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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
Rami Rosene58d1542015-09-26 19:27:57 +0300170 Format: { force | off | strict | noirq | rsdt |
171 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700175 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800177 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800178 copy_dsdt -- copy DSDT to memory
Al Stoneb10d79f2015-03-24 14:02:41 +0000179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
Paul Bolle395cf962011-08-15 02:02:26 +0200181 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182
Len Browna1fdcc02007-03-11 03:26:14 -0400183 acpi_apic_instance= [ACPI, IOAPIC]
184 Format: <int>
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400187 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400188
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
191 acpi_backlight=video
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
195
Dominik Brodowskief694492015-05-14 15:31:28 +0200196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
203
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200227
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800231
Dominik Brodowskief694492015-05-14 15:31:28 +0200232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
247
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
251 size limitation.
252
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
255 default in APIC mode
256
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
259 default in PIC mode
260
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
263
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 use by PCI
266 Format: <irq>,<irq>...
267
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800273 This feature is enabled by default.
274 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800275
Dominik Brodowskief694492015-05-14 15:31:28 +0200276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
277 kernels.
278
Lv Zhenga94e88c2014-04-04 12:39:11 +0800279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700288
Dominik Brodowskief694492015-05-14 15:31:28 +0200289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800293
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
296
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
302
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800306 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800307 acpi_osi=! # disable all built-in OS vendor
308 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700309 acpi_osi= # disable all strings
310
Lv Zheng5dc17982013-07-22 16:08:25 +0800311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800321 Examples:
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
325
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
331 meaningless.
332 Examples:
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
334 FALSE.
335
Lv Zheng741d8122013-07-22 16:08:36 +0800336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
346 the OSPM features.
347 Examples:
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
353 equivalent to
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
355 and
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
358
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530359 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
363
Randy Dunlap4af94f32009-04-17 18:30:28 -0700364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
366
Randy Dunlap4af94f32009-04-17 18:30:28 -0700367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
370
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200373 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700374 See Documentation/power/video.txt for information on
375 s3_bios and s3_mode.
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700389
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
393
Randy Dunlap4af94f32009-04-17 18:30:28 -0700394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
396
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700397 agp= [AGP]
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
402
Randy Dunlapbcfde332010-06-07 17:10:38 -0700403 ALSA [HW,ALSA]
404 See Documentation/sound/alsa/alsa-parameters.txt
405
Russell Kingd944d542010-02-20 16:13:29 +0000406 alignment= [KNL,ARM]
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
410
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
418
Borislav Petkov8360ee22011-11-21 12:10:19 +0100419 32: only for 32-bit processes
420 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
423
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
430
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100431 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200432 Pass parameters to the AMD IOMMU driver in the system.
433 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
437 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200438 off - do not initialize any AMD IOMMU found in
439 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900445
Shuah Khanc099cf12012-05-24 15:58:25 -0600446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
451
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
454 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200455 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
461
Randy Dunlapa9913042005-10-23 12:57:11 -0700462 apc= [HW,SPARC]
463 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 Format: noidle
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
468
Randy Dunlapca1eda22009-05-06 16:02:58 -0700469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700470 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700474
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100475 apic_extnmi= [APIC,X86] External NMI delivery setting
476 Format: { bsp (default) | all | none }
477 bsp: External NMI is delivered only to CPU 0
478 all: External NMIs are broadcast to all CPUs as a
479 backup of CPU 0
480 none: External NMI is masked for all CPUs. This is
481 useful so that a dump capture kernel won't be
482 shot down by NMI
483
Brian Haleyb0f83b22010-02-04 13:36:50 -0800484 autoconf= [IPV6]
485 See Documentation/networking/ipv6.txt.
486
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400487 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
488 Limit apic dumping. The parameter defines the maximal
489 number of local apics being dumped. Also it is possible
490 to set it to "all" by meaning -- no limit here.
491 Format: { 1 (default) | 2 | ... | all }.
492 The parameter valid if only apic=debug or
493 apic=verbose is specified.
494 Example: apic=debug show_lapic=all
495
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700497 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
500 Format: <io>,<irq>,<nodeID>
501
502 ataflop= [HW,M68k]
503
504 atarimouse= [HW,MOUSE] Atari Mouse
505
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
507 EzKey and similar keyboards
508
509 atkbd.reset= [HW] Reset keyboard during initialization
510
Randy Dunlapa9913042005-10-23 12:57:11 -0700511 atkbd.set= [HW] Select keyboard code set
512 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513
514 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
515 keyboards
516
517 atkbd.softraw= [HW] Choose between synthetic and real raw mode
518 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700519
520 atkbd.softrepeat= [HW]
521 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400523 audit= [KNL] Enable the audit sub-system
524 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500525 0 - kernel audit is disabled and can not be enabled
526 until the next reboot
527 unset - kernel audit is initialized but disabled and
528 will be fully enabled by the userspace auditd.
529 1 - kernel audit is initialized and partially enabled,
530 storing at most audit_backlog_limit messages in
531 RAM until it is fully enabled by the userspace
532 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400533 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400534
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400535 audit_backlog_limit= [KNL] Set the audit queue size limit.
536 Format: <int> (must be >=0)
537 Default: 64
538
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 baycom_epp= [HW,AX25]
540 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700541
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
543 Format: <io>,<mode>
544 See header of drivers/net/hamradio/baycom_par.c.
545
Randy Dunlapa9913042005-10-23 12:57:11 -0700546 baycom_ser_fdx= [HW,AX25]
547 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548 Format: <io>,<irq>,<mode>[,<baud>]
549 See header of drivers/net/hamradio/baycom_ser_fdx.c.
550
Randy Dunlapa9913042005-10-23 12:57:11 -0700551 baycom_ser_hdx= [HW,AX25]
552 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 Format: <io>,<irq>,<mode>
554 See header of drivers/net/hamradio/baycom_ser_hdx.c.
555
Paul Gortmaker080506a2013-09-30 13:45:19 -0700556 blkdevparts= Manual partition parsing of block device(s) for
557 embedded devices based on command line input.
558 See Documentation/block/cmdline-partition.txt
559
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700560 boot_delay= Milliseconds to delay each printk during boot.
561 Values larger than 10 seconds (10000) are changed to
562 no delay (0).
563 Format: integer
564
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700565 bootmem_debug [KNL] Enable bootmem allocator debug messages.
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700568 bttv.radio= Most important insmod options are available as
569 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200571 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000573 bulk_remove=off [PPC] This parameter disables the use of the pSeries
574 firmware feature for flushing multiple hpte entries
575 at a time.
576
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577 c101= [NET] Moxa C101 synchronous serial card
578
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700579 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 Sometimes CPU hardware bugs make them report the cache
581 size incorrectly. The kernel will attempt work arounds
582 to fix known problems, but for some CPUs it is not
583 possible to determine what the correct size should be.
584 This option provides an override for these situations.
585
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300586 ca_keys= [KEYS] This parameter identifies a specific key(s) on
587 the system trusted keyring to be used for certificate
588 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300589 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300590
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700591 cca= [MIPS] Override the kernel pages' cache coherency
592 algorithm. Accepted values range from 0 to 7
593 inclusive. See arch/mips/include/asm/pgtable-bits.h
594 for platform specific values (SB1, Loongson3 and
595 others).
596
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100597 ccw_timeout_log [S390]
598 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599
Paul Menage8bab8dd2008-04-04 14:29:57 -0700600 cgroup_disable= [KNL] Disable a particular controller
601 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800602 The effects of cgroup_disable=foo are:
603 - foo isn't auto-mounted if you mount all cgroups in
604 a single hierarchy
605 - foo isn't visible as an individually mountable
606 subsystem
607 {Currently only "memory" controller deal with this and
608 cut the overhead, others just disable the usage. So
609 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700610
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 checkreqprot [SELINUX] Set initial checkreqprot flag value.
612 Format: { "0" | "1" }
613 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700614 0 -- check protection applied by kernel (includes
615 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 1 -- check protection requested by application.
617 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700618 Value can be changed at runtime via
619 /selinux/checkreqprot.
620
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100621 cio_ignore= [S390]
622 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700623 clk_ignore_unused
624 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700625 Prevents the clock framework from automatically gating
626 clocks that have not been explicitly enabled by a Linux
627 device driver but are enabled in hardware at reset or
628 by the bootloader/firmware. Note that this does not
629 force such clocks to be always-on nor does it reserve
630 those clocks in any way. This parameter is useful for
631 debug and development, but should not be needed on a
632 platform with proper driver support. For more
633 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100634
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700635 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700636 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200637 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700638 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200639 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640 Format: { pit | tsc | cyclone | pmtmr }
641
John Stultz592913e2010-07-13 17:56:20 -0700642 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700643 Format: <string>
644 Override the default clocksource and use the clocksource
645 with the name specified.
646 Some clocksource names to choose from, depending on
647 the platform:
648 [all] jiffies (this is the base, fallback clocksource)
649 [ACPI] acpi_pm
650 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
651 pxa_timer,timer3,32k_counter,timer0_1
652 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700653 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700654 scx200_hrt on Geode; cyclone on IBM x440
655 [MIPS] MIPS
656 [PARISC] cr16
657 [S390] tod
658 [SH] SuperH
659 [SPARC64] tick
660 [X86-64] hpet,tsc
661
Andi Kleenac72e782008-01-30 13:33:21 +0100662 clearcpuid=BITNUM [X86]
663 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800664 arch/x86/include/asm/cpufeature.h for the valid bit
665 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100666 stable over kernel options, but the vendor specific
667 ones should be.
668 Also note that user programs calling CPUID directly
669 or using the feature without checking anything
670 will still see it. This just prevents it from
671 being used by the kernel or shown in /proc/cpuinfo.
672 Also note the kernel might malfunction if you disable
673 some critical bits.
674
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700675 cma=nn[MG]@[start[MG][-end[MG]]]
676 [ARM,X86,KNL]
677 Sets the size of kernel global memory area for
678 contiguous memory allocations and optionally the
679 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700680 memory allocations. A value of 0 disables CMA
681 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100682 include/linux/dma-contiguous.h
683
Robert Jennings14f966e2009-04-15 05:55:32 +0000684 cmo_free_hint= [PPC] Format: { yes | no }
685 Specify whether pages are marked as being inactive
686 when they are freed. This is used in CMO environments
687 to determine OS memory pressure for page stealing by
688 a hypervisor.
689 Default: yes
690
Marek Szyprowskic7909502011-12-29 13:09:51 +0100691 coherent_pool=nn[KMG] [ARM,KNL]
692 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200693 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100694
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530695 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100696 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100697 Range: 0 - 8192
698 Default: 64
699
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700701 Format:
702 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703
704 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
705 Format: <io>[,<irq>]
706
Randy Dunlapa9913042005-10-23 12:57:11 -0700707 com90xx= [HW,NET]
708 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 Format: <io>[,<irq>[,<memstart>]]
710
711 condev= [HW,S390] console device
712 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700713
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 console= [KNL] Output console device and options.
715
716 tty<n> Use the virtual console device <n>.
717
718 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800719 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800721 the form "bbbbpnf", where "bbbb" is the baud rate,
722 "p" is parity ("n", "o", or "e"), "n" is number of
723 bits, and "f" is flow control ("r" for RTS or
724 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800726 See Documentation/serial-console.txt for more
727 information. See
728 Documentation/networking/netconsole.txt for an
729 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700731 uart[8250],io,<addr>[,options]
732 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900733 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400734 uart[8250],mmio32,<addr>[,options]
735 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 Start an early, polled-mode console on the 8250/16550
737 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400738 switching to the matching ttyS device later.
739 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900740 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
741 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
742 to be equivalent to 'mmio'. 'options' are specified in
743 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400744 the h/w is not re-initialized.
745
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500746 hvc<n> Use the hypervisor console device <n>. This is for
747 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700749 If the device connected to the port is not a TTY but a braille
750 device, prepend "brl," before the device type, for instance
751 console=brl,ttyS0
752 For now, only VisioBraille is supported.
753
Daniel Mackf324edc2009-06-16 15:33:52 -0700754 consoleblank= [KNL] The console blank (screen saver) timeout in
755 seconds. Defaults to 10*60 = 10mins. A value of 0
756 disables the blank timer.
757
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800758 coredump_filter=
759 [KNL] Change the default value for
760 /proc/<pid>/coredump_filter.
761 See also Documentation/filesystems/proc.txt.
762
Len Brown62027ae2011-04-01 18:13:10 -0400763 cpuidle.off=1 [CPU_IDLE]
764 disable the cpuidle sub-system
765
Len Brownd68921f2015-05-11 17:27:09 -0400766 cpu_init_udelay=N
767 [X86] Delay for N microsec between assert and de-assert
768 of APIC INIT to start processors. This delay occurs
769 on every CPU online, such as boot, and resume from suspend.
770 Default: 10000
771
Linus Torvalds1da177e2005-04-16 15:20:36 -0700772 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700773 Format:
774 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700775
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800776 crashkernel=size[KMG][@offset[KMG]]
777 [KNL] Using kexec, Linux can switch to a 'crash kernel'
778 upon panic. This parameter reserves the physical
779 memory region [offset, offset + size] for that kernel
780 image. If '@offset' is omitted, then a suitable offset
781 is selected automatically. Check
782 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700783
Bernhard Wallefb391592007-10-18 23:41:02 -0700784 crashkernel=range1:size1[,range2:size2,...][@offset]
785 [KNL] Same as above, but depends on the memory
786 in the running system. The syntax of range is
787 start-[end] where start and end are both
788 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800789 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700790
Yinghai Luadbc7422013-04-15 22:23:48 -0700791 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700792 [KNL, x86_64] range could be above 4G. Allow kernel
793 to allocate physical memory region from top, so could
794 be above 4G if system have more than 4G ram installed.
795 Otherwise memory region will be allocated below 4G, if
796 available.
797 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700798 crashkernel=size[KMG],low
799 [KNL, x86_64] range under 4G. When crashkernel=X,high
800 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700801 above 4G, that cause second kernel crash on system
802 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800803 requires at least 64M+32K low memory, also enough extra
804 low memory is needed to make sure DMA buffers for 32-bit
805 devices won't run out. Kernel would try to allocate at
806 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700807 This one let user to specify own low range under 4G
808 for second kernel instead.
809 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700810 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700811 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700812
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813 cs89x0_dma= [HW,NET]
814 Format: <dma>
815
816 cs89x0_media= [HW,NET]
817 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700818
Randy Dunlapa9913042005-10-23 12:57:11 -0700819 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 See header of drivers/s390/block/dasd_devmap.c.
821
822 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
823 (one device per port)
824 Format: <port#>,<type>
825 See also Documentation/input/joystick-parport.txt
826
Thomas Renningera648ec02010-08-06 16:11:02 +0200827 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
828 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600829 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200830
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831 debug [KNL] Enable kernel debugging (events log level).
832
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700833 debug_locks_verbose=
834 [KNL] verbose self-tests
835 Format=<0|1>
836 Print debugging info while doing the locking API
837 self-tests.
838 We default to 0 (no extra messages), setting it to
839 1 will print _a lot_ more information - normally
840 only useful to kernel developers.
841
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700842 debug_objects [KNL] Enable object debugging
843
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500844 no_debug_objects
845 [KNL] Disable object debugging
846
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800847 debug_guardpage_minorder=
848 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
849 parameter allows control of the order of pages that will
850 be intentionally kept free (and hence protected) by the
851 buddy allocator. Bigger value increase the probability
852 of catching random memory corruption, but reduce the
853 amount of memory for normal system use. The maximum
854 possible value is MAX_ORDER/2. Setting this parameter
855 to 1 or 2 should be enough to identify most random
856 memory corruption problems caused by bugs in kernel or
857 driver code when a CPU writes to (or reads from) a
858 random memory location. Note that there exists a class
859 of memory corruptions problems caused by buggy H/W or
860 F/W or by drivers badly programing DMA (basically when
861 memory is written at bus level and the CPU MMU is
862 bypassed) which are not detectable by
863 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
864 tracking down these problems.
865
Joonsoo Kim031bc572014-12-12 16:55:52 -0800866 debug_pagealloc=
867 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
868 parameter enables the feature at boot time. In
869 default, it is disabled. We can avoid allocating huge
870 chunk of memory for debug pagealloc if we don't enable
871 it at boot time and the system will work mostly same
872 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
873 on: enable the feature
874
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200875 debugpat [X86] Enable PAT debugging
876
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200877 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 Format: <area>[,<node>]
879 See also Documentation/networking/decnet.txt.
880
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700881 default_hugepagesz=
882 [same as hugepagesz=] The size of the default
883 HugeTLB page size. This is the size represented by
884 the legacy /proc/ hugepages APIs, used for SHM, and
885 default size when mounting hugetlbfs filesystems.
886 Defaults to the default architecture's huge page size
887 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700888
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 dhash_entries= [KNL]
890 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700891
Brian Haleyb0f83b22010-02-04 13:36:50 -0800892 disable= [IPV6]
893 See Documentation/networking/ipv6.txt.
894
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900895 disable_cpu_apicid= [X86,APIC,SMP]
896 Format: <int>
897 The number of initial APIC ID for the
898 corresponding CPU to be disabled at boot,
899 mostly used for the kdump 2nd kernel to
900 disable BSP to wake up multiple CPUs without
901 causing system reset or hang due to sending
902 INIT from AP to BSP.
903
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000904 disable_ddw [PPC/PSERIES]
905 Disable Dynamic DMA Window support. Use this if
906 to workaround buggy firmware.
907
Brian Haleyb0f83b22010-02-04 13:36:50 -0800908 disable_ipv6= [IPV6]
909 See Documentation/networking/ipv6.txt.
910
Yinghai Lu95ffa242008-04-29 03:52:33 -0700911 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700912 The kernel tries to adjust MTRR layout from continuous
913 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700914 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700915
Yinghai Lu093af8d2008-01-30 13:33:32 +0100916 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100917 By default the kernel will trim any uncacheable
918 memory out of your available memory pool based on
919 MTRR settings. This parameter disables that behavior,
920 possibly causing your machine to run very slowly.
921
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530922 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700923 Disable PIN 1 of APIC timer
924 Can be useful to work around chipset bugs.
925
Prarit Bhargavace14c582015-08-25 13:34:53 -0400926 dis_ucode_ldr [X86] Disable the microcode loader.
927
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700928 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
929 this option disables the debugging code at boot.
930
931 dma_debug_entries=<number>
932 This option allows to tune the number of preallocated
933 entries for DMA-API debugging code. One entry is
934 required per DMA-API allocation. Use this if the
935 DMA-API debugging code disables itself because the
936 architectural default is too low.
937
Joerg Roedel1745de52009-05-22 21:49:51 +0200938 dma_debug_driver=<driver_name>
939 With this option the DMA-API debugging driver
940 filter feature can be enabled at boot time. Just
941 pass the driver to filter for as the parameter.
942 The filter can be disabled or changed to another
943 driver later using sysfs.
944
Bob Paauwe96206e22015-08-27 10:04:13 -0700945 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
946 Broken monitors, graphic adapters, KVMs and EDIDless
947 panels may send no or incorrect EDID data sets.
948 This parameter allows to specify an EDID data sets
949 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100950 Generic built-in EDID data sets are used, if one of
951 edid/1024x768.bin, edid/1280x1024.bin,
952 edid/1680x1050.bin, or edid/1920x1080.bin is given
953 and no file with the same name exists. Details and
954 instructions how to build your own EDID data are
955 available in Documentation/EDID/HOWTO.txt. An EDID
956 data set will only be used for a particular connector,
957 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700958 name. Each connector may use a unique EDID data
959 set by separating the files with a comma. An EDID
960 data set with no connector name will be used for
961 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100962
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 dscc4.setup= [NET]
964
Jim Cromie29e36c92012-04-27 14:30:41 -0600965 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
966 module.dyndbg[="val"]
967 Enable debug messages at boot time. See
968 Documentation/dynamic-debug-howto.txt for details.
969
Dave Hansen8c3641e2015-06-07 11:37:02 -0700970 nompx [X86] Disables Intel Memory Protection Extensions.
971 See Documentation/x86/intel_mpx.txt for more
972 information about the feature.
973
Borislav Petkovf29ba612015-03-27 16:15:18 +0100974 eagerfpu= [X86]
975 on enable eager fpu restore
976 off disable eager fpu restore
977 auto selects the default scheme, which automatically
978 enables eagerfpu restore for xsaveopt.
979
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700980 module.async_probe [KNL]
981 Enable asynchronous probe on this module.
982
Mark Salter56aeeba2014-04-07 15:39:53 -0700983 early_ioremap_debug [KNL]
984 Enable debug messages in early_ioremap support. This
985 is useful for tracking down temporary early mappings
986 which are not unmapped.
987
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700988 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500989
Scott Wood5664f762015-09-14 19:54:07 -0500990 When used with no options, the early console is
991 determined by the stdout-path property in device
992 tree's chosen node.
993
Michal Simek6fa62fc2014-09-10 12:43:02 +0200994 cdns,<addr>
995 Start an early, polled-mode console on a cadence serial
996 port at the specified address. The cadence serial port
997 must already be setup and configured. Options are not
998 yet supported.
999
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001000 uart[8250],io,<addr>[,options]
1001 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001002 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001003 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001004 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001005 Start an early, polled-mode console on the 8250/16550
1006 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001007 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001008 (mmio) or 32-bit (mmio32 or mmio32be).
1009 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1010 to be equivalent to 'mmio'. 'options' are specified
1011 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001012 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001013
Rob Herring0d3c6732014-04-18 17:19:57 -05001014 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001015 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001016 Start an early, polled-mode console on a pl011 serial
1017 port at the specified address. The pl011 serial port
1018 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001019 yet supported. If 'mmio32' is specified, then only
1020 the driver will use only 32-bit accessors to read/write
1021 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001022
Stephen Boyd0efe7292014-09-15 17:22:51 -07001023 msm_serial,<addr>
1024 Start an early, polled-mode console on an msm serial
1025 port at the specified address. The serial port
1026 must already be setup and configured. Options are not
1027 yet supported.
1028
1029 msm_serial_dm,<addr>
1030 Start an early, polled-mode console on an msm serial
1031 dm port at the specified address. The serial port
1032 must already be setup and configured. Options are not
1033 yet supported.
1034
Rob Herringd50d7262014-04-18 17:19:58 -05001035 smh Use ARM semihosting calls for early console.
1036
Tomasz Figab94ba032015-01-23 14:47:41 +01001037 s3c2410,<addr>
1038 s3c2412,<addr>
1039 s3c2440,<addr>
1040 s3c6400,<addr>
1041 s5pv210,<addr>
1042 exynos4210,<addr>
1043 Use early console provided by serial driver available
1044 on Samsung SoCs, requires selecting proper type and
1045 a correct base address of the selected UART port. The
1046 serial port must already be setup and configured.
1047 Options are not yet supported.
1048
Stefan Agner1d59b382015-10-17 00:45:55 -07001049 lpuart,<addr>
1050 lpuart32,<addr>
1051 Use early console provided by Freescale LP UART driver
1052 found on Freescale Vybrid and QorIQ LS1021A processors.
1053 A valid base address must be provided, and the serial
1054 port must already be setup and configured.
1055
Finn Thain7913ad12014-04-12 23:48:56 +10001056 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001058 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001059 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001061 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001062 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001063 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001064 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065
Dave Hansen147ea092013-04-10 14:03:38 -07001066 earlyprintk is useful when the kernel crashes before
1067 the normal console is initialized. It is not enabled by
1068 default because it has some cosmetic problems.
1069
Randy Dunlapa9913042005-10-23 12:57:11 -07001070 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 takes over.
1072
Matt Fleming72548e82013-10-04 09:36:56 +01001073 Only one of vga, efi, serial, or usb debug port can
1074 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001075
Dave Hansen147ea092013-04-10 14:03:38 -07001076 Currently only ttyS0 and ttyS1 may be specified by
1077 name. Other I/O ports may be explicitly specified
1078 on some architectures (x86 and arm at least) by
1079 replacing ttySn with an I/O port address, like this:
1080 earlyprintk=serial,0x1008,115200
1081 You can find the port for a given device in
1082 /proc/tty/driver/serial:
1083 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084
1085 Interaction with the standard serial driver is not
1086 very good.
1087
Matt Fleming72548e82013-10-04 09:36:56 +01001088 The VGA and EFI output is eventually overwritten by
1089 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001090
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001091 The xen output can only be used by Xen PV guests.
1092
Chen, Gongc700f012013-12-06 01:17:08 -05001093 edac_report= [HW,EDAC] Control how to report EDAC event
1094 Format: {"on" | "off" | "force"}
1095 on: enable EDAC to report H/W event. May be overridden
1096 by other higher priority error reporting module.
1097 off: disable H/W event reporting through EDAC.
1098 force: enforce the use of EDAC to report H/W event.
1099 default: on.
1100
Jason Wessel97311912010-05-20 21:04:30 -05001101 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1102 ekgdboc=kbd
1103
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001104 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001105 the boot argument: earlyprintk=vga
1106
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001108 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001110 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001111 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001112 old_map [X86-64]: switch to the old ioremap-based EFI
1113 runtime services mapping. 32-bit still uses this one by
1114 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001115 nochunk: disable reading files in "chunks" in the EFI
1116 boot stub, as chunking can cause problems with some
1117 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001118 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001119 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001120
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001121 efi_no_storage_paranoia [EFI; X86]
1122 Using this parameter you can use more than 50% of
1123 your efi variable storage. Use this parameter only if
1124 you are really sure that your UEFI does sane gc and
1125 fulfills the spec otherwise your board may brick.
1126
Taku Izumi0f96a992015-09-30 23:01:56 +09001127 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1128 Add arbitrary attribute to specific memory range by
1129 updating original EFI memory map.
1130 Region of memory which aa attribute is added to is
1131 from ss to ss+nn.
1132 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1133 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1134 attribute is added to range 0x100000000-0x180000000 and
1135 0x10a0000000-0x1120000000.
1136
1137 Using this parameter you can do debugging of EFI memmap
1138 related feature. For example, you can do debugging of
1139 Address Range Mirroring feature even if your box
1140 doesn't support it.
1141
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 eisa_irq_edge= [PARISC,HW]
1143 See header of drivers/parisc/eisa.c.
1144
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001145 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001147 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148
1149 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001150 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001151 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001152 Documentation/block/deadline-iosched.txt for details.
1153
Michael Holzheud3bf37952011-10-30 15:16:37 +01001154 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001155 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001156 image elf header and optionally the size. Generally
1157 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001158 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001160 enable_mtrr_cleanup [X86]
1161 The kernel tries to adjust MTRR layout from continuous
1162 to discrete, to make X server driver able to add WB
1163 entry later. This parameter enables that.
1164
Randy Dunlapca1eda22009-05-06 16:02:58 -07001165 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001166 Enable PIN 1 of APIC timer
1167 Can be useful to work around chipset bugs
1168 (in particular on some ATI chipsets).
1169 The kernel tries to set a reasonable default.
1170
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171 enforcing [SELINUX] Set initial enforcing status.
1172 Format: {"0" | "1"}
1173 See security/selinux/Kconfig help text.
1174 0 -- permissive (log only, no denials).
1175 1 -- enforcing (deny and log).
1176 Default value is 0.
1177 Value can be changed at runtime via /selinux/enforce.
1178
Huang Yinga08f82d2010-05-18 14:35:21 +08001179 erst_disable [ACPI]
1180 Disable Error Record Serialization Table (ERST)
1181 support.
1182
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 ether= [HW,NET] Ethernet cards parameters
1184 This option is obsoleted by the "netdev=" option, which
1185 has equivalent usage. See its documentation for details.
1186
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001187 evm= [EVM]
1188 Format: { "fix" }
1189 Permit 'security.evm' to be updated regardless of
1190 current integrity status.
1191
Akinobu Mitade1ba092006-12-08 02:39:42 -08001192 failslab=
1193 fail_page_alloc=
1194 fail_make_request=[KNL]
1195 General fault injection mechanism.
1196 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001197 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001198
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001200 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001201
Alex Chiangf13ae302008-05-08 14:03:23 -06001202 force_pal_cache_flush
1203 [IA-64] Avoid check_sal_cache_flush which may hang on
1204 buggy SAL_CACHE_FLUSH implementations. Using this
1205 parameter will force ia64_sal_cache_flush to call
1206 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1207
Chris Bainbridge69f23662014-03-07 18:40:42 +07001208 forcepae [X86-32]
1209 Forcefully enable Physical Address Extension (PAE).
1210 Many Pentium M systems disable PAE but may have a
1211 functionally usable PAE implementation.
1212 Warning: use of this parameter will taint the kernel
1213 and may cause unknown problems.
1214
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001215 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001216 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001217 as early as possible in order to facilitate early
1218 boot debugging.
1219
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001220 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001221 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001222 If no parameter is passed, ftrace will dump
1223 buffers of all CPUs, but if you pass orig_cpu, it will
1224 dump only the buffer of the CPU that triggered the
1225 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001226
1227 ftrace_filter=[function-list]
1228 [FTRACE] Limit the functions traced by the function
1229 tracer at boot up. function-list is a comma separated
1230 list of functions. This list can be changed at run
1231 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001232 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001233
1234 ftrace_notrace=[function-list]
1235 [FTRACE] Do not trace the functions specified in
1236 function-list. This list can be changed at run time
1237 by the set_ftrace_notrace file in the debugfs
1238 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001239
Stefan Assmann369bc182009-10-12 22:17:21 +02001240 ftrace_graph_filter=[function-list]
1241 [FTRACE] Limit the top level callers functions traced
1242 by the function graph tracer at boot up.
1243 function-list is a comma separated list of functions
1244 that can be changed at run time by the
1245 set_graph_function file in the debugfs tracing directory.
1246
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001247 ftrace_graph_notrace=[function-list]
1248 [FTRACE] Do not trace from the functions specified in
1249 function-list. This list is a comma separated list of
1250 functions that can be changed at run time by the
1251 set_graph_notrace file in the debugfs tracing directory.
1252
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 gamecon.map[2|3]=
1254 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1255 support via parallel port (up to 5 devices per port)
1256 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1257 See also Documentation/input/joystick-parport.txt
1258
1259 gamma= [HW,DRM]
1260
Yinghai Luaaf23042008-01-30 13:33:09 +01001261 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1262 Format: off | on
1263 default: on
1264
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001265 gcov_persist= [GCOV] When non-zero (default), profiling data for
1266 kernel modules is saved and remains accessible via
1267 debugfs, even when the module is unloaded/reloaded.
1268 When zero, profiling data is discarded and associated
1269 debugfs files are removed at module unload time.
1270
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001272 invalid Protective MBR to be treated as GPT. If the
1273 primary GPT is corrupted, it enables the backup/alternate
1274 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001276 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1277 the "Enable 0" bit of the configuration register.
1278 Format: 0 | 1
1279 Default: 0
1280 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1281 the "Enable 0" bit of the configuration register.
1282 Format: 0 | 1
1283 Default: 0
1284 grcan.select= [HW] Select which physical interface to use.
1285 Format: 0 | 1
1286 Default: 0
1287 grcan.txsize= [HW] Sets the size of the tx buffer.
1288 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1289 Default: 1024
1290 grcan.rxsize= [HW] Sets the size of the rx buffer.
1291 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1292 Default: 1024
1293
Jiri Kosina55537872015-11-05 18:44:41 -08001294 hardlockup_all_cpu_backtrace=
1295 [KNL] Should the hard-lockup detector generate
1296 backtraces on all cpus.
1297 Format: <integer>
1298
Linus Torvalds1da177e2005-04-16 15:20:36 -07001299 hashdist= [KNL,NUMA] Large hashes allocated during boot
1300 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001301 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001302 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303
1304 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1305
1306 hd= [EIDE] (E)IDE hard drive subsystem geometry
1307 Format: <cyl>,<head>,<sect>
1308
Huang Yingea8c0712010-05-18 14:35:15 +08001309 hest_disable [ACPI]
1310 Disable Hardware Error Source Table (HEST) support;
1311 corresponding firmware-first mode error processing
1312 logic will be disabled.
1313
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1315 size of <nn>. This works even on boxes that have no
1316 highmem otherwise. This also works to reduce highmem
1317 size on bigger boxes.
1318
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001319 highres= [KNL] Enable/disable high resolution timer mode.
1320 Valid parameters: "on", "off"
1321 Default: "on"
1322
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 hisax= [HW,ISDN]
1324 See Documentation/isdn/README.HiSax.
1325
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001326 hlt [BUGS=ARM,SH]
1327
1328 hpet= [X86-32,HPET] option to control HPET usage
1329 Format: { enable (default) | disable | force |
1330 verbose }
1331 disable: disable HPET and use PIT instead
1332 force: allow force enabled of undocumented chips (ICH4,
1333 VIA, nVidia)
1334 verbose: show contents of HPET registers during setup
1335
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001336 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1337 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1338
Andi Kleenb4718e62008-07-23 21:27:51 -07001339 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1340 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001341 On x86-64 and powerpc, this option can be specified
1342 multiple times interleaved with hugepages= to reserve
1343 huge pages of different sizes. Valid pages sizes on
1344 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001345 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001346
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001347 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1348 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001349 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1350 If specified, z/VM IUCV HVC accepts connections
1351 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001352
James Hoganfdabf522012-10-09 11:00:27 +01001353 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1354 hardware thread id mappings.
1355 Format: <cpu>:<hwthread>
1356
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001357 keep_bootcon [KNL]
1358 Do not unregister boot console at start. This is only
1359 useful for debugging when something happens in the window
1360 between unregistering the boot console and initializing
1361 the real console.
1362
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001363 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001364 or register an additional I2C bus that is not
1365 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001366 Format:
1367 <bus_id>,<clkrate>
1368
Jiri Kosina36d95732008-10-06 02:51:09 -04001369 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001370 i8042.unmask_kbd_data
1371 [HW] Enable printing of interrupt data from the KBD port
1372 (disabled by default, and as a pre-condition
1373 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001375 i8042.dumbkbd [HW] Pretend that controller can only read data from
1376 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377 (Don't attempt to blink the leds)
1378 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001379 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001380 i8042.noloop [HW] Disable the AUX Loopback command while probing
1381 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001383 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1385 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001386 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001387 i8042.reset [HW] Reset the controller during init and cleanup
1388 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001389 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390
1391 i810= [HW,DRM]
1392
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001393 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1394 indicates that the driver is running on unsupported
1395 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1397 does not match list of supported models.
1398 i8k.power_status
1399 [HW] Report power status in /proc/i8k
1400 (disabled by default)
1401 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1402 capability is set.
1403
Carsten Emde4dca20e2012-03-15 15:56:26 +01001404 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001405 [DRM] Invert the sense of the variable that is used to
1406 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001407 brightness value of 0 indicates backlight switched off,
1408 and the maximum of the brightness value sets the backlight
1409 to maximum brightness. If this parameter is set to 0
1410 (default) and the machine requires it, or this parameter
1411 is set to 1, a brightness value of 0 sets the backlight
1412 to maximum brightness, and the maximum of the brightness
1413 value switches the backlight off.
1414 -1 -- never invert brightness
1415 0 -- machine default
1416 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001417
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418 icn= [HW,ISDN]
1419 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1420
David Fries0af80c02009-02-25 20:28:21 +01001421 ide-core.nodma= [HW] (E)IDE subsystem
1422 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001423 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1424 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001425 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001427 ide-generic.probe-mask= [HW] (E)IDE subsystem
1428 Format: <int>
1429 Probe mask for legacy ISA IDE ports. Depending on
1430 platform up to 6 ports are supported, enabled by
1431 setting corresponding bits in the mask to 1. The
1432 default value is 0x0, which has a special meaning.
1433 On systems that have PCI, it triggers scanning the
1434 PCI bus for the first and the second port, which
1435 are then probed. On systems without PCI the value
1436 of 0x0 enables probing the two first ports as if it
1437 was 0x3.
1438
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001439 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1440 Claim all unknown PCI IDE storage controllers.
1441
Andi Kleenf039b752007-05-02 19:27:12 +02001442 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001443 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001444 Poll forces a polling idle loop that can slightly
1445 improve the performance of waking up a idle CPU, but
1446 will use a lot of power and make the system run hot.
1447 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001448 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001449 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001450 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001451
Ingo Molnar792908222006-12-06 20:40:51 -08001452 ignore_loglevel [KNL]
1453 Ignore loglevel setting - this will print /all/
1454 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001455 We also add it as printk module parameter, so users
1456 could change it dynamically, usually by
1457 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001458
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459 ihash_entries= [KNL]
1460 Set number of hash buckets for inode cache.
1461
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001462 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001463 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001464 default: "enforce"
1465
Mimi Zohar07f6a792011-03-09 22:25:48 -05001466 ima_appraise_tcb [IMA]
1467 The builtin appraise policy appraises all files
1468 owned by uid=0.
1469
Mimi Zohar3323eec2009-02-04 09:06:58 -05001470 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001471 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1472 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001473 default: "sha1"
1474
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001475 The list of supported hash algorithms is defined
1476 in crypto/hash_info.h.
1477
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001478 ima_policy= [IMA]
1479 The builtin measurement policy to load during IMA
1480 setup. Specyfing "tcb" as the value, measures all
1481 programs exec'd, files mmap'd for exec, and all files
1482 opened with the read mode bit set by either the
1483 effective uid (euid=0) or uid=0.
1484 Format: "tcb"
1485
1486 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001487 Load a policy which meets the needs of the Trusted
1488 Computing Base. This means IMA will measure all
1489 programs exec'd, files mmap'd for exec, and all files
1490 opened for read by uid=0.
1491
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001492 ima_template= [IMA]
1493 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001494 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001495 Default: "ima-ng"
1496
Roberto Sassuc2426d22014-10-13 14:08:42 +02001497 ima_template_fmt=
1498 [IMA] Define a custom template format.
1499 Format: { "field1|...|fieldN" }
1500
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001501 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1502 Format: <min_file_size>
1503 Set the minimal file size for using asynchronous hash.
1504 If left unspecified, ahash usage is disabled.
1505
1506 ahash performance varies for different data sizes on
1507 different crypto accelerators. This option can be used
1508 to achieve the best performance for a particular HW.
1509
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001510 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1511 Format: <bufsize>
1512 Set hashing buffer size. Default: 4k.
1513
1514 ahash performance varies for different chunk sizes on
1515 different crypto accelerators. This option can be used
1516 to achieve best performance for particular HW.
1517
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518 init= [KNL]
1519 Format: <full_path>
1520 Run specified binary instead of /sbin/init as init
1521 process.
1522
1523 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1524 for working out where the kernel is dying during
1525 startup.
1526
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001527 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1528 initcall functions. Useful for debugging built-in
1529 modules and initcalls.
1530
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531 initrd= [BOOT] Specify the location of the initial ramdisk
1532
1533 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1534 Format: <irq>
1535
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001536 int_pln_enable [x86] Enable power limit notification interrupt
1537
Mimi Zohard726d8d2013-03-18 14:48:02 -04001538 integrity_audit=[IMA]
1539 Format: { "0" | "1" }
1540 0 -- basic integrity auditing messages. (Default)
1541 1 -- additional integrity auditing messages.
1542
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001543 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001544 on
1545 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001546 off
1547 Disable intel iommu driver.
1548 igfx_off [Default Off]
1549 By default, gfx is mapped as normal device. If a gfx
1550 device has a dedicated DMAR unit, the DMAR unit is
1551 bypassed by not enabling DMAR with this option. In
1552 this case, gfx device will use physical address for
1553 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001554 forcedac [x86_64]
1555 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001556 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001557 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001558 than 32-bit addressing. The default is to look
1559 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001560 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001561 strict [Default Off]
1562 With this option on every unmap_single operation will
1563 result in a hardware IOTLB flush operation as opposed
1564 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001565 sp_off [Default Off]
1566 By default, super page will be supported if Intel IOMMU
1567 has the capability. With this option, super page will
1568 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001569 ecs_off [Default Off]
1570 By default, extended context tables will be supported if
1571 the hardware advertises that it has support both for the
1572 extended tables themselves, and also PASID support. With
1573 this option set, extended tables will not be used even
1574 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001575
1576 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1577 0 disables intel_idle and fall back on acpi_idle.
1578 1 to 6 specify maximum depth of C-state.
1579
Dirk Brandewie6be26492013-02-15 22:55:10 +01001580 intel_pstate= [X86]
1581 disable
1582 Do not enable intel_pstate as the default
1583 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001584 force
1585 Enable intel_pstate on systems that prohibit it by default
1586 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1587 instead of acpi-cpufreq may disable platform features, such
1588 as thermal controls and power capping, that rely on ACPI
1589 P-States information being indicated to OSPM and therefore
1590 should be used with caution. This option does not work with
1591 processors that aren't supported by the intel_pstate driver
1592 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001593 no_hwp
1594 Do not enable hardware P state control (HWP)
1595 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001596 hwp_only
1597 Only load intel_pstate on systems which support
1598 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001599
Chris Wrightd1423d52010-07-20 11:06:49 -07001600 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001601 on enable Interrupt Remapping (default)
1602 off disable Interrupt Remapping
1603 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001604 no_x2apic_optout
1605 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001606 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001607
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001608 iomem= Disable strict checking of access to MMIO memory
1609 strict regions from userspace.
1610 relaxed
1611
1612 iommu= [x86]
1613 off
1614 force
1615 noforce
1616 biomerge
1617 panic
1618 nopanic
1619 merge
1620 nomerge
1621 forcesac
1622 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001623 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001624 nobypass [PPC/POWERNV]
1625 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001626
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001627
1628 io7= [HW] IO7 for Marvel based alpha systems
1629 See comment before marvel_specify_io7 in
1630 arch/alpha/kernel/core_marvel.c.
1631
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301632 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001633 0x80
1634 Standard port 0x80 based delay
1635 0xed
1636 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001637 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001638 Simple two microseconds delay
1639 none
1640 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001641
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001643 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644
Alan Cox200803d2005-06-28 20:45:18 -07001645 irqfixup [HW]
1646 When an interrupt is not handled search all handlers
1647 for it. Intended to get systems with badly broken
1648 firmware running.
1649
1650 irqpoll [HW]
1651 When an interrupt is not handled search all handlers
1652 for it. Also check all handlers each timer
1653 interrupt. Intended to get systems with badly broken
1654 firmware running.
1655
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001657 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658
1659 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001660 Format:
1661 <cpu number>,...,<cpu number>
1662 or
Li Zefanb225d442008-11-06 12:53:39 -08001663 <cpu number>-<cpu number>
1664 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001665 or a mixture
1666 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001667
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668 This option can be used to specify one or more CPUs
1669 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001670 algorithms. You can move a process onto or off an
1671 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672 <cpu number> begins at 0 and the maximum value is
1673 "number of CPUs in system - 1".
1674
1675 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001676 alternative -- manually setting the CPU mask of all
1677 tasks in the system -- can cause problems and
1678 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679
Randy Dunlapa9913042005-10-23 12:57:11 -07001680 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001682 ivrs_ioapic [HW,X86_64]
1683 Provide an override to the IOAPIC-ID<->DEVICE-ID
1684 mapping provided in the IVRS ACPI table. For
1685 example, to map IOAPIC-ID decimal 10 to
1686 PCI device 00:14.0 write the parameter as:
1687 ivrs_ioapic[10]=00:14.0
1688
1689 ivrs_hpet [HW,X86_64]
1690 Provide an override to the HPET-ID<->DEVICE-ID
1691 mapping provided in the IVRS ACPI table. For
1692 example, to map HPET-ID decimal 0 to
1693 PCI device 00:14.0 write the parameter as:
1694 ivrs_hpet[0]=00:14.0
1695
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 js= [HW,JOY] Analog joystick
1697 See Documentation/input/joystick.txt.
1698
Kees Cook24f2e022014-06-13 13:30:36 -07001699 kaslr/nokaslr [X86]
1700 Enable/disable kernel and module base offset ASLR
1701 (Address Space Layout Randomization) if built into
1702 the kernel. When CONFIG_HIBERNATION is selected,
1703 kASLR is disabled by default. When kASLR is enabled,
1704 hibernation will be disabled.
1705
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001706 keepinitrd [HW,ARM]
1707
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301708 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001709 specifies the amount of memory usable by the kernel
1710 for non-movable allocations. The requested amount is
1711 spread evenly throughout all nodes in the system. The
1712 remaining memory in each node is used for Movable
1713 pages. In the event, a node is too small to have both
1714 kernelcore and Movable pages, kernelcore pages will
1715 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001716 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001717 allocation of pages that may be reclaimed or moved
1718 by the page migration subsystem. This means that
1719 HugeTLB pages may not be allocated from this zone.
1720 Note that allocations like PTEs-from-HighMem still
1721 use the HighMem zone if it exists, and the Normal
1722 zone if it does not.
1723
Jason Wessel4fe1da42010-05-20 21:04:31 -05001724 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1725 Format: <Controller#>[,poll interval]
1726 The controller # is the number of the ehci usb debug
1727 port as it is probed via PCI. The poll interval is
1728 optional and is the number seconds in between
1729 each poll cycle to the debug port in case you need
1730 the functionality for interrupting the kernel with
1731 gdb or control-c on the dbgp connection. When
1732 not using this parameter you use sysrq-g to break into
1733 the kernel debugger.
1734
Jason Wessel84c08fd2010-05-20 21:04:24 -05001735 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001736 Requires a tty driver that supports console polling,
1737 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001738 Serial only format: <serial_device>[,baud]
1739 keyboard only format: kbd
1740 keyboard and serial format: kbd,<serial_device>[,baud]
1741 Optional Kernel mode setting:
1742 kms, kbd format: kms,kbd
1743 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001744
Jason Wessel84c08fd2010-05-20 21:04:24 -05001745 kgdbwait [KGDB] Stop kernel execution and enter the
1746 kernel debugger at the earliest opportunity.
1747
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001748 kmac= [MIPS] korina ethernet MAC address.
1749 Configure the RouterBoard 532 series on-chip
1750 Ethernet adapter MAC address.
1751
Catalin Marinas04f70332009-06-11 13:22:39 +01001752 kmemleak= [KNL] Boot-time kmemleak enable/disable
1753 Valid arguments: on, off
1754 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001755 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1756 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001757
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001758 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1759 Valid arguments: 0, 1, 2
1760 kmemcheck=0 (disabled)
1761 kmemcheck=1 (enabled)
1762 kmemcheck=2 (one-shot mode)
1763 Default: 2 (one-shot mode)
1764
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301765 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001766 in oops dumps.
1767
Andre Przywarafef07aa2009-07-10 14:20:35 +02001768 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1769 Default is 0 (don't ignore, but inject #GP)
1770
Xiao Guangronga182d872010-09-20 22:17:48 +08001771 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1772 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001773 Default is 0 (off)
1774
Andre Przywarafef07aa2009-07-10 14:20:35 +02001775 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001776 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001777
1778 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1779 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001780 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001781
Andre Przywarafef07aa2009-07-10 14:20:35 +02001782 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1783 (virtualized MMU) support on capable Intel chips.
1784 Default is 1 (enabled)
1785
1786 kvm-intel.emulate_invalid_guest_state=
1787 [KVM,Intel] Enable emulation of invalid guest states
1788 Default is 0 (disabled)
1789
1790 kvm-intel.flexpriority=
1791 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1792 Default is 1 (enabled)
1793
Sasha Levine1a72ae2011-08-09 14:28:35 +03001794 kvm-intel.nested=
1795 [KVM,Intel] Enable VMX nesting (nVMX).
1796 Default is 0 (disabled)
1797
Andre Przywarafef07aa2009-07-10 14:20:35 +02001798 kvm-intel.unrestricted_guest=
1799 [KVM,Intel] Disable unrestricted guest feature
1800 (virtualized real and unpaged mode) on capable
1801 Intel chips. Default is 1 (enabled)
1802
1803 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1804 feature (tagged TLBs) on capable Intel chips.
1805 Default is 1 (enabled)
1806
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807 l2cr= [PPC]
1808
Robert Brosea78bfbf2008-03-29 07:20:23 +11001809 l3cr= [PPC]
1810
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001811 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001812 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001813
Suresh Siddha279f1462012-10-22 14:37:58 -07001814 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1815 value for LAPIC timer one-shot implementation. Default
1816 back to the programmable timer unit in the LAPIC.
1817
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301818 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001819 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001820
FD Camifcb71f62008-01-06 19:08:56 +01001821 libata.dma= [LIBATA] DMA control
1822 libata.dma=0 Disable all PATA and SATA DMA
1823 libata.dma=1 PATA and SATA Disk DMA only
1824 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001825 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001826 Combinations also work, so libata.dma=3 enables DMA
1827 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001828
Michael Prokop20308872009-08-06 00:14:10 +02001829 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1830 libata.ignore_hpa=0 keep BIOS limits (default)
1831 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001832
Dave Jones78e70c22007-09-27 11:50:13 -04001833 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1834 when set.
1835 Format: <int>
1836
Tejun Heo33267322008-02-13 09:15:09 +09001837 libata.force= [LIBATA] Force configurations. The format is comma
1838 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001839 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001840 matching port, link or device. Basically, it matches
1841 the ATA ID string printed on console by libata. If
1842 the whole ID part is omitted, the last PORT and DEVICE
1843 values are used. If ID hasn't been specified yet, the
1844 configuration applies to all ports, links and devices.
1845
1846 If only DEVICE is omitted, the parameter applies to
1847 the port and all links and devices behind it. DEVICE
1848 number of 0 either selects the first device or the
1849 first fan-out link behind PMP device. It does not
1850 select the host link. DEVICE number of 15 selects the
1851 host link and device attached to it.
1852
1853 The VAL specifies the configuration to force. As long
1854 as there's no ambiguity shortcut notation is allowed.
1855 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1856 The following configurations can be forced.
1857
1858 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1859 Any ID with matching PORT is used.
1860
1861 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1862
1863 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1864 udma[/][16,25,33,44,66,100,133] notation is also
1865 allowed.
1866
1867 * [no]ncq: Turn on or off NCQ.
1868
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001869 * [no]ncqtrim: Turn off queued DSM TRIM.
1870
Tejun Heo05944bd2008-08-13 20:19:09 +09001871 * nohrst, nosrst, norst: suppress hard, soft
1872 and both resets.
1873
Dan Williamsca6d43b2012-06-21 23:41:41 -07001874 * rstonce: only attempt one reset during
1875 hot-unplug link recovery
1876
Tejun Heo43c9c592010-05-23 12:59:11 +02001877 * dump_id: dump IDENTIFY data.
1878
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001879 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1880
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001881 * disable: Disable this device.
1882
Tejun Heo33267322008-02-13 09:15:09 +09001883 If there are multiple matching configurations changing
1884 the same attribute, the last one is used.
1885
Yinghai Lu95f72d12010-07-12 14:36:09 +10001886 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001887
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001889 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001891 lockd.nlm_grace_period=P [NFS] Assign grace period.
1892 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001894 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1895 Format: <integer>
1896
1897 lockd.nlm_timeout=T [NFS] Assign timeout value.
1898 Format: <integer>
1899
1900 lockd.nlm_udpport=M [NFS] Assign UDP port.
1901 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001902
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001903 locktorture.nreaders_stress= [KNL]
1904 Set the number of locking read-acquisition kthreads.
1905 Defaults to being automatically set based on the
1906 number of online CPUs.
1907
1908 locktorture.nwriters_stress= [KNL]
1909 Set the number of locking write-acquisition kthreads.
1910
1911 locktorture.onoff_holdoff= [KNL]
1912 Set time (s) after boot for CPU-hotplug testing.
1913
1914 locktorture.onoff_interval= [KNL]
1915 Set time (s) between CPU-hotplug operations, or
1916 zero to disable CPU-hotplug testing.
1917
1918 locktorture.shuffle_interval= [KNL]
1919 Set task-shuffle interval (jiffies). Shuffling
1920 tasks allows some CPUs to go into dyntick-idle
1921 mode during the locktorture test.
1922
1923 locktorture.shutdown_secs= [KNL]
1924 Set time (s) after boot system shutdown. This
1925 is useful for hands-off automated testing.
1926
1927 locktorture.stat_interval= [KNL]
1928 Time (s) between statistics printk()s.
1929
1930 locktorture.stutter= [KNL]
1931 Time (s) to stutter testing, for example,
1932 specifying five seconds causes the test to run for
1933 five seconds, wait for five seconds, and so on.
1934 This tests the locking primitive's ability to
1935 transition abruptly to and from idle.
1936
1937 locktorture.torture_runnable= [BOOT]
1938 Start locktorture running at boot time.
1939
1940 locktorture.torture_type= [KNL]
1941 Specify the locking implementation to test.
1942
1943 locktorture.verbose= [KNL]
1944 Enable additional printk() statements.
1945
Linus Torvalds1da177e2005-04-16 15:20:36 -07001946 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1947 Format: <irq>
1948
1949 loglevel= All Kernel Messages with a loglevel smaller than the
1950 console loglevel will be printed to the console. It can
1951 also be changed with klogd or other programs. The
1952 loglevels are defined as follows:
1953
1954 0 (KERN_EMERG) system is unusable
1955 1 (KERN_ALERT) action must be taken immediately
1956 2 (KERN_CRIT) critical conditions
1957 3 (KERN_ERR) error conditions
1958 4 (KERN_WARNING) warning conditions
1959 5 (KERN_NOTICE) normal but significant condition
1960 6 (KERN_INFO) informational
1961 7 (KERN_DEBUG) debug-level messages
1962
Randy Dunlapc756d082011-02-20 20:08:35 -08001963 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001964 in bytes. n must be a power of two and greater
1965 than the minimal size. The minimal size is defined
1966 by LOG_BUF_SHIFT kernel config parameter. There is
1967 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1968 that allows to increase the default size depending on
1969 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001970
Randy Dunlapaccaa242007-10-16 01:29:37 -07001971 logo.nologo [FB] Disables display of the built-in Linux logo.
1972 This may be used to provide more screen space for
1973 kernel log messages and is useful when debugging
1974 kernel boot problems.
1975
Linus Torvalds1da177e2005-04-16 15:20:36 -07001976 lp=0 [LP] Specify parallel ports to use, e.g,
1977 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1978 lp=reset first parallel port). 'lp=0' disables the
1979 lp=auto printer driver. 'lp=reset' (which can be
1980 specified in addition to the ports) causes
1981 attached printers to be reset. Using
1982 lp=port1,port2,... specifies the parallel ports
1983 to associate lp devices with, starting with
1984 lp0. A port specification may be 'none' to skip
1985 that lp device, or a parport name such as
1986 'parport0'. Specifying 'lp=auto' instead of a
1987 port specification list means that device IDs
1988 from each port should be examined, to see if
1989 an IEEE 1284-compliant printer is attached; if
1990 so, the driver will manage that printer.
1991 See also header of drivers/char/lp.c.
1992
1993 lpj=n [KNL]
1994 Sets loops_per_jiffy to given constant, thus avoiding
1995 time-consuming boot-time autodetection (up to 250 ms per
1996 CPU). 0 enables autodetection (default). To determine
1997 the correct value for your kernel, boot with normal
1998 autodetection and see what value is printed. Note that
1999 on SMP systems the preset will be applied to all CPUs,
2000 which is likely to cause problems if your CPUs need
2001 significantly divergent settings. An incorrect value
2002 will cause delays in the kernel to be wrong, leading to
2003 unpredictable I/O errors and other breakage. Although
2004 unlikely, in the extreme case this might damage your
2005 hardware.
2006
2007 ltpc= [NET]
2008 Format: <io>,<irq>,<dma>
2009
Randy Dunlap16290242011-08-13 12:34:52 -07002010 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002011 (machvec) in a generic kernel.
2012 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002013
Wu Zhangjin3209e702009-07-02 23:27:12 +08002014 machtype= [Loongson] Share the same kernel image file between different
2015 yeeloong laptop.
2016 Example: machtype=lemote-yeeloong-2f-7inch
2017
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002018 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2019 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002020
2021 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04002022 should make use of. maxcpus=n : n >= 0 limits the
2023 kernel to using 'n' processors. n=0 is a special case,
2024 it is equivalent to "nosmp", which also disables
2025 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026
Kay Sieversd134b002011-07-31 22:08:04 +02002027 max_loop= [LOOP] The number of loop block devices that get
2028 (loop.max_loop) unconditionally pre-created at init time. The default
2029 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2030 of statically allocating a predefined number, loop
2031 devices can be requested on-demand with the
2032 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002033
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002034 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035
Uwe Hermann71cced62008-10-20 09:32:21 -07002036 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002037
Linus Torvalds1da177e2005-04-16 15:20:36 -07002038 md= [HW] RAID subsystems devices and level
2039 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002040
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 mdacon= [MDA]
2042 Format: <first>,<last>
2043 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002044
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2046 Amount of memory to be used when the kernel is not able
2047 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002048 [X86] Work as limiting max address. Use together
2049 with memmap= to avoid physical address space collisions.
2050 Without memmap= PCI devices could be placed at addresses
2051 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002053 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002054 memory.
2055
Paul Mundt6902aa82008-09-21 17:14:42 +09002056 memchunk=nn[KMG]
2057 [KNL,SH] Allow user to override the default size for
2058 per-device physically contiguous DMA buffers.
2059
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302060 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061 E820 memory map, as specified by the user.
2062 Such memmap=exactmap lines can be constructed based on
2063 BIOS output or other requirements. See the memmap=nn@ss
2064 option description.
2065
2066 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002067 [KNL] Force usage of a specific region of memory.
2068 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002069
2070 memmap=nn[KMG]#ss[KMG]
2071 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002072 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002073
2074 memmap=nn[KMG]$ss[KMG]
2075 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002076 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002077 Example: Exclude memory from 0x18690000-0x1869ffff
2078 memmap=64K$0x18690000
2079 or
2080 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002082 memmap=nn[KMG]!ss[KMG]
2083 [KNL,X86] Mark specific memory as protected.
2084 Region of memory to be used, from ss to ss+nn.
2085 The memory region may be marked as e820 type 12 (0xc)
2086 and is NVDIMM or ADR memory.
2087
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002088 memory_corruption_check=0/1 [X86]
2089 Some BIOSes seem to corrupt the first 64k of
2090 memory when doing things like suspend/resume.
2091 Setting this option will scan the memory
2092 looking for corruption. Enabling this will
2093 both detect corruption and prevent the kernel
2094 from using the memory being corrupted.
2095 However, its intended as a diagnostic tool; if
2096 repeatable BIOS-originated corruption always
2097 affects the same memory, you can use memmap=
2098 to prevent the kernel from using that memory.
2099
2100 memory_corruption_check_size=size [X86]
2101 By default it checks for corruption in the low
2102 64k, making this memory unavailable for normal
2103 use. Use this parameter to scan for
2104 corruption in more or less memory.
2105
2106 memory_corruption_check_period=seconds [X86]
2107 By default it checks for corruption every 60
2108 seconds. Use this parameter to check at some
2109 other rate. 0 disables periodic checking.
2110
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002111 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002112 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002113 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002114 Specifies the number of memtest passes to be
2115 performed. Each pass selects another test
2116 pattern from a given set of patterns. Memtest
2117 fills the memory with this pattern, validates
2118 memory contents and reserves bad memory
2119 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002120
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 meye.*= [HW] Set MotionEye Camera parameters
2122 See Documentation/video4linux/meye.txt.
2123
Andres Salomon8f368812007-10-12 23:04:06 +02002124 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2125 Multi-Function General Purpose Timers on AMD Geode
2126 platforms.
2127
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002128 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2129 the BIOS has incorrectly applied a workaround. TinyBIOS
2130 version 0.98 is known to be affected, 0.99 fixes the
2131 problem by letting the user disable the workaround.
2132
Linus Torvalds1da177e2005-04-16 15:20:36 -07002133 mga= [HW,DRM]
2134
Randy Dunlap1c207f952008-11-19 15:36:16 -08002135 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2136 physical address is ignored.
2137
Michel Pollet39f45d72009-05-20 11:10:31 +01002138 mini2440= [ARM,HW,KNL]
2139 Format:[0..2][b][c][t]
2140 Default: "0tb"
2141 MINI2440 configuration specification:
2142 0 - The attached screen is the 3.5" TFT
2143 1 - The attached screen is the 7" TFT
2144 2 - The VGA Shield is attached (1024x768)
2145 Leaving out the screen size parameter will not load
2146 the TFT driver, and the framebuffer will be left
2147 unconfigured.
2148 b - Enable backlight. The TFT backlight pin will be
2149 linked to the kernel VESA blanking code and a GPIO
2150 LED. This parameter is not necessary when using the
2151 VGA shield.
2152 c - Enable the s3c camera interface.
2153 t - Reserved for enabling touchscreen support. The
2154 touchscreen support is not enabled in the mainstream
2155 kernel as of 2.6.30, a preliminary port can be found
2156 in the "bleeding edge" mini2440 support kernel at
2157 http://repo.or.cz/w/linux-2.6/mini2440.git
2158
Mel Gorman6b74ab92008-07-23 21:26:49 -07002159 mminit_loglevel=
2160 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2161 parameter allows control of the logging verbosity for
2162 the additional memory initialisation checks. A value
2163 of 0 disables mminit logging and a level of 4 will
2164 log everything. Information is printed at KERN_DEBUG
2165 so loglevel=8 may also need to be specified.
2166
Rusty Russell106a4ee2012-09-26 10:09:40 +01002167 module.sig_enforce
2168 [KNL] When CONFIG_MODULE_SIG is set, this means that
2169 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002170 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002171 is always true, so this option does nothing.
2172
Linus Torvalds1da177e2005-04-16 15:20:36 -07002173 mousedev.tap_time=
2174 [MOUSE] Maximum time between finger touching and
2175 leaving touchpad surface for touch to be considered
2176 a tap and be reported as a left button click (for
2177 touchpads working in absolute mode only).
2178 Format: <msecs>
2179 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2180 reporting absolute coordinates, such as tablets
2181 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2182 reporting absolute coordinates, such as tablets
2183
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302184 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002185 is similar to kernelcore except it specifies the
2186 amount of memory used for migratable allocations.
2187 If both kernelcore and movablecore is specified,
2188 then kernelcore will be at *least* the specified
2189 value but may be more. If movablecore on its own
2190 is specified, the administrator must be careful
2191 that the amount of memory usable for all allocations
2192 is not too small.
2193
Tang Chenc5320922013-11-12 15:08:10 -08002194 movable_node [KNL,X86] Boot-time switch to enable the effects
2195 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2196
Linus Torvalds1da177e2005-04-16 15:20:36 -07002197 MTD_Partition= [MTD]
2198 Format: <name>,<region-number>,<size>,<offset>
2199
Randy Dunlapa9913042005-10-23 12:57:11 -07002200 MTD_Region= [MTD] Format:
2201 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202
2203 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002204 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002206 multitce=off [PPC] This parameter disables the use of the pSeries
2207 firmware feature for updating multiple TCE entries
2208 at a time.
2209
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002210 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2211
2212 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2213
2214 boundary - index of last SLC block on Flex-OneNAND.
2215 The remaining blocks are configured as MLC blocks.
2216 lock - Configure if Flex-OneNAND boundary should be locked.
2217 Once locked, the boundary cannot be changed.
2218 1 indicates lock status, 0 indicates unlock status.
2219
Ben Dooks9db829f2008-07-03 11:24:29 +01002220 mtdset= [ARM]
2221 ARM/S3C2412 JIVE boot control
2222
2223 See arch/arm/mach-s3c2412/mach-jive.c
2224
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002226 [HW] Make the MicroTouch USB driver use raw coordinates
2227 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002228
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002229 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002230 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002231 that could hold holes aka. UC entries.
2232
2233 mtrr_gran_size=nn[KMG] [X86]
2234 Used for mtrr cleanup. It is granularity of mtrr block.
2235 Default is 1.
2236 Large value could prevent small alignment from
2237 using up MTRRs.
2238
2239 mtrr_spare_reg_nr=n [X86]
2240 Format: <integer>
2241 Range: 0,7 : spare reg number
2242 Default : 1
2243 Used for mtrr cleanup. It is spare mtrr entries number.
2244 Set to 2 or more if your graphical card needs more.
2245
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2247
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248 netdev= [NET] Network devices parameters
2249 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2250 Note that mem_start is often overloaded to mean
2251 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002252 This usage is only documented in each driver source
2253 file if at all.
2254
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002255 nf_conntrack.acct=
2256 [NETFILTER] Enable connection tracking flow accounting
2257 0 to disable accounting
2258 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002259 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002260
Chuck Lever306a0752010-09-17 10:54:37 -04002261 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002262 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263
2264 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002265 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002266
Chuck Lever306a0752010-09-17 10:54:37 -04002267 nfsrootdebug [NFS] enable nfsroot debugging messages.
2268 See Documentation/filesystems/nfs/nfsroot.txt.
2269
Trond Myklebusta72b4422006-01-03 09:55:41 +01002270 nfs.callback_tcpport=
2271 [NFS] set the TCP port on which the NFSv4 callback
2272 channel should listen.
2273
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002274 nfs.cache_getent=
2275 [NFS] sets the pathname to the program which is used
2276 to update the NFS client cache entries.
2277
2278 nfs.cache_getent_timeout=
2279 [NFS] sets the timeout after which an attempt to
2280 update a cache entry is deemed to have failed.
2281
Trond Myklebust58df0952006-01-03 09:55:57 +01002282 nfs.idmap_cache_timeout=
2283 [NFS] set the maximum lifetime for idmapper cache
2284 entries.
2285
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002286 nfs.enable_ino64=
2287 [NFS] enable 64-bit inode numbers.
2288 If zero, the NFS client will fake up a 32-bit inode
2289 number for the readdir() and stat() syscalls instead
2290 of returning the full 64-bit number.
2291 The default is to return 64-bit inode numbers.
2292
Trond Myklebustef159e92012-02-06 19:50:40 -05002293 nfs.max_session_slots=
2294 [NFSv4.1] Sets the maximum number of session slots
2295 the client will attempt to negotiate with the server.
2296 This limits the number of simultaneous RPC requests
2297 that the client can send to the NFSv4.1 server.
2298 Note that there is little point in setting this
2299 value higher than the max_tcp_slot_table_limit.
2300
Trond Myklebustb064eca22011-02-22 15:44:32 -08002301 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002302 [NFSv4] When set to the default of '1', this option
2303 ensures that both the RPC level authentication
2304 scheme and the NFS level operations agree to use
2305 numeric uids/gids if the mount is using the
2306 'sec=sys' security flavour. In effect it is
2307 disabling idmapping, which can make migration from
2308 legacy NFSv2/v3 systems to NFSv4 easier.
2309 Servers that do not support this mode of operation
2310 will be autodetected by the client, and it will fall
2311 back to using the idmapper.
2312 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002313 nfs.nfs4_unique_id=
2314 [NFS4] Specify an additional fixed unique ident-
2315 ification string that NFSv4 clients can insert into
2316 their nfs_client_id4 string. This is typically a
2317 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002318
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002319 nfs.send_implementation_id =
2320 [NFSv4.1] Send client implementation identification
2321 information in exchange_id requests.
2322 If zero, no implementation identification information
2323 will be sent.
2324 The default is to send the implementation identification
2325 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002326
2327 nfs.recover_lost_locks =
2328 [NFSv4] Attempt to recover locks that were lost due
2329 to a lease timeout on the server. Please note that
2330 doing this risks data corruption, since there are
2331 no guarantees that the file will remain unchanged
2332 after the locks are lost.
2333 If you want to enable the kernel legacy behaviour of
2334 attempting to recover these locks, then set this
2335 parameter to '1'.
2336 The default parameter value of '0' causes the kernel
2337 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002338
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002339 nfs4.layoutstats_timer =
2340 [NFSv4.2] Change the rate at which the kernel sends
2341 layoutstats to the pNFS metadata server.
2342
2343 Setting this to value to 0 causes the kernel to use
2344 whatever value is the default set by the layout
2345 driver. A non-zero value sets the minimum interval
2346 in seconds between layoutstats transmissions.
2347
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002348 nfsd.nfs4_disable_idmapping=
2349 [NFSv4] When set to the default of '1', the NFSv4
2350 server will return only numeric uids and gids to
2351 clients using auth_sys, and will accept numeric uids
2352 and gids from such clients. This is intended to ease
2353 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002354
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002355 objlayoutdriver.osd_login_prog=
2356 [NFS] [OBJLAYOUT] sets the pathname to the program which
2357 is used to automatically discover and login into new
2358 osd-targets. Please see:
2359 Documentation/filesystems/pnfs.txt for more explanations
2360
Paul Mundt1e1030d2009-09-01 17:38:32 +09002361 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002362 when a NMI is triggered.
2363 Format: [state][,regs][,debounce][,die]
2364
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302365 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002366 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002367 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002368 0 - turn hardlockup detector in nmi_watchdog off
2369 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002370 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002371 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002372 default). To disable both hard and soft lockup detectors,
2373 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002374 This is useful when you use a panic=... timeout and
2375 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002376
Anton Vorontsovbff38772009-07-08 11:10:56 -07002377 netpoll.carrier_timeout=
2378 [NET] Specifies amount of time (in seconds) that
2379 netpoll should wait for a carrier. By default netpoll
2380 waits 4 seconds.
2381
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002382 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383 emulation library even if a 387 maths coprocessor
2384 is present.
2385
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002386 no_console_suspend
2387 [HW] Never suspend the console
2388 Disable suspending of consoles during suspend and
2389 hibernate operations. Once disabled, debugging
2390 messages can reach various consoles while the rest
2391 of the system is being put to sleep (ie, while
2392 debugging driver suspend/resume hooks). This may
2393 not work reliably with all consoles, but is known
2394 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002395 To facilitate more flexible debugging, we also add
2396 console_suspend, a printk module parameter to control
2397 it. Users could use console_suspend (usually
2398 /sys/module/printk/parameters/console_suspend) to
2399 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002400
Christoph Lameterc1aee212007-05-31 00:40:47 -07002401 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2402 caches in the slab allocator. Saves per-node memory,
2403 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002404
Randy Dunlapa9913042005-10-23 12:57:11 -07002405 noalign [KNL,ARM]
2406
Linus Torvalds1da177e2005-04-16 15:20:36 -07002407 noapic [SMP,APIC] Tells the kernel to not make use of any
2408 IOAPICs that may be present in the system.
2409
Mike Galbraith5091faa2010-11-30 14:18:03 +01002410 noautogroup Disable scheduler automatic task group creation.
2411
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412 nobats [PPC] Do not use BATs for mapping kernel lowmem
2413 on "Classic" PPC cores.
2414
2415 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002416
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002417 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2418
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002419 nodelayacct [KNL] Disable per-task delay accounting
2420
Linus Torvalds1da177e2005-04-16 15:20:36 -07002421 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2422
Paul Mundt6902aa82008-09-21 17:14:42 +09002423 nodsp [SH] Disable hardware DSP at boot time.
2424
Dave Youngb2e0a542014-08-14 17:15:26 +08002425 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002426
Linus Torvalds1da177e2005-04-16 15:20:36 -07002427 noexec [IA-64]
2428
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302429 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002430 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002432 noexec=off: disable non-executable mappings
2433
H. Peter Anvin52b61792012-09-21 12:43:13 -07002434 nosmap [X86]
2435 Disable SMAP (Supervisor Mode Access Prevention)
2436 even if it is supported by processor.
2437
Fenghua Yude5397a2011-05-11 16:51:05 -07002438 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002439 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002440 even if it is supported by processor.
2441
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002442 noexec32 [X86-64]
2443 This affects only 32-bit executables.
2444 noexec32=on: enable non-executable mappings (default)
2445 read doesn't imply executable mappings
2446 noexec32=off: disable non-executable mappings
2447 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002448
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002449 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002450
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002451 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002452 register save and restore. The kernel will only save
2453 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002455 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2456
Suresh Siddha0c752a92009-05-22 12:17:45 -07002457 noxsave [BUGS=X86] Disables x86 extended register state save
2458 and restore using xsave. The kernel will fallback to
2459 enabling legacy floating-point and sse state.
2460
Fenghua Yub6f42a42014-05-29 11:12:31 -07002461 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2462 register states. The kernel will fall back to use
2463 xsave to save the states. By using this parameter,
2464 performance of saving the states is degraded because
2465 xsave doesn't support modified optimization while
2466 xsaveopt supports it on xsaveopt enabled systems.
2467
2468 noxsaves [X86] Disables xsaves and xrstors used in saving and
2469 restoring x86 extended register state in compacted
2470 form of xsave area. The kernel will fall back to use
2471 xsaveopt and xrstor to save and restore the states
2472 in standard form of xsave area. By using this
2473 parameter, xsave area per process might occupy more
2474 memory on xsaves enabled systems.
2475
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002476 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2477 wfi(ARM) instruction doesn't work correctly and not to
2478 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002479
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002480 no_file_caps Tells the kernel not to honor file capabilities. The
2481 only way then for a file to be executed with privilege
2482 is to be setuid root or executed by root.
2483
Linus Torvalds1da177e2005-04-16 15:20:36 -07002484 nohalt [IA-64] Tells the kernel not to use the power saving
2485 function PAL_HALT_LIGHT when idle. This increases
2486 power-consumption. On the positive side, it reduces
2487 interrupt wake-up latency, which may improve performance
2488 in certain environments such as networked servers or
2489 real-time systems.
2490
Kees Cooka6e15a32014-06-13 13:30:35 -07002491 nohibernate [HIBERNATION] Disable hibernation and resume.
2492
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002493 nohz= [KNL] Boottime enable/disable dynamic ticks
2494 Valid arguments: on, off
2495 Default: on
2496
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002497 nohz_full= [KNL,BOOT]
2498 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002499 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002500 whenever possible. The boot CPU will be forced outside
2501 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002502 The CPUs in this range must also be included in the
2503 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002504
Paul Mundteeee7852009-04-02 12:31:16 +09002505 noiotrap [SH] Disables trapped I/O port accesses.
2506
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002507 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508 disable unhandled interrupt sources.
2509
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302510 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002511 broken timer IRQ sources.
2512
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513 noisapnp [ISAPNP] Disables ISA PnP code.
2514
2515 noinitrd [RAM] Tells the kernel not to load any configured
2516 initial RAM disk.
2517
Weidong Han03ea8152009-04-17 16:42:15 +08002518 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2519 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002520 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002521
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522 nointroute [IA-64]
2523
Randy Dunlap16290242011-08-13 12:34:52 -07002524 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002525
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002526 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2527
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002528 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2529 fault handling.
2530
Glauber Costad910f5c2011-07-11 15:28:19 -04002531 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2532 steal time is computed, but won't influence scheduler
2533 behaviour
2534
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002535 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002536
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002537 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002538
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539 noltlbs [PPC] Do not use large page/tlb entries for kernel
2540 lowmem mapping on PPC40x.
2541
Horms312f1f02006-02-22 09:57:55 +09002542 nomca [IA-64] Disable machine check abort handling
2543
Masanari Iida13696e02015-05-16 02:16:43 +09002544 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002545
Andres Salomon83d73842007-10-12 23:04:06 +02002546 nomfgpt [X86-32] Disable Multi-Function General Purpose
2547 Timer usage (for AMD Geode machines).
2548
Don Zickusbda62632011-10-13 15:14:27 -04002549 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2550 shutdown the other cpus. Instead use the REBOOT_VECTOR
2551 irq.
2552
Dave Young02608be2012-02-01 10:33:14 +08002553 nomodule Disable module load
2554
Jiri Kosina016ddd92010-01-18 17:05:40 +01002555 nopat [X86] Disable PAT (page attribute table extension of
2556 pagetables) support.
2557
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002558 norandmaps Don't use address space randomization. Equivalent to
2559 echo 0 > /proc/sys/kernel/randomize_va_space
2560
Jiri Kosinabbff2162010-08-11 18:34:09 +02002561 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002562
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002563 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002564 with UP alternatives
2565
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002566 nordrand [X86] Disable kernel use of the RDRAND and
2567 RDSEED instructions even if they are supported
2568 by the processor. RDRAND and RDSEED are still
2569 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002570
Randy Dunlapa9913042005-10-23 12:57:11 -07002571 noresume [SWSUSP] Disables resume and restores original swap
2572 space.
2573
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 no-scroll [VGA] Disables scrollback.
2575 This is required for the Braillex ib80-piezo Braille
2576 reader made by F.H. Papenmeier (Germany).
2577
2578 nosbagart [IA-64]
2579
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002580 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002581
Len Brown61ec7562007-08-16 03:34:22 -04002582 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2583 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002584
Dave Jones97842212007-07-15 23:41:05 -07002585 nosoftlockup [KNL] Disable the soft-lockup detector.
2586
Linus Torvalds1da177e2005-04-16 15:20:36 -07002587 nosync [HW,M68K] Disables sync negotiation for all devices.
2588
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002589 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002591 nowatchdog [KNL] Disable both lockup detectors, i.e.
2592 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002593
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002595
Weidong Han2b2fd872009-04-17 16:42:12 +08002596 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2597
Fenghua Yuf78cff42012-11-13 11:32:38 -08002598 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2599 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2600 Some features depend on CPU0. Known dependencies are:
2601 1. Resume from suspend/hibernate depends on CPU0.
2602 Suspend/hibernate will fail if CPU0 is offline and you
2603 need to online CPU0 before suspend/hibernate.
2604 2. PIC interrupts also depend on CPU0. CPU0 can't be
2605 removed if a PIC interrupt is detected.
2606 It's said poweroff/reboot may depend on CPU0 on some
2607 machines although I haven't seen such issues so far
2608 after CPU0 is offline on a few tested machines.
2609 If the dependencies are under your control, you can
2610 turn on cpu0_hotplug.
2611
Randy Dunlap16290242011-08-13 12:34:52 -07002612 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002613 purges which is reported from either PAL_VM_SUMMARY or
2614 SAL PALO.
2615
Yinghai Lu2b633e32010-02-10 01:20:37 -08002616 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2617 could support. nr_cpus=n : n >= 1 limits the kernel to
2618 supporting 'n' processors. Later in runtime you can not
2619 use hotplug cpu feature to put more cpu back to online.
2620 just like you compile the kernel NR_CPUS=n
2621
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002622 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2623
Mel Gorman1a687c22012-11-22 11:16:36 +00002624 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2625 Allowed values are enable and disable
2626
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002627 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2628 one of ['zone', 'node', 'default'] can be specified
2629 This can be set from sysctl after boot.
2630 See Documentation/sysctl/vm.txt for details.
2631
Randy Dunlap7c4be252009-01-06 14:42:44 -08002632 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2633 See Documentation/debugging-via-ohci1394.txt for more
2634 info.
2635
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002636 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2637 Rather than timing out after 20 ms if an EC
2638 command is not properly ACKed, override the length
2639 of the timeout. We have interrupts disabled while
2640 waiting for the ACK, so if this is set too high
2641 interrupts *may* be lost!
2642
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002643 omap_mux= [OMAP] Override bootloader pin multiplexing.
2644 Format: <mux_mode0.mode_name=value>...
2645 For example, to override I2C bus2:
2646 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2647
Linus Torvalds1da177e2005-04-16 15:20:36 -07002648 oprofile.timer= [HW]
2649 Use timer interrupt instead of performance counters
2650
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002651 oprofile.cpu_type= Force an oprofile cpu type
2652 This might be useful if you have an older oprofile
2653 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002654 Format: { arch_perfmon }
2655 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002656 perfmon on Intel CPUs instead of the
2657 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002658 timer: [X86] Force use of architectural NMI
2659 timer mode (see also oprofile.timer
2660 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002661 [s390] Force legacy basic mode sampling
2662 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002663
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002664 oops=panic Always panic on oopses. Default is to just kill the
2665 process, but there is a small probability of
2666 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002667 This will also cause panics on machine check exceptions.
2668 Useful together with panic=30 to trigger a reboot.
2669
Randy Dunlapbcfde332010-06-07 17:10:38 -07002670 OSS [HW,OSS]
2671 See Documentation/sound/oss/oss-parameters.txt
2672
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002673 page_owner= [KNL] Boot-time page_owner enabling option.
2674 Storage of the information about who allocated
2675 each page is disabled in default. With this switch,
2676 we can turn it on.
2677 on: enable the feature
2678
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002679 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002680 timeout > 0: seconds before rebooting
2681 timeout = 0: wait forever
2682 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002683 Format: <timeout>
2684
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002685 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2686 on a WARN().
2687
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002688 crash_kexec_post_notifiers
2689 Run kdump after running panic-notifiers and dumping
2690 kmsg. This only for the users who doubt kdump always
2691 succeeds in any situation.
2692 Note that this also increases risks of kdump failure,
2693 because some panic notifiers can make the crashed
2694 kernel more unstable.
2695
Linus Torvalds1da177e2005-04-16 15:20:36 -07002696 parkbd.port= [HW] Parallel port number the keyboard adapter is
2697 connected to, default is 0.
2698 Format: <parport#>
2699 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2700 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002701 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002702
Randy Dunlapa9913042005-10-23 12:57:11 -07002703 parport= [HW,PPT] Specify parallel ports. 0 disables.
2704 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2705 Use 'auto' to force the driver to use any
2706 IRQ/DMA settings detected (the default is to
2707 ignore detected IRQ/DMA settings because of
2708 possible conflicts). You can specify the base
2709 address, IRQ, and DMA settings; IRQ and DMA
2710 should be numbers, or 'auto' (for using detected
2711 settings on that particular port), or 'nofifo'
2712 (to avoid using a FIFO even if it is detected).
2713 Parallel ports are assigned in the order they
2714 are specified on the command line, starting
2715 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716
Randy Dunlapa9913042005-10-23 12:57:11 -07002717 parport_init_mode= [HW,PPT]
2718 Configure VIA parallel port to operate in
2719 a specific mode. This is necessary on Pegasos
2720 computer where firmware has no options for setting
2721 up parallel port mode and sets it to spp.
2722 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002723 Format: [spp|ps2|epp|ecp|ecpepp]
2724
Andrew Mortondd287792006-03-23 03:00:57 -08002725 pause_on_oops=
2726 Halt all CPUs after the first oops has been printed for
2727 the specified number of seconds. This is to be used if
2728 your oopses keep scrolling off the screen.
2729
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730 pcbit= [HW,ISDN]
2731
2732 pcd. [PARIDE]
2733 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002734 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002735
Randy Dunlapa9913042005-10-23 12:57:11 -07002736 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002737 earlydump [X86] dump PCI config space before the kernel
2738 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002739 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002740 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002741 the hardware directly. Use this if your machine
2742 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002743 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002744 hardware access methods are allowed. Use this
2745 if you experience crashes upon bootup and you
2746 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002747 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002748 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002749 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002750 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002751 noaer [PCIE] If the PCIEAER kernel config parameter is
2752 enabled, this kernel boot option can be used to
2753 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002754 nodomains [PCI] Disable support for multiple PCI
2755 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302756 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002757 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002758 check_enable_amd_mmconf [X86] check for and enable
2759 properly configured MMIO access to PCI
2760 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002761 nomsi [MSI] If the PCI_MSI kernel config parameter is
2762 enabled, this kernel boot option can be used to
2763 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002764 noioapicquirk [APIC] Disable all boot interrupt quirks.
2765 Safety option to keep boot IRQs enabled. This
2766 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002767 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2768 primary IO-APIC for bridges that cannot disable
2769 boot IRQs. This fixes a source of spurious IRQs
2770 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002771 noioapicreroute [APIC] Disable workaround that uses the
2772 boot IRQ equivalent of an IRQ that connects to
2773 a chipset where boot IRQs cannot be disabled.
2774 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002775 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002776 routing table. These calls are known to be buggy
2777 on several machines and they hang the machine
2778 when used, but on other computers it's the only
2779 way to get the interrupt routing table. Try
2780 this option if the kernel is unable to allocate
2781 IRQs or discover secondary PCI buses on your
2782 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002783 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002784 Use with caution as certain devices share
2785 address decoders between ROMs and other
2786 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002787 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002788 expansion ROMs that do not already have
2789 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002790 nobar [X86] Do not assign address space to the
2791 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002792 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002793 assigned automatically to PCI devices. You can
2794 make the kernel exclude IRQs of your ISA cards
2795 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002796 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002797 of the PIRQ table (normally generated
2798 by the BIOS) if it is outside the
2799 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002800 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002801 useful if the kernel is unable to find your
2802 secondary buses and you want to tell it
2803 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002804 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002805 numbers ourselves, overriding
2806 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002807 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002808 in the BIOS $PIR table. This is needed on
2809 some systems with broken BIOSes, notably
2810 some HP Pavilion N5400 and Omnibook XE3
2811 notebooks. This will have no effect if ACPI
2812 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002813 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002814 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002815 use_crs [X86] Use PCI host bridge window information
2816 from ACPI. On BIOSes from 2008 or later, this
2817 is enabled by default. If you need to use this,
2818 please report a bug.
2819 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2820 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002821 routeirq Do IRQ routing for all PCI devices.
2822 This is normally done in pci_enable_device(),
2823 so this option is a temporary workaround
2824 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002825 skip_isa_align [X86] do not align io start addr, so can
2826 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002827 firmware [ARM] Do not re-enumerate the bus but instead
2828 just use the configuration from the
2829 bootloader. This is currently used on
2830 IXP2000 systems where the bus has to be
2831 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002832 noearly [X86] Don't do any early type 1 scanning.
2833 This might help on some broken boards which
2834 machine check when some devices' config space
2835 is read. But various workarounds are disabled
2836 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002837 bfsort Sort PCI devices into breadth-first order.
2838 This sorting is done to get a device
2839 order compatible with older (<= 2.4) kernels.
2840 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002841 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2842 tuning and use the BIOS-configured MPS defaults.
2843 pcie_bus_safe Set every device's MPS to the largest value
2844 supported by all devices below the root complex.
2845 pcie_bus_perf Set device MPS to the largest allowable MPS
2846 based on its parent bus. Also set MRRS (Max
2847 Read Request Size) to the largest supported
2848 value (no larger than the MPS that the device
2849 or bus can support) for best performance.
2850 pcie_bus_peer2peer Set every device's MPS to 128B, which
2851 every device is guaranteed to support. This
2852 configuration allows peer-to-peer DMA between
2853 any pair of devices, possibly at the cost of
2854 reduced performance. This also guarantees
2855 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002856 cbiosize=nn[KMG] The fixed amount of bus space which is
2857 reserved for the CardBus bridge's IO window.
2858 The default value is 256 bytes.
2859 cbmemsize=nn[KMG] The fixed amount of bus space which is
2860 reserved for the CardBus bridge's memory
2861 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002862 resource_alignment=
2863 Format:
2864 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2865 Specifies alignment and device to reassign
2866 aligned memory resources.
2867 If <order of align> is not specified,
2868 PAGE_SIZE is used as alignment.
2869 PCI-PCI bridge can be specified, if resource
2870 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002871 ecrc= Enable/disable PCIe ECRC (transaction layer
2872 end-to-end CRC checking).
2873 bios: Use BIOS/firmware settings. This is the
2874 the default.
2875 off: Turn ECRC off
2876 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002877 hpiosize=nn[KMG] The fixed amount of bus space which is
2878 reserved for hotplug bridge's IO window.
2879 Default size is 256 bytes.
2880 hpmemsize=nn[KMG] The fixed amount of bus space which is
2881 reserved for hotplug bridge's memory window.
2882 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002883 realloc= Enable/disable reallocating PCI bridge resources
2884 if allocations done by BIOS are too small to
2885 accommodate resources required by all child
2886 devices.
2887 off: Turn realloc off
2888 on: Turn realloc on
2889 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002890 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002891 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2892 only look for one device below a PCIe downstream
2893 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002894
Chuck Ebberte5665a42008-09-24 20:40:34 -04002895 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2896 Management.
2897 off Disable ASPM.
2898 force Enable ASPM even on devices that claim not to support it.
2899 WARNING: Forcing ASPM on may cause system lockups.
2900
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002901 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2902 nomsi Do not use MSI for PCI Express Native Hotplug (this
2903 makes all PCIe ports use INTx for hotplug services).
2904
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002905 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002906 auto Ask the BIOS whether or not to use native PCIe services
2907 associated with PCIe ports (PME, hot-plug, AER). Use
2908 them only if that is allowed by the BIOS.
2909 native Use native PCIe services associated with PCIe ports
2910 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002911 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2912 ports driver.
2913
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002914 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002915 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002916 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002917
Linus Torvalds1da177e2005-04-16 15:20:36 -07002918 pcmv= [HW,PCMCIA] BadgePAD 4
2919
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302920 pd_ignore_unused
2921 [PM]
2922 Keep all power-domains already enabled by bootloader on,
2923 even if no driver has claimed them. This is useful
2924 for debug and development, but should not be
2925 needed on a platform with proper driver support.
2926
Linus Torvalds1da177e2005-04-16 15:20:36 -07002927 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002928 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002929
2930 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2931 boot time.
2932 Format: { 0 | 1 }
2933 See arch/parisc/kernel/pdc_chassis.c
2934
Tejun Heof58dc012009-08-14 15:00:50 +09002935 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002936 Currently supported values are "embed" and "page".
2937 Archs may support subset or none of the selections.
2938 See comments in mm/percpu.c for details on each
2939 allocator. This parameter is primarily for debugging
2940 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002941
Linus Torvalds1da177e2005-04-16 15:20:36 -07002942 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002943 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944
2945 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002946 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002947
2948 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002949 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002950
2951 plip= [PPT,NET] Parallel port network link
2952 Format: { parport<nr> | timid | 0 }
2953 See also Documentation/parport.txt.
2954
Randy Dunlap16290242011-08-13 12:34:52 -07002955 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002956 Override pmtimer IOPort with a hex value.
2957 e.g. pmtmr=0x508
2958
Bjorn Helgaas96242112011-08-11 12:14:05 -06002959 pnp.debug=1 [PNP]
2960 Enable PNP debug messages (depends on the
2961 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2962 via /sys/module/pnp/parameters/debug. We always show
2963 current resource usage; turning this on also shows
2964 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002965
Linus Torvalds1da177e2005-04-16 15:20:36 -07002966 pnpacpi= [ACPI]
2967 { off }
2968
2969 pnpbios= [ISAPNP]
2970 { on | off | curr | res | no-curr | no-res }
2971
2972 pnp_reserve_irq=
2973 [ISAPNP] Exclude IRQs for the autoconfiguration
2974
2975 pnp_reserve_dma=
2976 [ISAPNP] Exclude DMAs for the autoconfiguration
2977
2978 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002979 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002980
2981 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002982 [ISAPNP] Exclude memory regions for the
2983 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002984 Ranges are in pairs (memory base and size).
2985
Randy Dunlap4af94f32009-04-17 18:30:28 -07002986 ports= [IP_VS_FTP] IPVS ftp helper module
2987 Default is 21.
2988 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2989 may be specified.
2990 Format: <port>,<port>....
2991
Ingo Molnar45807a12007-07-15 23:40:10 -07002992 print-fatal-signals=
2993 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002994
2995 If enabled, warn about various signal handling
2996 related application anomalies: too many signals,
2997 too many POSIX.1 timers, fatal signals causing a
2998 coredump - etc.
2999
3000 If you hit the warning due to signal overflow,
3001 you might want to try "ulimit -i unlimited".
3002
Ingo Molnar45807a12007-07-15 23:40:10 -07003003 default: off.
3004
Matthew Garrettc22ab3322012-03-05 14:59:10 -08003005 printk.always_kmsg_dump=
3006 Trigger kmsg_dump for cases other than kernel oops or
3007 panics
3008 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3009 default: disabled
3010
Randy Dunlape84845c2007-07-15 23:40:25 -07003011 printk.time= Show timing data prefixed to each printk message line
3012 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3013
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003014 processor.max_cstate= [HW,ACPI]
3015 Limit processor to maximum C-state
3016 max_cstate=9 overrides any DMI blacklist limit.
3017
3018 processor.nocst [HW,ACPI]
3019 Ignore the _CST method to determine C-states,
3020 instead using the legacy FADT method
3021
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003023 Format: [schedule,]<number>
3024 Param: "schedule" - profile schedule points.
3025 Param: <number> - step/bucket size as a power of 2 for
3026 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003027 Param: "sleep" - profile D-state sleeping (millisecs).
3028 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003029 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003030
Linus Torvalds1da177e2005-04-16 15:20:36 -07003031 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3032 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003033 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003034
Randy Dunlapa9913042005-10-23 12:57:11 -07003035 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3036 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003037 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3038 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003039 psmouse.resetafter= [HW,MOUSE]
3040 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003041 (0 = never).
3042 psmouse.resolution=
3043 [HW,MOUSE] Set desired mouse resolution, in dpi.
3044 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003045 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003046 0 = disabled, 1 = enabled (default).
3047
Matthew Garrettdee28e72011-07-21 16:57:55 -04003048 pstore.backend= Specify the name of the pstore backend to use
3049
Linus Torvalds1da177e2005-04-16 15:20:36 -07003050 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003051 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003052
Kay Sieversdc8c8582007-08-15 12:25:38 +02003053 pty.legacy_count=
3054 [KNL] Number of legacy pty's. Overwrites compiled-in
3055 default number.
3056
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003057 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003058
Linus Torvalds1da177e2005-04-16 15:20:36 -07003059 r128= [HW,DRM]
3060
3061 raid= [HW,RAID]
3062 See Documentation/md.txt.
3063
Randy Dunlapa9913042005-10-23 12:57:11 -07003064 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003065 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07003066
Linus Torvalds1da177e2005-04-16 15:20:36 -07003067 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003068 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003069
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003070 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003071 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3072 the specified list of CPUs to be no-callback CPUs.
3073 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003074 be offloaded to "rcuox/N" kthreads created for
3075 that purpose, where "x" is "b" for RCU-bh, "p"
3076 for RCU-preempt, and "s" for RCU-sched, and "N"
3077 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003078 offloaded CPUs, which can be useful for HPC and
3079 real-time workloads. It can also improve energy
3080 efficiency for asymmetric multiprocessors.
3081
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003082 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003083 Rather than requiring that offloaded CPUs
3084 (specified by rcu_nocbs= above) explicitly
3085 awaken the corresponding "rcuoN" kthreads,
3086 make these kthreads poll for callbacks.
3087 This improves the real-time response for the
3088 offloaded CPUs by relieving them of the need to
3089 wake up the corresponding kthread, but degrades
3090 energy efficiency by requiring that the kthreads
3091 periodically wake up to do the polling.
3092
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003093 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003094 Set maximum number of finished RCU callbacks to
3095 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003096
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003097 rcutree.dump_tree= [KNL]
3098 Dump the structure of the rcu_node combining tree
3099 out at early boot. This is used for diagnostic
3100 purposes, to verify correct tree setup.
3101
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003102 rcutree.gp_cleanup_delay= [KNL]
3103 Set the number of jiffies to delay each step of
3104 RCU grace-period cleanup. This only has effect
3105 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3106
Paul E. McKenney37745d22015-01-22 18:24:08 -08003107 rcutree.gp_init_delay= [KNL]
3108 Set the number of jiffies to delay each step of
3109 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003110 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3111 is set.
3112
3113 rcutree.gp_preinit_delay= [KNL]
3114 Set the number of jiffies to delay each step of
3115 RCU grace-period pre-initialization, that is,
3116 the propagation of recent CPU-hotplug changes up
3117 the rcu_node combining tree. This only has effect
3118 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003119
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003120 rcutree.rcu_fanout_exact= [KNL]
3121 Disable autobalancing of the rcu_node combining
3122 tree. This is used by rcutorture, and might
3123 possibly be useful for architectures having high
3124 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003125
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003126 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003127 Change the number of CPUs assigned to each
3128 leaf rcu_node structure. Useful for very
3129 large systems, which will choose the value 64,
3130 and for NUMA systems with large remote-access
3131 latencies, which will choose a value aligned
3132 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003133
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003134 rcutree.jiffies_till_sched_qs= [KNL]
3135 Set required age in jiffies for a
3136 given grace period before RCU starts
3137 soliciting quiescent-state help from
3138 rcu_note_context_switch().
3139
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003140 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003141 Set delay from grace-period initialization to
3142 first attempt to force quiescent states.
3143 Units are jiffies, minimum value is zero,
3144 and maximum value is HZ.
3145
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003146 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003147 Set delay between subsequent attempts to force
3148 quiescent states. Units are jiffies, minimum
3149 value is one, and maximum value is HZ.
3150
Clark Williams21871d72014-09-12 21:21:09 -05003151 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003152 Set the SCHED_FIFO priority of the RCU per-CPU
3153 kthreads (rcuc/N). This value is also used for
3154 the priority of the RCU boost threads (rcub/N)
3155 and for the RCU grace-period kthreads (rcu_bh,
3156 rcu_preempt, and rcu_sched). If RCU_BOOST is
3157 set, valid values are 1-99 and the default is 1
3158 (the least-favored priority). Otherwise, when
3159 RCU_BOOST is not set, valid values are 0-99 and
3160 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003161
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003162 rcutree.rcu_nocb_leader_stride= [KNL]
3163 Set the number of NOCB kthread groups, which
3164 defaults to the square root of the number of
3165 CPUs. Larger numbers reduces the wakeup overhead
3166 on the per-CPU grace-period kthreads, but increases
3167 that same overhead on each group's leader.
3168
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003169 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003170 Set threshold of queued RCU callbacks beyond which
3171 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003172
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003173 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003174 Set threshold of queued RCU callbacks below which
3175 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003176
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003177 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003178 Set wakeup interval for idle CPUs that have
3179 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003180
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003181 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003182 Set wakeup interval for idle CPUs that have
3183 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3184 Lazy RCU callbacks are those which RCU can
3185 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003186
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003187 rcutorture.cbflood_inter_holdoff= [KNL]
3188 Set holdoff time (jiffies) between successive
3189 callback-flood tests.
3190
3191 rcutorture.cbflood_intra_holdoff= [KNL]
3192 Set holdoff time (jiffies) between successive
3193 bursts of callbacks within a given callback-flood
3194 test.
3195
3196 rcutorture.cbflood_n_burst= [KNL]
3197 Set the number of bursts making up a given
3198 callback-flood test. Set this to zero to
3199 disable callback-flood testing.
3200
3201 rcutorture.cbflood_n_per_burst= [KNL]
3202 Set the number of callbacks to be registered
3203 in a given burst of a callback-flood test.
3204
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003205 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003206 Set duration of force_quiescent_state bursts
3207 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003208
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003209 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003210 Set holdoff time within force_quiescent_state bursts
3211 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003212
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003213 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003214 Set wait time between force_quiescent_state bursts
3215 in seconds.
3216
3217 rcutorture.gp_cond= [KNL]
3218 Use conditional/asynchronous update-side
3219 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003220
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003221 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003222 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003223
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003224 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003225 Use normal (non-expedited) asynchronous
3226 update-side primitives, if available.
3227
3228 rcutorture.gp_sync= [KNL]
3229 Use normal (non-expedited) synchronous
3230 update-side primitives, if available. If all
3231 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3232 rcutorture.gp_normal=, and rcutorture.gp_sync=
3233 are zero, rcutorture acts as if is interpreted
3234 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003235
3236 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003237 Set callbacks/threads for rcu_barrier() testing.
3238
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003239 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003240 Set number of concurrent RCU writers. These just
3241 stress RCU, they don't participate in the actual
3242 test, hence the "fake".
3243
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003244 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003245 Set number of RCU readers. The value -1 selects
3246 N-1, where N is the number of CPUs. A value
3247 "n" less than -1 selects N-n-2, where N is again
3248 the number of CPUs. For example, -2 selects N
3249 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003250
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003251 rcutorture.object_debug= [KNL]
3252 Enable debug-object double-call_rcu() testing.
3253
3254 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003255 Set time (s) after boot for CPU-hotplug testing.
3256
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003257 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003258 Set time (s) between CPU-hotplug operations, or
3259 zero to disable CPU-hotplug testing.
3260
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003261 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003262 Set task-shuffle interval (s). Shuffling tasks
3263 allows some CPUs to go into dyntick-idle mode
3264 during the rcutorture test.
3265
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003266 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003267 Set time (s) after boot system shutdown. This
3268 is useful for hands-off automated testing.
3269
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003270 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003271 Duration of CPU stall (s) to test RCU CPU stall
3272 warnings, zero to disable.
3273
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003274 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003275 Time to wait (s) after boot before inducing stall.
3276
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003277 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003278 Time (s) between statistics printk()s.
3279
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003280 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003281 Time (s) to stutter testing, for example, specifying
3282 five seconds causes the test to run for five seconds,
3283 wait for five seconds, and so on. This tests RCU's
3284 ability to transition abruptly to and from idle.
3285
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003286 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003287 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3288 "Maybe" means test if the RCU implementation
3289 under test support RCU priority boosting.
3290
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003291 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003292 Duration (s) of each individual boost test.
3293
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003294 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003295 Interval (s) between each boost test.
3296
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003297 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003298 Test RCU's dyntick-idle handling. See also the
3299 rcutorture.shuffle_interval parameter.
3300
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003301 rcutorture.torture_runnable= [BOOT]
3302 Start rcutorture running at boot time.
3303
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003304 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003305 Specify the RCU implementation to test.
3306
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003307 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003308 Enable additional printk() statements.
3309
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003310 rcupdate.rcu_cpu_stall_suppress= [KNL]
3311 Suppress RCU CPU stall warning messages.
3312
3313 rcupdate.rcu_cpu_stall_timeout= [KNL]
3314 Set timeout for RCU CPU stall warning messages.
3315
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003316 rcupdate.rcu_expedited= [KNL]
3317 Use expedited grace-period primitives, for
3318 example, synchronize_rcu_expedited() instead
3319 of synchronize_rcu(). This reduces latency,
3320 but can increase CPU utilization, degrade
3321 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003322 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003323
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003324 rcupdate.rcu_normal= [KNL]
3325 Use only normal grace-period primitives,
3326 for example, synchronize_rcu() instead of
3327 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003328 real-time latency, CPU utilization, and
3329 energy efficiency, but can expose users to
3330 increased grace-period latency. This parameter
3331 overrides rcupdate.rcu_expedited. No effect on
3332 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003333
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003334 rcupdate.rcu_normal_after_boot= [KNL]
3335 Once boot has completed (that is, after
3336 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea022015-12-07 13:09:52 -08003337 only normal grace-period primitives. No effect
3338 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003339
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003340 rcupdate.rcu_task_stall_timeout= [KNL]
3341 Set timeout in jiffies for RCU task stall warning
3342 messages. Disable with a value less than or equal
3343 to zero.
3344
Pranith Kumar74860fe2014-09-19 11:34:09 -04003345 rcupdate.rcu_self_test= [KNL]
3346 Run the RCU early boot self tests
3347
3348 rcupdate.rcu_self_test_bh= [KNL]
3349 Run the RCU bh early boot self tests
3350
3351 rcupdate.rcu_self_test_sched= [KNL]
3352 Run the RCU sched early boot self tests
3353
Olof Johanssonffdfc402005-09-06 15:17:19 -07003354 rdinit= [KNL]
3355 Format: <full_path>
3356 Run specified binary instead of /init from the ramdisk,
3357 used for early userspace startup. See initrd.
3358
Robin Holt1b3a5d02013-07-08 16:01:42 -07003359 reboot= [KNL]
3360 Format (x86 or x86_64):
3361 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3362 [[,]s[mp]#### \
3363 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3364 [[,]f[orce]
3365 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3366 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3367 reboot_force is either force or not specified,
3368 reboot_cpu is s[mp]#### with #### being the processor
3369 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003370
Paul Jackson46b6d942008-07-04 10:00:09 -07003371 relax_domain_level=
3372 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003373 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003374
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003375 relative_sleep_states=
3376 [SUSPEND] Use sleep state labeling where the deepest
3377 state available other than hibernation is always "mem".
3378 Format: { "0" | "1" }
3379 0 -- Traditional sleep state labels.
3380 1 -- Relative sleep state labels.
3381
Linus Torvalds1da177e2005-04-16 15:20:36 -07003382 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3383
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003384 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003385 Format: nn[KMG]
3386 Reserves a hole at the top of the kernel virtual
3387 address space.
3388
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003389 reservelow= [X86]
3390 Format: nn[K]
3391 Set the amount of memory to reserve for BIOS at
3392 the bottom of the address space.
3393
Vivek Goyal7e962872006-09-27 01:50:44 -07003394 reset_devices [KNL] Force drivers to reset the underlying device
3395 during initialization.
3396
Randy Dunlapa9913042005-10-23 12:57:11 -07003397 resume= [SWSUSP]
3398 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003399 Format:
3400 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003401
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003402 resume_offset= [SWSUSP]
3403 Specify the offset from the beginning of the partition
3404 given by "resume=" at which the swap header is located,
3405 in <PAGE_SIZE> units (needed only for swap files).
3406 See Documentation/power/swsusp-and-swap-files.txt
3407
Barry Songf126f732011-10-10 23:38:41 +02003408 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3409 read the resume files
3410
Barry Song6f8d7022011-10-06 20:34:46 +02003411 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3412 Useful for devices that are detected asynchronously
3413 (e.g. USB and MMC devices).
3414
Bojan Smojverf996fc92010-09-09 23:06:23 +02003415 hibernate= [HIBERNATION]
3416 noresume Don't check if there's a hibernation image
3417 present during boot.
3418 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003419 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003420
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003421 retain_initrd [RAM] Keep initrd memory after extraction
3422
Andrew Clausen0efbb782015-01-09 20:24:55 +00003423 rfkill.default_state=
3424 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3425 etc. communication is blocked by default.
3426 1 Unblocked.
3427
3428 rfkill.master_switch_mode=
3429 0 The "airplane mode" button does nothing.
3430 1 The "airplane mode" button toggles between everything
3431 blocked and the previous configuration.
3432 2 The "airplane mode" button toggles between everything
3433 blocked and everything unblocked.
3434
Linus Torvalds1da177e2005-04-16 15:20:36 -07003435 rhash_entries= [KNL,NET]
3436 Set number of hash buckets for route cache
3437
Linus Torvalds1da177e2005-04-16 15:20:36 -07003438 ro [KNL] Mount root device read-only on boot
3439
3440 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003441 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003442
3443 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3444 mount the root filesystem
3445
3446 rootflags= [KNL] Set root filesystem mount option string
3447
3448 rootfstype= [KNL] Set root filesystem type
3449
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003450 rootwait [KNL] Wait (indefinitely) for root device to show up.
3451 Useful for devices that are detected asynchronously
3452 (e.g. USB and MMC devices).
3453
Robert Tivy5c71d612013-03-28 18:41:46 -07003454 rproc_mem=nn[KMG][@address]
3455 [KNL,ARM,CMA] Remoteproc physical memory block.
3456 Memory area to be used by remote processor image,
3457 managed by CMA.
3458
Linus Torvalds1da177e2005-04-16 15:20:36 -07003459 rw [KNL] Mount root device read-write on boot
3460
3461 S [KNL] Run init in single mode
3462
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003463 s390_iommu= [HW,S390]
3464 Set s390 IOTLB flushing mode
3465 strict
3466 With strict flushing every unmap operation will result in
3467 an IOTLB flush. Default is lazy flushing before reuse,
3468 which is faster.
3469
Linus Torvalds1da177e2005-04-16 15:20:36 -07003470 sa1100ir [NET]
3471 See drivers/net/irda/sa1100_ir.c.
3472
Linus Torvalds1da177e2005-04-16 15:20:36 -07003473 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003474
Mike Travisf6630112009-11-17 18:22:15 -06003475 sched_debug [KNL] Enables verbose scheduler debug messages.
3476
Mike Galbraith5307c952012-05-08 12:20:58 +02003477 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3478 xtime_lock contention on larger systems, and/or RCU lock
3479 contention on all systems with CONFIG_MAXSMP set.
3480 Format: { "0" | "1" }
3481 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3482 1 -- enable.
3483 Note: increases power consumption, thus should only be
3484 enabled if running jitter sensitive (HPC/RT) workloads.
3485
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003486 security= [SECURITY] Choose a security module to enable at boot.
3487 If this boot parameter is not specified, only the first
3488 security module asking for security registration will be
3489 loaded. An invalid security module name will be treated
3490 as if no module has been chosen.
3491
3492 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003493 Format: { "0" | "1" }
3494 See security/selinux/Kconfig help text.
3495 0 -- disable.
3496 1 -- enable.
3497 Default value is set via kernel config option.
3498 If enabled at boot time, /selinux/disable can be used
3499 later to disable prior to initial policy load.
3500
John Johansenc1c124e2010-07-29 14:48:09 -07003501 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3502 Format: { "0" | "1" }
3503 See security/apparmor/Kconfig help text
3504 0 -- disable.
3505 1 -- enable.
3506 Default value is set via kernel config option.
3507
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003508 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003509
Linus Torvalds1da177e2005-04-16 15:20:36 -07003510 shapers= [NET]
3511 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003512
Yinghai Lub05f78f2008-08-22 01:32:50 -07003513 show_msr= [x86] show boot-time MSR settings
3514 Format: { <integer> }
3515 Show boot-time (BIOS-initialized) MSR settings.
3516 The parameter means the number of CPUs to show,
3517 for example 1 means boot CPU only.
3518
Linus Torvalds1da177e2005-04-16 15:20:36 -07003519 simeth= [IA-64]
3520 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003521
Linus Torvalds1da177e2005-04-16 15:20:36 -07003522 slram= [HW,MTD]
3523
Joonsoo Kim423c9292014-10-09 15:26:22 -07003524 slab_nomerge [MM]
3525 Disable merging of slabs with similar size. May be
3526 necessary if there is some reason to distinguish
3527 allocs to different slabs. Debug options disable
3528 merging on their own.
3529 For more information see Documentation/vm/slub.txt.
3530
David Rientjes3df1ccc2011-10-18 22:09:28 -07003531 slab_max_order= [MM, SLAB]
3532 Determines the maximum allowed order for slabs.
3533 A high setting may cause OOMs due to memory
3534 fragmentation. Defaults to 1 for systems with
3535 more than 32MB of RAM, 0 otherwise.
3536
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003537 slub_debug[=options[,slabs]] [MM, SLUB]
3538 Enabling slub_debug allows one to determine the
3539 culprit if slab objects become corrupted. Enabling
3540 slub_debug can create guard zones around objects and
3541 may poison objects when not in use. Also tracks the
3542 last alloc / free. For more information see
3543 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003544
3545 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003546 Determines the maximum allowed order for slabs.
3547 A high setting may cause OOMs due to memory
3548 fragmentation. For more information see
3549 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003550
3551 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003552 The minimum number of objects per slab. SLUB will
3553 increase the slab order up to slub_max_order to
3554 generate a sufficiently large slab able to contain
3555 the number of objects indicated. The higher the number
3556 of objects the smaller the overhead of tracking slabs
3557 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003558 For more information see Documentation/vm/slub.txt.
3559
3560 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003561 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003562 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003563 For more information see Documentation/vm/slub.txt.
3564
3565 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003566 Same with slab_nomerge. This is supported for legacy.
3567 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003568
Linus Torvalds1da177e2005-04-16 15:20:36 -07003569 smart2= [HW]
3570 Format: <io1>[,<io2>[,...,<io8>]]
3571
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003572 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3573 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3574 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3575 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3576 smsc-ircc2.ircc_irq= [HW] IRQ line
3577 smsc-ircc2.ircc_dma= [HW] DMA channel
3578 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3579 0: Toshiba Satellite 1800 (GP data pin select)
3580 1: Fast pin select (default)
3581 2: ATC IRMode
3582
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003583 softlockup_panic=
3584 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003585 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003586
Aaron Tomlined235872014-06-23 13:22:05 -07003587 softlockup_all_cpu_backtrace=
3588 [KNL] Should the soft-lockup detector generate
3589 backtraces on all cpus.
3590 Format: <integer>
3591
Linus Torvalds1da177e2005-04-16 15:20:36 -07003592 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003593 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003594
Linus Torvalds1da177e2005-04-16 15:20:36 -07003595 spia_io_base= [HW,MTD]
3596 spia_fio_base=
3597 spia_pedr=
3598 spia_peddr=
3599
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003600 stacktrace [FTRACE]
3601 Enabled the stack tracer on boot up.
3602
Steven Rostedt762e1202011-12-19 22:01:00 -05003603 stacktrace_filter=[function-list]
3604 [FTRACE] Limit the functions that the stack tracer
3605 will trace at boot up. function-list is a comma separated
3606 list of functions. This list can be changed at run
3607 time by the stack_trace_filter file in the debugfs
3608 tracing directory. Note, this enables stack tracing
3609 and the stacktrace above is not needed.
3610
Linus Torvalds1da177e2005-04-16 15:20:36 -07003611 sti= [PARISC,HW]
3612 Format: <num>
3613 Set the STI (builtin display/keyboard on the HP-PARISC
3614 machines) console (graphic card) which should be used
3615 as the initial boot-console.
3616 See also comment in drivers/video/console/sticore.c.
3617
3618 sti_font= [HW]
3619 See comment in drivers/video/console/sticore.c.
3620
3621 stifb= [HW]
3622 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3623
Trond Myklebustcbf11072009-08-09 15:06:19 -04003624 sunrpc.min_resvport=
3625 sunrpc.max_resvport=
3626 [NFS,SUNRPC]
3627 SunRPC servers often require that client requests
3628 originate from a privileged port (i.e. a port in the
3629 range 0 < portnr < 1024).
3630 An administrator who wishes to reserve some of these
3631 ports for other uses may adjust the range that the
3632 kernel's sunrpc client considers to be privileged
3633 using these two parameters to set the minimum and
3634 maximum port values.
3635
Greg Banks42a7fc42007-03-06 01:42:23 -08003636 sunrpc.pool_mode=
3637 [NFS]
3638 Control how the NFS server code allocates CPUs to
3639 service thread pools. Depending on how many NICs
3640 you have and where their interrupts are bound, this
3641 option will affect which CPUs will do NFS serving.
3642 Note: this parameter cannot be changed while the
3643 NFS server is running.
3644
3645 auto the server chooses an appropriate mode
3646 automatically using heuristics
3647 global a single global pool contains all CPUs
3648 percpu one pool for each CPU
3649 pernode one pool for each NUMA node (equivalent
3650 to global on non-NUMA machines)
3651
Trond Myklebustcbf11072009-08-09 15:06:19 -04003652 sunrpc.tcp_slot_table_entries=
3653 sunrpc.udp_slot_table_entries=
3654 [NFS,SUNRPC]
3655 Sets the upper limit on the number of simultaneous
3656 RPC calls that can be sent from the client to a
3657 server. Increasing these values may allow you to
3658 improve throughput, but will also increase the
3659 amount of memory reserved for use by the client.
3660
Brian Norris1d4a9c12015-02-22 21:16:49 -08003661 suspend.pm_test_delay=
3662 [SUSPEND]
3663 Sets the number of seconds to remain in a suspend test
3664 mode before resuming the system (see
3665 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3666 is set. Default value is 5.
3667
Michal Hocko07555ac2013-08-22 16:35:46 -07003668 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003669 [KNL] Enable accounting of swap in memory resource
3670 controller if no parameter or 1 is given or disable
3671 it if 0 is given (See Documentation/cgroups/memory.txt)
3672
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003673 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3674 Format: { <int> | force }
3675 <int> -- Number of I/O TLB slabs
3676 force -- force using of bounce buffers even if they
3677 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003678
Linus Torvalds1da177e2005-04-16 15:20:36 -07003679 switches= [HW,M68k]
3680
Andi Kleene52eec12010-09-08 16:54:17 +02003681 sysfs.deprecated=0|1 [KNL]
3682 Enable/disable old style sysfs layout for old udev
3683 on older distributions. When this option is enabled
3684 very new udev will not work anymore. When this option
3685 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3686 in older udev will not work anymore.
3687 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3688 the kernel configuration.
3689
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003690 sysrq_always_enabled
3691 [KNL]
3692 Ignore sysrq setting - this boot parameter will
3693 neutralize any effect of /proc/sys/kernel/sysrq.
3694 Useful for debugging.
3695
Fabian Frederick747029a2014-11-06 19:46:50 +01003696 tcpmhash_entries= [KNL,NET]
3697 Set the number of tcp_metrics_hash slots.
3698 Default value is 8192 or 16384 depending on total
3699 ram pages. This is used to specify the TCP metrics
3700 cache size. See Documentation/networking/ip-sysctl.txt
3701 "tcp_no_metrics_save" section for more details.
3702
Linus Torvalds1da177e2005-04-16 15:20:36 -07003703 tdfx= [HW,DRM]
3704
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003705 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003706 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003707 standby suspend) or "freeze" (for suspend type freeze)
3708 as the system sleep state during system startup with
3709 the optional capability to repeat N number of times.
3710 The system is woken from this state using a
3711 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003712
Linus Torvalds1da177e2005-04-16 15:20:36 -07003713 thash_entries= [KNL,NET]
3714 Set number of hash buckets for TCP connection
3715
Len Brownf8707ec2007-08-12 00:12:54 -04003716 thermal.act= [HW,ACPI]
3717 -1: disable all active trip points in all thermal zones
3718 <degrees C>: override all lowest active trip points
3719
Len Brownc52a7412007-08-14 15:49:32 -04003720 thermal.crt= [HW,ACPI]
3721 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003722 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003723
Len Brownf5487142007-08-12 00:12:44 -04003724 thermal.nocrt= [HW,ACPI]
3725 Set to disable actions on ACPI thermal zone
3726 critical and hot trip points.
3727
Len Brown72b33ef2007-08-12 00:12:17 -04003728 thermal.off= [HW,ACPI]
3729 1: disable ACPI thermal control
3730
Len Browna70cdc52007-08-12 00:12:35 -04003731 thermal.psv= [HW,ACPI]
3732 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003733 <degrees C>: override all passive trip points to this
3734 value
Len Browna70cdc52007-08-12 00:12:35 -04003735
Len Brown730ff342007-08-12 00:12:26 -04003736 thermal.tzp= [HW,ACPI]
3737 Specify global default ACPI thermal zone polling rate
3738 <deci-seconds>: poll all this frequency
3739 0: no polling (default)
3740
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003741 threadirqs [KNL]
3742 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003743 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003744
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003745 tmem [KNL,XEN]
3746 Enable the Transcendent memory driver if built-in.
3747
3748 tmem.cleancache=0|1 [KNL, XEN]
3749 Default is on (1). Disable the usage of the cleancache
3750 API to send anonymous pages to the hypervisor.
3751
3752 tmem.frontswap=0|1 [KNL, XEN]
3753 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003754 API to send swap pages to the hypervisor. If disabled
3755 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003756
3757 tmem.selfballooning=0|1 [KNL, XEN]
3758 Default is on (1). Disable the driving of swap pages
3759 to the hypervisor.
3760
3761 tmem.selfshrinking=0|1 [KNL, XEN]
3762 Default is on (1). Partial swapoff that immediately
3763 transfers pages from Xen hypervisor back to the
3764 kernel based on different criteria.
3765
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003766 topology= [S390]
3767 Format: {off | on}
3768 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003769 topology information if the hardware supports this.
3770 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003771 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003772 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003773
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003774 topology_updates= [KNL, PPC, NUMA]
3775 Format: {off}
3776 Specify if the kernel should ignore (off)
3777 topology updates sent by the hypervisor to this
3778 LPAR.
3779
Linus Torvalds1da177e2005-04-16 15:20:36 -07003780 tp720= [HW,PS2]
3781
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003782 tpm_suspend_pcr=[HW,TPM]
3783 Format: integer pcr id
3784 Specify that at suspend time, the tpm driver
3785 should extend the specified pcr with zeros,
3786 as a workaround for some chips which fail to
3787 flush the last written pcr on TPM_SaveState.
3788 This will guarantee that all the other pcrs
3789 are saved.
3790
Li Zefan9d612be2009-06-24 17:33:15 +08003791 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003792 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003793
Li Zefan020e5f82009-07-01 10:47:05 +08003794 trace_event=[event-list]
3795 [FTRACE] Set and start specified trace events in order
3796 to facilitate early boot debugging.
3797 See also Documentation/trace/events.txt
3798
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003799 trace_options=[option-list]
3800 [FTRACE] Enable or disable tracer options at boot.
3801 The option-list is a comma delimited list of options
3802 that can be enabled or disabled just as if you were
3803 to echo the option name into
3804
3805 /sys/kernel/debug/tracing/trace_options
3806
3807 For example, to enable stacktrace option (to dump the
3808 stack trace of each event), add to the command line:
3809
3810 trace_options=stacktrace
3811
3812 See also Documentation/trace/ftrace.txt "trace options"
3813 section.
3814
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003815 tp_printk[FTRACE]
3816 Have the tracepoints sent to printk as well as the
3817 tracing ring buffer. This is useful for early boot up
3818 where the system hangs or reboots and does not give the
3819 option for reading the tracing buffer or performing a
3820 ftrace_dump_on_oops.
3821
3822 To turn off having tracepoints sent to printk,
3823 echo 0 > /proc/sys/kernel/tracepoint_printk
3824 Note, echoing 1 into this file without the
3825 tracepoint_printk kernel cmdline option has no effect.
3826
3827 ** CAUTION **
3828
3829 Having tracepoints sent to printk() and activating high
3830 frequency tracepoints such as irq or sched, can cause
3831 the system to live lock.
3832
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003833 traceoff_on_warning
3834 [FTRACE] enable this option to disable tracing when a
3835 warning is hit. This turns off "tracing_on". Tracing can
3836 be enabled again by echoing '1' into the "tracing_on"
3837 file located in /sys/kernel/debug/tracing/
3838
3839 This option is useful, as it disables the trace before
3840 the WARNING dump is called, which prevents the trace to
3841 be filled with content caused by the warning output.
3842
3843 This option can also be set at run time via the sysctl
3844 option: kernel/traceoff_on_warning
3845
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003846 transparent_hugepage=
3847 [KNL]
3848 Format: [always|madvise|never]
3849 Can be used to control the default behavior of the system
3850 with respect to transparent hugepages.
3851 See Documentation/vm/transhuge.txt for more details.
3852
john stultzd3b8f882009-08-17 16:40:47 -07003853 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003854 Format: <string>
3855 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003856 disables clocksource verification at runtime, as well
3857 as the stability checks done at bootup. Used to enable
3858 high-resolution timer mode on older hardware, and in
3859 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003860 [x86] noirqtime: Do not use TSC to do irq accounting.
3861 Used to run time disable IRQ_TIME_ACCOUNTING on any
3862 platforms where RDTSC is slow and this accounting
3863 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003864
Randy Dunlapa9913042005-10-23 12:57:11 -07003865 turbografx.map[2|3]= [HW,JOY]
3866 TurboGraFX parallel port interface
3867 Format:
3868 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003869 See also Documentation/input/joystick-parport.txt
3870
Christian Kujaub6935f82011-05-31 15:22:05 +00003871 udbg-immortal [PPC] When debugging early kernel crashes that
3872 happen after console_init() and before a proper
3873 console driver takes over, this boot options might
3874 help "seeing" what's going on.
3875
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003876 uhash_entries= [KNL,NET]
3877 Set number of hash buckets for UDP/UDP-Lite connections
3878
Alan Stern5f8364b2006-12-05 16:29:55 -05003879 uhci-hcd.ignore_oc=
3880 [USB] Ignore overcurrent events (default N).
3881 Some badly-designed motherboards generate lots of
3882 bogus events, for ports that aren't wired to
3883 anything. Set this parameter to avoid log spamming.
3884 Note that genuine overcurrent events won't be
3885 reported either.
3886
Simon Arlotte3a61b02008-07-19 23:32:54 +01003887 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003888 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003889
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003890 usbcore.authorized_default=
3891 [USB] Default USB device authorization:
3892 (default -1 = authorized except for wireless USB,
3893 0 = not authorized, 1 = authorized)
3894
Alan Sternb5e795f2007-02-20 15:00:53 -05003895 usbcore.autosuspend=
3896 [USB] The autosuspend time delay (in seconds) used
3897 for newly-detected USB devices (default 2). This
3898 is the time required before an idle device will be
3899 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003900 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003901
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003902 usbcore.usbfs_snoop=
3903 [USB] Set to log all usbfs traffic (default 0 = off).
3904
Alan Stern0290cc92015-11-20 13:53:22 -05003905 usbcore.usbfs_snoop_max=
3906 [USB] Maximum number of bytes to snoop in each URB
3907 (default = 65536).
3908
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003909 usbcore.blinkenlights=
3910 [USB] Set to cycle leds on hubs (default 0 = off).
3911
3912 usbcore.old_scheme_first=
3913 [USB] Start with the old device initialization
3914 scheme (default 0 = off).
3915
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003916 usbcore.usbfs_memory_mb=
3917 [USB] Memory limit (in MB) for buffers allocated by
3918 usbfs (default = 16, 0 = max = 2047).
3919
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003920 usbcore.use_both_schemes=
3921 [USB] Try the other device initialization scheme
3922 if the first one fails (default 1 = enabled).
3923
3924 usbcore.initial_descriptor_timeout=
3925 [USB] Specifies timeout for the initial 64-byte
3926 USB_REQ_GET_DESCRIPTOR request in milliseconds
3927 (default 5000 = 5.0 seconds).
3928
Oliver Neukum40d58142015-12-03 15:03:32 +01003929 usbcore.nousb [USB] Disable the USB subsystem
3930
Linus Torvalds1da177e2005-04-16 15:20:36 -07003931 usbhid.mousepoll=
3932 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003933
Alan Sternd4f373e2008-11-10 14:07:45 -05003934 usb-storage.delay_use=
3935 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003936 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003937
3938 usb-storage.quirks=
3939 [UMS] A list of quirks entries to supplement or
3940 override the built-in unusual_devs list. List
3941 entries are separated by commas. Each entry has
3942 the form VID:PID:Flags where VID and PID are Vendor
3943 and Product ID values (4-digit hex numbers) and
3944 Flags is a set of characters, each corresponding
3945 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003946 a = SANE_SENSE (collect more than 18 bytes
3947 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003948 b = BAD_SENSE (don't collect more than 18
3949 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003950 c = FIX_CAPACITY (decrease the reported
3951 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003952 d = NO_READ_DISC_INFO (don't use
3953 READ_DISC_INFO command);
3954 e = NO_READ_CAPACITY_16 (don't use
3955 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003956 f = NO_REPORT_OPCODES (don't use report opcodes
3957 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02003958 g = MAX_SECTORS_240 (don't transfer more than
3959 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003960 h = CAPACITY_HEURISTICS (decrease the
3961 reported device capacity by one
3962 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003963 i = IGNORE_DEVICE (don't bind to this
3964 device);
3965 l = NOT_LOCKABLE (don't try to lock and
3966 unlock ejectable media);
3967 m = MAX_SECTORS_64 (don't transfer more
3968 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003969 n = INITIAL_READ10 (force a retry of the
3970 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003971 o = CAPACITY_OK (accept the capacity
3972 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003973 p = WRITE_CACHE (the device cache is ON
3974 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003975 r = IGNORE_RESIDUE (the device reports
3976 bogus residue values);
3977 s = SINGLE_LUN (the device has only one
3978 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003979 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3980 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003981 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003982 w = NO_WP_DETECT (don't test whether the
3983 medium is write-protected).
3984 Example: quirks=0419:aaf5:rl,0421:0433:rc
3985
Stephen Boydac1667d2011-08-13 12:34:50 -07003986 user_debug= [KNL,ARM]
3987 Format: <int>
3988 See arch/arm/Kconfig.debug help text.
3989 1 - undefined instruction events
3990 2 - system calls
3991 4 - invalid data aborts
3992 8 - SIGSEGV faults
3993 16 - SIGBUS faults
3994 Example: user_debug=31
3995
Ian Campbell14315592010-02-17 10:38:10 +00003996 userpte=
3997 [X86] Flags controlling user PTE allocations.
3998
3999 nohigh = do not allocate PTE pages in
4000 HIGHMEM regardless of setting
4001 of CONFIG_HIGHPTE.
4002
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304003 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004004 On X86_32, this is an alias for vdso32=. Otherwise:
4005
4006 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004007 vdso=0: disable VDSO mapping
4008
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004009 vdso32= [X86] Control the 32-bit vDSO
4010 vdso32=1: enable 32-bit VDSO
4011 vdso32=0 or vdso32=2: disable 32-bit VDSO
4012
4013 See the help text for CONFIG_COMPAT_VDSO for more
4014 details. If CONFIG_COMPAT_VDSO is set, the default is
4015 vdso32=0; otherwise, the default is vdso32=1.
4016
4017 For compatibility with older kernels, vdso32=2 is an
4018 alias for vdso32=0.
4019
4020 Try vdso32=0 if you encounter an error that says:
4021 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004022
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004023 vector= [IA-64,SMP]
4024 vector=percpu: enable percpu vector domain
4025
Linus Torvalds1da177e2005-04-16 15:20:36 -07004026 video= [FB] Frame buffer configuration
4027 See Documentation/fb/modedb.txt.
4028
Aaron Lu3afe6da2013-06-20 15:08:55 +08004029 video.brightness_switch_enabled= [0,1]
4030 If set to 1, on receiving an ACPI notify event
4031 generated by hotkey, video driver will adjust brightness
4032 level and then send out the event to user space through
4033 the allocated input device; If set to 0, video driver
4034 will only send out the event without touching backlight
4035 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004036 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004037
Pawel Moll81a054c2012-05-09 18:30:16 +01004038 virtio_mmio.device=
4039 [VMMIO] Memory mapped virtio (platform) device.
4040
4041 <size>@<baseaddr>:<irq>[:<id>]
4042 where:
4043 <size> := size (can use standard suffixes
4044 like K, M and G)
4045 <baseaddr> := physical base address
4046 <irq> := interrupt number (as passed to
4047 request_irq())
4048 <id> := (optional) platform device id
4049 example:
4050 virtio_mmio.device=1K@0x100b0000:48:7
4051
4052 Can be used multiple times for multiple devices.
4053
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004054 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004055 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004056 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004057 Use vga=ask for menu.
4058 This is actually a boot loader parameter; the value is
4059 passed to the kernel using a special protocol.
4060
Randy Dunlapa9913042005-10-23 12:57:11 -07004061 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004062 size of <nn>. This can be used to increase the
4063 minimum size (128MB on x86). It can also be used to
4064 decrease the size and leave more room for directly
4065 mapped kernel RAM.
4066
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004067 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4068 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004069
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004070 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4071 Format: <command>
4072
4073 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4074 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004075
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004076 vsyscall= [X86-64]
4077 Controls the behavior of vsyscalls (i.e. calls to
4078 fixed addresses of 0xffffffffff600x00 from legacy
4079 code). Most statically-linked binaries and older
4080 versions of glibc use these calls. Because these
4081 functions are at fixed addresses, they make nice
4082 targets for exploits that can control RIP.
4083
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004084 emulate [default] Vsyscalls turn into traps and are
4085 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004086
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004087 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004088 This is a little bit faster than trapping
4089 and makes a few dynamic recompilers work
4090 better than they would in emulation mode.
4091 It also makes exploits much easier to write.
4092
4093 none Vsyscalls don't work at all. This makes
4094 them quite hard to use for exploits but
4095 might break your system.
4096
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004097 vt.color= [VT] Default text color.
4098 Format: 0xYX, X = foreground, Y = background.
4099 Default: 0x07 = light gray on black.
4100
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004101 vt.cur_default= [VT] Default cursor shape.
4102 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4103 the parameters of the <Esc>[?A;B;Cc escape sequence;
4104 see VGA-softcursor.txt. Default: 2 = underline.
4105
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004106 vt.default_blu= [VT]
4107 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4108 Change the default blue palette of the console.
4109 This is a 16-member array composed of values
4110 ranging from 0-255.
4111
4112 vt.default_grn= [VT]
4113 Format: <green0>,<green1>,<green2>,...,<green15>
4114 Change the default green palette of the console.
4115 This is a 16-member array composed of values
4116 ranging from 0-255.
4117
4118 vt.default_red= [VT]
4119 Format: <red0>,<red1>,<red2>,...,<red15>
4120 Change the default red palette of the console.
4121 This is a 16-member array composed of values
4122 ranging from 0-255.
4123
4124 vt.default_utf8=
4125 [VT]
4126 Format=<0|1>
4127 Set system-wide default UTF-8 mode for all tty's.
4128 Default is 1, i.e. UTF-8 mode is enabled for all
4129 newly opened terminals.
4130
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004131 vt.global_cursor_default=
4132 [VT]
4133 Format=<-1|0|1>
4134 Set system-wide default for whether a cursor
4135 is shown on new VTs. Default is -1,
4136 i.e. cursors will be created by default unless
4137 overridden by individual drivers. 0 will hide
4138 cursors, 1 will display them.
4139
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004140 vt.italic= [VT] Default color for italic text; 0-15.
4141 Default: 2 = green.
4142
4143 vt.underline= [VT] Default color for underlined text; 0-15.
4144 Default: 3 = cyan.
4145
Randy Dunlap4724ba572010-05-03 11:42:52 -07004146 watchdog timers [HW,WDT] For information on watchdog timers,
4147 see Documentation/watchdog/watchdog-parameters.txt
4148 or other driver-specific files in the
4149 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004150
Tejun Heo82607adc2015-12-08 11:28:04 -05004151 workqueue.watchdog_thresh=
4152 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4153 warn stall conditions and dump internal state to
4154 help debugging. 0 disables workqueue stall
4155 detection; otherwise, it's the stall threshold
4156 duration in seconds. The default value is 30 and
4157 it can be updated at runtime by writing to the
4158 corresponding sysfs file.
4159
Tejun Heod55262c2013-04-01 11:23:38 -07004160 workqueue.disable_numa
4161 By default, all work items queued to unbound
4162 workqueues are affine to the NUMA nodes they're
4163 issued on, which results in better behavior in
4164 general. If NUMA affinity needs to be disabled for
4165 whatever reason, this option can be used. Note
4166 that this also can be controlled per-workqueue for
4167 workqueues visible under /sys/bus/workqueue/.
4168
Viresh Kumarcee22a12013-04-08 16:45:40 +05304169 workqueue.power_efficient
4170 Per-cpu workqueues are generally preferred because
4171 they show better performance thanks to cache
4172 locality; unfortunately, per-cpu workqueues tend to
4173 be more power hungry than unbound workqueues.
4174
4175 Enabling this makes the per-cpu workqueues which
4176 were observed to contribute significantly to power
4177 consumption unbound, leading to measurably lower
4178 power usage at the cost of small performance
4179 overhead.
4180
4181 The default value of this parameter is determined by
4182 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4183
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004184 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4185 default x2apic cluster mode on platforms
4186 supporting x2apic.
4187
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004188 x86_intel_mid_timer= [X86-32,APBT]
4189 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004190 Two valid options are apbt timer only and lapic timer
4191 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004192 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004193
Juergen Grossc70727a2015-07-17 06:51:36 +02004194 xen_512gb_limit [KNL,X86-64,XEN]
4195 Restricts the kernel running paravirtualized under Xen
4196 to use only up to 512 GB of RAM. The reason to do so is
4197 crash analysis tools and Xen tools for doing domain
4198 save/restore/migration must be enabled to handle larger
4199 domains.
4200
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004201 xen_emul_unplug= [HW,X86,XEN]
4202 Unplug Xen emulated devices
4203 Format: [unplug0,][unplug1]
4204 ide-disks -- unplug primary master IDE devices
4205 aux-ide-disks -- unplug non-primary-master IDE devices
4206 nics -- unplug network devices
4207 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004208 unnecessary -- unplugging emulated devices is
4209 unnecessary even if the host did not respond to
4210 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004211 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004212
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004213 xen_nopvspin [X86,XEN]
4214 Disables the ticketlock slowpath using Xen PV
4215 optimizations.
4216
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004217 xen_nopv [X86]
4218 Disables the PV optimizations forcing the HVM guest to
4219 run as generic HVM guest with no PV drivers.
4220
Linus Torvalds1da177e2005-04-16 15:20:36 -07004221 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004222 Format:
4223 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004224
Randy Dunlapa9913042005-10-23 12:57:11 -07004225______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004226
4227TODO:
4228
Linus Torvalds1da177e2005-04-16 15:20:36 -07004229 Add more DRM drivers.