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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
Randy Dunlapca1eda22009-05-06 16:02:58 -070020Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
Stefan Richtera901ebb2006-04-01 01:43:18 +020026This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
Stefan Richter6585fa82006-04-01 01:44:30 +020033The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100039 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070043 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020044 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070045 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080046 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070047 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070048 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000049 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040054 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070056 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070057 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050060 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070062 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080063 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050067 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020068 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070069 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070076 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070078 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070079 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070084 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070088 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070097 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070099 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700101 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900103 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300108 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500110 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100114 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700119 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700122 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100124 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
126In addition, the following text indicates that the option:
127
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
131
132Parameters denoted with BOOT are actually interpreted by the boot
133loader, and have no meaning to the kernel directly.
134Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500135need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
Karsten Weiss55588702007-02-13 13:26:21 +0100137There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700138See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100139
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141a trailing = on the name of any parameter states that that parameter will
142be entered as an environment variable, whereas its absence indicates that
143it will appear as a kernel argument readable via /proc/cmdline by programs
144running once the system is up.
145
jens m. noedler9c4751f2006-09-29 02:00:27 -0700146The number of kernel parameters is not limited, but the length of the
147complete command line (parameters including spaces etc.) is limited to
148a fixed number of characters. This limit depends on the architecture
149and is between 256 and 4096 characters. It is defined in the file
150./include/asm/setup.h as COMMAND_LINE_SIZE.
151
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800152Finally, the [KMG] suffix is commonly described after a number of kernel
153parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155bytes respectively. Such letter suffixes can also be entirely omitted.
156
jens m. noedler9c4751f2006-09-29 02:00:27 -0700157
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530158 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800159 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500160 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700164 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800166 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800167 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Paul Bolle395cf962011-08-15 02:02:26 +0200169 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170
Takao Indoh4996c022011-07-14 18:05:21 -0400171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
175
Len Browna1fdcc02007-03-11 03:26:14 -0400176 acpi_apic_instance= [ACPI, IOAPIC]
177 Format: <int>
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400180 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400181
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
184 acpi_backlight=video
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
188
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200212
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800216
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800217 acpi_force_table_verification [HW,ACPI]
218 Enable table checksum verification during early stage.
219 By default, this is disabled due to x86 early mapping
220 size limitation.
221
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700222 acpi_irq_balance [HW,ACPI]
223 ACPI will balance active IRQs
224 default in APIC mode
225
226 acpi_irq_nobalance [HW,ACPI]
227 ACPI will not move active IRQs (default)
228 default in PIC mode
229
230 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
231 Format: <irq>,<irq>...
232
233 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
234 use by PCI
235 Format: <irq>,<irq>...
236
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800237 acpi_no_auto_serialize [HW,ACPI]
238 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800239 AML control methods that contain the opcodes to create
240 named objects will be marked as "Serialized" by the
241 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800242 This feature is enabled by default.
243 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800244
Lv Zhenga94e88c2014-04-04 12:39:11 +0800245 acpi_no_static_ssdt [HW,ACPI]
246 Disable installation of static SSDTs at early boot time
247 By default, SSDTs contained in the RSDT/XSDT will be
248 installed automatically and they will appear under
249 /sys/firmware/acpi/tables.
250 This option turns off this feature.
251 Note that specifying this option does not affect
252 dynamic table installation which will install SSDT
253 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700254
Lv Zheng4dde5072014-02-11 11:01:52 +0800255 acpica_no_return_repair [HW, ACPI]
256 Disable AML predefined validation mechanism
257 This mechanism can repair the evaluation result to make
258 the return objects more ACPI specification compliant.
259 This option is useful for developers to identify the
260 root cause of an AML interpreter issue when the issue
261 has something to do with the repair mechanism.
262
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700263 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
264 Format: To spoof as Windows 98: ="Microsoft Windows"
265
266 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800267 acpi_osi="string1" # add string1
268 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800269 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800270 acpi_osi=! # disable all built-in OS vendor
271 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700272 acpi_osi= # disable all strings
273
Lv Zheng5dc17982013-07-22 16:08:25 +0800274 'acpi_osi=!' can be used in combination with single or
275 multiple 'acpi_osi="string1"' to support specific OS
276 vendor string(s). Note that such command can only
277 affect the default state of the OS vendor strings, thus
278 it cannot affect the default state of the feature group
279 strings and the current state of the OS vendor strings,
280 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800281 is meaningless. This command is useful when one do not
282 care about the state of the feature group strings which
283 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800284 Examples:
285 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
286 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
287 can make '_OSI("Windows 2000")' TRUE.
288
289 'acpi_osi=' cannot be used in combination with other
290 'acpi_osi=' command lines, the _OSI method will not
291 exist in the ACPI namespace. NOTE that such command can
292 only affect the _OSI support state, thus specifying it
293 multiple times through kernel command line is also
294 meaningless.
295 Examples:
296 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
297 FALSE.
298
Lv Zheng741d8122013-07-22 16:08:36 +0800299 'acpi_osi=!*' can be used in combination with single or
300 multiple 'acpi_osi="string1"' to support specific
301 string(s). Note that such command can affect the
302 current state of both the OS vendor strings and the
303 feature group strings, thus specifying it multiple times
304 through kernel command line is meaningful. But it may
305 still not able to affect the final state of a string if
306 there are quirks related to this string. This command
307 is useful when one want to control the state of the
308 feature group strings to debug BIOS issues related to
309 the OSPM features.
310 Examples:
311 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
312 '_OSI("Module Device")' FALSE.
313 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
314 '_OSI("Module Device")' TRUE.
315 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
316 equivalent to
317 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
318 and
319 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
320 they all will make '_OSI("Windows 2000")' TRUE.
321
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530322 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700323 Override the pmtimer bug detection: force the kernel
324 to assume that this machine's pmtimer latches its value
325 and always returns good values.
326
Randy Dunlap4af94f32009-04-17 18:30:28 -0700327 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
328 Format: { level | edge | high | low }
329
Randy Dunlap4af94f32009-04-17 18:30:28 -0700330 acpi_skip_timer_override [HW,ACPI]
331 Recognize and ignore IRQ0/pin2 Interrupt Override.
332 For broken nForce2 BIOS resulting in XT-PIC timer.
333
334 acpi_sleep= [HW,ACPI] Sleep options
335 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200336 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700337 See Documentation/power/video.txt for information on
338 s3_bios and s3_mode.
339 s3_beep is for debugging; it makes the PC's speaker beep
340 as soon as the kernel's real-mode entry point is called.
341 s4_nohwsig prevents ACPI hardware signature from being
342 used during resume from hibernation.
343 old_ordering causes the ACPI 1.0 ordering of the _PTS
344 control method, with respect to putting devices into
345 low power states, to be enforced (the ACPI 2.0 ordering
346 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200347 nonvs prevents the kernel from saving/restoring the
348 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800349 sci_force_enable causes the kernel to set SCI_EN directly
350 on resume from S1/S3 (which is against the ACPI spec,
351 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700352
353 acpi_use_timer_override [HW,ACPI]
354 Use timer override. For some broken Nvidia NF5 boards
355 that require a timer override, but don't have HPET
356
Luca Tettamanti7e905602009-03-30 00:01:27 +0200357 acpi_enforce_resources= [ACPI]
358 { strict | lax | no }
359 Check for resource conflicts between native drivers
360 and ACPI OperationRegions (SystemIO and SystemMemory
361 only). IO ports and memory declared in ACPI might be
362 used by the ACPI subsystem in arbitrary AML code and
363 can interfere with legacy drivers.
364 strict (default): access to resources claimed by ACPI
365 is denied; legacy drivers trying to access reserved
366 resources will fail to bind to device using them.
367 lax: access to resources claimed by ACPI is allowed;
368 legacy drivers trying to access reserved resources
369 will bind successfully but a warning message is logged.
370 no: ACPI OperationRegions are not marked as reserved,
371 no further checks are performed.
372
Prarit Bhargava00159a22014-01-14 14:21:13 -0500373 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
374 kernels.
375
Randy Dunlap4af94f32009-04-17 18:30:28 -0700376 add_efi_memmap [EFI; X86] Include EFI memory map in
377 kernel's map of available physical RAM.
378
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700379 agp= [AGP]
380 { off | try_unsupported }
381 off: disable AGP support
382 try_unsupported: try to drive unsupported chipsets
383 (may crash computer or cause data corruption)
384
Randy Dunlapbcfde332010-06-07 17:10:38 -0700385 ALSA [HW,ALSA]
386 See Documentation/sound/alsa/alsa-parameters.txt
387
Russell Kingd944d542010-02-20 16:13:29 +0000388 alignment= [KNL,ARM]
389 Allow the default userspace alignment fault handler
390 behaviour to be specified. Bit 0 enables warnings,
391 bit 1 enables fixups, and bit 2 sends a segfault.
392
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200393 align_va_addr= [X86-64]
394 Align virtual addresses by clearing slice [14:12] when
395 allocating a VMA at process creation time. This option
396 gives you up to 3% performance improvement on AMD F15h
397 machines (where it is enabled by default) for a
398 CPU-intensive style benchmark, and it can vary highly in
399 a microbenchmark depending on workload and compiler.
400
Borislav Petkov8360ee22011-11-21 12:10:19 +0100401 32: only for 32-bit processes
402 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200403 on: enable for both 32- and 64-bit processes
404 off: disable for both 32- and 64-bit processes
405
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500406 alloc_snapshot [FTRACE]
407 Allocate the ftrace snapshot buffer on boot up when the
408 main buffer is allocated. This is handy if debugging
409 and you need to use tracing_snapshot() on boot up, and
410 do not want to use tracing_snapshot_alloc() as it needs
411 to be done where GFP_KERNEL allocations are allowed.
412
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100413 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200414 Pass parameters to the AMD IOMMU driver in the system.
415 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900416 fullflush - enable flushing of IO/TLB entries when
417 they are unmapped. Otherwise they are
418 flushed before they will be reused, which
419 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200420 off - do not initialize any AMD IOMMU found in
421 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100422 force_isolation - Force device isolation for all
423 devices. The IOMMU driver is not
424 allowed anymore to lift isolation
425 requirements as needed. This option
426 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900427
Shuah Khanc099cf12012-05-24 15:58:25 -0600428 amd_iommu_dump= [HW,X86-64]
429 Enable AMD IOMMU driver option to dump the ACPI table
430 for AMD IOMMU. With this option enabled, AMD IOMMU
431 driver will print ACPI tables for AMD IOMMU during
432 IOMMU initialization.
433
Linus Torvalds1da177e2005-04-16 15:20:36 -0700434 amijoy.map= [HW,JOY] Amiga joystick support
435 Map of devices attached to JOY0DAT and JOY1DAT
436 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200437 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438
439 analog.map= [HW,JOY] Analog joystick and gamepad support
440 Specifies type or capabilities of an analog joystick
441 connected to one of 16 gameports
442 Format: <type1>,<type2>,..<type16>
443
Randy Dunlapa9913042005-10-23 12:57:11 -0700444 apc= [HW,SPARC]
445 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 Format: noidle
447 Disable APC CPU standby support. SPARCstation-Fox does
448 not play well with APC CPU idle - disable it if you have
449 APC and your system crashes randomly.
450
Randy Dunlapca1eda22009-05-06 16:02:58 -0700451 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700452 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700453 Format: { quiet (default) | verbose | debug }
454 Change the amount of debugging information output
455 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700456
Brian Haleyb0f83b22010-02-04 13:36:50 -0800457 autoconf= [IPV6]
458 See Documentation/networking/ipv6.txt.
459
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400460 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
461 Limit apic dumping. The parameter defines the maximal
462 number of local apics being dumped. Also it is possible
463 to set it to "all" by meaning -- no limit here.
464 Format: { 1 (default) | 2 | ... | all }.
465 The parameter valid if only apic=debug or
466 apic=verbose is specified.
467 Example: apic=debug show_lapic=all
468
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700470 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
473 Format: <io>,<irq>,<nodeID>
474
475 ataflop= [HW,M68k]
476
477 atarimouse= [HW,MOUSE] Atari Mouse
478
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
480 EzKey and similar keyboards
481
482 atkbd.reset= [HW] Reset keyboard during initialization
483
Randy Dunlapa9913042005-10-23 12:57:11 -0700484 atkbd.set= [HW] Select keyboard code set
485 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486
487 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
488 keyboards
489
490 atkbd.softraw= [HW] Choose between synthetic and real raw mode
491 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700492
493 atkbd.softrepeat= [HW]
494 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400496 audit= [KNL] Enable the audit sub-system
497 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500498 0 - kernel audit is disabled and can not be enabled
499 until the next reboot
500 unset - kernel audit is initialized but disabled and
501 will be fully enabled by the userspace auditd.
502 1 - kernel audit is initialized and partially enabled,
503 storing at most audit_backlog_limit messages in
504 RAM until it is fully enabled by the userspace
505 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400506 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400507
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400508 audit_backlog_limit= [KNL] Set the audit queue size limit.
509 Format: <int> (must be >=0)
510 Default: 64
511
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 baycom_epp= [HW,AX25]
513 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700514
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
516 Format: <io>,<mode>
517 See header of drivers/net/hamradio/baycom_par.c.
518
Randy Dunlapa9913042005-10-23 12:57:11 -0700519 baycom_ser_fdx= [HW,AX25]
520 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 Format: <io>,<irq>,<mode>[,<baud>]
522 See header of drivers/net/hamradio/baycom_ser_fdx.c.
523
Randy Dunlapa9913042005-10-23 12:57:11 -0700524 baycom_ser_hdx= [HW,AX25]
525 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 Format: <io>,<irq>,<mode>
527 See header of drivers/net/hamradio/baycom_ser_hdx.c.
528
Paul Gortmaker080506a2013-09-30 13:45:19 -0700529 blkdevparts= Manual partition parsing of block device(s) for
530 embedded devices based on command line input.
531 See Documentation/block/cmdline-partition.txt
532
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700533 boot_delay= Milliseconds to delay each printk during boot.
534 Values larger than 10 seconds (10000) are changed to
535 no delay (0).
536 Format: integer
537
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700538 bootmem_debug [KNL] Enable bootmem allocator debug messages.
539
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700541 bttv.radio= Most important insmod options are available as
542 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200544 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000546 bulk_remove=off [PPC] This parameter disables the use of the pSeries
547 firmware feature for flushing multiple hpte entries
548 at a time.
549
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 c101= [NET] Moxa C101 synchronous serial card
551
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700552 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 Sometimes CPU hardware bugs make them report the cache
554 size incorrectly. The kernel will attempt work arounds
555 to fix known problems, but for some CPUs it is not
556 possible to determine what the correct size should be.
557 This option provides an override for these situations.
558
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100559 ccw_timeout_log [S390]
560 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561
Paul Menage8bab8dd2008-04-04 14:29:57 -0700562 cgroup_disable= [KNL] Disable a particular controller
563 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800564 The effects of cgroup_disable=foo are:
565 - foo isn't auto-mounted if you mount all cgroups in
566 a single hierarchy
567 - foo isn't visible as an individually mountable
568 subsystem
569 {Currently only "memory" controller deal with this and
570 cut the overhead, others just disable the usage. So
571 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700572
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573 checkreqprot [SELINUX] Set initial checkreqprot flag value.
574 Format: { "0" | "1" }
575 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700576 0 -- check protection applied by kernel (includes
577 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 1 -- check protection requested by application.
579 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700580 Value can be changed at runtime via
581 /selinux/checkreqprot.
582
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100583 cio_ignore= [S390]
584 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700585 clk_ignore_unused
586 [CLK]
587 Keep all clocks already enabled by bootloader on,
588 even if no driver has claimed them. This is useful
589 for debug and development, but should not be
590 needed on a platform with proper driver support.
591 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100592
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700593 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700594 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200595 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700596 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200597 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 Format: { pit | tsc | cyclone | pmtmr }
599
John Stultz592913e2010-07-13 17:56:20 -0700600 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700601 Format: <string>
602 Override the default clocksource and use the clocksource
603 with the name specified.
604 Some clocksource names to choose from, depending on
605 the platform:
606 [all] jiffies (this is the base, fallback clocksource)
607 [ACPI] acpi_pm
608 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
609 pxa_timer,timer3,32k_counter,timer0_1
610 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700611 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700612 scx200_hrt on Geode; cyclone on IBM x440
613 [MIPS] MIPS
614 [PARISC] cr16
615 [S390] tod
616 [SH] SuperH
617 [SPARC64] tick
618 [X86-64] hpet,tsc
619
Andi Kleenac72e782008-01-30 13:33:21 +0100620 clearcpuid=BITNUM [X86]
621 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800622 arch/x86/include/asm/cpufeature.h for the valid bit
623 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100624 stable over kernel options, but the vendor specific
625 ones should be.
626 Also note that user programs calling CPUID directly
627 or using the feature without checking anything
628 will still see it. This just prevents it from
629 being used by the kernel or shown in /proc/cpuinfo.
630 Also note the kernel might malfunction if you disable
631 some critical bits.
632
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100633 cma=nn[MG] [ARM,KNL]
634 Sets the size of kernel global memory area for contiguous
635 memory allocations. For more information, see
636 include/linux/dma-contiguous.h
637
Robert Jennings14f966e2009-04-15 05:55:32 +0000638 cmo_free_hint= [PPC] Format: { yes | no }
639 Specify whether pages are marked as being inactive
640 when they are freed. This is used in CMO environments
641 to determine OS memory pressure for page stealing by
642 a hypervisor.
643 Default: yes
644
Marek Szyprowskic7909502011-12-29 13:09:51 +0100645 coherent_pool=nn[KMG] [ARM,KNL]
646 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200647 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100648
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530649 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100650 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100651 Range: 0 - 8192
652 Default: 64
653
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700655 Format:
656 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657
658 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
659 Format: <io>[,<irq>]
660
Randy Dunlapa9913042005-10-23 12:57:11 -0700661 com90xx= [HW,NET]
662 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700663 Format: <io>[,<irq>[,<memstart>]]
664
665 condev= [HW,S390] console device
666 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700667
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 console= [KNL] Output console device and options.
669
670 tty<n> Use the virtual console device <n>.
671
672 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800673 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800675 the form "bbbbpnf", where "bbbb" is the baud rate,
676 "p" is parity ("n", "o", or "e"), "n" is number of
677 bits, and "f" is flow control ("r" for RTS or
678 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700679
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800680 See Documentation/serial-console.txt for more
681 information. See
682 Documentation/networking/netconsole.txt for an
683 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700685 uart[8250],io,<addr>[,options]
686 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 Start an early, polled-mode console on the 8250/16550
688 UART at the specified I/O port or MMIO address,
689 switching to the matching ttyS device later. The
690 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500691 hvc<n> Use the hypervisor console device <n>. This is for
692 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700694 If the device connected to the port is not a TTY but a braille
695 device, prepend "brl," before the device type, for instance
696 console=brl,ttyS0
697 For now, only VisioBraille is supported.
698
Daniel Mackf324edc2009-06-16 15:33:52 -0700699 consoleblank= [KNL] The console blank (screen saver) timeout in
700 seconds. Defaults to 10*60 = 10mins. A value of 0
701 disables the blank timer.
702
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800703 coredump_filter=
704 [KNL] Change the default value for
705 /proc/<pid>/coredump_filter.
706 See also Documentation/filesystems/proc.txt.
707
Len Brown62027ae2011-04-01 18:13:10 -0400708 cpuidle.off=1 [CPU_IDLE]
709 disable the cpuidle sub-system
710
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700712 Format:
713 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800715 crashkernel=size[KMG][@offset[KMG]]
716 [KNL] Using kexec, Linux can switch to a 'crash kernel'
717 upon panic. This parameter reserves the physical
718 memory region [offset, offset + size] for that kernel
719 image. If '@offset' is omitted, then a suitable offset
720 is selected automatically. Check
721 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700722
Bernhard Wallefb391592007-10-18 23:41:02 -0700723 crashkernel=range1:size1[,range2:size2,...][@offset]
724 [KNL] Same as above, but depends on the memory
725 in the running system. The syntax of range is
726 start-[end] where start and end are both
727 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800728 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700729
Yinghai Luadbc7422013-04-15 22:23:48 -0700730 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700731 [KNL, x86_64] range could be above 4G. Allow kernel
732 to allocate physical memory region from top, so could
733 be above 4G if system have more than 4G ram installed.
734 Otherwise memory region will be allocated below 4G, if
735 available.
736 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700737 crashkernel=size[KMG],low
738 [KNL, x86_64] range under 4G. When crashkernel=X,high
739 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700740 above 4G, that cause second kernel crash on system
741 that require some amount of low memory, e.g. swiotlb
742 requires at least 64M+32K low memory. Kernel would
743 try to allocate 72M below 4G automatically.
744 This one let user to specify own low range under 4G
745 for second kernel instead.
746 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700747 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700748 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700749
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750 cs89x0_dma= [HW,NET]
751 Format: <dma>
752
753 cs89x0_media= [HW,NET]
754 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700755
Randy Dunlapa9913042005-10-23 12:57:11 -0700756 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 See header of drivers/s390/block/dasd_devmap.c.
758
759 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
760 (one device per port)
761 Format: <port#>,<type>
762 See also Documentation/input/joystick-parport.txt
763
Thomas Renningera648ec02010-08-06 16:11:02 +0200764 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
765 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600766 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200767
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 debug [KNL] Enable kernel debugging (events log level).
769
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700770 debug_locks_verbose=
771 [KNL] verbose self-tests
772 Format=<0|1>
773 Print debugging info while doing the locking API
774 self-tests.
775 We default to 0 (no extra messages), setting it to
776 1 will print _a lot_ more information - normally
777 only useful to kernel developers.
778
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700779 debug_objects [KNL] Enable object debugging
780
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500781 no_debug_objects
782 [KNL] Disable object debugging
783
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800784 debug_guardpage_minorder=
785 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
786 parameter allows control of the order of pages that will
787 be intentionally kept free (and hence protected) by the
788 buddy allocator. Bigger value increase the probability
789 of catching random memory corruption, but reduce the
790 amount of memory for normal system use. The maximum
791 possible value is MAX_ORDER/2. Setting this parameter
792 to 1 or 2 should be enough to identify most random
793 memory corruption problems caused by bugs in kernel or
794 driver code when a CPU writes to (or reads from) a
795 random memory location. Note that there exists a class
796 of memory corruptions problems caused by buggy H/W or
797 F/W or by drivers badly programing DMA (basically when
798 memory is written at bus level and the CPU MMU is
799 bypassed) which are not detectable by
800 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
801 tracking down these problems.
802
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200803 debugpat [X86] Enable PAT debugging
804
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200805 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 Format: <area>[,<node>]
807 See also Documentation/networking/decnet.txt.
808
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700809 default_hugepagesz=
810 [same as hugepagesz=] The size of the default
811 HugeTLB page size. This is the size represented by
812 the legacy /proc/ hugepages APIs, used for SHM, and
813 default size when mounting hugetlbfs filesystems.
814 Defaults to the default architecture's huge page size
815 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700816
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817 dhash_entries= [KNL]
818 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700819
Brian Haleyb0f83b22010-02-04 13:36:50 -0800820 disable= [IPV6]
821 See Documentation/networking/ipv6.txt.
822
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900823 disable_cpu_apicid= [X86,APIC,SMP]
824 Format: <int>
825 The number of initial APIC ID for the
826 corresponding CPU to be disabled at boot,
827 mostly used for the kdump 2nd kernel to
828 disable BSP to wake up multiple CPUs without
829 causing system reset or hang due to sending
830 INIT from AP to BSP.
831
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000832 disable_ddw [PPC/PSERIES]
833 Disable Dynamic DMA Window support. Use this if
834 to workaround buggy firmware.
835
Brian Haleyb0f83b22010-02-04 13:36:50 -0800836 disable_ipv6= [IPV6]
837 See Documentation/networking/ipv6.txt.
838
Yinghai Lu95ffa242008-04-29 03:52:33 -0700839 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700840 The kernel tries to adjust MTRR layout from continuous
841 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700842 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700843
Yinghai Lu093af8d2008-01-30 13:33:32 +0100844 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100845 By default the kernel will trim any uncacheable
846 memory out of your available memory pool based on
847 MTRR settings. This parameter disables that behavior,
848 possibly causing your machine to run very slowly.
849
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530850 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700851 Disable PIN 1 of APIC timer
852 Can be useful to work around chipset bugs.
853
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700854 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
855 this option disables the debugging code at boot.
856
857 dma_debug_entries=<number>
858 This option allows to tune the number of preallocated
859 entries for DMA-API debugging code. One entry is
860 required per DMA-API allocation. Use this if the
861 DMA-API debugging code disables itself because the
862 architectural default is too low.
863
Joerg Roedel1745de52009-05-22 21:49:51 +0200864 dma_debug_driver=<driver_name>
865 With this option the DMA-API debugging driver
866 filter feature can be enabled at boot time. Just
867 pass the driver to filter for as the parameter.
868 The filter can be disabled or changed to another
869 driver later using sysfs.
870
Carsten Emdeda0df922012-03-18 22:37:33 +0100871 drm_kms_helper.edid_firmware=[<connector>:]<file>
872 Broken monitors, graphic adapters and KVMs may
873 send no or incorrect EDID data sets. This parameter
874 allows to specify an EDID data set in the
875 /lib/firmware directory that is used instead.
876 Generic built-in EDID data sets are used, if one of
877 edid/1024x768.bin, edid/1280x1024.bin,
878 edid/1680x1050.bin, or edid/1920x1080.bin is given
879 and no file with the same name exists. Details and
880 instructions how to build your own EDID data are
881 available in Documentation/EDID/HOWTO.txt. An EDID
882 data set will only be used for a particular connector,
883 if its name and a colon are prepended to the EDID
884 name.
885
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886 dscc4.setup= [NET]
887
Jim Cromie29e36c92012-04-27 14:30:41 -0600888 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
889 module.dyndbg[="val"]
890 Enable debug messages at boot time. See
891 Documentation/dynamic-debug-howto.txt for details.
892
Mark Salter56aeeba2014-04-07 15:39:53 -0700893 early_ioremap_debug [KNL]
894 Enable debug messages in early_ioremap support. This
895 is useful for tracking down temporary early mappings
896 which are not unmapped.
897
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700898 earlycon= [KNL] Output early console device and options.
899 uart[8250],io,<addr>[,options]
900 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700901 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700902 Start an early, polled-mode console on the 8250/16550
903 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700904 MMIO inter-register address stride is either 8-bit
905 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700906 The options are the same as for ttyS, above.
907
Dave Hansen147ea092013-04-10 14:03:38 -0700908 earlyprintk= [X86,SH,BLACKFIN,ARM]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100910 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500911 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700913 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500914 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500915 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916
Dave Hansen147ea092013-04-10 14:03:38 -0700917 earlyprintk is useful when the kernel crashes before
918 the normal console is initialized. It is not enabled by
919 default because it has some cosmetic problems.
920
Randy Dunlapa9913042005-10-23 12:57:11 -0700921 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 takes over.
923
Matt Fleming72548e82013-10-04 09:36:56 +0100924 Only one of vga, efi, serial, or usb debug port can
925 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926
Dave Hansen147ea092013-04-10 14:03:38 -0700927 Currently only ttyS0 and ttyS1 may be specified by
928 name. Other I/O ports may be explicitly specified
929 on some architectures (x86 and arm at least) by
930 replacing ttySn with an I/O port address, like this:
931 earlyprintk=serial,0x1008,115200
932 You can find the port for a given device in
933 /proc/tty/driver/serial:
934 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935
936 Interaction with the standard serial driver is not
937 very good.
938
Matt Fleming72548e82013-10-04 09:36:56 +0100939 The VGA and EFI output is eventually overwritten by
940 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500942 The xen output can only be used by Xen PV guests.
943
Chen, Gongc700f012013-12-06 01:17:08 -0500944 edac_report= [HW,EDAC] Control how to report EDAC event
945 Format: {"on" | "off" | "force"}
946 on: enable EDAC to report H/W event. May be overridden
947 by other higher priority error reporting module.
948 off: disable H/W event reporting through EDAC.
949 force: enforce the use of EDAC to report H/W event.
950 default: on.
951
Jason Wessel97311912010-05-20 21:04:30 -0500952 ekgdboc= [X86,KGDB] Allow early kernel console debugging
953 ekgdboc=kbd
954
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300955 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500956 the boot argument: earlyprintk=vga
957
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700959 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +0100961 efi= [EFI]
962 Format: { "old_map" }
963 old_map [X86-64]: switch to the old ioremap-based EFI
964 runtime services mapping. 32-bit still uses this one by
965 default.
966
Richard Weinberger8c58bf32013-04-17 01:00:53 +0200967 efi_no_storage_paranoia [EFI; X86]
968 Using this parameter you can use more than 50% of
969 your efi variable storage. Use this parameter only if
970 you are really sure that your UEFI does sane gc and
971 fulfills the spec otherwise your board may brick.
972
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973 eisa_irq_edge= [PARISC,HW]
974 See header of drivers/parisc/eisa.c.
975
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700976 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700978 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979
980 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100981 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200982 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700983 Documentation/block/deadline-iosched.txt for details.
984
Michael Holzheud3bf37952011-10-30 15:16:37 +0100985 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700986 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100987 image elf header and optionally the size. Generally
988 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800989 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700991 enable_mtrr_cleanup [X86]
992 The kernel tries to adjust MTRR layout from continuous
993 to discrete, to make X server driver able to add WB
994 entry later. This parameter enables that.
995
Randy Dunlapca1eda22009-05-06 16:02:58 -0700996 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700997 Enable PIN 1 of APIC timer
998 Can be useful to work around chipset bugs
999 (in particular on some ATI chipsets).
1000 The kernel tries to set a reasonable default.
1001
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002 enforcing [SELINUX] Set initial enforcing status.
1003 Format: {"0" | "1"}
1004 See security/selinux/Kconfig help text.
1005 0 -- permissive (log only, no denials).
1006 1 -- enforcing (deny and log).
1007 Default value is 0.
1008 Value can be changed at runtime via /selinux/enforce.
1009
Huang Yinga08f82d2010-05-18 14:35:21 +08001010 erst_disable [ACPI]
1011 Disable Error Record Serialization Table (ERST)
1012 support.
1013
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 ether= [HW,NET] Ethernet cards parameters
1015 This option is obsoleted by the "netdev=" option, which
1016 has equivalent usage. See its documentation for details.
1017
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001018 evm= [EVM]
1019 Format: { "fix" }
1020 Permit 'security.evm' to be updated regardless of
1021 current integrity status.
1022
Akinobu Mitade1ba092006-12-08 02:39:42 -08001023 failslab=
1024 fail_page_alloc=
1025 fail_make_request=[KNL]
1026 General fault injection mechanism.
1027 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001028 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001029
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001031 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032
Alex Chiangf13ae302008-05-08 14:03:23 -06001033 force_pal_cache_flush
1034 [IA-64] Avoid check_sal_cache_flush which may hang on
1035 buggy SAL_CACHE_FLUSH implementations. Using this
1036 parameter will force ia64_sal_cache_flush to call
1037 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1038
Chris Bainbridge69f23662014-03-07 18:40:42 +07001039 forcepae [X86-32]
1040 Forcefully enable Physical Address Extension (PAE).
1041 Many Pentium M systems disable PAE but may have a
1042 functionally usable PAE implementation.
1043 Warning: use of this parameter will taint the kernel
1044 and may cause unknown problems.
1045
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001046 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001047 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001048 as early as possible in order to facilitate early
1049 boot debugging.
1050
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001051 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001052 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001053 If no parameter is passed, ftrace will dump
1054 buffers of all CPUs, but if you pass orig_cpu, it will
1055 dump only the buffer of the CPU that triggered the
1056 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001057
1058 ftrace_filter=[function-list]
1059 [FTRACE] Limit the functions traced by the function
1060 tracer at boot up. function-list is a comma separated
1061 list of functions. This list can be changed at run
1062 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001063 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001064
1065 ftrace_notrace=[function-list]
1066 [FTRACE] Do not trace the functions specified in
1067 function-list. This list can be changed at run time
1068 by the set_ftrace_notrace file in the debugfs
1069 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001070
Stefan Assmann369bc182009-10-12 22:17:21 +02001071 ftrace_graph_filter=[function-list]
1072 [FTRACE] Limit the top level callers functions traced
1073 by the function graph tracer at boot up.
1074 function-list is a comma separated list of functions
1075 that can be changed at run time by the
1076 set_graph_function file in the debugfs tracing directory.
1077
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 gamecon.map[2|3]=
1079 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1080 support via parallel port (up to 5 devices per port)
1081 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1082 See also Documentation/input/joystick-parport.txt
1083
1084 gamma= [HW,DRM]
1085
Yinghai Luaaf23042008-01-30 13:33:09 +01001086 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1087 Format: off | on
1088 default: on
1089
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001090 gcov_persist= [GCOV] When non-zero (default), profiling data for
1091 kernel modules is saved and remains accessible via
1092 debugfs, even when the module is unloaded/reloaded.
1093 When zero, profiling data is discarded and associated
1094 debugfs files are removed at module unload time.
1095
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001097 invalid Protective MBR to be treated as GPT. If the
1098 primary GPT is corrupted, it enables the backup/alternate
1099 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001101 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1102 the "Enable 0" bit of the configuration register.
1103 Format: 0 | 1
1104 Default: 0
1105 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1106 the "Enable 0" bit of the configuration register.
1107 Format: 0 | 1
1108 Default: 0
1109 grcan.select= [HW] Select which physical interface to use.
1110 Format: 0 | 1
1111 Default: 0
1112 grcan.txsize= [HW] Sets the size of the tx buffer.
1113 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1114 Default: 1024
1115 grcan.rxsize= [HW] Sets the size of the rx buffer.
1116 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1117 Default: 1024
1118
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 hashdist= [KNL,NUMA] Large hashes allocated during boot
1120 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001121 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001122 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001123
1124 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1125
1126 hd= [EIDE] (E)IDE hard drive subsystem geometry
1127 Format: <cyl>,<head>,<sect>
1128
Huang Yingea8c0712010-05-18 14:35:15 +08001129 hest_disable [ACPI]
1130 Disable Hardware Error Source Table (HEST) support;
1131 corresponding firmware-first mode error processing
1132 logic will be disabled.
1133
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1135 size of <nn>. This works even on boxes that have no
1136 highmem otherwise. This also works to reduce highmem
1137 size on bigger boxes.
1138
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001139 highres= [KNL] Enable/disable high resolution timer mode.
1140 Valid parameters: "on", "off"
1141 Default: "on"
1142
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143 hisax= [HW,ISDN]
1144 See Documentation/isdn/README.HiSax.
1145
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001146 hlt [BUGS=ARM,SH]
1147
1148 hpet= [X86-32,HPET] option to control HPET usage
1149 Format: { enable (default) | disable | force |
1150 verbose }
1151 disable: disable HPET and use PIT instead
1152 force: allow force enabled of undocumented chips (ICH4,
1153 VIA, nVidia)
1154 verbose: show contents of HPET registers during setup
1155
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001156 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1157 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1158
Andi Kleenb4718e62008-07-23 21:27:51 -07001159 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1160 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001161 On x86-64 and powerpc, this option can be specified
1162 multiple times interleaved with hugepages= to reserve
1163 huge pages of different sizes. Valid pages sizes on
1164 x86-64 are 2M (when the CPU supports "pse") and 1G
1165 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001166 Note that 1GB pages can only be allocated at boot time
1167 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001168
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001169 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1170 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001171 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1172 If specified, z/VM IUCV HVC accepts connections
1173 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001174
James Hoganfdabf522012-10-09 11:00:27 +01001175 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1176 hardware thread id mappings.
1177 Format: <cpu>:<hwthread>
1178
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001179 keep_bootcon [KNL]
1180 Do not unregister boot console at start. This is only
1181 useful for debugging when something happens in the window
1182 between unregistering the boot console and initializing
1183 the real console.
1184
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001185 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001186 or register an additional I2C bus that is not
1187 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001188 Format:
1189 <bus_id>,<clkrate>
1190
Jiri Kosina36d95732008-10-06 02:51:09 -04001191 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001192 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001193 i8042.dumbkbd [HW] Pretend that controller can only read data from
1194 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 (Don't attempt to blink the leds)
1196 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001197 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001198 i8042.noloop [HW] Disable the AUX Loopback command while probing
1199 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200 i8042.nomux [HW] Don't check presence of an active multiplexing
1201 controller
1202 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1203 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001204 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205 i8042.reset [HW] Reset the controller during init and cleanup
1206 i8042.unlock [HW] Unlock (ignore) the keylock
1207
1208 i810= [HW,DRM]
1209
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001210 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1211 indicates that the driver is running on unsupported
1212 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001213 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1214 does not match list of supported models.
1215 i8k.power_status
1216 [HW] Report power status in /proc/i8k
1217 (disabled by default)
1218 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1219 capability is set.
1220
Carsten Emde4dca20e2012-03-15 15:56:26 +01001221 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001222 [DRM] Invert the sense of the variable that is used to
1223 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001224 brightness value of 0 indicates backlight switched off,
1225 and the maximum of the brightness value sets the backlight
1226 to maximum brightness. If this parameter is set to 0
1227 (default) and the machine requires it, or this parameter
1228 is set to 1, a brightness value of 0 sets the backlight
1229 to maximum brightness, and the maximum of the brightness
1230 value switches the backlight off.
1231 -1 -- never invert brightness
1232 0 -- machine default
1233 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001234
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235 icn= [HW,ISDN]
1236 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1237
David Fries0af80c02009-02-25 20:28:21 +01001238 ide-core.nodma= [HW] (E)IDE subsystem
1239 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001240 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1241 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001242 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001244 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1245 Claim all unknown PCI IDE storage controllers.
1246
Andi Kleenf039b752007-05-02 19:27:12 +02001247 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001248 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001249 Poll forces a polling idle loop that can slightly
1250 improve the performance of waking up a idle CPU, but
1251 will use a lot of power and make the system run hot.
1252 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001253 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001254 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001255 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001256
Ingo Molnar792908222006-12-06 20:40:51 -08001257 ignore_loglevel [KNL]
1258 Ignore loglevel setting - this will print /all/
1259 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001260 We also add it as printk module parameter, so users
1261 could change it dynamically, usually by
1262 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 ihash_entries= [KNL]
1265 Set number of hash buckets for inode cache.
1266
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001267 ima_appraise= [IMA] appraise integrity measurements
1268 Format: { "off" | "enforce" | "fix" }
1269 default: "enforce"
1270
Mimi Zohar07f6a792011-03-09 22:25:48 -05001271 ima_appraise_tcb [IMA]
1272 The builtin appraise policy appraises all files
1273 owned by uid=0.
1274
Mimi Zohar3323eec2009-02-04 09:06:58 -05001275 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001276 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1277 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001278 default: "sha1"
1279
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001280 The list of supported hash algorithms is defined
1281 in crypto/hash_info.h.
1282
Eric Paris5789ba32009-05-21 15:47:06 -04001283 ima_tcb [IMA]
1284 Load a policy which meets the needs of the Trusted
1285 Computing Base. This means IMA will measure all
1286 programs exec'd, files mmap'd for exec, and all files
1287 opened for read by uid=0.
1288
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001289 ima_template= [IMA]
1290 Select one of defined IMA measurements template formats.
1291 Formats: { "ima" | "ima-ng" }
1292 Default: "ima-ng"
1293
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294 init= [KNL]
1295 Format: <full_path>
1296 Run specified binary instead of /sbin/init as init
1297 process.
1298
1299 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1300 for working out where the kernel is dying during
1301 startup.
1302
1303 initrd= [BOOT] Specify the location of the initial ramdisk
1304
1305 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1306 Format: <irq>
1307
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001308 int_pln_enable [x86] Enable power limit notification interrupt
1309
Mimi Zohard726d8d2013-03-18 14:48:02 -04001310 integrity_audit=[IMA]
1311 Format: { "0" | "1" }
1312 0 -- basic integrity auditing messages. (Default)
1313 1 -- additional integrity auditing messages.
1314
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001315 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001316 on
1317 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001318 off
1319 Disable intel iommu driver.
1320 igfx_off [Default Off]
1321 By default, gfx is mapped as normal device. If a gfx
1322 device has a dedicated DMAR unit, the DMAR unit is
1323 bypassed by not enabling DMAR with this option. In
1324 this case, gfx device will use physical address for
1325 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001326 forcedac [x86_64]
1327 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001328 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001329 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001330 than 32-bit addressing. The default is to look
1331 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001332 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001333 strict [Default Off]
1334 With this option on every unmap_single operation will
1335 result in a hardware IOTLB flush operation as opposed
1336 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001337 sp_off [Default Off]
1338 By default, super page will be supported if Intel IOMMU
1339 has the capability. With this option, super page will
1340 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001341
1342 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1343 0 disables intel_idle and fall back on acpi_idle.
1344 1 to 6 specify maximum depth of C-state.
1345
Dirk Brandewie6be26492013-02-15 22:55:10 +01001346 intel_pstate= [X86]
1347 disable
1348 Do not enable intel_pstate as the default
1349 scaling driver for the supported processors
1350
Chris Wrightd1423d52010-07-20 11:06:49 -07001351 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001352 on enable Interrupt Remapping (default)
1353 off disable Interrupt Remapping
1354 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001355 no_x2apic_optout
1356 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001357
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001358 iomem= Disable strict checking of access to MMIO memory
1359 strict regions from userspace.
1360 relaxed
1361
1362 iommu= [x86]
1363 off
1364 force
1365 noforce
1366 biomerge
1367 panic
1368 nopanic
1369 merge
1370 nomerge
1371 forcesac
1372 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001373 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001374
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001375
1376 io7= [HW] IO7 for Marvel based alpha systems
1377 See comment before marvel_specify_io7 in
1378 arch/alpha/kernel/core_marvel.c.
1379
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301380 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001381 0x80
1382 Standard port 0x80 based delay
1383 0xed
1384 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001385 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001386 Simple two microseconds delay
1387 none
1388 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001389
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001391 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392
1393 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001394 See comment before ip2_setup() in
1395 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396
Alan Cox200803d2005-06-28 20:45:18 -07001397 irqfixup [HW]
1398 When an interrupt is not handled search all handlers
1399 for it. Intended to get systems with badly broken
1400 firmware running.
1401
1402 irqpoll [HW]
1403 When an interrupt is not handled search all handlers
1404 for it. Also check all handlers each timer
1405 interrupt. Intended to get systems with badly broken
1406 firmware running.
1407
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001409 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001410
1411 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001412 Format:
1413 <cpu number>,...,<cpu number>
1414 or
Li Zefanb225d442008-11-06 12:53:39 -08001415 <cpu number>-<cpu number>
1416 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001417 or a mixture
1418 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001419
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 This option can be used to specify one or more CPUs
1421 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001422 algorithms. You can move a process onto or off an
1423 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 <cpu number> begins at 0 and the maximum value is
1425 "number of CPUs in system - 1".
1426
1427 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001428 alternative -- manually setting the CPU mask of all
1429 tasks in the system -- can cause problems and
1430 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431
Randy Dunlapa9913042005-10-23 12:57:11 -07001432 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001434 ivrs_ioapic [HW,X86_64]
1435 Provide an override to the IOAPIC-ID<->DEVICE-ID
1436 mapping provided in the IVRS ACPI table. For
1437 example, to map IOAPIC-ID decimal 10 to
1438 PCI device 00:14.0 write the parameter as:
1439 ivrs_ioapic[10]=00:14.0
1440
1441 ivrs_hpet [HW,X86_64]
1442 Provide an override to the HPET-ID<->DEVICE-ID
1443 mapping provided in the IVRS ACPI table. For
1444 example, to map HPET-ID decimal 0 to
1445 PCI device 00:14.0 write the parameter as:
1446 ivrs_hpet[0]=00:14.0
1447
Linus Torvalds1da177e2005-04-16 15:20:36 -07001448 js= [HW,JOY] Analog joystick
1449 See Documentation/input/joystick.txt.
1450
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001451 keepinitrd [HW,ARM]
1452
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301453 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001454 specifies the amount of memory usable by the kernel
1455 for non-movable allocations. The requested amount is
1456 spread evenly throughout all nodes in the system. The
1457 remaining memory in each node is used for Movable
1458 pages. In the event, a node is too small to have both
1459 kernelcore and Movable pages, kernelcore pages will
1460 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001461 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001462 allocation of pages that may be reclaimed or moved
1463 by the page migration subsystem. This means that
1464 HugeTLB pages may not be allocated from this zone.
1465 Note that allocations like PTEs-from-HighMem still
1466 use the HighMem zone if it exists, and the Normal
1467 zone if it does not.
1468
Jason Wessel4fe1da42010-05-20 21:04:31 -05001469 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1470 Format: <Controller#>[,poll interval]
1471 The controller # is the number of the ehci usb debug
1472 port as it is probed via PCI. The poll interval is
1473 optional and is the number seconds in between
1474 each poll cycle to the debug port in case you need
1475 the functionality for interrupting the kernel with
1476 gdb or control-c on the dbgp connection. When
1477 not using this parameter you use sysrq-g to break into
1478 the kernel debugger.
1479
Jason Wessel84c08fd2010-05-20 21:04:24 -05001480 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001481 Requires a tty driver that supports console polling,
1482 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001483 Serial only format: <serial_device>[,baud]
1484 keyboard only format: kbd
1485 keyboard and serial format: kbd,<serial_device>[,baud]
1486 Optional Kernel mode setting:
1487 kms, kbd format: kms,kbd
1488 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001489
Jason Wessel84c08fd2010-05-20 21:04:24 -05001490 kgdbwait [KGDB] Stop kernel execution and enter the
1491 kernel debugger at the earliest opportunity.
1492
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001493 kmac= [MIPS] korina ethernet MAC address.
1494 Configure the RouterBoard 532 series on-chip
1495 Ethernet adapter MAC address.
1496
Catalin Marinas04f70332009-06-11 13:22:39 +01001497 kmemleak= [KNL] Boot-time kmemleak enable/disable
1498 Valid arguments: on, off
1499 Default: on
1500
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001501 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1502 Valid arguments: 0, 1, 2
1503 kmemcheck=0 (disabled)
1504 kmemcheck=1 (enabled)
1505 kmemcheck=2 (one-shot mode)
1506 Default: 2 (one-shot mode)
1507
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301508 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001509 in oops dumps.
1510
Andre Przywarafef07aa2009-07-10 14:20:35 +02001511 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1512 Default is 0 (don't ignore, but inject #GP)
1513
Xiao Guangronga182d872010-09-20 22:17:48 +08001514 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1515 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001516 Default is 0 (off)
1517
Andre Przywarafef07aa2009-07-10 14:20:35 +02001518 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001519 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001520
1521 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1522 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001523 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001524
Andre Przywarafef07aa2009-07-10 14:20:35 +02001525 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1526 (virtualized MMU) support on capable Intel chips.
1527 Default is 1 (enabled)
1528
1529 kvm-intel.emulate_invalid_guest_state=
1530 [KVM,Intel] Enable emulation of invalid guest states
1531 Default is 0 (disabled)
1532
1533 kvm-intel.flexpriority=
1534 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1535 Default is 1 (enabled)
1536
Sasha Levine1a72ae2011-08-09 14:28:35 +03001537 kvm-intel.nested=
1538 [KVM,Intel] Enable VMX nesting (nVMX).
1539 Default is 0 (disabled)
1540
Andre Przywarafef07aa2009-07-10 14:20:35 +02001541 kvm-intel.unrestricted_guest=
1542 [KVM,Intel] Disable unrestricted guest feature
1543 (virtualized real and unpaged mode) on capable
1544 Intel chips. Default is 1 (enabled)
1545
1546 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1547 feature (tagged TLBs) on capable Intel chips.
1548 Default is 1 (enabled)
1549
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550 l2cr= [PPC]
1551
Robert Brosea78bfbf2008-03-29 07:20:23 +11001552 l3cr= [PPC]
1553
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001554 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001555 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556
Suresh Siddha279f1462012-10-22 14:37:58 -07001557 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1558 value for LAPIC timer one-shot implementation. Default
1559 back to the programmable timer unit in the LAPIC.
1560
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301561 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001562 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001563
FD Camifcb71f62008-01-06 19:08:56 +01001564 libata.dma= [LIBATA] DMA control
1565 libata.dma=0 Disable all PATA and SATA DMA
1566 libata.dma=1 PATA and SATA Disk DMA only
1567 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001568 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001569 Combinations also work, so libata.dma=3 enables DMA
1570 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001571
Michael Prokop20308872009-08-06 00:14:10 +02001572 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1573 libata.ignore_hpa=0 keep BIOS limits (default)
1574 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001575
Dave Jones78e70c22007-09-27 11:50:13 -04001576 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1577 when set.
1578 Format: <int>
1579
Tejun Heo33267322008-02-13 09:15:09 +09001580 libata.force= [LIBATA] Force configurations. The format is comma
1581 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001582 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001583 matching port, link or device. Basically, it matches
1584 the ATA ID string printed on console by libata. If
1585 the whole ID part is omitted, the last PORT and DEVICE
1586 values are used. If ID hasn't been specified yet, the
1587 configuration applies to all ports, links and devices.
1588
1589 If only DEVICE is omitted, the parameter applies to
1590 the port and all links and devices behind it. DEVICE
1591 number of 0 either selects the first device or the
1592 first fan-out link behind PMP device. It does not
1593 select the host link. DEVICE number of 15 selects the
1594 host link and device attached to it.
1595
1596 The VAL specifies the configuration to force. As long
1597 as there's no ambiguity shortcut notation is allowed.
1598 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1599 The following configurations can be forced.
1600
1601 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1602 Any ID with matching PORT is used.
1603
1604 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1605
1606 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1607 udma[/][16,25,33,44,66,100,133] notation is also
1608 allowed.
1609
1610 * [no]ncq: Turn on or off NCQ.
1611
Tejun Heo05944bd2008-08-13 20:19:09 +09001612 * nohrst, nosrst, norst: suppress hard, soft
1613 and both resets.
1614
Dan Williamsca6d43b2012-06-21 23:41:41 -07001615 * rstonce: only attempt one reset during
1616 hot-unplug link recovery
1617
Tejun Heo43c9c592010-05-23 12:59:11 +02001618 * dump_id: dump IDENTIFY data.
1619
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001620 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1621
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001622 * disable: Disable this device.
1623
Tejun Heo33267322008-02-13 09:15:09 +09001624 If there are multiple matching configurations changing
1625 the same attribute, the last one is used.
1626
Yinghai Lu95f72d12010-07-12 14:36:09 +10001627 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001628
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001630 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001632 lockd.nlm_grace_period=P [NFS] Assign grace period.
1633 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001635 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1636 Format: <integer>
1637
1638 lockd.nlm_timeout=T [NFS] Assign timeout value.
1639 Format: <integer>
1640
1641 lockd.nlm_udpport=M [NFS] Assign UDP port.
1642 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643
1644 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1645 Format: <irq>
1646
1647 loglevel= All Kernel Messages with a loglevel smaller than the
1648 console loglevel will be printed to the console. It can
1649 also be changed with klogd or other programs. The
1650 loglevels are defined as follows:
1651
1652 0 (KERN_EMERG) system is unusable
1653 1 (KERN_ALERT) action must be taken immediately
1654 2 (KERN_CRIT) critical conditions
1655 3 (KERN_ERR) error conditions
1656 4 (KERN_WARNING) warning conditions
1657 5 (KERN_NOTICE) normal but significant condition
1658 6 (KERN_INFO) informational
1659 7 (KERN_DEBUG) debug-level messages
1660
Randy Dunlapc756d082011-02-20 20:08:35 -08001661 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1662 in bytes. n must be a power of two. The default
1663 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664
Randy Dunlapaccaa242007-10-16 01:29:37 -07001665 logo.nologo [FB] Disables display of the built-in Linux logo.
1666 This may be used to provide more screen space for
1667 kernel log messages and is useful when debugging
1668 kernel boot problems.
1669
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670 lp=0 [LP] Specify parallel ports to use, e.g,
1671 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1672 lp=reset first parallel port). 'lp=0' disables the
1673 lp=auto printer driver. 'lp=reset' (which can be
1674 specified in addition to the ports) causes
1675 attached printers to be reset. Using
1676 lp=port1,port2,... specifies the parallel ports
1677 to associate lp devices with, starting with
1678 lp0. A port specification may be 'none' to skip
1679 that lp device, or a parport name such as
1680 'parport0'. Specifying 'lp=auto' instead of a
1681 port specification list means that device IDs
1682 from each port should be examined, to see if
1683 an IEEE 1284-compliant printer is attached; if
1684 so, the driver will manage that printer.
1685 See also header of drivers/char/lp.c.
1686
1687 lpj=n [KNL]
1688 Sets loops_per_jiffy to given constant, thus avoiding
1689 time-consuming boot-time autodetection (up to 250 ms per
1690 CPU). 0 enables autodetection (default). To determine
1691 the correct value for your kernel, boot with normal
1692 autodetection and see what value is printed. Note that
1693 on SMP systems the preset will be applied to all CPUs,
1694 which is likely to cause problems if your CPUs need
1695 significantly divergent settings. An incorrect value
1696 will cause delays in the kernel to be wrong, leading to
1697 unpredictable I/O errors and other breakage. Although
1698 unlikely, in the extreme case this might damage your
1699 hardware.
1700
1701 ltpc= [NET]
1702 Format: <io>,<irq>,<dma>
1703
Randy Dunlap16290242011-08-13 12:34:52 -07001704 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001705 (machvec) in a generic kernel.
1706 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707
Wu Zhangjin3209e702009-07-02 23:27:12 +08001708 machtype= [Loongson] Share the same kernel image file between different
1709 yeeloong laptop.
1710 Example: machtype=lemote-yeeloong-2f-7inch
1711
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001712 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1713 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714
1715 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001716 should make use of. maxcpus=n : n >= 0 limits the
1717 kernel to using 'n' processors. n=0 is a special case,
1718 it is equivalent to "nosmp", which also disables
1719 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720
Kay Sieversd134b002011-07-31 22:08:04 +02001721 max_loop= [LOOP] The number of loop block devices that get
1722 (loop.max_loop) unconditionally pre-created at init time. The default
1723 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1724 of statically allocating a predefined number, loop
1725 devices can be requested on-demand with the
1726 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001727
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001728 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729
Uwe Hermann71cced62008-10-20 09:32:21 -07001730 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001731
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 md= [HW] RAID subsystems devices and level
1733 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001734
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735 mdacon= [MDA]
1736 Format: <first>,<last>
1737 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001738
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1740 Amount of memory to be used when the kernel is not able
1741 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001742 [X86] Work as limiting max address. Use together
1743 with memmap= to avoid physical address space collisions.
1744 Without memmap= PCI devices could be placed at addresses
1745 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001747 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001748 memory.
1749
Paul Mundt6902aa82008-09-21 17:14:42 +09001750 memchunk=nn[KMG]
1751 [KNL,SH] Allow user to override the default size for
1752 per-device physically contiguous DMA buffers.
1753
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301754 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 E820 memory map, as specified by the user.
1756 Such memmap=exactmap lines can be constructed based on
1757 BIOS output or other requirements. See the memmap=nn@ss
1758 option description.
1759
1760 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001761 [KNL] Force usage of a specific region of memory.
1762 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001763
1764 memmap=nn[KMG]#ss[KMG]
1765 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001766 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001767
1768 memmap=nn[KMG]$ss[KMG]
1769 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001770 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001771 Example: Exclude memory from 0x18690000-0x1869ffff
1772 memmap=64K$0x18690000
1773 or
1774 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001776 memory_corruption_check=0/1 [X86]
1777 Some BIOSes seem to corrupt the first 64k of
1778 memory when doing things like suspend/resume.
1779 Setting this option will scan the memory
1780 looking for corruption. Enabling this will
1781 both detect corruption and prevent the kernel
1782 from using the memory being corrupted.
1783 However, its intended as a diagnostic tool; if
1784 repeatable BIOS-originated corruption always
1785 affects the same memory, you can use memmap=
1786 to prevent the kernel from using that memory.
1787
1788 memory_corruption_check_size=size [X86]
1789 By default it checks for corruption in the low
1790 64k, making this memory unavailable for normal
1791 use. Use this parameter to scan for
1792 corruption in more or less memory.
1793
1794 memory_corruption_check_period=seconds [X86]
1795 By default it checks for corruption every 60
1796 seconds. Use this parameter to check at some
1797 other rate. 0 disables periodic checking.
1798
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001799 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001800 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001801 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001802 Specifies the number of memtest passes to be
1803 performed. Each pass selects another test
1804 pattern from a given set of patterns. Memtest
1805 fills the memory with this pattern, validates
1806 memory contents and reserves bad memory
1807 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001808
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809 meye.*= [HW] Set MotionEye Camera parameters
1810 See Documentation/video4linux/meye.txt.
1811
Andres Salomon8f368812007-10-12 23:04:06 +02001812 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1813 Multi-Function General Purpose Timers on AMD Geode
1814 platforms.
1815
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001816 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1817 the BIOS has incorrectly applied a workaround. TinyBIOS
1818 version 0.98 is known to be affected, 0.99 fixes the
1819 problem by letting the user disable the workaround.
1820
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 mga= [HW,DRM]
1822
Randy Dunlap1c207f92008-11-19 15:36:16 -08001823 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1824 physical address is ignored.
1825
Michel Pollet39f45d72009-05-20 11:10:31 +01001826 mini2440= [ARM,HW,KNL]
1827 Format:[0..2][b][c][t]
1828 Default: "0tb"
1829 MINI2440 configuration specification:
1830 0 - The attached screen is the 3.5" TFT
1831 1 - The attached screen is the 7" TFT
1832 2 - The VGA Shield is attached (1024x768)
1833 Leaving out the screen size parameter will not load
1834 the TFT driver, and the framebuffer will be left
1835 unconfigured.
1836 b - Enable backlight. The TFT backlight pin will be
1837 linked to the kernel VESA blanking code and a GPIO
1838 LED. This parameter is not necessary when using the
1839 VGA shield.
1840 c - Enable the s3c camera interface.
1841 t - Reserved for enabling touchscreen support. The
1842 touchscreen support is not enabled in the mainstream
1843 kernel as of 2.6.30, a preliminary port can be found
1844 in the "bleeding edge" mini2440 support kernel at
1845 http://repo.or.cz/w/linux-2.6/mini2440.git
1846
Mel Gorman6b74ab92008-07-23 21:26:49 -07001847 mminit_loglevel=
1848 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1849 parameter allows control of the logging verbosity for
1850 the additional memory initialisation checks. A value
1851 of 0 disables mminit logging and a level of 4 will
1852 log everything. Information is printed at KERN_DEBUG
1853 so loglevel=8 may also need to be specified.
1854
Rusty Russell106a4ee2012-09-26 10:09:40 +01001855 module.sig_enforce
1856 [KNL] When CONFIG_MODULE_SIG is set, this means that
1857 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001858 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001859 is always true, so this option does nothing.
1860
Linus Torvalds1da177e2005-04-16 15:20:36 -07001861 mousedev.tap_time=
1862 [MOUSE] Maximum time between finger touching and
1863 leaving touchpad surface for touch to be considered
1864 a tap and be reported as a left button click (for
1865 touchpads working in absolute mode only).
1866 Format: <msecs>
1867 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1868 reporting absolute coordinates, such as tablets
1869 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1870 reporting absolute coordinates, such as tablets
1871
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301872 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001873 is similar to kernelcore except it specifies the
1874 amount of memory used for migratable allocations.
1875 If both kernelcore and movablecore is specified,
1876 then kernelcore will be at *least* the specified
1877 value but may be more. If movablecore on its own
1878 is specified, the administrator must be careful
1879 that the amount of memory usable for all allocations
1880 is not too small.
1881
Tang Chenc5320922013-11-12 15:08:10 -08001882 movable_node [KNL,X86] Boot-time switch to enable the effects
1883 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1884
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885 MTD_Partition= [MTD]
1886 Format: <name>,<region-number>,<size>,<offset>
1887
Randy Dunlapa9913042005-10-23 12:57:11 -07001888 MTD_Region= [MTD] Format:
1889 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890
1891 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001892 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001894 multitce=off [PPC] This parameter disables the use of the pSeries
1895 firmware feature for updating multiple TCE entries
1896 at a time.
1897
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001898 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1899
1900 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1901
1902 boundary - index of last SLC block on Flex-OneNAND.
1903 The remaining blocks are configured as MLC blocks.
1904 lock - Configure if Flex-OneNAND boundary should be locked.
1905 Once locked, the boundary cannot be changed.
1906 1 indicates lock status, 0 indicates unlock status.
1907
Ben Dooks9db829f2008-07-03 11:24:29 +01001908 mtdset= [ARM]
1909 ARM/S3C2412 JIVE boot control
1910
1911 See arch/arm/mach-s3c2412/mach-jive.c
1912
Linus Torvalds1da177e2005-04-16 15:20:36 -07001913 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001914 [HW] Make the MicroTouch USB driver use raw coordinates
1915 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001916
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001917 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001918 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001919 that could hold holes aka. UC entries.
1920
1921 mtrr_gran_size=nn[KMG] [X86]
1922 Used for mtrr cleanup. It is granularity of mtrr block.
1923 Default is 1.
1924 Large value could prevent small alignment from
1925 using up MTRRs.
1926
1927 mtrr_spare_reg_nr=n [X86]
1928 Format: <integer>
1929 Range: 0,7 : spare reg number
1930 Default : 1
1931 Used for mtrr cleanup. It is spare mtrr entries number.
1932 Set to 2 or more if your graphical card needs more.
1933
Linus Torvalds1da177e2005-04-16 15:20:36 -07001934 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1935
Linus Torvalds1da177e2005-04-16 15:20:36 -07001936 netdev= [NET] Network devices parameters
1937 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1938 Note that mem_start is often overloaded to mean
1939 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001940 This usage is only documented in each driver source
1941 file if at all.
1942
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001943 nf_conntrack.acct=
1944 [NETFILTER] Enable connection tracking flow accounting
1945 0 to disable accounting
1946 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001947 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001948
Chuck Lever306a0752010-09-17 10:54:37 -04001949 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001950 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951
1952 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001953 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954
Chuck Lever306a0752010-09-17 10:54:37 -04001955 nfsrootdebug [NFS] enable nfsroot debugging messages.
1956 See Documentation/filesystems/nfs/nfsroot.txt.
1957
Trond Myklebusta72b4422006-01-03 09:55:41 +01001958 nfs.callback_tcpport=
1959 [NFS] set the TCP port on which the NFSv4 callback
1960 channel should listen.
1961
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001962 nfs.cache_getent=
1963 [NFS] sets the pathname to the program which is used
1964 to update the NFS client cache entries.
1965
1966 nfs.cache_getent_timeout=
1967 [NFS] sets the timeout after which an attempt to
1968 update a cache entry is deemed to have failed.
1969
Trond Myklebust58df0952006-01-03 09:55:57 +01001970 nfs.idmap_cache_timeout=
1971 [NFS] set the maximum lifetime for idmapper cache
1972 entries.
1973
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001974 nfs.enable_ino64=
1975 [NFS] enable 64-bit inode numbers.
1976 If zero, the NFS client will fake up a 32-bit inode
1977 number for the readdir() and stat() syscalls instead
1978 of returning the full 64-bit number.
1979 The default is to return 64-bit inode numbers.
1980
Trond Myklebustef159e92012-02-06 19:50:40 -05001981 nfs.max_session_slots=
1982 [NFSv4.1] Sets the maximum number of session slots
1983 the client will attempt to negotiate with the server.
1984 This limits the number of simultaneous RPC requests
1985 that the client can send to the NFSv4.1 server.
1986 Note that there is little point in setting this
1987 value higher than the max_tcp_slot_table_limit.
1988
Trond Myklebustb064eca22011-02-22 15:44:32 -08001989 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001990 [NFSv4] When set to the default of '1', this option
1991 ensures that both the RPC level authentication
1992 scheme and the NFS level operations agree to use
1993 numeric uids/gids if the mount is using the
1994 'sec=sys' security flavour. In effect it is
1995 disabling idmapping, which can make migration from
1996 legacy NFSv2/v3 systems to NFSv4 easier.
1997 Servers that do not support this mode of operation
1998 will be autodetected by the client, and it will fall
1999 back to using the idmapper.
2000 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002001 nfs.nfs4_unique_id=
2002 [NFS4] Specify an additional fixed unique ident-
2003 ification string that NFSv4 clients can insert into
2004 their nfs_client_id4 string. This is typically a
2005 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002006
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002007 nfs.send_implementation_id =
2008 [NFSv4.1] Send client implementation identification
2009 information in exchange_id requests.
2010 If zero, no implementation identification information
2011 will be sent.
2012 The default is to send the implementation identification
2013 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002014
2015 nfs.recover_lost_locks =
2016 [NFSv4] Attempt to recover locks that were lost due
2017 to a lease timeout on the server. Please note that
2018 doing this risks data corruption, since there are
2019 no guarantees that the file will remain unchanged
2020 after the locks are lost.
2021 If you want to enable the kernel legacy behaviour of
2022 attempting to recover these locks, then set this
2023 parameter to '1'.
2024 The default parameter value of '0' causes the kernel
2025 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002026
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002027 nfsd.nfs4_disable_idmapping=
2028 [NFSv4] When set to the default of '1', the NFSv4
2029 server will return only numeric uids and gids to
2030 clients using auth_sys, and will accept numeric uids
2031 and gids from such clients. This is intended to ease
2032 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002033
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002034 objlayoutdriver.osd_login_prog=
2035 [NFS] [OBJLAYOUT] sets the pathname to the program which
2036 is used to automatically discover and login into new
2037 osd-targets. Please see:
2038 Documentation/filesystems/pnfs.txt for more explanations
2039
Paul Mundt1e1030d2009-09-01 17:38:32 +09002040 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002041 when a NMI is triggered.
2042 Format: [state][,regs][,debounce][,die]
2043
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302044 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002045 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05002046 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002047 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002048 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002049 timeout occurs (or 'nopanic' to override the opposite
2050 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002051 This is useful when you use a panic=... timeout and
2052 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053
Anton Vorontsovbff38772009-07-08 11:10:56 -07002054 netpoll.carrier_timeout=
2055 [NET] Specifies amount of time (in seconds) that
2056 netpoll should wait for a carrier. By default netpoll
2057 waits 4 seconds.
2058
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002059 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060 emulation library even if a 387 maths coprocessor
2061 is present.
2062
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002063 no_console_suspend
2064 [HW] Never suspend the console
2065 Disable suspending of consoles during suspend and
2066 hibernate operations. Once disabled, debugging
2067 messages can reach various consoles while the rest
2068 of the system is being put to sleep (ie, while
2069 debugging driver suspend/resume hooks). This may
2070 not work reliably with all consoles, but is known
2071 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002072 To facilitate more flexible debugging, we also add
2073 console_suspend, a printk module parameter to control
2074 it. Users could use console_suspend (usually
2075 /sys/module/printk/parameters/console_suspend) to
2076 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002077
Christoph Lameterc1aee212007-05-31 00:40:47 -07002078 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2079 caches in the slab allocator. Saves per-node memory,
2080 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002081
Randy Dunlapa9913042005-10-23 12:57:11 -07002082 noalign [KNL,ARM]
2083
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 noapic [SMP,APIC] Tells the kernel to not make use of any
2085 IOAPICs that may be present in the system.
2086
Kees Cook8ab38202013-10-10 17:18:14 -07002087 nokaslr [X86]
Kees Cooke2b32e62014-02-25 16:59:17 -08002088 Disable kernel and module base offset ASLR (Address
2089 Space Layout Randomization) if built into the kernel.
Kees Cook8ab38202013-10-10 17:18:14 -07002090
Mike Galbraith5091faa2010-11-30 14:18:03 +01002091 noautogroup Disable scheduler automatic task group creation.
2092
Linus Torvalds1da177e2005-04-16 15:20:36 -07002093 nobats [PPC] Do not use BATs for mapping kernel lowmem
2094 on "Classic" PPC cores.
2095
2096 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002097
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002098 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2099
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002100 nodelayacct [KNL] Disable per-task delay accounting
2101
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2103
Paul Mundt6902aa82008-09-21 17:14:42 +09002104 nodsp [SH] Disable hardware DSP at boot time.
2105
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302106 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002107
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108 noexec [IA-64]
2109
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302110 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002111 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002113 noexec=off: disable non-executable mappings
2114
H. Peter Anvin52b61792012-09-21 12:43:13 -07002115 nosmap [X86]
2116 Disable SMAP (Supervisor Mode Access Prevention)
2117 even if it is supported by processor.
2118
Fenghua Yude5397a2011-05-11 16:51:05 -07002119 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002120 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002121 even if it is supported by processor.
2122
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002123 noexec32 [X86-64]
2124 This affects only 32-bit executables.
2125 noexec32=on: enable non-executable mappings (default)
2126 read doesn't imply executable mappings
2127 noexec32=off: disable non-executable mappings
2128 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129
Paul Mundt6902aa82008-09-21 17:14:42 +09002130 nofpu [SH] Disable hardware FPU at boot time.
2131
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002132 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002133 register save and restore. The kernel will only save
2134 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002135
Suresh Siddha0c752a92009-05-22 12:17:45 -07002136 noxsave [BUGS=X86] Disables x86 extended register state save
2137 and restore using xsave. The kernel will fallback to
2138 enabling legacy floating-point and sse state.
2139
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002140 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002141 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002142 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002143 auto selects the default scheme, which automatically
2144 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002145
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002146 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2147 wfi(ARM) instruction doesn't work correctly and not to
2148 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002149
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002150 no_file_caps Tells the kernel not to honor file capabilities. The
2151 only way then for a file to be executed with privilege
2152 is to be setuid root or executed by root.
2153
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154 nohalt [IA-64] Tells the kernel not to use the power saving
2155 function PAL_HALT_LIGHT when idle. This increases
2156 power-consumption. On the positive side, it reduces
2157 interrupt wake-up latency, which may improve performance
2158 in certain environments such as networked servers or
2159 real-time systems.
2160
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002161 nohz= [KNL] Boottime enable/disable dynamic ticks
2162 Valid arguments: on, off
2163 Default: on
2164
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002165 nohz_full= [KNL,BOOT]
2166 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002167 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002168 whenever possible. The boot CPU will be forced outside
2169 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002170 The CPUs in this range must also be included in the
2171 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002172
Paul Mundteeee7852009-04-02 12:31:16 +09002173 noiotrap [SH] Disables trapped I/O port accesses.
2174
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002175 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002176 disable unhandled interrupt sources.
2177
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302178 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002179 broken timer IRQ sources.
2180
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181 noisapnp [ISAPNP] Disables ISA PnP code.
2182
2183 noinitrd [RAM] Tells the kernel not to load any configured
2184 initial RAM disk.
2185
Weidong Han03ea8152009-04-17 16:42:15 +08002186 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2187 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002188 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002189
Linus Torvalds1da177e2005-04-16 15:20:36 -07002190 nointroute [IA-64]
2191
Randy Dunlap16290242011-08-13 12:34:52 -07002192 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002193
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002194 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2195
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002196 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2197 fault handling.
2198
Glauber Costad910f5c2011-07-11 15:28:19 -04002199 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2200 steal time is computed, but won't influence scheduler
2201 behaviour
2202
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002203 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002204
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002205 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002206
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207 noltlbs [PPC] Do not use large page/tlb entries for kernel
2208 lowmem mapping on PPC40x.
2209
Horms312f1f02006-02-22 09:57:55 +09002210 nomca [IA-64] Disable machine check abort handling
2211
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002212 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002213
Andres Salomon83d73842007-10-12 23:04:06 +02002214 nomfgpt [X86-32] Disable Multi-Function General Purpose
2215 Timer usage (for AMD Geode machines).
2216
Don Zickusbda62632011-10-13 15:14:27 -04002217 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2218 shutdown the other cpus. Instead use the REBOOT_VECTOR
2219 irq.
2220
Dave Young02608be2012-02-01 10:33:14 +08002221 nomodule Disable module load
2222
Jiri Kosina016ddd92010-01-18 17:05:40 +01002223 nopat [X86] Disable PAT (page attribute table extension of
2224 pagetables) support.
2225
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002226 norandmaps Don't use address space randomization. Equivalent to
2227 echo 0 > /proc/sys/kernel/randomize_va_space
2228
Jiri Kosinabbff2162010-08-11 18:34:09 +02002229 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002230
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002231 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002232 with UP alternatives
2233
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002234 nordrand [X86] Disable the direct use of the RDRAND
2235 instruction even if it is supported by the
2236 processor. RDRAND is still available to user
2237 space applications.
2238
Randy Dunlapa9913042005-10-23 12:57:11 -07002239 noresume [SWSUSP] Disables resume and restores original swap
2240 space.
2241
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242 no-scroll [VGA] Disables scrollback.
2243 This is required for the Braillex ib80-piezo Braille
2244 reader made by F.H. Papenmeier (Germany).
2245
2246 nosbagart [IA-64]
2247
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002248 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002249
Len Brown61ec7562007-08-16 03:34:22 -04002250 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2251 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252
Dave Jones97842212007-07-15 23:41:05 -07002253 nosoftlockup [KNL] Disable the soft-lockup detector.
2254
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 nosync [HW,M68K] Disables sync negotiation for all devices.
2256
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002257 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258
2259 nousb [USB] Disable the USB subsystem
2260
Ben Hutchings55142372011-01-02 23:02:42 +00002261 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002262
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002264
Weidong Han2b2fd872009-04-17 16:42:12 +08002265 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2266
Fenghua Yuf78cff42012-11-13 11:32:38 -08002267 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2268 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2269 Some features depend on CPU0. Known dependencies are:
2270 1. Resume from suspend/hibernate depends on CPU0.
2271 Suspend/hibernate will fail if CPU0 is offline and you
2272 need to online CPU0 before suspend/hibernate.
2273 2. PIC interrupts also depend on CPU0. CPU0 can't be
2274 removed if a PIC interrupt is detected.
2275 It's said poweroff/reboot may depend on CPU0 on some
2276 machines although I haven't seen such issues so far
2277 after CPU0 is offline on a few tested machines.
2278 If the dependencies are under your control, you can
2279 turn on cpu0_hotplug.
2280
Randy Dunlap16290242011-08-13 12:34:52 -07002281 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002282 purges which is reported from either PAL_VM_SUMMARY or
2283 SAL PALO.
2284
Yinghai Lu2b633e32010-02-10 01:20:37 -08002285 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2286 could support. nr_cpus=n : n >= 1 limits the kernel to
2287 supporting 'n' processors. Later in runtime you can not
2288 use hotplug cpu feature to put more cpu back to online.
2289 just like you compile the kernel NR_CPUS=n
2290
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002291 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2292
Mel Gorman1a687c22012-11-22 11:16:36 +00002293 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2294 Allowed values are enable and disable
2295
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002296 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2297 one of ['zone', 'node', 'default'] can be specified
2298 This can be set from sysctl after boot.
2299 See Documentation/sysctl/vm.txt for details.
2300
Randy Dunlap7c4be252009-01-06 14:42:44 -08002301 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2302 See Documentation/debugging-via-ohci1394.txt for more
2303 info.
2304
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002305 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2306 Rather than timing out after 20 ms if an EC
2307 command is not properly ACKed, override the length
2308 of the timeout. We have interrupts disabled while
2309 waiting for the ACK, so if this is set too high
2310 interrupts *may* be lost!
2311
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002312 omap_mux= [OMAP] Override bootloader pin multiplexing.
2313 Format: <mux_mode0.mode_name=value>...
2314 For example, to override I2C bus2:
2315 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2316
Linus Torvalds1da177e2005-04-16 15:20:36 -07002317 oprofile.timer= [HW]
2318 Use timer interrupt instead of performance counters
2319
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002320 oprofile.cpu_type= Force an oprofile cpu type
2321 This might be useful if you have an older oprofile
2322 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002323 Format: { arch_perfmon }
2324 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002325 perfmon on Intel CPUs instead of the
2326 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002327 timer: [X86] Force use of architectural NMI
2328 timer mode (see also oprofile.timer
2329 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002330 [s390] Force legacy basic mode sampling
2331 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002332
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002333 oops=panic Always panic on oopses. Default is to just kill the
2334 process, but there is a small probability of
2335 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002336 This will also cause panics on machine check exceptions.
2337 Useful together with panic=30 to trigger a reboot.
2338
Randy Dunlapbcfde332010-06-07 17:10:38 -07002339 OSS [HW,OSS]
2340 See Documentation/sound/oss/oss-parameters.txt
2341
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002342 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002343 timeout > 0: seconds before rebooting
2344 timeout = 0: wait forever
2345 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002346 Format: <timeout>
2347
2348 parkbd.port= [HW] Parallel port number the keyboard adapter is
2349 connected to, default is 0.
2350 Format: <parport#>
2351 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2352 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002353 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354
Randy Dunlapa9913042005-10-23 12:57:11 -07002355 parport= [HW,PPT] Specify parallel ports. 0 disables.
2356 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2357 Use 'auto' to force the driver to use any
2358 IRQ/DMA settings detected (the default is to
2359 ignore detected IRQ/DMA settings because of
2360 possible conflicts). You can specify the base
2361 address, IRQ, and DMA settings; IRQ and DMA
2362 should be numbers, or 'auto' (for using detected
2363 settings on that particular port), or 'nofifo'
2364 (to avoid using a FIFO even if it is detected).
2365 Parallel ports are assigned in the order they
2366 are specified on the command line, starting
2367 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002368
Randy Dunlapa9913042005-10-23 12:57:11 -07002369 parport_init_mode= [HW,PPT]
2370 Configure VIA parallel port to operate in
2371 a specific mode. This is necessary on Pegasos
2372 computer where firmware has no options for setting
2373 up parallel port mode and sets it to spp.
2374 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375 Format: [spp|ps2|epp|ecp|ecpepp]
2376
Andrew Mortondd287792006-03-23 03:00:57 -08002377 pause_on_oops=
2378 Halt all CPUs after the first oops has been printed for
2379 the specified number of seconds. This is to be used if
2380 your oopses keep scrolling off the screen.
2381
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 pcbit= [HW,ISDN]
2383
2384 pcd. [PARIDE]
2385 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002386 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002387
Randy Dunlapa9913042005-10-23 12:57:11 -07002388 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002389 earlydump [X86] dump PCI config space before the kernel
2390 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002391 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002392 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002393 the hardware directly. Use this if your machine
2394 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002395 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002396 hardware access methods are allowed. Use this
2397 if you experience crashes upon bootup and you
2398 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002399 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002400 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002401 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002402 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002403 noaer [PCIE] If the PCIEAER kernel config parameter is
2404 enabled, this kernel boot option can be used to
2405 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002406 nodomains [PCI] Disable support for multiple PCI
2407 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302408 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002409 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002410 check_enable_amd_mmconf [X86] check for and enable
2411 properly configured MMIO access to PCI
2412 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002413 nomsi [MSI] If the PCI_MSI kernel config parameter is
2414 enabled, this kernel boot option can be used to
2415 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002416 noioapicquirk [APIC] Disable all boot interrupt quirks.
2417 Safety option to keep boot IRQs enabled. This
2418 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002419 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2420 primary IO-APIC for bridges that cannot disable
2421 boot IRQs. This fixes a source of spurious IRQs
2422 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002423 noioapicreroute [APIC] Disable workaround that uses the
2424 boot IRQ equivalent of an IRQ that connects to
2425 a chipset where boot IRQs cannot be disabled.
2426 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002427 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002428 routing table. These calls are known to be buggy
2429 on several machines and they hang the machine
2430 when used, but on other computers it's the only
2431 way to get the interrupt routing table. Try
2432 this option if the kernel is unable to allocate
2433 IRQs or discover secondary PCI buses on your
2434 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002435 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002436 Use with caution as certain devices share
2437 address decoders between ROMs and other
2438 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002439 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002440 expansion ROMs that do not already have
2441 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002442 nobar [X86] Do not assign address space to the
2443 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002444 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002445 assigned automatically to PCI devices. You can
2446 make the kernel exclude IRQs of your ISA cards
2447 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002448 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002449 of the PIRQ table (normally generated
2450 by the BIOS) if it is outside the
2451 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002452 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002453 useful if the kernel is unable to find your
2454 secondary buses and you want to tell it
2455 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002456 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002457 numbers ourselves, overriding
2458 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002459 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002460 in the BIOS $PIR table. This is needed on
2461 some systems with broken BIOSes, notably
2462 some HP Pavilion N5400 and Omnibook XE3
2463 notebooks. This will have no effect if ACPI
2464 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002465 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002466 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002467 use_crs [X86] Use PCI host bridge window information
2468 from ACPI. On BIOSes from 2008 or later, this
2469 is enabled by default. If you need to use this,
2470 please report a bug.
2471 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2472 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002473 routeirq Do IRQ routing for all PCI devices.
2474 This is normally done in pci_enable_device(),
2475 so this option is a temporary workaround
2476 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002477 skip_isa_align [X86] do not align io start addr, so can
2478 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002479 firmware [ARM] Do not re-enumerate the bus but instead
2480 just use the configuration from the
2481 bootloader. This is currently used on
2482 IXP2000 systems where the bus has to be
2483 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002484 noearly [X86] Don't do any early type 1 scanning.
2485 This might help on some broken boards which
2486 machine check when some devices' config space
2487 is read. But various workarounds are disabled
2488 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002489 bfsort Sort PCI devices into breadth-first order.
2490 This sorting is done to get a device
2491 order compatible with older (<= 2.4) kernels.
2492 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002493 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2494 tuning and use the BIOS-configured MPS defaults.
2495 pcie_bus_safe Set every device's MPS to the largest value
2496 supported by all devices below the root complex.
2497 pcie_bus_perf Set device MPS to the largest allowable MPS
2498 based on its parent bus. Also set MRRS (Max
2499 Read Request Size) to the largest supported
2500 value (no larger than the MPS that the device
2501 or bus can support) for best performance.
2502 pcie_bus_peer2peer Set every device's MPS to 128B, which
2503 every device is guaranteed to support. This
2504 configuration allows peer-to-peer DMA between
2505 any pair of devices, possibly at the cost of
2506 reduced performance. This also guarantees
2507 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002508 cbiosize=nn[KMG] The fixed amount of bus space which is
2509 reserved for the CardBus bridge's IO window.
2510 The default value is 256 bytes.
2511 cbmemsize=nn[KMG] The fixed amount of bus space which is
2512 reserved for the CardBus bridge's memory
2513 window. The default value is 64 megabytes.
Yuji Shimada32a9a682009-03-16 17:13:39 +09002514 resource_alignment=
2515 Format:
2516 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2517 Specifies alignment and device to reassign
2518 aligned memory resources.
2519 If <order of align> is not specified,
2520 PAGE_SIZE is used as alignment.
2521 PCI-PCI bridge can be specified, if resource
2522 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002523 ecrc= Enable/disable PCIe ECRC (transaction layer
2524 end-to-end CRC checking).
2525 bios: Use BIOS/firmware settings. This is the
2526 the default.
2527 off: Turn ECRC off
2528 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002529 hpiosize=nn[KMG] The fixed amount of bus space which is
2530 reserved for hotplug bridge's IO window.
2531 Default size is 256 bytes.
2532 hpmemsize=nn[KMG] The fixed amount of bus space which is
2533 reserved for hotplug bridge's memory window.
2534 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002535 realloc= Enable/disable reallocating PCI bridge resources
2536 if allocations done by BIOS are too small to
2537 accommodate resources required by all child
2538 devices.
2539 off: Turn realloc off
2540 on: Turn realloc on
2541 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002542 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002543 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2544 only look for one device below a PCIe downstream
2545 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002546
Chuck Ebberte5665a42008-09-24 20:40:34 -04002547 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2548 Management.
2549 off Disable ASPM.
2550 force Enable ASPM even on devices that claim not to support it.
2551 WARNING: Forcing ASPM on may cause system lockups.
2552
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002553 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2554 nomsi Do not use MSI for PCI Express Native Hotplug (this
2555 makes all PCIe ports use INTx for hotplug services).
2556
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002557 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002558 auto Ask the BIOS whether or not to use native PCIe services
2559 associated with PCIe ports (PME, hot-plug, AER). Use
2560 them only if that is allowed by the BIOS.
2561 native Use native PCIe services associated with PCIe ports
2562 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002563 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2564 ports driver.
2565
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002566 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002567 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002568 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002569
Linus Torvalds1da177e2005-04-16 15:20:36 -07002570 pcmv= [HW,PCMCIA] BadgePAD 4
2571
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302572 pd_ignore_unused
2573 [PM]
2574 Keep all power-domains already enabled by bootloader on,
2575 even if no driver has claimed them. This is useful
2576 for debug and development, but should not be
2577 needed on a platform with proper driver support.
2578
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002580 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002581
2582 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2583 boot time.
2584 Format: { 0 | 1 }
2585 See arch/parisc/kernel/pdc_chassis.c
2586
Tejun Heof58dc012009-08-14 15:00:50 +09002587 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002588 Currently supported values are "embed" and "page".
2589 Archs may support subset or none of the selections.
2590 See comments in mm/percpu.c for details on each
2591 allocator. This parameter is primarily for debugging
2592 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002593
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002595 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596
2597 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002598 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599
2600 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002601 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002602
2603 plip= [PPT,NET] Parallel port network link
2604 Format: { parport<nr> | timid | 0 }
2605 See also Documentation/parport.txt.
2606
Randy Dunlap16290242011-08-13 12:34:52 -07002607 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002608 Override pmtimer IOPort with a hex value.
2609 e.g. pmtmr=0x508
2610
Bjorn Helgaas96242112011-08-11 12:14:05 -06002611 pnp.debug=1 [PNP]
2612 Enable PNP debug messages (depends on the
2613 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2614 via /sys/module/pnp/parameters/debug. We always show
2615 current resource usage; turning this on also shows
2616 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002617
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618 pnpacpi= [ACPI]
2619 { off }
2620
2621 pnpbios= [ISAPNP]
2622 { on | off | curr | res | no-curr | no-res }
2623
2624 pnp_reserve_irq=
2625 [ISAPNP] Exclude IRQs for the autoconfiguration
2626
2627 pnp_reserve_dma=
2628 [ISAPNP] Exclude DMAs for the autoconfiguration
2629
2630 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002631 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002632
2633 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002634 [ISAPNP] Exclude memory regions for the
2635 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636 Ranges are in pairs (memory base and size).
2637
Randy Dunlap4af94f32009-04-17 18:30:28 -07002638 ports= [IP_VS_FTP] IPVS ftp helper module
2639 Default is 21.
2640 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2641 may be specified.
2642 Format: <port>,<port>....
2643
Ingo Molnar45807a12007-07-15 23:40:10 -07002644 print-fatal-signals=
2645 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002646
2647 If enabled, warn about various signal handling
2648 related application anomalies: too many signals,
2649 too many POSIX.1 timers, fatal signals causing a
2650 coredump - etc.
2651
2652 If you hit the warning due to signal overflow,
2653 you might want to try "ulimit -i unlimited".
2654
Ingo Molnar45807a12007-07-15 23:40:10 -07002655 default: off.
2656
Matthew Garrettc22ab332012-03-05 14:59:10 -08002657 printk.always_kmsg_dump=
2658 Trigger kmsg_dump for cases other than kernel oops or
2659 panics
2660 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2661 default: disabled
2662
Randy Dunlape84845c2007-07-15 23:40:25 -07002663 printk.time= Show timing data prefixed to each printk message line
2664 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2665
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002666 processor.max_cstate= [HW,ACPI]
2667 Limit processor to maximum C-state
2668 max_cstate=9 overrides any DMI blacklist limit.
2669
2670 processor.nocst [HW,ACPI]
2671 Ignore the _CST method to determine C-states,
2672 instead using the legacy FADT method
2673
Linus Torvalds1da177e2005-04-16 15:20:36 -07002674 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002675 Format: [schedule,]<number>
2676 Param: "schedule" - profile schedule points.
2677 Param: <number> - step/bucket size as a power of 2 for
2678 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002679 Param: "sleep" - profile D-state sleeping (millisecs).
2680 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002681 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682
Linus Torvalds1da177e2005-04-16 15:20:36 -07002683 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2684 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002685 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002686
Randy Dunlapa9913042005-10-23 12:57:11 -07002687 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2688 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002689 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2690 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002691 psmouse.resetafter= [HW,MOUSE]
2692 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002693 (0 = never).
2694 psmouse.resolution=
2695 [HW,MOUSE] Set desired mouse resolution, in dpi.
2696 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002697 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698 0 = disabled, 1 = enabled (default).
2699
Matthew Garrettdee28e72011-07-21 16:57:55 -04002700 pstore.backend= Specify the name of the pstore backend to use
2701
Linus Torvalds1da177e2005-04-16 15:20:36 -07002702 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002703 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002704
Kay Sieversdc8c8582007-08-15 12:25:38 +02002705 pty.legacy_count=
2706 [KNL] Number of legacy pty's. Overwrites compiled-in
2707 default number.
2708
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002709 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002710
Linus Torvalds1da177e2005-04-16 15:20:36 -07002711 r128= [HW,DRM]
2712
2713 raid= [HW,RAID]
2714 See Documentation/md.txt.
2715
Randy Dunlapa9913042005-10-23 12:57:11 -07002716 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002717 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002718
Linus Torvalds1da177e2005-04-16 15:20:36 -07002719 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002720 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002721
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002722 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002723 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2724 the specified list of CPUs to be no-callback CPUs.
2725 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002726 be offloaded to "rcuox/N" kthreads created for
2727 that purpose, where "x" is "b" for RCU-bh, "p"
2728 for RCU-preempt, and "s" for RCU-sched, and "N"
2729 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002730 offloaded CPUs, which can be useful for HPC and
2731 real-time workloads. It can also improve energy
2732 efficiency for asymmetric multiprocessors.
2733
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002734 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002735 Rather than requiring that offloaded CPUs
2736 (specified by rcu_nocbs= above) explicitly
2737 awaken the corresponding "rcuoN" kthreads,
2738 make these kthreads poll for callbacks.
2739 This improves the real-time response for the
2740 offloaded CPUs by relieving them of the need to
2741 wake up the corresponding kthread, but degrades
2742 energy efficiency by requiring that the kthreads
2743 periodically wake up to do the polling.
2744
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002745 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002746 Set maximum number of finished RCU callbacks to
2747 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002748
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002749 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002750 Increase the number of CPUs assigned to each
2751 leaf rcu_node structure. Useful for very large
2752 systems.
2753
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002754 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002755 Set delay from grace-period initialization to
2756 first attempt to force quiescent states.
2757 Units are jiffies, minimum value is zero,
2758 and maximum value is HZ.
2759
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002760 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002761 Set delay between subsequent attempts to force
2762 quiescent states. Units are jiffies, minimum
2763 value is one, and maximum value is HZ.
2764
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002765 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002766 Set threshold of queued RCU callbacks beyond which
2767 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002768
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002769 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002770 Set threshold of queued RCU callbacks below which
2771 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002772
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002773 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002774 Set wakeup interval for idle CPUs that have
2775 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002776
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002777 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002778 Set wakeup interval for idle CPUs that have
2779 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2780 Lazy RCU callbacks are those which RCU can
2781 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002782
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002783 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002784 Set duration of force_quiescent_state bursts.
2785
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002786 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002787 Set holdoff time within force_quiescent_state bursts.
2788
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002789 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002790 Set wait time between force_quiescent_state bursts.
2791
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002792 rcutorture.gp_exp= [KNL]
2793 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002794
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002795 rcutorture.gp_normal= [KNL]
2796 Use normal (non-expedited) update-side primitives.
2797 If both gp_exp and gp_normal are set, do both.
2798 If neither gp_exp nor gp_normal are set, still
2799 do both.
2800
2801 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002802 Set callbacks/threads for rcu_barrier() testing.
2803
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002804 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002805 Set number of concurrent RCU writers. These just
2806 stress RCU, they don't participate in the actual
2807 test, hence the "fake".
2808
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002809 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002810 Set number of RCU readers.
2811
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002812 rcutorture.object_debug= [KNL]
2813 Enable debug-object double-call_rcu() testing.
2814
2815 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002816 Set time (s) after boot for CPU-hotplug testing.
2817
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002818 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002819 Set time (s) between CPU-hotplug operations, or
2820 zero to disable CPU-hotplug testing.
2821
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002822 rcutorture.rcutorture_runnable= [BOOT]
2823 Start rcutorture running at boot time.
2824
2825 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002826 Set task-shuffle interval (s). Shuffling tasks
2827 allows some CPUs to go into dyntick-idle mode
2828 during the rcutorture test.
2829
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002830 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002831 Set time (s) after boot system shutdown. This
2832 is useful for hands-off automated testing.
2833
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002834 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002835 Duration of CPU stall (s) to test RCU CPU stall
2836 warnings, zero to disable.
2837
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002838 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002839 Time to wait (s) after boot before inducing stall.
2840
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002841 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002842 Time (s) between statistics printk()s.
2843
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002844 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002845 Time (s) to stutter testing, for example, specifying
2846 five seconds causes the test to run for five seconds,
2847 wait for five seconds, and so on. This tests RCU's
2848 ability to transition abruptly to and from idle.
2849
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002850 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002851 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2852 "Maybe" means test if the RCU implementation
2853 under test support RCU priority boosting.
2854
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002855 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002856 Duration (s) of each individual boost test.
2857
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002858 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002859 Interval (s) between each boost test.
2860
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002861 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002862 Test RCU's dyntick-idle handling. See also the
2863 rcutorture.shuffle_interval parameter.
2864
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002865 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002866 Specify the RCU implementation to test.
2867
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002868 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002869 Enable additional printk() statements.
2870
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002871 rcupdate.rcu_expedited= [KNL]
2872 Use expedited grace-period primitives, for
2873 example, synchronize_rcu_expedited() instead
2874 of synchronize_rcu(). This reduces latency,
2875 but can increase CPU utilization, degrade
2876 real-time latency, and degrade energy efficiency.
2877
2878 rcupdate.rcu_cpu_stall_suppress= [KNL]
2879 Suppress RCU CPU stall warning messages.
2880
2881 rcupdate.rcu_cpu_stall_timeout= [KNL]
2882 Set timeout for RCU CPU stall warning messages.
2883
Olof Johanssonffdfc402005-09-06 15:17:19 -07002884 rdinit= [KNL]
2885 Format: <full_path>
2886 Run specified binary instead of /init from the ramdisk,
2887 used for early userspace startup. See initrd.
2888
Robin Holt1b3a5d02013-07-08 16:01:42 -07002889 reboot= [KNL]
2890 Format (x86 or x86_64):
2891 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2892 [[,]s[mp]#### \
2893 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2894 [[,]f[orce]
2895 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2896 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2897 reboot_force is either force or not specified,
2898 reboot_cpu is s[mp]#### with #### being the processor
2899 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900
Paul Jackson46b6d942008-07-04 10:00:09 -07002901 relax_domain_level=
2902 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002903 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002904
Linus Torvalds1da177e2005-04-16 15:20:36 -07002905 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2906
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002907 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002908 Format: nn[KMG]
2909 Reserves a hole at the top of the kernel virtual
2910 address space.
2911
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002912 reservelow= [X86]
2913 Format: nn[K]
2914 Set the amount of memory to reserve for BIOS at
2915 the bottom of the address space.
2916
Vivek Goyal7e962872006-09-27 01:50:44 -07002917 reset_devices [KNL] Force drivers to reset the underlying device
2918 during initialization.
2919
Randy Dunlapa9913042005-10-23 12:57:11 -07002920 resume= [SWSUSP]
2921 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002922 Format:
2923 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002924
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002925 resume_offset= [SWSUSP]
2926 Specify the offset from the beginning of the partition
2927 given by "resume=" at which the swap header is located,
2928 in <PAGE_SIZE> units (needed only for swap files).
2929 See Documentation/power/swsusp-and-swap-files.txt
2930
Barry Songf126f732011-10-10 23:38:41 +02002931 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2932 read the resume files
2933
Barry Song6f8d7022011-10-06 20:34:46 +02002934 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2935 Useful for devices that are detected asynchronously
2936 (e.g. USB and MMC devices).
2937
Bojan Smojverf996fc92010-09-09 23:06:23 +02002938 hibernate= [HIBERNATION]
2939 noresume Don't check if there's a hibernation image
2940 present during boot.
2941 nocompress Don't compress/decompress hibernation images.
2942
Michael Neuling0a7b35c2007-02-10 01:44:33 -08002943 retain_initrd [RAM] Keep initrd memory after extraction
2944
Linus Torvalds1da177e2005-04-16 15:20:36 -07002945 rhash_entries= [KNL,NET]
2946 Set number of hash buckets for route cache
2947
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948 ro [KNL] Mount root device read-only on boot
2949
2950 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002951 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002952
2953 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2954 mount the root filesystem
2955
2956 rootflags= [KNL] Set root filesystem mount option string
2957
2958 rootfstype= [KNL] Set root filesystem type
2959
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002960 rootwait [KNL] Wait (indefinitely) for root device to show up.
2961 Useful for devices that are detected asynchronously
2962 (e.g. USB and MMC devices).
2963
Robert Tivy5c71d612013-03-28 18:41:46 -07002964 rproc_mem=nn[KMG][@address]
2965 [KNL,ARM,CMA] Remoteproc physical memory block.
2966 Memory area to be used by remote processor image,
2967 managed by CMA.
2968
Linus Torvalds1da177e2005-04-16 15:20:36 -07002969 rw [KNL] Mount root device read-write on boot
2970
2971 S [KNL] Run init in single mode
2972
2973 sa1100ir [NET]
2974 See drivers/net/irda/sa1100_ir.c.
2975
Linus Torvalds1da177e2005-04-16 15:20:36 -07002976 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002977
Mike Travisf6630112009-11-17 18:22:15 -06002978 sched_debug [KNL] Enables verbose scheduler debug messages.
2979
Mike Galbraith5307c952012-05-08 12:20:58 +02002980 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2981 xtime_lock contention on larger systems, and/or RCU lock
2982 contention on all systems with CONFIG_MAXSMP set.
2983 Format: { "0" | "1" }
2984 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2985 1 -- enable.
2986 Note: increases power consumption, thus should only be
2987 enabled if running jitter sensitive (HPC/RT) workloads.
2988
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002989 security= [SECURITY] Choose a security module to enable at boot.
2990 If this boot parameter is not specified, only the first
2991 security module asking for security registration will be
2992 loaded. An invalid security module name will be treated
2993 as if no module has been chosen.
2994
2995 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002996 Format: { "0" | "1" }
2997 See security/selinux/Kconfig help text.
2998 0 -- disable.
2999 1 -- enable.
3000 Default value is set via kernel config option.
3001 If enabled at boot time, /selinux/disable can be used
3002 later to disable prior to initial policy load.
3003
John Johansenc1c124e2010-07-29 14:48:09 -07003004 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3005 Format: { "0" | "1" }
3006 See security/apparmor/Kconfig help text
3007 0 -- disable.
3008 1 -- enable.
3009 Default value is set via kernel config option.
3010
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003011 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003012
Linus Torvalds1da177e2005-04-16 15:20:36 -07003013 shapers= [NET]
3014 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003015
Yinghai Lub05f78f2008-08-22 01:32:50 -07003016 show_msr= [x86] show boot-time MSR settings
3017 Format: { <integer> }
3018 Show boot-time (BIOS-initialized) MSR settings.
3019 The parameter means the number of CPUs to show,
3020 for example 1 means boot CPU only.
3021
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 simeth= [IA-64]
3023 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003024
Linus Torvalds1da177e2005-04-16 15:20:36 -07003025 slram= [HW,MTD]
3026
David Rientjes3df1ccc2011-10-18 22:09:28 -07003027 slab_max_order= [MM, SLAB]
3028 Determines the maximum allowed order for slabs.
3029 A high setting may cause OOMs due to memory
3030 fragmentation. Defaults to 1 for systems with
3031 more than 32MB of RAM, 0 otherwise.
3032
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003033 slub_debug[=options[,slabs]] [MM, SLUB]
3034 Enabling slub_debug allows one to determine the
3035 culprit if slab objects become corrupted. Enabling
3036 slub_debug can create guard zones around objects and
3037 may poison objects when not in use. Also tracks the
3038 last alloc / free. For more information see
3039 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003040
3041 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003042 Determines the maximum allowed order for slabs.
3043 A high setting may cause OOMs due to memory
3044 fragmentation. For more information see
3045 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003046
3047 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003048 The minimum number of objects per slab. SLUB will
3049 increase the slab order up to slub_max_order to
3050 generate a sufficiently large slab able to contain
3051 the number of objects indicated. The higher the number
3052 of objects the smaller the overhead of tracking slabs
3053 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003054 For more information see Documentation/vm/slub.txt.
3055
3056 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003057 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003058 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003059 For more information see Documentation/vm/slub.txt.
3060
3061 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003062 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07003063 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003064 allocs to different slabs. Debug options disable
3065 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003066 For more information see Documentation/vm/slub.txt.
3067
Linus Torvalds1da177e2005-04-16 15:20:36 -07003068 smart2= [HW]
3069 Format: <io1>[,<io2>[,...,<io8>]]
3070
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003071 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3072 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3073 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3074 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3075 smsc-ircc2.ircc_irq= [HW] IRQ line
3076 smsc-ircc2.ircc_dma= [HW] DMA channel
3077 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3078 0: Toshiba Satellite 1800 (GP data pin select)
3079 1: Fast pin select (default)
3080 2: ATC IRMode
3081
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003082 softlockup_panic=
3083 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003084 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003085
Linus Torvalds1da177e2005-04-16 15:20:36 -07003086 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003087 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003088
Linus Torvalds1da177e2005-04-16 15:20:36 -07003089 spia_io_base= [HW,MTD]
3090 spia_fio_base=
3091 spia_pedr=
3092 spia_peddr=
3093
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003094 stacktrace [FTRACE]
3095 Enabled the stack tracer on boot up.
3096
Steven Rostedt762e1202011-12-19 22:01:00 -05003097 stacktrace_filter=[function-list]
3098 [FTRACE] Limit the functions that the stack tracer
3099 will trace at boot up. function-list is a comma separated
3100 list of functions. This list can be changed at run
3101 time by the stack_trace_filter file in the debugfs
3102 tracing directory. Note, this enables stack tracing
3103 and the stacktrace above is not needed.
3104
Linus Torvalds1da177e2005-04-16 15:20:36 -07003105 sti= [PARISC,HW]
3106 Format: <num>
3107 Set the STI (builtin display/keyboard on the HP-PARISC
3108 machines) console (graphic card) which should be used
3109 as the initial boot-console.
3110 See also comment in drivers/video/console/sticore.c.
3111
3112 sti_font= [HW]
3113 See comment in drivers/video/console/sticore.c.
3114
3115 stifb= [HW]
3116 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3117
Trond Myklebustcbf11072009-08-09 15:06:19 -04003118 sunrpc.min_resvport=
3119 sunrpc.max_resvport=
3120 [NFS,SUNRPC]
3121 SunRPC servers often require that client requests
3122 originate from a privileged port (i.e. a port in the
3123 range 0 < portnr < 1024).
3124 An administrator who wishes to reserve some of these
3125 ports for other uses may adjust the range that the
3126 kernel's sunrpc client considers to be privileged
3127 using these two parameters to set the minimum and
3128 maximum port values.
3129
Greg Banks42a7fc42007-03-06 01:42:23 -08003130 sunrpc.pool_mode=
3131 [NFS]
3132 Control how the NFS server code allocates CPUs to
3133 service thread pools. Depending on how many NICs
3134 you have and where their interrupts are bound, this
3135 option will affect which CPUs will do NFS serving.
3136 Note: this parameter cannot be changed while the
3137 NFS server is running.
3138
3139 auto the server chooses an appropriate mode
3140 automatically using heuristics
3141 global a single global pool contains all CPUs
3142 percpu one pool for each CPU
3143 pernode one pool for each NUMA node (equivalent
3144 to global on non-NUMA machines)
3145
Trond Myklebustcbf11072009-08-09 15:06:19 -04003146 sunrpc.tcp_slot_table_entries=
3147 sunrpc.udp_slot_table_entries=
3148 [NFS,SUNRPC]
3149 Sets the upper limit on the number of simultaneous
3150 RPC calls that can be sent from the client to a
3151 server. Increasing these values may allow you to
3152 improve throughput, but will also increase the
3153 amount of memory reserved for use by the client.
3154
Michal Hocko07555ac2013-08-22 16:35:46 -07003155 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003156 [KNL] Enable accounting of swap in memory resource
3157 controller if no parameter or 1 is given or disable
3158 it if 0 is given (See Documentation/cgroups/memory.txt)
3159
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003160 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3161 Format: { <int> | force }
3162 <int> -- Number of I/O TLB slabs
3163 force -- force using of bounce buffers even if they
3164 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003165
Linus Torvalds1da177e2005-04-16 15:20:36 -07003166 switches= [HW,M68k]
3167
Andi Kleene52eec12010-09-08 16:54:17 +02003168 sysfs.deprecated=0|1 [KNL]
3169 Enable/disable old style sysfs layout for old udev
3170 on older distributions. When this option is enabled
3171 very new udev will not work anymore. When this option
3172 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3173 in older udev will not work anymore.
3174 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3175 the kernel configuration.
3176
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003177 sysrq_always_enabled
3178 [KNL]
3179 Ignore sysrq setting - this boot parameter will
3180 neutralize any effect of /proc/sys/kernel/sysrq.
3181 Useful for debugging.
3182
Linus Torvalds1da177e2005-04-16 15:20:36 -07003183 tdfx= [HW,DRM]
3184
David Brownell77437fd2008-07-23 21:28:33 -07003185 test_suspend= [SUSPEND]
3186 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3187 standby suspend) as the system sleep state to briefly
3188 enter during system startup. The system is woken from
3189 this state using a wakeup-capable RTC alarm.
3190
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191 thash_entries= [KNL,NET]
3192 Set number of hash buckets for TCP connection
3193
Len Brownf8707ec2007-08-12 00:12:54 -04003194 thermal.act= [HW,ACPI]
3195 -1: disable all active trip points in all thermal zones
3196 <degrees C>: override all lowest active trip points
3197
Len Brownc52a7412007-08-14 15:49:32 -04003198 thermal.crt= [HW,ACPI]
3199 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003200 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003201
Len Brownf5487142007-08-12 00:12:44 -04003202 thermal.nocrt= [HW,ACPI]
3203 Set to disable actions on ACPI thermal zone
3204 critical and hot trip points.
3205
Len Brown72b33ef2007-08-12 00:12:17 -04003206 thermal.off= [HW,ACPI]
3207 1: disable ACPI thermal control
3208
Len Browna70cdc52007-08-12 00:12:35 -04003209 thermal.psv= [HW,ACPI]
3210 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003211 <degrees C>: override all passive trip points to this
3212 value
Len Browna70cdc52007-08-12 00:12:35 -04003213
Len Brown730ff342007-08-12 00:12:26 -04003214 thermal.tzp= [HW,ACPI]
3215 Specify global default ACPI thermal zone polling rate
3216 <deci-seconds>: poll all this frequency
3217 0: no polling (default)
3218
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003219 threadirqs [KNL]
3220 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003221 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003222
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003223 tmem [KNL,XEN]
3224 Enable the Transcendent memory driver if built-in.
3225
3226 tmem.cleancache=0|1 [KNL, XEN]
3227 Default is on (1). Disable the usage of the cleancache
3228 API to send anonymous pages to the hypervisor.
3229
3230 tmem.frontswap=0|1 [KNL, XEN]
3231 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003232 API to send swap pages to the hypervisor. If disabled
3233 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003234
3235 tmem.selfballooning=0|1 [KNL, XEN]
3236 Default is on (1). Disable the driving of swap pages
3237 to the hypervisor.
3238
3239 tmem.selfshrinking=0|1 [KNL, XEN]
3240 Default is on (1). Partial swapoff that immediately
3241 transfers pages from Xen hypervisor back to the
3242 kernel based on different criteria.
3243
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003244 topology= [S390]
3245 Format: {off | on}
3246 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003247 topology information if the hardware supports this.
3248 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003249 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003250 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003251
Linus Torvalds1da177e2005-04-16 15:20:36 -07003252 tp720= [HW,PS2]
3253
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003254 tpm_suspend_pcr=[HW,TPM]
3255 Format: integer pcr id
3256 Specify that at suspend time, the tpm driver
3257 should extend the specified pcr with zeros,
3258 as a workaround for some chips which fail to
3259 flush the last written pcr on TPM_SaveState.
3260 This will guarantee that all the other pcrs
3261 are saved.
3262
Li Zefan9d612be2009-06-24 17:33:15 +08003263 trace_buf_size=nn[KMG]
3264 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003265
Li Zefan020e5f82009-07-01 10:47:05 +08003266 trace_event=[event-list]
3267 [FTRACE] Set and start specified trace events in order
3268 to facilitate early boot debugging.
3269 See also Documentation/trace/events.txt
3270
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003271 trace_options=[option-list]
3272 [FTRACE] Enable or disable tracer options at boot.
3273 The option-list is a comma delimited list of options
3274 that can be enabled or disabled just as if you were
3275 to echo the option name into
3276
3277 /sys/kernel/debug/tracing/trace_options
3278
3279 For example, to enable stacktrace option (to dump the
3280 stack trace of each event), add to the command line:
3281
3282 trace_options=stacktrace
3283
3284 See also Documentation/trace/ftrace.txt "trace options"
3285 section.
3286
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003287 traceoff_on_warning
3288 [FTRACE] enable this option to disable tracing when a
3289 warning is hit. This turns off "tracing_on". Tracing can
3290 be enabled again by echoing '1' into the "tracing_on"
3291 file located in /sys/kernel/debug/tracing/
3292
3293 This option is useful, as it disables the trace before
3294 the WARNING dump is called, which prevents the trace to
3295 be filled with content caused by the warning output.
3296
3297 This option can also be set at run time via the sysctl
3298 option: kernel/traceoff_on_warning
3299
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003300 transparent_hugepage=
3301 [KNL]
3302 Format: [always|madvise|never]
3303 Can be used to control the default behavior of the system
3304 with respect to transparent hugepages.
3305 See Documentation/vm/transhuge.txt for more details.
3306
john stultzd3b8f882009-08-17 16:40:47 -07003307 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003308 Format: <string>
3309 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003310 disables clocksource verification at runtime, as well
3311 as the stability checks done at bootup. Used to enable
3312 high-resolution timer mode on older hardware, and in
3313 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003314 [x86] noirqtime: Do not use TSC to do irq accounting.
3315 Used to run time disable IRQ_TIME_ACCOUNTING on any
3316 platforms where RDTSC is slow and this accounting
3317 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003318
Randy Dunlapa9913042005-10-23 12:57:11 -07003319 turbografx.map[2|3]= [HW,JOY]
3320 TurboGraFX parallel port interface
3321 Format:
3322 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 See also Documentation/input/joystick-parport.txt
3324
Christian Kujaub6935f82011-05-31 15:22:05 +00003325 udbg-immortal [PPC] When debugging early kernel crashes that
3326 happen after console_init() and before a proper
3327 console driver takes over, this boot options might
3328 help "seeing" what's going on.
3329
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003330 uhash_entries= [KNL,NET]
3331 Set number of hash buckets for UDP/UDP-Lite connections
3332
Alan Stern5f8364b2006-12-05 16:29:55 -05003333 uhci-hcd.ignore_oc=
3334 [USB] Ignore overcurrent events (default N).
3335 Some badly-designed motherboards generate lots of
3336 bogus events, for ports that aren't wired to
3337 anything. Set this parameter to avoid log spamming.
3338 Note that genuine overcurrent events won't be
3339 reported either.
3340
Simon Arlotte3a61b02008-07-19 23:32:54 +01003341 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003342 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003343
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003344 usbcore.authorized_default=
3345 [USB] Default USB device authorization:
3346 (default -1 = authorized except for wireless USB,
3347 0 = not authorized, 1 = authorized)
3348
Alan Sternb5e795f2007-02-20 15:00:53 -05003349 usbcore.autosuspend=
3350 [USB] The autosuspend time delay (in seconds) used
3351 for newly-detected USB devices (default 2). This
3352 is the time required before an idle device will be
3353 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003354 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003355
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003356 usbcore.usbfs_snoop=
3357 [USB] Set to log all usbfs traffic (default 0 = off).
3358
3359 usbcore.blinkenlights=
3360 [USB] Set to cycle leds on hubs (default 0 = off).
3361
3362 usbcore.old_scheme_first=
3363 [USB] Start with the old device initialization
3364 scheme (default 0 = off).
3365
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003366 usbcore.usbfs_memory_mb=
3367 [USB] Memory limit (in MB) for buffers allocated by
3368 usbfs (default = 16, 0 = max = 2047).
3369
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003370 usbcore.use_both_schemes=
3371 [USB] Try the other device initialization scheme
3372 if the first one fails (default 1 = enabled).
3373
3374 usbcore.initial_descriptor_timeout=
3375 [USB] Specifies timeout for the initial 64-byte
3376 USB_REQ_GET_DESCRIPTOR request in milliseconds
3377 (default 5000 = 5.0 seconds).
3378
Linus Torvalds1da177e2005-04-16 15:20:36 -07003379 usbhid.mousepoll=
3380 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003381
Alan Sternd4f373e2008-11-10 14:07:45 -05003382 usb-storage.delay_use=
3383 [UMS] The delay in seconds before a new device is
3384 scanned for Logical Units (default 5).
3385
3386 usb-storage.quirks=
3387 [UMS] A list of quirks entries to supplement or
3388 override the built-in unusual_devs list. List
3389 entries are separated by commas. Each entry has
3390 the form VID:PID:Flags where VID and PID are Vendor
3391 and Product ID values (4-digit hex numbers) and
3392 Flags is a set of characters, each corresponding
3393 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003394 a = SANE_SENSE (collect more than 18 bytes
3395 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003396 b = BAD_SENSE (don't collect more than 18
3397 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003398 c = FIX_CAPACITY (decrease the reported
3399 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003400 d = NO_READ_DISC_INFO (don't use
3401 READ_DISC_INFO command);
3402 e = NO_READ_CAPACITY_16 (don't use
3403 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003404 h = CAPACITY_HEURISTICS (decrease the
3405 reported device capacity by one
3406 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003407 i = IGNORE_DEVICE (don't bind to this
3408 device);
3409 l = NOT_LOCKABLE (don't try to lock and
3410 unlock ejectable media);
3411 m = MAX_SECTORS_64 (don't transfer more
3412 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003413 n = INITIAL_READ10 (force a retry of the
3414 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003415 o = CAPACITY_OK (accept the capacity
3416 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003417 p = WRITE_CACHE (the device cache is ON
3418 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003419 r = IGNORE_RESIDUE (the device reports
3420 bogus residue values);
3421 s = SINGLE_LUN (the device has only one
3422 Logical Unit);
3423 w = NO_WP_DETECT (don't test whether the
3424 medium is write-protected).
3425 Example: quirks=0419:aaf5:rl,0421:0433:rc
3426
Stephen Boydac1667d2011-08-13 12:34:50 -07003427 user_debug= [KNL,ARM]
3428 Format: <int>
3429 See arch/arm/Kconfig.debug help text.
3430 1 - undefined instruction events
3431 2 - system calls
3432 4 - invalid data aborts
3433 8 - SIGSEGV faults
3434 16 - SIGBUS faults
3435 Example: user_debug=31
3436
Ian Campbell14315592010-02-17 10:38:10 +00003437 userpte=
3438 [X86] Flags controlling user PTE allocations.
3439
3440 nohigh = do not allocate PTE pages in
3441 HIGHMEM regardless of setting
3442 of CONFIG_HIGHPTE.
3443
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303444 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003445 On X86_32, this is an alias for vdso32=. Otherwise:
3446
3447 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003448 vdso=0: disable VDSO mapping
3449
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003450 vdso32= [X86] Control the 32-bit vDSO
3451 vdso32=1: enable 32-bit VDSO
3452 vdso32=0 or vdso32=2: disable 32-bit VDSO
3453
3454 See the help text for CONFIG_COMPAT_VDSO for more
3455 details. If CONFIG_COMPAT_VDSO is set, the default is
3456 vdso32=0; otherwise, the default is vdso32=1.
3457
3458 For compatibility with older kernels, vdso32=2 is an
3459 alias for vdso32=0.
3460
3461 Try vdso32=0 if you encounter an error that says:
3462 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003463
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003464 vector= [IA-64,SMP]
3465 vector=percpu: enable percpu vector domain
3466
Linus Torvalds1da177e2005-04-16 15:20:36 -07003467 video= [FB] Frame buffer configuration
3468 See Documentation/fb/modedb.txt.
3469
Aaron Lu3afe6da2013-06-20 15:08:55 +08003470 video.brightness_switch_enabled= [0,1]
3471 If set to 1, on receiving an ACPI notify event
3472 generated by hotkey, video driver will adjust brightness
3473 level and then send out the event to user space through
3474 the allocated input device; If set to 0, video driver
3475 will only send out the event without touching backlight
3476 brightness level.
3477 default: 1
3478
Pawel Moll81a054c2012-05-09 18:30:16 +01003479 virtio_mmio.device=
3480 [VMMIO] Memory mapped virtio (platform) device.
3481
3482 <size>@<baseaddr>:<irq>[:<id>]
3483 where:
3484 <size> := size (can use standard suffixes
3485 like K, M and G)
3486 <baseaddr> := physical base address
3487 <irq> := interrupt number (as passed to
3488 request_irq())
3489 <id> := (optional) platform device id
3490 example:
3491 virtio_mmio.device=1K@0x100b0000:48:7
3492
3493 Can be used multiple times for multiple devices.
3494
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003495 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003496 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003497 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003498 Use vga=ask for menu.
3499 This is actually a boot loader parameter; the value is
3500 passed to the kernel using a special protocol.
3501
Randy Dunlapa9913042005-10-23 12:57:11 -07003502 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003503 size of <nn>. This can be used to increase the
3504 minimum size (128MB on x86). It can also be used to
3505 decrease the size and leave more room for directly
3506 mapped kernel RAM.
3507
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003508 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3509 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003510
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003511 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3512 Format: <command>
3513
3514 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3515 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003516
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003517 vsyscall= [X86-64]
3518 Controls the behavior of vsyscalls (i.e. calls to
3519 fixed addresses of 0xffffffffff600x00 from legacy
3520 code). Most statically-linked binaries and older
3521 versions of glibc use these calls. Because these
3522 functions are at fixed addresses, they make nice
3523 targets for exploits that can control RIP.
3524
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003525 emulate [default] Vsyscalls turn into traps and are
3526 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003527
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003528 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003529 This is a little bit faster than trapping
3530 and makes a few dynamic recompilers work
3531 better than they would in emulation mode.
3532 It also makes exploits much easier to write.
3533
3534 none Vsyscalls don't work at all. This makes
3535 them quite hard to use for exploits but
3536 might break your system.
3537
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003538 vt.color= [VT] Default text color.
3539 Format: 0xYX, X = foreground, Y = background.
3540 Default: 0x07 = light gray on black.
3541
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003542 vt.cur_default= [VT] Default cursor shape.
3543 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3544 the parameters of the <Esc>[?A;B;Cc escape sequence;
3545 see VGA-softcursor.txt. Default: 2 = underline.
3546
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003547 vt.default_blu= [VT]
3548 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3549 Change the default blue palette of the console.
3550 This is a 16-member array composed of values
3551 ranging from 0-255.
3552
3553 vt.default_grn= [VT]
3554 Format: <green0>,<green1>,<green2>,...,<green15>
3555 Change the default green palette of the console.
3556 This is a 16-member array composed of values
3557 ranging from 0-255.
3558
3559 vt.default_red= [VT]
3560 Format: <red0>,<red1>,<red2>,...,<red15>
3561 Change the default red palette of the console.
3562 This is a 16-member array composed of values
3563 ranging from 0-255.
3564
3565 vt.default_utf8=
3566 [VT]
3567 Format=<0|1>
3568 Set system-wide default UTF-8 mode for all tty's.
3569 Default is 1, i.e. UTF-8 mode is enabled for all
3570 newly opened terminals.
3571
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003572 vt.global_cursor_default=
3573 [VT]
3574 Format=<-1|0|1>
3575 Set system-wide default for whether a cursor
3576 is shown on new VTs. Default is -1,
3577 i.e. cursors will be created by default unless
3578 overridden by individual drivers. 0 will hide
3579 cursors, 1 will display them.
3580
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003581 vt.italic= [VT] Default color for italic text; 0-15.
3582 Default: 2 = green.
3583
3584 vt.underline= [VT] Default color for underlined text; 0-15.
3585 Default: 3 = cyan.
3586
Randy Dunlap4724ba52010-05-03 11:42:52 -07003587 watchdog timers [HW,WDT] For information on watchdog timers,
3588 see Documentation/watchdog/watchdog-parameters.txt
3589 or other driver-specific files in the
3590 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003591
Tejun Heod55262c2013-04-01 11:23:38 -07003592 workqueue.disable_numa
3593 By default, all work items queued to unbound
3594 workqueues are affine to the NUMA nodes they're
3595 issued on, which results in better behavior in
3596 general. If NUMA affinity needs to be disabled for
3597 whatever reason, this option can be used. Note
3598 that this also can be controlled per-workqueue for
3599 workqueues visible under /sys/bus/workqueue/.
3600
Viresh Kumarcee22a12013-04-08 16:45:40 +05303601 workqueue.power_efficient
3602 Per-cpu workqueues are generally preferred because
3603 they show better performance thanks to cache
3604 locality; unfortunately, per-cpu workqueues tend to
3605 be more power hungry than unbound workqueues.
3606
3607 Enabling this makes the per-cpu workqueues which
3608 were observed to contribute significantly to power
3609 consumption unbound, leading to measurably lower
3610 power usage at the cost of small performance
3611 overhead.
3612
3613 The default value of this parameter is determined by
3614 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3615
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003616 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3617 default x2apic cluster mode on platforms
3618 supporting x2apic.
3619
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003620 x86_intel_mid_timer= [X86-32,APBT]
3621 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003622 Two valid options are apbt timer only and lapic timer
3623 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003624 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003625
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003626 xen_emul_unplug= [HW,X86,XEN]
3627 Unplug Xen emulated devices
3628 Format: [unplug0,][unplug1]
3629 ide-disks -- unplug primary master IDE devices
3630 aux-ide-disks -- unplug non-primary-master IDE devices
3631 nics -- unplug network devices
3632 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003633 unnecessary -- unplugging emulated devices is
3634 unnecessary even if the host did not respond to
3635 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003636 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003637
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003638 xen_nopvspin [X86,XEN]
3639 Disables the ticketlock slowpath using Xen PV
3640 optimizations.
3641
Linus Torvalds1da177e2005-04-16 15:20:36 -07003642 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003643 Format:
3644 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003645
Randy Dunlapa9913042005-10-23 12:57:11 -07003646______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003647
3648TODO:
3649
Linus Torvalds1da177e2005-04-16 15:20:36 -07003650 Add more DRM drivers.