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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
Rusty Russell5888bcc2014-05-14 10:33:45 +09304The following is a consolidated list of the kernel parameters as
5implemented by the __setup(), core_param() and module_param() macros
6and sorted into English Dictionary order (defined as ignoring all
7punctuation and sorting digits before letters in a case insensitive
8manner), and with descriptions where known.
Linus Torvalds1da177e2005-04-16 15:20:36 -07009
Rusty Russell5888bcc2014-05-14 10:33:45 +093010The kernel parses parameters from the kernel command line up to "--";
11if it doesn't recognize a parameter and it doesn't contain a '.', the
12parameter gets passed to init: parameters with '=' go into init's
13environment, others are passed as command line arguments to init.
14Everything after "--" is passed as an argument to init.
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Rusty Russell5888bcc2014-05-14 10:33:45 +093016Module parameters can be specified in two ways: via the kernel command
17line with a module name prefix, or via modprobe, e.g.:
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Rusty Russell5888bcc2014-05-14 10:33:45 +093019 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Rusty Russell5888bcc2014-05-14 10:33:45 +093022Parameters for modules which are built into the kernel need to be
23specified on the kernel command line. modprobe looks through the
24kernel command line (/proc/cmdline) and collects module parameters
25when it loads a module, so the kernel command line can be used for
26loadable modules too.
Linus Torvalds1da177e2005-04-16 15:20:36 -070027
Randy Dunlapca1eda22009-05-06 16:02:58 -070028Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30can also be entered as
31 log-buf-len=1M print_fatal_signals=1
32
Rusty Russell5888bcc2014-05-14 10:33:45 +093033Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
Randy Dunlapca1eda22009-05-06 16:02:58 -070035
Stefan Richtera901ebb2006-04-01 01:43:18 +020036This document may not be entirely up to date and comprehensive. The command
37"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38module. Loadable modules, after being loaded into the running kernel, also
39reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40parameters may be changed at runtime by the command
41"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
42
Stefan Richter6585fa82006-04-01 01:44:30 +020043The parameters listed below are only valid if certain kernel build options were
44enabled and if respective hardware is present. The text in square brackets at
45the beginning of each description states the restrictions within which a
46parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100049 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070053 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020054 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080056 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070057 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070058 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000059 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040064 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070066 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070067 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050070 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070072 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080073 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050077 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020078 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070079 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070086 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070088 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070089 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070094 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070098 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -0700107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -0700109 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700111 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900113 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300118 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500120 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100124 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700129 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700132 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100134 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136In addition, the following text indicates that the option:
137
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
141
142Parameters denoted with BOOT are actually interpreted by the boot
143loader, and have no meaning to the kernel directly.
144Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500145need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146
Karsten Weiss55588702007-02-13 13:26:21 +0100147There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700148See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100149
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151a trailing = on the name of any parameter states that that parameter will
152be entered as an environment variable, whereas its absence indicates that
153it will appear as a kernel argument readable via /proc/cmdline by programs
154running once the system is up.
155
jens m. noedler9c4751f2006-09-29 02:00:27 -0700156The number of kernel parameters is not limited, but the length of the
157complete command line (parameters including spaces etc.) is limited to
158a fixed number of characters. This limit depends on the architecture
159and is between 256 and 4096 characters. It is defined in the file
160./include/asm/setup.h as COMMAND_LINE_SIZE.
161
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800162Finally, the [KMG] suffix is commonly described after a number of kernel
163parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165bytes respectively. Such letter suffixes can also be entirely omitted.
166
jens m. noedler9c4751f2006-09-29 02:00:27 -0700167
Al Stoneb10d79f2015-03-24 14:02:41 +0000168 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800169 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500170 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700174 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800176 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800177 copy_dsdt -- copy DSDT to memory
Al Stoneb10d79f2015-03-24 14:02:41 +0000178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179
Paul Bolle395cf962011-08-15 02:02:26 +0200180 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181
Takao Indoh4996c022011-07-14 18:05:21 -0400182 acpi_rsdp= [ACPI,EFI,KEXEC]
183 Pass the RSDP address to the kernel, mostly used
184 on machines running EFI runtime service to boot the
185 second kernel for kdump.
186
Len Browna1fdcc02007-03-11 03:26:14 -0400187 acpi_apic_instance= [ACPI, IOAPIC]
188 Format: <int>
189 2: use 2nd APIC table, if available
190 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400191 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400192
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200193 acpi_backlight= [HW,ACPI]
194 acpi_backlight=vendor
195 acpi_backlight=video
196 If set to vendor, prefer vendor specific driver
197 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
198 of the ACPI video.ko driver.
199
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700200 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
201 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700203 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204 debug output. Bits in debug_layer correspond to a
205 _COMPONENT in an ACPI source file, e.g.,
206 #define _COMPONENT ACPI_PCI_COMPONENT
207 Bits in debug_level correspond to a level in
208 ACPI_DEBUG_PRINT statements, e.g.,
209 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600210 The debug_level mask defaults to "info". See
211 Documentation/acpi/debug.txt for more information about
212 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600214 Enable processor driver info messages:
215 acpi.debug_layer=0x20000000
216 Enable PCI/PCI interrupt routing info messages:
217 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700218 Enable AML "Debug" output, i.e., stores to the Debug
219 object while interpreting AML:
220 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700221 Enable all messages related to ACPI hardware:
222 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200223
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700224 Some values produce so much output that the system is
225 unusable. The "log_buf_len" parameter may be useful
226 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800227
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800228 acpi_force_table_verification [HW,ACPI]
229 Enable table checksum verification during early stage.
230 By default, this is disabled due to x86 early mapping
231 size limitation.
232
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700233 acpi_irq_balance [HW,ACPI]
234 ACPI will balance active IRQs
235 default in APIC mode
236
237 acpi_irq_nobalance [HW,ACPI]
238 ACPI will not move active IRQs (default)
239 default in PIC mode
240
241 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242 Format: <irq>,<irq>...
243
244 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 use by PCI
246 Format: <irq>,<irq>...
247
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800248 acpi_no_auto_serialize [HW,ACPI]
249 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800250 AML control methods that contain the opcodes to create
251 named objects will be marked as "Serialized" by the
252 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800253 This feature is enabled by default.
254 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800255
Lv Zhenga94e88c2014-04-04 12:39:11 +0800256 acpi_no_static_ssdt [HW,ACPI]
257 Disable installation of static SSDTs at early boot time
258 By default, SSDTs contained in the RSDT/XSDT will be
259 installed automatically and they will appear under
260 /sys/firmware/acpi/tables.
261 This option turns off this feature.
262 Note that specifying this option does not affect
263 dynamic table installation which will install SSDT
264 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700265
Lv Zheng4dde5072014-02-11 11:01:52 +0800266 acpica_no_return_repair [HW, ACPI]
267 Disable AML predefined validation mechanism
268 This mechanism can repair the evaluation result to make
269 the return objects more ACPI specification compliant.
270 This option is useful for developers to identify the
271 root cause of an AML interpreter issue when the issue
272 has something to do with the repair mechanism.
273
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700274 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
275 Format: To spoof as Windows 98: ="Microsoft Windows"
276
277 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800278 acpi_osi="string1" # add string1
279 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800280 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800281 acpi_osi=! # disable all built-in OS vendor
282 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700283 acpi_osi= # disable all strings
284
Lv Zheng5dc17982013-07-22 16:08:25 +0800285 'acpi_osi=!' can be used in combination with single or
286 multiple 'acpi_osi="string1"' to support specific OS
287 vendor string(s). Note that such command can only
288 affect the default state of the OS vendor strings, thus
289 it cannot affect the default state of the feature group
290 strings and the current state of the OS vendor strings,
291 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800292 is meaningless. This command is useful when one do not
293 care about the state of the feature group strings which
294 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800295 Examples:
296 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298 can make '_OSI("Windows 2000")' TRUE.
299
300 'acpi_osi=' cannot be used in combination with other
301 'acpi_osi=' command lines, the _OSI method will not
302 exist in the ACPI namespace. NOTE that such command can
303 only affect the _OSI support state, thus specifying it
304 multiple times through kernel command line is also
305 meaningless.
306 Examples:
307 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
308 FALSE.
309
Lv Zheng741d8122013-07-22 16:08:36 +0800310 'acpi_osi=!*' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific
312 string(s). Note that such command can affect the
313 current state of both the OS vendor strings and the
314 feature group strings, thus specifying it multiple times
315 through kernel command line is meaningful. But it may
316 still not able to affect the final state of a string if
317 there are quirks related to this string. This command
318 is useful when one want to control the state of the
319 feature group strings to debug BIOS issues related to
320 the OSPM features.
321 Examples:
322 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323 '_OSI("Module Device")' FALSE.
324 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325 '_OSI("Module Device")' TRUE.
326 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 equivalent to
328 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 and
330 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331 they all will make '_OSI("Windows 2000")' TRUE.
332
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530333 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700334 Override the pmtimer bug detection: force the kernel
335 to assume that this machine's pmtimer latches its value
336 and always returns good values.
337
Randy Dunlap4af94f32009-04-17 18:30:28 -0700338 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
339 Format: { level | edge | high | low }
340
Randy Dunlap4af94f32009-04-17 18:30:28 -0700341 acpi_skip_timer_override [HW,ACPI]
342 Recognize and ignore IRQ0/pin2 Interrupt Override.
343 For broken nForce2 BIOS resulting in XT-PIC timer.
344
345 acpi_sleep= [HW,ACPI] Sleep options
346 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200347 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700348 See Documentation/power/video.txt for information on
349 s3_bios and s3_mode.
350 s3_beep is for debugging; it makes the PC's speaker beep
351 as soon as the kernel's real-mode entry point is called.
352 s4_nohwsig prevents ACPI hardware signature from being
353 used during resume from hibernation.
354 old_ordering causes the ACPI 1.0 ordering of the _PTS
355 control method, with respect to putting devices into
356 low power states, to be enforced (the ACPI 2.0 ordering
357 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200358 nonvs prevents the kernel from saving/restoring the
359 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800360 sci_force_enable causes the kernel to set SCI_EN directly
361 on resume from S1/S3 (which is against the ACPI spec,
362 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700363
364 acpi_use_timer_override [HW,ACPI]
365 Use timer override. For some broken Nvidia NF5 boards
366 that require a timer override, but don't have HPET
367
Luca Tettamanti7e905602009-03-30 00:01:27 +0200368 acpi_enforce_resources= [ACPI]
369 { strict | lax | no }
370 Check for resource conflicts between native drivers
371 and ACPI OperationRegions (SystemIO and SystemMemory
372 only). IO ports and memory declared in ACPI might be
373 used by the ACPI subsystem in arbitrary AML code and
374 can interfere with legacy drivers.
375 strict (default): access to resources claimed by ACPI
376 is denied; legacy drivers trying to access reserved
377 resources will fail to bind to device using them.
378 lax: access to resources claimed by ACPI is allowed;
379 legacy drivers trying to access reserved resources
380 will bind successfully but a warning message is logged.
381 no: ACPI OperationRegions are not marked as reserved,
382 no further checks are performed.
383
Prarit Bhargava00159a22014-01-14 14:21:13 -0500384 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
385 kernels.
386
Randy Dunlap4af94f32009-04-17 18:30:28 -0700387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
389
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700390 agp= [AGP]
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
395
Randy Dunlapbcfde332010-06-07 17:10:38 -0700396 ALSA [HW,ALSA]
397 See Documentation/sound/alsa/alsa-parameters.txt
398
Russell Kingd944d542010-02-20 16:13:29 +0000399 alignment= [KNL,ARM]
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
403
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
411
Borislav Petkov8360ee22011-11-21 12:10:19 +0100412 32: only for 32-bit processes
413 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
416
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
423
Sedat Dilek89e0b9a32011-12-05 23:08:32 +0100424 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200425 Pass parameters to the AMD IOMMU driver in the system.
426 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
430 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200431 off - do not initialize any AMD IOMMU found in
432 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900438
Shuah Khanc099cf12012-05-24 15:58:25 -0600439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
444
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
447 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200448 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
454
Randy Dunlapa9913042005-10-23 12:57:11 -0700455 apc= [HW,SPARC]
456 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457 Format: noidle
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
461
Randy Dunlapca1eda22009-05-06 16:02:58 -0700462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700463 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700467
Brian Haleyb0f83b22010-02-04 13:36:50 -0800468 autoconf= [IPV6]
469 See Documentation/networking/ipv6.txt.
470
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
479
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700481 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482
Linus Torvalds1da177e2005-04-16 15:20:36 -0700483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
485
486 ataflop= [HW,M68k]
487
488 atarimouse= [HW,MOUSE] Atari Mouse
489
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
492
493 atkbd.reset= [HW] Reset keyboard during initialization
494
Randy Dunlapa9913042005-10-23 12:57:11 -0700495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
499 keyboards
500
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700503
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
516 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400517 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400518
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
521 Default: 64
522
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 baycom_epp= [HW,AX25]
524 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700525
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 Format: <io>,<mode>
528 See header of drivers/net/hamradio/baycom_par.c.
529
Randy Dunlapa9913042005-10-23 12:57:11 -0700530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534
Randy Dunlapa9913042005-10-23 12:57:11 -0700535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539
Paul Gortmaker080506a2013-09-30 13:45:19 -0700540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
543
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
546 no delay (0).
547 Format: integer
548
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700552 bttv.radio= Most important insmod options are available as
553 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200555 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
559 at a time.
560
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561 c101= [NET] Moxa C101 synchronous serial card
562
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
569
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
572 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300573 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300574
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
579 others).
580
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583
Paul Menage8bab8dd2008-04-04 14:29:57 -0700584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
588 a single hierarchy
589 - foo isn't visible as an individually mountable
590 subsystem
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700594
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700602 Value can be changed at runtime via
603 /selinux/checkreqprot.
604
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100605 cio_ignore= [S390]
606 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700607 clk_ignore_unused
608 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100618
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700620 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200621 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700622 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200623 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 Format: { pit | tsc | cyclone | pmtmr }
625
John Stultz592913e2010-07-13 17:56:20 -0700626 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700627 Format: <string>
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
631 the platform:
632 [all] jiffies (this is the base, fallback clocksource)
633 [ACPI] acpi_pm
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
636 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700637 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700638 scx200_hrt on Geode; cyclone on IBM x440
639 [MIPS] MIPS
640 [PARISC] cr16
641 [S390] tod
642 [SH] SuperH
643 [SPARC64] tick
644 [X86-64] hpet,tsc
645
Andi Kleenac72e782008-01-30 13:33:21 +0100646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100650 stable over kernel options, but the vendor specific
651 ones should be.
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
657 some critical bits.
658
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700659 cma=nn[MG]@[start[MG][-end[MG]]]
660 [ARM,X86,KNL]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100666 include/linux/dma-contiguous.h
667
Robert Jennings14f966e2009-04-15 05:55:32 +0000668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
672 a hypervisor.
673 Default: yes
674
Marek Szyprowskic7909502011-12-29 13:09:51 +0100675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200677 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100678
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530679 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100680 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100681 Range: 0 - 8192
682 Default: 64
683
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700685 Format:
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
689 Format: <io>[,<irq>]
690
Randy Dunlapa9913042005-10-23 12:57:11 -0700691 com90xx= [HW,NET]
692 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 Format: <io>[,<irq>[,<memstart>]]
694
695 condev= [HW,S390] console device
696 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700697
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 console= [KNL] Output console device and options.
699
700 tty<n> Use the virtual console device <n>.
701
702 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800703 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800710 See Documentation/serial-console.txt for more
711 information. See
712 Documentation/networking/netconsole.txt for an
713 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
728
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
734 console=brl,ttyS0
735 For now, only VisioBraille is supported.
736
Daniel Mackf324edc2009-06-16 15:33:52 -0700737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
740
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800741 coredump_filter=
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
745
Len Brown62027ae2011-04-01 18:13:10 -0400746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
748
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700750 Format:
751 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800753 crashkernel=size[KMG][@offset[KMG]]
754 [KNL] Using kexec, Linux can switch to a 'crash kernel'
755 upon panic. This parameter reserves the physical
756 memory region [offset, offset + size] for that kernel
757 image. If '@offset' is omitted, then a suitable offset
758 is selected automatically. Check
759 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700760
Bernhard Wallefb391592007-10-18 23:41:02 -0700761 crashkernel=range1:size1[,range2:size2,...][@offset]
762 [KNL] Same as above, but depends on the memory
763 in the running system. The syntax of range is
764 start-[end] where start and end are both
765 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800766 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700767
Yinghai Luadbc7422013-04-15 22:23:48 -0700768 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700769 [KNL, x86_64] range could be above 4G. Allow kernel
770 to allocate physical memory region from top, so could
771 be above 4G if system have more than 4G ram installed.
772 Otherwise memory region will be allocated below 4G, if
773 available.
774 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700775 crashkernel=size[KMG],low
776 [KNL, x86_64] range under 4G. When crashkernel=X,high
777 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700778 above 4G, that cause second kernel crash on system
779 that require some amount of low memory, e.g. swiotlb
780 requires at least 64M+32K low memory. Kernel would
781 try to allocate 72M below 4G automatically.
782 This one let user to specify own low range under 4G
783 for second kernel instead.
784 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700785 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700786 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700787
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788 cs89x0_dma= [HW,NET]
789 Format: <dma>
790
791 cs89x0_media= [HW,NET]
792 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700793
Randy Dunlapa9913042005-10-23 12:57:11 -0700794 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795 See header of drivers/s390/block/dasd_devmap.c.
796
797 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
798 (one device per port)
799 Format: <port#>,<type>
800 See also Documentation/input/joystick-parport.txt
801
Thomas Renningera648ec02010-08-06 16:11:02 +0200802 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
803 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600804 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200805
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 debug [KNL] Enable kernel debugging (events log level).
807
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700808 debug_locks_verbose=
809 [KNL] verbose self-tests
810 Format=<0|1>
811 Print debugging info while doing the locking API
812 self-tests.
813 We default to 0 (no extra messages), setting it to
814 1 will print _a lot_ more information - normally
815 only useful to kernel developers.
816
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700817 debug_objects [KNL] Enable object debugging
818
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500819 no_debug_objects
820 [KNL] Disable object debugging
821
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800822 debug_guardpage_minorder=
823 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
824 parameter allows control of the order of pages that will
825 be intentionally kept free (and hence protected) by the
826 buddy allocator. Bigger value increase the probability
827 of catching random memory corruption, but reduce the
828 amount of memory for normal system use. The maximum
829 possible value is MAX_ORDER/2. Setting this parameter
830 to 1 or 2 should be enough to identify most random
831 memory corruption problems caused by bugs in kernel or
832 driver code when a CPU writes to (or reads from) a
833 random memory location. Note that there exists a class
834 of memory corruptions problems caused by buggy H/W or
835 F/W or by drivers badly programing DMA (basically when
836 memory is written at bus level and the CPU MMU is
837 bypassed) which are not detectable by
838 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
839 tracking down these problems.
840
Joonsoo Kim031bc572014-12-12 16:55:52 -0800841 debug_pagealloc=
842 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
843 parameter enables the feature at boot time. In
844 default, it is disabled. We can avoid allocating huge
845 chunk of memory for debug pagealloc if we don't enable
846 it at boot time and the system will work mostly same
847 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
848 on: enable the feature
849
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200850 debugpat [X86] Enable PAT debugging
851
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200852 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700853 Format: <area>[,<node>]
854 See also Documentation/networking/decnet.txt.
855
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700856 default_hugepagesz=
857 [same as hugepagesz=] The size of the default
858 HugeTLB page size. This is the size represented by
859 the legacy /proc/ hugepages APIs, used for SHM, and
860 default size when mounting hugetlbfs filesystems.
861 Defaults to the default architecture's huge page size
862 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700863
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 dhash_entries= [KNL]
865 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700866
Brian Haleyb0f83b22010-02-04 13:36:50 -0800867 disable= [IPV6]
868 See Documentation/networking/ipv6.txt.
869
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900870 disable_cpu_apicid= [X86,APIC,SMP]
871 Format: <int>
872 The number of initial APIC ID for the
873 corresponding CPU to be disabled at boot,
874 mostly used for the kdump 2nd kernel to
875 disable BSP to wake up multiple CPUs without
876 causing system reset or hang due to sending
877 INIT from AP to BSP.
878
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000879 disable_ddw [PPC/PSERIES]
880 Disable Dynamic DMA Window support. Use this if
881 to workaround buggy firmware.
882
Brian Haleyb0f83b22010-02-04 13:36:50 -0800883 disable_ipv6= [IPV6]
884 See Documentation/networking/ipv6.txt.
885
Yinghai Lu95ffa242008-04-29 03:52:33 -0700886 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700887 The kernel tries to adjust MTRR layout from continuous
888 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700889 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700890
Yinghai Lu093af8d2008-01-30 13:33:32 +0100891 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100892 By default the kernel will trim any uncacheable
893 memory out of your available memory pool based on
894 MTRR settings. This parameter disables that behavior,
895 possibly causing your machine to run very slowly.
896
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530897 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700898 Disable PIN 1 of APIC timer
899 Can be useful to work around chipset bugs.
900
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700901 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
902 this option disables the debugging code at boot.
903
904 dma_debug_entries=<number>
905 This option allows to tune the number of preallocated
906 entries for DMA-API debugging code. One entry is
907 required per DMA-API allocation. Use this if the
908 DMA-API debugging code disables itself because the
909 architectural default is too low.
910
Joerg Roedel1745de52009-05-22 21:49:51 +0200911 dma_debug_driver=<driver_name>
912 With this option the DMA-API debugging driver
913 filter feature can be enabled at boot time. Just
914 pass the driver to filter for as the parameter.
915 The filter can be disabled or changed to another
916 driver later using sysfs.
917
Carsten Emdeda0df922012-03-18 22:37:33 +0100918 drm_kms_helper.edid_firmware=[<connector>:]<file>
919 Broken monitors, graphic adapters and KVMs may
920 send no or incorrect EDID data sets. This parameter
921 allows to specify an EDID data set in the
922 /lib/firmware directory that is used instead.
923 Generic built-in EDID data sets are used, if one of
924 edid/1024x768.bin, edid/1280x1024.bin,
925 edid/1680x1050.bin, or edid/1920x1080.bin is given
926 and no file with the same name exists. Details and
927 instructions how to build your own EDID data are
928 available in Documentation/EDID/HOWTO.txt. An EDID
929 data set will only be used for a particular connector,
930 if its name and a colon are prepended to the EDID
931 name.
932
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 dscc4.setup= [NET]
934
Jim Cromie29e36c92012-04-27 14:30:41 -0600935 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
936 module.dyndbg[="val"]
937 Enable debug messages at boot time. See
938 Documentation/dynamic-debug-howto.txt for details.
939
Borislav Petkovf29ba612015-03-27 16:15:18 +0100940 eagerfpu= [X86]
941 on enable eager fpu restore
942 off disable eager fpu restore
943 auto selects the default scheme, which automatically
944 enables eagerfpu restore for xsaveopt.
945
Mark Salter56aeeba2014-04-07 15:39:53 -0700946 early_ioremap_debug [KNL]
947 Enable debug messages in early_ioremap support. This
948 is useful for tracking down temporary early mappings
949 which are not unmapped.
950
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700951 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500952
Michal Simek6fa62fc2014-09-10 12:43:02 +0200953 cdns,<addr>
954 Start an early, polled-mode console on a cadence serial
955 port at the specified address. The cadence serial port
956 must already be setup and configured. Options are not
957 yet supported.
958
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700959 uart[8250],io,<addr>[,options]
960 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700961 uart[8250],mmio32,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400962 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700963 Start an early, polled-mode console on the 8250/16550
964 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700965 MMIO inter-register address stride is either 8-bit
966 (mmio) or 32-bit (mmio32).
Peter Hurleyca782f12015-04-06 10:52:39 -0400967 If none of [io|mmio|mmio32], <addr> is assumed to be
968 equivalent to 'mmio'. 'options' are specified in the
969 same format described for "console=ttyS<n>"; if
970 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700971
Rob Herring0d3c6732014-04-18 17:19:57 -0500972 pl011,<addr>
973 Start an early, polled-mode console on a pl011 serial
974 port at the specified address. The pl011 serial port
975 must already be setup and configured. Options are not
976 yet supported.
977
Stephen Boyd0efe7292014-09-15 17:22:51 -0700978 msm_serial,<addr>
979 Start an early, polled-mode console on an msm serial
980 port at the specified address. The serial port
981 must already be setup and configured. Options are not
982 yet supported.
983
984 msm_serial_dm,<addr>
985 Start an early, polled-mode console on an msm serial
986 dm port at the specified address. The serial port
987 must already be setup and configured. Options are not
988 yet supported.
989
Rob Herringd50d7262014-04-18 17:19:58 -0500990 smh Use ARM semihosting calls for early console.
991
Tomasz Figab94ba032015-01-23 14:47:41 +0100992 s3c2410,<addr>
993 s3c2412,<addr>
994 s3c2440,<addr>
995 s3c6400,<addr>
996 s5pv210,<addr>
997 exynos4210,<addr>
998 Use early console provided by serial driver available
999 on Samsung SoCs, requires selecting proper type and
1000 a correct base address of the selected UART port. The
1001 serial port must already be setup and configured.
1002 Options are not yet supported.
1003
Finn Thain7913ad12014-04-12 23:48:56 +10001004 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001005 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001006 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001007 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001009 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001010 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001011 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
Dave Hansen147ea092013-04-10 14:03:38 -07001013 earlyprintk is useful when the kernel crashes before
1014 the normal console is initialized. It is not enabled by
1015 default because it has some cosmetic problems.
1016
Randy Dunlapa9913042005-10-23 12:57:11 -07001017 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001018 takes over.
1019
Matt Fleming72548e82013-10-04 09:36:56 +01001020 Only one of vga, efi, serial, or usb debug port can
1021 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022
Dave Hansen147ea092013-04-10 14:03:38 -07001023 Currently only ttyS0 and ttyS1 may be specified by
1024 name. Other I/O ports may be explicitly specified
1025 on some architectures (x86 and arm at least) by
1026 replacing ttySn with an I/O port address, like this:
1027 earlyprintk=serial,0x1008,115200
1028 You can find the port for a given device in
1029 /proc/tty/driver/serial:
1030 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001031
1032 Interaction with the standard serial driver is not
1033 very good.
1034
Matt Fleming72548e82013-10-04 09:36:56 +01001035 The VGA and EFI output is eventually overwritten by
1036 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001038 The xen output can only be used by Xen PV guests.
1039
Chen, Gongc700f012013-12-06 01:17:08 -05001040 edac_report= [HW,EDAC] Control how to report EDAC event
1041 Format: {"on" | "off" | "force"}
1042 on: enable EDAC to report H/W event. May be overridden
1043 by other higher priority error reporting module.
1044 off: disable H/W event reporting through EDAC.
1045 force: enforce the use of EDAC to report H/W event.
1046 default: on.
1047
Jason Wessel97311912010-05-20 21:04:30 -05001048 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1049 ekgdboc=kbd
1050
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001051 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001052 the boot argument: earlyprintk=vga
1053
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001055 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001057 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001058 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001059 old_map [X86-64]: switch to the old ioremap-based EFI
1060 runtime services mapping. 32-bit still uses this one by
1061 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001062 nochunk: disable reading files in "chunks" in the EFI
1063 boot stub, as chunking can cause problems with some
1064 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001065 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001066 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001067
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001068 efi_no_storage_paranoia [EFI; X86]
1069 Using this parameter you can use more than 50% of
1070 your efi variable storage. Use this parameter only if
1071 you are really sure that your UEFI does sane gc and
1072 fulfills the spec otherwise your board may brick.
1073
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 eisa_irq_edge= [PARISC,HW]
1075 See header of drivers/parisc/eisa.c.
1076
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001077 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001079 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080
1081 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001082 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001083 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001084 Documentation/block/deadline-iosched.txt for details.
1085
Michael Holzheud3bf37952011-10-30 15:16:37 +01001086 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001087 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001088 image elf header and optionally the size. Generally
1089 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001090 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001092 enable_mtrr_cleanup [X86]
1093 The kernel tries to adjust MTRR layout from continuous
1094 to discrete, to make X server driver able to add WB
1095 entry later. This parameter enables that.
1096
Randy Dunlapca1eda22009-05-06 16:02:58 -07001097 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001098 Enable PIN 1 of APIC timer
1099 Can be useful to work around chipset bugs
1100 (in particular on some ATI chipsets).
1101 The kernel tries to set a reasonable default.
1102
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 enforcing [SELINUX] Set initial enforcing status.
1104 Format: {"0" | "1"}
1105 See security/selinux/Kconfig help text.
1106 0 -- permissive (log only, no denials).
1107 1 -- enforcing (deny and log).
1108 Default value is 0.
1109 Value can be changed at runtime via /selinux/enforce.
1110
Huang Yinga08f82d2010-05-18 14:35:21 +08001111 erst_disable [ACPI]
1112 Disable Error Record Serialization Table (ERST)
1113 support.
1114
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115 ether= [HW,NET] Ethernet cards parameters
1116 This option is obsoleted by the "netdev=" option, which
1117 has equivalent usage. See its documentation for details.
1118
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001119 evm= [EVM]
1120 Format: { "fix" }
1121 Permit 'security.evm' to be updated regardless of
1122 current integrity status.
1123
Akinobu Mitade1ba092006-12-08 02:39:42 -08001124 failslab=
1125 fail_page_alloc=
1126 fail_make_request=[KNL]
1127 General fault injection mechanism.
1128 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001129 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001130
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001132 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133
Alex Chiangf13ae302008-05-08 14:03:23 -06001134 force_pal_cache_flush
1135 [IA-64] Avoid check_sal_cache_flush which may hang on
1136 buggy SAL_CACHE_FLUSH implementations. Using this
1137 parameter will force ia64_sal_cache_flush to call
1138 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1139
Chris Bainbridge69f23662014-03-07 18:40:42 +07001140 forcepae [X86-32]
1141 Forcefully enable Physical Address Extension (PAE).
1142 Many Pentium M systems disable PAE but may have a
1143 functionally usable PAE implementation.
1144 Warning: use of this parameter will taint the kernel
1145 and may cause unknown problems.
1146
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001147 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001148 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001149 as early as possible in order to facilitate early
1150 boot debugging.
1151
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001152 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001153 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001154 If no parameter is passed, ftrace will dump
1155 buffers of all CPUs, but if you pass orig_cpu, it will
1156 dump only the buffer of the CPU that triggered the
1157 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001158
1159 ftrace_filter=[function-list]
1160 [FTRACE] Limit the functions traced by the function
1161 tracer at boot up. function-list is a comma separated
1162 list of functions. This list can be changed at run
1163 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001164 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001165
1166 ftrace_notrace=[function-list]
1167 [FTRACE] Do not trace the functions specified in
1168 function-list. This list can be changed at run time
1169 by the set_ftrace_notrace file in the debugfs
1170 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001171
Stefan Assmann369bc182009-10-12 22:17:21 +02001172 ftrace_graph_filter=[function-list]
1173 [FTRACE] Limit the top level callers functions traced
1174 by the function graph tracer at boot up.
1175 function-list is a comma separated list of functions
1176 that can be changed at run time by the
1177 set_graph_function file in the debugfs tracing directory.
1178
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001179 ftrace_graph_notrace=[function-list]
1180 [FTRACE] Do not trace from the functions specified in
1181 function-list. This list is a comma separated list of
1182 functions that can be changed at run time by the
1183 set_graph_notrace file in the debugfs tracing directory.
1184
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 gamecon.map[2|3]=
1186 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1187 support via parallel port (up to 5 devices per port)
1188 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1189 See also Documentation/input/joystick-parport.txt
1190
1191 gamma= [HW,DRM]
1192
Yinghai Luaaf23042008-01-30 13:33:09 +01001193 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1194 Format: off | on
1195 default: on
1196
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001197 gcov_persist= [GCOV] When non-zero (default), profiling data for
1198 kernel modules is saved and remains accessible via
1199 debugfs, even when the module is unloaded/reloaded.
1200 When zero, profiling data is discarded and associated
1201 debugfs files are removed at module unload time.
1202
Linus Torvalds1da177e2005-04-16 15:20:36 -07001203 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001204 invalid Protective MBR to be treated as GPT. If the
1205 primary GPT is corrupted, it enables the backup/alternate
1206 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001208 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1209 the "Enable 0" bit of the configuration register.
1210 Format: 0 | 1
1211 Default: 0
1212 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1213 the "Enable 0" bit of the configuration register.
1214 Format: 0 | 1
1215 Default: 0
1216 grcan.select= [HW] Select which physical interface to use.
1217 Format: 0 | 1
1218 Default: 0
1219 grcan.txsize= [HW] Sets the size of the tx buffer.
1220 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1221 Default: 1024
1222 grcan.rxsize= [HW] Sets the size of the rx buffer.
1223 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1224 Default: 1024
1225
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 hashdist= [KNL,NUMA] Large hashes allocated during boot
1227 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001228 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001229 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
1231 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1232
1233 hd= [EIDE] (E)IDE hard drive subsystem geometry
1234 Format: <cyl>,<head>,<sect>
1235
Huang Yingea8c0712010-05-18 14:35:15 +08001236 hest_disable [ACPI]
1237 Disable Hardware Error Source Table (HEST) support;
1238 corresponding firmware-first mode error processing
1239 logic will be disabled.
1240
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1242 size of <nn>. This works even on boxes that have no
1243 highmem otherwise. This also works to reduce highmem
1244 size on bigger boxes.
1245
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001246 highres= [KNL] Enable/disable high resolution timer mode.
1247 Valid parameters: "on", "off"
1248 Default: "on"
1249
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250 hisax= [HW,ISDN]
1251 See Documentation/isdn/README.HiSax.
1252
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001253 hlt [BUGS=ARM,SH]
1254
1255 hpet= [X86-32,HPET] option to control HPET usage
1256 Format: { enable (default) | disable | force |
1257 verbose }
1258 disable: disable HPET and use PIT instead
1259 force: allow force enabled of undocumented chips (ICH4,
1260 VIA, nVidia)
1261 verbose: show contents of HPET registers during setup
1262
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001263 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1264 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1265
Andi Kleenb4718e62008-07-23 21:27:51 -07001266 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1267 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001268 On x86-64 and powerpc, this option can be specified
1269 multiple times interleaved with hugepages= to reserve
1270 huge pages of different sizes. Valid pages sizes on
1271 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001272 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001273
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001274 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1275 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001276 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1277 If specified, z/VM IUCV HVC accepts connections
1278 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001279
James Hoganfdabf522012-10-09 11:00:27 +01001280 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1281 hardware thread id mappings.
1282 Format: <cpu>:<hwthread>
1283
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001284 keep_bootcon [KNL]
1285 Do not unregister boot console at start. This is only
1286 useful for debugging when something happens in the window
1287 between unregistering the boot console and initializing
1288 the real console.
1289
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001290 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001291 or register an additional I2C bus that is not
1292 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001293 Format:
1294 <bus_id>,<clkrate>
1295
Jiri Kosina36d95732008-10-06 02:51:09 -04001296 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001298 i8042.dumbkbd [HW] Pretend that controller can only read data from
1299 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300 (Don't attempt to blink the leds)
1301 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001302 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001303 i8042.noloop [HW] Disable the AUX Loopback command while probing
1304 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001306 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1308 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001309 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310 i8042.reset [HW] Reset the controller during init and cleanup
1311 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001312 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001313
1314 i810= [HW,DRM]
1315
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001316 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1317 indicates that the driver is running on unsupported
1318 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1320 does not match list of supported models.
1321 i8k.power_status
1322 [HW] Report power status in /proc/i8k
1323 (disabled by default)
1324 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1325 capability is set.
1326
Carsten Emde4dca20e2012-03-15 15:56:26 +01001327 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001328 [DRM] Invert the sense of the variable that is used to
1329 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001330 brightness value of 0 indicates backlight switched off,
1331 and the maximum of the brightness value sets the backlight
1332 to maximum brightness. If this parameter is set to 0
1333 (default) and the machine requires it, or this parameter
1334 is set to 1, a brightness value of 0 sets the backlight
1335 to maximum brightness, and the maximum of the brightness
1336 value switches the backlight off.
1337 -1 -- never invert brightness
1338 0 -- machine default
1339 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001340
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341 icn= [HW,ISDN]
1342 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1343
David Fries0af80c02009-02-25 20:28:21 +01001344 ide-core.nodma= [HW] (E)IDE subsystem
1345 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001346 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1347 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001348 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001350 ide-generic.probe-mask= [HW] (E)IDE subsystem
1351 Format: <int>
1352 Probe mask for legacy ISA IDE ports. Depending on
1353 platform up to 6 ports are supported, enabled by
1354 setting corresponding bits in the mask to 1. The
1355 default value is 0x0, which has a special meaning.
1356 On systems that have PCI, it triggers scanning the
1357 PCI bus for the first and the second port, which
1358 are then probed. On systems without PCI the value
1359 of 0x0 enables probing the two first ports as if it
1360 was 0x3.
1361
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001362 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1363 Claim all unknown PCI IDE storage controllers.
1364
Andi Kleenf039b752007-05-02 19:27:12 +02001365 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001366 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001367 Poll forces a polling idle loop that can slightly
1368 improve the performance of waking up a idle CPU, but
1369 will use a lot of power and make the system run hot.
1370 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001371 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001372 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001373 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001374
Ingo Molnar792908222006-12-06 20:40:51 -08001375 ignore_loglevel [KNL]
1376 Ignore loglevel setting - this will print /all/
1377 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001378 We also add it as printk module parameter, so users
1379 could change it dynamically, usually by
1380 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001381
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 ihash_entries= [KNL]
1383 Set number of hash buckets for inode cache.
1384
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001385 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001386 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001387 default: "enforce"
1388
Mimi Zohar07f6a792011-03-09 22:25:48 -05001389 ima_appraise_tcb [IMA]
1390 The builtin appraise policy appraises all files
1391 owned by uid=0.
1392
Mimi Zohar3323eec2009-02-04 09:06:58 -05001393 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001394 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1395 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001396 default: "sha1"
1397
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001398 The list of supported hash algorithms is defined
1399 in crypto/hash_info.h.
1400
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001401 ima_policy= [IMA]
1402 The builtin measurement policy to load during IMA
1403 setup. Specyfing "tcb" as the value, measures all
1404 programs exec'd, files mmap'd for exec, and all files
1405 opened with the read mode bit set by either the
1406 effective uid (euid=0) or uid=0.
1407 Format: "tcb"
1408
1409 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001410 Load a policy which meets the needs of the Trusted
1411 Computing Base. This means IMA will measure all
1412 programs exec'd, files mmap'd for exec, and all files
1413 opened for read by uid=0.
1414
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001415 ima_template= [IMA]
1416 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001417 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001418 Default: "ima-ng"
1419
Roberto Sassuc2426d22014-10-13 14:08:42 +02001420 ima_template_fmt=
1421 [IMA] Define a custom template format.
1422 Format: { "field1|...|fieldN" }
1423
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001424 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1425 Format: <min_file_size>
1426 Set the minimal file size for using asynchronous hash.
1427 If left unspecified, ahash usage is disabled.
1428
1429 ahash performance varies for different data sizes on
1430 different crypto accelerators. This option can be used
1431 to achieve the best performance for a particular HW.
1432
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001433 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1434 Format: <bufsize>
1435 Set hashing buffer size. Default: 4k.
1436
1437 ahash performance varies for different chunk sizes on
1438 different crypto accelerators. This option can be used
1439 to achieve best performance for particular HW.
1440
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441 init= [KNL]
1442 Format: <full_path>
1443 Run specified binary instead of /sbin/init as init
1444 process.
1445
1446 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1447 for working out where the kernel is dying during
1448 startup.
1449
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001450 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1451 initcall functions. Useful for debugging built-in
1452 modules and initcalls.
1453
Linus Torvalds1da177e2005-04-16 15:20:36 -07001454 initrd= [BOOT] Specify the location of the initial ramdisk
1455
1456 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1457 Format: <irq>
1458
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001459 int_pln_enable [x86] Enable power limit notification interrupt
1460
Mimi Zohard726d8d2013-03-18 14:48:02 -04001461 integrity_audit=[IMA]
1462 Format: { "0" | "1" }
1463 0 -- basic integrity auditing messages. (Default)
1464 1 -- additional integrity auditing messages.
1465
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001466 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001467 on
1468 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001469 off
1470 Disable intel iommu driver.
1471 igfx_off [Default Off]
1472 By default, gfx is mapped as normal device. If a gfx
1473 device has a dedicated DMAR unit, the DMAR unit is
1474 bypassed by not enabling DMAR with this option. In
1475 this case, gfx device will use physical address for
1476 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001477 forcedac [x86_64]
1478 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001479 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001480 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001481 than 32-bit addressing. The default is to look
1482 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001483 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001484 strict [Default Off]
1485 With this option on every unmap_single operation will
1486 result in a hardware IOTLB flush operation as opposed
1487 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001488 sp_off [Default Off]
1489 By default, super page will be supported if Intel IOMMU
1490 has the capability. With this option, super page will
1491 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001492
1493 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1494 0 disables intel_idle and fall back on acpi_idle.
1495 1 to 6 specify maximum depth of C-state.
1496
Dirk Brandewie6be26492013-02-15 22:55:10 +01001497 intel_pstate= [X86]
1498 disable
1499 Do not enable intel_pstate as the default
1500 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001501 force
1502 Enable intel_pstate on systems that prohibit it by default
1503 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1504 instead of acpi-cpufreq may disable platform features, such
1505 as thermal controls and power capping, that rely on ACPI
1506 P-States information being indicated to OSPM and therefore
1507 should be used with caution. This option does not work with
1508 processors that aren't supported by the intel_pstate driver
1509 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001510 no_hwp
1511 Do not enable hardware P state control (HWP)
1512 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001513 hwp_only
1514 Only load intel_pstate on systems which support
1515 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001516
Chris Wrightd1423d52010-07-20 11:06:49 -07001517 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001518 on enable Interrupt Remapping (default)
1519 off disable Interrupt Remapping
1520 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001521 no_x2apic_optout
1522 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001523
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001524 iomem= Disable strict checking of access to MMIO memory
1525 strict regions from userspace.
1526 relaxed
1527
1528 iommu= [x86]
1529 off
1530 force
1531 noforce
1532 biomerge
1533 panic
1534 nopanic
1535 merge
1536 nomerge
1537 forcesac
1538 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001539 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001540 nobypass [PPC/POWERNV]
1541 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001542
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001543
1544 io7= [HW] IO7 for Marvel based alpha systems
1545 See comment before marvel_specify_io7 in
1546 arch/alpha/kernel/core_marvel.c.
1547
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301548 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001549 0x80
1550 Standard port 0x80 based delay
1551 0xed
1552 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001553 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001554 Simple two microseconds delay
1555 none
1556 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001557
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001559 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560
Alan Cox200803d2005-06-28 20:45:18 -07001561 irqfixup [HW]
1562 When an interrupt is not handled search all handlers
1563 for it. Intended to get systems with badly broken
1564 firmware running.
1565
1566 irqpoll [HW]
1567 When an interrupt is not handled search all handlers
1568 for it. Also check all handlers each timer
1569 interrupt. Intended to get systems with badly broken
1570 firmware running.
1571
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001573 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574
1575 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001576 Format:
1577 <cpu number>,...,<cpu number>
1578 or
Li Zefanb225d442008-11-06 12:53:39 -08001579 <cpu number>-<cpu number>
1580 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001581 or a mixture
1582 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001583
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584 This option can be used to specify one or more CPUs
1585 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001586 algorithms. You can move a process onto or off an
1587 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001588 <cpu number> begins at 0 and the maximum value is
1589 "number of CPUs in system - 1".
1590
1591 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001592 alternative -- manually setting the CPU mask of all
1593 tasks in the system -- can cause problems and
1594 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595
Randy Dunlapa9913042005-10-23 12:57:11 -07001596 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001598 ivrs_ioapic [HW,X86_64]
1599 Provide an override to the IOAPIC-ID<->DEVICE-ID
1600 mapping provided in the IVRS ACPI table. For
1601 example, to map IOAPIC-ID decimal 10 to
1602 PCI device 00:14.0 write the parameter as:
1603 ivrs_ioapic[10]=00:14.0
1604
1605 ivrs_hpet [HW,X86_64]
1606 Provide an override to the HPET-ID<->DEVICE-ID
1607 mapping provided in the IVRS ACPI table. For
1608 example, to map HPET-ID decimal 0 to
1609 PCI device 00:14.0 write the parameter as:
1610 ivrs_hpet[0]=00:14.0
1611
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612 js= [HW,JOY] Analog joystick
1613 See Documentation/input/joystick.txt.
1614
Kees Cook24f2e022014-06-13 13:30:36 -07001615 kaslr/nokaslr [X86]
1616 Enable/disable kernel and module base offset ASLR
1617 (Address Space Layout Randomization) if built into
1618 the kernel. When CONFIG_HIBERNATION is selected,
1619 kASLR is disabled by default. When kASLR is enabled,
1620 hibernation will be disabled.
1621
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001622 keepinitrd [HW,ARM]
1623
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301624 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001625 specifies the amount of memory usable by the kernel
1626 for non-movable allocations. The requested amount is
1627 spread evenly throughout all nodes in the system. The
1628 remaining memory in each node is used for Movable
1629 pages. In the event, a node is too small to have both
1630 kernelcore and Movable pages, kernelcore pages will
1631 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001632 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001633 allocation of pages that may be reclaimed or moved
1634 by the page migration subsystem. This means that
1635 HugeTLB pages may not be allocated from this zone.
1636 Note that allocations like PTEs-from-HighMem still
1637 use the HighMem zone if it exists, and the Normal
1638 zone if it does not.
1639
Jason Wessel4fe1da42010-05-20 21:04:31 -05001640 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1641 Format: <Controller#>[,poll interval]
1642 The controller # is the number of the ehci usb debug
1643 port as it is probed via PCI. The poll interval is
1644 optional and is the number seconds in between
1645 each poll cycle to the debug port in case you need
1646 the functionality for interrupting the kernel with
1647 gdb or control-c on the dbgp connection. When
1648 not using this parameter you use sysrq-g to break into
1649 the kernel debugger.
1650
Jason Wessel84c08fd2010-05-20 21:04:24 -05001651 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001652 Requires a tty driver that supports console polling,
1653 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001654 Serial only format: <serial_device>[,baud]
1655 keyboard only format: kbd
1656 keyboard and serial format: kbd,<serial_device>[,baud]
1657 Optional Kernel mode setting:
1658 kms, kbd format: kms,kbd
1659 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001660
Jason Wessel84c08fd2010-05-20 21:04:24 -05001661 kgdbwait [KGDB] Stop kernel execution and enter the
1662 kernel debugger at the earliest opportunity.
1663
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001664 kmac= [MIPS] korina ethernet MAC address.
1665 Configure the RouterBoard 532 series on-chip
1666 Ethernet adapter MAC address.
1667
Catalin Marinas04f70332009-06-11 13:22:39 +01001668 kmemleak= [KNL] Boot-time kmemleak enable/disable
1669 Valid arguments: on, off
1670 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001671 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1672 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001673
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001674 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1675 Valid arguments: 0, 1, 2
1676 kmemcheck=0 (disabled)
1677 kmemcheck=1 (enabled)
1678 kmemcheck=2 (one-shot mode)
1679 Default: 2 (one-shot mode)
1680
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301681 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001682 in oops dumps.
1683
Andre Przywarafef07aa2009-07-10 14:20:35 +02001684 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1685 Default is 0 (don't ignore, but inject #GP)
1686
Xiao Guangronga182d872010-09-20 22:17:48 +08001687 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1688 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001689 Default is 0 (off)
1690
Andre Przywarafef07aa2009-07-10 14:20:35 +02001691 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001692 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001693
1694 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1695 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001696 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001697
Andre Przywarafef07aa2009-07-10 14:20:35 +02001698 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1699 (virtualized MMU) support on capable Intel chips.
1700 Default is 1 (enabled)
1701
1702 kvm-intel.emulate_invalid_guest_state=
1703 [KVM,Intel] Enable emulation of invalid guest states
1704 Default is 0 (disabled)
1705
1706 kvm-intel.flexpriority=
1707 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1708 Default is 1 (enabled)
1709
Sasha Levine1a72ae2011-08-09 14:28:35 +03001710 kvm-intel.nested=
1711 [KVM,Intel] Enable VMX nesting (nVMX).
1712 Default is 0 (disabled)
1713
Andre Przywarafef07aa2009-07-10 14:20:35 +02001714 kvm-intel.unrestricted_guest=
1715 [KVM,Intel] Disable unrestricted guest feature
1716 (virtualized real and unpaged mode) on capable
1717 Intel chips. Default is 1 (enabled)
1718
1719 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1720 feature (tagged TLBs) on capable Intel chips.
1721 Default is 1 (enabled)
1722
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723 l2cr= [PPC]
1724
Robert Brosea78bfbf2008-03-29 07:20:23 +11001725 l3cr= [PPC]
1726
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001727 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001728 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729
Suresh Siddha279f1462012-10-22 14:37:58 -07001730 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1731 value for LAPIC timer one-shot implementation. Default
1732 back to the programmable timer unit in the LAPIC.
1733
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301734 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001735 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001736
FD Camifcb71f62008-01-06 19:08:56 +01001737 libata.dma= [LIBATA] DMA control
1738 libata.dma=0 Disable all PATA and SATA DMA
1739 libata.dma=1 PATA and SATA Disk DMA only
1740 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001741 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001742 Combinations also work, so libata.dma=3 enables DMA
1743 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001744
Michael Prokop20308872009-08-06 00:14:10 +02001745 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1746 libata.ignore_hpa=0 keep BIOS limits (default)
1747 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001748
Dave Jones78e70c22007-09-27 11:50:13 -04001749 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1750 when set.
1751 Format: <int>
1752
Tejun Heo33267322008-02-13 09:15:09 +09001753 libata.force= [LIBATA] Force configurations. The format is comma
1754 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001755 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001756 matching port, link or device. Basically, it matches
1757 the ATA ID string printed on console by libata. If
1758 the whole ID part is omitted, the last PORT and DEVICE
1759 values are used. If ID hasn't been specified yet, the
1760 configuration applies to all ports, links and devices.
1761
1762 If only DEVICE is omitted, the parameter applies to
1763 the port and all links and devices behind it. DEVICE
1764 number of 0 either selects the first device or the
1765 first fan-out link behind PMP device. It does not
1766 select the host link. DEVICE number of 15 selects the
1767 host link and device attached to it.
1768
1769 The VAL specifies the configuration to force. As long
1770 as there's no ambiguity shortcut notation is allowed.
1771 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1772 The following configurations can be forced.
1773
1774 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1775 Any ID with matching PORT is used.
1776
1777 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1778
1779 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1780 udma[/][16,25,33,44,66,100,133] notation is also
1781 allowed.
1782
1783 * [no]ncq: Turn on or off NCQ.
1784
Tejun Heo05944bd2008-08-13 20:19:09 +09001785 * nohrst, nosrst, norst: suppress hard, soft
1786 and both resets.
1787
Dan Williamsca6d43b2012-06-21 23:41:41 -07001788 * rstonce: only attempt one reset during
1789 hot-unplug link recovery
1790
Tejun Heo43c9c592010-05-23 12:59:11 +02001791 * dump_id: dump IDENTIFY data.
1792
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001793 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1794
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001795 * disable: Disable this device.
1796
Tejun Heo33267322008-02-13 09:15:09 +09001797 If there are multiple matching configurations changing
1798 the same attribute, the last one is used.
1799
Yinghai Lu95f72d12010-07-12 14:36:09 +10001800 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001801
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001803 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001805 lockd.nlm_grace_period=P [NFS] Assign grace period.
1806 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001808 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1809 Format: <integer>
1810
1811 lockd.nlm_timeout=T [NFS] Assign timeout value.
1812 Format: <integer>
1813
1814 lockd.nlm_udpport=M [NFS] Assign UDP port.
1815 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001817 locktorture.nreaders_stress= [KNL]
1818 Set the number of locking read-acquisition kthreads.
1819 Defaults to being automatically set based on the
1820 number of online CPUs.
1821
1822 locktorture.nwriters_stress= [KNL]
1823 Set the number of locking write-acquisition kthreads.
1824
1825 locktorture.onoff_holdoff= [KNL]
1826 Set time (s) after boot for CPU-hotplug testing.
1827
1828 locktorture.onoff_interval= [KNL]
1829 Set time (s) between CPU-hotplug operations, or
1830 zero to disable CPU-hotplug testing.
1831
1832 locktorture.shuffle_interval= [KNL]
1833 Set task-shuffle interval (jiffies). Shuffling
1834 tasks allows some CPUs to go into dyntick-idle
1835 mode during the locktorture test.
1836
1837 locktorture.shutdown_secs= [KNL]
1838 Set time (s) after boot system shutdown. This
1839 is useful for hands-off automated testing.
1840
1841 locktorture.stat_interval= [KNL]
1842 Time (s) between statistics printk()s.
1843
1844 locktorture.stutter= [KNL]
1845 Time (s) to stutter testing, for example,
1846 specifying five seconds causes the test to run for
1847 five seconds, wait for five seconds, and so on.
1848 This tests the locking primitive's ability to
1849 transition abruptly to and from idle.
1850
1851 locktorture.torture_runnable= [BOOT]
1852 Start locktorture running at boot time.
1853
1854 locktorture.torture_type= [KNL]
1855 Specify the locking implementation to test.
1856
1857 locktorture.verbose= [KNL]
1858 Enable additional printk() statements.
1859
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1861 Format: <irq>
1862
1863 loglevel= All Kernel Messages with a loglevel smaller than the
1864 console loglevel will be printed to the console. It can
1865 also be changed with klogd or other programs. The
1866 loglevels are defined as follows:
1867
1868 0 (KERN_EMERG) system is unusable
1869 1 (KERN_ALERT) action must be taken immediately
1870 2 (KERN_CRIT) critical conditions
1871 3 (KERN_ERR) error conditions
1872 4 (KERN_WARNING) warning conditions
1873 5 (KERN_NOTICE) normal but significant condition
1874 6 (KERN_INFO) informational
1875 7 (KERN_DEBUG) debug-level messages
1876
Randy Dunlapc756d082011-02-20 20:08:35 -08001877 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001878 in bytes. n must be a power of two and greater
1879 than the minimal size. The minimal size is defined
1880 by LOG_BUF_SHIFT kernel config parameter. There is
1881 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1882 that allows to increase the default size depending on
1883 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884
Randy Dunlapaccaa242007-10-16 01:29:37 -07001885 logo.nologo [FB] Disables display of the built-in Linux logo.
1886 This may be used to provide more screen space for
1887 kernel log messages and is useful when debugging
1888 kernel boot problems.
1889
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890 lp=0 [LP] Specify parallel ports to use, e.g,
1891 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1892 lp=reset first parallel port). 'lp=0' disables the
1893 lp=auto printer driver. 'lp=reset' (which can be
1894 specified in addition to the ports) causes
1895 attached printers to be reset. Using
1896 lp=port1,port2,... specifies the parallel ports
1897 to associate lp devices with, starting with
1898 lp0. A port specification may be 'none' to skip
1899 that lp device, or a parport name such as
1900 'parport0'. Specifying 'lp=auto' instead of a
1901 port specification list means that device IDs
1902 from each port should be examined, to see if
1903 an IEEE 1284-compliant printer is attached; if
1904 so, the driver will manage that printer.
1905 See also header of drivers/char/lp.c.
1906
1907 lpj=n [KNL]
1908 Sets loops_per_jiffy to given constant, thus avoiding
1909 time-consuming boot-time autodetection (up to 250 ms per
1910 CPU). 0 enables autodetection (default). To determine
1911 the correct value for your kernel, boot with normal
1912 autodetection and see what value is printed. Note that
1913 on SMP systems the preset will be applied to all CPUs,
1914 which is likely to cause problems if your CPUs need
1915 significantly divergent settings. An incorrect value
1916 will cause delays in the kernel to be wrong, leading to
1917 unpredictable I/O errors and other breakage. Although
1918 unlikely, in the extreme case this might damage your
1919 hardware.
1920
1921 ltpc= [NET]
1922 Format: <io>,<irq>,<dma>
1923
Randy Dunlap16290242011-08-13 12:34:52 -07001924 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001925 (machvec) in a generic kernel.
1926 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001927
Wu Zhangjin3209e702009-07-02 23:27:12 +08001928 machtype= [Loongson] Share the same kernel image file between different
1929 yeeloong laptop.
1930 Example: machtype=lemote-yeeloong-2f-7inch
1931
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001932 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1933 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001934
1935 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001936 should make use of. maxcpus=n : n >= 0 limits the
1937 kernel to using 'n' processors. n=0 is a special case,
1938 it is equivalent to "nosmp", which also disables
1939 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940
Kay Sieversd134b002011-07-31 22:08:04 +02001941 max_loop= [LOOP] The number of loop block devices that get
1942 (loop.max_loop) unconditionally pre-created at init time. The default
1943 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1944 of statically allocating a predefined number, loop
1945 devices can be requested on-demand with the
1946 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001947
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001948 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949
Uwe Hermann71cced62008-10-20 09:32:21 -07001950 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001951
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952 md= [HW] RAID subsystems devices and level
1953 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001954
Linus Torvalds1da177e2005-04-16 15:20:36 -07001955 mdacon= [MDA]
1956 Format: <first>,<last>
1957 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001958
Linus Torvalds1da177e2005-04-16 15:20:36 -07001959 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1960 Amount of memory to be used when the kernel is not able
1961 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001962 [X86] Work as limiting max address. Use together
1963 with memmap= to avoid physical address space collisions.
1964 Without memmap= PCI devices could be placed at addresses
1965 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001967 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001968 memory.
1969
Paul Mundt6902aa82008-09-21 17:14:42 +09001970 memchunk=nn[KMG]
1971 [KNL,SH] Allow user to override the default size for
1972 per-device physically contiguous DMA buffers.
1973
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301974 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975 E820 memory map, as specified by the user.
1976 Such memmap=exactmap lines can be constructed based on
1977 BIOS output or other requirements. See the memmap=nn@ss
1978 option description.
1979
1980 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001981 [KNL] Force usage of a specific region of memory.
1982 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001983
1984 memmap=nn[KMG]#ss[KMG]
1985 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001986 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987
1988 memmap=nn[KMG]$ss[KMG]
1989 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001990 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001991 Example: Exclude memory from 0x18690000-0x1869ffff
1992 memmap=64K$0x18690000
1993 or
1994 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001995
Christoph Hellwigec776ef2015-04-01 09:12:18 +02001996 memmap=nn[KMG]!ss[KMG]
1997 [KNL,X86] Mark specific memory as protected.
1998 Region of memory to be used, from ss to ss+nn.
1999 The memory region may be marked as e820 type 12 (0xc)
2000 and is NVDIMM or ADR memory.
2001
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002002 memory_corruption_check=0/1 [X86]
2003 Some BIOSes seem to corrupt the first 64k of
2004 memory when doing things like suspend/resume.
2005 Setting this option will scan the memory
2006 looking for corruption. Enabling this will
2007 both detect corruption and prevent the kernel
2008 from using the memory being corrupted.
2009 However, its intended as a diagnostic tool; if
2010 repeatable BIOS-originated corruption always
2011 affects the same memory, you can use memmap=
2012 to prevent the kernel from using that memory.
2013
2014 memory_corruption_check_size=size [X86]
2015 By default it checks for corruption in the low
2016 64k, making this memory unavailable for normal
2017 use. Use this parameter to scan for
2018 corruption in more or less memory.
2019
2020 memory_corruption_check_period=seconds [X86]
2021 By default it checks for corruption every 60
2022 seconds. Use this parameter to check at some
2023 other rate. 0 disables periodic checking.
2024
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002025 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002026 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002027 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002028 Specifies the number of memtest passes to be
2029 performed. Each pass selects another test
2030 pattern from a given set of patterns. Memtest
2031 fills the memory with this pattern, validates
2032 memory contents and reserves bad memory
2033 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002034
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 meye.*= [HW] Set MotionEye Camera parameters
2036 See Documentation/video4linux/meye.txt.
2037
Andres Salomon8f368812007-10-12 23:04:06 +02002038 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2039 Multi-Function General Purpose Timers on AMD Geode
2040 platforms.
2041
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002042 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2043 the BIOS has incorrectly applied a workaround. TinyBIOS
2044 version 0.98 is known to be affected, 0.99 fixes the
2045 problem by letting the user disable the workaround.
2046
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 mga= [HW,DRM]
2048
Randy Dunlap1c207f952008-11-19 15:36:16 -08002049 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2050 physical address is ignored.
2051
Michel Pollet39f45d72009-05-20 11:10:31 +01002052 mini2440= [ARM,HW,KNL]
2053 Format:[0..2][b][c][t]
2054 Default: "0tb"
2055 MINI2440 configuration specification:
2056 0 - The attached screen is the 3.5" TFT
2057 1 - The attached screen is the 7" TFT
2058 2 - The VGA Shield is attached (1024x768)
2059 Leaving out the screen size parameter will not load
2060 the TFT driver, and the framebuffer will be left
2061 unconfigured.
2062 b - Enable backlight. The TFT backlight pin will be
2063 linked to the kernel VESA blanking code and a GPIO
2064 LED. This parameter is not necessary when using the
2065 VGA shield.
2066 c - Enable the s3c camera interface.
2067 t - Reserved for enabling touchscreen support. The
2068 touchscreen support is not enabled in the mainstream
2069 kernel as of 2.6.30, a preliminary port can be found
2070 in the "bleeding edge" mini2440 support kernel at
2071 http://repo.or.cz/w/linux-2.6/mini2440.git
2072
Mel Gorman6b74ab92008-07-23 21:26:49 -07002073 mminit_loglevel=
2074 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2075 parameter allows control of the logging verbosity for
2076 the additional memory initialisation checks. A value
2077 of 0 disables mminit logging and a level of 4 will
2078 log everything. Information is printed at KERN_DEBUG
2079 so loglevel=8 may also need to be specified.
2080
Rusty Russell106a4ee2012-09-26 10:09:40 +01002081 module.sig_enforce
2082 [KNL] When CONFIG_MODULE_SIG is set, this means that
2083 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002084 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002085 is always true, so this option does nothing.
2086
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 mousedev.tap_time=
2088 [MOUSE] Maximum time between finger touching and
2089 leaving touchpad surface for touch to be considered
2090 a tap and be reported as a left button click (for
2091 touchpads working in absolute mode only).
2092 Format: <msecs>
2093 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2094 reporting absolute coordinates, such as tablets
2095 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2096 reporting absolute coordinates, such as tablets
2097
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302098 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002099 is similar to kernelcore except it specifies the
2100 amount of memory used for migratable allocations.
2101 If both kernelcore and movablecore is specified,
2102 then kernelcore will be at *least* the specified
2103 value but may be more. If movablecore on its own
2104 is specified, the administrator must be careful
2105 that the amount of memory usable for all allocations
2106 is not too small.
2107
Tang Chenc5320922013-11-12 15:08:10 -08002108 movable_node [KNL,X86] Boot-time switch to enable the effects
2109 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2110
Linus Torvalds1da177e2005-04-16 15:20:36 -07002111 MTD_Partition= [MTD]
2112 Format: <name>,<region-number>,<size>,<offset>
2113
Randy Dunlapa9913042005-10-23 12:57:11 -07002114 MTD_Region= [MTD] Format:
2115 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116
2117 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002118 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002119
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002120 multitce=off [PPC] This parameter disables the use of the pSeries
2121 firmware feature for updating multiple TCE entries
2122 at a time.
2123
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002124 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2125
2126 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2127
2128 boundary - index of last SLC block on Flex-OneNAND.
2129 The remaining blocks are configured as MLC blocks.
2130 lock - Configure if Flex-OneNAND boundary should be locked.
2131 Once locked, the boundary cannot be changed.
2132 1 indicates lock status, 0 indicates unlock status.
2133
Ben Dooks9db829f2008-07-03 11:24:29 +01002134 mtdset= [ARM]
2135 ARM/S3C2412 JIVE boot control
2136
2137 See arch/arm/mach-s3c2412/mach-jive.c
2138
Linus Torvalds1da177e2005-04-16 15:20:36 -07002139 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002140 [HW] Make the MicroTouch USB driver use raw coordinates
2141 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002143 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002144 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002145 that could hold holes aka. UC entries.
2146
2147 mtrr_gran_size=nn[KMG] [X86]
2148 Used for mtrr cleanup. It is granularity of mtrr block.
2149 Default is 1.
2150 Large value could prevent small alignment from
2151 using up MTRRs.
2152
2153 mtrr_spare_reg_nr=n [X86]
2154 Format: <integer>
2155 Range: 0,7 : spare reg number
2156 Default : 1
2157 Used for mtrr cleanup. It is spare mtrr entries number.
2158 Set to 2 or more if your graphical card needs more.
2159
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2161
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 netdev= [NET] Network devices parameters
2163 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2164 Note that mem_start is often overloaded to mean
2165 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002166 This usage is only documented in each driver source
2167 file if at all.
2168
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002169 nf_conntrack.acct=
2170 [NETFILTER] Enable connection tracking flow accounting
2171 0 to disable accounting
2172 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002173 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002174
Chuck Lever306a0752010-09-17 10:54:37 -04002175 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002176 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002177
2178 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002179 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180
Chuck Lever306a0752010-09-17 10:54:37 -04002181 nfsrootdebug [NFS] enable nfsroot debugging messages.
2182 See Documentation/filesystems/nfs/nfsroot.txt.
2183
Trond Myklebusta72b4422006-01-03 09:55:41 +01002184 nfs.callback_tcpport=
2185 [NFS] set the TCP port on which the NFSv4 callback
2186 channel should listen.
2187
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002188 nfs.cache_getent=
2189 [NFS] sets the pathname to the program which is used
2190 to update the NFS client cache entries.
2191
2192 nfs.cache_getent_timeout=
2193 [NFS] sets the timeout after which an attempt to
2194 update a cache entry is deemed to have failed.
2195
Trond Myklebust58df0952006-01-03 09:55:57 +01002196 nfs.idmap_cache_timeout=
2197 [NFS] set the maximum lifetime for idmapper cache
2198 entries.
2199
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002200 nfs.enable_ino64=
2201 [NFS] enable 64-bit inode numbers.
2202 If zero, the NFS client will fake up a 32-bit inode
2203 number for the readdir() and stat() syscalls instead
2204 of returning the full 64-bit number.
2205 The default is to return 64-bit inode numbers.
2206
Trond Myklebustef159e92012-02-06 19:50:40 -05002207 nfs.max_session_slots=
2208 [NFSv4.1] Sets the maximum number of session slots
2209 the client will attempt to negotiate with the server.
2210 This limits the number of simultaneous RPC requests
2211 that the client can send to the NFSv4.1 server.
2212 Note that there is little point in setting this
2213 value higher than the max_tcp_slot_table_limit.
2214
Trond Myklebustb064eca22011-02-22 15:44:32 -08002215 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002216 [NFSv4] When set to the default of '1', this option
2217 ensures that both the RPC level authentication
2218 scheme and the NFS level operations agree to use
2219 numeric uids/gids if the mount is using the
2220 'sec=sys' security flavour. In effect it is
2221 disabling idmapping, which can make migration from
2222 legacy NFSv2/v3 systems to NFSv4 easier.
2223 Servers that do not support this mode of operation
2224 will be autodetected by the client, and it will fall
2225 back to using the idmapper.
2226 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002227 nfs.nfs4_unique_id=
2228 [NFS4] Specify an additional fixed unique ident-
2229 ification string that NFSv4 clients can insert into
2230 their nfs_client_id4 string. This is typically a
2231 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002232
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002233 nfs.send_implementation_id =
2234 [NFSv4.1] Send client implementation identification
2235 information in exchange_id requests.
2236 If zero, no implementation identification information
2237 will be sent.
2238 The default is to send the implementation identification
2239 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002240
2241 nfs.recover_lost_locks =
2242 [NFSv4] Attempt to recover locks that were lost due
2243 to a lease timeout on the server. Please note that
2244 doing this risks data corruption, since there are
2245 no guarantees that the file will remain unchanged
2246 after the locks are lost.
2247 If you want to enable the kernel legacy behaviour of
2248 attempting to recover these locks, then set this
2249 parameter to '1'.
2250 The default parameter value of '0' causes the kernel
2251 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002252
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002253 nfsd.nfs4_disable_idmapping=
2254 [NFSv4] When set to the default of '1', the NFSv4
2255 server will return only numeric uids and gids to
2256 clients using auth_sys, and will accept numeric uids
2257 and gids from such clients. This is intended to ease
2258 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002259
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002260 objlayoutdriver.osd_login_prog=
2261 [NFS] [OBJLAYOUT] sets the pathname to the program which
2262 is used to automatically discover and login into new
2263 osd-targets. Please see:
2264 Documentation/filesystems/pnfs.txt for more explanations
2265
Paul Mundt1e1030d2009-09-01 17:38:32 +09002266 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002267 when a NMI is triggered.
2268 Format: [state][,regs][,debounce][,die]
2269
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302270 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002271 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002272 Valid num: 0 or 1
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002273 0 - turn nmi_watchdog off
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002274 1 - turn nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002275 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002276 timeout occurs (or 'nopanic' to override the opposite
2277 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002278 This is useful when you use a panic=... timeout and
2279 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002280
Anton Vorontsovbff38772009-07-08 11:10:56 -07002281 netpoll.carrier_timeout=
2282 [NET] Specifies amount of time (in seconds) that
2283 netpoll should wait for a carrier. By default netpoll
2284 waits 4 seconds.
2285
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002286 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287 emulation library even if a 387 maths coprocessor
2288 is present.
2289
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002290 no_console_suspend
2291 [HW] Never suspend the console
2292 Disable suspending of consoles during suspend and
2293 hibernate operations. Once disabled, debugging
2294 messages can reach various consoles while the rest
2295 of the system is being put to sleep (ie, while
2296 debugging driver suspend/resume hooks). This may
2297 not work reliably with all consoles, but is known
2298 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002299 To facilitate more flexible debugging, we also add
2300 console_suspend, a printk module parameter to control
2301 it. Users could use console_suspend (usually
2302 /sys/module/printk/parameters/console_suspend) to
2303 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002304
Christoph Lameterc1aee212007-05-31 00:40:47 -07002305 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2306 caches in the slab allocator. Saves per-node memory,
2307 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002308
Randy Dunlapa9913042005-10-23 12:57:11 -07002309 noalign [KNL,ARM]
2310
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311 noapic [SMP,APIC] Tells the kernel to not make use of any
2312 IOAPICs that may be present in the system.
2313
Mike Galbraith5091faa2010-11-30 14:18:03 +01002314 noautogroup Disable scheduler automatic task group creation.
2315
Linus Torvalds1da177e2005-04-16 15:20:36 -07002316 nobats [PPC] Do not use BATs for mapping kernel lowmem
2317 on "Classic" PPC cores.
2318
2319 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002320
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002321 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2322
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002323 nodelayacct [KNL] Disable per-task delay accounting
2324
Linus Torvalds1da177e2005-04-16 15:20:36 -07002325 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2326
Paul Mundt6902aa82008-09-21 17:14:42 +09002327 nodsp [SH] Disable hardware DSP at boot time.
2328
Dave Youngb2e0a542014-08-14 17:15:26 +08002329 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002330
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331 noexec [IA-64]
2332
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302333 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002334 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002336 noexec=off: disable non-executable mappings
2337
H. Peter Anvin52b61792012-09-21 12:43:13 -07002338 nosmap [X86]
2339 Disable SMAP (Supervisor Mode Access Prevention)
2340 even if it is supported by processor.
2341
Fenghua Yude5397a2011-05-11 16:51:05 -07002342 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002343 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002344 even if it is supported by processor.
2345
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002346 noexec32 [X86-64]
2347 This affects only 32-bit executables.
2348 noexec32=on: enable non-executable mappings (default)
2349 read doesn't imply executable mappings
2350 noexec32=off: disable non-executable mappings
2351 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002352
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002353 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002354
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002355 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002356 register save and restore. The kernel will only save
2357 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002358
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002359 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2360
Suresh Siddha0c752a92009-05-22 12:17:45 -07002361 noxsave [BUGS=X86] Disables x86 extended register state save
2362 and restore using xsave. The kernel will fallback to
2363 enabling legacy floating-point and sse state.
2364
Fenghua Yub6f42a42014-05-29 11:12:31 -07002365 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2366 register states. The kernel will fall back to use
2367 xsave to save the states. By using this parameter,
2368 performance of saving the states is degraded because
2369 xsave doesn't support modified optimization while
2370 xsaveopt supports it on xsaveopt enabled systems.
2371
2372 noxsaves [X86] Disables xsaves and xrstors used in saving and
2373 restoring x86 extended register state in compacted
2374 form of xsave area. The kernel will fall back to use
2375 xsaveopt and xrstor to save and restore the states
2376 in standard form of xsave area. By using this
2377 parameter, xsave area per process might occupy more
2378 memory on xsaves enabled systems.
2379
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002380 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2381 wfi(ARM) instruction doesn't work correctly and not to
2382 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002383
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002384 no_file_caps Tells the kernel not to honor file capabilities. The
2385 only way then for a file to be executed with privilege
2386 is to be setuid root or executed by root.
2387
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388 nohalt [IA-64] Tells the kernel not to use the power saving
2389 function PAL_HALT_LIGHT when idle. This increases
2390 power-consumption. On the positive side, it reduces
2391 interrupt wake-up latency, which may improve performance
2392 in certain environments such as networked servers or
2393 real-time systems.
2394
Kees Cooka6e15a32014-06-13 13:30:35 -07002395 nohibernate [HIBERNATION] Disable hibernation and resume.
2396
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002397 nohz= [KNL] Boottime enable/disable dynamic ticks
2398 Valid arguments: on, off
2399 Default: on
2400
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002401 nohz_full= [KNL,BOOT]
2402 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002403 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002404 whenever possible. The boot CPU will be forced outside
2405 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002406 The CPUs in this range must also be included in the
2407 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002408
Paul Mundteeee7852009-04-02 12:31:16 +09002409 noiotrap [SH] Disables trapped I/O port accesses.
2410
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002411 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412 disable unhandled interrupt sources.
2413
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302414 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002415 broken timer IRQ sources.
2416
Linus Torvalds1da177e2005-04-16 15:20:36 -07002417 noisapnp [ISAPNP] Disables ISA PnP code.
2418
2419 noinitrd [RAM] Tells the kernel not to load any configured
2420 initial RAM disk.
2421
Weidong Han03ea8152009-04-17 16:42:15 +08002422 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2423 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002424 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002425
Linus Torvalds1da177e2005-04-16 15:20:36 -07002426 nointroute [IA-64]
2427
Randy Dunlap16290242011-08-13 12:34:52 -07002428 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002429
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002430 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2431
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002432 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2433 fault handling.
2434
Glauber Costad910f5c2011-07-11 15:28:19 -04002435 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2436 steal time is computed, but won't influence scheduler
2437 behaviour
2438
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002439 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002441 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002442
Linus Torvalds1da177e2005-04-16 15:20:36 -07002443 noltlbs [PPC] Do not use large page/tlb entries for kernel
2444 lowmem mapping on PPC40x.
2445
Horms312f1f02006-02-22 09:57:55 +09002446 nomca [IA-64] Disable machine check abort handling
2447
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002448 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002449
Andres Salomon83d73842007-10-12 23:04:06 +02002450 nomfgpt [X86-32] Disable Multi-Function General Purpose
2451 Timer usage (for AMD Geode machines).
2452
Don Zickusbda62632011-10-13 15:14:27 -04002453 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2454 shutdown the other cpus. Instead use the REBOOT_VECTOR
2455 irq.
2456
Dave Young02608be2012-02-01 10:33:14 +08002457 nomodule Disable module load
2458
Jiri Kosina016ddd92010-01-18 17:05:40 +01002459 nopat [X86] Disable PAT (page attribute table extension of
2460 pagetables) support.
2461
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002462 norandmaps Don't use address space randomization. Equivalent to
2463 echo 0 > /proc/sys/kernel/randomize_va_space
2464
Jiri Kosinabbff2162010-08-11 18:34:09 +02002465 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002466
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002467 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002468 with UP alternatives
2469
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002470 nordrand [X86] Disable kernel use of the RDRAND and
2471 RDSEED instructions even if they are supported
2472 by the processor. RDRAND and RDSEED are still
2473 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002474
Randy Dunlapa9913042005-10-23 12:57:11 -07002475 noresume [SWSUSP] Disables resume and restores original swap
2476 space.
2477
Linus Torvalds1da177e2005-04-16 15:20:36 -07002478 no-scroll [VGA] Disables scrollback.
2479 This is required for the Braillex ib80-piezo Braille
2480 reader made by F.H. Papenmeier (Germany).
2481
2482 nosbagart [IA-64]
2483
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002484 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002485
Len Brown61ec7562007-08-16 03:34:22 -04002486 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2487 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002488
Dave Jones97842212007-07-15 23:41:05 -07002489 nosoftlockup [KNL] Disable the soft-lockup detector.
2490
Linus Torvalds1da177e2005-04-16 15:20:36 -07002491 nosync [HW,M68K] Disables sync negotiation for all devices.
2492
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002493 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002494
2495 nousb [USB] Disable the USB subsystem
2496
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002497 nowatchdog [KNL] Disable both lockup detectors, i.e.
2498 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002499
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002501
Weidong Han2b2fd872009-04-17 16:42:12 +08002502 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2503
Fenghua Yuf78cff42012-11-13 11:32:38 -08002504 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2505 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2506 Some features depend on CPU0. Known dependencies are:
2507 1. Resume from suspend/hibernate depends on CPU0.
2508 Suspend/hibernate will fail if CPU0 is offline and you
2509 need to online CPU0 before suspend/hibernate.
2510 2. PIC interrupts also depend on CPU0. CPU0 can't be
2511 removed if a PIC interrupt is detected.
2512 It's said poweroff/reboot may depend on CPU0 on some
2513 machines although I haven't seen such issues so far
2514 after CPU0 is offline on a few tested machines.
2515 If the dependencies are under your control, you can
2516 turn on cpu0_hotplug.
2517
Randy Dunlap16290242011-08-13 12:34:52 -07002518 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002519 purges which is reported from either PAL_VM_SUMMARY or
2520 SAL PALO.
2521
Yinghai Lu2b633e32010-02-10 01:20:37 -08002522 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2523 could support. nr_cpus=n : n >= 1 limits the kernel to
2524 supporting 'n' processors. Later in runtime you can not
2525 use hotplug cpu feature to put more cpu back to online.
2526 just like you compile the kernel NR_CPUS=n
2527
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002528 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2529
Mel Gorman1a687c22012-11-22 11:16:36 +00002530 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2531 Allowed values are enable and disable
2532
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002533 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2534 one of ['zone', 'node', 'default'] can be specified
2535 This can be set from sysctl after boot.
2536 See Documentation/sysctl/vm.txt for details.
2537
Randy Dunlap7c4be252009-01-06 14:42:44 -08002538 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2539 See Documentation/debugging-via-ohci1394.txt for more
2540 info.
2541
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002542 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2543 Rather than timing out after 20 ms if an EC
2544 command is not properly ACKed, override the length
2545 of the timeout. We have interrupts disabled while
2546 waiting for the ACK, so if this is set too high
2547 interrupts *may* be lost!
2548
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002549 omap_mux= [OMAP] Override bootloader pin multiplexing.
2550 Format: <mux_mode0.mode_name=value>...
2551 For example, to override I2C bus2:
2552 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2553
Linus Torvalds1da177e2005-04-16 15:20:36 -07002554 oprofile.timer= [HW]
2555 Use timer interrupt instead of performance counters
2556
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002557 oprofile.cpu_type= Force an oprofile cpu type
2558 This might be useful if you have an older oprofile
2559 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002560 Format: { arch_perfmon }
2561 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002562 perfmon on Intel CPUs instead of the
2563 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002564 timer: [X86] Force use of architectural NMI
2565 timer mode (see also oprofile.timer
2566 for generic hr timer mode)
Andreas Krebbeldd3c46702011-11-25 20:03:05 +01002567 [s390] Force legacy basic mode sampling
2568 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002569
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002570 oops=panic Always panic on oopses. Default is to just kill the
2571 process, but there is a small probability of
2572 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002573 This will also cause panics on machine check exceptions.
2574 Useful together with panic=30 to trigger a reboot.
2575
Randy Dunlapbcfde332010-06-07 17:10:38 -07002576 OSS [HW,OSS]
2577 See Documentation/sound/oss/oss-parameters.txt
2578
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002579 page_owner= [KNL] Boot-time page_owner enabling option.
2580 Storage of the information about who allocated
2581 each page is disabled in default. With this switch,
2582 we can turn it on.
2583 on: enable the feature
2584
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002585 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002586 timeout > 0: seconds before rebooting
2587 timeout = 0: wait forever
2588 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002589 Format: <timeout>
2590
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002591 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2592 on a WARN().
2593
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002594 crash_kexec_post_notifiers
2595 Run kdump after running panic-notifiers and dumping
2596 kmsg. This only for the users who doubt kdump always
2597 succeeds in any situation.
2598 Note that this also increases risks of kdump failure,
2599 because some panic notifiers can make the crashed
2600 kernel more unstable.
2601
Linus Torvalds1da177e2005-04-16 15:20:36 -07002602 parkbd.port= [HW] Parallel port number the keyboard adapter is
2603 connected to, default is 0.
2604 Format: <parport#>
2605 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2606 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002607 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002608
Randy Dunlapa9913042005-10-23 12:57:11 -07002609 parport= [HW,PPT] Specify parallel ports. 0 disables.
2610 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2611 Use 'auto' to force the driver to use any
2612 IRQ/DMA settings detected (the default is to
2613 ignore detected IRQ/DMA settings because of
2614 possible conflicts). You can specify the base
2615 address, IRQ, and DMA settings; IRQ and DMA
2616 should be numbers, or 'auto' (for using detected
2617 settings on that particular port), or 'nofifo'
2618 (to avoid using a FIFO even if it is detected).
2619 Parallel ports are assigned in the order they
2620 are specified on the command line, starting
2621 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622
Randy Dunlapa9913042005-10-23 12:57:11 -07002623 parport_init_mode= [HW,PPT]
2624 Configure VIA parallel port to operate in
2625 a specific mode. This is necessary on Pegasos
2626 computer where firmware has no options for setting
2627 up parallel port mode and sets it to spp.
2628 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629 Format: [spp|ps2|epp|ecp|ecpepp]
2630
Andrew Mortondd287792006-03-23 03:00:57 -08002631 pause_on_oops=
2632 Halt all CPUs after the first oops has been printed for
2633 the specified number of seconds. This is to be used if
2634 your oopses keep scrolling off the screen.
2635
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636 pcbit= [HW,ISDN]
2637
2638 pcd. [PARIDE]
2639 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002640 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002641
Randy Dunlapa9913042005-10-23 12:57:11 -07002642 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002643 earlydump [X86] dump PCI config space before the kernel
2644 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002645 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002646 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002647 the hardware directly. Use this if your machine
2648 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002649 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002650 hardware access methods are allowed. Use this
2651 if you experience crashes upon bootup and you
2652 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002653 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002654 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002655 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002656 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002657 noaer [PCIE] If the PCIEAER kernel config parameter is
2658 enabled, this kernel boot option can be used to
2659 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002660 nodomains [PCI] Disable support for multiple PCI
2661 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302662 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002663 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002664 check_enable_amd_mmconf [X86] check for and enable
2665 properly configured MMIO access to PCI
2666 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002667 nomsi [MSI] If the PCI_MSI kernel config parameter is
2668 enabled, this kernel boot option can be used to
2669 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002670 noioapicquirk [APIC] Disable all boot interrupt quirks.
2671 Safety option to keep boot IRQs enabled. This
2672 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002673 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2674 primary IO-APIC for bridges that cannot disable
2675 boot IRQs. This fixes a source of spurious IRQs
2676 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002677 noioapicreroute [APIC] Disable workaround that uses the
2678 boot IRQ equivalent of an IRQ that connects to
2679 a chipset where boot IRQs cannot be disabled.
2680 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002681 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002682 routing table. These calls are known to be buggy
2683 on several machines and they hang the machine
2684 when used, but on other computers it's the only
2685 way to get the interrupt routing table. Try
2686 this option if the kernel is unable to allocate
2687 IRQs or discover secondary PCI buses on your
2688 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002689 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002690 Use with caution as certain devices share
2691 address decoders between ROMs and other
2692 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002693 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002694 expansion ROMs that do not already have
2695 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002696 nobar [X86] Do not assign address space to the
2697 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002698 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002699 assigned automatically to PCI devices. You can
2700 make the kernel exclude IRQs of your ISA cards
2701 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002702 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002703 of the PIRQ table (normally generated
2704 by the BIOS) if it is outside the
2705 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002706 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002707 useful if the kernel is unable to find your
2708 secondary buses and you want to tell it
2709 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002710 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002711 numbers ourselves, overriding
2712 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002713 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002714 in the BIOS $PIR table. This is needed on
2715 some systems with broken BIOSes, notably
2716 some HP Pavilion N5400 and Omnibook XE3
2717 notebooks. This will have no effect if ACPI
2718 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002719 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002720 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002721 use_crs [X86] Use PCI host bridge window information
2722 from ACPI. On BIOSes from 2008 or later, this
2723 is enabled by default. If you need to use this,
2724 please report a bug.
2725 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2726 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002727 routeirq Do IRQ routing for all PCI devices.
2728 This is normally done in pci_enable_device(),
2729 so this option is a temporary workaround
2730 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002731 skip_isa_align [X86] do not align io start addr, so can
2732 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002733 firmware [ARM] Do not re-enumerate the bus but instead
2734 just use the configuration from the
2735 bootloader. This is currently used on
2736 IXP2000 systems where the bus has to be
2737 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002738 noearly [X86] Don't do any early type 1 scanning.
2739 This might help on some broken boards which
2740 machine check when some devices' config space
2741 is read. But various workarounds are disabled
2742 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002743 bfsort Sort PCI devices into breadth-first order.
2744 This sorting is done to get a device
2745 order compatible with older (<= 2.4) kernels.
2746 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002747 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2748 tuning and use the BIOS-configured MPS defaults.
2749 pcie_bus_safe Set every device's MPS to the largest value
2750 supported by all devices below the root complex.
2751 pcie_bus_perf Set device MPS to the largest allowable MPS
2752 based on its parent bus. Also set MRRS (Max
2753 Read Request Size) to the largest supported
2754 value (no larger than the MPS that the device
2755 or bus can support) for best performance.
2756 pcie_bus_peer2peer Set every device's MPS to 128B, which
2757 every device is guaranteed to support. This
2758 configuration allows peer-to-peer DMA between
2759 any pair of devices, possibly at the cost of
2760 reduced performance. This also guarantees
2761 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002762 cbiosize=nn[KMG] The fixed amount of bus space which is
2763 reserved for the CardBus bridge's IO window.
2764 The default value is 256 bytes.
2765 cbmemsize=nn[KMG] The fixed amount of bus space which is
2766 reserved for the CardBus bridge's memory
2767 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002768 resource_alignment=
2769 Format:
2770 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2771 Specifies alignment and device to reassign
2772 aligned memory resources.
2773 If <order of align> is not specified,
2774 PAGE_SIZE is used as alignment.
2775 PCI-PCI bridge can be specified, if resource
2776 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002777 ecrc= Enable/disable PCIe ECRC (transaction layer
2778 end-to-end CRC checking).
2779 bios: Use BIOS/firmware settings. This is the
2780 the default.
2781 off: Turn ECRC off
2782 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002783 hpiosize=nn[KMG] The fixed amount of bus space which is
2784 reserved for hotplug bridge's IO window.
2785 Default size is 256 bytes.
2786 hpmemsize=nn[KMG] The fixed amount of bus space which is
2787 reserved for hotplug bridge's memory window.
2788 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002789 realloc= Enable/disable reallocating PCI bridge resources
2790 if allocations done by BIOS are too small to
2791 accommodate resources required by all child
2792 devices.
2793 off: Turn realloc off
2794 on: Turn realloc on
2795 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002796 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002797 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2798 only look for one device below a PCIe downstream
2799 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002800
Chuck Ebberte5665a42008-09-24 20:40:34 -04002801 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2802 Management.
2803 off Disable ASPM.
2804 force Enable ASPM even on devices that claim not to support it.
2805 WARNING: Forcing ASPM on may cause system lockups.
2806
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002807 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2808 nomsi Do not use MSI for PCI Express Native Hotplug (this
2809 makes all PCIe ports use INTx for hotplug services).
2810
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002811 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002812 auto Ask the BIOS whether or not to use native PCIe services
2813 associated with PCIe ports (PME, hot-plug, AER). Use
2814 them only if that is allowed by the BIOS.
2815 native Use native PCIe services associated with PCIe ports
2816 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002817 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2818 ports driver.
2819
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002820 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002821 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002822 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002823
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824 pcmv= [HW,PCMCIA] BadgePAD 4
2825
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302826 pd_ignore_unused
2827 [PM]
2828 Keep all power-domains already enabled by bootloader on,
2829 even if no driver has claimed them. This is useful
2830 for debug and development, but should not be
2831 needed on a platform with proper driver support.
2832
Linus Torvalds1da177e2005-04-16 15:20:36 -07002833 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002834 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002835
2836 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2837 boot time.
2838 Format: { 0 | 1 }
2839 See arch/parisc/kernel/pdc_chassis.c
2840
Tejun Heof58dc012009-08-14 15:00:50 +09002841 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002842 Currently supported values are "embed" and "page".
2843 Archs may support subset or none of the selections.
2844 See comments in mm/percpu.c for details on each
2845 allocator. This parameter is primarily for debugging
2846 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002847
Linus Torvalds1da177e2005-04-16 15:20:36 -07002848 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002849 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002850
2851 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002852 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002853
2854 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002855 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002856
2857 plip= [PPT,NET] Parallel port network link
2858 Format: { parport<nr> | timid | 0 }
2859 See also Documentation/parport.txt.
2860
Randy Dunlap16290242011-08-13 12:34:52 -07002861 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002862 Override pmtimer IOPort with a hex value.
2863 e.g. pmtmr=0x508
2864
Bjorn Helgaas96242112011-08-11 12:14:05 -06002865 pnp.debug=1 [PNP]
2866 Enable PNP debug messages (depends on the
2867 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2868 via /sys/module/pnp/parameters/debug. We always show
2869 current resource usage; turning this on also shows
2870 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002871
Linus Torvalds1da177e2005-04-16 15:20:36 -07002872 pnpacpi= [ACPI]
2873 { off }
2874
2875 pnpbios= [ISAPNP]
2876 { on | off | curr | res | no-curr | no-res }
2877
2878 pnp_reserve_irq=
2879 [ISAPNP] Exclude IRQs for the autoconfiguration
2880
2881 pnp_reserve_dma=
2882 [ISAPNP] Exclude DMAs for the autoconfiguration
2883
2884 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002885 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002886
2887 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002888 [ISAPNP] Exclude memory regions for the
2889 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002890 Ranges are in pairs (memory base and size).
2891
Randy Dunlap4af94f32009-04-17 18:30:28 -07002892 ports= [IP_VS_FTP] IPVS ftp helper module
2893 Default is 21.
2894 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2895 may be specified.
2896 Format: <port>,<port>....
2897
Ingo Molnar45807a12007-07-15 23:40:10 -07002898 print-fatal-signals=
2899 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002900
2901 If enabled, warn about various signal handling
2902 related application anomalies: too many signals,
2903 too many POSIX.1 timers, fatal signals causing a
2904 coredump - etc.
2905
2906 If you hit the warning due to signal overflow,
2907 you might want to try "ulimit -i unlimited".
2908
Ingo Molnar45807a12007-07-15 23:40:10 -07002909 default: off.
2910
Matthew Garrettc22ab3322012-03-05 14:59:10 -08002911 printk.always_kmsg_dump=
2912 Trigger kmsg_dump for cases other than kernel oops or
2913 panics
2914 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2915 default: disabled
2916
Randy Dunlape84845c2007-07-15 23:40:25 -07002917 printk.time= Show timing data prefixed to each printk message line
2918 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2919
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002920 processor.max_cstate= [HW,ACPI]
2921 Limit processor to maximum C-state
2922 max_cstate=9 overrides any DMI blacklist limit.
2923
2924 processor.nocst [HW,ACPI]
2925 Ignore the _CST method to determine C-states,
2926 instead using the legacy FADT method
2927
Linus Torvalds1da177e2005-04-16 15:20:36 -07002928 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002929 Format: [schedule,]<number>
2930 Param: "schedule" - profile schedule points.
2931 Param: <number> - step/bucket size as a power of 2 for
2932 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002933 Param: "sleep" - profile D-state sleeping (millisecs).
2934 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002935 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002936
Linus Torvalds1da177e2005-04-16 15:20:36 -07002937 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2938 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002939 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940
Randy Dunlapa9913042005-10-23 12:57:11 -07002941 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2942 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002943 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2944 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002945 psmouse.resetafter= [HW,MOUSE]
2946 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002947 (0 = never).
2948 psmouse.resolution=
2949 [HW,MOUSE] Set desired mouse resolution, in dpi.
2950 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002951 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002952 0 = disabled, 1 = enabled (default).
2953
Matthew Garrettdee28e72011-07-21 16:57:55 -04002954 pstore.backend= Specify the name of the pstore backend to use
2955
Linus Torvalds1da177e2005-04-16 15:20:36 -07002956 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002957 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002958
Kay Sieversdc8c8582007-08-15 12:25:38 +02002959 pty.legacy_count=
2960 [KNL] Number of legacy pty's. Overwrites compiled-in
2961 default number.
2962
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002963 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002964
Linus Torvalds1da177e2005-04-16 15:20:36 -07002965 r128= [HW,DRM]
2966
2967 raid= [HW,RAID]
2968 See Documentation/md.txt.
2969
Randy Dunlapa9913042005-10-23 12:57:11 -07002970 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002971 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002972
Linus Torvalds1da177e2005-04-16 15:20:36 -07002973 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002974 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002975
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002976 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002977 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2978 the specified list of CPUs to be no-callback CPUs.
2979 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002980 be offloaded to "rcuox/N" kthreads created for
2981 that purpose, where "x" is "b" for RCU-bh, "p"
2982 for RCU-preempt, and "s" for RCU-sched, and "N"
2983 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002984 offloaded CPUs, which can be useful for HPC and
2985 real-time workloads. It can also improve energy
2986 efficiency for asymmetric multiprocessors.
2987
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002988 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002989 Rather than requiring that offloaded CPUs
2990 (specified by rcu_nocbs= above) explicitly
2991 awaken the corresponding "rcuoN" kthreads,
2992 make these kthreads poll for callbacks.
2993 This improves the real-time response for the
2994 offloaded CPUs by relieving them of the need to
2995 wake up the corresponding kthread, but degrades
2996 energy efficiency by requiring that the kthreads
2997 periodically wake up to do the polling.
2998
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002999 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003000 Set maximum number of finished RCU callbacks to
3001 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003002
Paul E. McKenney37745d22015-01-22 18:24:08 -08003003 rcutree.gp_init_delay= [KNL]
3004 Set the number of jiffies to delay each step of
3005 RCU grace-period initialization. This only has
3006 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3007 set.
3008
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003009 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003010 Increase the number of CPUs assigned to each
3011 leaf rcu_node structure. Useful for very large
3012 systems.
3013
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003014 rcutree.jiffies_till_sched_qs= [KNL]
3015 Set required age in jiffies for a
3016 given grace period before RCU starts
3017 soliciting quiescent-state help from
3018 rcu_note_context_switch().
3019
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003020 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003021 Set delay from grace-period initialization to
3022 first attempt to force quiescent states.
3023 Units are jiffies, minimum value is zero,
3024 and maximum value is HZ.
3025
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003026 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003027 Set delay between subsequent attempts to force
3028 quiescent states. Units are jiffies, minimum
3029 value is one, and maximum value is HZ.
3030
Clark Williams21871d72014-09-12 21:21:09 -05003031 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003032 Set the SCHED_FIFO priority of the RCU per-CPU
3033 kthreads (rcuc/N). This value is also used for
3034 the priority of the RCU boost threads (rcub/N)
3035 and for the RCU grace-period kthreads (rcu_bh,
3036 rcu_preempt, and rcu_sched). If RCU_BOOST is
3037 set, valid values are 1-99 and the default is 1
3038 (the least-favored priority). Otherwise, when
3039 RCU_BOOST is not set, valid values are 0-99 and
3040 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003041
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003042 rcutree.rcu_nocb_leader_stride= [KNL]
3043 Set the number of NOCB kthread groups, which
3044 defaults to the square root of the number of
3045 CPUs. Larger numbers reduces the wakeup overhead
3046 on the per-CPU grace-period kthreads, but increases
3047 that same overhead on each group's leader.
3048
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003049 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003050 Set threshold of queued RCU callbacks beyond which
3051 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003052
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003053 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003054 Set threshold of queued RCU callbacks below which
3055 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003056
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003057 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003058 Set wakeup interval for idle CPUs that have
3059 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003060
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003061 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003062 Set wakeup interval for idle CPUs that have
3063 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3064 Lazy RCU callbacks are those which RCU can
3065 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003066
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003067 rcutorture.cbflood_inter_holdoff= [KNL]
3068 Set holdoff time (jiffies) between successive
3069 callback-flood tests.
3070
3071 rcutorture.cbflood_intra_holdoff= [KNL]
3072 Set holdoff time (jiffies) between successive
3073 bursts of callbacks within a given callback-flood
3074 test.
3075
3076 rcutorture.cbflood_n_burst= [KNL]
3077 Set the number of bursts making up a given
3078 callback-flood test. Set this to zero to
3079 disable callback-flood testing.
3080
3081 rcutorture.cbflood_n_per_burst= [KNL]
3082 Set the number of callbacks to be registered
3083 in a given burst of a callback-flood test.
3084
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003085 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003086 Set duration of force_quiescent_state bursts.
3087
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003088 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003089 Set holdoff time within force_quiescent_state bursts.
3090
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003091 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003092 Set wait time between force_quiescent_state bursts.
3093
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003094 rcutorture.gp_exp= [KNL]
3095 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003096
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003097 rcutorture.gp_normal= [KNL]
3098 Use normal (non-expedited) update-side primitives.
3099 If both gp_exp and gp_normal are set, do both.
3100 If neither gp_exp nor gp_normal are set, still
3101 do both.
3102
3103 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003104 Set callbacks/threads for rcu_barrier() testing.
3105
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003106 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003107 Set number of concurrent RCU writers. These just
3108 stress RCU, they don't participate in the actual
3109 test, hence the "fake".
3110
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003111 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003112 Set number of RCU readers.
3113
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003114 rcutorture.object_debug= [KNL]
3115 Enable debug-object double-call_rcu() testing.
3116
3117 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003118 Set time (s) after boot for CPU-hotplug testing.
3119
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003120 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003121 Set time (s) between CPU-hotplug operations, or
3122 zero to disable CPU-hotplug testing.
3123
Paul E. McKenney59da22a2014-09-12 10:36:15 -07003124 rcutorture.torture_runnable= [BOOT]
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003125 Start rcutorture running at boot time.
3126
3127 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003128 Set task-shuffle interval (s). Shuffling tasks
3129 allows some CPUs to go into dyntick-idle mode
3130 during the rcutorture test.
3131
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003132 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003133 Set time (s) after boot system shutdown. This
3134 is useful for hands-off automated testing.
3135
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003136 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003137 Duration of CPU stall (s) to test RCU CPU stall
3138 warnings, zero to disable.
3139
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003140 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003141 Time to wait (s) after boot before inducing stall.
3142
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003143 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003144 Time (s) between statistics printk()s.
3145
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003146 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003147 Time (s) to stutter testing, for example, specifying
3148 five seconds causes the test to run for five seconds,
3149 wait for five seconds, and so on. This tests RCU's
3150 ability to transition abruptly to and from idle.
3151
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003152 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003153 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3154 "Maybe" means test if the RCU implementation
3155 under test support RCU priority boosting.
3156
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003157 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003158 Duration (s) of each individual boost test.
3159
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003160 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003161 Interval (s) between each boost test.
3162
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003163 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003164 Test RCU's dyntick-idle handling. See also the
3165 rcutorture.shuffle_interval parameter.
3166
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003167 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003168 Specify the RCU implementation to test.
3169
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003170 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003171 Enable additional printk() statements.
3172
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003173 rcupdate.rcu_expedited= [KNL]
3174 Use expedited grace-period primitives, for
3175 example, synchronize_rcu_expedited() instead
3176 of synchronize_rcu(). This reduces latency,
3177 but can increase CPU utilization, degrade
3178 real-time latency, and degrade energy efficiency.
3179
3180 rcupdate.rcu_cpu_stall_suppress= [KNL]
3181 Suppress RCU CPU stall warning messages.
3182
3183 rcupdate.rcu_cpu_stall_timeout= [KNL]
3184 Set timeout for RCU CPU stall warning messages.
3185
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003186 rcupdate.rcu_task_stall_timeout= [KNL]
3187 Set timeout in jiffies for RCU task stall warning
3188 messages. Disable with a value less than or equal
3189 to zero.
3190
Pranith Kumar74860fe2014-09-19 11:34:09 -04003191 rcupdate.rcu_self_test= [KNL]
3192 Run the RCU early boot self tests
3193
3194 rcupdate.rcu_self_test_bh= [KNL]
3195 Run the RCU bh early boot self tests
3196
3197 rcupdate.rcu_self_test_sched= [KNL]
3198 Run the RCU sched early boot self tests
3199
Olof Johanssonffdfc402005-09-06 15:17:19 -07003200 rdinit= [KNL]
3201 Format: <full_path>
3202 Run specified binary instead of /init from the ramdisk,
3203 used for early userspace startup. See initrd.
3204
Robin Holt1b3a5d02013-07-08 16:01:42 -07003205 reboot= [KNL]
3206 Format (x86 or x86_64):
3207 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3208 [[,]s[mp]#### \
3209 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3210 [[,]f[orce]
3211 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3212 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3213 reboot_force is either force or not specified,
3214 reboot_cpu is s[mp]#### with #### being the processor
3215 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003216
Paul Jackson46b6d942008-07-04 10:00:09 -07003217 relax_domain_level=
3218 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003219 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003220
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003221 relative_sleep_states=
3222 [SUSPEND] Use sleep state labeling where the deepest
3223 state available other than hibernation is always "mem".
3224 Format: { "0" | "1" }
3225 0 -- Traditional sleep state labels.
3226 1 -- Relative sleep state labels.
3227
Linus Torvalds1da177e2005-04-16 15:20:36 -07003228 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3229
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003230 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003231 Format: nn[KMG]
3232 Reserves a hole at the top of the kernel virtual
3233 address space.
3234
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003235 reservelow= [X86]
3236 Format: nn[K]
3237 Set the amount of memory to reserve for BIOS at
3238 the bottom of the address space.
3239
Vivek Goyal7e962872006-09-27 01:50:44 -07003240 reset_devices [KNL] Force drivers to reset the underlying device
3241 during initialization.
3242
Randy Dunlapa9913042005-10-23 12:57:11 -07003243 resume= [SWSUSP]
3244 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003245 Format:
3246 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003247
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003248 resume_offset= [SWSUSP]
3249 Specify the offset from the beginning of the partition
3250 given by "resume=" at which the swap header is located,
3251 in <PAGE_SIZE> units (needed only for swap files).
3252 See Documentation/power/swsusp-and-swap-files.txt
3253
Barry Songf126f732011-10-10 23:38:41 +02003254 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3255 read the resume files
3256
Barry Song6f8d7022011-10-06 20:34:46 +02003257 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3258 Useful for devices that are detected asynchronously
3259 (e.g. USB and MMC devices).
3260
Bojan Smojverf996fc92010-09-09 23:06:23 +02003261 hibernate= [HIBERNATION]
3262 noresume Don't check if there's a hibernation image
3263 present during boot.
3264 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003265 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003266
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003267 retain_initrd [RAM] Keep initrd memory after extraction
3268
Andrew Clausen0efbb782015-01-09 20:24:55 +00003269 rfkill.default_state=
3270 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3271 etc. communication is blocked by default.
3272 1 Unblocked.
3273
3274 rfkill.master_switch_mode=
3275 0 The "airplane mode" button does nothing.
3276 1 The "airplane mode" button toggles between everything
3277 blocked and the previous configuration.
3278 2 The "airplane mode" button toggles between everything
3279 blocked and everything unblocked.
3280
Linus Torvalds1da177e2005-04-16 15:20:36 -07003281 rhash_entries= [KNL,NET]
3282 Set number of hash buckets for route cache
3283
Linus Torvalds1da177e2005-04-16 15:20:36 -07003284 ro [KNL] Mount root device read-only on boot
3285
3286 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003287 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003288
3289 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3290 mount the root filesystem
3291
3292 rootflags= [KNL] Set root filesystem mount option string
3293
3294 rootfstype= [KNL] Set root filesystem type
3295
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003296 rootwait [KNL] Wait (indefinitely) for root device to show up.
3297 Useful for devices that are detected asynchronously
3298 (e.g. USB and MMC devices).
3299
Robert Tivy5c71d612013-03-28 18:41:46 -07003300 rproc_mem=nn[KMG][@address]
3301 [KNL,ARM,CMA] Remoteproc physical memory block.
3302 Memory area to be used by remote processor image,
3303 managed by CMA.
3304
Linus Torvalds1da177e2005-04-16 15:20:36 -07003305 rw [KNL] Mount root device read-write on boot
3306
3307 S [KNL] Run init in single mode
3308
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003309 s390_iommu= [HW,S390]
3310 Set s390 IOTLB flushing mode
3311 strict
3312 With strict flushing every unmap operation will result in
3313 an IOTLB flush. Default is lazy flushing before reuse,
3314 which is faster.
3315
Linus Torvalds1da177e2005-04-16 15:20:36 -07003316 sa1100ir [NET]
3317 See drivers/net/irda/sa1100_ir.c.
3318
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003320
Mike Travisf6630112009-11-17 18:22:15 -06003321 sched_debug [KNL] Enables verbose scheduler debug messages.
3322
Mike Galbraith5307c952012-05-08 12:20:58 +02003323 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3324 xtime_lock contention on larger systems, and/or RCU lock
3325 contention on all systems with CONFIG_MAXSMP set.
3326 Format: { "0" | "1" }
3327 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3328 1 -- enable.
3329 Note: increases power consumption, thus should only be
3330 enabled if running jitter sensitive (HPC/RT) workloads.
3331
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003332 security= [SECURITY] Choose a security module to enable at boot.
3333 If this boot parameter is not specified, only the first
3334 security module asking for security registration will be
3335 loaded. An invalid security module name will be treated
3336 as if no module has been chosen.
3337
3338 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339 Format: { "0" | "1" }
3340 See security/selinux/Kconfig help text.
3341 0 -- disable.
3342 1 -- enable.
3343 Default value is set via kernel config option.
3344 If enabled at boot time, /selinux/disable can be used
3345 later to disable prior to initial policy load.
3346
John Johansenc1c124e2010-07-29 14:48:09 -07003347 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3348 Format: { "0" | "1" }
3349 See security/apparmor/Kconfig help text
3350 0 -- disable.
3351 1 -- enable.
3352 Default value is set via kernel config option.
3353
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003354 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003355
Linus Torvalds1da177e2005-04-16 15:20:36 -07003356 shapers= [NET]
3357 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003358
Yinghai Lub05f78f2008-08-22 01:32:50 -07003359 show_msr= [x86] show boot-time MSR settings
3360 Format: { <integer> }
3361 Show boot-time (BIOS-initialized) MSR settings.
3362 The parameter means the number of CPUs to show,
3363 for example 1 means boot CPU only.
3364
Linus Torvalds1da177e2005-04-16 15:20:36 -07003365 simeth= [IA-64]
3366 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003367
Linus Torvalds1da177e2005-04-16 15:20:36 -07003368 slram= [HW,MTD]
3369
Joonsoo Kim423c9292014-10-09 15:26:22 -07003370 slab_nomerge [MM]
3371 Disable merging of slabs with similar size. May be
3372 necessary if there is some reason to distinguish
3373 allocs to different slabs. Debug options disable
3374 merging on their own.
3375 For more information see Documentation/vm/slub.txt.
3376
David Rientjes3df1ccc2011-10-18 22:09:28 -07003377 slab_max_order= [MM, SLAB]
3378 Determines the maximum allowed order for slabs.
3379 A high setting may cause OOMs due to memory
3380 fragmentation. Defaults to 1 for systems with
3381 more than 32MB of RAM, 0 otherwise.
3382
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003383 slub_debug[=options[,slabs]] [MM, SLUB]
3384 Enabling slub_debug allows one to determine the
3385 culprit if slab objects become corrupted. Enabling
3386 slub_debug can create guard zones around objects and
3387 may poison objects when not in use. Also tracks the
3388 last alloc / free. For more information see
3389 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003390
3391 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003392 Determines the maximum allowed order for slabs.
3393 A high setting may cause OOMs due to memory
3394 fragmentation. For more information see
3395 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003396
3397 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003398 The minimum number of objects per slab. SLUB will
3399 increase the slab order up to slub_max_order to
3400 generate a sufficiently large slab able to contain
3401 the number of objects indicated. The higher the number
3402 of objects the smaller the overhead of tracking slabs
3403 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003404 For more information see Documentation/vm/slub.txt.
3405
3406 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003407 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003408 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003409 For more information see Documentation/vm/slub.txt.
3410
3411 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003412 Same with slab_nomerge. This is supported for legacy.
3413 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003414
Linus Torvalds1da177e2005-04-16 15:20:36 -07003415 smart2= [HW]
3416 Format: <io1>[,<io2>[,...,<io8>]]
3417
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003418 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3419 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3420 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3421 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3422 smsc-ircc2.ircc_irq= [HW] IRQ line
3423 smsc-ircc2.ircc_dma= [HW] DMA channel
3424 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3425 0: Toshiba Satellite 1800 (GP data pin select)
3426 1: Fast pin select (default)
3427 2: ATC IRMode
3428
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003429 softlockup_panic=
3430 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003431 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003432
Aaron Tomlined235872014-06-23 13:22:05 -07003433 softlockup_all_cpu_backtrace=
3434 [KNL] Should the soft-lockup detector generate
3435 backtraces on all cpus.
3436 Format: <integer>
3437
Linus Torvalds1da177e2005-04-16 15:20:36 -07003438 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003439 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003440
Linus Torvalds1da177e2005-04-16 15:20:36 -07003441 spia_io_base= [HW,MTD]
3442 spia_fio_base=
3443 spia_pedr=
3444 spia_peddr=
3445
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003446 stacktrace [FTRACE]
3447 Enabled the stack tracer on boot up.
3448
Steven Rostedt762e1202011-12-19 22:01:00 -05003449 stacktrace_filter=[function-list]
3450 [FTRACE] Limit the functions that the stack tracer
3451 will trace at boot up. function-list is a comma separated
3452 list of functions. This list can be changed at run
3453 time by the stack_trace_filter file in the debugfs
3454 tracing directory. Note, this enables stack tracing
3455 and the stacktrace above is not needed.
3456
Linus Torvalds1da177e2005-04-16 15:20:36 -07003457 sti= [PARISC,HW]
3458 Format: <num>
3459 Set the STI (builtin display/keyboard on the HP-PARISC
3460 machines) console (graphic card) which should be used
3461 as the initial boot-console.
3462 See also comment in drivers/video/console/sticore.c.
3463
3464 sti_font= [HW]
3465 See comment in drivers/video/console/sticore.c.
3466
3467 stifb= [HW]
3468 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3469
Trond Myklebustcbf11072009-08-09 15:06:19 -04003470 sunrpc.min_resvport=
3471 sunrpc.max_resvport=
3472 [NFS,SUNRPC]
3473 SunRPC servers often require that client requests
3474 originate from a privileged port (i.e. a port in the
3475 range 0 < portnr < 1024).
3476 An administrator who wishes to reserve some of these
3477 ports for other uses may adjust the range that the
3478 kernel's sunrpc client considers to be privileged
3479 using these two parameters to set the minimum and
3480 maximum port values.
3481
Greg Banks42a7fc42007-03-06 01:42:23 -08003482 sunrpc.pool_mode=
3483 [NFS]
3484 Control how the NFS server code allocates CPUs to
3485 service thread pools. Depending on how many NICs
3486 you have and where their interrupts are bound, this
3487 option will affect which CPUs will do NFS serving.
3488 Note: this parameter cannot be changed while the
3489 NFS server is running.
3490
3491 auto the server chooses an appropriate mode
3492 automatically using heuristics
3493 global a single global pool contains all CPUs
3494 percpu one pool for each CPU
3495 pernode one pool for each NUMA node (equivalent
3496 to global on non-NUMA machines)
3497
Trond Myklebustcbf11072009-08-09 15:06:19 -04003498 sunrpc.tcp_slot_table_entries=
3499 sunrpc.udp_slot_table_entries=
3500 [NFS,SUNRPC]
3501 Sets the upper limit on the number of simultaneous
3502 RPC calls that can be sent from the client to a
3503 server. Increasing these values may allow you to
3504 improve throughput, but will also increase the
3505 amount of memory reserved for use by the client.
3506
Brian Norris1d4a9c12015-02-22 21:16:49 -08003507 suspend.pm_test_delay=
3508 [SUSPEND]
3509 Sets the number of seconds to remain in a suspend test
3510 mode before resuming the system (see
3511 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3512 is set. Default value is 5.
3513
Michal Hocko07555ac2013-08-22 16:35:46 -07003514 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003515 [KNL] Enable accounting of swap in memory resource
3516 controller if no parameter or 1 is given or disable
3517 it if 0 is given (See Documentation/cgroups/memory.txt)
3518
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003519 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3520 Format: { <int> | force }
3521 <int> -- Number of I/O TLB slabs
3522 force -- force using of bounce buffers even if they
3523 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003524
Linus Torvalds1da177e2005-04-16 15:20:36 -07003525 switches= [HW,M68k]
3526
Andi Kleene52eec12010-09-08 16:54:17 +02003527 sysfs.deprecated=0|1 [KNL]
3528 Enable/disable old style sysfs layout for old udev
3529 on older distributions. When this option is enabled
3530 very new udev will not work anymore. When this option
3531 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3532 in older udev will not work anymore.
3533 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3534 the kernel configuration.
3535
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003536 sysrq_always_enabled
3537 [KNL]
3538 Ignore sysrq setting - this boot parameter will
3539 neutralize any effect of /proc/sys/kernel/sysrq.
3540 Useful for debugging.
3541
Fabian Frederick747029a2014-11-06 19:46:50 +01003542 tcpmhash_entries= [KNL,NET]
3543 Set the number of tcp_metrics_hash slots.
3544 Default value is 8192 or 16384 depending on total
3545 ram pages. This is used to specify the TCP metrics
3546 cache size. See Documentation/networking/ip-sysctl.txt
3547 "tcp_no_metrics_save" section for more details.
3548
Linus Torvalds1da177e2005-04-16 15:20:36 -07003549 tdfx= [HW,DRM]
3550
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003551 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003552 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003553 standby suspend) or "freeze" (for suspend type freeze)
3554 as the system sleep state during system startup with
3555 the optional capability to repeat N number of times.
3556 The system is woken from this state using a
3557 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003558
Linus Torvalds1da177e2005-04-16 15:20:36 -07003559 thash_entries= [KNL,NET]
3560 Set number of hash buckets for TCP connection
3561
Len Brownf8707ec2007-08-12 00:12:54 -04003562 thermal.act= [HW,ACPI]
3563 -1: disable all active trip points in all thermal zones
3564 <degrees C>: override all lowest active trip points
3565
Len Brownc52a7412007-08-14 15:49:32 -04003566 thermal.crt= [HW,ACPI]
3567 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003568 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003569
Len Brownf5487142007-08-12 00:12:44 -04003570 thermal.nocrt= [HW,ACPI]
3571 Set to disable actions on ACPI thermal zone
3572 critical and hot trip points.
3573
Len Brown72b33ef2007-08-12 00:12:17 -04003574 thermal.off= [HW,ACPI]
3575 1: disable ACPI thermal control
3576
Len Browna70cdc52007-08-12 00:12:35 -04003577 thermal.psv= [HW,ACPI]
3578 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003579 <degrees C>: override all passive trip points to this
3580 value
Len Browna70cdc52007-08-12 00:12:35 -04003581
Len Brown730ff342007-08-12 00:12:26 -04003582 thermal.tzp= [HW,ACPI]
3583 Specify global default ACPI thermal zone polling rate
3584 <deci-seconds>: poll all this frequency
3585 0: no polling (default)
3586
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003587 threadirqs [KNL]
3588 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003589 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003590
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003591 tmem [KNL,XEN]
3592 Enable the Transcendent memory driver if built-in.
3593
3594 tmem.cleancache=0|1 [KNL, XEN]
3595 Default is on (1). Disable the usage of the cleancache
3596 API to send anonymous pages to the hypervisor.
3597
3598 tmem.frontswap=0|1 [KNL, XEN]
3599 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003600 API to send swap pages to the hypervisor. If disabled
3601 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003602
3603 tmem.selfballooning=0|1 [KNL, XEN]
3604 Default is on (1). Disable the driving of swap pages
3605 to the hypervisor.
3606
3607 tmem.selfshrinking=0|1 [KNL, XEN]
3608 Default is on (1). Partial swapoff that immediately
3609 transfers pages from Xen hypervisor back to the
3610 kernel based on different criteria.
3611
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003612 topology= [S390]
3613 Format: {off | on}
3614 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003615 topology information if the hardware supports this.
3616 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003617 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003618 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003619
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003620 topology_updates= [KNL, PPC, NUMA]
3621 Format: {off}
3622 Specify if the kernel should ignore (off)
3623 topology updates sent by the hypervisor to this
3624 LPAR.
3625
Linus Torvalds1da177e2005-04-16 15:20:36 -07003626 tp720= [HW,PS2]
3627
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003628 tpm_suspend_pcr=[HW,TPM]
3629 Format: integer pcr id
3630 Specify that at suspend time, the tpm driver
3631 should extend the specified pcr with zeros,
3632 as a workaround for some chips which fail to
3633 flush the last written pcr on TPM_SaveState.
3634 This will guarantee that all the other pcrs
3635 are saved.
3636
Li Zefan9d612be2009-06-24 17:33:15 +08003637 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003638 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003639
Li Zefan020e5f82009-07-01 10:47:05 +08003640 trace_event=[event-list]
3641 [FTRACE] Set and start specified trace events in order
3642 to facilitate early boot debugging.
3643 See also Documentation/trace/events.txt
3644
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003645 trace_options=[option-list]
3646 [FTRACE] Enable or disable tracer options at boot.
3647 The option-list is a comma delimited list of options
3648 that can be enabled or disabled just as if you were
3649 to echo the option name into
3650
3651 /sys/kernel/debug/tracing/trace_options
3652
3653 For example, to enable stacktrace option (to dump the
3654 stack trace of each event), add to the command line:
3655
3656 trace_options=stacktrace
3657
3658 See also Documentation/trace/ftrace.txt "trace options"
3659 section.
3660
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003661 tp_printk[FTRACE]
3662 Have the tracepoints sent to printk as well as the
3663 tracing ring buffer. This is useful for early boot up
3664 where the system hangs or reboots and does not give the
3665 option for reading the tracing buffer or performing a
3666 ftrace_dump_on_oops.
3667
3668 To turn off having tracepoints sent to printk,
3669 echo 0 > /proc/sys/kernel/tracepoint_printk
3670 Note, echoing 1 into this file without the
3671 tracepoint_printk kernel cmdline option has no effect.
3672
3673 ** CAUTION **
3674
3675 Having tracepoints sent to printk() and activating high
3676 frequency tracepoints such as irq or sched, can cause
3677 the system to live lock.
3678
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003679 traceoff_on_warning
3680 [FTRACE] enable this option to disable tracing when a
3681 warning is hit. This turns off "tracing_on". Tracing can
3682 be enabled again by echoing '1' into the "tracing_on"
3683 file located in /sys/kernel/debug/tracing/
3684
3685 This option is useful, as it disables the trace before
3686 the WARNING dump is called, which prevents the trace to
3687 be filled with content caused by the warning output.
3688
3689 This option can also be set at run time via the sysctl
3690 option: kernel/traceoff_on_warning
3691
Jiri Kosinafcf4d8212012-03-21 16:34:02 -07003692 transparent_hugepage=
3693 [KNL]
3694 Format: [always|madvise|never]
3695 Can be used to control the default behavior of the system
3696 with respect to transparent hugepages.
3697 See Documentation/vm/transhuge.txt for more details.
3698
john stultzd3b8f882009-08-17 16:40:47 -07003699 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003700 Format: <string>
3701 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003702 disables clocksource verification at runtime, as well
3703 as the stability checks done at bootup. Used to enable
3704 high-resolution timer mode on older hardware, and in
3705 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003706 [x86] noirqtime: Do not use TSC to do irq accounting.
3707 Used to run time disable IRQ_TIME_ACCOUNTING on any
3708 platforms where RDTSC is slow and this accounting
3709 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003710
Randy Dunlapa9913042005-10-23 12:57:11 -07003711 turbografx.map[2|3]= [HW,JOY]
3712 TurboGraFX parallel port interface
3713 Format:
3714 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003715 See also Documentation/input/joystick-parport.txt
3716
Christian Kujaub6935f82011-05-31 15:22:05 +00003717 udbg-immortal [PPC] When debugging early kernel crashes that
3718 happen after console_init() and before a proper
3719 console driver takes over, this boot options might
3720 help "seeing" what's going on.
3721
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003722 uhash_entries= [KNL,NET]
3723 Set number of hash buckets for UDP/UDP-Lite connections
3724
Alan Stern5f8364b2006-12-05 16:29:55 -05003725 uhci-hcd.ignore_oc=
3726 [USB] Ignore overcurrent events (default N).
3727 Some badly-designed motherboards generate lots of
3728 bogus events, for ports that aren't wired to
3729 anything. Set this parameter to avoid log spamming.
3730 Note that genuine overcurrent events won't be
3731 reported either.
3732
Simon Arlotte3a61b02008-07-19 23:32:54 +01003733 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003734 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003735
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003736 usbcore.authorized_default=
3737 [USB] Default USB device authorization:
3738 (default -1 = authorized except for wireless USB,
3739 0 = not authorized, 1 = authorized)
3740
Alan Sternb5e795f2007-02-20 15:00:53 -05003741 usbcore.autosuspend=
3742 [USB] The autosuspend time delay (in seconds) used
3743 for newly-detected USB devices (default 2). This
3744 is the time required before an idle device will be
3745 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003746 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003747
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003748 usbcore.usbfs_snoop=
3749 [USB] Set to log all usbfs traffic (default 0 = off).
3750
3751 usbcore.blinkenlights=
3752 [USB] Set to cycle leds on hubs (default 0 = off).
3753
3754 usbcore.old_scheme_first=
3755 [USB] Start with the old device initialization
3756 scheme (default 0 = off).
3757
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003758 usbcore.usbfs_memory_mb=
3759 [USB] Memory limit (in MB) for buffers allocated by
3760 usbfs (default = 16, 0 = max = 2047).
3761
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003762 usbcore.use_both_schemes=
3763 [USB] Try the other device initialization scheme
3764 if the first one fails (default 1 = enabled).
3765
3766 usbcore.initial_descriptor_timeout=
3767 [USB] Specifies timeout for the initial 64-byte
3768 USB_REQ_GET_DESCRIPTOR request in milliseconds
3769 (default 5000 = 5.0 seconds).
3770
Linus Torvalds1da177e2005-04-16 15:20:36 -07003771 usbhid.mousepoll=
3772 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003773
Alan Sternd4f373e2008-11-10 14:07:45 -05003774 usb-storage.delay_use=
3775 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003776 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003777
3778 usb-storage.quirks=
3779 [UMS] A list of quirks entries to supplement or
3780 override the built-in unusual_devs list. List
3781 entries are separated by commas. Each entry has
3782 the form VID:PID:Flags where VID and PID are Vendor
3783 and Product ID values (4-digit hex numbers) and
3784 Flags is a set of characters, each corresponding
3785 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003786 a = SANE_SENSE (collect more than 18 bytes
3787 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003788 b = BAD_SENSE (don't collect more than 18
3789 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003790 c = FIX_CAPACITY (decrease the reported
3791 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003792 d = NO_READ_DISC_INFO (don't use
3793 READ_DISC_INFO command);
3794 e = NO_READ_CAPACITY_16 (don't use
3795 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003796 f = NO_REPORT_OPCODES (don't use report opcodes
3797 command, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003798 h = CAPACITY_HEURISTICS (decrease the
3799 reported device capacity by one
3800 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003801 i = IGNORE_DEVICE (don't bind to this
3802 device);
3803 l = NOT_LOCKABLE (don't try to lock and
3804 unlock ejectable media);
3805 m = MAX_SECTORS_64 (don't transfer more
3806 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003807 n = INITIAL_READ10 (force a retry of the
3808 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003809 o = CAPACITY_OK (accept the capacity
3810 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003811 p = WRITE_CACHE (the device cache is ON
3812 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003813 r = IGNORE_RESIDUE (the device reports
3814 bogus residue values);
3815 s = SINGLE_LUN (the device has only one
3816 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003817 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3818 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003819 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003820 w = NO_WP_DETECT (don't test whether the
3821 medium is write-protected).
3822 Example: quirks=0419:aaf5:rl,0421:0433:rc
3823
Stephen Boydac1667d2011-08-13 12:34:50 -07003824 user_debug= [KNL,ARM]
3825 Format: <int>
3826 See arch/arm/Kconfig.debug help text.
3827 1 - undefined instruction events
3828 2 - system calls
3829 4 - invalid data aborts
3830 8 - SIGSEGV faults
3831 16 - SIGBUS faults
3832 Example: user_debug=31
3833
Ian Campbell14315592010-02-17 10:38:10 +00003834 userpte=
3835 [X86] Flags controlling user PTE allocations.
3836
3837 nohigh = do not allocate PTE pages in
3838 HIGHMEM regardless of setting
3839 of CONFIG_HIGHPTE.
3840
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303841 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003842 On X86_32, this is an alias for vdso32=. Otherwise:
3843
3844 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003845 vdso=0: disable VDSO mapping
3846
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003847 vdso32= [X86] Control the 32-bit vDSO
3848 vdso32=1: enable 32-bit VDSO
3849 vdso32=0 or vdso32=2: disable 32-bit VDSO
3850
3851 See the help text for CONFIG_COMPAT_VDSO for more
3852 details. If CONFIG_COMPAT_VDSO is set, the default is
3853 vdso32=0; otherwise, the default is vdso32=1.
3854
3855 For compatibility with older kernels, vdso32=2 is an
3856 alias for vdso32=0.
3857
3858 Try vdso32=0 if you encounter an error that says:
3859 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003860
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003861 vector= [IA-64,SMP]
3862 vector=percpu: enable percpu vector domain
3863
Linus Torvalds1da177e2005-04-16 15:20:36 -07003864 video= [FB] Frame buffer configuration
3865 See Documentation/fb/modedb.txt.
3866
Aaron Lu3afe6da2013-06-20 15:08:55 +08003867 video.brightness_switch_enabled= [0,1]
3868 If set to 1, on receiving an ACPI notify event
3869 generated by hotkey, video driver will adjust brightness
3870 level and then send out the event to user space through
3871 the allocated input device; If set to 0, video driver
3872 will only send out the event without touching backlight
3873 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02003874 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08003875
Pawel Moll81a054c2012-05-09 18:30:16 +01003876 virtio_mmio.device=
3877 [VMMIO] Memory mapped virtio (platform) device.
3878
3879 <size>@<baseaddr>:<irq>[:<id>]
3880 where:
3881 <size> := size (can use standard suffixes
3882 like K, M and G)
3883 <baseaddr> := physical base address
3884 <irq> := interrupt number (as passed to
3885 request_irq())
3886 <id> := (optional) platform device id
3887 example:
3888 virtio_mmio.device=1K@0x100b0000:48:7
3889
3890 Can be used multiple times for multiple devices.
3891
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003892 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003893 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003894 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003895 Use vga=ask for menu.
3896 This is actually a boot loader parameter; the value is
3897 passed to the kernel using a special protocol.
3898
Randy Dunlapa9913042005-10-23 12:57:11 -07003899 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003900 size of <nn>. This can be used to increase the
3901 minimum size (128MB on x86). It can also be used to
3902 decrease the size and leave more room for directly
3903 mapped kernel RAM.
3904
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003905 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3906 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003907
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003908 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3909 Format: <command>
3910
3911 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3912 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003913
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003914 vsyscall= [X86-64]
3915 Controls the behavior of vsyscalls (i.e. calls to
3916 fixed addresses of 0xffffffffff600x00 from legacy
3917 code). Most statically-linked binaries and older
3918 versions of glibc use these calls. Because these
3919 functions are at fixed addresses, they make nice
3920 targets for exploits that can control RIP.
3921
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003922 emulate [default] Vsyscalls turn into traps and are
3923 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003924
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003925 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003926 This is a little bit faster than trapping
3927 and makes a few dynamic recompilers work
3928 better than they would in emulation mode.
3929 It also makes exploits much easier to write.
3930
3931 none Vsyscalls don't work at all. This makes
3932 them quite hard to use for exploits but
3933 might break your system.
3934
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003935 vt.color= [VT] Default text color.
3936 Format: 0xYX, X = foreground, Y = background.
3937 Default: 0x07 = light gray on black.
3938
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003939 vt.cur_default= [VT] Default cursor shape.
3940 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3941 the parameters of the <Esc>[?A;B;Cc escape sequence;
3942 see VGA-softcursor.txt. Default: 2 = underline.
3943
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003944 vt.default_blu= [VT]
3945 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3946 Change the default blue palette of the console.
3947 This is a 16-member array composed of values
3948 ranging from 0-255.
3949
3950 vt.default_grn= [VT]
3951 Format: <green0>,<green1>,<green2>,...,<green15>
3952 Change the default green palette of the console.
3953 This is a 16-member array composed of values
3954 ranging from 0-255.
3955
3956 vt.default_red= [VT]
3957 Format: <red0>,<red1>,<red2>,...,<red15>
3958 Change the default red palette of the console.
3959 This is a 16-member array composed of values
3960 ranging from 0-255.
3961
3962 vt.default_utf8=
3963 [VT]
3964 Format=<0|1>
3965 Set system-wide default UTF-8 mode for all tty's.
3966 Default is 1, i.e. UTF-8 mode is enabled for all
3967 newly opened terminals.
3968
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003969 vt.global_cursor_default=
3970 [VT]
3971 Format=<-1|0|1>
3972 Set system-wide default for whether a cursor
3973 is shown on new VTs. Default is -1,
3974 i.e. cursors will be created by default unless
3975 overridden by individual drivers. 0 will hide
3976 cursors, 1 will display them.
3977
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003978 vt.italic= [VT] Default color for italic text; 0-15.
3979 Default: 2 = green.
3980
3981 vt.underline= [VT] Default color for underlined text; 0-15.
3982 Default: 3 = cyan.
3983
Randy Dunlap4724ba572010-05-03 11:42:52 -07003984 watchdog timers [HW,WDT] For information on watchdog timers,
3985 see Documentation/watchdog/watchdog-parameters.txt
3986 or other driver-specific files in the
3987 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003988
Tejun Heod55262c2013-04-01 11:23:38 -07003989 workqueue.disable_numa
3990 By default, all work items queued to unbound
3991 workqueues are affine to the NUMA nodes they're
3992 issued on, which results in better behavior in
3993 general. If NUMA affinity needs to be disabled for
3994 whatever reason, this option can be used. Note
3995 that this also can be controlled per-workqueue for
3996 workqueues visible under /sys/bus/workqueue/.
3997
Viresh Kumarcee22a12013-04-08 16:45:40 +05303998 workqueue.power_efficient
3999 Per-cpu workqueues are generally preferred because
4000 they show better performance thanks to cache
4001 locality; unfortunately, per-cpu workqueues tend to
4002 be more power hungry than unbound workqueues.
4003
4004 Enabling this makes the per-cpu workqueues which
4005 were observed to contribute significantly to power
4006 consumption unbound, leading to measurably lower
4007 power usage at the cost of small performance
4008 overhead.
4009
4010 The default value of this parameter is determined by
4011 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4012
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004013 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4014 default x2apic cluster mode on platforms
4015 supporting x2apic.
4016
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004017 x86_intel_mid_timer= [X86-32,APBT]
4018 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004019 Two valid options are apbt timer only and lapic timer
4020 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004021 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004022
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004023 xen_emul_unplug= [HW,X86,XEN]
4024 Unplug Xen emulated devices
4025 Format: [unplug0,][unplug1]
4026 ide-disks -- unplug primary master IDE devices
4027 aux-ide-disks -- unplug non-primary-master IDE devices
4028 nics -- unplug network devices
4029 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004030 unnecessary -- unplugging emulated devices is
4031 unnecessary even if the host did not respond to
4032 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004033 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004034
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004035 xen_nopvspin [X86,XEN]
4036 Disables the ticketlock slowpath using Xen PV
4037 optimizations.
4038
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004039 xen_nopv [X86]
4040 Disables the PV optimizations forcing the HVM guest to
4041 run as generic HVM guest with no PV drivers.
4042
Linus Torvalds1da177e2005-04-16 15:20:36 -07004043 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004044 Format:
4045 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004046
Randy Dunlapa9913042005-10-23 12:57:11 -07004047______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004048
4049TODO:
4050
Linus Torvalds1da177e2005-04-16 15:20:36 -07004051 Add more DRM drivers.