-01-30 13:33:21 +0100551 clearcpuid=BITNUM [X86]
552 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100553 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800554 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100555 stable over kernel options, but the vendor specific
556 ones should be.
557 Also note that user programs calling CPUID directly
558 or using the feature without checking anything
559 will still see it. This just prevents it from
560 being used by the kernel or shown in /proc/cpuinfo.
561 Also note the kernel might malfunction if you disable
562 some critical bits.
563
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700564 cma=nn[MG]@[start[MG][-end[MG]]]
565 [ARM,X86,KNL]
566 Sets the size of kernel global memory area for
567 contiguous memory allocations and optionally the
568 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700569 memory allocations. A value of 0 disables CMA
570 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100571 include/linux/dma-contiguous.h
572
Robert Jennings14f966e2009-04-15 05:55:32 +0000573 cmo_free_hint= [PPC] Format: { yes | no }
574 Specify whether pages are marked as being inactive
575 when they are freed. This is used in CMO environments
576 to determine OS memory pressure for page stealing by
577 a hypervisor.
578 Default: yes
579
Marek Szyprowskic7909502011-12-29 13:09:51 +0100580 coherent_pool=nn[KMG] [ARM,KNL]
581 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200582 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100583
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530584 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100585 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100586 Range: 0 - 8192
587 Default: 64
588
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700590 Format:
591 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592
593 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
594 Format: <io>[,<irq>]
595
Randy Dunlapa9913042005-10-23 12:57:11 -0700596 com90xx= [HW,NET]
597 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 Format: <io>[,<irq>[,<memstart>]]
599
600 condev= [HW,S390] console device
601 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700602
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603 console= [KNL] Output console device and options.
604
605 tty<n> Use the virtual console device <n>.
606
607 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800608 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800610 the form "bbbbpnf", where "bbbb" is the baud rate,
611 "p" is parity ("n", "o", or "e"), "n" is number of
612 bits, and "f" is flow control ("r" for RTS or
613 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614
Jani Nikulae52347b2016-11-03 12:10:10 +0200615 See Documentation/admin-guide/serial-console.rst for more
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800616 information. See
617 Documentation/networking/netconsole.txt for an
618 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700620 uart[8250],io,<addr>[,options]
621 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900622 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400623 uart[8250],mmio32,<addr>[,options]
624 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 Start an early, polled-mode console on the 8250/16550
626 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400627 switching to the matching ttyS device later.
628 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900629 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
630 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
631 to be equivalent to 'mmio'. 'options' are specified in
632 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400633 the h/w is not re-initialized.
634
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500635 hvc<n> Use the hypervisor console device <n>. This is for
636 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700637
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700638 If the device connected to the port is not a TTY but a braille
639 device, prepend "brl," before the device type, for instance
640 console=brl,ttyS0
641 For now, only VisioBraille is supported.
642
Daniel Mackf324edc2009-06-16 15:33:52 -0700643 consoleblank= [KNL] The console blank (screen saver) timeout in
644 seconds. Defaults to 10*60 = 10mins. A value of 0
645 disables the blank timer.
646
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800647 coredump_filter=
648 [KNL] Change the default value for
649 /proc/<pid>/coredump_filter.
650 See also Documentation/filesystems/proc.txt.
651
Len Brown62027ae2011-04-01 18:13:10 -0400652 cpuidle.off=1 [CPU_IDLE]
653 disable the cpuidle sub-system
654
Len Brownd82f2692017-02-28 16:44:16 -0500655 cpufreq.off=1 [CPU_FREQ]
656 disable the cpufreq sub-system
657
Len Brownd68921f2015-05-11 17:27:09 -0400658 cpu_init_udelay=N
659 [X86] Delay for N microsec between assert and de-assert
660 of APIC INIT to start processors. This delay occurs
661 on every CPU online, such as boot, and resume from suspend.
662 Default: 10000
663
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700665 Format:
666 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800668 crashkernel=size[KMG][@offset[KMG]]
669 [KNL] Using kexec, Linux can switch to a 'crash kernel'
670 upon panic. This parameter reserves the physical
671 memory region [offset, offset + size] for that kernel
672 image. If '@offset' is omitted, then a suitable offset
673 is selected automatically. Check
674 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700675
Bernhard Wallefb391592007-10-18 23:41:02 -0700676 crashkernel=range1:size1[,range2:size2,...][@offset]
677 [KNL] Same as above, but depends on the memory
678 in the running system. The syntax of range is
679 start-[end] where start and end are both
680 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800681 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700682
Yinghai Luadbc7422013-04-15 22:23:48 -0700683 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700684 [KNL, x86_64] range could be above 4G. Allow kernel
685 to allocate physical memory region from top, so could
686 be above 4G if system have more than 4G ram installed.
687 Otherwise memory region will be allocated below 4G, if
688 available.
689 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700690 crashkernel=size[KMG],low
691 [KNL, x86_64] range under 4G. When crashkernel=X,high
692 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700693 above 4G, that cause second kernel crash on system
694 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800695 requires at least 64M+32K low memory, also enough extra
696 low memory is needed to make sure DMA buffers for 32-bit
697 devices won't run out. Kernel would try to allocate at
698 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700699 This one let user to specify own low range under 4G
700 for second kernel instead.
701 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700702 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700703 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700704
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100705 cryptomgr.notests
706 [KNL] Disable crypto self-tests
707
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708 cs89x0_dma= [HW,NET]
709 Format: <dma>
710
711 cs89x0_media= [HW,NET]
712 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700713
Randy Dunlapa9913042005-10-23 12:57:11 -0700714 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 See header of drivers/s390/block/dasd_devmap.c.
716
717 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
718 (one device per port)
719 Format: <port#>,<type>
720 See also Documentation/input/joystick-parport.txt
721
Thomas Renningera648ec02010-08-06 16:11:02 +0200722 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
723 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600724 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200725
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726 debug [KNL] Enable kernel debugging (events log level).
727
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700728 debug_locks_verbose=
729 [KNL] verbose self-tests
730 Format=<0|1>
731 Print debugging info while doing the locking API
732 self-tests.
733 We default to 0 (no extra messages), setting it to
734 1 will print _a lot_ more information - normally
735 only useful to kernel developers.
736
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700737 debug_objects [KNL] Enable object debugging
738
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500739 no_debug_objects
740 [KNL] Disable object debugging
741
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800742 debug_guardpage_minorder=
743 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
744 parameter allows control of the order of pages that will
745 be intentionally kept free (and hence protected) by the
746 buddy allocator. Bigger value increase the probability
747 of catching random memory corruption, but reduce the
748 amount of memory for normal system use. The maximum
749 possible value is MAX_ORDER/2. Setting this parameter
750 to 1 or 2 should be enough to identify most random
751 memory corruption problems caused by bugs in kernel or
752 driver code when a CPU writes to (or reads from) a
753 random memory location. Note that there exists a class
754 of memory corruptions problems caused by buggy H/W or
755 F/W or by drivers badly programing DMA (basically when
756 memory is written at bus level and the CPU MMU is
757 bypassed) which are not detectable by
758 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
759 tracking down these problems.
760
Joonsoo Kim031bc572014-12-12 16:55:52 -0800761 debug_pagealloc=
762 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
763 parameter enables the feature at boot time. In
764 default, it is disabled. We can avoid allocating huge
765 chunk of memory for debug pagealloc if we don't enable
766 it at boot time and the system will work mostly same
767 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
768 on: enable the feature
769
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200770 debugpat [X86] Enable PAT debugging
771
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200772 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773 Format: <area>[,<node>]
774 See also Documentation/networking/decnet.txt.
775
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700776 default_hugepagesz=
777 [same as hugepagesz=] The size of the default
778 HugeTLB page size. This is the size represented by
779 the legacy /proc/ hugepages APIs, used for SHM, and
780 default size when mounting hugetlbfs filesystems.
781 Defaults to the default architecture's huge page size
782 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700783
Linus Torvalds1da177e2005-04-16 15:20:36 -0700784 dhash_entries= [KNL]
785 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700786
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000787 disable_1tb_segments [PPC]
788 Disables the use of 1TB hash page table segments. This
789 causes the kernel to fall back to 256MB segments which
790 can be useful when debugging issues that require an SLB
791 miss to occur.
792
Brian Haleyb0f83b22010-02-04 13:36:50 -0800793 disable= [IPV6]
794 See Documentation/networking/ipv6.txt.
795
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530796 disable_radix [PPC]
797 Disable RADIX MMU mode on POWER9
798
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900799 disable_cpu_apicid= [X86,APIC,SMP]
800 Format: <int>
801 The number of initial APIC ID for the
802 corresponding CPU to be disabled at boot,
803 mostly used for the kdump 2nd kernel to
804 disable BSP to wake up multiple CPUs without
805 causing system reset or hang due to sending
806 INIT from AP to BSP.
807
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000808 disable_ddw [PPC/PSERIES]
809 Disable Dynamic DMA Window support. Use this if
810 to workaround buggy firmware.
811
Brian Haleyb0f83b22010-02-04 13:36:50 -0800812 disable_ipv6= [IPV6]
813 See Documentation/networking/ipv6.txt.
814
Yinghai Lu95ffa242008-04-29 03:52:33 -0700815 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700816 The kernel tries to adjust MTRR layout from continuous
817 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700818 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700819
Yinghai Lu093af8d2008-01-30 13:33:32 +0100820 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100821 By default the kernel will trim any uncacheable
822 memory out of your available memory pool based on
823 MTRR settings. This parameter disables that behavior,
824 possibly causing your machine to run very slowly.
825
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530826 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700827 Disable PIN 1 of APIC timer
828 Can be useful to work around chipset bugs.
829
Prarit Bhargavace14c582015-08-25 13:34:53 -0400830 dis_ucode_ldr [X86] Disable the microcode loader.
831
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700832 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
833 this option disables the debugging code at boot.
834
835 dma_debug_entries=<number>
836 This option allows to tune the number of preallocated
837 entries for DMA-API debugging code. One entry is
838 required per DMA-API allocation. Use this if the
839 DMA-API debugging code disables itself because the
840 architectural default is too low.
841
Joerg Roedel1745de52009-05-22 21:49:51 +0200842 dma_debug_driver=<driver_name>
843 With this option the DMA-API debugging driver
844 filter feature can be enabled at boot time. Just
845 pass the driver to filter for as the parameter.
846 The filter can be disabled or changed to another
847 driver later using sysfs.
848
Bob Paauwe96206e22015-08-27 10:04:13 -0700849 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
850 Broken monitors, graphic adapters, KVMs and EDIDless
851 panels may send no or incorrect EDID data sets.
852 This parameter allows to specify an EDID data sets
853 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100854 Generic built-in EDID data sets are used, if one of
855 edid/1024x768.bin, edid/1280x1024.bin,
856 edid/1680x1050.bin, or edid/1920x1080.bin is given
857 and no file with the same name exists. Details and
858 instructions how to build your own EDID data are
859 available in Documentation/EDID/HOWTO.txt. An EDID
860 data set will only be used for a particular connector,
861 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700862 name. Each connector may use a unique EDID data
863 set by separating the files with a comma. An EDID
864 data set with no connector name will be used for
865 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100866
Linus Torvalds1da177e2005-04-16 15:20:36 -0700867 dscc4.setup= [NET]
868
Lukas Wunner58c54752016-11-12 21:32:36 +0000869 dump_apple_properties [X86]
870 Dump name and content of EFI device properties on
871 x86 Macs. Useful for driver authors to determine
872 what data is available or for reverse-engineering.
873
Jim Cromie29e36c92012-04-27 14:30:41 -0600874 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
875 module.dyndbg[="val"]
876 Enable debug messages at boot time. See
877 Documentation/dynamic-debug-howto.txt for details.
878
Dave Hansen8c3641e2015-06-07 11:37:02 -0700879 nompx [X86] Disables Intel Memory Protection Extensions.
880 See Documentation/x86/intel_mpx.txt for more
881 information about the feature.
882
Dave Hansen06976942016-02-12 13:02:29 -0800883 nopku [X86] Disable Memory Protection Keys CPU feature found
884 in some Intel CPUs.
885
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700886 module.async_probe [KNL]
887 Enable asynchronous probe on this module.
888
Mark Salter56aeeba2014-04-07 15:39:53 -0700889 early_ioremap_debug [KNL]
890 Enable debug messages in early_ioremap support. This
891 is useful for tracking down temporary early mappings
892 which are not unmapped.
893
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700894 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500895
Scott Wood5664f762015-09-14 19:54:07 -0500896 When used with no options, the early console is
897 determined by the stdout-path property in device
898 tree's chosen node.
899
Scott Telfordc41251b2016-09-22 16:58:16 +0100900 cdns,<addr>[,options]
901 Start an early, polled-mode console on a Cadence
902 (xuartps) serial port at the specified address. Only
903 supported option is baud rate. If baud rate is not
904 specified, the serial port must already be setup and
905 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +0200906
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700907 uart[8250],io,<addr>[,options]
908 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700909 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300910 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400911 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700912 Start an early, polled-mode console on the 8250/16550
913 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700914 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300915 (mmio) or 32-bit (mmio32 or mmio32be).
916 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
917 to be equivalent to 'mmio'. 'options' are specified
918 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400919 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700920
Rob Herring0d3c6732014-04-18 17:19:57 -0500921 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -0600922 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -0500923 Start an early, polled-mode console on a pl011 serial
924 port at the specified address. The pl011 serial port
925 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -0600926 yet supported. If 'mmio32' is specified, then only
927 the driver will use only 32-bit accessors to read/write
928 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -0500929
Andreas Färber736d5532016-03-06 12:21:24 +0100930 meson,<addr>
931 Start an early, polled-mode console on a meson serial
932 port at the specified address. The serial port must
933 already be setup and configured. Options are not yet
934 supported.
935
Stephen Boyd0efe7292014-09-15 17:22:51 -0700936 msm_serial,<addr>
937 Start an early, polled-mode console on an msm serial
938 port at the specified address. The serial port
939 must already be setup and configured. Options are not
940 yet supported.
941
942 msm_serial_dm,<addr>
943 Start an early, polled-mode console on an msm serial
944 dm port at the specified address. The serial port
945 must already be setup and configured. Options are not
946 yet supported.
947
Rob Herringd50d7262014-04-18 17:19:58 -0500948 smh Use ARM semihosting calls for early console.
949
Tomasz Figab94ba032015-01-23 14:47:41 +0100950 s3c2410,<addr>
951 s3c2412,<addr>
952 s3c2440,<addr>
953 s3c6400,<addr>
954 s5pv210,<addr>
955 exynos4210,<addr>
956 Use early console provided by serial driver available
957 on Samsung SoCs, requires selecting proper type and
958 a correct base address of the selected UART port. The
959 serial port must already be setup and configured.
960 Options are not yet supported.
961
Martin Blumenstinglec84aa02016-12-11 21:42:23 +0100962 lantiq,<addr>
963 Start an early, polled-mode console on a lantiq serial
964 (lqasc) port at the specified address. The serial port
965 must already be setup and configured. Options are not
966 yet supported.
967
Stefan Agner1d59b382015-10-17 00:45:55 -0700968 lpuart,<addr>
969 lpuart32,<addr>
970 Use early console provided by Freescale LP UART driver
971 found on Freescale Vybrid and QorIQ LS1021A processors.
972 A valid base address must be provided, and the serial
973 port must already be setup and configured.
974
Andre Przywaraf7c864e2017-05-04 00:49:36 +0100975 ar3700_uart,<addr>
Wilson Ding30530792016-02-16 19:14:53 +0100976 Start an early, polled-mode console on the
977 Armada 3700 serial port at the specified
978 address. The serial port must already be setup
979 and configured. Options are not yet supported.
980
Heiko Carstens89175cf2017-01-11 09:14:52 +0100981 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100983 earlyprintk=efi
Heiko Carstens89175cf2017-01-11 09:14:52 +0100984 earlyprintk=sclp
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500985 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700986 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700987 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500988 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500989 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +0600990 earlyprintk=pciserial,bus:device.function[,baudrate]
Lu Baolu1b5aeeb2017-03-21 16:01:31 +0800991 earlyprintk=xdbc[xhciController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992
Dave Hansen147ea092013-04-10 14:03:38 -0700993 earlyprintk is useful when the kernel crashes before
994 the normal console is initialized. It is not enabled by
995 default because it has some cosmetic problems.
996
Randy Dunlapa9913042005-10-23 12:57:11 -0700997 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998 takes over.
999
Matt Fleming72548e82013-10-04 09:36:56 +01001000 Only one of vga, efi, serial, or usb debug port can
1001 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002
Dave Hansen147ea092013-04-10 14:03:38 -07001003 Currently only ttyS0 and ttyS1 may be specified by
1004 name. Other I/O ports may be explicitly specified
1005 on some architectures (x86 and arm at least) by
1006 replacing ttySn with an I/O port address, like this:
1007 earlyprintk=serial,0x1008,115200
1008 You can find the port for a given device in
1009 /proc/tty/driver/serial:
1010 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011
1012 Interaction with the standard serial driver is not
1013 very good.
1014
Matt Fleming72548e82013-10-04 09:36:56 +01001015 The VGA and EFI output is eventually overwritten by
1016 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001018 The xen output can only be used by Xen PV guests.
1019
Heiko Carstens89175cf2017-01-11 09:14:52 +01001020 The sclp output can only be used on s390.
1021
Chen, Gongc700f012013-12-06 01:17:08 -05001022 edac_report= [HW,EDAC] Control how to report EDAC event
1023 Format: {"on" | "off" | "force"}
1024 on: enable EDAC to report H/W event. May be overridden
1025 by other higher priority error reporting module.
1026 off: disable H/W event reporting through EDAC.
1027 force: enforce the use of EDAC to report H/W event.
1028 default: on.
1029
Jason Wessel97311912010-05-20 21:04:30 -05001030 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1031 ekgdboc=kbd
1032
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001033 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001034 the boot argument: earlyprintk=vga
1035
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001037 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001039 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001040 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001041 old_map [X86-64]: switch to the old ioremap-based EFI
1042 runtime services mapping. 32-bit still uses this one by
1043 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001044 nochunk: disable reading files in "chunks" in the EFI
1045 boot stub, as chunking can cause problems with some
1046 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001047 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001048 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001049
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001050 efi_no_storage_paranoia [EFI; X86]
1051 Using this parameter you can use more than 50% of
1052 your efi variable storage. Use this parameter only if
1053 you are really sure that your UEFI does sane gc and
1054 fulfills the spec otherwise your board may brick.
1055
Taku Izumi0f96a992015-09-30 23:01:56 +09001056 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1057 Add arbitrary attribute to specific memory range by
1058 updating original EFI memory map.
1059 Region of memory which aa attribute is added to is
1060 from ss to ss+nn.
1061 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1062 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1063 attribute is added to range 0x100000000-0x180000000 and
1064 0x10a0000000-0x1120000000.
1065
1066 Using this parameter you can do debugging of EFI memmap
1067 related feature. For example, you can do debugging of
1068 Address Range Mirroring feature even if your box
1069 doesn't support it.
1070
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001071 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1072 that is to be dynamically loaded by Linux. If there are
1073 multiple variables with the same name but with different
1074 vendor GUIDs, all of them will be loaded. See
1075 Documentation/acpi/ssdt-overlays.txt for details.
1076
1077
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 eisa_irq_edge= [PARISC,HW]
1079 See header of drivers/parisc/eisa.c.
1080
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001081 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001083 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084
1085 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001086 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001087 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001088 Documentation/block/deadline-iosched.txt for details.
1089
Michael Holzheud3bf37952011-10-30 15:16:37 +01001090 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001091 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001092 image elf header and optionally the size. Generally
1093 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001094 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001096 enable_mtrr_cleanup [X86]
1097 The kernel tries to adjust MTRR layout from continuous
1098 to discrete, to make X server driver able to add WB
1099 entry later. This parameter enables that.
1100
Randy Dunlapca1eda22009-05-06 16:02:58 -07001101 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001102 Enable PIN 1 of APIC timer
1103 Can be useful to work around chipset bugs
1104 (in particular on some ATI chipsets).
1105 The kernel tries to set a reasonable default.
1106
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 enforcing [SELINUX] Set initial enforcing status.
1108 Format: {"0" | "1"}
1109 See security/selinux/Kconfig help text.
1110 0 -- permissive (log only, no denials).
1111 1 -- enforcing (deny and log).
1112 Default value is 0.
1113 Value can be changed at runtime via /selinux/enforce.
1114
Huang Yinga08f82d2010-05-18 14:35:21 +08001115 erst_disable [ACPI]
1116 Disable Error Record Serialization Table (ERST)
1117 support.
1118
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 ether= [HW,NET] Ethernet cards parameters
1120 This option is obsoleted by the "netdev=" option, which
1121 has equivalent usage. See its documentation for details.
1122
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001123 evm= [EVM]
1124 Format: { "fix" }
1125 Permit 'security.evm' to be updated regardless of
1126 current integrity status.
1127
Akinobu Mitade1ba092006-12-08 02:39:42 -08001128 failslab=
1129 fail_page_alloc=
1130 fail_make_request=[KNL]
1131 General fault injection mechanism.
1132 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001133 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001134
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001136 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137
Alex Chiangf13ae302008-05-08 14:03:23 -06001138 force_pal_cache_flush
1139 [IA-64] Avoid check_sal_cache_flush which may hang on
1140 buggy SAL_CACHE_FLUSH implementations. Using this
1141 parameter will force ia64_sal_cache_flush to call
1142 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1143
Chris Bainbridge69f23662014-03-07 18:40:42 +07001144 forcepae [X86-32]
1145 Forcefully enable Physical Address Extension (PAE).
1146 Many Pentium M systems disable PAE but may have a
1147 functionally usable PAE implementation.
1148 Warning: use of this parameter will taint the kernel
1149 and may cause unknown problems.
1150
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001151 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001152 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001153 as early as possible in order to facilitate early
1154 boot debugging.
1155
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001156 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001157 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001158 If no parameter is passed, ftrace will dump
1159 buffers of all CPUs, but if you pass orig_cpu, it will
1160 dump only the buffer of the CPU that triggered the
1161 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001162
1163 ftrace_filter=[function-list]
1164 [FTRACE] Limit the functions traced by the function
1165 tracer at boot up. function-list is a comma separated
1166 list of functions. This list can be changed at run
1167 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001168 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001169
1170 ftrace_notrace=[function-list]
1171 [FTRACE] Do not trace the functions specified in
1172 function-list. This list can be changed at run time
1173 by the set_ftrace_notrace file in the debugfs
1174 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001175
Stefan Assmann369bc182009-10-12 22:17:21 +02001176 ftrace_graph_filter=[function-list]
1177 [FTRACE] Limit the top level callers functions traced
1178 by the function graph tracer at boot up.
1179 function-list is a comma separated list of functions
1180 that can be changed at run time by the
1181 set_graph_function file in the debugfs tracing directory.
1182
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001183 ftrace_graph_notrace=[function-list]
1184 [FTRACE] Do not trace from the functions specified in
1185 function-list. This list is a comma separated list of
1186 functions that can be changed at run time by the
1187 set_graph_notrace file in the debugfs tracing directory.
1188
Todd Brandt65a50c62017-03-02 16:12:15 -08001189 ftrace_graph_max_depth=<uint>
1190 [FTRACE] Used with the function graph tracer. This is
1191 the max depth it will trace into a function. This value
1192 can be changed at run time by the max_graph_depth file
1193 in the tracefs tracing directory. default: 0 (no limit)
1194
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 gamecon.map[2|3]=
1196 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1197 support via parallel port (up to 5 devices per port)
1198 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1199 See also Documentation/input/joystick-parport.txt
1200
1201 gamma= [HW,DRM]
1202
Yinghai Luaaf23042008-01-30 13:33:09 +01001203 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1204 Format: off | on
1205 default: on
1206
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001207 gcov_persist= [GCOV] When non-zero (default), profiling data for
1208 kernel modules is saved and remains accessible via
1209 debugfs, even when the module is unloaded/reloaded.
1210 When zero, profiling data is discarded and associated
1211 debugfs files are removed at module unload time.
1212
Thomas Gleixner47512cf2017-02-15 11:11:50 +01001213 goldfish [X86] Enable the goldfish android emulator platform.
1214 Don't use this when you are not running on the
1215 android emulator
1216
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001218 invalid Protective MBR to be treated as GPT. If the
1219 primary GPT is corrupted, it enables the backup/alternate
1220 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001222 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1223 the "Enable 0" bit of the configuration register.
1224 Format: 0 | 1
1225 Default: 0
1226 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1227 the "Enable 0" bit of the configuration register.
1228 Format: 0 | 1
1229 Default: 0
1230 grcan.select= [HW] Select which physical interface to use.
1231 Format: 0 | 1
1232 Default: 0
1233 grcan.txsize= [HW] Sets the size of the tx buffer.
1234 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1235 Default: 1024
1236 grcan.rxsize= [HW] Sets the size of the rx buffer.
1237 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1238 Default: 1024
1239
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001240 gpio-mockup.gpio_mockup_ranges
1241 [HW] Sets the ranges of gpiochip of for this device.
1242 Format: <start1>,<end1>,<start2>,<end2>...
1243
Jiri Kosina55537872015-11-05 18:44:41 -08001244 hardlockup_all_cpu_backtrace=
1245 [KNL] Should the hard-lockup detector generate
1246 backtraces on all cpus.
1247 Format: <integer>
1248
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249 hashdist= [KNL,NUMA] Large hashes allocated during boot
1250 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001251 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001252 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253
1254 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1255
1256 hd= [EIDE] (E)IDE hard drive subsystem geometry
1257 Format: <cyl>,<head>,<sect>
1258
Huang Yingea8c0712010-05-18 14:35:15 +08001259 hest_disable [ACPI]
1260 Disable Hardware Error Source Table (HEST) support;
1261 corresponding firmware-first mode error processing
1262 logic will be disabled.
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1265 size of <nn>. This works even on boxes that have no
1266 highmem otherwise. This also works to reduce highmem
1267 size on bigger boxes.
1268
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001269 highres= [KNL] Enable/disable high resolution timer mode.
1270 Valid parameters: "on", "off"
1271 Default: "on"
1272
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273 hisax= [HW,ISDN]
1274 See Documentation/isdn/README.HiSax.
1275
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001276 hlt [BUGS=ARM,SH]
1277
1278 hpet= [X86-32,HPET] option to control HPET usage
1279 Format: { enable (default) | disable | force |
1280 verbose }
1281 disable: disable HPET and use PIT instead
1282 force: allow force enabled of undocumented chips (ICH4,
1283 VIA, nVidia)
1284 verbose: show contents of HPET registers during setup
1285
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001286 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1287 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1288
Andi Kleenb4718e62008-07-23 21:27:51 -07001289 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1290 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001291 On x86-64 and powerpc, this option can be specified
1292 multiple times interleaved with hugepages= to reserve
1293 huge pages of different sizes. Valid pages sizes on
1294 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001295 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001296
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001297 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1298 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001299 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1300 If specified, z/VM IUCV HVC accepts connections
1301 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001302
James Hoganfdabf522012-10-09 11:00:27 +01001303 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1304 hardware thread id mappings.
1305 Format: <cpu>:<hwthread>
1306
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001307 keep_bootcon [KNL]
1308 Do not unregister boot console at start. This is only
1309 useful for debugging when something happens in the window
1310 between unregistering the boot console and initializing
1311 the real console.
1312
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001313 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001314 or register an additional I2C bus that is not
1315 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001316 Format:
1317 <bus_id>,<clkrate>
1318
Jiri Kosina36d95732008-10-06 02:51:09 -04001319 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001320 i8042.unmask_kbd_data
1321 [HW] Enable printing of interrupt data from the KBD port
1322 (disabled by default, and as a pre-condition
1323 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001325 i8042.dumbkbd [HW] Pretend that controller can only read data from
1326 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 (Don't attempt to blink the leds)
1328 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001329 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001330 i8042.noloop [HW] Disable the AUX Loopback command while probing
1331 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001333 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1335 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001336 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e19242016-10-01 12:07:35 -07001337 i8042.reset [HW] Reset the controller during init, cleanup and
1338 suspend-to-ram transitions, only during s2r
1339 transitions, or never reset
1340 Format: { 1 | Y | y | 0 | N | n }
1341 1, Y, y: always reset controller
1342 0, N, n: don't ever reset controller
1343 Default: only on s2r transitions on x86; most other
1344 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001346 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347
1348 i810= [HW,DRM]
1349
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001350 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1351 indicates that the driver is running on unsupported
1352 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1354 does not match list of supported models.
1355 i8k.power_status
1356 [HW] Report power status in /proc/i8k
1357 (disabled by default)
1358 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1359 capability is set.
1360
Carsten Emde4dca20e2012-03-15 15:56:26 +01001361 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001362 [DRM] Invert the sense of the variable that is used to
1363 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001364 brightness value of 0 indicates backlight switched off,
1365 and the maximum of the brightness value sets the backlight
1366 to maximum brightness. If this parameter is set to 0
1367 (default) and the machine requires it, or this parameter
1368 is set to 1, a brightness value of 0 sets the backlight
1369 to maximum brightness, and the maximum of the brightness
1370 value switches the backlight off.
1371 -1 -- never invert brightness
1372 0 -- machine default
1373 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001374
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375 icn= [HW,ISDN]
1376 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1377
David Fries0af80c02009-02-25 20:28:21 +01001378 ide-core.nodma= [HW] (E)IDE subsystem
1379 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001380 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1381 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001382 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001384 ide-generic.probe-mask= [HW] (E)IDE subsystem
1385 Format: <int>
1386 Probe mask for legacy ISA IDE ports. Depending on
1387 platform up to 6 ports are supported, enabled by
1388 setting corresponding bits in the mask to 1. The
1389 default value is 0x0, which has a special meaning.
1390 On systems that have PCI, it triggers scanning the
1391 PCI bus for the first and the second port, which
1392 are then probed. On systems without PCI the value
1393 of 0x0 enables probing the two first ports as if it
1394 was 0x3.
1395
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001396 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1397 Claim all unknown PCI IDE storage controllers.
1398
Andi Kleenf039b752007-05-02 19:27:12 +02001399 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001400 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001401 Poll forces a polling idle loop that can slightly
1402 improve the performance of waking up a idle CPU, but
1403 will use a lot of power and make the system run hot.
1404 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001405 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001406 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001407 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001408
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001409 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1410 Format: { strict | legacy | 2008 | relaxed }
1411 Default: strict
1412
1413 Choose which programs will be accepted for execution
1414 based on the IEEE 754 NaN encoding(s) supported by
1415 the FPU and the NaN encoding requested with the value
1416 of an ELF file header flag individually set by each
1417 binary. Hardware implementations are permitted to
1418 support either or both of the legacy and the 2008 NaN
1419 encoding mode.
1420
1421 Available settings are as follows:
1422 strict accept binaries that request a NaN encoding
1423 supported by the FPU
1424 legacy only accept legacy-NaN binaries, if supported
1425 by the FPU
1426 2008 only accept 2008-NaN binaries, if supported
1427 by the FPU
1428 relaxed accept any binaries regardless of whether
1429 supported by the FPU
1430
1431 The FPU emulator is always able to support both NaN
1432 encodings, so if no FPU hardware is present or it has
1433 been disabled with 'nofpu', then the settings of
1434 'legacy' and '2008' strap the emulator accordingly,
1435 'relaxed' straps the emulator for both legacy-NaN and
1436 2008-NaN, whereas 'strict' enables legacy-NaN only on
1437 legacy processors and both NaN encodings on MIPS32 or
1438 MIPS64 CPUs.
1439
1440 The setting for ABS.fmt/NEG.fmt instruction execution
1441 mode generally follows that for the NaN encoding,
1442 except where unsupported by hardware.
1443
Ingo Molnar792908222006-12-06 20:40:51 -08001444 ignore_loglevel [KNL]
1445 Ignore loglevel setting - this will print /all/
1446 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001447 We also add it as printk module parameter, so users
1448 could change it dynamically, usually by
1449 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001450
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001451 ignore_rlimit_data
1452 Ignore RLIMIT_DATA setting for data mappings,
1453 print warning at first misuse. Can be changed via
1454 /sys/module/kernel/parameters/ignore_rlimit_data.
1455
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 ihash_entries= [KNL]
1457 Set number of hash buckets for inode cache.
1458
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001459 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001460 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001461 default: "enforce"
1462
Mimi Zohar07f6a792011-03-09 22:25:48 -05001463 ima_appraise_tcb [IMA]
1464 The builtin appraise policy appraises all files
1465 owned by uid=0.
1466
Mimi Zohard68a6fe2016-12-19 16:22:57 -08001467 ima_canonical_fmt [IMA]
1468 Use the canonical format for the binary runtime
1469 measurements, instead of host native format.
1470
Mimi Zohar3323eec2009-02-04 09:06:58 -05001471 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001472 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1473 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001474 default: "sha1"
1475
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001476 The list of supported hash algorithms is defined
1477 in crypto/hash_info.h.
1478
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001479 ima_policy= [IMA]
Mimi Zohar33ce9542017-04-24 12:04:09 -04001480 The builtin policies to load during IMA setup.
Mimi Zohar503ceae2017-04-21 18:58:27 -04001481 Format: "tcb | appraise_tcb | secure_boot"
Mimi Zohar33ce9542017-04-24 12:04:09 -04001482
1483 The "tcb" policy measures all programs exec'd, files
1484 mmap'd for exec, and all files opened with the read
1485 mode bit set by either the effective uid (euid=0) or
1486 uid=0.
1487
1488 The "appraise_tcb" policy appraises the integrity of
1489 all files owned by root. (This is the equivalent
1490 of ima_appraise_tcb.)
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001491
Mimi Zohar503ceae2017-04-21 18:58:27 -04001492 The "secure_boot" policy appraises the integrity
1493 of files (eg. kexec kernel image, kernel modules,
1494 firmware, policy, etc) based on file signatures.
1495
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001496 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001497 Load a policy which meets the needs of the Trusted
1498 Computing Base. This means IMA will measure all
1499 programs exec'd, files mmap'd for exec, and all files
1500 opened for read by uid=0.
1501
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001502 ima_template= [IMA]
1503 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001504 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001505 Default: "ima-ng"
1506
Roberto Sassuc2426d22014-10-13 14:08:42 +02001507 ima_template_fmt=
1508 [IMA] Define a custom template format.
1509 Format: { "field1|...|fieldN" }
1510
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001511 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1512 Format: <min_file_size>
1513 Set the minimal file size for using asynchronous hash.
1514 If left unspecified, ahash usage is disabled.
1515
1516 ahash performance varies for different data sizes on
1517 different crypto accelerators. This option can be used
1518 to achieve the best performance for a particular HW.
1519
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001520 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1521 Format: <bufsize>
1522 Set hashing buffer size. Default: 4k.
1523
1524 ahash performance varies for different chunk sizes on
1525 different crypto accelerators. This option can be used
1526 to achieve best performance for particular HW.
1527
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 init= [KNL]
1529 Format: <full_path>
1530 Run specified binary instead of /sbin/init as init
1531 process.
1532
1533 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1534 for working out where the kernel is dying during
1535 startup.
1536
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001537 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1538 initcall functions. Useful for debugging built-in
1539 modules and initcalls.
1540
Linus Torvalds1da177e2005-04-16 15:20:36 -07001541 initrd= [BOOT] Specify the location of the initial ramdisk
1542
Dave Hansenacd547b2016-07-29 09:30:21 -07001543 init_pkru= [x86] Specify the default memory protection keys rights
1544 register contents for all processes. 0x55555554 by
1545 default (disallow access to all but pkey 0). Can
1546 override in debugfs after boot.
1547
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1549 Format: <irq>
1550
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001551 int_pln_enable [x86] Enable power limit notification interrupt
1552
Mimi Zohard726d8d2013-03-18 14:48:02 -04001553 integrity_audit=[IMA]
1554 Format: { "0" | "1" }
1555 0 -- basic integrity auditing messages. (Default)
1556 1 -- additional integrity auditing messages.
1557
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001558 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001559 on
1560 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001561 off
1562 Disable intel iommu driver.
1563 igfx_off [Default Off]
1564 By default, gfx is mapped as normal device. If a gfx
1565 device has a dedicated DMAR unit, the DMAR unit is
1566 bypassed by not enabling DMAR with this option. In
1567 this case, gfx device will use physical address for
1568 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001569 forcedac [x86_64]
1570 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001571 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001572 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001573 than 32-bit addressing. The default is to look
1574 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001575 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001576 strict [Default Off]
1577 With this option on every unmap_single operation will
1578 result in a hardware IOTLB flush operation as opposed
1579 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001580 sp_off [Default Off]
1581 By default, super page will be supported if Intel IOMMU
1582 has the capability. With this option, super page will
1583 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001584 ecs_off [Default Off]
1585 By default, extended context tables will be supported if
1586 the hardware advertises that it has support both for the
1587 extended tables themselves, and also PASID support. With
1588 this option set, extended tables will not be used even
1589 on hardware which claims to support them.
Shaohua Libfd20f12017-04-26 09:18:35 -07001590 tboot_noforce [Default Off]
1591 Do not force the Intel IOMMU enabled under tboot.
1592 By default, tboot will force Intel IOMMU on, which
1593 could harm performance of some high-throughput
1594 devices like 40GBit network cards, even if identity
1595 mapping is enabled.
1596 Note that using this option lowers the security
1597 provided by tboot because it makes the system
1598 vulnerable to DMA attacks.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001599
1600 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1601 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001602 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001603
Dirk Brandewie6be26492013-02-15 22:55:10 +01001604 intel_pstate= [X86]
1605 disable
1606 Do not enable intel_pstate as the default
1607 scaling driver for the supported processors
Rafael J. Wysocki001c76f2016-11-17 23:34:17 +01001608 passive
1609 Use intel_pstate as a scaling driver, but configure it
1610 to work with generic cpufreq governors (instead of
1611 enabling its internal governor). This mode cannot be
1612 used along with the hardware-managed P-states (HWP)
1613 feature.
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001614 force
1615 Enable intel_pstate on systems that prohibit it by default
1616 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1617 instead of acpi-cpufreq may disable platform features, such
1618 as thermal controls and power capping, that rely on ACPI
1619 P-States information being indicated to OSPM and therefore
1620 should be used with caution. This option does not work with
1621 processors that aren't supported by the intel_pstate driver
1622 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001623 no_hwp
1624 Do not enable hardware P state control (HWP)
1625 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001626 hwp_only
1627 Only load intel_pstate on systems which support
1628 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001629 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001630 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1631 Description Table, specifies preferred power management
1632 profile as "Enterprise Server" or "Performance Server",
1633 then this feature is turned on by default.
Srinivas Pandruvada22449c02016-10-25 13:20:43 -07001634 per_cpu_perf_limits
1635 Allow per-logical-CPU P-State performance control limits using
1636 cpufreq sysfs interface
Dirk Brandewie6be26492013-02-15 22:55:10 +01001637
Chris Wrightd1423d52010-07-20 11:06:49 -07001638 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001639 on enable Interrupt Remapping (default)
1640 off disable Interrupt Remapping
1641 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001642 no_x2apic_optout
1643 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001644 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001645
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001646 iomem= Disable strict checking of access to MMIO memory
1647 strict regions from userspace.
1648 relaxed
1649
1650 iommu= [x86]
1651 off
1652 force
1653 noforce
1654 biomerge
1655 panic
1656 nopanic
1657 merge
1658 nomerge
1659 forcesac
1660 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001661 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001662 nobypass [PPC/POWERNV]
1663 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001664
Will Deaconfccb4e32017-01-05 18:38:26 +00001665 iommu.passthrough=
1666 [ARM64] Configure DMA to bypass the IOMMU by default.
1667 Format: { "0" | "1" }
1668 0 - Use IOMMU translation for DMA.
1669 1 - Bypass the IOMMU for DMA.
1670 unset - Use IOMMU translation for DMA.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001671
1672 io7= [HW] IO7 for Marvel based alpha systems
1673 See comment before marvel_specify_io7 in
1674 arch/alpha/kernel/core_marvel.c.
1675
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301676 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001677 0x80
1678 Standard port 0x80 based delay
1679 0xed
1680 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001681 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001682 Simple two microseconds delay
1683 none
1684 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001685
Linus Torvalds1da177e2005-04-16 15:20:36 -07001686 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001687 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001689 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001690 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001691
Alan Cox200803d2005-06-28 20:45:18 -07001692 irqfixup [HW]
1693 When an interrupt is not handled search all handlers
1694 for it. Intended to get systems with badly broken
1695 firmware running.
1696
1697 irqpoll [HW]
1698 When an interrupt is not handled search all handlers
1699 for it. Also check all handlers each timer
1700 interrupt. Intended to get systems with badly broken
1701 firmware running.
1702
Linus Torvalds1da177e2005-04-16 15:20:36 -07001703 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001704 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705
1706 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001707 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001708
Linus Torvalds1da177e2005-04-16 15:20:36 -07001709 This option can be used to specify one or more CPUs
1710 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001711 algorithms. You can move a process onto or off an
1712 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713 <cpu number> begins at 0 and the maximum value is
1714 "number of CPUs in system - 1".
1715
1716 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001717 alternative -- manually setting the CPU mask of all
1718 tasks in the system -- can cause problems and
1719 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720
Randy Dunlapa9913042005-10-23 12:57:11 -07001721 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001723 ivrs_ioapic [HW,X86_64]
1724 Provide an override to the IOAPIC-ID<->DEVICE-ID
1725 mapping provided in the IVRS ACPI table. For
1726 example, to map IOAPIC-ID decimal 10 to
1727 PCI device 00:14.0 write the parameter as:
1728 ivrs_ioapic[10]=00:14.0
1729
1730 ivrs_hpet [HW,X86_64]
1731 Provide an override to the HPET-ID<->DEVICE-ID
1732 mapping provided in the IVRS ACPI table. For
1733 example, to map HPET-ID decimal 0 to
1734 PCI device 00:14.0 write the parameter as:
1735 ivrs_hpet[0]=00:14.0
1736
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001737 ivrs_acpihid [HW,X86_64]
1738 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1739 mapping provided in the IVRS ACPI table. For
1740 example, to map UART-HID:UID AMD0020:0 to
1741 PCI device 00:14.5 write the parameter as:
1742 ivrs_acpihid[00:14.5]=AMD0020:0
1743
Linus Torvalds1da177e2005-04-16 15:20:36 -07001744 js= [HW,JOY] Analog joystick
1745 See Documentation/input/joystick.txt.
1746
Kees Cook65fe9352016-06-13 15:10:02 -07001747 nokaslr [KNL]
1748 When CONFIG_RANDOMIZE_BASE is set, this disables
1749 kernel and module base offset ASLR (Address Space
1750 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001751
Mark Rutlandb0845ce2017-03-31 15:12:04 -07001752 kasan_multi_shot
1753 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1754 report on every invalid memory access. Without this
1755 parameter KASAN will print report only for the first
1756 invalid access.
1757
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001758 keepinitrd [HW,ARM]
1759
Taku Izumi342332e2016-03-15 14:55:22 -07001760 kernelcore= [KNL,X86,IA-64,PPC]
1761 Format: nn[KMGTPE] | "mirror"
1762 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001763 specifies the amount of memory usable by the kernel
1764 for non-movable allocations. The requested amount is
1765 spread evenly throughout all nodes in the system. The
1766 remaining memory in each node is used for Movable
1767 pages. In the event, a node is too small to have both
1768 kernelcore and Movable pages, kernelcore pages will
1769 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001770 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001771 allocation of pages that may be reclaimed or moved
1772 by the page migration subsystem. This means that
1773 HugeTLB pages may not be allocated from this zone.
1774 Note that allocations like PTEs-from-HighMem still
1775 use the HighMem zone if it exists, and the Normal
1776 zone if it does not.
1777
Taku Izumi342332e2016-03-15 14:55:22 -07001778 Instead of specifying the amount of memory (nn[KMGTPE]),
1779 you can specify "mirror" option. In case "mirror"
1780 option is specified, mirrored (reliable) memory is used
1781 for non-movable allocations and remaining memory is used
1782 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1783 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1784 time.
1785
Jason Wessel4fe1da42010-05-20 21:04:31 -05001786 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1787 Format: <Controller#>[,poll interval]
1788 The controller # is the number of the ehci usb debug
1789 port as it is probed via PCI. The poll interval is
1790 optional and is the number seconds in between
1791 each poll cycle to the debug port in case you need
1792 the functionality for interrupting the kernel with
1793 gdb or control-c on the dbgp connection. When
1794 not using this parameter you use sysrq-g to break into
1795 the kernel debugger.
1796
Jason Wessel84c08fd2010-05-20 21:04:24 -05001797 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001798 Requires a tty driver that supports console polling,
1799 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001800 Serial only format: <serial_device>[,baud]
1801 keyboard only format: kbd
1802 keyboard and serial format: kbd,<serial_device>[,baud]
1803 Optional Kernel mode setting:
1804 kms, kbd format: kms,kbd
1805 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001806
Jason Wessel84c08fd2010-05-20 21:04:24 -05001807 kgdbwait [KGDB] Stop kernel execution and enter the
1808 kernel debugger at the earliest opportunity.
1809
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001810 kmac= [MIPS] korina ethernet MAC address.
1811 Configure the RouterBoard 532 series on-chip
1812 Ethernet adapter MAC address.
1813
Catalin Marinas04f70332009-06-11 13:22:39 +01001814 kmemleak= [KNL] Boot-time kmemleak enable/disable
1815 Valid arguments: on, off
1816 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001817 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1818 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001819
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001820 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1821 Valid arguments: 0, 1, 2
1822 kmemcheck=0 (disabled)
1823 kmemcheck=1 (enabled)
1824 kmemcheck=2 (one-shot mode)
1825 Default: 2 (one-shot mode)
1826
Andre Przywarafef07aa2009-07-10 14:20:35 +02001827 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1828 Default is 0 (don't ignore, but inject #GP)
1829
Xiao Guangronga182d872010-09-20 22:17:48 +08001830 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1831 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001832 Default is 0 (off)
1833
Andre Przywarafef07aa2009-07-10 14:20:35 +02001834 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001835 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001836
1837 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1838 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001839 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001840
Andre Przywarafef07aa2009-07-10 14:20:35 +02001841 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1842 (virtualized MMU) support on capable Intel chips.
1843 Default is 1 (enabled)
1844
1845 kvm-intel.emulate_invalid_guest_state=
1846 [KVM,Intel] Enable emulation of invalid guest states
1847 Default is 0 (disabled)
1848
1849 kvm-intel.flexpriority=
1850 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1851 Default is 1 (enabled)
1852
Sasha Levine1a72ae2011-08-09 14:28:35 +03001853 kvm-intel.nested=
1854 [KVM,Intel] Enable VMX nesting (nVMX).
1855 Default is 0 (disabled)
1856
Andre Przywarafef07aa2009-07-10 14:20:35 +02001857 kvm-intel.unrestricted_guest=
1858 [KVM,Intel] Disable unrestricted guest feature
1859 (virtualized real and unpaged mode) on capable
1860 Intel chips. Default is 1 (enabled)
1861
1862 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1863 feature (tagged TLBs) on capable Intel chips.
1864 Default is 1 (enabled)
1865
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 l2cr= [PPC]
1867
Robert Brosea78bfbf2008-03-29 07:20:23 +11001868 l3cr= [PPC]
1869
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001870 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001871 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001872
Suresh Siddha279f1462012-10-22 14:37:58 -07001873 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1874 value for LAPIC timer one-shot implementation. Default
1875 back to the programmable timer unit in the LAPIC.
1876
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301877 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001878 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001879
FD Camifcb71f62008-01-06 19:08:56 +01001880 libata.dma= [LIBATA] DMA control
1881 libata.dma=0 Disable all PATA and SATA DMA
1882 libata.dma=1 PATA and SATA Disk DMA only
1883 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001884 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001885 Combinations also work, so libata.dma=3 enables DMA
1886 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001887
Michael Prokop20308872009-08-06 00:14:10 +02001888 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1889 libata.ignore_hpa=0 keep BIOS limits (default)
1890 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001891
Dave Jones78e70c22007-09-27 11:50:13 -04001892 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1893 when set.
1894 Format: <int>
1895
Tejun Heo33267322008-02-13 09:15:09 +09001896 libata.force= [LIBATA] Force configurations. The format is comma
1897 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001898 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001899 matching port, link or device. Basically, it matches
1900 the ATA ID string printed on console by libata. If
1901 the whole ID part is omitted, the last PORT and DEVICE
1902 values are used. If ID hasn't been specified yet, the
1903 configuration applies to all ports, links and devices.
1904
1905 If only DEVICE is omitted, the parameter applies to
1906 the port and all links and devices behind it. DEVICE
1907 number of 0 either selects the first device or the
1908 first fan-out link behind PMP device. It does not
1909 select the host link. DEVICE number of 15 selects the
1910 host link and device attached to it.
1911
1912 The VAL specifies the configuration to force. As long
1913 as there's no ambiguity shortcut notation is allowed.
1914 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1915 The following configurations can be forced.
1916
1917 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1918 Any ID with matching PORT is used.
1919
1920 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1921
1922 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1923 udma[/][16,25,33,44,66,100,133] notation is also
1924 allowed.
1925
1926 * [no]ncq: Turn on or off NCQ.
1927
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001928 * [no]ncqtrim: Turn off queued DSM TRIM.
1929
Tejun Heo05944bd2008-08-13 20:19:09 +09001930 * nohrst, nosrst, norst: suppress hard, soft
1931 and both resets.
1932
Dan Williamsca6d43b2012-06-21 23:41:41 -07001933 * rstonce: only attempt one reset during
1934 hot-unplug link recovery
1935
Tejun Heo43c9c592010-05-23 12:59:11 +02001936 * dump_id: dump IDENTIFY data.
1937
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001938 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1939
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001940 * disable: Disable this device.
1941
Tejun Heo33267322008-02-13 09:15:09 +09001942 If there are multiple matching configurations changing
1943 the same attribute, the last one is used.
1944
Yinghai Lu95f72d12010-07-12 14:36:09 +10001945 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001946
Linus Torvalds1da177e2005-04-16 15:20:36 -07001947 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001948 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001950 lockd.nlm_grace_period=P [NFS] Assign grace period.
1951 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001953 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1954 Format: <integer>
1955
1956 lockd.nlm_timeout=T [NFS] Assign timeout value.
1957 Format: <integer>
1958
1959 lockd.nlm_udpport=M [NFS] Assign UDP port.
1960 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001961
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001962 locktorture.nreaders_stress= [KNL]
1963 Set the number of locking read-acquisition kthreads.
1964 Defaults to being automatically set based on the
1965 number of online CPUs.
1966
1967 locktorture.nwriters_stress= [KNL]
1968 Set the number of locking write-acquisition kthreads.
1969
1970 locktorture.onoff_holdoff= [KNL]
1971 Set time (s) after boot for CPU-hotplug testing.
1972
1973 locktorture.onoff_interval= [KNL]
1974 Set time (s) between CPU-hotplug operations, or
1975 zero to disable CPU-hotplug testing.
1976
1977 locktorture.shuffle_interval= [KNL]
1978 Set task-shuffle interval (jiffies). Shuffling
1979 tasks allows some CPUs to go into dyntick-idle
1980 mode during the locktorture test.
1981
1982 locktorture.shutdown_secs= [KNL]
1983 Set time (s) after boot system shutdown. This
1984 is useful for hands-off automated testing.
1985
1986 locktorture.stat_interval= [KNL]
1987 Time (s) between statistics printk()s.
1988
1989 locktorture.stutter= [KNL]
1990 Time (s) to stutter testing, for example,
1991 specifying five seconds causes the test to run for
1992 five seconds, wait for five seconds, and so on.
1993 This tests the locking primitive's ability to
1994 transition abruptly to and from idle.
1995
1996 locktorture.torture_runnable= [BOOT]
1997 Start locktorture running at boot time.
1998
1999 locktorture.torture_type= [KNL]
2000 Specify the locking implementation to test.
2001
2002 locktorture.verbose= [KNL]
2003 Enable additional printk() statements.
2004
Linus Torvalds1da177e2005-04-16 15:20:36 -07002005 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2006 Format: <irq>
2007
2008 loglevel= All Kernel Messages with a loglevel smaller than the
2009 console loglevel will be printed to the console. It can
2010 also be changed with klogd or other programs. The
2011 loglevels are defined as follows:
2012
2013 0 (KERN_EMERG) system is unusable
2014 1 (KERN_ALERT) action must be taken immediately
2015 2 (KERN_CRIT) critical conditions
2016 3 (KERN_ERR) error conditions
2017 4 (KERN_WARNING) warning conditions
2018 5 (KERN_NOTICE) normal but significant condition
2019 6 (KERN_INFO) informational
2020 7 (KERN_DEBUG) debug-level messages
2021
Randy Dunlapc756d082011-02-20 20:08:35 -08002022 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002023 in bytes. n must be a power of two and greater
2024 than the minimal size. The minimal size is defined
2025 by LOG_BUF_SHIFT kernel config parameter. There is
2026 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2027 that allows to increase the default size depending on
2028 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029
Randy Dunlapaccaa242007-10-16 01:29:37 -07002030 logo.nologo [FB] Disables display of the built-in Linux logo.
2031 This may be used to provide more screen space for
2032 kernel log messages and is useful when debugging
2033 kernel boot problems.
2034
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 lp=0 [LP] Specify parallel ports to use, e.g,
2036 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2037 lp=reset first parallel port). 'lp=0' disables the
2038 lp=auto printer driver. 'lp=reset' (which can be
2039 specified in addition to the ports) causes
2040 attached printers to be reset. Using
2041 lp=port1,port2,... specifies the parallel ports
2042 to associate lp devices with, starting with
2043 lp0. A port specification may be 'none' to skip
2044 that lp device, or a parport name such as
2045 'parport0'. Specifying 'lp=auto' instead of a
2046 port specification list means that device IDs
2047 from each port should be examined, to see if
2048 an IEEE 1284-compliant printer is attached; if
2049 so, the driver will manage that printer.
2050 See also header of drivers/char/lp.c.
2051
2052 lpj=n [KNL]
2053 Sets loops_per_jiffy to given constant, thus avoiding
2054 time-consuming boot-time autodetection (up to 250 ms per
2055 CPU). 0 enables autodetection (default). To determine
2056 the correct value for your kernel, boot with normal
2057 autodetection and see what value is printed. Note that
2058 on SMP systems the preset will be applied to all CPUs,
2059 which is likely to cause problems if your CPUs need
2060 significantly divergent settings. An incorrect value
2061 will cause delays in the kernel to be wrong, leading to
2062 unpredictable I/O errors and other breakage. Although
2063 unlikely, in the extreme case this might damage your
2064 hardware.
2065
2066 ltpc= [NET]
2067 Format: <io>,<irq>,<dma>
2068
Randy Dunlap16290242011-08-13 12:34:52 -07002069 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002070 (machvec) in a generic kernel.
2071 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072
Wu Zhangjin3209e702009-07-02 23:27:12 +08002073 machtype= [Loongson] Share the same kernel image file between different
2074 yeeloong laptop.
2075 Example: machtype=lemote-yeeloong-2f-7inch
2076
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002077 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2078 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002079
2080 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002081 will bring up during bootup. maxcpus=n : n >= 0 limits
2082 the kernel to bring up 'n' processors. Surely after
2083 bootup you can bring up the other plugged cpu by executing
2084 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2085 only takes effect during system bootup.
2086 While n=0 is a special case, it is equivalent to "nosmp",
2087 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088
Kay Sieversd134b002011-07-31 22:08:04 +02002089 max_loop= [LOOP] The number of loop block devices that get
2090 (loop.max_loop) unconditionally pre-created at init time. The default
2091 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2092 of statically allocating a predefined number, loop
2093 devices can be requested on-demand with the
2094 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002095
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002096 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097
Uwe Hermann71cced62008-10-20 09:32:21 -07002098 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002099
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100 md= [HW] RAID subsystems devices and level
Jani Nikulae52347b2016-11-03 12:10:10 +02002101 See Documentation/admin-guide/md.rst.
Randy Dunlapa9913042005-10-23 12:57:11 -07002102
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103 mdacon= [MDA]
2104 Format: <first>,<last>
2105 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002106
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2108 Amount of memory to be used when the kernel is not able
2109 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002110 [X86] Work as limiting max address. Use together
2111 with memmap= to avoid physical address space collisions.
2112 Without memmap= PCI devices could be placed at addresses
2113 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002115 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116 memory.
2117
Paul Mundt6902aa82008-09-21 17:14:42 +09002118 memchunk=nn[KMG]
2119 [KNL,SH] Allow user to override the default size for
2120 per-device physically contiguous DMA buffers.
2121
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002122 memhp_default_state=online/offline
2123 [KNL] Set the initial state for the memory hotplug
2124 onlining policy. If not specified, the default value is
2125 set according to the
2126 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2127 option.
2128 See Documentation/memory-hotplug.txt.
2129
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302130 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131 E820 memory map, as specified by the user.
2132 Such memmap=exactmap lines can be constructed based on
2133 BIOS output or other requirements. See the memmap=nn@ss
2134 option description.
2135
2136 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002137 [KNL] Force usage of a specific region of memory.
2138 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002139
2140 memmap=nn[KMG]#ss[KMG]
2141 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002142 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143
2144 memmap=nn[KMG]$ss[KMG]
2145 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002146 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002147 Example: Exclude memory from 0x18690000-0x1869ffff
2148 memmap=64K$0x18690000
2149 or
2150 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002152 memmap=nn[KMG]!ss[KMG]
2153 [KNL,X86] Mark specific memory as protected.
2154 Region of memory to be used, from ss to ss+nn.
2155 The memory region may be marked as e820 type 12 (0xc)
2156 and is NVDIMM or ADR memory.
2157
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002158 memory_corruption_check=0/1 [X86]
2159 Some BIOSes seem to corrupt the first 64k of
2160 memory when doing things like suspend/resume.
2161 Setting this option will scan the memory
2162 looking for corruption. Enabling this will
2163 both detect corruption and prevent the kernel
2164 from using the memory being corrupted.
2165 However, its intended as a diagnostic tool; if
2166 repeatable BIOS-originated corruption always
2167 affects the same memory, you can use memmap=
2168 to prevent the kernel from using that memory.
2169
2170 memory_corruption_check_size=size [X86]
2171 By default it checks for corruption in the low
2172 64k, making this memory unavailable for normal
2173 use. Use this parameter to scan for
2174 corruption in more or less memory.
2175
2176 memory_corruption_check_period=seconds [X86]
2177 By default it checks for corruption every 60
2178 seconds. Use this parameter to check at some
2179 other rate. 0 disables periodic checking.
2180
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002181 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002182 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002183 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002184 Specifies the number of memtest passes to be
2185 performed. Each pass selects another test
2186 pattern from a given set of patterns. Memtest
2187 fills the memory with this pattern, validates
2188 memory contents and reserves bad memory
2189 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002190
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002191 mem_sleep_default= [SUSPEND] Default system suspend mode:
2192 s2idle - Suspend-To-Idle
2193 shallow - Power-On Suspend or equivalent (if supported)
2194 deep - Suspend-To-RAM or equivalent (if supported)
2195 See Documentation/power/states.txt.
2196
Linus Torvalds1da177e2005-04-16 15:20:36 -07002197 meye.*= [HW] Set MotionEye Camera parameters
2198 See Documentation/video4linux/meye.txt.
2199
Andres Salomon8f368812007-10-12 23:04:06 +02002200 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2201 Multi-Function General Purpose Timers on AMD Geode
2202 platforms.
2203
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002204 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2205 the BIOS has incorrectly applied a workaround. TinyBIOS
2206 version 0.98 is known to be affected, 0.99 fixes the
2207 problem by letting the user disable the workaround.
2208
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 mga= [HW,DRM]
2210
Randy Dunlap1c207f952008-11-19 15:36:16 -08002211 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2212 physical address is ignored.
2213
Michel Pollet39f45d72009-05-20 11:10:31 +01002214 mini2440= [ARM,HW,KNL]
2215 Format:[0..2][b][c][t]
2216 Default: "0tb"
2217 MINI2440 configuration specification:
2218 0 - The attached screen is the 3.5" TFT
2219 1 - The attached screen is the 7" TFT
2220 2 - The VGA Shield is attached (1024x768)
2221 Leaving out the screen size parameter will not load
2222 the TFT driver, and the framebuffer will be left
2223 unconfigured.
2224 b - Enable backlight. The TFT backlight pin will be
2225 linked to the kernel VESA blanking code and a GPIO
2226 LED. This parameter is not necessary when using the
2227 VGA shield.
2228 c - Enable the s3c camera interface.
2229 t - Reserved for enabling touchscreen support. The
2230 touchscreen support is not enabled in the mainstream
2231 kernel as of 2.6.30, a preliminary port can be found
2232 in the "bleeding edge" mini2440 support kernel at
2233 http://repo.or.cz/w/linux-2.6/mini2440.git
2234
Mel Gorman6b74ab92008-07-23 21:26:49 -07002235 mminit_loglevel=
2236 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2237 parameter allows control of the logging verbosity for
2238 the additional memory initialisation checks. A value
2239 of 0 disables mminit logging and a level of 4 will
2240 log everything. Information is printed at KERN_DEBUG
2241 so loglevel=8 may also need to be specified.
2242
Rusty Russell106a4ee2012-09-26 10:09:40 +01002243 module.sig_enforce
2244 [KNL] When CONFIG_MODULE_SIG is set, this means that
2245 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002246 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002247 is always true, so this option does nothing.
2248
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302249 module_blacklist= [KNL] Do not load a comma-separated list of
2250 modules. Useful for debugging problem modules.
2251
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252 mousedev.tap_time=
2253 [MOUSE] Maximum time between finger touching and
2254 leaving touchpad surface for touch to be considered
2255 a tap and be reported as a left button click (for
2256 touchpads working in absolute mode only).
2257 Format: <msecs>
2258 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2259 reporting absolute coordinates, such as tablets
2260 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2261 reporting absolute coordinates, such as tablets
2262
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302263 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002264 is similar to kernelcore except it specifies the
2265 amount of memory used for migratable allocations.
2266 If both kernelcore and movablecore is specified,
2267 then kernelcore will be at *least* the specified
2268 value but may be more. If movablecore on its own
2269 is specified, the administrator must be careful
2270 that the amount of memory usable for all allocations
2271 is not too small.
2272
Reza Arbab39fa104d2016-12-12 16:42:55 -08002273 movable_node [KNL] Boot-time switch to enable the effects
Tang Chenc5320922013-11-12 15:08:10 -08002274 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2275
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276 MTD_Partition= [MTD]
2277 Format: <name>,<region-number>,<size>,<offset>
2278
Randy Dunlapa9913042005-10-23 12:57:11 -07002279 MTD_Region= [MTD] Format:
2280 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002281
2282 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002283 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002285 multitce=off [PPC] This parameter disables the use of the pSeries
2286 firmware feature for updating multiple TCE entries
2287 at a time.
2288
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002289 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2290
2291 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2292
2293 boundary - index of last SLC block on Flex-OneNAND.
2294 The remaining blocks are configured as MLC blocks.
2295 lock - Configure if Flex-OneNAND boundary should be locked.
2296 Once locked, the boundary cannot be changed.
2297 1 indicates lock status, 0 indicates unlock status.
2298
Ben Dooks9db829f2008-07-03 11:24:29 +01002299 mtdset= [ARM]
2300 ARM/S3C2412 JIVE boot control
2301
2302 See arch/arm/mach-s3c2412/mach-jive.c
2303
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002305 [HW] Make the MicroTouch USB driver use raw coordinates
2306 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002307
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002308 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002309 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002310 that could hold holes aka. UC entries.
2311
2312 mtrr_gran_size=nn[KMG] [X86]
2313 Used for mtrr cleanup. It is granularity of mtrr block.
2314 Default is 1.
2315 Large value could prevent small alignment from
2316 using up MTRRs.
2317
2318 mtrr_spare_reg_nr=n [X86]
2319 Format: <integer>
2320 Range: 0,7 : spare reg number
2321 Default : 1
2322 Used for mtrr cleanup. It is spare mtrr entries number.
2323 Set to 2 or more if your graphical card needs more.
2324
Linus Torvalds1da177e2005-04-16 15:20:36 -07002325 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2326
Linus Torvalds1da177e2005-04-16 15:20:36 -07002327 netdev= [NET] Network devices parameters
2328 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2329 Note that mem_start is often overloaded to mean
2330 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002331 This usage is only documented in each driver source
2332 file if at all.
2333
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002334 nf_conntrack.acct=
2335 [NETFILTER] Enable connection tracking flow accounting
2336 0 to disable accounting
2337 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002338 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002339
Chuck Lever306a0752010-09-17 10:54:37 -04002340 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002341 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002342
2343 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002344 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002345
Chuck Lever306a0752010-09-17 10:54:37 -04002346 nfsrootdebug [NFS] enable nfsroot debugging messages.
2347 See Documentation/filesystems/nfs/nfsroot.txt.
2348
Trond Myklebust5405fc42016-08-29 20:03:52 -04002349 nfs.callback_nr_threads=
2350 [NFSv4] set the total number of threads that the
2351 NFS client will assign to service NFSv4 callback
2352 requests.
2353
Trond Myklebusta72b4422006-01-03 09:55:41 +01002354 nfs.callback_tcpport=
2355 [NFS] set the TCP port on which the NFSv4 callback
2356 channel should listen.
2357
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002358 nfs.cache_getent=
2359 [NFS] sets the pathname to the program which is used
2360 to update the NFS client cache entries.
2361
2362 nfs.cache_getent_timeout=
2363 [NFS] sets the timeout after which an attempt to
2364 update a cache entry is deemed to have failed.
2365
Trond Myklebust58df0952006-01-03 09:55:57 +01002366 nfs.idmap_cache_timeout=
2367 [NFS] set the maximum lifetime for idmapper cache
2368 entries.
2369
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002370 nfs.enable_ino64=
2371 [NFS] enable 64-bit inode numbers.
2372 If zero, the NFS client will fake up a 32-bit inode
2373 number for the readdir() and stat() syscalls instead
2374 of returning the full 64-bit number.
2375 The default is to return 64-bit inode numbers.
2376
Trond Myklebust5405fc42016-08-29 20:03:52 -04002377 nfs.max_session_cb_slots=
2378 [NFSv4.1] Sets the maximum number of session
2379 slots the client will assign to the callback
2380 channel. This determines the maximum number of
2381 callbacks the client will process in parallel for
2382 a particular server.
2383
Trond Myklebustef159e92012-02-06 19:50:40 -05002384 nfs.max_session_slots=
2385 [NFSv4.1] Sets the maximum number of session slots
2386 the client will attempt to negotiate with the server.
2387 This limits the number of simultaneous RPC requests
2388 that the client can send to the NFSv4.1 server.
2389 Note that there is little point in setting this
2390 value higher than the max_tcp_slot_table_limit.
2391
Trond Myklebustb064eca22011-02-22 15:44:32 -08002392 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002393 [NFSv4] When set to the default of '1', this option
2394 ensures that both the RPC level authentication
2395 scheme and the NFS level operations agree to use
2396 numeric uids/gids if the mount is using the
2397 'sec=sys' security flavour. In effect it is
2398 disabling idmapping, which can make migration from
2399 legacy NFSv2/v3 systems to NFSv4 easier.
2400 Servers that do not support this mode of operation
2401 will be autodetected by the client, and it will fall
2402 back to using the idmapper.
2403 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002404 nfs.nfs4_unique_id=
2405 [NFS4] Specify an additional fixed unique ident-
2406 ification string that NFSv4 clients can insert into
2407 their nfs_client_id4 string. This is typically a
2408 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002409
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002410 nfs.send_implementation_id =
2411 [NFSv4.1] Send client implementation identification
2412 information in exchange_id requests.
2413 If zero, no implementation identification information
2414 will be sent.
2415 The default is to send the implementation identification
2416 information.
Jani Nikulae52347b2016-11-03 12:10:10 +02002417
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002418 nfs.recover_lost_locks =
2419 [NFSv4] Attempt to recover locks that were lost due
2420 to a lease timeout on the server. Please note that
2421 doing this risks data corruption, since there are
2422 no guarantees that the file will remain unchanged
2423 after the locks are lost.
2424 If you want to enable the kernel legacy behaviour of
2425 attempting to recover these locks, then set this
2426 parameter to '1'.
2427 The default parameter value of '0' causes the kernel
2428 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002429
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002430 nfs4.layoutstats_timer =
2431 [NFSv4.2] Change the rate at which the kernel sends
2432 layoutstats to the pNFS metadata server.
2433
2434 Setting this to value to 0 causes the kernel to use
2435 whatever value is the default set by the layout
2436 driver. A non-zero value sets the minimum interval
2437 in seconds between layoutstats transmissions.
2438
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002439 nfsd.nfs4_disable_idmapping=
2440 [NFSv4] When set to the default of '1', the NFSv4
2441 server will return only numeric uids and gids to
2442 clients using auth_sys, and will accept numeric uids
2443 and gids from such clients. This is intended to ease
2444 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002445
Hans-Christian Noren Egtvedtc0c74ac2017-02-26 13:17:39 +01002446 nmi_debug= [KNL,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002447 when a NMI is triggered.
2448 Format: [state][,regs][,debounce][,die]
2449
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302450 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002451 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002452 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002453 0 - turn hardlockup detector in nmi_watchdog off
2454 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002455 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002456 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002457 default). To disable both hard and soft lockup detectors,
2458 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002459 This is useful when you use a panic=... timeout and
2460 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002461
Anton Vorontsovbff38772009-07-08 11:10:56 -07002462 netpoll.carrier_timeout=
2463 [NET] Specifies amount of time (in seconds) that
2464 netpoll should wait for a carrier. By default netpoll
2465 waits 4 seconds.
2466
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002467 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002468 emulation library even if a 387 maths coprocessor
2469 is present.
2470
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002471 no_console_suspend
2472 [HW] Never suspend the console
2473 Disable suspending of consoles during suspend and
2474 hibernate operations. Once disabled, debugging
2475 messages can reach various consoles while the rest
2476 of the system is being put to sleep (ie, while
2477 debugging driver suspend/resume hooks). This may
2478 not work reliably with all consoles, but is known
2479 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002480 To facilitate more flexible debugging, we also add
2481 console_suspend, a printk module parameter to control
2482 it. Users could use console_suspend (usually
2483 /sys/module/printk/parameters/console_suspend) to
2484 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002485
Christoph Lameterc1aee212007-05-31 00:40:47 -07002486 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2487 caches in the slab allocator. Saves per-node memory,
2488 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002489
Randy Dunlapa9913042005-10-23 12:57:11 -07002490 noalign [KNL,ARM]
2491
Linus Torvalds1da177e2005-04-16 15:20:36 -07002492 noapic [SMP,APIC] Tells the kernel to not make use of any
2493 IOAPICs that may be present in the system.
2494
Mike Galbraith5091faa2010-11-30 14:18:03 +01002495 noautogroup Disable scheduler automatic task group creation.
2496
Linus Torvalds1da177e2005-04-16 15:20:36 -07002497 nobats [PPC] Do not use BATs for mapping kernel lowmem
2498 on "Classic" PPC cores.
2499
2500 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002501
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002502 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2503
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002504 nodelayacct [KNL] Disable per-task delay accounting
2505
Paul Mundt6902aa82008-09-21 17:14:42 +09002506 nodsp [SH] Disable hardware DSP at boot time.
2507
Dave Youngb2e0a542014-08-14 17:15:26 +08002508 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002509
Linus Torvalds1da177e2005-04-16 15:20:36 -07002510 noexec [IA-64]
2511
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302512 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002513 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002514 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002515 noexec=off: disable non-executable mappings
2516
H. Peter Anvin52b61792012-09-21 12:43:13 -07002517 nosmap [X86]
2518 Disable SMAP (Supervisor Mode Access Prevention)
2519 even if it is supported by processor.
2520
Fenghua Yude5397a2011-05-11 16:51:05 -07002521 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002522 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002523 even if it is supported by processor.
2524
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002525 noexec32 [X86-64]
2526 This affects only 32-bit executables.
2527 noexec32=on: enable non-executable mappings (default)
2528 read doesn't imply executable mappings
2529 noexec32=off: disable non-executable mappings
2530 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002531
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002532 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002533
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002534 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002535 register save and restore. The kernel will only save
2536 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002538 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2539
Sascha Silbe52c48c52016-04-05 12:53:38 +02002540 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2541 Equivalent to smt=1.
2542
Suresh Siddha0c752a92009-05-22 12:17:45 -07002543 noxsave [BUGS=X86] Disables x86 extended register state save
2544 and restore using xsave. The kernel will fallback to
2545 enabling legacy floating-point and sse state.
2546
Fenghua Yub6f42a42014-05-29 11:12:31 -07002547 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2548 register states. The kernel will fall back to use
2549 xsave to save the states. By using this parameter,
2550 performance of saving the states is degraded because
2551 xsave doesn't support modified optimization while
2552 xsaveopt supports it on xsaveopt enabled systems.
2553
2554 noxsaves [X86] Disables xsaves and xrstors used in saving and
2555 restoring x86 extended register state in compacted
2556 form of xsave area. The kernel will fall back to use
2557 xsaveopt and xrstor to save and restore the states
2558 in standard form of xsave area. By using this
2559 parameter, xsave area per process might occupy more
2560 memory on xsaves enabled systems.
2561
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002562 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2563 wfi(ARM) instruction doesn't work correctly and not to
2564 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002565
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002566 no_file_caps Tells the kernel not to honor file capabilities. The
2567 only way then for a file to be executed with privilege
2568 is to be setuid root or executed by root.
2569
Linus Torvalds1da177e2005-04-16 15:20:36 -07002570 nohalt [IA-64] Tells the kernel not to use the power saving
2571 function PAL_HALT_LIGHT when idle. This increases
2572 power-consumption. On the positive side, it reduces
2573 interrupt wake-up latency, which may improve performance
2574 in certain environments such as networked servers or
2575 real-time systems.
2576
Kees Cooka6e15a32014-06-13 13:30:35 -07002577 nohibernate [HIBERNATION] Disable hibernation and resume.
2578
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002579 nohz= [KNL] Boottime enable/disable dynamic ticks
2580 Valid arguments: on, off
2581 Default: on
2582
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002583 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002584 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002585 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002586 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002587 whenever possible. The boot CPU will be forced outside
2588 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002589 The CPUs in this range must also be included in the
2590 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002591
Paul Mundteeee7852009-04-02 12:31:16 +09002592 noiotrap [SH] Disables trapped I/O port accesses.
2593
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002594 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 disable unhandled interrupt sources.
2596
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302597 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002598 broken timer IRQ sources.
2599
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 noisapnp [ISAPNP] Disables ISA PnP code.
2601
2602 noinitrd [RAM] Tells the kernel not to load any configured
2603 initial RAM disk.
2604
Weidong Han03ea8152009-04-17 16:42:15 +08002605 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2606 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002607 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002608
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609 nointroute [IA-64]
2610
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002611 noinvpcid [X86] Disable the INVPCID cpu feature.
2612
Randy Dunlap16290242011-08-13 12:34:52 -07002613 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002614
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002615 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2616
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002617 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2618 fault handling.
2619
Alexey Makhalov80e9a4f2016-10-28 00:54:32 -07002620 no-vmw-sched-clock
2621 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2622 clock and use the default one.
2623
Glauber Costad910f5c2011-07-11 15:28:19 -04002624 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2625 steal time is computed, but won't influence scheduler
2626 behaviour
2627
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002628 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002630 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002631
Linus Torvalds1da177e2005-04-16 15:20:36 -07002632 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002633 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634
Horms312f1f02006-02-22 09:57:55 +09002635 nomca [IA-64] Disable machine check abort handling
2636
Masanari Iida13696e02015-05-16 02:16:43 +09002637 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002638
Andres Salomon83d73842007-10-12 23:04:06 +02002639 nomfgpt [X86-32] Disable Multi-Function General Purpose
2640 Timer usage (for AMD Geode machines).
2641
Don Zickusbda62632011-10-13 15:14:27 -04002642 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2643 shutdown the other cpus. Instead use the REBOOT_VECTOR
2644 irq.
2645
Dave Young02608be2012-02-01 10:33:14 +08002646 nomodule Disable module load
2647
Jiri Kosina016ddd92010-01-18 17:05:40 +01002648 nopat [X86] Disable PAT (page attribute table extension of
2649 pagetables) support.
2650
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002651 norandmaps Don't use address space randomization. Equivalent to
2652 echo 0 > /proc/sys/kernel/randomize_va_space
2653
Jiri Kosinabbff2162010-08-11 18:34:09 +02002654 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002655
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002656 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002657 with UP alternatives
2658
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002659 nordrand [X86] Disable kernel use of the RDRAND and
2660 RDSEED instructions even if they are supported
2661 by the processor. RDRAND and RDSEED are still
2662 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002663
Randy Dunlapa9913042005-10-23 12:57:11 -07002664 noresume [SWSUSP] Disables resume and restores original swap
2665 space.
2666
Linus Torvalds1da177e2005-04-16 15:20:36 -07002667 no-scroll [VGA] Disables scrollback.
2668 This is required for the Braillex ib80-piezo Braille
2669 reader made by F.H. Papenmeier (Germany).
2670
2671 nosbagart [IA-64]
2672
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002673 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002674
Len Brown61ec7562007-08-16 03:34:22 -04002675 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2676 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002677
Dave Jones97842212007-07-15 23:41:05 -07002678 nosoftlockup [KNL] Disable the soft-lockup detector.
2679
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680 nosync [HW,M68K] Disables sync negotiation for all devices.
2681
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002682 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002683
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002684 nowatchdog [KNL] Disable both lockup detectors, i.e.
2685 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002686
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002688
Weidong Han2b2fd872009-04-17 16:42:12 +08002689 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2690
Fenghua Yuf78cff42012-11-13 11:32:38 -08002691 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2692 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2693 Some features depend on CPU0. Known dependencies are:
2694 1. Resume from suspend/hibernate depends on CPU0.
2695 Suspend/hibernate will fail if CPU0 is offline and you
2696 need to online CPU0 before suspend/hibernate.
2697 2. PIC interrupts also depend on CPU0. CPU0 can't be
2698 removed if a PIC interrupt is detected.
2699 It's said poweroff/reboot may depend on CPU0 on some
2700 machines although I haven't seen such issues so far
2701 after CPU0 is offline on a few tested machines.
2702 If the dependencies are under your control, you can
2703 turn on cpu0_hotplug.
2704
Randy Dunlap16290242011-08-13 12:34:52 -07002705 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002706 purges which is reported from either PAL_VM_SUMMARY or
2707 SAL PALO.
2708
Yinghai Lu2b633e32010-02-10 01:20:37 -08002709 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2710 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002711 support 'n' processors. It could be larger than the
2712 number of already plugged CPU during bootup, later in
2713 runtime you can physically add extra cpu until it reaches
2714 n. So during boot up some boot time memory for per-cpu
2715 variables need be pre-allocated for later physical cpu
2716 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002717
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002718 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2719
Mel Gorman1a687c22012-11-22 11:16:36 +00002720 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2721 Allowed values are enable and disable
2722
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002723 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2724 one of ['zone', 'node', 'default'] can be specified
2725 This can be set from sysctl after boot.
2726 See Documentation/sysctl/vm.txt for details.
2727
Randy Dunlap7c4be252009-01-06 14:42:44 -08002728 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2729 See Documentation/debugging-via-ohci1394.txt for more
2730 info.
2731
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002732 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2733 Rather than timing out after 20 ms if an EC
2734 command is not properly ACKed, override the length
2735 of the timeout. We have interrupts disabled while
2736 waiting for the ACK, so if this is set too high
2737 interrupts *may* be lost!
2738
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002739 omap_mux= [OMAP] Override bootloader pin multiplexing.
2740 Format: <mux_mode0.mode_name=value>...
2741 For example, to override I2C bus2:
2742 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2743
Linus Torvalds1da177e2005-04-16 15:20:36 -07002744 oprofile.timer= [HW]
2745 Use timer interrupt instead of performance counters
2746
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002747 oprofile.cpu_type= Force an oprofile cpu type
2748 This might be useful if you have an older oprofile
2749 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002750 Format: { arch_perfmon }
2751 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002752 perfmon on Intel CPUs instead of the
2753 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002754 timer: [X86] Force use of architectural NMI
2755 timer mode (see also oprofile.timer
2756 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002757
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002758 oops=panic Always panic on oopses. Default is to just kill the
2759 process, but there is a small probability of
2760 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002761 This will also cause panics on machine check exceptions.
2762 Useful together with panic=30 to trigger a reboot.
2763
Randy Dunlapbcfde332010-06-07 17:10:38 -07002764 OSS [HW,OSS]
2765 See Documentation/sound/oss/oss-parameters.txt
2766
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002767 page_owner= [KNL] Boot-time page_owner enabling option.
2768 Storage of the information about who allocated
2769 each page is disabled in default. With this switch,
2770 we can turn it on.
2771 on: enable the feature
2772
Laura Abbott8823b1d2016-03-15 14:56:27 -07002773 page_poison= [KNL] Boot-time parameter changing the state of
2774 poisoning on the buddy allocator.
2775 off: turn off poisoning
2776 on: turn on poisoning
2777
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002778 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002779 timeout > 0: seconds before rebooting
2780 timeout = 0: wait forever
2781 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002782 Format: <timeout>
2783
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002784 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2785 on a WARN().
2786
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002787 crash_kexec_post_notifiers
2788 Run kdump after running panic-notifiers and dumping
2789 kmsg. This only for the users who doubt kdump always
2790 succeeds in any situation.
2791 Note that this also increases risks of kdump failure,
2792 because some panic notifiers can make the crashed
2793 kernel more unstable.
2794
Linus Torvalds1da177e2005-04-16 15:20:36 -07002795 parkbd.port= [HW] Parallel port number the keyboard adapter is
2796 connected to, default is 0.
2797 Format: <parport#>
2798 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2799 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002800 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801
Randy Dunlapa9913042005-10-23 12:57:11 -07002802 parport= [HW,PPT] Specify parallel ports. 0 disables.
2803 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2804 Use 'auto' to force the driver to use any
2805 IRQ/DMA settings detected (the default is to
2806 ignore detected IRQ/DMA settings because of
2807 possible conflicts). You can specify the base
2808 address, IRQ, and DMA settings; IRQ and DMA
2809 should be numbers, or 'auto' (for using detected
2810 settings on that particular port), or 'nofifo'
2811 (to avoid using a FIFO even if it is detected).
2812 Parallel ports are assigned in the order they
2813 are specified on the command line, starting
2814 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002815
Randy Dunlapa9913042005-10-23 12:57:11 -07002816 parport_init_mode= [HW,PPT]
2817 Configure VIA parallel port to operate in
2818 a specific mode. This is necessary on Pegasos
2819 computer where firmware has no options for setting
2820 up parallel port mode and sets it to spp.
2821 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002822 Format: [spp|ps2|epp|ecp|ecpepp]
2823
Andrew Mortondd287792006-03-23 03:00:57 -08002824 pause_on_oops=
2825 Halt all CPUs after the first oops has been printed for
2826 the specified number of seconds. This is to be used if
2827 your oopses keep scrolling off the screen.
2828
Linus Torvalds1da177e2005-04-16 15:20:36 -07002829 pcbit= [HW,ISDN]
2830
2831 pcd. [PARIDE]
2832 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002833 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002834
Randy Dunlapa9913042005-10-23 12:57:11 -07002835 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002836 earlydump [X86] dump PCI config space before the kernel
2837 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002838 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002839 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002840 the hardware directly. Use this if your machine
2841 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002842 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002843 hardware access methods are allowed. Use this
2844 if you experience crashes upon bootup and you
2845 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002846 conf1 [X86] Force use of PCI Configuration Access
2847 Mechanism 1 (config address in IO port 0xCF8,
2848 data in IO port 0xCFC, both 32-bit).
2849 conf2 [X86] Force use of PCI Configuration Access
2850 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2851 the function, IO port 0xCFA, also 8-bit, sets
2852 bus number. The config space is then accessed
2853 through ports 0xC000-0xCFFF).
2854 See http://wiki.osdev.org/PCI for more info
2855 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002856 noaer [PCIE] If the PCIEAER kernel config parameter is
2857 enabled, this kernel boot option can be used to
2858 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002859 nodomains [PCI] Disable support for multiple PCI
2860 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302861 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002862 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002863 check_enable_amd_mmconf [X86] check for and enable
2864 properly configured MMIO access to PCI
2865 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002866 nomsi [MSI] If the PCI_MSI kernel config parameter is
2867 enabled, this kernel boot option can be used to
2868 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002869 noioapicquirk [APIC] Disable all boot interrupt quirks.
2870 Safety option to keep boot IRQs enabled. This
2871 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002872 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2873 primary IO-APIC for bridges that cannot disable
2874 boot IRQs. This fixes a source of spurious IRQs
2875 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002876 noioapicreroute [APIC] Disable workaround that uses the
2877 boot IRQ equivalent of an IRQ that connects to
2878 a chipset where boot IRQs cannot be disabled.
2879 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002880 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002881 routing table. These calls are known to be buggy
2882 on several machines and they hang the machine
2883 when used, but on other computers it's the only
2884 way to get the interrupt routing table. Try
2885 this option if the kernel is unable to allocate
2886 IRQs or discover secondary PCI buses on your
2887 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002888 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002889 Use with caution as certain devices share
2890 address decoders between ROMs and other
2891 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002892 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002893 expansion ROMs that do not already have
2894 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002895 nobar [X86] Do not assign address space to the
2896 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002897 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002898 assigned automatically to PCI devices. You can
2899 make the kernel exclude IRQs of your ISA cards
2900 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002901 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002902 of the PIRQ table (normally generated
2903 by the BIOS) if it is outside the
2904 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002905 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002906 useful if the kernel is unable to find your
2907 secondary buses and you want to tell it
2908 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002909 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002910 numbers ourselves, overriding
2911 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002912 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002913 in the BIOS $PIR table. This is needed on
2914 some systems with broken BIOSes, notably
2915 some HP Pavilion N5400 and Omnibook XE3
2916 notebooks. This will have no effect if ACPI
2917 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002918 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002919 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002920 use_crs [X86] Use PCI host bridge window information
2921 from ACPI. On BIOSes from 2008 or later, this
2922 is enabled by default. If you need to use this,
2923 please report a bug.
2924 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2925 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002926 routeirq Do IRQ routing for all PCI devices.
2927 This is normally done in pci_enable_device(),
2928 so this option is a temporary workaround
2929 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002930 skip_isa_align [X86] do not align io start addr, so can
2931 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02002932 noearly [X86] Don't do any early type 1 scanning.
2933 This might help on some broken boards which
2934 machine check when some devices' config space
2935 is read. But various workarounds are disabled
2936 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002937 bfsort Sort PCI devices into breadth-first order.
2938 This sorting is done to get a device
2939 order compatible with older (<= 2.4) kernels.
2940 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002941 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2942 tuning and use the BIOS-configured MPS defaults.
2943 pcie_bus_safe Set every device's MPS to the largest value
2944 supported by all devices below the root complex.
2945 pcie_bus_perf Set device MPS to the largest allowable MPS
2946 based on its parent bus. Also set MRRS (Max
2947 Read Request Size) to the largest supported
2948 value (no larger than the MPS that the device
2949 or bus can support) for best performance.
2950 pcie_bus_peer2peer Set every device's MPS to 128B, which
2951 every device is guaranteed to support. This
2952 configuration allows peer-to-peer DMA between
2953 any pair of devices, possibly at the cost of
2954 reduced performance. This also guarantees
2955 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002956 cbiosize=nn[KMG] The fixed amount of bus space which is
2957 reserved for the CardBus bridge's IO window.
2958 The default value is 256 bytes.
2959 cbmemsize=nn[KMG] The fixed amount of bus space which is
2960 reserved for the CardBus bridge's memory
2961 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002962 resource_alignment=
2963 Format:
2964 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00002965 [<order of align>@]pci:<vendor>:<device>\
2966 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002967 Specifies alignment and device to reassign
2968 aligned memory resources.
2969 If <order of align> is not specified,
2970 PAGE_SIZE is used as alignment.
2971 PCI-PCI bridge can be specified, if resource
2972 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02002973 To specify the alignment for several
2974 instances of a device, the PCI vendor,
2975 device, subvendor, and subdevice may be
2976 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06002977 ecrc= Enable/disable PCIe ECRC (transaction layer
2978 end-to-end CRC checking).
2979 bios: Use BIOS/firmware settings. This is the
2980 the default.
2981 off: Turn ECRC off
2982 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002983 hpiosize=nn[KMG] The fixed amount of bus space which is
2984 reserved for hotplug bridge's IO window.
2985 Default size is 256 bytes.
2986 hpmemsize=nn[KMG] The fixed amount of bus space which is
2987 reserved for hotplug bridge's memory window.
2988 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06002989 hpbussize=nn The minimum amount of additional bus numbers
2990 reserved for buses below a hotplug bridge.
2991 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08002992 realloc= Enable/disable reallocating PCI bridge resources
2993 if allocations done by BIOS are too small to
2994 accommodate resources required by all child
2995 devices.
2996 off: Turn realloc off
2997 on: Turn realloc on
2998 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002999 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003000 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3001 only look for one device below a PCIe downstream
3002 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003003
Chuck Ebberte5665a42008-09-24 20:40:34 -04003004 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3005 Management.
3006 off Disable ASPM.
3007 force Enable ASPM even on devices that claim not to support it.
3008 WARNING: Forcing ASPM on may cause system lockups.
3009
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003010 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3011 nomsi Do not use MSI for PCI Express Native Hotplug (this
3012 makes all PCIe ports use INTx for hotplug services).
3013
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003014 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003015 auto Ask the BIOS whether or not to use native PCIe services
3016 associated with PCIe ports (PME, hot-plug, AER). Use
3017 them only if that is allowed by the BIOS.
3018 native Use native PCIe services associated with PCIe ports
3019 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003020 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3021 ports driver.
3022
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03003023 pcie_port_pm= [PCIE] PCIe port power management handling:
3024 off Disable power management of all PCIe ports
3025 force Forcibly enable power management of all PCIe ports
3026
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003027 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003028 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003029 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003030
Linus Torvalds1da177e2005-04-16 15:20:36 -07003031 pcmv= [HW,PCMCIA] BadgePAD 4
3032
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303033 pd_ignore_unused
3034 [PM]
3035 Keep all power-domains already enabled by bootloader on,
3036 even if no driver has claimed them. This is useful
3037 for debug and development, but should not be
3038 needed on a platform with proper driver support.
3039
Linus Torvalds1da177e2005-04-16 15:20:36 -07003040 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003041 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042
3043 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3044 boot time.
3045 Format: { 0 | 1 }
3046 See arch/parisc/kernel/pdc_chassis.c
3047
Tejun Heof58dc012009-08-14 15:00:50 +09003048 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003049 Currently supported values are "embed" and "page".
3050 Archs may support subset or none of the selections.
3051 See comments in mm/percpu.c for details on each
3052 allocator. This parameter is primarily for debugging
3053 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003054
Linus Torvalds1da177e2005-04-16 15:20:36 -07003055 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003056 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003057
3058 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003059 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003060
3061 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003062 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003063
3064 plip= [PPT,NET] Parallel port network link
3065 Format: { parport<nr> | timid | 0 }
3066 See also Documentation/parport.txt.
3067
Randy Dunlap16290242011-08-13 12:34:52 -07003068 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003069 Override pmtimer IOPort with a hex value.
3070 e.g. pmtmr=0x508
3071
Bjorn Helgaas96242112011-08-11 12:14:05 -06003072 pnp.debug=1 [PNP]
3073 Enable PNP debug messages (depends on the
3074 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3075 via /sys/module/pnp/parameters/debug. We always show
3076 current resource usage; turning this on also shows
3077 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003078
Linus Torvalds1da177e2005-04-16 15:20:36 -07003079 pnpacpi= [ACPI]
3080 { off }
3081
3082 pnpbios= [ISAPNP]
3083 { on | off | curr | res | no-curr | no-res }
3084
3085 pnp_reserve_irq=
3086 [ISAPNP] Exclude IRQs for the autoconfiguration
3087
3088 pnp_reserve_dma=
3089 [ISAPNP] Exclude DMAs for the autoconfiguration
3090
3091 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003092 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003093
3094 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003095 [ISAPNP] Exclude memory regions for the
3096 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003097 Ranges are in pairs (memory base and size).
3098
Randy Dunlap4af94f32009-04-17 18:30:28 -07003099 ports= [IP_VS_FTP] IPVS ftp helper module
3100 Default is 21.
3101 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3102 may be specified.
3103 Format: <port>,<port>....
3104
Balbir Singhc3cbd072016-12-02 00:08:26 +11003105 powersave=off [PPC] This option disables power saving features.
3106 It specifically disables cpuidle and sets the
3107 platform machine description specific power_save
3108 function to NULL. On Idle the CPU just reduces
3109 execution priority.
3110
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003111 ppc_strict_facility_enable
3112 [PPC] This option catches any kernel floating point,
3113 Altivec, VSX and SPE outside of regions specifically
3114 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3115 There is some performance impact when enabling this.
3116
Ingo Molnar45807a12007-07-15 23:40:10 -07003117 print-fatal-signals=
3118 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003119
3120 If enabled, warn about various signal handling
3121 related application anomalies: too many signals,
3122 too many POSIX.1 timers, fatal signals causing a
3123 coredump - etc.
3124
3125 If you hit the warning due to signal overflow,
3126 you might want to try "ulimit -i unlimited".
3127
Ingo Molnar45807a12007-07-15 23:40:10 -07003128 default: off.
3129
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003130 printk.always_kmsg_dump=
3131 Trigger kmsg_dump for cases other than kernel oops or
3132 panics
3133 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3134 default: disabled
3135
Borislav Petkov750afe72016-08-02 14:04:07 -07003136 printk.devkmsg={on,off,ratelimit}
3137 Control writing to /dev/kmsg.
3138 on - unlimited logging to /dev/kmsg from userspace
3139 off - logging to /dev/kmsg disabled
3140 ratelimit - ratelimit the logging
3141 Default: ratelimit
3142
Randy Dunlape84845c2007-07-15 23:40:25 -07003143 printk.time= Show timing data prefixed to each printk message line
3144 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3145
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003146 processor.max_cstate= [HW,ACPI]
3147 Limit processor to maximum C-state
3148 max_cstate=9 overrides any DMI blacklist limit.
3149
3150 processor.nocst [HW,ACPI]
3151 Ignore the _CST method to determine C-states,
3152 instead using the legacy FADT method
3153
Linus Torvalds1da177e2005-04-16 15:20:36 -07003154 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003155 Format: [schedule,]<number>
3156 Param: "schedule" - profile schedule points.
3157 Param: <number> - step/bucket size as a power of 2 for
3158 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003159 Param: "sleep" - profile D-state sleeping (millisecs).
3160 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003161 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003162
Linus Torvalds1da177e2005-04-16 15:20:36 -07003163 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3164 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003165 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003166
Randy Dunlapa9913042005-10-23 12:57:11 -07003167 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3168 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003169 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3170 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003171 psmouse.resetafter= [HW,MOUSE]
3172 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003173 (0 = never).
3174 psmouse.resolution=
3175 [HW,MOUSE] Set desired mouse resolution, in dpi.
3176 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003177 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178 0 = disabled, 1 = enabled (default).
3179
Matthew Garrettdee28e72011-07-21 16:57:55 -04003180 pstore.backend= Specify the name of the pstore backend to use
3181
Linus Torvalds1da177e2005-04-16 15:20:36 -07003182 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003183 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003184
Kay Sieversdc8c8582007-08-15 12:25:38 +02003185 pty.legacy_count=
3186 [KNL] Number of legacy pty's. Overwrites compiled-in
3187 default number.
3188
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003189 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003190
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191 r128= [HW,DRM]
3192
3193 raid= [HW,RAID]
Jani Nikulae52347b2016-11-03 12:10:10 +02003194 See Documentation/admin-guide/md.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003195
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003197 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003198
Borislav Petkov011d8262017-03-27 11:33:02 +02003199 ras=option[,option,...] [KNL] RAS-specific options
3200
3201 cec_disable [X86]
3202 Disable the Correctable Errors Collector,
3203 see CONFIG_RAS_CEC help text.
3204
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003205 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003206 The argument is a cpu list, as described above.
3207
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003208 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3209 the specified list of CPUs to be no-callback CPUs.
3210 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003211 be offloaded to "rcuox/N" kthreads created for
3212 that purpose, where "x" is "b" for RCU-bh, "p"
3213 for RCU-preempt, and "s" for RCU-sched, and "N"
3214 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003215 offloaded CPUs, which can be useful for HPC and
3216 real-time workloads. It can also improve energy
3217 efficiency for asymmetric multiprocessors.
3218
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003219 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003220 Rather than requiring that offloaded CPUs
3221 (specified by rcu_nocbs= above) explicitly
3222 awaken the corresponding "rcuoN" kthreads,
3223 make these kthreads poll for callbacks.
3224 This improves the real-time response for the
3225 offloaded CPUs by relieving them of the need to
3226 wake up the corresponding kthread, but degrades
3227 energy efficiency by requiring that the kthreads
3228 periodically wake up to do the polling.
3229
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003230 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003231 Set maximum number of finished RCU callbacks to
3232 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003233
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003234 rcutree.dump_tree= [KNL]
3235 Dump the structure of the rcu_node combining tree
3236 out at early boot. This is used for diagnostic
3237 purposes, to verify correct tree setup.
3238
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003239 rcutree.gp_cleanup_delay= [KNL]
3240 Set the number of jiffies to delay each step of
3241 RCU grace-period cleanup. This only has effect
3242 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3243
Paul E. McKenney37745d22015-01-22 18:24:08 -08003244 rcutree.gp_init_delay= [KNL]
3245 Set the number of jiffies to delay each step of
3246 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003247 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3248 is set.
3249
3250 rcutree.gp_preinit_delay= [KNL]
3251 Set the number of jiffies to delay each step of
3252 RCU grace-period pre-initialization, that is,
3253 the propagation of recent CPU-hotplug changes up
3254 the rcu_node combining tree. This only has effect
3255 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003256
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003257 rcutree.rcu_fanout_exact= [KNL]
3258 Disable autobalancing of the rcu_node combining
3259 tree. This is used by rcutorture, and might
3260 possibly be useful for architectures having high
3261 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003262
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003263 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003264 Change the number of CPUs assigned to each
3265 leaf rcu_node structure. Useful for very
3266 large systems, which will choose the value 64,
3267 and for NUMA systems with large remote-access
3268 latencies, which will choose a value aligned
3269 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003270
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003271 rcutree.jiffies_till_sched_qs= [KNL]
3272 Set required age in jiffies for a
3273 given grace period before RCU starts
3274 soliciting quiescent-state help from
3275 rcu_note_context_switch().
3276
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003277 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003278 Set delay from grace-period initialization to
3279 first attempt to force quiescent states.
3280 Units are jiffies, minimum value is zero,
3281 and maximum value is HZ.
3282
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003283 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003284 Set delay between subsequent attempts to force
3285 quiescent states. Units are jiffies, minimum
3286 value is one, and maximum value is HZ.
3287
Clark Williams21871d72014-09-12 21:21:09 -05003288 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003289 Set the SCHED_FIFO priority of the RCU per-CPU
3290 kthreads (rcuc/N). This value is also used for
3291 the priority of the RCU boost threads (rcub/N)
3292 and for the RCU grace-period kthreads (rcu_bh,
3293 rcu_preempt, and rcu_sched). If RCU_BOOST is
3294 set, valid values are 1-99 and the default is 1
3295 (the least-favored priority). Otherwise, when
3296 RCU_BOOST is not set, valid values are 0-99 and
3297 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003298
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003299 rcutree.rcu_nocb_leader_stride= [KNL]
3300 Set the number of NOCB kthread groups, which
3301 defaults to the square root of the number of
3302 CPUs. Larger numbers reduces the wakeup overhead
3303 on the per-CPU grace-period kthreads, but increases
3304 that same overhead on each group's leader.
3305
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003306 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003307 Set threshold of queued RCU callbacks beyond which
3308 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003309
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003310 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003311 Set threshold of queued RCU callbacks below which
3312 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003313
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003314 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003315 Set wakeup interval for idle CPUs that have
3316 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003317
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003318 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003319 Set wakeup interval for idle CPUs that have
3320 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3321 Lazy RCU callbacks are those which RCU can
3322 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003323
Paul E. McKenneye3c50df2017-01-06 15:14:11 -08003324 rcutree.rcu_kick_kthreads= [KNL]
3325 Cause the grace-period kthread to get an extra
3326 wake_up() if it sleeps three times longer than
3327 it should at force-quiescent-state time.
3328 This wake_up() will be accompanied by a
3329 WARN_ONCE() splat and an ftrace_dump().
3330
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003331 rcuperf.gp_exp= [KNL]
3332 Measure performance of expedited synchronous
3333 grace-period primitives.
3334
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003335 rcuperf.holdoff= [KNL]
3336 Set test-start holdoff period. The purpose of
3337 this parameter is to delay the start of the
3338 test until boot completes in order to avoid
3339 interference.
3340
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003341 rcuperf.nreaders= [KNL]
3342 Set number of RCU readers. The value -1 selects
3343 N, where N is the number of CPUs. A value
3344 "n" less than -1 selects N-n+1, where N is again
3345 the number of CPUs. For example, -2 selects N
3346 (the number of CPUs), -3 selects N+1, and so on.
3347 A value of "n" less than or equal to -N selects
3348 a single reader.
3349
3350 rcuperf.nwriters= [KNL]
3351 Set number of RCU writers. The values operate
3352 the same as for rcuperf.nreaders.
3353 N, where N is the number of CPUs
3354
3355 rcuperf.perf_runnable= [BOOT]
3356 Start rcuperf running at boot time.
3357
3358 rcuperf.shutdown= [KNL]
3359 Shut the system down after performance tests
3360 complete. This is useful for hands-off automated
3361 testing.
3362
3363 rcuperf.perf_type= [KNL]
3364 Specify the RCU implementation to test.
3365
3366 rcuperf.verbose= [KNL]
3367 Enable additional printk() statements.
3368
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003369 rcutorture.cbflood_inter_holdoff= [KNL]
3370 Set holdoff time (jiffies) between successive
3371 callback-flood tests.
3372
3373 rcutorture.cbflood_intra_holdoff= [KNL]
3374 Set holdoff time (jiffies) between successive
3375 bursts of callbacks within a given callback-flood
3376 test.
3377
3378 rcutorture.cbflood_n_burst= [KNL]
3379 Set the number of bursts making up a given
3380 callback-flood test. Set this to zero to
3381 disable callback-flood testing.
3382
3383 rcutorture.cbflood_n_per_burst= [KNL]
3384 Set the number of callbacks to be registered
3385 in a given burst of a callback-flood test.
3386
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003387 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003388 Set duration of force_quiescent_state bursts
3389 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003390
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003391 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003392 Set holdoff time within force_quiescent_state bursts
3393 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003394
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003395 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003396 Set wait time between force_quiescent_state bursts
3397 in seconds.
3398
3399 rcutorture.gp_cond= [KNL]
3400 Use conditional/asynchronous update-side
3401 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003402
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003403 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003404 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003405
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003406 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003407 Use normal (non-expedited) asynchronous
3408 update-side primitives, if available.
3409
3410 rcutorture.gp_sync= [KNL]
3411 Use normal (non-expedited) synchronous
3412 update-side primitives, if available. If all
3413 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3414 rcutorture.gp_normal=, and rcutorture.gp_sync=
3415 are zero, rcutorture acts as if is interpreted
3416 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003417
3418 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003419 Set callbacks/threads for rcu_barrier() testing.
3420
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003421 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003422 Set number of concurrent RCU writers. These just
3423 stress RCU, they don't participate in the actual
3424 test, hence the "fake".
3425
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003426 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003427 Set number of RCU readers. The value -1 selects
3428 N-1, where N is the number of CPUs. A value
3429 "n" less than -1 selects N-n-2, where N is again
3430 the number of CPUs. For example, -2 selects N
3431 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003432
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003433 rcutorture.object_debug= [KNL]
3434 Enable debug-object double-call_rcu() testing.
3435
3436 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003437 Set time (s) after boot for CPU-hotplug testing.
3438
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003439 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003440 Set time (s) between CPU-hotplug operations, or
3441 zero to disable CPU-hotplug testing.
3442
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003443 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003444 Set task-shuffle interval (s). Shuffling tasks
3445 allows some CPUs to go into dyntick-idle mode
3446 during the rcutorture test.
3447
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003448 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003449 Set time (s) after boot system shutdown. This
3450 is useful for hands-off automated testing.
3451
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003452 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003453 Duration of CPU stall (s) to test RCU CPU stall
3454 warnings, zero to disable.
3455
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003456 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003457 Time to wait (s) after boot before inducing stall.
3458
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003459 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003460 Time (s) between statistics printk()s.
3461
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003462 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003463 Time (s) to stutter testing, for example, specifying
3464 five seconds causes the test to run for five seconds,
3465 wait for five seconds, and so on. This tests RCU's
3466 ability to transition abruptly to and from idle.
3467
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003468 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003469 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3470 "Maybe" means test if the RCU implementation
3471 under test support RCU priority boosting.
3472
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003473 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003474 Duration (s) of each individual boost test.
3475
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003476 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003477 Interval (s) between each boost test.
3478
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003479 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003480 Test RCU's dyntick-idle handling. See also the
3481 rcutorture.shuffle_interval parameter.
3482
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003483 rcutorture.torture_runnable= [BOOT]
3484 Start rcutorture running at boot time.
3485
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003486 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003487 Specify the RCU implementation to test.
3488
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003489 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003490 Enable additional printk() statements.
3491
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003492 rcupdate.rcu_cpu_stall_suppress= [KNL]
3493 Suppress RCU CPU stall warning messages.
3494
3495 rcupdate.rcu_cpu_stall_timeout= [KNL]
3496 Set timeout for RCU CPU stall warning messages.
3497
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003498 rcupdate.rcu_expedited= [KNL]
3499 Use expedited grace-period primitives, for
3500 example, synchronize_rcu_expedited() instead
3501 of synchronize_rcu(). This reduces latency,
3502 but can increase CPU utilization, degrade
3503 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003504 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003505
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003506 rcupdate.rcu_normal= [KNL]
3507 Use only normal grace-period primitives,
3508 for example, synchronize_rcu() instead of
3509 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003510 real-time latency, CPU utilization, and
3511 energy efficiency, but can expose users to
3512 increased grace-period latency. This parameter
3513 overrides rcupdate.rcu_expedited. No effect on
3514 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003515
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003516 rcupdate.rcu_normal_after_boot= [KNL]
3517 Once boot has completed (that is, after
3518 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003519 only normal grace-period primitives. No effect
3520 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003521
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003522 rcupdate.rcu_task_stall_timeout= [KNL]
3523 Set timeout in jiffies for RCU task stall warning
3524 messages. Disable with a value less than or equal
3525 to zero.
3526
Pranith Kumar74860fe2014-09-19 11:34:09 -04003527 rcupdate.rcu_self_test= [KNL]
3528 Run the RCU early boot self tests
3529
3530 rcupdate.rcu_self_test_bh= [KNL]
3531 Run the RCU bh early boot self tests
3532
3533 rcupdate.rcu_self_test_sched= [KNL]
3534 Run the RCU sched early boot self tests
3535
Olof Johanssonffdfc402005-09-06 15:17:19 -07003536 rdinit= [KNL]
3537 Format: <full_path>
3538 Run specified binary instead of /init from the ramdisk,
3539 used for early userspace startup. See initrd.
3540
Robin Holt1b3a5d02013-07-08 16:01:42 -07003541 reboot= [KNL]
3542 Format (x86 or x86_64):
3543 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3544 [[,]s[mp]#### \
3545 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3546 [[,]f[orce]
3547 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3548 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3549 reboot_force is either force or not specified,
3550 reboot_cpu is s[mp]#### with #### being the processor
3551 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003552
Paul Jackson46b6d942008-07-04 10:00:09 -07003553 relax_domain_level=
3554 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003555 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003556
Linus Torvalds1da177e2005-04-16 15:20:36 -07003557 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3558
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003559 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003560 Format: nn[KMG]
3561 Reserves a hole at the top of the kernel virtual
3562 address space.
3563
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003564 reservelow= [X86]
3565 Format: nn[K]
3566 Set the amount of memory to reserve for BIOS at
3567 the bottom of the address space.
3568
Vivek Goyal7e962872006-09-27 01:50:44 -07003569 reset_devices [KNL] Force drivers to reset the underlying device
3570 during initialization.
3571
Randy Dunlapa9913042005-10-23 12:57:11 -07003572 resume= [SWSUSP]
3573 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003574 Format:
3575 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003576
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003577 resume_offset= [SWSUSP]
3578 Specify the offset from the beginning of the partition
3579 given by "resume=" at which the swap header is located,
3580 in <PAGE_SIZE> units (needed only for swap files).
3581 See Documentation/power/swsusp-and-swap-files.txt
3582
Barry Songf126f732011-10-10 23:38:41 +02003583 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3584 read the resume files
3585
Barry Song6f8d7022011-10-06 20:34:46 +02003586 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3587 Useful for devices that are detected asynchronously
3588 (e.g. USB and MMC devices).
3589
Bojan Smojverf996fc92010-09-09 23:06:23 +02003590 hibernate= [HIBERNATION]
3591 noresume Don't check if there's a hibernation image
3592 present during boot.
3593 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003594 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003595 protect_image Turn on image protection during restoration
3596 (that will set all pages holding image data
3597 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003598
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003599 retain_initrd [RAM] Keep initrd memory after extraction
3600
Andrew Clausen0efbb782015-01-09 20:24:55 +00003601 rfkill.default_state=
3602 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3603 etc. communication is blocked by default.
3604 1 Unblocked.
3605
3606 rfkill.master_switch_mode=
3607 0 The "airplane mode" button does nothing.
3608 1 The "airplane mode" button toggles between everything
3609 blocked and the previous configuration.
3610 2 The "airplane mode" button toggles between everything
3611 blocked and everything unblocked.
3612
Linus Torvalds1da177e2005-04-16 15:20:36 -07003613 rhash_entries= [KNL,NET]
3614 Set number of hash buckets for route cache
3615
Grzegorz Andrejczuke16fd002017-01-20 14:22:36 +01003616 ring3mwait=disable
3617 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3618 CPUs.
3619
Linus Torvalds1da177e2005-04-16 15:20:36 -07003620 ro [KNL] Mount root device read-only on boot
3621
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003622 rodata= [KNL]
3623 on Mark read-only kernel memory as read-only (default).
3624 off Leave read-only kernel memory writable for debugging.
3625
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003626 rockchip.usb_uart
3627 Enable the uart passthrough on the designated usb port
3628 on Rockchip SoCs. When active, the signals of the
3629 debug-uart get routed to the D+ and D- pins of the usb
3630 port and the regular usb controller gets disabled.
3631
Linus Torvalds1da177e2005-04-16 15:20:36 -07003632 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003633 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003634
3635 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3636 mount the root filesystem
3637
3638 rootflags= [KNL] Set root filesystem mount option string
3639
3640 rootfstype= [KNL] Set root filesystem type
3641
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003642 rootwait [KNL] Wait (indefinitely) for root device to show up.
3643 Useful for devices that are detected asynchronously
3644 (e.g. USB and MMC devices).
3645
Robert Tivy5c71d612013-03-28 18:41:46 -07003646 rproc_mem=nn[KMG][@address]
3647 [KNL,ARM,CMA] Remoteproc physical memory block.
3648 Memory area to be used by remote processor image,
3649 managed by CMA.
3650
Linus Torvalds1da177e2005-04-16 15:20:36 -07003651 rw [KNL] Mount root device read-write on boot
3652
3653 S [KNL] Run init in single mode
3654
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003655 s390_iommu= [HW,S390]
3656 Set s390 IOTLB flushing mode
3657 strict
3658 With strict flushing every unmap operation will result in
3659 an IOTLB flush. Default is lazy flushing before reuse,
3660 which is faster.
3661
Linus Torvalds1da177e2005-04-16 15:20:36 -07003662 sa1100ir [NET]
3663 See drivers/net/irda/sa1100_ir.c.
3664
Linus Torvalds1da177e2005-04-16 15:20:36 -07003665 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003666
Mike Travisf6630112009-11-17 18:22:15 -06003667 sched_debug [KNL] Enables verbose scheduler debug messages.
3668
Mel Gormancb251762016-02-05 09:08:36 +00003669 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3670 Allowed values are enable and disable. This feature
3671 incurs a small amount of overhead in the scheduler
3672 but is useful for debugging and performance tuning.
3673
Mike Galbraith5307c952012-05-08 12:20:58 +02003674 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3675 xtime_lock contention on larger systems, and/or RCU lock
3676 contention on all systems with CONFIG_MAXSMP set.
3677 Format: { "0" | "1" }
3678 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3679 1 -- enable.
3680 Note: increases power consumption, thus should only be
3681 enabled if running jitter sensitive (HPC/RT) workloads.
3682
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003683 security= [SECURITY] Choose a security module to enable at boot.
3684 If this boot parameter is not specified, only the first
3685 security module asking for security registration will be
3686 loaded. An invalid security module name will be treated
3687 as if no module has been chosen.
3688
3689 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003690 Format: { "0" | "1" }
3691 See security/selinux/Kconfig help text.
3692 0 -- disable.
3693 1 -- enable.
3694 Default value is set via kernel config option.
3695 If enabled at boot time, /selinux/disable can be used
3696 later to disable prior to initial policy load.
3697
John Johansenc1c124e2010-07-29 14:48:09 -07003698 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3699 Format: { "0" | "1" }
3700 See security/apparmor/Kconfig help text
3701 0 -- disable.
3702 1 -- enable.
3703 Default value is set via kernel config option.
3704
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003705 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003706
Linus Torvalds1da177e2005-04-16 15:20:36 -07003707 shapers= [NET]
3708 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003709
Linus Torvalds1da177e2005-04-16 15:20:36 -07003710 simeth= [IA-64]
3711 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003712
Linus Torvalds1da177e2005-04-16 15:20:36 -07003713 slram= [HW,MTD]
3714
Joonsoo Kim423c9292014-10-09 15:26:22 -07003715 slab_nomerge [MM]
3716 Disable merging of slabs with similar size. May be
3717 necessary if there is some reason to distinguish
3718 allocs to different slabs. Debug options disable
3719 merging on their own.
3720 For more information see Documentation/vm/slub.txt.
3721
David Rientjes3df1ccc2011-10-18 22:09:28 -07003722 slab_max_order= [MM, SLAB]
3723 Determines the maximum allowed order for slabs.
3724 A high setting may cause OOMs due to memory
3725 fragmentation. Defaults to 1 for systems with
3726 more than 32MB of RAM, 0 otherwise.
3727
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003728 slub_debug[=options[,slabs]] [MM, SLUB]
3729 Enabling slub_debug allows one to determine the
3730 culprit if slab objects become corrupted. Enabling
3731 slub_debug can create guard zones around objects and
3732 may poison objects when not in use. Also tracks the
3733 last alloc / free. For more information see
3734 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003735
Tejun Heo1663f262017-02-22 15:41:39 -08003736 slub_memcg_sysfs= [MM, SLUB]
3737 Determines whether to enable sysfs directories for
3738 memory cgroup sub-caches. 1 to enable, 0 to disable.
3739 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3740 Enabling this can lead to a very high number of debug
3741 directories and files being created under
3742 /sys/kernel/slub.
3743
Christoph Lameterc1aee212007-05-31 00:40:47 -07003744 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003745 Determines the maximum allowed order for slabs.
3746 A high setting may cause OOMs due to memory
3747 fragmentation. For more information see
3748 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003749
3750 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003751 The minimum number of objects per slab. SLUB will
3752 increase the slab order up to slub_max_order to
3753 generate a sufficiently large slab able to contain
3754 the number of objects indicated. The higher the number
3755 of objects the smaller the overhead of tracking slabs
3756 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003757 For more information see Documentation/vm/slub.txt.
3758
3759 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003760 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003761 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003762 For more information see Documentation/vm/slub.txt.
3763
3764 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003765 Same with slab_nomerge. This is supported for legacy.
3766 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003767
Linus Torvalds1da177e2005-04-16 15:20:36 -07003768 smart2= [HW]
3769 Format: <io1>[,<io2>[,...,<io8>]]
3770
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003771 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3772 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3773 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3774 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3775 smsc-ircc2.ircc_irq= [HW] IRQ line
3776 smsc-ircc2.ircc_dma= [HW] DMA channel
3777 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3778 0: Toshiba Satellite 1800 (GP data pin select)
3779 1: Fast pin select (default)
3780 2: ATC IRMode
3781
Sascha Silbe52c48c52016-04-05 12:53:38 +02003782 smt [KNL,S390] Set the maximum number of threads (logical
3783 CPUs) to use per physical CPU on systems capable of
3784 symmetric multithreading (SMT). Will be capped to the
3785 actual hardware limit.
3786 Format: <integer>
3787 Default: -1 (no limit)
3788
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003789 softlockup_panic=
3790 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003791 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003792
Aaron Tomlined235872014-06-23 13:22:05 -07003793 softlockup_all_cpu_backtrace=
3794 [KNL] Should the soft-lockup detector generate
3795 backtraces on all cpus.
3796 Format: <integer>
3797
Linus Torvalds1da177e2005-04-16 15:20:36 -07003798 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003799 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003800
Linus Torvalds1da177e2005-04-16 15:20:36 -07003801 spia_io_base= [HW,MTD]
3802 spia_fio_base=
3803 spia_pedr=
3804 spia_peddr=
3805
Paul E. McKenney22607d62017-04-25 14:03:11 -07003806 srcutree.exp_holdoff [KNL]
3807 Specifies how many nanoseconds must elapse
3808 since the end of the last SRCU grace period for
3809 a given srcu_struct until the next normal SRCU
3810 grace period will be considered for automatic
3811 expediting. Set to zero to disable automatic
3812 expediting.
3813
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003814 stacktrace [FTRACE]
3815 Enabled the stack tracer on boot up.
3816
Steven Rostedt762e1202011-12-19 22:01:00 -05003817 stacktrace_filter=[function-list]
3818 [FTRACE] Limit the functions that the stack tracer
3819 will trace at boot up. function-list is a comma separated
3820 list of functions. This list can be changed at run
3821 time by the stack_trace_filter file in the debugfs
3822 tracing directory. Note, this enables stack tracing
3823 and the stacktrace above is not needed.
3824
Linus Torvalds1da177e2005-04-16 15:20:36 -07003825 sti= [PARISC,HW]
3826 Format: <num>
3827 Set the STI (builtin display/keyboard on the HP-PARISC
3828 machines) console (graphic card) which should be used
3829 as the initial boot-console.
3830 See also comment in drivers/video/console/sticore.c.
3831
3832 sti_font= [HW]
3833 See comment in drivers/video/console/sticore.c.
3834
3835 stifb= [HW]
3836 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3837
Trond Myklebustcbf11072009-08-09 15:06:19 -04003838 sunrpc.min_resvport=
3839 sunrpc.max_resvport=
3840 [NFS,SUNRPC]
3841 SunRPC servers often require that client requests
3842 originate from a privileged port (i.e. a port in the
3843 range 0 < portnr < 1024).
3844 An administrator who wishes to reserve some of these
3845 ports for other uses may adjust the range that the
3846 kernel's sunrpc client considers to be privileged
3847 using these two parameters to set the minimum and
3848 maximum port values.
3849
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003850 sunrpc.svc_rpc_per_connection_limit=
3851 [NFS,SUNRPC]
3852 Limit the number of requests that the server will
3853 process in parallel from a single connection.
3854 The default value is 0 (no limit).
3855
Greg Banks42a7fc42007-03-06 01:42:23 -08003856 sunrpc.pool_mode=
3857 [NFS]
3858 Control how the NFS server code allocates CPUs to
3859 service thread pools. Depending on how many NICs
3860 you have and where their interrupts are bound, this
3861 option will affect which CPUs will do NFS serving.
3862 Note: this parameter cannot be changed while the
3863 NFS server is running.
3864
3865 auto the server chooses an appropriate mode
3866 automatically using heuristics
3867 global a single global pool contains all CPUs
3868 percpu one pool for each CPU
3869 pernode one pool for each NUMA node (equivalent
3870 to global on non-NUMA machines)
3871
Trond Myklebustcbf11072009-08-09 15:06:19 -04003872 sunrpc.tcp_slot_table_entries=
3873 sunrpc.udp_slot_table_entries=
3874 [NFS,SUNRPC]
3875 Sets the upper limit on the number of simultaneous
3876 RPC calls that can be sent from the client to a
3877 server. Increasing these values may allow you to
3878 improve throughput, but will also increase the
3879 amount of memory reserved for use by the client.
3880
Brian Norris1d4a9c12015-02-22 21:16:49 -08003881 suspend.pm_test_delay=
3882 [SUSPEND]
3883 Sets the number of seconds to remain in a suspend test
3884 mode before resuming the system (see
3885 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3886 is set. Default value is 5.
3887
Michal Hocko07555ac2013-08-22 16:35:46 -07003888 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003889 [KNL] Enable accounting of swap in memory resource
3890 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003891 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003892
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003893 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003894 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003895 <int> -- Number of I/O TLB slabs
3896 force -- force using of bounce buffers even if they
3897 wouldn't be automatically used by the kernel
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003898 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07003899
Linus Torvalds1da177e2005-04-16 15:20:36 -07003900 switches= [HW,M68k]
3901
Andi Kleene52eec12010-09-08 16:54:17 +02003902 sysfs.deprecated=0|1 [KNL]
3903 Enable/disable old style sysfs layout for old udev
3904 on older distributions. When this option is enabled
3905 very new udev will not work anymore. When this option
3906 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3907 in older udev will not work anymore.
3908 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3909 the kernel configuration.
3910
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003911 sysrq_always_enabled
3912 [KNL]
3913 Ignore sysrq setting - this boot parameter will
3914 neutralize any effect of /proc/sys/kernel/sysrq.
3915 Useful for debugging.
3916
Fabian Frederick747029a2014-11-06 19:46:50 +01003917 tcpmhash_entries= [KNL,NET]
3918 Set the number of tcp_metrics_hash slots.
3919 Default value is 8192 or 16384 depending on total
3920 ram pages. This is used to specify the TCP metrics
3921 cache size. See Documentation/networking/ip-sysctl.txt
3922 "tcp_no_metrics_save" section for more details.
3923
Linus Torvalds1da177e2005-04-16 15:20:36 -07003924 tdfx= [HW,DRM]
3925
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003926 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003927 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003928 standby suspend) or "freeze" (for suspend type freeze)
3929 as the system sleep state during system startup with
3930 the optional capability to repeat N number of times.
3931 The system is woken from this state using a
3932 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003933
Linus Torvalds1da177e2005-04-16 15:20:36 -07003934 thash_entries= [KNL,NET]
3935 Set number of hash buckets for TCP connection
3936
Len Brownf8707ec2007-08-12 00:12:54 -04003937 thermal.act= [HW,ACPI]
3938 -1: disable all active trip points in all thermal zones
3939 <degrees C>: override all lowest active trip points
3940
Len Brownc52a7412007-08-14 15:49:32 -04003941 thermal.crt= [HW,ACPI]
3942 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003943 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003944
Len Brownf5487142007-08-12 00:12:44 -04003945 thermal.nocrt= [HW,ACPI]
3946 Set to disable actions on ACPI thermal zone
3947 critical and hot trip points.
3948
Len Brown72b33ef2007-08-12 00:12:17 -04003949 thermal.off= [HW,ACPI]
3950 1: disable ACPI thermal control
3951
Len Browna70cdc52007-08-12 00:12:35 -04003952 thermal.psv= [HW,ACPI]
3953 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003954 <degrees C>: override all passive trip points to this
3955 value
Len Browna70cdc52007-08-12 00:12:35 -04003956
Len Brown730ff342007-08-12 00:12:26 -04003957 thermal.tzp= [HW,ACPI]
3958 Specify global default ACPI thermal zone polling rate
3959 <deci-seconds>: poll all this frequency
3960 0: no polling (default)
3961
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003962 threadirqs [KNL]
3963 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003964 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003965
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003966 tmem [KNL,XEN]
3967 Enable the Transcendent memory driver if built-in.
3968
3969 tmem.cleancache=0|1 [KNL, XEN]
3970 Default is on (1). Disable the usage of the cleancache
3971 API to send anonymous pages to the hypervisor.
3972
3973 tmem.frontswap=0|1 [KNL, XEN]
3974 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003975 API to send swap pages to the hypervisor. If disabled
3976 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003977
3978 tmem.selfballooning=0|1 [KNL, XEN]
3979 Default is on (1). Disable the driving of swap pages
3980 to the hypervisor.
3981
3982 tmem.selfshrinking=0|1 [KNL, XEN]
3983 Default is on (1). Partial swapoff that immediately
3984 transfers pages from Xen hypervisor back to the
3985 kernel based on different criteria.
3986
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003987 topology= [S390]
3988 Format: {off | on}
3989 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003990 topology information if the hardware supports this.
3991 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003992 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003993 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003994
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003995 topology_updates= [KNL, PPC, NUMA]
3996 Format: {off}
3997 Specify if the kernel should ignore (off)
3998 topology updates sent by the hypervisor to this
3999 LPAR.
4000
Linus Torvalds1da177e2005-04-16 15:20:36 -07004001 tp720= [HW,PS2]
4002
Rajiv Andrade225a9be2010-03-25 00:55:32 -03004003 tpm_suspend_pcr=[HW,TPM]
4004 Format: integer pcr id
4005 Specify that at suspend time, the tpm driver
4006 should extend the specified pcr with zeros,
4007 as a workaround for some chips which fail to
4008 flush the last written pcr on TPM_SaveState.
4009 This will guarantee that all the other pcrs
4010 are saved.
4011
Li Zefan9d612be2009-06-24 17:33:15 +08004012 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09004013 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09004014
Li Zefan020e5f82009-07-01 10:47:05 +08004015 trace_event=[event-list]
4016 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07004017 to facilitate early boot debugging. The event-list is a
4018 comma separated list of trace events to enable. See
4019 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08004020
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04004021 trace_options=[option-list]
4022 [FTRACE] Enable or disable tracer options at boot.
4023 The option-list is a comma delimited list of options
4024 that can be enabled or disabled just as if you were
4025 to echo the option name into
4026
4027 /sys/kernel/debug/tracing/trace_options
4028
4029 For example, to enable stacktrace option (to dump the
4030 stack trace of each event), add to the command line:
4031
4032 trace_options=stacktrace
4033
4034 See also Documentation/trace/ftrace.txt "trace options"
4035 section.
4036
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004037 tp_printk[FTRACE]
4038 Have the tracepoints sent to printk as well as the
4039 tracing ring buffer. This is useful for early boot up
4040 where the system hangs or reboots and does not give the
4041 option for reading the tracing buffer or performing a
4042 ftrace_dump_on_oops.
4043
4044 To turn off having tracepoints sent to printk,
4045 echo 0 > /proc/sys/kernel/tracepoint_printk
4046 Note, echoing 1 into this file without the
4047 tracepoint_printk kernel cmdline option has no effect.
4048
4049 ** CAUTION **
4050
4051 Having tracepoints sent to printk() and activating high
4052 frequency tracepoints such as irq or sched, can cause
4053 the system to live lock.
4054
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004055 traceoff_on_warning
4056 [FTRACE] enable this option to disable tracing when a
4057 warning is hit. This turns off "tracing_on". Tracing can
4058 be enabled again by echoing '1' into the "tracing_on"
4059 file located in /sys/kernel/debug/tracing/
4060
4061 This option is useful, as it disables the trace before
4062 the WARNING dump is called, which prevents the trace to
4063 be filled with content caused by the warning output.
4064
4065 This option can also be set at run time via the sysctl
4066 option: kernel/traceoff_on_warning
4067
Jiri Kosinafcf4d8212012-03-21 16:34:02 -07004068 transparent_hugepage=
4069 [KNL]
4070 Format: [always|madvise|never]
4071 Can be used to control the default behavior of the system
4072 with respect to transparent hugepages.
4073 See Documentation/vm/transhuge.txt for more details.
4074
john stultzd3b8f882009-08-17 16:40:47 -07004075 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004076 Format: <string>
4077 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004078 disables clocksource verification at runtime, as well
4079 as the stability checks done at bootup. Used to enable
4080 high-resolution timer mode on older hardware, and in
4081 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004082 [x86] noirqtime: Do not use TSC to do irq accounting.
4083 Used to run time disable IRQ_TIME_ACCOUNTING on any
4084 platforms where RDTSC is slow and this accounting
4085 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004086
Randy Dunlapa9913042005-10-23 12:57:11 -07004087 turbografx.map[2|3]= [HW,JOY]
4088 TurboGraFX parallel port interface
4089 Format:
4090 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004091 See also Documentation/input/joystick-parport.txt
4092
Christian Kujaub6935f82011-05-31 15:22:05 +00004093 udbg-immortal [PPC] When debugging early kernel crashes that
Jani Nikulae52347b2016-11-03 12:10:10 +02004094 happen after console_init() and before a proper
Christian Kujaub6935f82011-05-31 15:22:05 +00004095 console driver takes over, this boot options might
4096 help "seeing" what's going on.
4097
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004098 uhash_entries= [KNL,NET]
4099 Set number of hash buckets for UDP/UDP-Lite connections
4100
Alan Stern5f8364b2006-12-05 16:29:55 -05004101 uhci-hcd.ignore_oc=
4102 [USB] Ignore overcurrent events (default N).
4103 Some badly-designed motherboards generate lots of
4104 bogus events, for ports that aren't wired to
4105 anything. Set this parameter to avoid log spamming.
4106 Note that genuine overcurrent events won't be
4107 reported either.
4108
Simon Arlotte3a61b02008-07-19 23:32:54 +01004109 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004110 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004111
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004112 usbcore.authorized_default=
4113 [USB] Default USB device authorization:
4114 (default -1 = authorized except for wireless USB,
4115 0 = not authorized, 1 = authorized)
4116
Alan Sternb5e795f2007-02-20 15:00:53 -05004117 usbcore.autosuspend=
4118 [USB] The autosuspend time delay (in seconds) used
4119 for newly-detected USB devices (default 2). This
4120 is the time required before an idle device will be
4121 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004122 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004123
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004124 usbcore.usbfs_snoop=
4125 [USB] Set to log all usbfs traffic (default 0 = off).
4126
Alan Stern0290cc92015-11-20 13:53:22 -05004127 usbcore.usbfs_snoop_max=
4128 [USB] Maximum number of bytes to snoop in each URB
4129 (default = 65536).
4130
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004131 usbcore.blinkenlights=
4132 [USB] Set to cycle leds on hubs (default 0 = off).
4133
4134 usbcore.old_scheme_first=
4135 [USB] Start with the old device initialization
4136 scheme (default 0 = off).
4137
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004138 usbcore.usbfs_memory_mb=
4139 [USB] Memory limit (in MB) for buffers allocated by
4140 usbfs (default = 16, 0 = max = 2047).
4141
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004142 usbcore.use_both_schemes=
4143 [USB] Try the other device initialization scheme
4144 if the first one fails (default 1 = enabled).
4145
4146 usbcore.initial_descriptor_timeout=
4147 [USB] Specifies timeout for the initial 64-byte
4148 USB_REQ_GET_DESCRIPTOR request in milliseconds
4149 (default 5000 = 5.0 seconds).
4150
Oliver Neukum40d58142015-12-03 15:03:32 +01004151 usbcore.nousb [USB] Disable the USB subsystem
4152
Linus Torvalds1da177e2005-04-16 15:20:36 -07004153 usbhid.mousepoll=
4154 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004155
Tobias Jakobi933bfe42017-02-25 20:27:27 +01004156 usbhid.jspoll=
4157 [USBHID] The interval which joysticks are to be polled at.
4158
Alan Sternd4f373e2008-11-10 14:07:45 -05004159 usb-storage.delay_use=
4160 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004161 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004162
4163 usb-storage.quirks=
4164 [UMS] A list of quirks entries to supplement or
4165 override the built-in unusual_devs list. List
4166 entries are separated by commas. Each entry has
4167 the form VID:PID:Flags where VID and PID are Vendor
4168 and Product ID values (4-digit hex numbers) and
4169 Flags is a set of characters, each corresponding
4170 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004171 a = SANE_SENSE (collect more than 18 bytes
4172 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004173 b = BAD_SENSE (don't collect more than 18
4174 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004175 c = FIX_CAPACITY (decrease the reported
4176 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004177 d = NO_READ_DISC_INFO (don't use
4178 READ_DISC_INFO command);
4179 e = NO_READ_CAPACITY_16 (don't use
4180 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004181 f = NO_REPORT_OPCODES (don't use report opcodes
4182 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004183 g = MAX_SECTORS_240 (don't transfer more than
4184 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004185 h = CAPACITY_HEURISTICS (decrease the
4186 reported device capacity by one
4187 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004188 i = IGNORE_DEVICE (don't bind to this
4189 device);
Hans de Goede13630742016-04-12 12:27:09 +02004190 j = NO_REPORT_LUNS (don't use report luns
4191 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004192 l = NOT_LOCKABLE (don't try to lock and
4193 unlock ejectable media);
4194 m = MAX_SECTORS_64 (don't transfer more
4195 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004196 n = INITIAL_READ10 (force a retry of the
4197 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004198 o = CAPACITY_OK (accept the capacity
4199 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004200 p = WRITE_CACHE (the device cache is ON
4201 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004202 r = IGNORE_RESIDUE (the device reports
4203 bogus residue values);
4204 s = SINGLE_LUN (the device has only one
4205 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004206 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4207 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004208 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004209 w = NO_WP_DETECT (don't test whether the
4210 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004211 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4212 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004213 Example: quirks=0419:aaf5:rl,0421:0433:rc
4214
Stephen Boydac1667d2011-08-13 12:34:50 -07004215 user_debug= [KNL,ARM]
4216 Format: <int>
4217 See arch/arm/Kconfig.debug help text.
4218 1 - undefined instruction events
4219 2 - system calls
4220 4 - invalid data aborts
4221 8 - SIGSEGV faults
4222 16 - SIGBUS faults
4223 Example: user_debug=31
4224
Ian Campbell14315592010-02-17 10:38:10 +00004225 userpte=
4226 [X86] Flags controlling user PTE allocations.
4227
4228 nohigh = do not allocate PTE pages in
4229 HIGHMEM regardless of setting
4230 of CONFIG_HIGHPTE.
4231
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304232 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004233 On X86_32, this is an alias for vdso32=. Otherwise:
4234
4235 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004236 vdso=0: disable VDSO mapping
4237
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004238 vdso32= [X86] Control the 32-bit vDSO
4239 vdso32=1: enable 32-bit VDSO
4240 vdso32=0 or vdso32=2: disable 32-bit VDSO
4241
4242 See the help text for CONFIG_COMPAT_VDSO for more
4243 details. If CONFIG_COMPAT_VDSO is set, the default is
4244 vdso32=0; otherwise, the default is vdso32=1.
4245
4246 For compatibility with older kernels, vdso32=2 is an
4247 alias for vdso32=0.
4248
4249 Try vdso32=0 if you encounter an error that says:
4250 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004251
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004252 vector= [IA-64,SMP]
4253 vector=percpu: enable percpu vector domain
4254
Linus Torvalds1da177e2005-04-16 15:20:36 -07004255 video= [FB] Frame buffer configuration
4256 See Documentation/fb/modedb.txt.
4257
Aaron Lu3afe6da2013-06-20 15:08:55 +08004258 video.brightness_switch_enabled= [0,1]
4259 If set to 1, on receiving an ACPI notify event
4260 generated by hotkey, video driver will adjust brightness
4261 level and then send out the event to user space through
4262 the allocated input device; If set to 0, video driver
4263 will only send out the event without touching backlight
4264 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004265 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004266
Pawel Moll81a054c2012-05-09 18:30:16 +01004267 virtio_mmio.device=
4268 [VMMIO] Memory mapped virtio (platform) device.
4269
4270 <size>@<baseaddr>:<irq>[:<id>]
4271 where:
4272 <size> := size (can use standard suffixes
4273 like K, M and G)
4274 <baseaddr> := physical base address
4275 <irq> := interrupt number (as passed to
4276 request_irq())
4277 <id> := (optional) platform device id
4278 example:
4279 virtio_mmio.device=1K@0x100b0000:48:7
4280
4281 Can be used multiple times for multiple devices.
4282
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004283 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004284 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004285 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004286 Use vga=ask for menu.
4287 This is actually a boot loader parameter; the value is
4288 passed to the kernel using a special protocol.
4289
Randy Dunlapa9913042005-10-23 12:57:11 -07004290 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004291 size of <nn>. This can be used to increase the
4292 minimum size (128MB on x86). It can also be used to
4293 decrease the size and leave more room for directly
4294 mapped kernel RAM.
4295
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004296 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4297 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004298
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004299 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4300 Format: <command>
4301
4302 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4303 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004304
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004305 vsyscall= [X86-64]
4306 Controls the behavior of vsyscalls (i.e. calls to
4307 fixed addresses of 0xffffffffff600x00 from legacy
4308 code). Most statically-linked binaries and older
4309 versions of glibc use these calls. Because these
4310 functions are at fixed addresses, they make nice
4311 targets for exploits that can control RIP.
4312
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004313 emulate [default] Vsyscalls turn into traps and are
4314 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004315
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004316 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004317 This is a little bit faster than trapping
4318 and makes a few dynamic recompilers work
4319 better than they would in emulation mode.
4320 It also makes exploits much easier to write.
4321
4322 none Vsyscalls don't work at all. This makes
4323 them quite hard to use for exploits but
4324 might break your system.
4325
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004326 vt.color= [VT] Default text color.
4327 Format: 0xYX, X = foreground, Y = background.
4328 Default: 0x07 = light gray on black.
4329
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004330 vt.cur_default= [VT] Default cursor shape.
4331 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4332 the parameters of the <Esc>[?A;B;Cc escape sequence;
4333 see VGA-softcursor.txt. Default: 2 = underline.
4334
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004335 vt.default_blu= [VT]
4336 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4337 Change the default blue palette of the console.
4338 This is a 16-member array composed of values
4339 ranging from 0-255.
4340
4341 vt.default_grn= [VT]
4342 Format: <green0>,<green1>,<green2>,...,<green15>
4343 Change the default green palette of the console.
4344 This is a 16-member array composed of values
4345 ranging from 0-255.
4346
4347 vt.default_red= [VT]
4348 Format: <red0>,<red1>,<red2>,...,<red15>
4349 Change the default red palette of the console.
4350 This is a 16-member array composed of values
4351 ranging from 0-255.
4352
4353 vt.default_utf8=
4354 [VT]
4355 Format=<0|1>
4356 Set system-wide default UTF-8 mode for all tty's.
4357 Default is 1, i.e. UTF-8 mode is enabled for all
4358 newly opened terminals.
4359
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004360 vt.global_cursor_default=
4361 [VT]
4362 Format=<-1|0|1>
4363 Set system-wide default for whether a cursor
4364 is shown on new VTs. Default is -1,
4365 i.e. cursors will be created by default unless
4366 overridden by individual drivers. 0 will hide
4367 cursors, 1 will display them.
4368
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004369 vt.italic= [VT] Default color for italic text; 0-15.
4370 Default: 2 = green.
4371
4372 vt.underline= [VT] Default color for underlined text; 0-15.
4373 Default: 3 = cyan.
4374
Randy Dunlap4724ba572010-05-03 11:42:52 -07004375 watchdog timers [HW,WDT] For information on watchdog timers,
4376 see Documentation/watchdog/watchdog-parameters.txt
4377 or other driver-specific files in the
4378 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004379
Tejun Heo82607adc2015-12-08 11:28:04 -05004380 workqueue.watchdog_thresh=
4381 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4382 warn stall conditions and dump internal state to
4383 help debugging. 0 disables workqueue stall
4384 detection; otherwise, it's the stall threshold
4385 duration in seconds. The default value is 30 and
4386 it can be updated at runtime by writing to the
4387 corresponding sysfs file.
4388
Tejun Heod55262c2013-04-01 11:23:38 -07004389 workqueue.disable_numa
4390 By default, all work items queued to unbound
4391 workqueues are affine to the NUMA nodes they're
4392 issued on, which results in better behavior in
4393 general. If NUMA affinity needs to be disabled for
4394 whatever reason, this option can be used. Note
4395 that this also can be controlled per-workqueue for
4396 workqueues visible under /sys/bus/workqueue/.
4397
Viresh Kumarcee22a12013-04-08 16:45:40 +05304398 workqueue.power_efficient
4399 Per-cpu workqueues are generally preferred because
4400 they show better performance thanks to cache
4401 locality; unfortunately, per-cpu workqueues tend to
4402 be more power hungry than unbound workqueues.
4403
4404 Enabling this makes the per-cpu workqueues which
4405 were observed to contribute significantly to power
4406 consumption unbound, leading to measurably lower
4407 power usage at the cost of small performance
4408 overhead.
4409
4410 The default value of this parameter is determined by
4411 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4412
Tejun Heof303fccb2016-02-09 17:59:38 -05004413 workqueue.debug_force_rr_cpu
4414 Workqueue used to implicitly guarantee that work
4415 items queued without explicit CPU specified are put
4416 on the local CPU. This guarantee is no longer true
4417 and while local CPU is still preferred work items
4418 may be put on foreign CPUs. This debug option
4419 forces round-robin CPU selection to flush out
4420 usages which depend on the now broken guarantee.
4421 When enabled, memory and cache locality will be
4422 impacted.
4423
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004424 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4425 default x2apic cluster mode on platforms
4426 supporting x2apic.
4427
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004428 x86_intel_mid_timer= [X86-32,APBT]
4429 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004430 Two valid options are apbt timer only and lapic timer
4431 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004432 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004433
Juergen Grossc70727a2015-07-17 06:51:36 +02004434 xen_512gb_limit [KNL,X86-64,XEN]
4435 Restricts the kernel running paravirtualized under Xen
4436 to use only up to 512 GB of RAM. The reason to do so is
4437 crash analysis tools and Xen tools for doing domain
4438 save/restore/migration must be enabled to handle larger
4439 domains.
4440
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004441 xen_emul_unplug= [HW,X86,XEN]
4442 Unplug Xen emulated devices
4443 Format: [unplug0,][unplug1]
4444 ide-disks -- unplug primary master IDE devices
4445 aux-ide-disks -- unplug non-primary-master IDE devices
4446 nics -- unplug network devices
4447 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004448 unnecessary -- unplugging emulated devices is
4449 unnecessary even if the host did not respond to
4450 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004451 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004452
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004453 xen_nopvspin [X86,XEN]
4454 Disables the ticketlock slowpath using Xen PV
4455 optimizations.
4456
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004457 xen_nopv [X86]
4458 Disables the PV optimizations forcing the HVM guest to
4459 run as generic HVM guest with no PV drivers.
4460
Linus Torvalds1da177e2005-04-16 15:20:36 -07004461 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004462 Format:
4463 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]