blob: 110745e7d61f89bd57bd580af148c6654a985dc3 [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
534 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700535 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700536 scx200_hrt on Geode; cyclone on IBM x440
537 [MIPS] MIPS
538 [PARISC] cr16
539 [S390] tod
540 [SH] SuperH
541 [SPARC64] tick
542 [X86-64] hpet,tsc
543
Will Deacon46fd5c62016-06-27 17:30:13 +0100544 clocksource.arm_arch_timer.evtstrm=
545 [ARM,ARM64]
546 Format: <bool>
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
550 systems.
551
Scott Woodf6dc1572016-09-22 03:35:17 -0500552 clocksource.arm_arch_timer.fsl-a008585=
553 [ARM64]
554 Format: <bool>
555 Enable/disable the workaround of Freescale/NXP
556 erratum A-008585. This can be useful for KVM
557 guests, if the guest device tree doesn't show the
558 erratum. If unspecified, the workaround is
559 enabled based on the device tree.
560
Andi Kleenac72e782008-01-30 13:33:21 +0100561 clearcpuid=BITNUM [X86]
562 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100563 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800564 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100565 stable over kernel options, but the vendor specific
566 ones should be.
567 Also note that user programs calling CPUID directly
568 or using the feature without checking anything
569 will still see it. This just prevents it from
570 being used by the kernel or shown in /proc/cpuinfo.
571 Also note the kernel might malfunction if you disable
572 some critical bits.
573
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700574 cma=nn[MG]@[start[MG][-end[MG]]]
575 [ARM,X86,KNL]
576 Sets the size of kernel global memory area for
577 contiguous memory allocations and optionally the
578 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700579 memory allocations. A value of 0 disables CMA
580 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100581 include/linux/dma-contiguous.h
582
Robert Jennings14f966e2009-04-15 05:55:32 +0000583 cmo_free_hint= [PPC] Format: { yes | no }
584 Specify whether pages are marked as being inactive
585 when they are freed. This is used in CMO environments
586 to determine OS memory pressure for page stealing by
587 a hypervisor.
588 Default: yes
589
Marek Szyprowskic7909502011-12-29 13:09:51 +0100590 coherent_pool=nn[KMG] [ARM,KNL]
591 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200592 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100593
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530594 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100595 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100596 Range: 0 - 8192
597 Default: 64
598
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700600 Format:
601 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602
603 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
604 Format: <io>[,<irq>]
605
Randy Dunlapa9913042005-10-23 12:57:11 -0700606 com90xx= [HW,NET]
607 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 Format: <io>[,<irq>[,<memstart>]]
609
610 condev= [HW,S390] console device
611 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700612
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 console= [KNL] Output console device and options.
614
615 tty<n> Use the virtual console device <n>.
616
617 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800618 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800620 the form "bbbbpnf", where "bbbb" is the baud rate,
621 "p" is parity ("n", "o", or "e"), "n" is number of
622 bits, and "f" is flow control ("r" for RTS or
623 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624
Jani Nikulae52347b2016-11-03 12:10:10 +0200625 See Documentation/admin-guide/serial-console.rst for more
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800626 information. See
627 Documentation/networking/netconsole.txt for an
628 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700630 uart[8250],io,<addr>[,options]
631 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900632 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400633 uart[8250],mmio32,<addr>[,options]
634 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 Start an early, polled-mode console on the 8250/16550
636 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400637 switching to the matching ttyS device later.
638 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900639 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
640 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
641 to be equivalent to 'mmio'. 'options' are specified in
642 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400643 the h/w is not re-initialized.
644
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500645 hvc<n> Use the hypervisor console device <n>. This is for
646 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700648 If the device connected to the port is not a TTY but a braille
649 device, prepend "brl," before the device type, for instance
650 console=brl,ttyS0
651 For now, only VisioBraille is supported.
652
Daniel Mackf324edc2009-06-16 15:33:52 -0700653 consoleblank= [KNL] The console blank (screen saver) timeout in
654 seconds. Defaults to 10*60 = 10mins. A value of 0
655 disables the blank timer.
656
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800657 coredump_filter=
658 [KNL] Change the default value for
659 /proc/<pid>/coredump_filter.
660 See also Documentation/filesystems/proc.txt.
661
Len Brown62027ae2011-04-01 18:13:10 -0400662 cpuidle.off=1 [CPU_IDLE]
663 disable the cpuidle sub-system
664
Len Brownd68921f2015-05-11 17:27:09 -0400665 cpu_init_udelay=N
666 [X86] Delay for N microsec between assert and de-assert
667 of APIC INIT to start processors. This delay occurs
668 on every CPU online, such as boot, and resume from suspend.
669 Default: 10000
670
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700672 Format:
673 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800675 crashkernel=size[KMG][@offset[KMG]]
676 [KNL] Using kexec, Linux can switch to a 'crash kernel'
677 upon panic. This parameter reserves the physical
678 memory region [offset, offset + size] for that kernel
679 image. If '@offset' is omitted, then a suitable offset
680 is selected automatically. Check
681 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700682
Bernhard Wallefb391592007-10-18 23:41:02 -0700683 crashkernel=range1:size1[,range2:size2,...][@offset]
684 [KNL] Same as above, but depends on the memory
685 in the running system. The syntax of range is
686 start-[end] where start and end are both
687 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800688 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700689
Yinghai Luadbc7422013-04-15 22:23:48 -0700690 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700691 [KNL, x86_64] range could be above 4G. Allow kernel
692 to allocate physical memory region from top, so could
693 be above 4G if system have more than 4G ram installed.
694 Otherwise memory region will be allocated below 4G, if
695 available.
696 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700697 crashkernel=size[KMG],low
698 [KNL, x86_64] range under 4G. When crashkernel=X,high
699 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700700 above 4G, that cause second kernel crash on system
701 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800702 requires at least 64M+32K low memory, also enough extra
703 low memory is needed to make sure DMA buffers for 32-bit
704 devices won't run out. Kernel would try to allocate at
705 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700706 This one let user to specify own low range under 4G
707 for second kernel instead.
708 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700709 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700710 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700711
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100712 cryptomgr.notests
713 [KNL] Disable crypto self-tests
714
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 cs89x0_dma= [HW,NET]
716 Format: <dma>
717
718 cs89x0_media= [HW,NET]
719 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700720
Randy Dunlapa9913042005-10-23 12:57:11 -0700721 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 See header of drivers/s390/block/dasd_devmap.c.
723
724 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
725 (one device per port)
726 Format: <port#>,<type>
727 See also Documentation/input/joystick-parport.txt
728
Thomas Renningera648ec02010-08-06 16:11:02 +0200729 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
730 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600731 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200732
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 debug [KNL] Enable kernel debugging (events log level).
734
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700735 debug_locks_verbose=
736 [KNL] verbose self-tests
737 Format=<0|1>
738 Print debugging info while doing the locking API
739 self-tests.
740 We default to 0 (no extra messages), setting it to
741 1 will print _a lot_ more information - normally
742 only useful to kernel developers.
743
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700744 debug_objects [KNL] Enable object debugging
745
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500746 no_debug_objects
747 [KNL] Disable object debugging
748
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800749 debug_guardpage_minorder=
750 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
751 parameter allows control of the order of pages that will
752 be intentionally kept free (and hence protected) by the
753 buddy allocator. Bigger value increase the probability
754 of catching random memory corruption, but reduce the
755 amount of memory for normal system use. The maximum
756 possible value is MAX_ORDER/2. Setting this parameter
757 to 1 or 2 should be enough to identify most random
758 memory corruption problems caused by bugs in kernel or
759 driver code when a CPU writes to (or reads from) a
760 random memory location. Note that there exists a class
761 of memory corruptions problems caused by buggy H/W or
762 F/W or by drivers badly programing DMA (basically when
763 memory is written at bus level and the CPU MMU is
764 bypassed) which are not detectable by
765 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
766 tracking down these problems.
767
Joonsoo Kim031bc572014-12-12 16:55:52 -0800768 debug_pagealloc=
769 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
770 parameter enables the feature at boot time. In
771 default, it is disabled. We can avoid allocating huge
772 chunk of memory for debug pagealloc if we don't enable
773 it at boot time and the system will work mostly same
774 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
775 on: enable the feature
776
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200777 debugpat [X86] Enable PAT debugging
778
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200779 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700780 Format: <area>[,<node>]
781 See also Documentation/networking/decnet.txt.
782
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700783 default_hugepagesz=
784 [same as hugepagesz=] The size of the default
785 HugeTLB page size. This is the size represented by
786 the legacy /proc/ hugepages APIs, used for SHM, and
787 default size when mounting hugetlbfs filesystems.
788 Defaults to the default architecture's huge page size
789 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700790
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791 dhash_entries= [KNL]
792 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700793
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000794 disable_1tb_segments [PPC]
795 Disables the use of 1TB hash page table segments. This
796 causes the kernel to fall back to 256MB segments which
797 can be useful when debugging issues that require an SLB
798 miss to occur.
799
Brian Haleyb0f83b22010-02-04 13:36:50 -0800800 disable= [IPV6]
801 See Documentation/networking/ipv6.txt.
802
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530803 disable_radix [PPC]
804 Disable RADIX MMU mode on POWER9
805
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900806 disable_cpu_apicid= [X86,APIC,SMP]
807 Format: <int>
808 The number of initial APIC ID for the
809 corresponding CPU to be disabled at boot,
810 mostly used for the kdump 2nd kernel to
811 disable BSP to wake up multiple CPUs without
812 causing system reset or hang due to sending
813 INIT from AP to BSP.
814
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000815 disable_ddw [PPC/PSERIES]
816 Disable Dynamic DMA Window support. Use this if
817 to workaround buggy firmware.
818
Brian Haleyb0f83b22010-02-04 13:36:50 -0800819 disable_ipv6= [IPV6]
820 See Documentation/networking/ipv6.txt.
821
Yinghai Lu95ffa242008-04-29 03:52:33 -0700822 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700823 The kernel tries to adjust MTRR layout from continuous
824 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700825 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700826
Yinghai Lu093af8d2008-01-30 13:33:32 +0100827 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100828 By default the kernel will trim any uncacheable
829 memory out of your available memory pool based on
830 MTRR settings. This parameter disables that behavior,
831 possibly causing your machine to run very slowly.
832
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530833 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700834 Disable PIN 1 of APIC timer
835 Can be useful to work around chipset bugs.
836
Prarit Bhargavace14c582015-08-25 13:34:53 -0400837 dis_ucode_ldr [X86] Disable the microcode loader.
838
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700839 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
840 this option disables the debugging code at boot.
841
842 dma_debug_entries=<number>
843 This option allows to tune the number of preallocated
844 entries for DMA-API debugging code. One entry is
845 required per DMA-API allocation. Use this if the
846 DMA-API debugging code disables itself because the
847 architectural default is too low.
848
Joerg Roedel1745de52009-05-22 21:49:51 +0200849 dma_debug_driver=<driver_name>
850 With this option the DMA-API debugging driver
851 filter feature can be enabled at boot time. Just
852 pass the driver to filter for as the parameter.
853 The filter can be disabled or changed to another
854 driver later using sysfs.
855
Bob Paauwe96206e22015-08-27 10:04:13 -0700856 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
857 Broken monitors, graphic adapters, KVMs and EDIDless
858 panels may send no or incorrect EDID data sets.
859 This parameter allows to specify an EDID data sets
860 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100861 Generic built-in EDID data sets are used, if one of
862 edid/1024x768.bin, edid/1280x1024.bin,
863 edid/1680x1050.bin, or edid/1920x1080.bin is given
864 and no file with the same name exists. Details and
865 instructions how to build your own EDID data are
866 available in Documentation/EDID/HOWTO.txt. An EDID
867 data set will only be used for a particular connector,
868 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700869 name. Each connector may use a unique EDID data
870 set by separating the files with a comma. An EDID
871 data set with no connector name will be used for
872 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100873
Linus Torvalds1da177e2005-04-16 15:20:36 -0700874 dscc4.setup= [NET]
875
Lukas Wunner58c54752016-11-12 21:32:36 +0000876 dump_apple_properties [X86]
877 Dump name and content of EFI device properties on
878 x86 Macs. Useful for driver authors to determine
879 what data is available or for reverse-engineering.
880
Jim Cromie29e36c92012-04-27 14:30:41 -0600881 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
882 module.dyndbg[="val"]
883 Enable debug messages at boot time. See
884 Documentation/dynamic-debug-howto.txt for details.
885
Dave Hansen8c3641e2015-06-07 11:37:02 -0700886 nompx [X86] Disables Intel Memory Protection Extensions.
887 See Documentation/x86/intel_mpx.txt for more
888 information about the feature.
889
Dave Hansen06976942016-02-12 13:02:29 -0800890 nopku [X86] Disable Memory Protection Keys CPU feature found
891 in some Intel CPUs.
892
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700893 module.async_probe [KNL]
894 Enable asynchronous probe on this module.
895
Mark Salter56aeeba2014-04-07 15:39:53 -0700896 early_ioremap_debug [KNL]
897 Enable debug messages in early_ioremap support. This
898 is useful for tracking down temporary early mappings
899 which are not unmapped.
900
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700901 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500902
Scott Wood5664f762015-09-14 19:54:07 -0500903 When used with no options, the early console is
904 determined by the stdout-path property in device
905 tree's chosen node.
906
Scott Telfordc41251b2016-09-22 16:58:16 +0100907 cdns,<addr>[,options]
908 Start an early, polled-mode console on a Cadence
909 (xuartps) serial port at the specified address. Only
910 supported option is baud rate. If baud rate is not
911 specified, the serial port must already be setup and
912 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +0200913
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700914 uart[8250],io,<addr>[,options]
915 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700916 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300917 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400918 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700919 Start an early, polled-mode console on the 8250/16550
920 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700921 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300922 (mmio) or 32-bit (mmio32 or mmio32be).
923 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
924 to be equivalent to 'mmio'. 'options' are specified
925 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400926 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700927
Rob Herring0d3c6732014-04-18 17:19:57 -0500928 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -0600929 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -0500930 Start an early, polled-mode console on a pl011 serial
931 port at the specified address. The pl011 serial port
932 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -0600933 yet supported. If 'mmio32' is specified, then only
934 the driver will use only 32-bit accessors to read/write
935 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -0500936
Andreas Färber736d5532016-03-06 12:21:24 +0100937 meson,<addr>
938 Start an early, polled-mode console on a meson serial
939 port at the specified address. The serial port must
940 already be setup and configured. Options are not yet
941 supported.
942
Stephen Boyd0efe7292014-09-15 17:22:51 -0700943 msm_serial,<addr>
944 Start an early, polled-mode console on an msm serial
945 port at the specified address. The serial port
946 must already be setup and configured. Options are not
947 yet supported.
948
949 msm_serial_dm,<addr>
950 Start an early, polled-mode console on an msm serial
951 dm port at the specified address. The serial port
952 must already be setup and configured. Options are not
953 yet supported.
954
Rob Herringd50d7262014-04-18 17:19:58 -0500955 smh Use ARM semihosting calls for early console.
956
Tomasz Figab94ba032015-01-23 14:47:41 +0100957 s3c2410,<addr>
958 s3c2412,<addr>
959 s3c2440,<addr>
960 s3c6400,<addr>
961 s5pv210,<addr>
962 exynos4210,<addr>
963 Use early console provided by serial driver available
964 on Samsung SoCs, requires selecting proper type and
965 a correct base address of the selected UART port. The
966 serial port must already be setup and configured.
967 Options are not yet supported.
968
Stefan Agner1d59b382015-10-17 00:45:55 -0700969 lpuart,<addr>
970 lpuart32,<addr>
971 Use early console provided by Freescale LP UART driver
972 found on Freescale Vybrid and QorIQ LS1021A processors.
973 A valid base address must be provided, and the serial
974 port must already be setup and configured.
975
Wilson Ding30530792016-02-16 19:14:53 +0100976 armada3700_uart,<addr>
977 Start an early, polled-mode console on the
978 Armada 3700 serial port at the specified
979 address. The serial port must already be setup
980 and configured. Options are not yet supported.
981
Finn Thain7913ad12014-04-12 23:48:56 +1000982 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100984 earlyprintk=efi
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]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991
Dave Hansen147ea092013-04-10 14:03:38 -0700992 earlyprintk is useful when the kernel crashes before
993 the normal console is initialized. It is not enabled by
994 default because it has some cosmetic problems.
995
Randy Dunlapa9913042005-10-23 12:57:11 -0700996 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997 takes over.
998
Matt Fleming72548e82013-10-04 09:36:56 +0100999 Only one of vga, efi, serial, or usb debug port can
1000 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001
Dave Hansen147ea092013-04-10 14:03:38 -07001002 Currently only ttyS0 and ttyS1 may be specified by
1003 name. Other I/O ports may be explicitly specified
1004 on some architectures (x86 and arm at least) by
1005 replacing ttySn with an I/O port address, like this:
1006 earlyprintk=serial,0x1008,115200
1007 You can find the port for a given device in
1008 /proc/tty/driver/serial:
1009 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010
1011 Interaction with the standard serial driver is not
1012 very good.
1013
Matt Fleming72548e82013-10-04 09:36:56 +01001014 The VGA and EFI output is eventually overwritten by
1015 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001017 The xen output can only be used by Xen PV guests.
1018
Chen, Gongc700f012013-12-06 01:17:08 -05001019 edac_report= [HW,EDAC] Control how to report EDAC event
1020 Format: {"on" | "off" | "force"}
1021 on: enable EDAC to report H/W event. May be overridden
1022 by other higher priority error reporting module.
1023 off: disable H/W event reporting through EDAC.
1024 force: enforce the use of EDAC to report H/W event.
1025 default: on.
1026
Jason Wessel97311912010-05-20 21:04:30 -05001027 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1028 ekgdboc=kbd
1029
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001030 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001031 the boot argument: earlyprintk=vga
1032
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001034 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001036 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001037 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001038 old_map [X86-64]: switch to the old ioremap-based EFI
1039 runtime services mapping. 32-bit still uses this one by
1040 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001041 nochunk: disable reading files in "chunks" in the EFI
1042 boot stub, as chunking can cause problems with some
1043 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001044 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001045 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001046
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001047 efi_no_storage_paranoia [EFI; X86]
1048 Using this parameter you can use more than 50% of
1049 your efi variable storage. Use this parameter only if
1050 you are really sure that your UEFI does sane gc and
1051 fulfills the spec otherwise your board may brick.
1052
Taku Izumi0f96a992015-09-30 23:01:56 +09001053 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1054 Add arbitrary attribute to specific memory range by
1055 updating original EFI memory map.
1056 Region of memory which aa attribute is added to is
1057 from ss to ss+nn.
1058 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1059 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1060 attribute is added to range 0x100000000-0x180000000 and
1061 0x10a0000000-0x1120000000.
1062
1063 Using this parameter you can do debugging of EFI memmap
1064 related feature. For example, you can do debugging of
1065 Address Range Mirroring feature even if your box
1066 doesn't support it.
1067
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001068 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1069 that is to be dynamically loaded by Linux. If there are
1070 multiple variables with the same name but with different
1071 vendor GUIDs, all of them will be loaded. See
1072 Documentation/acpi/ssdt-overlays.txt for details.
1073
1074
Linus Torvalds1da177e2005-04-16 15:20:36 -07001075 eisa_irq_edge= [PARISC,HW]
1076 See header of drivers/parisc/eisa.c.
1077
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001078 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001080 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081
1082 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001083 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001084 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001085 Documentation/block/deadline-iosched.txt for details.
1086
Michael Holzheud3bf37952011-10-30 15:16:37 +01001087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001088 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001089 image elf header and optionally the size. Generally
1090 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001091 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001093 enable_mtrr_cleanup [X86]
1094 The kernel tries to adjust MTRR layout from continuous
1095 to discrete, to make X server driver able to add WB
1096 entry later. This parameter enables that.
1097
Randy Dunlapca1eda22009-05-06 16:02:58 -07001098 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001099 Enable PIN 1 of APIC timer
1100 Can be useful to work around chipset bugs
1101 (in particular on some ATI chipsets).
1102 The kernel tries to set a reasonable default.
1103
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104 enforcing [SELINUX] Set initial enforcing status.
1105 Format: {"0" | "1"}
1106 See security/selinux/Kconfig help text.
1107 0 -- permissive (log only, no denials).
1108 1 -- enforcing (deny and log).
1109 Default value is 0.
1110 Value can be changed at runtime via /selinux/enforce.
1111
Huang Yinga08f82d2010-05-18 14:35:21 +08001112 erst_disable [ACPI]
1113 Disable Error Record Serialization Table (ERST)
1114 support.
1115
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116 ether= [HW,NET] Ethernet cards parameters
1117 This option is obsoleted by the "netdev=" option, which
1118 has equivalent usage. See its documentation for details.
1119
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001120 evm= [EVM]
1121 Format: { "fix" }
1122 Permit 'security.evm' to be updated regardless of
1123 current integrity status.
1124
Akinobu Mitade1ba092006-12-08 02:39:42 -08001125 failslab=
1126 fail_page_alloc=
1127 fail_make_request=[KNL]
1128 General fault injection mechanism.
1129 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001130 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001131
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001133 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134
Alex Chiangf13ae302008-05-08 14:03:23 -06001135 force_pal_cache_flush
1136 [IA-64] Avoid check_sal_cache_flush which may hang on
1137 buggy SAL_CACHE_FLUSH implementations. Using this
1138 parameter will force ia64_sal_cache_flush to call
1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1140
Chris Bainbridge69f23662014-03-07 18:40:42 +07001141 forcepae [X86-32]
1142 Forcefully enable Physical Address Extension (PAE).
1143 Many Pentium M systems disable PAE but may have a
1144 functionally usable PAE implementation.
1145 Warning: use of this parameter will taint the kernel
1146 and may cause unknown problems.
1147
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001148 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001149 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001150 as early as possible in order to facilitate early
1151 boot debugging.
1152
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001153 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001154 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001155 If no parameter is passed, ftrace will dump
1156 buffers of all CPUs, but if you pass orig_cpu, it will
1157 dump only the buffer of the CPU that triggered the
1158 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001159
1160 ftrace_filter=[function-list]
1161 [FTRACE] Limit the functions traced by the function
1162 tracer at boot up. function-list is a comma separated
1163 list of functions. This list can be changed at run
1164 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001165 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001166
1167 ftrace_notrace=[function-list]
1168 [FTRACE] Do not trace the functions specified in
1169 function-list. This list can be changed at run time
1170 by the set_ftrace_notrace file in the debugfs
1171 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001172
Stefan Assmann369bc182009-10-12 22:17:21 +02001173 ftrace_graph_filter=[function-list]
1174 [FTRACE] Limit the top level callers functions traced
1175 by the function graph tracer at boot up.
1176 function-list is a comma separated list of functions
1177 that can be changed at run time by the
1178 set_graph_function file in the debugfs tracing directory.
1179
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001180 ftrace_graph_notrace=[function-list]
1181 [FTRACE] Do not trace from the functions specified in
1182 function-list. This list is a comma separated list of
1183 functions that can be changed at run time by the
1184 set_graph_notrace file in the debugfs tracing directory.
1185
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 gamecon.map[2|3]=
1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1188 support via parallel port (up to 5 devices per port)
1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1190 See also Documentation/input/joystick-parport.txt
1191
1192 gamma= [HW,DRM]
1193
Yinghai Luaaf23042008-01-30 13:33:09 +01001194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1195 Format: off | on
1196 default: on
1197
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001198 gcov_persist= [GCOV] When non-zero (default), profiling data for
1199 kernel modules is saved and remains accessible via
1200 debugfs, even when the module is unloaded/reloaded.
1201 When zero, profiling data is discarded and associated
1202 debugfs files are removed at module unload time.
1203
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001205 invalid Protective MBR to be treated as GPT. If the
1206 primary GPT is corrupted, it enables the backup/alternate
1207 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001209 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1210 the "Enable 0" bit of the configuration register.
1211 Format: 0 | 1
1212 Default: 0
1213 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1214 the "Enable 0" bit of the configuration register.
1215 Format: 0 | 1
1216 Default: 0
1217 grcan.select= [HW] Select which physical interface to use.
1218 Format: 0 | 1
1219 Default: 0
1220 grcan.txsize= [HW] Sets the size of the tx buffer.
1221 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1222 Default: 1024
1223 grcan.rxsize= [HW] Sets the size of the rx buffer.
1224 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1225 Default: 1024
1226
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001227 gpio-mockup.gpio_mockup_ranges
1228 [HW] Sets the ranges of gpiochip of for this device.
1229 Format: <start1>,<end1>,<start2>,<end2>...
1230
Jiri Kosina55537872015-11-05 18:44:41 -08001231 hardlockup_all_cpu_backtrace=
1232 [KNL] Should the hard-lockup detector generate
1233 backtraces on all cpus.
1234 Format: <integer>
1235
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 hashdist= [KNL,NUMA] Large hashes allocated during boot
1237 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001238 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001239 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240
1241 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1242
1243 hd= [EIDE] (E)IDE hard drive subsystem geometry
1244 Format: <cyl>,<head>,<sect>
1245
Huang Yingea8c0712010-05-18 14:35:15 +08001246 hest_disable [ACPI]
1247 Disable Hardware Error Source Table (HEST) support;
1248 corresponding firmware-first mode error processing
1249 logic will be disabled.
1250
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1252 size of <nn>. This works even on boxes that have no
1253 highmem otherwise. This also works to reduce highmem
1254 size on bigger boxes.
1255
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001256 highres= [KNL] Enable/disable high resolution timer mode.
1257 Valid parameters: "on", "off"
1258 Default: "on"
1259
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 hisax= [HW,ISDN]
1261 See Documentation/isdn/README.HiSax.
1262
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001263 hlt [BUGS=ARM,SH]
1264
1265 hpet= [X86-32,HPET] option to control HPET usage
1266 Format: { enable (default) | disable | force |
1267 verbose }
1268 disable: disable HPET and use PIT instead
1269 force: allow force enabled of undocumented chips (ICH4,
1270 VIA, nVidia)
1271 verbose: show contents of HPET registers during setup
1272
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001273 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1274 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1275
Andi Kleenb4718e62008-07-23 21:27:51 -07001276 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1277 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001278 On x86-64 and powerpc, this option can be specified
1279 multiple times interleaved with hugepages= to reserve
1280 huge pages of different sizes. Valid pages sizes on
1281 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001282 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001283
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001284 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1285 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001286 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1287 If specified, z/VM IUCV HVC accepts connections
1288 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001289
James Hoganfdabf522012-10-09 11:00:27 +01001290 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1291 hardware thread id mappings.
1292 Format: <cpu>:<hwthread>
1293
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001294 keep_bootcon [KNL]
1295 Do not unregister boot console at start. This is only
1296 useful for debugging when something happens in the window
1297 between unregistering the boot console and initializing
1298 the real console.
1299
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001300 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001301 or register an additional I2C bus that is not
1302 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001303 Format:
1304 <bus_id>,<clkrate>
1305
Jiri Kosina36d95732008-10-06 02:51:09 -04001306 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001307 i8042.unmask_kbd_data
1308 [HW] Enable printing of interrupt data from the KBD port
1309 (disabled by default, and as a pre-condition
1310 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001312 i8042.dumbkbd [HW] Pretend that controller can only read data from
1313 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314 (Don't attempt to blink the leds)
1315 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001316 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001317 i8042.noloop [HW] Disable the AUX Loopback command while probing
1318 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001320 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1322 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001323 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e19242016-10-01 12:07:35 -07001324 i8042.reset [HW] Reset the controller during init, cleanup and
1325 suspend-to-ram transitions, only during s2r
1326 transitions, or never reset
1327 Format: { 1 | Y | y | 0 | N | n }
1328 1, Y, y: always reset controller
1329 0, N, n: don't ever reset controller
1330 Default: only on s2r transitions on x86; most other
1331 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001333 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334
1335 i810= [HW,DRM]
1336
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001337 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1338 indicates that the driver is running on unsupported
1339 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1341 does not match list of supported models.
1342 i8k.power_status
1343 [HW] Report power status in /proc/i8k
1344 (disabled by default)
1345 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1346 capability is set.
1347
Carsten Emde4dca20e2012-03-15 15:56:26 +01001348 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001349 [DRM] Invert the sense of the variable that is used to
1350 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001351 brightness value of 0 indicates backlight switched off,
1352 and the maximum of the brightness value sets the backlight
1353 to maximum brightness. If this parameter is set to 0
1354 (default) and the machine requires it, or this parameter
1355 is set to 1, a brightness value of 0 sets the backlight
1356 to maximum brightness, and the maximum of the brightness
1357 value switches the backlight off.
1358 -1 -- never invert brightness
1359 0 -- machine default
1360 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001361
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362 icn= [HW,ISDN]
1363 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1364
David Fries0af80c02009-02-25 20:28:21 +01001365 ide-core.nodma= [HW] (E)IDE subsystem
1366 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001367 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1368 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001369 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001371 ide-generic.probe-mask= [HW] (E)IDE subsystem
1372 Format: <int>
1373 Probe mask for legacy ISA IDE ports. Depending on
1374 platform up to 6 ports are supported, enabled by
1375 setting corresponding bits in the mask to 1. The
1376 default value is 0x0, which has a special meaning.
1377 On systems that have PCI, it triggers scanning the
1378 PCI bus for the first and the second port, which
1379 are then probed. On systems without PCI the value
1380 of 0x0 enables probing the two first ports as if it
1381 was 0x3.
1382
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001383 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1384 Claim all unknown PCI IDE storage controllers.
1385
Andi Kleenf039b752007-05-02 19:27:12 +02001386 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001387 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001388 Poll forces a polling idle loop that can slightly
1389 improve the performance of waking up a idle CPU, but
1390 will use a lot of power and make the system run hot.
1391 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001392 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001393 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001394 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001395
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001396 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1397 Format: { strict | legacy | 2008 | relaxed }
1398 Default: strict
1399
1400 Choose which programs will be accepted for execution
1401 based on the IEEE 754 NaN encoding(s) supported by
1402 the FPU and the NaN encoding requested with the value
1403 of an ELF file header flag individually set by each
1404 binary. Hardware implementations are permitted to
1405 support either or both of the legacy and the 2008 NaN
1406 encoding mode.
1407
1408 Available settings are as follows:
1409 strict accept binaries that request a NaN encoding
1410 supported by the FPU
1411 legacy only accept legacy-NaN binaries, if supported
1412 by the FPU
1413 2008 only accept 2008-NaN binaries, if supported
1414 by the FPU
1415 relaxed accept any binaries regardless of whether
1416 supported by the FPU
1417
1418 The FPU emulator is always able to support both NaN
1419 encodings, so if no FPU hardware is present or it has
1420 been disabled with 'nofpu', then the settings of
1421 'legacy' and '2008' strap the emulator accordingly,
1422 'relaxed' straps the emulator for both legacy-NaN and
1423 2008-NaN, whereas 'strict' enables legacy-NaN only on
1424 legacy processors and both NaN encodings on MIPS32 or
1425 MIPS64 CPUs.
1426
1427 The setting for ABS.fmt/NEG.fmt instruction execution
1428 mode generally follows that for the NaN encoding,
1429 except where unsupported by hardware.
1430
Ingo Molnar792908222006-12-06 20:40:51 -08001431 ignore_loglevel [KNL]
1432 Ignore loglevel setting - this will print /all/
1433 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001434 We also add it as printk module parameter, so users
1435 could change it dynamically, usually by
1436 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001437
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001438 ignore_rlimit_data
1439 Ignore RLIMIT_DATA setting for data mappings,
1440 print warning at first misuse. Can be changed via
1441 /sys/module/kernel/parameters/ignore_rlimit_data.
1442
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 ihash_entries= [KNL]
1444 Set number of hash buckets for inode cache.
1445
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001446 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001447 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001448 default: "enforce"
1449
Mimi Zohar07f6a792011-03-09 22:25:48 -05001450 ima_appraise_tcb [IMA]
1451 The builtin appraise policy appraises all files
1452 owned by uid=0.
1453
Mimi Zohard68a6fe2016-12-19 16:22:57 -08001454 ima_canonical_fmt [IMA]
1455 Use the canonical format for the binary runtime
1456 measurements, instead of host native format.
1457
Mimi Zohar3323eec2009-02-04 09:06:58 -05001458 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001459 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1460 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001461 default: "sha1"
1462
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001463 The list of supported hash algorithms is defined
1464 in crypto/hash_info.h.
1465
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001466 ima_policy= [IMA]
1467 The builtin measurement policy to load during IMA
1468 setup. Specyfing "tcb" as the value, measures all
1469 programs exec'd, files mmap'd for exec, and all files
1470 opened with the read mode bit set by either the
1471 effective uid (euid=0) or uid=0.
1472 Format: "tcb"
1473
1474 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001475 Load a policy which meets the needs of the Trusted
1476 Computing Base. This means IMA will measure all
1477 programs exec'd, files mmap'd for exec, and all files
1478 opened for read by uid=0.
1479
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001480 ima_template= [IMA]
1481 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001482 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001483 Default: "ima-ng"
1484
Roberto Sassuc2426d22014-10-13 14:08:42 +02001485 ima_template_fmt=
1486 [IMA] Define a custom template format.
1487 Format: { "field1|...|fieldN" }
1488
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001489 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1490 Format: <min_file_size>
1491 Set the minimal file size for using asynchronous hash.
1492 If left unspecified, ahash usage is disabled.
1493
1494 ahash performance varies for different data sizes on
1495 different crypto accelerators. This option can be used
1496 to achieve the best performance for a particular HW.
1497
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001498 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1499 Format: <bufsize>
1500 Set hashing buffer size. Default: 4k.
1501
1502 ahash performance varies for different chunk sizes on
1503 different crypto accelerators. This option can be used
1504 to achieve best performance for particular HW.
1505
Linus Torvalds1da177e2005-04-16 15:20:36 -07001506 init= [KNL]
1507 Format: <full_path>
1508 Run specified binary instead of /sbin/init as init
1509 process.
1510
1511 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1512 for working out where the kernel is dying during
1513 startup.
1514
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001515 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1516 initcall functions. Useful for debugging built-in
1517 modules and initcalls.
1518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 initrd= [BOOT] Specify the location of the initial ramdisk
1520
Dave Hansenacd547b2016-07-29 09:30:21 -07001521 init_pkru= [x86] Specify the default memory protection keys rights
1522 register contents for all processes. 0x55555554 by
1523 default (disallow access to all but pkey 0). Can
1524 override in debugfs after boot.
1525
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1527 Format: <irq>
1528
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001529 int_pln_enable [x86] Enable power limit notification interrupt
1530
Mimi Zohard726d8d2013-03-18 14:48:02 -04001531 integrity_audit=[IMA]
1532 Format: { "0" | "1" }
1533 0 -- basic integrity auditing messages. (Default)
1534 1 -- additional integrity auditing messages.
1535
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001536 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001537 on
1538 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001539 off
1540 Disable intel iommu driver.
1541 igfx_off [Default Off]
1542 By default, gfx is mapped as normal device. If a gfx
1543 device has a dedicated DMAR unit, the DMAR unit is
1544 bypassed by not enabling DMAR with this option. In
1545 this case, gfx device will use physical address for
1546 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001547 forcedac [x86_64]
1548 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001549 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001550 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001551 than 32-bit addressing. The default is to look
1552 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001553 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001554 strict [Default Off]
1555 With this option on every unmap_single operation will
1556 result in a hardware IOTLB flush operation as opposed
1557 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001558 sp_off [Default Off]
1559 By default, super page will be supported if Intel IOMMU
1560 has the capability. With this option, super page will
1561 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001562 ecs_off [Default Off]
1563 By default, extended context tables will be supported if
1564 the hardware advertises that it has support both for the
1565 extended tables themselves, and also PASID support. With
1566 this option set, extended tables will not be used even
1567 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001568
1569 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1570 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001571 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001572
Dirk Brandewie6be26492013-02-15 22:55:10 +01001573 intel_pstate= [X86]
1574 disable
1575 Do not enable intel_pstate as the default
1576 scaling driver for the supported processors
Rafael J. Wysocki001c76f2016-11-17 23:34:17 +01001577 passive
1578 Use intel_pstate as a scaling driver, but configure it
1579 to work with generic cpufreq governors (instead of
1580 enabling its internal governor). This mode cannot be
1581 used along with the hardware-managed P-states (HWP)
1582 feature.
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001583 force
1584 Enable intel_pstate on systems that prohibit it by default
1585 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1586 instead of acpi-cpufreq may disable platform features, such
1587 as thermal controls and power capping, that rely on ACPI
1588 P-States information being indicated to OSPM and therefore
1589 should be used with caution. This option does not work with
1590 processors that aren't supported by the intel_pstate driver
1591 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001592 no_hwp
1593 Do not enable hardware P state control (HWP)
1594 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001595 hwp_only
1596 Only load intel_pstate on systems which support
1597 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001598 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001599 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1600 Description Table, specifies preferred power management
1601 profile as "Enterprise Server" or "Performance Server",
1602 then this feature is turned on by default.
Srinivas Pandruvada22449c02016-10-25 13:20:43 -07001603 per_cpu_perf_limits
1604 Allow per-logical-CPU P-State performance control limits using
1605 cpufreq sysfs interface
Dirk Brandewie6be26492013-02-15 22:55:10 +01001606
Chris Wrightd1423d52010-07-20 11:06:49 -07001607 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001608 on enable Interrupt Remapping (default)
1609 off disable Interrupt Remapping
1610 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001611 no_x2apic_optout
1612 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001613 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001614
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001615 iomem= Disable strict checking of access to MMIO memory
1616 strict regions from userspace.
1617 relaxed
1618
1619 iommu= [x86]
1620 off
1621 force
1622 noforce
1623 biomerge
1624 panic
1625 nopanic
1626 merge
1627 nomerge
1628 forcesac
1629 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001630 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001631 nobypass [PPC/POWERNV]
1632 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001633
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001634
1635 io7= [HW] IO7 for Marvel based alpha systems
1636 See comment before marvel_specify_io7 in
1637 arch/alpha/kernel/core_marvel.c.
1638
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301639 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001640 0x80
1641 Standard port 0x80 based delay
1642 0xed
1643 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001644 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001645 Simple two microseconds delay
1646 none
1647 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001648
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001650 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001652 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001653 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001654
Alan Cox200803d2005-06-28 20:45:18 -07001655 irqfixup [HW]
1656 When an interrupt is not handled search all handlers
1657 for it. Intended to get systems with badly broken
1658 firmware running.
1659
1660 irqpoll [HW]
1661 When an interrupt is not handled search all handlers
1662 for it. Also check all handlers each timer
1663 interrupt. Intended to get systems with badly broken
1664 firmware running.
1665
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001667 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668
1669 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001670 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001671
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672 This option can be used to specify one or more CPUs
1673 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001674 algorithms. You can move a process onto or off an
1675 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 <cpu number> begins at 0 and the maximum value is
1677 "number of CPUs in system - 1".
1678
1679 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001680 alternative -- manually setting the CPU mask of all
1681 tasks in the system -- can cause problems and
1682 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683
Randy Dunlapa9913042005-10-23 12:57:11 -07001684 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001685
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001686 ivrs_ioapic [HW,X86_64]
1687 Provide an override to the IOAPIC-ID<->DEVICE-ID
1688 mapping provided in the IVRS ACPI table. For
1689 example, to map IOAPIC-ID decimal 10 to
1690 PCI device 00:14.0 write the parameter as:
1691 ivrs_ioapic[10]=00:14.0
1692
1693 ivrs_hpet [HW,X86_64]
1694 Provide an override to the HPET-ID<->DEVICE-ID
1695 mapping provided in the IVRS ACPI table. For
1696 example, to map HPET-ID decimal 0 to
1697 PCI device 00:14.0 write the parameter as:
1698 ivrs_hpet[0]=00:14.0
1699
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001700 ivrs_acpihid [HW,X86_64]
1701 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1702 mapping provided in the IVRS ACPI table. For
1703 example, to map UART-HID:UID AMD0020:0 to
1704 PCI device 00:14.5 write the parameter as:
1705 ivrs_acpihid[00:14.5]=AMD0020:0
1706
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 js= [HW,JOY] Analog joystick
1708 See Documentation/input/joystick.txt.
1709
Kees Cook65fe9352016-06-13 15:10:02 -07001710 nokaslr [KNL]
1711 When CONFIG_RANDOMIZE_BASE is set, this disables
1712 kernel and module base offset ASLR (Address Space
1713 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001714
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001715 keepinitrd [HW,ARM]
1716
Taku Izumi342332e2016-03-15 14:55:22 -07001717 kernelcore= [KNL,X86,IA-64,PPC]
1718 Format: nn[KMGTPE] | "mirror"
1719 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001720 specifies the amount of memory usable by the kernel
1721 for non-movable allocations. The requested amount is
1722 spread evenly throughout all nodes in the system. The
1723 remaining memory in each node is used for Movable
1724 pages. In the event, a node is too small to have both
1725 kernelcore and Movable pages, kernelcore pages will
1726 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001727 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001728 allocation of pages that may be reclaimed or moved
1729 by the page migration subsystem. This means that
1730 HugeTLB pages may not be allocated from this zone.
1731 Note that allocations like PTEs-from-HighMem still
1732 use the HighMem zone if it exists, and the Normal
1733 zone if it does not.
1734
Taku Izumi342332e2016-03-15 14:55:22 -07001735 Instead of specifying the amount of memory (nn[KMGTPE]),
1736 you can specify "mirror" option. In case "mirror"
1737 option is specified, mirrored (reliable) memory is used
1738 for non-movable allocations and remaining memory is used
1739 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1740 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1741 time.
1742
Jason Wessel4fe1da42010-05-20 21:04:31 -05001743 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1744 Format: <Controller#>[,poll interval]
1745 The controller # is the number of the ehci usb debug
1746 port as it is probed via PCI. The poll interval is
1747 optional and is the number seconds in between
1748 each poll cycle to the debug port in case you need
1749 the functionality for interrupting the kernel with
1750 gdb or control-c on the dbgp connection. When
1751 not using this parameter you use sysrq-g to break into
1752 the kernel debugger.
1753
Jason Wessel84c08fd2010-05-20 21:04:24 -05001754 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001755 Requires a tty driver that supports console polling,
1756 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001757 Serial only format: <serial_device>[,baud]
1758 keyboard only format: kbd
1759 keyboard and serial format: kbd,<serial_device>[,baud]
1760 Optional Kernel mode setting:
1761 kms, kbd format: kms,kbd
1762 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001763
Jason Wessel84c08fd2010-05-20 21:04:24 -05001764 kgdbwait [KGDB] Stop kernel execution and enter the
1765 kernel debugger at the earliest opportunity.
1766
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001767 kmac= [MIPS] korina ethernet MAC address.
1768 Configure the RouterBoard 532 series on-chip
1769 Ethernet adapter MAC address.
1770
Catalin Marinas04f70332009-06-11 13:22:39 +01001771 kmemleak= [KNL] Boot-time kmemleak enable/disable
1772 Valid arguments: on, off
1773 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001774 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1775 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001776
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001777 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1778 Valid arguments: 0, 1, 2
1779 kmemcheck=0 (disabled)
1780 kmemcheck=1 (enabled)
1781 kmemcheck=2 (one-shot mode)
1782 Default: 2 (one-shot mode)
1783
Andre Przywarafef07aa2009-07-10 14:20:35 +02001784 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1785 Default is 0 (don't ignore, but inject #GP)
1786
Xiao Guangronga182d872010-09-20 22:17:48 +08001787 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1788 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001789 Default is 0 (off)
1790
Andre Przywarafef07aa2009-07-10 14:20:35 +02001791 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001792 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001793
1794 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1795 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001796 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001797
Andre Przywarafef07aa2009-07-10 14:20:35 +02001798 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1799 (virtualized MMU) support on capable Intel chips.
1800 Default is 1 (enabled)
1801
1802 kvm-intel.emulate_invalid_guest_state=
1803 [KVM,Intel] Enable emulation of invalid guest states
1804 Default is 0 (disabled)
1805
1806 kvm-intel.flexpriority=
1807 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1808 Default is 1 (enabled)
1809
Sasha Levine1a72ae2011-08-09 14:28:35 +03001810 kvm-intel.nested=
1811 [KVM,Intel] Enable VMX nesting (nVMX).
1812 Default is 0 (disabled)
1813
Andre Przywarafef07aa2009-07-10 14:20:35 +02001814 kvm-intel.unrestricted_guest=
1815 [KVM,Intel] Disable unrestricted guest feature
1816 (virtualized real and unpaged mode) on capable
1817 Intel chips. Default is 1 (enabled)
1818
1819 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1820 feature (tagged TLBs) on capable Intel chips.
1821 Default is 1 (enabled)
1822
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 l2cr= [PPC]
1824
Robert Brosea78bfbf2008-03-29 07:20:23 +11001825 l3cr= [PPC]
1826
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001827 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001828 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001829
Suresh Siddha279f1462012-10-22 14:37:58 -07001830 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1831 value for LAPIC timer one-shot implementation. Default
1832 back to the programmable timer unit in the LAPIC.
1833
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301834 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001835 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001836
FD Camifcb71f62008-01-06 19:08:56 +01001837 libata.dma= [LIBATA] DMA control
1838 libata.dma=0 Disable all PATA and SATA DMA
1839 libata.dma=1 PATA and SATA Disk DMA only
1840 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001841 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001842 Combinations also work, so libata.dma=3 enables DMA
1843 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001844
Michael Prokop20308872009-08-06 00:14:10 +02001845 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1846 libata.ignore_hpa=0 keep BIOS limits (default)
1847 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001848
Dave Jones78e70c22007-09-27 11:50:13 -04001849 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1850 when set.
1851 Format: <int>
1852
Tejun Heo33267322008-02-13 09:15:09 +09001853 libata.force= [LIBATA] Force configurations. The format is comma
1854 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001855 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001856 matching port, link or device. Basically, it matches
1857 the ATA ID string printed on console by libata. If
1858 the whole ID part is omitted, the last PORT and DEVICE
1859 values are used. If ID hasn't been specified yet, the
1860 configuration applies to all ports, links and devices.
1861
1862 If only DEVICE is omitted, the parameter applies to
1863 the port and all links and devices behind it. DEVICE
1864 number of 0 either selects the first device or the
1865 first fan-out link behind PMP device. It does not
1866 select the host link. DEVICE number of 15 selects the
1867 host link and device attached to it.
1868
1869 The VAL specifies the configuration to force. As long
1870 as there's no ambiguity shortcut notation is allowed.
1871 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1872 The following configurations can be forced.
1873
1874 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1875 Any ID with matching PORT is used.
1876
1877 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1878
1879 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1880 udma[/][16,25,33,44,66,100,133] notation is also
1881 allowed.
1882
1883 * [no]ncq: Turn on or off NCQ.
1884
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001885 * [no]ncqtrim: Turn off queued DSM TRIM.
1886
Tejun Heo05944bd2008-08-13 20:19:09 +09001887 * nohrst, nosrst, norst: suppress hard, soft
1888 and both resets.
1889
Dan Williamsca6d43b2012-06-21 23:41:41 -07001890 * rstonce: only attempt one reset during
1891 hot-unplug link recovery
1892
Tejun Heo43c9c592010-05-23 12:59:11 +02001893 * dump_id: dump IDENTIFY data.
1894
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001895 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1896
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001897 * disable: Disable this device.
1898
Tejun Heo33267322008-02-13 09:15:09 +09001899 If there are multiple matching configurations changing
1900 the same attribute, the last one is used.
1901
Yinghai Lu95f72d12010-07-12 14:36:09 +10001902 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001903
Linus Torvalds1da177e2005-04-16 15:20:36 -07001904 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001905 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001906
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001907 lockd.nlm_grace_period=P [NFS] Assign grace period.
1908 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001909
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001910 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1911 Format: <integer>
1912
1913 lockd.nlm_timeout=T [NFS] Assign timeout value.
1914 Format: <integer>
1915
1916 lockd.nlm_udpport=M [NFS] Assign UDP port.
1917 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001918
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001919 locktorture.nreaders_stress= [KNL]
1920 Set the number of locking read-acquisition kthreads.
1921 Defaults to being automatically set based on the
1922 number of online CPUs.
1923
1924 locktorture.nwriters_stress= [KNL]
1925 Set the number of locking write-acquisition kthreads.
1926
1927 locktorture.onoff_holdoff= [KNL]
1928 Set time (s) after boot for CPU-hotplug testing.
1929
1930 locktorture.onoff_interval= [KNL]
1931 Set time (s) between CPU-hotplug operations, or
1932 zero to disable CPU-hotplug testing.
1933
1934 locktorture.shuffle_interval= [KNL]
1935 Set task-shuffle interval (jiffies). Shuffling
1936 tasks allows some CPUs to go into dyntick-idle
1937 mode during the locktorture test.
1938
1939 locktorture.shutdown_secs= [KNL]
1940 Set time (s) after boot system shutdown. This
1941 is useful for hands-off automated testing.
1942
1943 locktorture.stat_interval= [KNL]
1944 Time (s) between statistics printk()s.
1945
1946 locktorture.stutter= [KNL]
1947 Time (s) to stutter testing, for example,
1948 specifying five seconds causes the test to run for
1949 five seconds, wait for five seconds, and so on.
1950 This tests the locking primitive's ability to
1951 transition abruptly to and from idle.
1952
1953 locktorture.torture_runnable= [BOOT]
1954 Start locktorture running at boot time.
1955
1956 locktorture.torture_type= [KNL]
1957 Specify the locking implementation to test.
1958
1959 locktorture.verbose= [KNL]
1960 Enable additional printk() statements.
1961
Linus Torvalds1da177e2005-04-16 15:20:36 -07001962 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1963 Format: <irq>
1964
1965 loglevel= All Kernel Messages with a loglevel smaller than the
1966 console loglevel will be printed to the console. It can
1967 also be changed with klogd or other programs. The
1968 loglevels are defined as follows:
1969
1970 0 (KERN_EMERG) system is unusable
1971 1 (KERN_ALERT) action must be taken immediately
1972 2 (KERN_CRIT) critical conditions
1973 3 (KERN_ERR) error conditions
1974 4 (KERN_WARNING) warning conditions
1975 5 (KERN_NOTICE) normal but significant condition
1976 6 (KERN_INFO) informational
1977 7 (KERN_DEBUG) debug-level messages
1978
Randy Dunlapc756d082011-02-20 20:08:35 -08001979 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001980 in bytes. n must be a power of two and greater
1981 than the minimal size. The minimal size is defined
1982 by LOG_BUF_SHIFT kernel config parameter. There is
1983 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1984 that allows to increase the default size depending on
1985 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001986
Randy Dunlapaccaa242007-10-16 01:29:37 -07001987 logo.nologo [FB] Disables display of the built-in Linux logo.
1988 This may be used to provide more screen space for
1989 kernel log messages and is useful when debugging
1990 kernel boot problems.
1991
Linus Torvalds1da177e2005-04-16 15:20:36 -07001992 lp=0 [LP] Specify parallel ports to use, e.g,
1993 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1994 lp=reset first parallel port). 'lp=0' disables the
1995 lp=auto printer driver. 'lp=reset' (which can be
1996 specified in addition to the ports) causes
1997 attached printers to be reset. Using
1998 lp=port1,port2,... specifies the parallel ports
1999 to associate lp devices with, starting with
2000 lp0. A port specification may be 'none' to skip
2001 that lp device, or a parport name such as
2002 'parport0'. Specifying 'lp=auto' instead of a
2003 port specification list means that device IDs
2004 from each port should be examined, to see if
2005 an IEEE 1284-compliant printer is attached; if
2006 so, the driver will manage that printer.
2007 See also header of drivers/char/lp.c.
2008
2009 lpj=n [KNL]
2010 Sets loops_per_jiffy to given constant, thus avoiding
2011 time-consuming boot-time autodetection (up to 250 ms per
2012 CPU). 0 enables autodetection (default). To determine
2013 the correct value for your kernel, boot with normal
2014 autodetection and see what value is printed. Note that
2015 on SMP systems the preset will be applied to all CPUs,
2016 which is likely to cause problems if your CPUs need
2017 significantly divergent settings. An incorrect value
2018 will cause delays in the kernel to be wrong, leading to
2019 unpredictable I/O errors and other breakage. Although
2020 unlikely, in the extreme case this might damage your
2021 hardware.
2022
2023 ltpc= [NET]
2024 Format: <io>,<irq>,<dma>
2025
Randy Dunlap16290242011-08-13 12:34:52 -07002026 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002027 (machvec) in a generic kernel.
2028 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029
Wu Zhangjin3209e702009-07-02 23:27:12 +08002030 machtype= [Loongson] Share the same kernel image file between different
2031 yeeloong laptop.
2032 Example: machtype=lemote-yeeloong-2f-7inch
2033
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002034 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2035 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002036
2037 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002038 will bring up during bootup. maxcpus=n : n >= 0 limits
2039 the kernel to bring up 'n' processors. Surely after
2040 bootup you can bring up the other plugged cpu by executing
2041 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2042 only takes effect during system bootup.
2043 While n=0 is a special case, it is equivalent to "nosmp",
2044 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045
Kay Sieversd134b002011-07-31 22:08:04 +02002046 max_loop= [LOOP] The number of loop block devices that get
2047 (loop.max_loop) unconditionally pre-created at init time. The default
2048 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2049 of statically allocating a predefined number, loop
2050 devices can be requested on-demand with the
2051 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002052
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002053 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002054
Uwe Hermann71cced62008-10-20 09:32:21 -07002055 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002056
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057 md= [HW] RAID subsystems devices and level
Jani Nikulae52347b2016-11-03 12:10:10 +02002058 See Documentation/admin-guide/md.rst.
Randy Dunlapa9913042005-10-23 12:57:11 -07002059
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060 mdacon= [MDA]
2061 Format: <first>,<last>
2062 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002063
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2065 Amount of memory to be used when the kernel is not able
2066 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002067 [X86] Work as limiting max address. Use together
2068 with memmap= to avoid physical address space collisions.
2069 Without memmap= PCI devices could be placed at addresses
2070 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002071
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002072 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002073 memory.
2074
Paul Mundt6902aa82008-09-21 17:14:42 +09002075 memchunk=nn[KMG]
2076 [KNL,SH] Allow user to override the default size for
2077 per-device physically contiguous DMA buffers.
2078
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002079 memhp_default_state=online/offline
2080 [KNL] Set the initial state for the memory hotplug
2081 onlining policy. If not specified, the default value is
2082 set according to the
2083 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2084 option.
2085 See Documentation/memory-hotplug.txt.
2086
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302087 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088 E820 memory map, as specified by the user.
2089 Such memmap=exactmap lines can be constructed based on
2090 BIOS output or other requirements. See the memmap=nn@ss
2091 option description.
2092
2093 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002094 [KNL] Force usage of a specific region of memory.
2095 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096
2097 memmap=nn[KMG]#ss[KMG]
2098 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002099 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100
2101 memmap=nn[KMG]$ss[KMG]
2102 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002103 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002104 Example: Exclude memory from 0x18690000-0x1869ffff
2105 memmap=64K$0x18690000
2106 or
2107 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002109 memmap=nn[KMG]!ss[KMG]
2110 [KNL,X86] Mark specific memory as protected.
2111 Region of memory to be used, from ss to ss+nn.
2112 The memory region may be marked as e820 type 12 (0xc)
2113 and is NVDIMM or ADR memory.
2114
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002115 memory_corruption_check=0/1 [X86]
2116 Some BIOSes seem to corrupt the first 64k of
2117 memory when doing things like suspend/resume.
2118 Setting this option will scan the memory
2119 looking for corruption. Enabling this will
2120 both detect corruption and prevent the kernel
2121 from using the memory being corrupted.
2122 However, its intended as a diagnostic tool; if
2123 repeatable BIOS-originated corruption always
2124 affects the same memory, you can use memmap=
2125 to prevent the kernel from using that memory.
2126
2127 memory_corruption_check_size=size [X86]
2128 By default it checks for corruption in the low
2129 64k, making this memory unavailable for normal
2130 use. Use this parameter to scan for
2131 corruption in more or less memory.
2132
2133 memory_corruption_check_period=seconds [X86]
2134 By default it checks for corruption every 60
2135 seconds. Use this parameter to check at some
2136 other rate. 0 disables periodic checking.
2137
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002138 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002139 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002140 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002141 Specifies the number of memtest passes to be
2142 performed. Each pass selects another test
2143 pattern from a given set of patterns. Memtest
2144 fills the memory with this pattern, validates
2145 memory contents and reserves bad memory
2146 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002147
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002148 mem_sleep_default= [SUSPEND] Default system suspend mode:
2149 s2idle - Suspend-To-Idle
2150 shallow - Power-On Suspend or equivalent (if supported)
2151 deep - Suspend-To-RAM or equivalent (if supported)
2152 See Documentation/power/states.txt.
2153
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154 meye.*= [HW] Set MotionEye Camera parameters
2155 See Documentation/video4linux/meye.txt.
2156
Andres Salomon8f368812007-10-12 23:04:06 +02002157 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2158 Multi-Function General Purpose Timers on AMD Geode
2159 platforms.
2160
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002161 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2162 the BIOS has incorrectly applied a workaround. TinyBIOS
2163 version 0.98 is known to be affected, 0.99 fixes the
2164 problem by letting the user disable the workaround.
2165
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166 mga= [HW,DRM]
2167
Randy Dunlap1c207f952008-11-19 15:36:16 -08002168 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2169 physical address is ignored.
2170
Michel Pollet39f45d72009-05-20 11:10:31 +01002171 mini2440= [ARM,HW,KNL]
2172 Format:[0..2][b][c][t]
2173 Default: "0tb"
2174 MINI2440 configuration specification:
2175 0 - The attached screen is the 3.5" TFT
2176 1 - The attached screen is the 7" TFT
2177 2 - The VGA Shield is attached (1024x768)
2178 Leaving out the screen size parameter will not load
2179 the TFT driver, and the framebuffer will be left
2180 unconfigured.
2181 b - Enable backlight. The TFT backlight pin will be
2182 linked to the kernel VESA blanking code and a GPIO
2183 LED. This parameter is not necessary when using the
2184 VGA shield.
2185 c - Enable the s3c camera interface.
2186 t - Reserved for enabling touchscreen support. The
2187 touchscreen support is not enabled in the mainstream
2188 kernel as of 2.6.30, a preliminary port can be found
2189 in the "bleeding edge" mini2440 support kernel at
2190 http://repo.or.cz/w/linux-2.6/mini2440.git
2191
Mel Gorman6b74ab92008-07-23 21:26:49 -07002192 mminit_loglevel=
2193 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2194 parameter allows control of the logging verbosity for
2195 the additional memory initialisation checks. A value
2196 of 0 disables mminit logging and a level of 4 will
2197 log everything. Information is printed at KERN_DEBUG
2198 so loglevel=8 may also need to be specified.
2199
Rusty Russell106a4ee2012-09-26 10:09:40 +01002200 module.sig_enforce
2201 [KNL] When CONFIG_MODULE_SIG is set, this means that
2202 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002203 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002204 is always true, so this option does nothing.
2205
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302206 module_blacklist= [KNL] Do not load a comma-separated list of
2207 modules. Useful for debugging problem modules.
2208
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 mousedev.tap_time=
2210 [MOUSE] Maximum time between finger touching and
2211 leaving touchpad surface for touch to be considered
2212 a tap and be reported as a left button click (for
2213 touchpads working in absolute mode only).
2214 Format: <msecs>
2215 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2216 reporting absolute coordinates, such as tablets
2217 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2218 reporting absolute coordinates, such as tablets
2219
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302220 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002221 is similar to kernelcore except it specifies the
2222 amount of memory used for migratable allocations.
2223 If both kernelcore and movablecore is specified,
2224 then kernelcore will be at *least* the specified
2225 value but may be more. If movablecore on its own
2226 is specified, the administrator must be careful
2227 that the amount of memory usable for all allocations
2228 is not too small.
2229
Reza Arbab39fa104d2016-12-12 16:42:55 -08002230 movable_node [KNL] Boot-time switch to enable the effects
Tang Chenc5320922013-11-12 15:08:10 -08002231 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2232
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233 MTD_Partition= [MTD]
2234 Format: <name>,<region-number>,<size>,<offset>
2235
Randy Dunlapa9913042005-10-23 12:57:11 -07002236 MTD_Region= [MTD] Format:
2237 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238
2239 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002240 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002241
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002242 multitce=off [PPC] This parameter disables the use of the pSeries
2243 firmware feature for updating multiple TCE entries
2244 at a time.
2245
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002246 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2247
2248 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2249
2250 boundary - index of last SLC block on Flex-OneNAND.
2251 The remaining blocks are configured as MLC blocks.
2252 lock - Configure if Flex-OneNAND boundary should be locked.
2253 Once locked, the boundary cannot be changed.
2254 1 indicates lock status, 0 indicates unlock status.
2255
Ben Dooks9db829f2008-07-03 11:24:29 +01002256 mtdset= [ARM]
2257 ARM/S3C2412 JIVE boot control
2258
2259 See arch/arm/mach-s3c2412/mach-jive.c
2260
Linus Torvalds1da177e2005-04-16 15:20:36 -07002261 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002262 [HW] Make the MicroTouch USB driver use raw coordinates
2263 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002265 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002266 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002267 that could hold holes aka. UC entries.
2268
2269 mtrr_gran_size=nn[KMG] [X86]
2270 Used for mtrr cleanup. It is granularity of mtrr block.
2271 Default is 1.
2272 Large value could prevent small alignment from
2273 using up MTRRs.
2274
2275 mtrr_spare_reg_nr=n [X86]
2276 Format: <integer>
2277 Range: 0,7 : spare reg number
2278 Default : 1
2279 Used for mtrr cleanup. It is spare mtrr entries number.
2280 Set to 2 or more if your graphical card needs more.
2281
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2283
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284 netdev= [NET] Network devices parameters
2285 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2286 Note that mem_start is often overloaded to mean
2287 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002288 This usage is only documented in each driver source
2289 file if at all.
2290
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002291 nf_conntrack.acct=
2292 [NETFILTER] Enable connection tracking flow accounting
2293 0 to disable accounting
2294 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002295 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002296
Chuck Lever306a0752010-09-17 10:54:37 -04002297 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002298 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299
2300 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002301 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002302
Chuck Lever306a0752010-09-17 10:54:37 -04002303 nfsrootdebug [NFS] enable nfsroot debugging messages.
2304 See Documentation/filesystems/nfs/nfsroot.txt.
2305
Trond Myklebust5405fc42016-08-29 20:03:52 -04002306 nfs.callback_nr_threads=
2307 [NFSv4] set the total number of threads that the
2308 NFS client will assign to service NFSv4 callback
2309 requests.
2310
Trond Myklebusta72b4422006-01-03 09:55:41 +01002311 nfs.callback_tcpport=
2312 [NFS] set the TCP port on which the NFSv4 callback
2313 channel should listen.
2314
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002315 nfs.cache_getent=
2316 [NFS] sets the pathname to the program which is used
2317 to update the NFS client cache entries.
2318
2319 nfs.cache_getent_timeout=
2320 [NFS] sets the timeout after which an attempt to
2321 update a cache entry is deemed to have failed.
2322
Trond Myklebust58df0952006-01-03 09:55:57 +01002323 nfs.idmap_cache_timeout=
2324 [NFS] set the maximum lifetime for idmapper cache
2325 entries.
2326
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002327 nfs.enable_ino64=
2328 [NFS] enable 64-bit inode numbers.
2329 If zero, the NFS client will fake up a 32-bit inode
2330 number for the readdir() and stat() syscalls instead
2331 of returning the full 64-bit number.
2332 The default is to return 64-bit inode numbers.
2333
Trond Myklebust5405fc42016-08-29 20:03:52 -04002334 nfs.max_session_cb_slots=
2335 [NFSv4.1] Sets the maximum number of session
2336 slots the client will assign to the callback
2337 channel. This determines the maximum number of
2338 callbacks the client will process in parallel for
2339 a particular server.
2340
Trond Myklebustef159e92012-02-06 19:50:40 -05002341 nfs.max_session_slots=
2342 [NFSv4.1] Sets the maximum number of session slots
2343 the client will attempt to negotiate with the server.
2344 This limits the number of simultaneous RPC requests
2345 that the client can send to the NFSv4.1 server.
2346 Note that there is little point in setting this
2347 value higher than the max_tcp_slot_table_limit.
2348
Trond Myklebustb064eca22011-02-22 15:44:32 -08002349 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002350 [NFSv4] When set to the default of '1', this option
2351 ensures that both the RPC level authentication
2352 scheme and the NFS level operations agree to use
2353 numeric uids/gids if the mount is using the
2354 'sec=sys' security flavour. In effect it is
2355 disabling idmapping, which can make migration from
2356 legacy NFSv2/v3 systems to NFSv4 easier.
2357 Servers that do not support this mode of operation
2358 will be autodetected by the client, and it will fall
2359 back to using the idmapper.
2360 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002361 nfs.nfs4_unique_id=
2362 [NFS4] Specify an additional fixed unique ident-
2363 ification string that NFSv4 clients can insert into
2364 their nfs_client_id4 string. This is typically a
2365 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002366
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002367 nfs.send_implementation_id =
2368 [NFSv4.1] Send client implementation identification
2369 information in exchange_id requests.
2370 If zero, no implementation identification information
2371 will be sent.
2372 The default is to send the implementation identification
2373 information.
Jani Nikulae52347b2016-11-03 12:10:10 +02002374
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002375 nfs.recover_lost_locks =
2376 [NFSv4] Attempt to recover locks that were lost due
2377 to a lease timeout on the server. Please note that
2378 doing this risks data corruption, since there are
2379 no guarantees that the file will remain unchanged
2380 after the locks are lost.
2381 If you want to enable the kernel legacy behaviour of
2382 attempting to recover these locks, then set this
2383 parameter to '1'.
2384 The default parameter value of '0' causes the kernel
2385 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002386
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002387 nfs4.layoutstats_timer =
2388 [NFSv4.2] Change the rate at which the kernel sends
2389 layoutstats to the pNFS metadata server.
2390
2391 Setting this to value to 0 causes the kernel to use
2392 whatever value is the default set by the layout
2393 driver. A non-zero value sets the minimum interval
2394 in seconds between layoutstats transmissions.
2395
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002396 nfsd.nfs4_disable_idmapping=
2397 [NFSv4] When set to the default of '1', the NFSv4
2398 server will return only numeric uids and gids to
2399 clients using auth_sys, and will accept numeric uids
2400 and gids from such clients. This is intended to ease
2401 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002402
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002403 objlayoutdriver.osd_login_prog=
2404 [NFS] [OBJLAYOUT] sets the pathname to the program which
2405 is used to automatically discover and login into new
2406 osd-targets. Please see:
2407 Documentation/filesystems/pnfs.txt for more explanations
2408
Paul Mundt1e1030d2009-09-01 17:38:32 +09002409 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002410 when a NMI is triggered.
2411 Format: [state][,regs][,debounce][,die]
2412
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302413 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002414 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002415 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002416 0 - turn hardlockup detector in nmi_watchdog off
2417 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002418 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002419 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002420 default). To disable both hard and soft lockup detectors,
2421 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002422 This is useful when you use a panic=... timeout and
2423 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002424
Anton Vorontsovbff38772009-07-08 11:10:56 -07002425 netpoll.carrier_timeout=
2426 [NET] Specifies amount of time (in seconds) that
2427 netpoll should wait for a carrier. By default netpoll
2428 waits 4 seconds.
2429
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002430 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431 emulation library even if a 387 maths coprocessor
2432 is present.
2433
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002434 no_console_suspend
2435 [HW] Never suspend the console
2436 Disable suspending of consoles during suspend and
2437 hibernate operations. Once disabled, debugging
2438 messages can reach various consoles while the rest
2439 of the system is being put to sleep (ie, while
2440 debugging driver suspend/resume hooks). This may
2441 not work reliably with all consoles, but is known
2442 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002443 To facilitate more flexible debugging, we also add
2444 console_suspend, a printk module parameter to control
2445 it. Users could use console_suspend (usually
2446 /sys/module/printk/parameters/console_suspend) to
2447 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002448
Christoph Lameterc1aee212007-05-31 00:40:47 -07002449 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2450 caches in the slab allocator. Saves per-node memory,
2451 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002452
Randy Dunlapa9913042005-10-23 12:57:11 -07002453 noalign [KNL,ARM]
2454
Linus Torvalds1da177e2005-04-16 15:20:36 -07002455 noapic [SMP,APIC] Tells the kernel to not make use of any
2456 IOAPICs that may be present in the system.
2457
Mike Galbraith5091faa2010-11-30 14:18:03 +01002458 noautogroup Disable scheduler automatic task group creation.
2459
Linus Torvalds1da177e2005-04-16 15:20:36 -07002460 nobats [PPC] Do not use BATs for mapping kernel lowmem
2461 on "Classic" PPC cores.
2462
2463 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002464
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002465 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2466
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002467 nodelayacct [KNL] Disable per-task delay accounting
2468
Paul Mundt6902aa82008-09-21 17:14:42 +09002469 nodsp [SH] Disable hardware DSP at boot time.
2470
Dave Youngb2e0a542014-08-14 17:15:26 +08002471 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002472
Linus Torvalds1da177e2005-04-16 15:20:36 -07002473 noexec [IA-64]
2474
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302475 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002476 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002478 noexec=off: disable non-executable mappings
2479
H. Peter Anvin52b61792012-09-21 12:43:13 -07002480 nosmap [X86]
2481 Disable SMAP (Supervisor Mode Access Prevention)
2482 even if it is supported by processor.
2483
Fenghua Yude5397a2011-05-11 16:51:05 -07002484 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002485 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002486 even if it is supported by processor.
2487
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002488 noexec32 [X86-64]
2489 This affects only 32-bit executables.
2490 noexec32=on: enable non-executable mappings (default)
2491 read doesn't imply executable mappings
2492 noexec32=off: disable non-executable mappings
2493 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002494
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002495 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002496
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002497 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002498 register save and restore. The kernel will only save
2499 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002501 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2502
Sascha Silbe52c48c52016-04-05 12:53:38 +02002503 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2504 Equivalent to smt=1.
2505
Suresh Siddha0c752a92009-05-22 12:17:45 -07002506 noxsave [BUGS=X86] Disables x86 extended register state save
2507 and restore using xsave. The kernel will fallback to
2508 enabling legacy floating-point and sse state.
2509
Fenghua Yub6f42a42014-05-29 11:12:31 -07002510 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2511 register states. The kernel will fall back to use
2512 xsave to save the states. By using this parameter,
2513 performance of saving the states is degraded because
2514 xsave doesn't support modified optimization while
2515 xsaveopt supports it on xsaveopt enabled systems.
2516
2517 noxsaves [X86] Disables xsaves and xrstors used in saving and
2518 restoring x86 extended register state in compacted
2519 form of xsave area. The kernel will fall back to use
2520 xsaveopt and xrstor to save and restore the states
2521 in standard form of xsave area. By using this
2522 parameter, xsave area per process might occupy more
2523 memory on xsaves enabled systems.
2524
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002525 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2526 wfi(ARM) instruction doesn't work correctly and not to
2527 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002528
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002529 no_file_caps Tells the kernel not to honor file capabilities. The
2530 only way then for a file to be executed with privilege
2531 is to be setuid root or executed by root.
2532
Linus Torvalds1da177e2005-04-16 15:20:36 -07002533 nohalt [IA-64] Tells the kernel not to use the power saving
2534 function PAL_HALT_LIGHT when idle. This increases
2535 power-consumption. On the positive side, it reduces
2536 interrupt wake-up latency, which may improve performance
2537 in certain environments such as networked servers or
2538 real-time systems.
2539
Kees Cooka6e15a32014-06-13 13:30:35 -07002540 nohibernate [HIBERNATION] Disable hibernation and resume.
2541
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002542 nohz= [KNL] Boottime enable/disable dynamic ticks
2543 Valid arguments: on, off
2544 Default: on
2545
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002546 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002547 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002548 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002549 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002550 whenever possible. The boot CPU will be forced outside
2551 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002552 The CPUs in this range must also be included in the
2553 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002554
Paul Mundteeee7852009-04-02 12:31:16 +09002555 noiotrap [SH] Disables trapped I/O port accesses.
2556
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002557 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002558 disable unhandled interrupt sources.
2559
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302560 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002561 broken timer IRQ sources.
2562
Linus Torvalds1da177e2005-04-16 15:20:36 -07002563 noisapnp [ISAPNP] Disables ISA PnP code.
2564
2565 noinitrd [RAM] Tells the kernel not to load any configured
2566 initial RAM disk.
2567
Weidong Han03ea8152009-04-17 16:42:15 +08002568 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2569 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002570 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002571
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 nointroute [IA-64]
2573
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002574 noinvpcid [X86] Disable the INVPCID cpu feature.
2575
Randy Dunlap16290242011-08-13 12:34:52 -07002576 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002577
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002578 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2579
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002580 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2581 fault handling.
2582
Alexey Makhalov80e9a4f2016-10-28 00:54:32 -07002583 no-vmw-sched-clock
2584 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2585 clock and use the default one.
2586
Glauber Costad910f5c2011-07-11 15:28:19 -04002587 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2588 steal time is computed, but won't influence scheduler
2589 behaviour
2590
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002591 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002593 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002594
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002596 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002597
Horms312f1f02006-02-22 09:57:55 +09002598 nomca [IA-64] Disable machine check abort handling
2599
Masanari Iida13696e02015-05-16 02:16:43 +09002600 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002601
Andres Salomon83d73842007-10-12 23:04:06 +02002602 nomfgpt [X86-32] Disable Multi-Function General Purpose
2603 Timer usage (for AMD Geode machines).
2604
Don Zickusbda62632011-10-13 15:14:27 -04002605 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2606 shutdown the other cpus. Instead use the REBOOT_VECTOR
2607 irq.
2608
Dave Young02608be2012-02-01 10:33:14 +08002609 nomodule Disable module load
2610
Jiri Kosina016ddd92010-01-18 17:05:40 +01002611 nopat [X86] Disable PAT (page attribute table extension of
2612 pagetables) support.
2613
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002614 norandmaps Don't use address space randomization. Equivalent to
2615 echo 0 > /proc/sys/kernel/randomize_va_space
2616
Jiri Kosinabbff2162010-08-11 18:34:09 +02002617 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002618
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002619 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002620 with UP alternatives
2621
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002622 nordrand [X86] Disable kernel use of the RDRAND and
2623 RDSEED instructions even if they are supported
2624 by the processor. RDRAND and RDSEED are still
2625 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002626
Randy Dunlapa9913042005-10-23 12:57:11 -07002627 noresume [SWSUSP] Disables resume and restores original swap
2628 space.
2629
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630 no-scroll [VGA] Disables scrollback.
2631 This is required for the Braillex ib80-piezo Braille
2632 reader made by F.H. Papenmeier (Germany).
2633
2634 nosbagart [IA-64]
2635
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002636 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002637
Len Brown61ec7562007-08-16 03:34:22 -04002638 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2639 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002640
Dave Jones97842212007-07-15 23:41:05 -07002641 nosoftlockup [KNL] Disable the soft-lockup detector.
2642
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643 nosync [HW,M68K] Disables sync negotiation for all devices.
2644
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002645 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002646
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002647 nowatchdog [KNL] Disable both lockup detectors, i.e.
2648 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002649
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002651
Weidong Han2b2fd872009-04-17 16:42:12 +08002652 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2653
Fenghua Yuf78cff42012-11-13 11:32:38 -08002654 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2655 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2656 Some features depend on CPU0. Known dependencies are:
2657 1. Resume from suspend/hibernate depends on CPU0.
2658 Suspend/hibernate will fail if CPU0 is offline and you
2659 need to online CPU0 before suspend/hibernate.
2660 2. PIC interrupts also depend on CPU0. CPU0 can't be
2661 removed if a PIC interrupt is detected.
2662 It's said poweroff/reboot may depend on CPU0 on some
2663 machines although I haven't seen such issues so far
2664 after CPU0 is offline on a few tested machines.
2665 If the dependencies are under your control, you can
2666 turn on cpu0_hotplug.
2667
Randy Dunlap16290242011-08-13 12:34:52 -07002668 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002669 purges which is reported from either PAL_VM_SUMMARY or
2670 SAL PALO.
2671
Yinghai Lu2b633e32010-02-10 01:20:37 -08002672 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2673 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002674 support 'n' processors. It could be larger than the
2675 number of already plugged CPU during bootup, later in
2676 runtime you can physically add extra cpu until it reaches
2677 n. So during boot up some boot time memory for per-cpu
2678 variables need be pre-allocated for later physical cpu
2679 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002680
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002681 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2682
Mel Gorman1a687c22012-11-22 11:16:36 +00002683 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2684 Allowed values are enable and disable
2685
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002686 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2687 one of ['zone', 'node', 'default'] can be specified
2688 This can be set from sysctl after boot.
2689 See Documentation/sysctl/vm.txt for details.
2690
Randy Dunlap7c4be252009-01-06 14:42:44 -08002691 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2692 See Documentation/debugging-via-ohci1394.txt for more
2693 info.
2694
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002695 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2696 Rather than timing out after 20 ms if an EC
2697 command is not properly ACKed, override the length
2698 of the timeout. We have interrupts disabled while
2699 waiting for the ACK, so if this is set too high
2700 interrupts *may* be lost!
2701
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002702 omap_mux= [OMAP] Override bootloader pin multiplexing.
2703 Format: <mux_mode0.mode_name=value>...
2704 For example, to override I2C bus2:
2705 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2706
Linus Torvalds1da177e2005-04-16 15:20:36 -07002707 oprofile.timer= [HW]
2708 Use timer interrupt instead of performance counters
2709
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002710 oprofile.cpu_type= Force an oprofile cpu type
2711 This might be useful if you have an older oprofile
2712 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002713 Format: { arch_perfmon }
2714 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002715 perfmon on Intel CPUs instead of the
2716 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002717 timer: [X86] Force use of architectural NMI
2718 timer mode (see also oprofile.timer
2719 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002720
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002721 oops=panic Always panic on oopses. Default is to just kill the
2722 process, but there is a small probability of
2723 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002724 This will also cause panics on machine check exceptions.
2725 Useful together with panic=30 to trigger a reboot.
2726
Randy Dunlapbcfde332010-06-07 17:10:38 -07002727 OSS [HW,OSS]
2728 See Documentation/sound/oss/oss-parameters.txt
2729
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002730 page_owner= [KNL] Boot-time page_owner enabling option.
2731 Storage of the information about who allocated
2732 each page is disabled in default. With this switch,
2733 we can turn it on.
2734 on: enable the feature
2735
Laura Abbott8823b1d2016-03-15 14:56:27 -07002736 page_poison= [KNL] Boot-time parameter changing the state of
2737 poisoning on the buddy allocator.
2738 off: turn off poisoning
2739 on: turn on poisoning
2740
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002741 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002742 timeout > 0: seconds before rebooting
2743 timeout = 0: wait forever
2744 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002745 Format: <timeout>
2746
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002747 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2748 on a WARN().
2749
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002750 crash_kexec_post_notifiers
2751 Run kdump after running panic-notifiers and dumping
2752 kmsg. This only for the users who doubt kdump always
2753 succeeds in any situation.
2754 Note that this also increases risks of kdump failure,
2755 because some panic notifiers can make the crashed
2756 kernel more unstable.
2757
Linus Torvalds1da177e2005-04-16 15:20:36 -07002758 parkbd.port= [HW] Parallel port number the keyboard adapter is
2759 connected to, default is 0.
2760 Format: <parport#>
2761 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2762 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002763 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002764
Randy Dunlapa9913042005-10-23 12:57:11 -07002765 parport= [HW,PPT] Specify parallel ports. 0 disables.
2766 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2767 Use 'auto' to force the driver to use any
2768 IRQ/DMA settings detected (the default is to
2769 ignore detected IRQ/DMA settings because of
2770 possible conflicts). You can specify the base
2771 address, IRQ, and DMA settings; IRQ and DMA
2772 should be numbers, or 'auto' (for using detected
2773 settings on that particular port), or 'nofifo'
2774 (to avoid using a FIFO even if it is detected).
2775 Parallel ports are assigned in the order they
2776 are specified on the command line, starting
2777 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778
Randy Dunlapa9913042005-10-23 12:57:11 -07002779 parport_init_mode= [HW,PPT]
2780 Configure VIA parallel port to operate in
2781 a specific mode. This is necessary on Pegasos
2782 computer where firmware has no options for setting
2783 up parallel port mode and sets it to spp.
2784 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002785 Format: [spp|ps2|epp|ecp|ecpepp]
2786
Andrew Mortondd287792006-03-23 03:00:57 -08002787 pause_on_oops=
2788 Halt all CPUs after the first oops has been printed for
2789 the specified number of seconds. This is to be used if
2790 your oopses keep scrolling off the screen.
2791
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792 pcbit= [HW,ISDN]
2793
2794 pcd. [PARIDE]
2795 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002796 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002797
Randy Dunlapa9913042005-10-23 12:57:11 -07002798 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002799 earlydump [X86] dump PCI config space before the kernel
2800 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002801 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002802 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002803 the hardware directly. Use this if your machine
2804 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002805 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002806 hardware access methods are allowed. Use this
2807 if you experience crashes upon bootup and you
2808 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002809 conf1 [X86] Force use of PCI Configuration Access
2810 Mechanism 1 (config address in IO port 0xCF8,
2811 data in IO port 0xCFC, both 32-bit).
2812 conf2 [X86] Force use of PCI Configuration Access
2813 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2814 the function, IO port 0xCFA, also 8-bit, sets
2815 bus number. The config space is then accessed
2816 through ports 0xC000-0xCFFF).
2817 See http://wiki.osdev.org/PCI for more info
2818 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002819 noaer [PCIE] If the PCIEAER kernel config parameter is
2820 enabled, this kernel boot option can be used to
2821 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002822 nodomains [PCI] Disable support for multiple PCI
2823 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302824 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002825 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002826 check_enable_amd_mmconf [X86] check for and enable
2827 properly configured MMIO access to PCI
2828 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002829 nomsi [MSI] If the PCI_MSI kernel config parameter is
2830 enabled, this kernel boot option can be used to
2831 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002832 noioapicquirk [APIC] Disable all boot interrupt quirks.
2833 Safety option to keep boot IRQs enabled. This
2834 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002835 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2836 primary IO-APIC for bridges that cannot disable
2837 boot IRQs. This fixes a source of spurious IRQs
2838 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002839 noioapicreroute [APIC] Disable workaround that uses the
2840 boot IRQ equivalent of an IRQ that connects to
2841 a chipset where boot IRQs cannot be disabled.
2842 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002843 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002844 routing table. These calls are known to be buggy
2845 on several machines and they hang the machine
2846 when used, but on other computers it's the only
2847 way to get the interrupt routing table. Try
2848 this option if the kernel is unable to allocate
2849 IRQs or discover secondary PCI buses on your
2850 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002851 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002852 Use with caution as certain devices share
2853 address decoders between ROMs and other
2854 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002855 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002856 expansion ROMs that do not already have
2857 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002858 nobar [X86] Do not assign address space to the
2859 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002860 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002861 assigned automatically to PCI devices. You can
2862 make the kernel exclude IRQs of your ISA cards
2863 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002864 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002865 of the PIRQ table (normally generated
2866 by the BIOS) if it is outside the
2867 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002868 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002869 useful if the kernel is unable to find your
2870 secondary buses and you want to tell it
2871 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002872 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002873 numbers ourselves, overriding
2874 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002875 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002876 in the BIOS $PIR table. This is needed on
2877 some systems with broken BIOSes, notably
2878 some HP Pavilion N5400 and Omnibook XE3
2879 notebooks. This will have no effect if ACPI
2880 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002881 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002882 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002883 use_crs [X86] Use PCI host bridge window information
2884 from ACPI. On BIOSes from 2008 or later, this
2885 is enabled by default. If you need to use this,
2886 please report a bug.
2887 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2888 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002889 routeirq Do IRQ routing for all PCI devices.
2890 This is normally done in pci_enable_device(),
2891 so this option is a temporary workaround
2892 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002893 skip_isa_align [X86] do not align io start addr, so can
2894 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02002895 noearly [X86] Don't do any early type 1 scanning.
2896 This might help on some broken boards which
2897 machine check when some devices' config space
2898 is read. But various workarounds are disabled
2899 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002900 bfsort Sort PCI devices into breadth-first order.
2901 This sorting is done to get a device
2902 order compatible with older (<= 2.4) kernels.
2903 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002904 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2905 tuning and use the BIOS-configured MPS defaults.
2906 pcie_bus_safe Set every device's MPS to the largest value
2907 supported by all devices below the root complex.
2908 pcie_bus_perf Set device MPS to the largest allowable MPS
2909 based on its parent bus. Also set MRRS (Max
2910 Read Request Size) to the largest supported
2911 value (no larger than the MPS that the device
2912 or bus can support) for best performance.
2913 pcie_bus_peer2peer Set every device's MPS to 128B, which
2914 every device is guaranteed to support. This
2915 configuration allows peer-to-peer DMA between
2916 any pair of devices, possibly at the cost of
2917 reduced performance. This also guarantees
2918 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002919 cbiosize=nn[KMG] The fixed amount of bus space which is
2920 reserved for the CardBus bridge's IO window.
2921 The default value is 256 bytes.
2922 cbmemsize=nn[KMG] The fixed amount of bus space which is
2923 reserved for the CardBus bridge's memory
2924 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002925 resource_alignment=
2926 Format:
2927 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00002928 [<order of align>@]pci:<vendor>:<device>\
2929 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002930 Specifies alignment and device to reassign
2931 aligned memory resources.
2932 If <order of align> is not specified,
2933 PAGE_SIZE is used as alignment.
2934 PCI-PCI bridge can be specified, if resource
2935 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02002936 To specify the alignment for several
2937 instances of a device, the PCI vendor,
2938 device, subvendor, and subdevice may be
2939 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06002940 ecrc= Enable/disable PCIe ECRC (transaction layer
2941 end-to-end CRC checking).
2942 bios: Use BIOS/firmware settings. This is the
2943 the default.
2944 off: Turn ECRC off
2945 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002946 hpiosize=nn[KMG] The fixed amount of bus space which is
2947 reserved for hotplug bridge's IO window.
2948 Default size is 256 bytes.
2949 hpmemsize=nn[KMG] The fixed amount of bus space which is
2950 reserved for hotplug bridge's memory window.
2951 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06002952 hpbussize=nn The minimum amount of additional bus numbers
2953 reserved for buses below a hotplug bridge.
2954 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08002955 realloc= Enable/disable reallocating PCI bridge resources
2956 if allocations done by BIOS are too small to
2957 accommodate resources required by all child
2958 devices.
2959 off: Turn realloc off
2960 on: Turn realloc on
2961 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002962 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002963 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2964 only look for one device below a PCIe downstream
2965 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002966
Chuck Ebberte5665a42008-09-24 20:40:34 -04002967 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2968 Management.
2969 off Disable ASPM.
2970 force Enable ASPM even on devices that claim not to support it.
2971 WARNING: Forcing ASPM on may cause system lockups.
2972
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002973 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2974 nomsi Do not use MSI for PCI Express Native Hotplug (this
2975 makes all PCIe ports use INTx for hotplug services).
2976
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002977 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002978 auto Ask the BIOS whether or not to use native PCIe services
2979 associated with PCIe ports (PME, hot-plug, AER). Use
2980 them only if that is allowed by the BIOS.
2981 native Use native PCIe services associated with PCIe ports
2982 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002983 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2984 ports driver.
2985
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03002986 pcie_port_pm= [PCIE] PCIe port power management handling:
2987 off Disable power management of all PCIe ports
2988 force Forcibly enable power management of all PCIe ports
2989
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002990 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002991 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002992 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002993
Linus Torvalds1da177e2005-04-16 15:20:36 -07002994 pcmv= [HW,PCMCIA] BadgePAD 4
2995
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302996 pd_ignore_unused
2997 [PM]
2998 Keep all power-domains already enabled by bootloader on,
2999 even if no driver has claimed them. This is useful
3000 for debug and development, but should not be
3001 needed on a platform with proper driver support.
3002
Linus Torvalds1da177e2005-04-16 15:20:36 -07003003 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003004 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003005
3006 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3007 boot time.
3008 Format: { 0 | 1 }
3009 See arch/parisc/kernel/pdc_chassis.c
3010
Tejun Heof58dc012009-08-14 15:00:50 +09003011 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003012 Currently supported values are "embed" and "page".
3013 Archs may support subset or none of the selections.
3014 See comments in mm/percpu.c for details on each
3015 allocator. This parameter is primarily for debugging
3016 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003017
Linus Torvalds1da177e2005-04-16 15:20:36 -07003018 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003019 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003020
3021 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003022 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003023
3024 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003025 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003026
3027 plip= [PPT,NET] Parallel port network link
3028 Format: { parport<nr> | timid | 0 }
3029 See also Documentation/parport.txt.
3030
Randy Dunlap16290242011-08-13 12:34:52 -07003031 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003032 Override pmtimer IOPort with a hex value.
3033 e.g. pmtmr=0x508
3034
Bjorn Helgaas96242112011-08-11 12:14:05 -06003035 pnp.debug=1 [PNP]
3036 Enable PNP debug messages (depends on the
3037 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3038 via /sys/module/pnp/parameters/debug. We always show
3039 current resource usage; turning this on also shows
3040 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003041
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042 pnpacpi= [ACPI]
3043 { off }
3044
3045 pnpbios= [ISAPNP]
3046 { on | off | curr | res | no-curr | no-res }
3047
3048 pnp_reserve_irq=
3049 [ISAPNP] Exclude IRQs for the autoconfiguration
3050
3051 pnp_reserve_dma=
3052 [ISAPNP] Exclude DMAs for the autoconfiguration
3053
3054 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003055 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003056
3057 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003058 [ISAPNP] Exclude memory regions for the
3059 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003060 Ranges are in pairs (memory base and size).
3061
Randy Dunlap4af94f32009-04-17 18:30:28 -07003062 ports= [IP_VS_FTP] IPVS ftp helper module
3063 Default is 21.
3064 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3065 may be specified.
3066 Format: <port>,<port>....
3067
Balbir Singhc3cbd072016-12-02 00:08:26 +11003068 powersave=off [PPC] This option disables power saving features.
3069 It specifically disables cpuidle and sets the
3070 platform machine description specific power_save
3071 function to NULL. On Idle the CPU just reduces
3072 execution priority.
3073
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003074 ppc_strict_facility_enable
3075 [PPC] This option catches any kernel floating point,
3076 Altivec, VSX and SPE outside of regions specifically
3077 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3078 There is some performance impact when enabling this.
3079
Ingo Molnar45807a12007-07-15 23:40:10 -07003080 print-fatal-signals=
3081 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003082
3083 If enabled, warn about various signal handling
3084 related application anomalies: too many signals,
3085 too many POSIX.1 timers, fatal signals causing a
3086 coredump - etc.
3087
3088 If you hit the warning due to signal overflow,
3089 you might want to try "ulimit -i unlimited".
3090
Ingo Molnar45807a12007-07-15 23:40:10 -07003091 default: off.
3092
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003093 printk.always_kmsg_dump=
3094 Trigger kmsg_dump for cases other than kernel oops or
3095 panics
3096 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3097 default: disabled
3098
Borislav Petkov750afe72016-08-02 14:04:07 -07003099 printk.devkmsg={on,off,ratelimit}
3100 Control writing to /dev/kmsg.
3101 on - unlimited logging to /dev/kmsg from userspace
3102 off - logging to /dev/kmsg disabled
3103 ratelimit - ratelimit the logging
3104 Default: ratelimit
3105
Randy Dunlape84845c2007-07-15 23:40:25 -07003106 printk.time= Show timing data prefixed to each printk message line
3107 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3108
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003109 processor.max_cstate= [HW,ACPI]
3110 Limit processor to maximum C-state
3111 max_cstate=9 overrides any DMI blacklist limit.
3112
3113 processor.nocst [HW,ACPI]
3114 Ignore the _CST method to determine C-states,
3115 instead using the legacy FADT method
3116
Linus Torvalds1da177e2005-04-16 15:20:36 -07003117 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003118 Format: [schedule,]<number>
3119 Param: "schedule" - profile schedule points.
3120 Param: <number> - step/bucket size as a power of 2 for
3121 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003122 Param: "sleep" - profile D-state sleeping (millisecs).
3123 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003124 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003125
Linus Torvalds1da177e2005-04-16 15:20:36 -07003126 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3127 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003128 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003129
Randy Dunlapa9913042005-10-23 12:57:11 -07003130 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3131 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003132 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3133 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003134 psmouse.resetafter= [HW,MOUSE]
3135 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003136 (0 = never).
3137 psmouse.resolution=
3138 [HW,MOUSE] Set desired mouse resolution, in dpi.
3139 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003140 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003141 0 = disabled, 1 = enabled (default).
3142
Matthew Garrettdee28e72011-07-21 16:57:55 -04003143 pstore.backend= Specify the name of the pstore backend to use
3144
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003146 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003147
Kay Sieversdc8c8582007-08-15 12:25:38 +02003148 pty.legacy_count=
3149 [KNL] Number of legacy pty's. Overwrites compiled-in
3150 default number.
3151
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003152 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003153
Linus Torvalds1da177e2005-04-16 15:20:36 -07003154 r128= [HW,DRM]
3155
3156 raid= [HW,RAID]
Jani Nikulae52347b2016-11-03 12:10:10 +02003157 See Documentation/admin-guide/md.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158
Linus Torvalds1da177e2005-04-16 15:20:36 -07003159 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003160 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003161
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003162 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003163 The argument is a cpu list, as described above.
3164
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003165 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3166 the specified list of CPUs to be no-callback CPUs.
3167 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003168 be offloaded to "rcuox/N" kthreads created for
3169 that purpose, where "x" is "b" for RCU-bh, "p"
3170 for RCU-preempt, and "s" for RCU-sched, and "N"
3171 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003172 offloaded CPUs, which can be useful for HPC and
3173 real-time workloads. It can also improve energy
3174 efficiency for asymmetric multiprocessors.
3175
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003176 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003177 Rather than requiring that offloaded CPUs
3178 (specified by rcu_nocbs= above) explicitly
3179 awaken the corresponding "rcuoN" kthreads,
3180 make these kthreads poll for callbacks.
3181 This improves the real-time response for the
3182 offloaded CPUs by relieving them of the need to
3183 wake up the corresponding kthread, but degrades
3184 energy efficiency by requiring that the kthreads
3185 periodically wake up to do the polling.
3186
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003187 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003188 Set maximum number of finished RCU callbacks to
3189 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003190
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003191 rcutree.dump_tree= [KNL]
3192 Dump the structure of the rcu_node combining tree
3193 out at early boot. This is used for diagnostic
3194 purposes, to verify correct tree setup.
3195
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003196 rcutree.gp_cleanup_delay= [KNL]
3197 Set the number of jiffies to delay each step of
3198 RCU grace-period cleanup. This only has effect
3199 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3200
Paul E. McKenney37745d22015-01-22 18:24:08 -08003201 rcutree.gp_init_delay= [KNL]
3202 Set the number of jiffies to delay each step of
3203 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003204 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3205 is set.
3206
3207 rcutree.gp_preinit_delay= [KNL]
3208 Set the number of jiffies to delay each step of
3209 RCU grace-period pre-initialization, that is,
3210 the propagation of recent CPU-hotplug changes up
3211 the rcu_node combining tree. This only has effect
3212 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003213
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003214 rcutree.rcu_fanout_exact= [KNL]
3215 Disable autobalancing of the rcu_node combining
3216 tree. This is used by rcutorture, and might
3217 possibly be useful for architectures having high
3218 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003219
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003220 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003221 Change the number of CPUs assigned to each
3222 leaf rcu_node structure. Useful for very
3223 large systems, which will choose the value 64,
3224 and for NUMA systems with large remote-access
3225 latencies, which will choose a value aligned
3226 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003227
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003228 rcutree.jiffies_till_sched_qs= [KNL]
3229 Set required age in jiffies for a
3230 given grace period before RCU starts
3231 soliciting quiescent-state help from
3232 rcu_note_context_switch().
3233
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003234 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003235 Set delay from grace-period initialization to
3236 first attempt to force quiescent states.
3237 Units are jiffies, minimum value is zero,
3238 and maximum value is HZ.
3239
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003240 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003241 Set delay between subsequent attempts to force
3242 quiescent states. Units are jiffies, minimum
3243 value is one, and maximum value is HZ.
3244
Clark Williams21871d72014-09-12 21:21:09 -05003245 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003246 Set the SCHED_FIFO priority of the RCU per-CPU
3247 kthreads (rcuc/N). This value is also used for
3248 the priority of the RCU boost threads (rcub/N)
3249 and for the RCU grace-period kthreads (rcu_bh,
3250 rcu_preempt, and rcu_sched). If RCU_BOOST is
3251 set, valid values are 1-99 and the default is 1
3252 (the least-favored priority). Otherwise, when
3253 RCU_BOOST is not set, valid values are 0-99 and
3254 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003255
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003256 rcutree.rcu_nocb_leader_stride= [KNL]
3257 Set the number of NOCB kthread groups, which
3258 defaults to the square root of the number of
3259 CPUs. Larger numbers reduces the wakeup overhead
3260 on the per-CPU grace-period kthreads, but increases
3261 that same overhead on each group's leader.
3262
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003263 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003264 Set threshold of queued RCU callbacks beyond which
3265 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003266
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003267 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003268 Set threshold of queued RCU callbacks below which
3269 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003270
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003271 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003272 Set wakeup interval for idle CPUs that have
3273 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003274
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003275 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003276 Set wakeup interval for idle CPUs that have
3277 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3278 Lazy RCU callbacks are those which RCU can
3279 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003280
Paul E. McKenneye3c50df2017-01-06 15:14:11 -08003281 rcutree.rcu_kick_kthreads= [KNL]
3282 Cause the grace-period kthread to get an extra
3283 wake_up() if it sleeps three times longer than
3284 it should at force-quiescent-state time.
3285 This wake_up() will be accompanied by a
3286 WARN_ONCE() splat and an ftrace_dump().
3287
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003288 rcuperf.gp_exp= [KNL]
3289 Measure performance of expedited synchronous
3290 grace-period primitives.
3291
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003292 rcuperf.holdoff= [KNL]
3293 Set test-start holdoff period. The purpose of
3294 this parameter is to delay the start of the
3295 test until boot completes in order to avoid
3296 interference.
3297
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003298 rcuperf.nreaders= [KNL]
3299 Set number of RCU readers. The value -1 selects
3300 N, where N is the number of CPUs. A value
3301 "n" less than -1 selects N-n+1, where N is again
3302 the number of CPUs. For example, -2 selects N
3303 (the number of CPUs), -3 selects N+1, and so on.
3304 A value of "n" less than or equal to -N selects
3305 a single reader.
3306
3307 rcuperf.nwriters= [KNL]
3308 Set number of RCU writers. The values operate
3309 the same as for rcuperf.nreaders.
3310 N, where N is the number of CPUs
3311
3312 rcuperf.perf_runnable= [BOOT]
3313 Start rcuperf running at boot time.
3314
3315 rcuperf.shutdown= [KNL]
3316 Shut the system down after performance tests
3317 complete. This is useful for hands-off automated
3318 testing.
3319
3320 rcuperf.perf_type= [KNL]
3321 Specify the RCU implementation to test.
3322
3323 rcuperf.verbose= [KNL]
3324 Enable additional printk() statements.
3325
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003326 rcutorture.cbflood_inter_holdoff= [KNL]
3327 Set holdoff time (jiffies) between successive
3328 callback-flood tests.
3329
3330 rcutorture.cbflood_intra_holdoff= [KNL]
3331 Set holdoff time (jiffies) between successive
3332 bursts of callbacks within a given callback-flood
3333 test.
3334
3335 rcutorture.cbflood_n_burst= [KNL]
3336 Set the number of bursts making up a given
3337 callback-flood test. Set this to zero to
3338 disable callback-flood testing.
3339
3340 rcutorture.cbflood_n_per_burst= [KNL]
3341 Set the number of callbacks to be registered
3342 in a given burst of a callback-flood test.
3343
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003344 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003345 Set duration of force_quiescent_state bursts
3346 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003347
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003348 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003349 Set holdoff time within force_quiescent_state bursts
3350 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003351
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003352 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003353 Set wait time between force_quiescent_state bursts
3354 in seconds.
3355
3356 rcutorture.gp_cond= [KNL]
3357 Use conditional/asynchronous update-side
3358 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003359
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003360 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003361 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003362
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003363 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003364 Use normal (non-expedited) asynchronous
3365 update-side primitives, if available.
3366
3367 rcutorture.gp_sync= [KNL]
3368 Use normal (non-expedited) synchronous
3369 update-side primitives, if available. If all
3370 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3371 rcutorture.gp_normal=, and rcutorture.gp_sync=
3372 are zero, rcutorture acts as if is interpreted
3373 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003374
3375 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003376 Set callbacks/threads for rcu_barrier() testing.
3377
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003378 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003379 Set number of concurrent RCU writers. These just
3380 stress RCU, they don't participate in the actual
3381 test, hence the "fake".
3382
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003383 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003384 Set number of RCU readers. The value -1 selects
3385 N-1, where N is the number of CPUs. A value
3386 "n" less than -1 selects N-n-2, where N is again
3387 the number of CPUs. For example, -2 selects N
3388 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003389
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003390 rcutorture.object_debug= [KNL]
3391 Enable debug-object double-call_rcu() testing.
3392
3393 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003394 Set time (s) after boot for CPU-hotplug testing.
3395
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003396 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003397 Set time (s) between CPU-hotplug operations, or
3398 zero to disable CPU-hotplug testing.
3399
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003400 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003401 Set task-shuffle interval (s). Shuffling tasks
3402 allows some CPUs to go into dyntick-idle mode
3403 during the rcutorture test.
3404
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003405 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003406 Set time (s) after boot system shutdown. This
3407 is useful for hands-off automated testing.
3408
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003409 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003410 Duration of CPU stall (s) to test RCU CPU stall
3411 warnings, zero to disable.
3412
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003413 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003414 Time to wait (s) after boot before inducing stall.
3415
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003416 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003417 Time (s) between statistics printk()s.
3418
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003419 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003420 Time (s) to stutter testing, for example, specifying
3421 five seconds causes the test to run for five seconds,
3422 wait for five seconds, and so on. This tests RCU's
3423 ability to transition abruptly to and from idle.
3424
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003425 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003426 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3427 "Maybe" means test if the RCU implementation
3428 under test support RCU priority boosting.
3429
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003430 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003431 Duration (s) of each individual boost test.
3432
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003433 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003434 Interval (s) between each boost test.
3435
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003436 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003437 Test RCU's dyntick-idle handling. See also the
3438 rcutorture.shuffle_interval parameter.
3439
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003440 rcutorture.torture_runnable= [BOOT]
3441 Start rcutorture running at boot time.
3442
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003443 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003444 Specify the RCU implementation to test.
3445
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003446 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003447 Enable additional printk() statements.
3448
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003449 rcupdate.rcu_cpu_stall_suppress= [KNL]
3450 Suppress RCU CPU stall warning messages.
3451
3452 rcupdate.rcu_cpu_stall_timeout= [KNL]
3453 Set timeout for RCU CPU stall warning messages.
3454
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003455 rcupdate.rcu_expedited= [KNL]
3456 Use expedited grace-period primitives, for
3457 example, synchronize_rcu_expedited() instead
3458 of synchronize_rcu(). This reduces latency,
3459 but can increase CPU utilization, degrade
3460 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003461 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003462
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003463 rcupdate.rcu_normal= [KNL]
3464 Use only normal grace-period primitives,
3465 for example, synchronize_rcu() instead of
3466 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003467 real-time latency, CPU utilization, and
3468 energy efficiency, but can expose users to
3469 increased grace-period latency. This parameter
3470 overrides rcupdate.rcu_expedited. No effect on
3471 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003472
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003473 rcupdate.rcu_normal_after_boot= [KNL]
3474 Once boot has completed (that is, after
3475 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003476 only normal grace-period primitives. No effect
3477 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003478
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003479 rcupdate.rcu_task_stall_timeout= [KNL]
3480 Set timeout in jiffies for RCU task stall warning
3481 messages. Disable with a value less than or equal
3482 to zero.
3483
Pranith Kumar74860fe2014-09-19 11:34:09 -04003484 rcupdate.rcu_self_test= [KNL]
3485 Run the RCU early boot self tests
3486
3487 rcupdate.rcu_self_test_bh= [KNL]
3488 Run the RCU bh early boot self tests
3489
3490 rcupdate.rcu_self_test_sched= [KNL]
3491 Run the RCU sched early boot self tests
3492
Olof Johanssonffdfc402005-09-06 15:17:19 -07003493 rdinit= [KNL]
3494 Format: <full_path>
3495 Run specified binary instead of /init from the ramdisk,
3496 used for early userspace startup. See initrd.
3497
Robin Holt1b3a5d02013-07-08 16:01:42 -07003498 reboot= [KNL]
3499 Format (x86 or x86_64):
3500 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3501 [[,]s[mp]#### \
3502 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3503 [[,]f[orce]
3504 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3505 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3506 reboot_force is either force or not specified,
3507 reboot_cpu is s[mp]#### with #### being the processor
3508 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003509
Paul Jackson46b6d942008-07-04 10:00:09 -07003510 relax_domain_level=
3511 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003512 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003513
Linus Torvalds1da177e2005-04-16 15:20:36 -07003514 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3515
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003516 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003517 Format: nn[KMG]
3518 Reserves a hole at the top of the kernel virtual
3519 address space.
3520
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003521 reservelow= [X86]
3522 Format: nn[K]
3523 Set the amount of memory to reserve for BIOS at
3524 the bottom of the address space.
3525
Vivek Goyal7e962872006-09-27 01:50:44 -07003526 reset_devices [KNL] Force drivers to reset the underlying device
3527 during initialization.
3528
Randy Dunlapa9913042005-10-23 12:57:11 -07003529 resume= [SWSUSP]
3530 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003531 Format:
3532 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003533
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003534 resume_offset= [SWSUSP]
3535 Specify the offset from the beginning of the partition
3536 given by "resume=" at which the swap header is located,
3537 in <PAGE_SIZE> units (needed only for swap files).
3538 See Documentation/power/swsusp-and-swap-files.txt
3539
Barry Songf126f732011-10-10 23:38:41 +02003540 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3541 read the resume files
3542
Barry Song6f8d7022011-10-06 20:34:46 +02003543 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3544 Useful for devices that are detected asynchronously
3545 (e.g. USB and MMC devices).
3546
Bojan Smojverf996fc92010-09-09 23:06:23 +02003547 hibernate= [HIBERNATION]
3548 noresume Don't check if there's a hibernation image
3549 present during boot.
3550 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003551 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003552 protect_image Turn on image protection during restoration
3553 (that will set all pages holding image data
3554 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003555
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003556 retain_initrd [RAM] Keep initrd memory after extraction
3557
Andrew Clausen0efbb782015-01-09 20:24:55 +00003558 rfkill.default_state=
3559 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3560 etc. communication is blocked by default.
3561 1 Unblocked.
3562
3563 rfkill.master_switch_mode=
3564 0 The "airplane mode" button does nothing.
3565 1 The "airplane mode" button toggles between everything
3566 blocked and the previous configuration.
3567 2 The "airplane mode" button toggles between everything
3568 blocked and everything unblocked.
3569
Linus Torvalds1da177e2005-04-16 15:20:36 -07003570 rhash_entries= [KNL,NET]
3571 Set number of hash buckets for route cache
3572
Linus Torvalds1da177e2005-04-16 15:20:36 -07003573 ro [KNL] Mount root device read-only on boot
3574
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003575 rodata= [KNL]
3576 on Mark read-only kernel memory as read-only (default).
3577 off Leave read-only kernel memory writable for debugging.
3578
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003579 rockchip.usb_uart
3580 Enable the uart passthrough on the designated usb port
3581 on Rockchip SoCs. When active, the signals of the
3582 debug-uart get routed to the D+ and D- pins of the usb
3583 port and the regular usb controller gets disabled.
3584
Linus Torvalds1da177e2005-04-16 15:20:36 -07003585 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003586 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003587
3588 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3589 mount the root filesystem
3590
3591 rootflags= [KNL] Set root filesystem mount option string
3592
3593 rootfstype= [KNL] Set root filesystem type
3594
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003595 rootwait [KNL] Wait (indefinitely) for root device to show up.
3596 Useful for devices that are detected asynchronously
3597 (e.g. USB and MMC devices).
3598
Robert Tivy5c71d612013-03-28 18:41:46 -07003599 rproc_mem=nn[KMG][@address]
3600 [KNL,ARM,CMA] Remoteproc physical memory block.
3601 Memory area to be used by remote processor image,
3602 managed by CMA.
3603
Linus Torvalds1da177e2005-04-16 15:20:36 -07003604 rw [KNL] Mount root device read-write on boot
3605
3606 S [KNL] Run init in single mode
3607
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003608 s390_iommu= [HW,S390]
3609 Set s390 IOTLB flushing mode
3610 strict
3611 With strict flushing every unmap operation will result in
3612 an IOTLB flush. Default is lazy flushing before reuse,
3613 which is faster.
3614
Linus Torvalds1da177e2005-04-16 15:20:36 -07003615 sa1100ir [NET]
3616 See drivers/net/irda/sa1100_ir.c.
3617
Linus Torvalds1da177e2005-04-16 15:20:36 -07003618 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003619
Mike Travisf6630112009-11-17 18:22:15 -06003620 sched_debug [KNL] Enables verbose scheduler debug messages.
3621
Mel Gormancb251762016-02-05 09:08:36 +00003622 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3623 Allowed values are enable and disable. This feature
3624 incurs a small amount of overhead in the scheduler
3625 but is useful for debugging and performance tuning.
3626
Mike Galbraith5307c952012-05-08 12:20:58 +02003627 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3628 xtime_lock contention on larger systems, and/or RCU lock
3629 contention on all systems with CONFIG_MAXSMP set.
3630 Format: { "0" | "1" }
3631 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3632 1 -- enable.
3633 Note: increases power consumption, thus should only be
3634 enabled if running jitter sensitive (HPC/RT) workloads.
3635
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003636 security= [SECURITY] Choose a security module to enable at boot.
3637 If this boot parameter is not specified, only the first
3638 security module asking for security registration will be
3639 loaded. An invalid security module name will be treated
3640 as if no module has been chosen.
3641
3642 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003643 Format: { "0" | "1" }
3644 See security/selinux/Kconfig help text.
3645 0 -- disable.
3646 1 -- enable.
3647 Default value is set via kernel config option.
3648 If enabled at boot time, /selinux/disable can be used
3649 later to disable prior to initial policy load.
3650
John Johansenc1c124e2010-07-29 14:48:09 -07003651 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3652 Format: { "0" | "1" }
3653 See security/apparmor/Kconfig help text
3654 0 -- disable.
3655 1 -- enable.
3656 Default value is set via kernel config option.
3657
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003658 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003659
Linus Torvalds1da177e2005-04-16 15:20:36 -07003660 shapers= [NET]
3661 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003662
Linus Torvalds1da177e2005-04-16 15:20:36 -07003663 simeth= [IA-64]
3664 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003665
Linus Torvalds1da177e2005-04-16 15:20:36 -07003666 slram= [HW,MTD]
3667
Joonsoo Kim423c9292014-10-09 15:26:22 -07003668 slab_nomerge [MM]
3669 Disable merging of slabs with similar size. May be
3670 necessary if there is some reason to distinguish
3671 allocs to different slabs. Debug options disable
3672 merging on their own.
3673 For more information see Documentation/vm/slub.txt.
3674
David Rientjes3df1ccc2011-10-18 22:09:28 -07003675 slab_max_order= [MM, SLAB]
3676 Determines the maximum allowed order for slabs.
3677 A high setting may cause OOMs due to memory
3678 fragmentation. Defaults to 1 for systems with
3679 more than 32MB of RAM, 0 otherwise.
3680
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003681 slub_debug[=options[,slabs]] [MM, SLUB]
3682 Enabling slub_debug allows one to determine the
3683 culprit if slab objects become corrupted. Enabling
3684 slub_debug can create guard zones around objects and
3685 may poison objects when not in use. Also tracks the
3686 last alloc / free. For more information see
3687 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003688
3689 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003690 Determines the maximum allowed order for slabs.
3691 A high setting may cause OOMs due to memory
3692 fragmentation. For more information see
3693 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003694
3695 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003696 The minimum number of objects per slab. SLUB will
3697 increase the slab order up to slub_max_order to
3698 generate a sufficiently large slab able to contain
3699 the number of objects indicated. The higher the number
3700 of objects the smaller the overhead of tracking slabs
3701 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003702 For more information see Documentation/vm/slub.txt.
3703
3704 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003705 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003706 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003707 For more information see Documentation/vm/slub.txt.
3708
3709 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003710 Same with slab_nomerge. This is supported for legacy.
3711 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003712
Linus Torvalds1da177e2005-04-16 15:20:36 -07003713 smart2= [HW]
3714 Format: <io1>[,<io2>[,...,<io8>]]
3715
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003716 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3717 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3718 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3719 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3720 smsc-ircc2.ircc_irq= [HW] IRQ line
3721 smsc-ircc2.ircc_dma= [HW] DMA channel
3722 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3723 0: Toshiba Satellite 1800 (GP data pin select)
3724 1: Fast pin select (default)
3725 2: ATC IRMode
3726
Sascha Silbe52c48c52016-04-05 12:53:38 +02003727 smt [KNL,S390] Set the maximum number of threads (logical
3728 CPUs) to use per physical CPU on systems capable of
3729 symmetric multithreading (SMT). Will be capped to the
3730 actual hardware limit.
3731 Format: <integer>
3732 Default: -1 (no limit)
3733
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003734 softlockup_panic=
3735 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003736 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003737
Aaron Tomlined235872014-06-23 13:22:05 -07003738 softlockup_all_cpu_backtrace=
3739 [KNL] Should the soft-lockup detector generate
3740 backtraces on all cpus.
3741 Format: <integer>
3742
Linus Torvalds1da177e2005-04-16 15:20:36 -07003743 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003744 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003745
Linus Torvalds1da177e2005-04-16 15:20:36 -07003746 spia_io_base= [HW,MTD]
3747 spia_fio_base=
3748 spia_pedr=
3749 spia_peddr=
3750
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003751 stacktrace [FTRACE]
3752 Enabled the stack tracer on boot up.
3753
Steven Rostedt762e1202011-12-19 22:01:00 -05003754 stacktrace_filter=[function-list]
3755 [FTRACE] Limit the functions that the stack tracer
3756 will trace at boot up. function-list is a comma separated
3757 list of functions. This list can be changed at run
3758 time by the stack_trace_filter file in the debugfs
3759 tracing directory. Note, this enables stack tracing
3760 and the stacktrace above is not needed.
3761
Linus Torvalds1da177e2005-04-16 15:20:36 -07003762 sti= [PARISC,HW]
3763 Format: <num>
3764 Set the STI (builtin display/keyboard on the HP-PARISC
3765 machines) console (graphic card) which should be used
3766 as the initial boot-console.
3767 See also comment in drivers/video/console/sticore.c.
3768
3769 sti_font= [HW]
3770 See comment in drivers/video/console/sticore.c.
3771
3772 stifb= [HW]
3773 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3774
Trond Myklebustcbf11072009-08-09 15:06:19 -04003775 sunrpc.min_resvport=
3776 sunrpc.max_resvport=
3777 [NFS,SUNRPC]
3778 SunRPC servers often require that client requests
3779 originate from a privileged port (i.e. a port in the
3780 range 0 < portnr < 1024).
3781 An administrator who wishes to reserve some of these
3782 ports for other uses may adjust the range that the
3783 kernel's sunrpc client considers to be privileged
3784 using these two parameters to set the minimum and
3785 maximum port values.
3786
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003787 sunrpc.svc_rpc_per_connection_limit=
3788 [NFS,SUNRPC]
3789 Limit the number of requests that the server will
3790 process in parallel from a single connection.
3791 The default value is 0 (no limit).
3792
Greg Banks42a7fc42007-03-06 01:42:23 -08003793 sunrpc.pool_mode=
3794 [NFS]
3795 Control how the NFS server code allocates CPUs to
3796 service thread pools. Depending on how many NICs
3797 you have and where their interrupts are bound, this
3798 option will affect which CPUs will do NFS serving.
3799 Note: this parameter cannot be changed while the
3800 NFS server is running.
3801
3802 auto the server chooses an appropriate mode
3803 automatically using heuristics
3804 global a single global pool contains all CPUs
3805 percpu one pool for each CPU
3806 pernode one pool for each NUMA node (equivalent
3807 to global on non-NUMA machines)
3808
Trond Myklebustcbf11072009-08-09 15:06:19 -04003809 sunrpc.tcp_slot_table_entries=
3810 sunrpc.udp_slot_table_entries=
3811 [NFS,SUNRPC]
3812 Sets the upper limit on the number of simultaneous
3813 RPC calls that can be sent from the client to a
3814 server. Increasing these values may allow you to
3815 improve throughput, but will also increase the
3816 amount of memory reserved for use by the client.
3817
Brian Norris1d4a9c12015-02-22 21:16:49 -08003818 suspend.pm_test_delay=
3819 [SUSPEND]
3820 Sets the number of seconds to remain in a suspend test
3821 mode before resuming the system (see
3822 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3823 is set. Default value is 5.
3824
Michal Hocko07555ac2013-08-22 16:35:46 -07003825 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003826 [KNL] Enable accounting of swap in memory resource
3827 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003828 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003829
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003830 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003831 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003832 <int> -- Number of I/O TLB slabs
3833 force -- force using of bounce buffers even if they
3834 wouldn't be automatically used by the kernel
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003835 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07003836
Linus Torvalds1da177e2005-04-16 15:20:36 -07003837 switches= [HW,M68k]
3838
Andi Kleene52eec12010-09-08 16:54:17 +02003839 sysfs.deprecated=0|1 [KNL]
3840 Enable/disable old style sysfs layout for old udev
3841 on older distributions. When this option is enabled
3842 very new udev will not work anymore. When this option
3843 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3844 in older udev will not work anymore.
3845 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3846 the kernel configuration.
3847
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003848 sysrq_always_enabled
3849 [KNL]
3850 Ignore sysrq setting - this boot parameter will
3851 neutralize any effect of /proc/sys/kernel/sysrq.
3852 Useful for debugging.
3853
Fabian Frederick747029a2014-11-06 19:46:50 +01003854 tcpmhash_entries= [KNL,NET]
3855 Set the number of tcp_metrics_hash slots.
3856 Default value is 8192 or 16384 depending on total
3857 ram pages. This is used to specify the TCP metrics
3858 cache size. See Documentation/networking/ip-sysctl.txt
3859 "tcp_no_metrics_save" section for more details.
3860
Linus Torvalds1da177e2005-04-16 15:20:36 -07003861 tdfx= [HW,DRM]
3862
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003863 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003864 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003865 standby suspend) or "freeze" (for suspend type freeze)
3866 as the system sleep state during system startup with
3867 the optional capability to repeat N number of times.
3868 The system is woken from this state using a
3869 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003870
Linus Torvalds1da177e2005-04-16 15:20:36 -07003871 thash_entries= [KNL,NET]
3872 Set number of hash buckets for TCP connection
3873
Len Brownf8707ec2007-08-12 00:12:54 -04003874 thermal.act= [HW,ACPI]
3875 -1: disable all active trip points in all thermal zones
3876 <degrees C>: override all lowest active trip points
3877
Len Brownc52a7412007-08-14 15:49:32 -04003878 thermal.crt= [HW,ACPI]
3879 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003880 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003881
Len Brownf5487142007-08-12 00:12:44 -04003882 thermal.nocrt= [HW,ACPI]
3883 Set to disable actions on ACPI thermal zone
3884 critical and hot trip points.
3885
Len Brown72b33ef2007-08-12 00:12:17 -04003886 thermal.off= [HW,ACPI]
3887 1: disable ACPI thermal control
3888
Len Browna70cdc52007-08-12 00:12:35 -04003889 thermal.psv= [HW,ACPI]
3890 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003891 <degrees C>: override all passive trip points to this
3892 value
Len Browna70cdc52007-08-12 00:12:35 -04003893
Len Brown730ff342007-08-12 00:12:26 -04003894 thermal.tzp= [HW,ACPI]
3895 Specify global default ACPI thermal zone polling rate
3896 <deci-seconds>: poll all this frequency
3897 0: no polling (default)
3898
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003899 threadirqs [KNL]
3900 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003901 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003902
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003903 tmem [KNL,XEN]
3904 Enable the Transcendent memory driver if built-in.
3905
3906 tmem.cleancache=0|1 [KNL, XEN]
3907 Default is on (1). Disable the usage of the cleancache
3908 API to send anonymous pages to the hypervisor.
3909
3910 tmem.frontswap=0|1 [KNL, XEN]
3911 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003912 API to send swap pages to the hypervisor. If disabled
3913 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003914
3915 tmem.selfballooning=0|1 [KNL, XEN]
3916 Default is on (1). Disable the driving of swap pages
3917 to the hypervisor.
3918
3919 tmem.selfshrinking=0|1 [KNL, XEN]
3920 Default is on (1). Partial swapoff that immediately
3921 transfers pages from Xen hypervisor back to the
3922 kernel based on different criteria.
3923
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003924 topology= [S390]
3925 Format: {off | on}
3926 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003927 topology information if the hardware supports this.
3928 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003929 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003930 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003931
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003932 topology_updates= [KNL, PPC, NUMA]
3933 Format: {off}
3934 Specify if the kernel should ignore (off)
3935 topology updates sent by the hypervisor to this
3936 LPAR.
3937
Linus Torvalds1da177e2005-04-16 15:20:36 -07003938 tp720= [HW,PS2]
3939
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003940 tpm_suspend_pcr=[HW,TPM]
3941 Format: integer pcr id
3942 Specify that at suspend time, the tpm driver
3943 should extend the specified pcr with zeros,
3944 as a workaround for some chips which fail to
3945 flush the last written pcr on TPM_SaveState.
3946 This will guarantee that all the other pcrs
3947 are saved.
3948
Li Zefan9d612be2009-06-24 17:33:15 +08003949 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003950 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003951
Li Zefan020e5f82009-07-01 10:47:05 +08003952 trace_event=[event-list]
3953 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07003954 to facilitate early boot debugging. The event-list is a
3955 comma separated list of trace events to enable. See
3956 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08003957
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003958 trace_options=[option-list]
3959 [FTRACE] Enable or disable tracer options at boot.
3960 The option-list is a comma delimited list of options
3961 that can be enabled or disabled just as if you were
3962 to echo the option name into
3963
3964 /sys/kernel/debug/tracing/trace_options
3965
3966 For example, to enable stacktrace option (to dump the
3967 stack trace of each event), add to the command line:
3968
3969 trace_options=stacktrace
3970
3971 See also Documentation/trace/ftrace.txt "trace options"
3972 section.
3973
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003974 tp_printk[FTRACE]
3975 Have the tracepoints sent to printk as well as the
3976 tracing ring buffer. This is useful for early boot up
3977 where the system hangs or reboots and does not give the
3978 option for reading the tracing buffer or performing a
3979 ftrace_dump_on_oops.
3980
3981 To turn off having tracepoints sent to printk,
3982 echo 0 > /proc/sys/kernel/tracepoint_printk
3983 Note, echoing 1 into this file without the
3984 tracepoint_printk kernel cmdline option has no effect.
3985
3986 ** CAUTION **
3987
3988 Having tracepoints sent to printk() and activating high
3989 frequency tracepoints such as irq or sched, can cause
3990 the system to live lock.
3991
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003992 traceoff_on_warning
3993 [FTRACE] enable this option to disable tracing when a
3994 warning is hit. This turns off "tracing_on". Tracing can
3995 be enabled again by echoing '1' into the "tracing_on"
3996 file located in /sys/kernel/debug/tracing/
3997
3998 This option is useful, as it disables the trace before
3999 the WARNING dump is called, which prevents the trace to
4000 be filled with content caused by the warning output.
4001
4002 This option can also be set at run time via the sysctl
4003 option: kernel/traceoff_on_warning
4004
Jiri Kosinafcf4d8212012-03-21 16:34:02 -07004005 transparent_hugepage=
4006 [KNL]
4007 Format: [always|madvise|never]
4008 Can be used to control the default behavior of the system
4009 with respect to transparent hugepages.
4010 See Documentation/vm/transhuge.txt for more details.
4011
john stultzd3b8f882009-08-17 16:40:47 -07004012 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004013 Format: <string>
4014 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004015 disables clocksource verification at runtime, as well
4016 as the stability checks done at bootup. Used to enable
4017 high-resolution timer mode on older hardware, and in
4018 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004019 [x86] noirqtime: Do not use TSC to do irq accounting.
4020 Used to run time disable IRQ_TIME_ACCOUNTING on any
4021 platforms where RDTSC is slow and this accounting
4022 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004023
Randy Dunlapa9913042005-10-23 12:57:11 -07004024 turbografx.map[2|3]= [HW,JOY]
4025 TurboGraFX parallel port interface
4026 Format:
4027 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004028 See also Documentation/input/joystick-parport.txt
4029
Christian Kujaub6935f82011-05-31 15:22:05 +00004030 udbg-immortal [PPC] When debugging early kernel crashes that
Jani Nikulae52347b2016-11-03 12:10:10 +02004031 happen after console_init() and before a proper
Christian Kujaub6935f82011-05-31 15:22:05 +00004032 console driver takes over, this boot options might
4033 help "seeing" what's going on.
4034
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004035 uhash_entries= [KNL,NET]
4036 Set number of hash buckets for UDP/UDP-Lite connections
4037
Alan Stern5f8364b2006-12-05 16:29:55 -05004038 uhci-hcd.ignore_oc=
4039 [USB] Ignore overcurrent events (default N).
4040 Some badly-designed motherboards generate lots of
4041 bogus events, for ports that aren't wired to
4042 anything. Set this parameter to avoid log spamming.
4043 Note that genuine overcurrent events won't be
4044 reported either.
4045
Simon Arlotte3a61b02008-07-19 23:32:54 +01004046 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004047 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004048
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004049 usbcore.authorized_default=
4050 [USB] Default USB device authorization:
4051 (default -1 = authorized except for wireless USB,
4052 0 = not authorized, 1 = authorized)
4053
Alan Sternb5e795f2007-02-20 15:00:53 -05004054 usbcore.autosuspend=
4055 [USB] The autosuspend time delay (in seconds) used
4056 for newly-detected USB devices (default 2). This
4057 is the time required before an idle device will be
4058 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004059 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004060
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004061 usbcore.usbfs_snoop=
4062 [USB] Set to log all usbfs traffic (default 0 = off).
4063
Alan Stern0290cc92015-11-20 13:53:22 -05004064 usbcore.usbfs_snoop_max=
4065 [USB] Maximum number of bytes to snoop in each URB
4066 (default = 65536).
4067
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004068 usbcore.blinkenlights=
4069 [USB] Set to cycle leds on hubs (default 0 = off).
4070
4071 usbcore.old_scheme_first=
4072 [USB] Start with the old device initialization
4073 scheme (default 0 = off).
4074
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004075 usbcore.usbfs_memory_mb=
4076 [USB] Memory limit (in MB) for buffers allocated by
4077 usbfs (default = 16, 0 = max = 2047).
4078
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004079 usbcore.use_both_schemes=
4080 [USB] Try the other device initialization scheme
4081 if the first one fails (default 1 = enabled).
4082
4083 usbcore.initial_descriptor_timeout=
4084 [USB] Specifies timeout for the initial 64-byte
4085 USB_REQ_GET_DESCRIPTOR request in milliseconds
4086 (default 5000 = 5.0 seconds).
4087
Oliver Neukum40d58142015-12-03 15:03:32 +01004088 usbcore.nousb [USB] Disable the USB subsystem
4089
Linus Torvalds1da177e2005-04-16 15:20:36 -07004090 usbhid.mousepoll=
4091 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004092
Alan Sternd4f373e2008-11-10 14:07:45 -05004093 usb-storage.delay_use=
4094 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004095 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004096
4097 usb-storage.quirks=
4098 [UMS] A list of quirks entries to supplement or
4099 override the built-in unusual_devs list. List
4100 entries are separated by commas. Each entry has
4101 the form VID:PID:Flags where VID and PID are Vendor
4102 and Product ID values (4-digit hex numbers) and
4103 Flags is a set of characters, each corresponding
4104 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004105 a = SANE_SENSE (collect more than 18 bytes
4106 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004107 b = BAD_SENSE (don't collect more than 18
4108 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004109 c = FIX_CAPACITY (decrease the reported
4110 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004111 d = NO_READ_DISC_INFO (don't use
4112 READ_DISC_INFO command);
4113 e = NO_READ_CAPACITY_16 (don't use
4114 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004115 f = NO_REPORT_OPCODES (don't use report opcodes
4116 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004117 g = MAX_SECTORS_240 (don't transfer more than
4118 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004119 h = CAPACITY_HEURISTICS (decrease the
4120 reported device capacity by one
4121 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004122 i = IGNORE_DEVICE (don't bind to this
4123 device);
Hans de Goede13630742016-04-12 12:27:09 +02004124 j = NO_REPORT_LUNS (don't use report luns
4125 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004126 l = NOT_LOCKABLE (don't try to lock and
4127 unlock ejectable media);
4128 m = MAX_SECTORS_64 (don't transfer more
4129 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004130 n = INITIAL_READ10 (force a retry of the
4131 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004132 o = CAPACITY_OK (accept the capacity
4133 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004134 p = WRITE_CACHE (the device cache is ON
4135 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004136 r = IGNORE_RESIDUE (the device reports
4137 bogus residue values);
4138 s = SINGLE_LUN (the device has only one
4139 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004140 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4141 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004142 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004143 w = NO_WP_DETECT (don't test whether the
4144 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004145 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4146 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004147 Example: quirks=0419:aaf5:rl,0421:0433:rc
4148
Stephen Boydac1667d2011-08-13 12:34:50 -07004149 user_debug= [KNL,ARM]
4150 Format: <int>
4151 See arch/arm/Kconfig.debug help text.
4152 1 - undefined instruction events
4153 2 - system calls
4154 4 - invalid data aborts
4155 8 - SIGSEGV faults
4156 16 - SIGBUS faults
4157 Example: user_debug=31
4158
Ian Campbell14315592010-02-17 10:38:10 +00004159 userpte=
4160 [X86] Flags controlling user PTE allocations.
4161
4162 nohigh = do not allocate PTE pages in
4163 HIGHMEM regardless of setting
4164 of CONFIG_HIGHPTE.
4165
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304166 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004167 On X86_32, this is an alias for vdso32=. Otherwise:
4168
4169 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004170 vdso=0: disable VDSO mapping
4171
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004172 vdso32= [X86] Control the 32-bit vDSO
4173 vdso32=1: enable 32-bit VDSO
4174 vdso32=0 or vdso32=2: disable 32-bit VDSO
4175
4176 See the help text for CONFIG_COMPAT_VDSO for more
4177 details. If CONFIG_COMPAT_VDSO is set, the default is
4178 vdso32=0; otherwise, the default is vdso32=1.
4179
4180 For compatibility with older kernels, vdso32=2 is an
4181 alias for vdso32=0.
4182
4183 Try vdso32=0 if you encounter an error that says:
4184 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004185
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004186 vector= [IA-64,SMP]
4187 vector=percpu: enable percpu vector domain
4188
Linus Torvalds1da177e2005-04-16 15:20:36 -07004189 video= [FB] Frame buffer configuration
4190 See Documentation/fb/modedb.txt.
4191
Aaron Lu3afe6da2013-06-20 15:08:55 +08004192 video.brightness_switch_enabled= [0,1]
4193 If set to 1, on receiving an ACPI notify event
4194 generated by hotkey, video driver will adjust brightness
4195 level and then send out the event to user space through
4196 the allocated input device; If set to 0, video driver
4197 will only send out the event without touching backlight
4198 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004199 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004200
Pawel Moll81a054c2012-05-09 18:30:16 +01004201 virtio_mmio.device=
4202 [VMMIO] Memory mapped virtio (platform) device.
4203
4204 <size>@<baseaddr>:<irq>[:<id>]
4205 where:
4206 <size> := size (can use standard suffixes
4207 like K, M and G)
4208 <baseaddr> := physical base address
4209 <irq> := interrupt number (as passed to
4210 request_irq())
4211 <id> := (optional) platform device id
4212 example:
4213 virtio_mmio.device=1K@0x100b0000:48:7
4214
4215 Can be used multiple times for multiple devices.
4216
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004217 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004218 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004219 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004220 Use vga=ask for menu.
4221 This is actually a boot loader parameter; the value is
4222 passed to the kernel using a special protocol.
4223
Randy Dunlapa9913042005-10-23 12:57:11 -07004224 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004225 size of <nn>. This can be used to increase the
4226 minimum size (128MB on x86). It can also be used to
4227 decrease the size and leave more room for directly
4228 mapped kernel RAM.
4229
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004230 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4231 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004232
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004233 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4234 Format: <command>
4235
4236 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4237 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004238
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004239 vsyscall= [X86-64]
4240 Controls the behavior of vsyscalls (i.e. calls to
4241 fixed addresses of 0xffffffffff600x00 from legacy
4242 code). Most statically-linked binaries and older
4243 versions of glibc use these calls. Because these
4244 functions are at fixed addresses, they make nice
4245 targets for exploits that can control RIP.
4246
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004247 emulate [default] Vsyscalls turn into traps and are
4248 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004249
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004250 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004251 This is a little bit faster than trapping
4252 and makes a few dynamic recompilers work
4253 better than they would in emulation mode.
4254 It also makes exploits much easier to write.
4255
4256 none Vsyscalls don't work at all. This makes
4257 them quite hard to use for exploits but
4258 might break your system.
4259
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004260 vt.color= [VT] Default text color.
4261 Format: 0xYX, X = foreground, Y = background.
4262 Default: 0x07 = light gray on black.
4263
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004264 vt.cur_default= [VT] Default cursor shape.
4265 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4266 the parameters of the <Esc>[?A;B;Cc escape sequence;
4267 see VGA-softcursor.txt. Default: 2 = underline.
4268
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004269 vt.default_blu= [VT]
4270 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4271 Change the default blue palette of the console.
4272 This is a 16-member array composed of values
4273 ranging from 0-255.
4274
4275 vt.default_grn= [VT]
4276 Format: <green0>,<green1>,<green2>,...,<green15>
4277 Change the default green palette of the console.
4278 This is a 16-member array composed of values
4279 ranging from 0-255.
4280
4281 vt.default_red= [VT]
4282 Format: <red0>,<red1>,<red2>,...,<red15>
4283 Change the default red palette of the console.
4284 This is a 16-member array composed of values
4285 ranging from 0-255.
4286
4287 vt.default_utf8=
4288 [VT]
4289 Format=<0|1>
4290 Set system-wide default UTF-8 mode for all tty's.
4291 Default is 1, i.e. UTF-8 mode is enabled for all
4292 newly opened terminals.
4293
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004294 vt.global_cursor_default=
4295 [VT]
4296 Format=<-1|0|1>
4297 Set system-wide default for whether a cursor
4298 is shown on new VTs. Default is -1,
4299 i.e. cursors will be created by default unless
4300 overridden by individual drivers. 0 will hide
4301 cursors, 1 will display them.
4302
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004303 vt.italic= [VT] Default color for italic text; 0-15.
4304 Default: 2 = green.
4305
4306 vt.underline= [VT] Default color for underlined text; 0-15.
4307 Default: 3 = cyan.
4308
Randy Dunlap4724ba572010-05-03 11:42:52 -07004309 watchdog timers [HW,WDT] For information on watchdog timers,
4310 see Documentation/watchdog/watchdog-parameters.txt
4311 or other driver-specific files in the
4312 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004313
Tejun Heo82607adc2015-12-08 11:28:04 -05004314 workqueue.watchdog_thresh=
4315 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4316 warn stall conditions and dump internal state to
4317 help debugging. 0 disables workqueue stall
4318 detection; otherwise, it's the stall threshold
4319 duration in seconds. The default value is 30 and
4320 it can be updated at runtime by writing to the
4321 corresponding sysfs file.
4322
Tejun Heod55262c2013-04-01 11:23:38 -07004323 workqueue.disable_numa
4324 By default, all work items queued to unbound
4325 workqueues are affine to the NUMA nodes they're
4326 issued on, which results in better behavior in
4327 general. If NUMA affinity needs to be disabled for
4328 whatever reason, this option can be used. Note
4329 that this also can be controlled per-workqueue for
4330 workqueues visible under /sys/bus/workqueue/.
4331
Viresh Kumarcee22a12013-04-08 16:45:40 +05304332 workqueue.power_efficient
4333 Per-cpu workqueues are generally preferred because
4334 they show better performance thanks to cache
4335 locality; unfortunately, per-cpu workqueues tend to
4336 be more power hungry than unbound workqueues.
4337
4338 Enabling this makes the per-cpu workqueues which
4339 were observed to contribute significantly to power
4340 consumption unbound, leading to measurably lower
4341 power usage at the cost of small performance
4342 overhead.
4343
4344 The default value of this parameter is determined by
4345 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4346
Tejun Heof303fccb2016-02-09 17:59:38 -05004347 workqueue.debug_force_rr_cpu
4348 Workqueue used to implicitly guarantee that work
4349 items queued without explicit CPU specified are put
4350 on the local CPU. This guarantee is no longer true
4351 and while local CPU is still preferred work items
4352 may be put on foreign CPUs. This debug option
4353 forces round-robin CPU selection to flush out
4354 usages which depend on the now broken guarantee.
4355 When enabled, memory and cache locality will be
4356 impacted.
4357
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004358 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4359 default x2apic cluster mode on platforms
4360 supporting x2apic.
4361
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004362 x86_intel_mid_timer= [X86-32,APBT]
4363 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004364 Two valid options are apbt timer only and lapic timer
4365 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004366 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004367
Juergen Grossc70727a2015-07-17 06:51:36 +02004368 xen_512gb_limit [KNL,X86-64,XEN]
4369 Restricts the kernel running paravirtualized under Xen
4370 to use only up to 512 GB of RAM. The reason to do so is
4371 crash analysis tools and Xen tools for doing domain
4372 save/restore/migration must be enabled to handle larger
4373 domains.
4374
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004375 xen_emul_unplug= [HW,X86,XEN]
4376 Unplug Xen emulated devices
4377 Format: [unplug0,][unplug1]
4378 ide-disks -- unplug primary master IDE devices
4379 aux-ide-disks -- unplug non-primary-master IDE devices
4380 nics -- unplug network devices
4381 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004382 unnecessary -- unplugging emulated devices is
4383 unnecessary even if the host did not respond to
4384 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004385 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004386
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004387 xen_nopvspin [X86,XEN]
4388 Disables the ticketlock slowpath using Xen PV
4389 optimizations.
4390
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004391 xen_nopv [X86]
4392 Disables the PV optimizations forcing the HVM guest to
4393 run as generic HVM guest with no PV drivers.
4394
Linus Torvalds1da177e2005-04-16 15:20:36 -07004395 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004396 Format:
4397 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]