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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
Rusty Russell5888bcc2014-05-14 10:33:45 +09304The following is a consolidated list of the kernel parameters as
5implemented by the __setup(), core_param() and module_param() macros
6and sorted into English Dictionary order (defined as ignoring all
7punctuation and sorting digits before letters in a case insensitive
8manner), and with descriptions where known.
Linus Torvalds1da177e2005-04-16 15:20:36 -07009
Rusty Russell5888bcc2014-05-14 10:33:45 +093010The kernel parses parameters from the kernel command line up to "--";
11if it doesn't recognize a parameter and it doesn't contain a '.', the
12parameter gets passed to init: parameters with '=' go into init's
13environment, others are passed as command line arguments to init.
14Everything after "--" is passed as an argument to init.
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Rusty Russell5888bcc2014-05-14 10:33:45 +093016Module parameters can be specified in two ways: via the kernel command
17line with a module name prefix, or via modprobe, e.g.:
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Rusty Russell5888bcc2014-05-14 10:33:45 +093019 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Rusty Russell5888bcc2014-05-14 10:33:45 +093022Parameters for modules which are built into the kernel need to be
23specified on the kernel command line. modprobe looks through the
24kernel command line (/proc/cmdline) and collects module parameters
25when it loads a module, so the kernel command line can be used for
26loadable modules too.
Linus Torvalds1da177e2005-04-16 15:20:36 -070027
Randy Dunlapca1eda22009-05-06 16:02:58 -070028Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30can also be entered as
31 log-buf-len=1M print_fatal_signals=1
32
Rusty Russell5888bcc2014-05-14 10:33:45 +093033Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
Randy Dunlapca1eda22009-05-06 16:02:58 -070035
Stefan Richtera901ebb2006-04-01 01:43:18 +020036This document may not be entirely up to date and comprehensive. The command
37"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38module. Loadable modules, after being loaded into the running kernel, also
39reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40parameters may be changed at runtime by the command
41"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
42
Stefan Richter6585fa82006-04-01 01:44:30 +020043The parameters listed below are only valid if certain kernel build options were
44enabled and if respective hardware is present. The text in square brackets at
45the beginning of each description states the restrictions within which a
46parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100049 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070053 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020054 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080056 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070057 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070058 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000059 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040064 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070066 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070067 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050070 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070072 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080073 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050077 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020078 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070079 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070086 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070088 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070089 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070094 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070098 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -0700107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -0700109 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700111 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900113 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300118 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500120 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100124 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700129 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700132 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100134 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136In addition, the following text indicates that the option:
137
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
141
142Parameters denoted with BOOT are actually interpreted by the boot
143loader, and have no meaning to the kernel directly.
144Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500145need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146
Karsten Weiss55588702007-02-13 13:26:21 +0100147There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700148See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100149
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151a trailing = on the name of any parameter states that that parameter will
152be entered as an environment variable, whereas its absence indicates that
153it will appear as a kernel argument readable via /proc/cmdline by programs
154running once the system is up.
155
jens m. noedler9c4751f2006-09-29 02:00:27 -0700156The number of kernel parameters is not limited, but the length of the
157complete command line (parameters including spaces etc.) is limited to
158a fixed number of characters. This limit depends on the architecture
159and is between 256 and 4096 characters. It is defined in the file
160./include/asm/setup.h as COMMAND_LINE_SIZE.
161
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800162Finally, the [KMG] suffix is commonly described after a number of kernel
163parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165bytes respectively. Such letter suffixes can also be entirely omitted.
166
jens m. noedler9c4751f2006-09-29 02:00:27 -0700167
Al Stoneb10d79f2015-03-24 14:02:41 +0000168 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800169 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500170 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700174 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800176 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800177 copy_dsdt -- copy DSDT to memory
Al Stoneb10d79f2015-03-24 14:02:41 +0000178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179
Paul Bolle395cf962011-08-15 02:02:26 +0200180 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181
Len Browna1fdcc02007-03-11 03:26:14 -0400182 acpi_apic_instance= [ACPI, IOAPIC]
183 Format: <int>
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400186 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400187
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
190 acpi_backlight=video
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
194
Dominik Brodowskief694492015-05-14 15:31:28 +0200195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
202
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200226
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800230
Dominik Brodowskief694492015-05-14 15:31:28 +0200231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
246
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
250 size limitation.
251
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
254 default in APIC mode
255
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
258 default in PIC mode
259
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
262
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
264 use by PCI
265 Format: <irq>,<irq>...
266
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800272 This feature is enabled by default.
273 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800274
Dominik Brodowskief694492015-05-14 15:31:28 +0200275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
276 kernels.
277
Lv Zhenga94e88c2014-04-04 12:39:11 +0800278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700287
Dominik Brodowskief694492015-05-14 15:31:28 +0200288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
295
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
301
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800305 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800306 acpi_osi=! # disable all built-in OS vendor
307 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700308 acpi_osi= # disable all strings
309
Lv Zheng5dc17982013-07-22 16:08:25 +0800310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800320 Examples:
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
324
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
330 meaningless.
331 Examples:
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
333 FALSE.
334
Lv Zheng741d8122013-07-22 16:08:36 +0800335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
345 the OSPM features.
346 Examples:
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
352 equivalent to
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
354 and
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
357
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530358 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
362
Randy Dunlap4af94f32009-04-17 18:30:28 -0700363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
365
Randy Dunlap4af94f32009-04-17 18:30:28 -0700366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
369
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200372 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700373 See Documentation/power/video.txt for information on
374 s3_bios and s3_mode.
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700388
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
392
Randy Dunlap4af94f32009-04-17 18:30:28 -0700393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
395
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700396 agp= [AGP]
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
401
Randy Dunlapbcfde332010-06-07 17:10:38 -0700402 ALSA [HW,ALSA]
403 See Documentation/sound/alsa/alsa-parameters.txt
404
Russell Kingd944d542010-02-20 16:13:29 +0000405 alignment= [KNL,ARM]
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
409
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
417
Borislav Petkov8360ee22011-11-21 12:10:19 +0100418 32: only for 32-bit processes
419 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
422
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
429
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100430 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200431 Pass parameters to the AMD IOMMU driver in the system.
432 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
436 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200437 off - do not initialize any AMD IOMMU found in
438 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900444
Shuah Khanc099cf12012-05-24 15:58:25 -0600445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
450
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
453 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200454 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
460
Randy Dunlapa9913042005-10-23 12:57:11 -0700461 apc= [HW,SPARC]
462 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 Format: noidle
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
467
Randy Dunlapca1eda22009-05-06 16:02:58 -0700468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700469 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700473
Brian Haleyb0f83b22010-02-04 13:36:50 -0800474 autoconf= [IPV6]
475 See Documentation/networking/ipv6.txt.
476
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
485
Linus Torvalds1da177e2005-04-16 15:20:36 -0700486 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700487 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
491
492 ataflop= [HW,M68k]
493
494 atarimouse= [HW,MOUSE] Atari Mouse
495
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
498
499 atkbd.reset= [HW] Reset keyboard during initialization
500
Randy Dunlapa9913042005-10-23 12:57:11 -0700501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
505 keyboards
506
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700509
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
522 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400523 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400524
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
527 Default: 64
528
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 baycom_epp= [HW,AX25]
530 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700531
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
533 Format: <io>,<mode>
534 See header of drivers/net/hamradio/baycom_par.c.
535
Randy Dunlapa9913042005-10-23 12:57:11 -0700536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
540
Randy Dunlapa9913042005-10-23 12:57:11 -0700541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
545
Paul Gortmaker080506a2013-09-30 13:45:19 -0700546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
549
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
552 no delay (0).
553 Format: integer
554
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700558 bttv.radio= Most important insmod options are available as
559 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200561 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
565 at a time.
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 c101= [NET] Moxa C101 synchronous serial card
568
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
575
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
578 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300579 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300580
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
585 others).
586
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589
Paul Menage8bab8dd2008-04-04 14:29:57 -0700590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
594 a single hierarchy
595 - foo isn't visible as an individually mountable
596 subsystem
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700600
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700608 Value can be changed at runtime via
609 /selinux/checkreqprot.
610
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100611 cio_ignore= [S390]
612 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700613 clk_ignore_unused
614 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100624
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700626 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200627 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700628 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200629 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 Format: { pit | tsc | cyclone | pmtmr }
631
John Stultz592913e2010-07-13 17:56:20 -0700632 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700633 Format: <string>
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
637 the platform:
638 [all] jiffies (this is the base, fallback clocksource)
639 [ACPI] acpi_pm
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
642 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700643 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700644 scx200_hrt on Geode; cyclone on IBM x440
645 [MIPS] MIPS
646 [PARISC] cr16
647 [S390] tod
648 [SH] SuperH
649 [SPARC64] tick
650 [X86-64] hpet,tsc
651
Andi Kleenac72e782008-01-30 13:33:21 +0100652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100656 stable over kernel options, but the vendor specific
657 ones should be.
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
663 some critical bits.
664
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700665 cma=nn[MG]@[start[MG][-end[MG]]]
666 [ARM,X86,KNL]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100672 include/linux/dma-contiguous.h
673
Robert Jennings14f966e2009-04-15 05:55:32 +0000674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
678 a hypervisor.
679 Default: yes
680
Marek Szyprowskic7909502011-12-29 13:09:51 +0100681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200683 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100684
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530685 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100686 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100687 Range: 0 - 8192
688 Default: 64
689
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700691 Format:
692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693
694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
695 Format: <io>[,<irq>]
696
Randy Dunlapa9913042005-10-23 12:57:11 -0700697 com90xx= [HW,NET]
698 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 Format: <io>[,<irq>[,<memstart>]]
700
701 condev= [HW,S390] console device
702 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700703
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 console= [KNL] Output console device and options.
705
706 tty<n> Use the virtual console device <n>.
707
708 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800709 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800711 the form "bbbbpnf", where "bbbb" is the baud rate,
712 "p" is parity ("n", "o", or "e"), "n" is number of
713 bits, and "f" is flow control ("r" for RTS or
714 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800716 See Documentation/serial-console.txt for more
717 information. See
718 Documentation/networking/netconsole.txt for an
719 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
734
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
740 console=brl,ttyS0
741 For now, only VisioBraille is supported.
742
Daniel Mackf324edc2009-06-16 15:33:52 -0700743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
746
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800747 coredump_filter=
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
751
Len Brown62027ae2011-04-01 18:13:10 -0400752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
754
Len Brownd68921f2015-05-11 17:27:09 -0400755 cpu_init_udelay=N
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
759 Default: 10000
760
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700762 Format:
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700772
Bernhard Wallefb391592007-10-18 23:41:02 -0700773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800778 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700779
Yinghai Luadbc7422013-04-15 22:23:48 -0700780 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
785 available.
786 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800792 requires at least 64M+32K low memory, also enough extra
793 low memory is needed to make sure DMA buffers for 32-bit
794 devices won't run out. Kernel would try to allocate at
795 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700796 This one let user to specify own low range under 4G
797 for second kernel instead.
798 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700799 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700800 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700801
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802 cs89x0_dma= [HW,NET]
803 Format: <dma>
804
805 cs89x0_media= [HW,NET]
806 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700807
Randy Dunlapa9913042005-10-23 12:57:11 -0700808 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 See header of drivers/s390/block/dasd_devmap.c.
810
811 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
812 (one device per port)
813 Format: <port#>,<type>
814 See also Documentation/input/joystick-parport.txt
815
Thomas Renningera648ec02010-08-06 16:11:02 +0200816 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
817 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600818 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200819
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 debug [KNL] Enable kernel debugging (events log level).
821
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700822 debug_locks_verbose=
823 [KNL] verbose self-tests
824 Format=<0|1>
825 Print debugging info while doing the locking API
826 self-tests.
827 We default to 0 (no extra messages), setting it to
828 1 will print _a lot_ more information - normally
829 only useful to kernel developers.
830
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700831 debug_objects [KNL] Enable object debugging
832
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500833 no_debug_objects
834 [KNL] Disable object debugging
835
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800836 debug_guardpage_minorder=
837 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
838 parameter allows control of the order of pages that will
839 be intentionally kept free (and hence protected) by the
840 buddy allocator. Bigger value increase the probability
841 of catching random memory corruption, but reduce the
842 amount of memory for normal system use. The maximum
843 possible value is MAX_ORDER/2. Setting this parameter
844 to 1 or 2 should be enough to identify most random
845 memory corruption problems caused by bugs in kernel or
846 driver code when a CPU writes to (or reads from) a
847 random memory location. Note that there exists a class
848 of memory corruptions problems caused by buggy H/W or
849 F/W or by drivers badly programing DMA (basically when
850 memory is written at bus level and the CPU MMU is
851 bypassed) which are not detectable by
852 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
853 tracking down these problems.
854
Joonsoo Kim031bc572014-12-12 16:55:52 -0800855 debug_pagealloc=
856 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
857 parameter enables the feature at boot time. In
858 default, it is disabled. We can avoid allocating huge
859 chunk of memory for debug pagealloc if we don't enable
860 it at boot time and the system will work mostly same
861 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
862 on: enable the feature
863
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200864 debugpat [X86] Enable PAT debugging
865
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200866 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700867 Format: <area>[,<node>]
868 See also Documentation/networking/decnet.txt.
869
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700870 default_hugepagesz=
871 [same as hugepagesz=] The size of the default
872 HugeTLB page size. This is the size represented by
873 the legacy /proc/ hugepages APIs, used for SHM, and
874 default size when mounting hugetlbfs filesystems.
875 Defaults to the default architecture's huge page size
876 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700877
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 dhash_entries= [KNL]
879 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700880
Brian Haleyb0f83b22010-02-04 13:36:50 -0800881 disable= [IPV6]
882 See Documentation/networking/ipv6.txt.
883
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900884 disable_cpu_apicid= [X86,APIC,SMP]
885 Format: <int>
886 The number of initial APIC ID for the
887 corresponding CPU to be disabled at boot,
888 mostly used for the kdump 2nd kernel to
889 disable BSP to wake up multiple CPUs without
890 causing system reset or hang due to sending
891 INIT from AP to BSP.
892
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000893 disable_ddw [PPC/PSERIES]
894 Disable Dynamic DMA Window support. Use this if
895 to workaround buggy firmware.
896
Brian Haleyb0f83b22010-02-04 13:36:50 -0800897 disable_ipv6= [IPV6]
898 See Documentation/networking/ipv6.txt.
899
Yinghai Lu95ffa242008-04-29 03:52:33 -0700900 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700901 The kernel tries to adjust MTRR layout from continuous
902 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700903 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700904
Yinghai Lu093af8d2008-01-30 13:33:32 +0100905 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100906 By default the kernel will trim any uncacheable
907 memory out of your available memory pool based on
908 MTRR settings. This parameter disables that behavior,
909 possibly causing your machine to run very slowly.
910
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530911 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700912 Disable PIN 1 of APIC timer
913 Can be useful to work around chipset bugs.
914
Prarit Bhargavace14c582015-08-25 13:34:53 -0400915 dis_ucode_ldr [X86] Disable the microcode loader.
916
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700917 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
918 this option disables the debugging code at boot.
919
920 dma_debug_entries=<number>
921 This option allows to tune the number of preallocated
922 entries for DMA-API debugging code. One entry is
923 required per DMA-API allocation. Use this if the
924 DMA-API debugging code disables itself because the
925 architectural default is too low.
926
Joerg Roedel1745de52009-05-22 21:49:51 +0200927 dma_debug_driver=<driver_name>
928 With this option the DMA-API debugging driver
929 filter feature can be enabled at boot time. Just
930 pass the driver to filter for as the parameter.
931 The filter can be disabled or changed to another
932 driver later using sysfs.
933
Carsten Emdeda0df922012-03-18 22:37:33 +0100934 drm_kms_helper.edid_firmware=[<connector>:]<file>
935 Broken monitors, graphic adapters and KVMs may
936 send no or incorrect EDID data sets. This parameter
937 allows to specify an EDID data set in the
938 /lib/firmware directory that is used instead.
939 Generic built-in EDID data sets are used, if one of
940 edid/1024x768.bin, edid/1280x1024.bin,
941 edid/1680x1050.bin, or edid/1920x1080.bin is given
942 and no file with the same name exists. Details and
943 instructions how to build your own EDID data are
944 available in Documentation/EDID/HOWTO.txt. An EDID
945 data set will only be used for a particular connector,
946 if its name and a colon are prepended to the EDID
947 name.
948
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949 dscc4.setup= [NET]
950
Jim Cromie29e36c92012-04-27 14:30:41 -0600951 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
952 module.dyndbg[="val"]
953 Enable debug messages at boot time. See
954 Documentation/dynamic-debug-howto.txt for details.
955
Dave Hansen8c3641e2015-06-07 11:37:02 -0700956 nompx [X86] Disables Intel Memory Protection Extensions.
957 See Documentation/x86/intel_mpx.txt for more
958 information about the feature.
959
Borislav Petkovf29ba612015-03-27 16:15:18 +0100960 eagerfpu= [X86]
961 on enable eager fpu restore
962 off disable eager fpu restore
963 auto selects the default scheme, which automatically
964 enables eagerfpu restore for xsaveopt.
965
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700966 module.async_probe [KNL]
967 Enable asynchronous probe on this module.
968
Mark Salter56aeeba2014-04-07 15:39:53 -0700969 early_ioremap_debug [KNL]
970 Enable debug messages in early_ioremap support. This
971 is useful for tracking down temporary early mappings
972 which are not unmapped.
973
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700974 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500975
Scott Wood5664f762015-09-14 19:54:07 -0500976 When used with no options, the early console is
977 determined by the stdout-path property in device
978 tree's chosen node.
979
Michal Simek6fa62fc2014-09-10 12:43:02 +0200980 cdns,<addr>
981 Start an early, polled-mode console on a cadence serial
982 port at the specified address. The cadence serial port
983 must already be setup and configured. Options are not
984 yet supported.
985
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700986 uart[8250],io,<addr>[,options]
987 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700988 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300989 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400990 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700991 Start an early, polled-mode console on the 8250/16550
992 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700993 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300994 (mmio) or 32-bit (mmio32 or mmio32be).
995 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
996 to be equivalent to 'mmio'. 'options' are specified
997 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400998 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700999
Rob Herring0d3c6732014-04-18 17:19:57 -05001000 pl011,<addr>
1001 Start an early, polled-mode console on a pl011 serial
1002 port at the specified address. The pl011 serial port
1003 must already be setup and configured. Options are not
1004 yet supported.
1005
Stephen Boyd0efe7292014-09-15 17:22:51 -07001006 msm_serial,<addr>
1007 Start an early, polled-mode console on an msm serial
1008 port at the specified address. The serial port
1009 must already be setup and configured. Options are not
1010 yet supported.
1011
1012 msm_serial_dm,<addr>
1013 Start an early, polled-mode console on an msm serial
1014 dm port at the specified address. The serial port
1015 must already be setup and configured. Options are not
1016 yet supported.
1017
Rob Herringd50d7262014-04-18 17:19:58 -05001018 smh Use ARM semihosting calls for early console.
1019
Tomasz Figab94ba032015-01-23 14:47:41 +01001020 s3c2410,<addr>
1021 s3c2412,<addr>
1022 s3c2440,<addr>
1023 s3c6400,<addr>
1024 s5pv210,<addr>
1025 exynos4210,<addr>
1026 Use early console provided by serial driver available
1027 on Samsung SoCs, requires selecting proper type and
1028 a correct base address of the selected UART port. The
1029 serial port must already be setup and configured.
1030 Options are not yet supported.
1031
Finn Thain7913ad12014-04-12 23:48:56 +10001032 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001034 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001035 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001037 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001038 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001039 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001040 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041
Dave Hansen147ea092013-04-10 14:03:38 -07001042 earlyprintk is useful when the kernel crashes before
1043 the normal console is initialized. It is not enabled by
1044 default because it has some cosmetic problems.
1045
Randy Dunlapa9913042005-10-23 12:57:11 -07001046 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 takes over.
1048
Matt Fleming72548e82013-10-04 09:36:56 +01001049 Only one of vga, efi, serial, or usb debug port can
1050 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051
Dave Hansen147ea092013-04-10 14:03:38 -07001052 Currently only ttyS0 and ttyS1 may be specified by
1053 name. Other I/O ports may be explicitly specified
1054 on some architectures (x86 and arm at least) by
1055 replacing ttySn with an I/O port address, like this:
1056 earlyprintk=serial,0x1008,115200
1057 You can find the port for a given device in
1058 /proc/tty/driver/serial:
1059 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060
1061 Interaction with the standard serial driver is not
1062 very good.
1063
Matt Fleming72548e82013-10-04 09:36:56 +01001064 The VGA and EFI output is eventually overwritten by
1065 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001067 The xen output can only be used by Xen PV guests.
1068
Chen, Gongc700f012013-12-06 01:17:08 -05001069 edac_report= [HW,EDAC] Control how to report EDAC event
1070 Format: {"on" | "off" | "force"}
1071 on: enable EDAC to report H/W event. May be overridden
1072 by other higher priority error reporting module.
1073 off: disable H/W event reporting through EDAC.
1074 force: enforce the use of EDAC to report H/W event.
1075 default: on.
1076
Jason Wessel97311912010-05-20 21:04:30 -05001077 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1078 ekgdboc=kbd
1079
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001080 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001081 the boot argument: earlyprintk=vga
1082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001084 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001085
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001086 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001087 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001088 old_map [X86-64]: switch to the old ioremap-based EFI
1089 runtime services mapping. 32-bit still uses this one by
1090 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001091 nochunk: disable reading files in "chunks" in the EFI
1092 boot stub, as chunking can cause problems with some
1093 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001094 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001095 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001096
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001097 efi_no_storage_paranoia [EFI; X86]
1098 Using this parameter you can use more than 50% of
1099 your efi variable storage. Use this parameter only if
1100 you are really sure that your UEFI does sane gc and
1101 fulfills the spec otherwise your board may brick.
1102
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 eisa_irq_edge= [PARISC,HW]
1104 See header of drivers/parisc/eisa.c.
1105
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001106 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001108 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109
1110 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001111 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001112 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001113 Documentation/block/deadline-iosched.txt for details.
1114
Michael Holzheud3bf37952011-10-30 15:16:37 +01001115 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001116 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001117 image elf header and optionally the size. Generally
1118 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001119 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001120
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001121 enable_mtrr_cleanup [X86]
1122 The kernel tries to adjust MTRR layout from continuous
1123 to discrete, to make X server driver able to add WB
1124 entry later. This parameter enables that.
1125
Randy Dunlapca1eda22009-05-06 16:02:58 -07001126 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001127 Enable PIN 1 of APIC timer
1128 Can be useful to work around chipset bugs
1129 (in particular on some ATI chipsets).
1130 The kernel tries to set a reasonable default.
1131
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 enforcing [SELINUX] Set initial enforcing status.
1133 Format: {"0" | "1"}
1134 See security/selinux/Kconfig help text.
1135 0 -- permissive (log only, no denials).
1136 1 -- enforcing (deny and log).
1137 Default value is 0.
1138 Value can be changed at runtime via /selinux/enforce.
1139
Huang Yinga08f82d2010-05-18 14:35:21 +08001140 erst_disable [ACPI]
1141 Disable Error Record Serialization Table (ERST)
1142 support.
1143
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144 ether= [HW,NET] Ethernet cards parameters
1145 This option is obsoleted by the "netdev=" option, which
1146 has equivalent usage. See its documentation for details.
1147
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001148 evm= [EVM]
1149 Format: { "fix" }
1150 Permit 'security.evm' to be updated regardless of
1151 current integrity status.
1152
Akinobu Mitade1ba092006-12-08 02:39:42 -08001153 failslab=
1154 fail_page_alloc=
1155 fail_make_request=[KNL]
1156 General fault injection mechanism.
1157 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001158 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001159
Linus Torvalds1da177e2005-04-16 15:20:36 -07001160 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001161 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162
Alex Chiangf13ae302008-05-08 14:03:23 -06001163 force_pal_cache_flush
1164 [IA-64] Avoid check_sal_cache_flush which may hang on
1165 buggy SAL_CACHE_FLUSH implementations. Using this
1166 parameter will force ia64_sal_cache_flush to call
1167 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1168
Chris Bainbridge69f23662014-03-07 18:40:42 +07001169 forcepae [X86-32]
1170 Forcefully enable Physical Address Extension (PAE).
1171 Many Pentium M systems disable PAE but may have a
1172 functionally usable PAE implementation.
1173 Warning: use of this parameter will taint the kernel
1174 and may cause unknown problems.
1175
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001176 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001177 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001178 as early as possible in order to facilitate early
1179 boot debugging.
1180
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001181 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001182 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001183 If no parameter is passed, ftrace will dump
1184 buffers of all CPUs, but if you pass orig_cpu, it will
1185 dump only the buffer of the CPU that triggered the
1186 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001187
1188 ftrace_filter=[function-list]
1189 [FTRACE] Limit the functions traced by the function
1190 tracer at boot up. function-list is a comma separated
1191 list of functions. This list can be changed at run
1192 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001193 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001194
1195 ftrace_notrace=[function-list]
1196 [FTRACE] Do not trace the functions specified in
1197 function-list. This list can be changed at run time
1198 by the set_ftrace_notrace file in the debugfs
1199 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001200
Stefan Assmann369bc182009-10-12 22:17:21 +02001201 ftrace_graph_filter=[function-list]
1202 [FTRACE] Limit the top level callers functions traced
1203 by the function graph tracer at boot up.
1204 function-list is a comma separated list of functions
1205 that can be changed at run time by the
1206 set_graph_function file in the debugfs tracing directory.
1207
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001208 ftrace_graph_notrace=[function-list]
1209 [FTRACE] Do not trace from the functions specified in
1210 function-list. This list is a comma separated list of
1211 functions that can be changed at run time by the
1212 set_graph_notrace file in the debugfs tracing directory.
1213
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 gamecon.map[2|3]=
1215 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1216 support via parallel port (up to 5 devices per port)
1217 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1218 See also Documentation/input/joystick-parport.txt
1219
1220 gamma= [HW,DRM]
1221
Yinghai Luaaf23042008-01-30 13:33:09 +01001222 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1223 Format: off | on
1224 default: on
1225
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001226 gcov_persist= [GCOV] When non-zero (default), profiling data for
1227 kernel modules is saved and remains accessible via
1228 debugfs, even when the module is unloaded/reloaded.
1229 When zero, profiling data is discarded and associated
1230 debugfs files are removed at module unload time.
1231
Linus Torvalds1da177e2005-04-16 15:20:36 -07001232 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001233 invalid Protective MBR to be treated as GPT. If the
1234 primary GPT is corrupted, it enables the backup/alternate
1235 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001237 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1238 the "Enable 0" bit of the configuration register.
1239 Format: 0 | 1
1240 Default: 0
1241 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1242 the "Enable 0" bit of the configuration register.
1243 Format: 0 | 1
1244 Default: 0
1245 grcan.select= [HW] Select which physical interface to use.
1246 Format: 0 | 1
1247 Default: 0
1248 grcan.txsize= [HW] Sets the size of the tx buffer.
1249 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1250 Default: 1024
1251 grcan.rxsize= [HW] Sets the size of the rx buffer.
1252 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1253 Default: 1024
1254
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 hashdist= [KNL,NUMA] Large hashes allocated during boot
1256 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001257 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001258 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259
1260 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1261
1262 hd= [EIDE] (E)IDE hard drive subsystem geometry
1263 Format: <cyl>,<head>,<sect>
1264
Huang Yingea8c0712010-05-18 14:35:15 +08001265 hest_disable [ACPI]
1266 Disable Hardware Error Source Table (HEST) support;
1267 corresponding firmware-first mode error processing
1268 logic will be disabled.
1269
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1271 size of <nn>. This works even on boxes that have no
1272 highmem otherwise. This also works to reduce highmem
1273 size on bigger boxes.
1274
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001275 highres= [KNL] Enable/disable high resolution timer mode.
1276 Valid parameters: "on", "off"
1277 Default: "on"
1278
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279 hisax= [HW,ISDN]
1280 See Documentation/isdn/README.HiSax.
1281
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001282 hlt [BUGS=ARM,SH]
1283
1284 hpet= [X86-32,HPET] option to control HPET usage
1285 Format: { enable (default) | disable | force |
1286 verbose }
1287 disable: disable HPET and use PIT instead
1288 force: allow force enabled of undocumented chips (ICH4,
1289 VIA, nVidia)
1290 verbose: show contents of HPET registers during setup
1291
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001292 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1293 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1294
Andi Kleenb4718e62008-07-23 21:27:51 -07001295 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1296 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001297 On x86-64 and powerpc, this option can be specified
1298 multiple times interleaved with hugepages= to reserve
1299 huge pages of different sizes. Valid pages sizes on
1300 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001301 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001302
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001303 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1304 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001305 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1306 If specified, z/VM IUCV HVC accepts connections
1307 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001308
James Hoganfdabf522012-10-09 11:00:27 +01001309 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1310 hardware thread id mappings.
1311 Format: <cpu>:<hwthread>
1312
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001313 keep_bootcon [KNL]
1314 Do not unregister boot console at start. This is only
1315 useful for debugging when something happens in the window
1316 between unregistering the boot console and initializing
1317 the real console.
1318
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001319 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001320 or register an additional I2C bus that is not
1321 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001322 Format:
1323 <bus_id>,<clkrate>
1324
Jiri Kosina36d95732008-10-06 02:51:09 -04001325 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001326 i8042.unmask_kbd_data
1327 [HW] Enable printing of interrupt data from the KBD port
1328 (disabled by default, and as a pre-condition
1329 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001331 i8042.dumbkbd [HW] Pretend that controller can only read data from
1332 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333 (Don't attempt to blink the leds)
1334 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001335 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001336 i8042.noloop [HW] Disable the AUX Loopback command while probing
1337 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001339 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1341 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001342 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 i8042.reset [HW] Reset the controller during init and cleanup
1344 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001345 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346
1347 i810= [HW,DRM]
1348
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001349 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1350 indicates that the driver is running on unsupported
1351 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1353 does not match list of supported models.
1354 i8k.power_status
1355 [HW] Report power status in /proc/i8k
1356 (disabled by default)
1357 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1358 capability is set.
1359
Carsten Emde4dca20e2012-03-15 15:56:26 +01001360 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001361 [DRM] Invert the sense of the variable that is used to
1362 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001363 brightness value of 0 indicates backlight switched off,
1364 and the maximum of the brightness value sets the backlight
1365 to maximum brightness. If this parameter is set to 0
1366 (default) and the machine requires it, or this parameter
1367 is set to 1, a brightness value of 0 sets the backlight
1368 to maximum brightness, and the maximum of the brightness
1369 value switches the backlight off.
1370 -1 -- never invert brightness
1371 0 -- machine default
1372 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001373
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374 icn= [HW,ISDN]
1375 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1376
David Fries0af80c02009-02-25 20:28:21 +01001377 ide-core.nodma= [HW] (E)IDE subsystem
1378 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001379 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1380 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001381 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001383 ide-generic.probe-mask= [HW] (E)IDE subsystem
1384 Format: <int>
1385 Probe mask for legacy ISA IDE ports. Depending on
1386 platform up to 6 ports are supported, enabled by
1387 setting corresponding bits in the mask to 1. The
1388 default value is 0x0, which has a special meaning.
1389 On systems that have PCI, it triggers scanning the
1390 PCI bus for the first and the second port, which
1391 are then probed. On systems without PCI the value
1392 of 0x0 enables probing the two first ports as if it
1393 was 0x3.
1394
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001395 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1396 Claim all unknown PCI IDE storage controllers.
1397
Andi Kleenf039b752007-05-02 19:27:12 +02001398 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001399 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001400 Poll forces a polling idle loop that can slightly
1401 improve the performance of waking up a idle CPU, but
1402 will use a lot of power and make the system run hot.
1403 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001404 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001405 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001406 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001407
Ingo Molnar792908222006-12-06 20:40:51 -08001408 ignore_loglevel [KNL]
1409 Ignore loglevel setting - this will print /all/
1410 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001411 We also add it as printk module parameter, so users
1412 could change it dynamically, usually by
1413 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001414
Linus Torvalds1da177e2005-04-16 15:20:36 -07001415 ihash_entries= [KNL]
1416 Set number of hash buckets for inode cache.
1417
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001418 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001419 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001420 default: "enforce"
1421
Mimi Zohar07f6a792011-03-09 22:25:48 -05001422 ima_appraise_tcb [IMA]
1423 The builtin appraise policy appraises all files
1424 owned by uid=0.
1425
Mimi Zohar3323eec92009-02-04 09:06:58 -05001426 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001427 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1428 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001429 default: "sha1"
1430
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001431 The list of supported hash algorithms is defined
1432 in crypto/hash_info.h.
1433
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001434 ima_policy= [IMA]
1435 The builtin measurement policy to load during IMA
1436 setup. Specyfing "tcb" as the value, measures all
1437 programs exec'd, files mmap'd for exec, and all files
1438 opened with the read mode bit set by either the
1439 effective uid (euid=0) or uid=0.
1440 Format: "tcb"
1441
1442 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001443 Load a policy which meets the needs of the Trusted
1444 Computing Base. This means IMA will measure all
1445 programs exec'd, files mmap'd for exec, and all files
1446 opened for read by uid=0.
1447
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001448 ima_template= [IMA]
1449 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001450 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001451 Default: "ima-ng"
1452
Roberto Sassuc2426d22014-10-13 14:08:42 +02001453 ima_template_fmt=
1454 [IMA] Define a custom template format.
1455 Format: { "field1|...|fieldN" }
1456
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001457 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1458 Format: <min_file_size>
1459 Set the minimal file size for using asynchronous hash.
1460 If left unspecified, ahash usage is disabled.
1461
1462 ahash performance varies for different data sizes on
1463 different crypto accelerators. This option can be used
1464 to achieve the best performance for a particular HW.
1465
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001466 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1467 Format: <bufsize>
1468 Set hashing buffer size. Default: 4k.
1469
1470 ahash performance varies for different chunk sizes on
1471 different crypto accelerators. This option can be used
1472 to achieve best performance for particular HW.
1473
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474 init= [KNL]
1475 Format: <full_path>
1476 Run specified binary instead of /sbin/init as init
1477 process.
1478
1479 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1480 for working out where the kernel is dying during
1481 startup.
1482
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001483 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1484 initcall functions. Useful for debugging built-in
1485 modules and initcalls.
1486
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487 initrd= [BOOT] Specify the location of the initial ramdisk
1488
1489 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1490 Format: <irq>
1491
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001492 int_pln_enable [x86] Enable power limit notification interrupt
1493
Mimi Zohard726d8d2013-03-18 14:48:02 -04001494 integrity_audit=[IMA]
1495 Format: { "0" | "1" }
1496 0 -- basic integrity auditing messages. (Default)
1497 1 -- additional integrity auditing messages.
1498
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001499 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001500 on
1501 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001502 off
1503 Disable intel iommu driver.
1504 igfx_off [Default Off]
1505 By default, gfx is mapped as normal device. If a gfx
1506 device has a dedicated DMAR unit, the DMAR unit is
1507 bypassed by not enabling DMAR with this option. In
1508 this case, gfx device will use physical address for
1509 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001510 forcedac [x86_64]
1511 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001512 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001513 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001514 than 32-bit addressing. The default is to look
1515 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001516 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001517 strict [Default Off]
1518 With this option on every unmap_single operation will
1519 result in a hardware IOTLB flush operation as opposed
1520 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001521 sp_off [Default Off]
1522 By default, super page will be supported if Intel IOMMU
1523 has the capability. With this option, super page will
1524 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001525 ecs_off [Default Off]
1526 By default, extended context tables will be supported if
1527 the hardware advertises that it has support both for the
1528 extended tables themselves, and also PASID support. With
1529 this option set, extended tables will not be used even
1530 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001531
1532 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1533 0 disables intel_idle and fall back on acpi_idle.
1534 1 to 6 specify maximum depth of C-state.
1535
Dirk Brandewie6be26492013-02-15 22:55:10 +01001536 intel_pstate= [X86]
1537 disable
1538 Do not enable intel_pstate as the default
1539 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001540 force
1541 Enable intel_pstate on systems that prohibit it by default
1542 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1543 instead of acpi-cpufreq may disable platform features, such
1544 as thermal controls and power capping, that rely on ACPI
1545 P-States information being indicated to OSPM and therefore
1546 should be used with caution. This option does not work with
1547 processors that aren't supported by the intel_pstate driver
1548 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001549 no_hwp
1550 Do not enable hardware P state control (HWP)
1551 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001552 hwp_only
1553 Only load intel_pstate on systems which support
1554 hardware P state control (HWP) if available.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001555
Chris Wrightd1423d52010-07-20 11:06:49 -07001556 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001557 on enable Interrupt Remapping (default)
1558 off disable Interrupt Remapping
1559 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001560 no_x2apic_optout
1561 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001562
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001563 iomem= Disable strict checking of access to MMIO memory
1564 strict regions from userspace.
1565 relaxed
1566
1567 iommu= [x86]
1568 off
1569 force
1570 noforce
1571 biomerge
1572 panic
1573 nopanic
1574 merge
1575 nomerge
1576 forcesac
1577 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001578 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001579 nobypass [PPC/POWERNV]
1580 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001581
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001582
1583 io7= [HW] IO7 for Marvel based alpha systems
1584 See comment before marvel_specify_io7 in
1585 arch/alpha/kernel/core_marvel.c.
1586
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301587 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001588 0x80
1589 Standard port 0x80 based delay
1590 0xed
1591 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001592 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001593 Simple two microseconds delay
1594 none
1595 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001596
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001598 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599
Alan Cox200803d2005-06-28 20:45:18 -07001600 irqfixup [HW]
1601 When an interrupt is not handled search all handlers
1602 for it. Intended to get systems with badly broken
1603 firmware running.
1604
1605 irqpoll [HW]
1606 When an interrupt is not handled search all handlers
1607 for it. Also check all handlers each timer
1608 interrupt. Intended to get systems with badly broken
1609 firmware running.
1610
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001612 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613
1614 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001615 Format:
1616 <cpu number>,...,<cpu number>
1617 or
Li Zefanb225d442008-11-06 12:53:39 -08001618 <cpu number>-<cpu number>
1619 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001620 or a mixture
1621 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001622
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 This option can be used to specify one or more CPUs
1624 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001625 algorithms. You can move a process onto or off an
1626 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 <cpu number> begins at 0 and the maximum value is
1628 "number of CPUs in system - 1".
1629
1630 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001631 alternative -- manually setting the CPU mask of all
1632 tasks in the system -- can cause problems and
1633 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634
Randy Dunlapa9913042005-10-23 12:57:11 -07001635 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001637 ivrs_ioapic [HW,X86_64]
1638 Provide an override to the IOAPIC-ID<->DEVICE-ID
1639 mapping provided in the IVRS ACPI table. For
1640 example, to map IOAPIC-ID decimal 10 to
1641 PCI device 00:14.0 write the parameter as:
1642 ivrs_ioapic[10]=00:14.0
1643
1644 ivrs_hpet [HW,X86_64]
1645 Provide an override to the HPET-ID<->DEVICE-ID
1646 mapping provided in the IVRS ACPI table. For
1647 example, to map HPET-ID decimal 0 to
1648 PCI device 00:14.0 write the parameter as:
1649 ivrs_hpet[0]=00:14.0
1650
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651 js= [HW,JOY] Analog joystick
1652 See Documentation/input/joystick.txt.
1653
Kees Cook24f2e022014-06-13 13:30:36 -07001654 kaslr/nokaslr [X86]
1655 Enable/disable kernel and module base offset ASLR
1656 (Address Space Layout Randomization) if built into
1657 the kernel. When CONFIG_HIBERNATION is selected,
1658 kASLR is disabled by default. When kASLR is enabled,
1659 hibernation will be disabled.
1660
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001661 keepinitrd [HW,ARM]
1662
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301663 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001664 specifies the amount of memory usable by the kernel
1665 for non-movable allocations. The requested amount is
1666 spread evenly throughout all nodes in the system. The
1667 remaining memory in each node is used for Movable
1668 pages. In the event, a node is too small to have both
1669 kernelcore and Movable pages, kernelcore pages will
1670 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001671 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001672 allocation of pages that may be reclaimed or moved
1673 by the page migration subsystem. This means that
1674 HugeTLB pages may not be allocated from this zone.
1675 Note that allocations like PTEs-from-HighMem still
1676 use the HighMem zone if it exists, and the Normal
1677 zone if it does not.
1678
Jason Wessel4fe1da42010-05-20 21:04:31 -05001679 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1680 Format: <Controller#>[,poll interval]
1681 The controller # is the number of the ehci usb debug
1682 port as it is probed via PCI. The poll interval is
1683 optional and is the number seconds in between
1684 each poll cycle to the debug port in case you need
1685 the functionality for interrupting the kernel with
1686 gdb or control-c on the dbgp connection. When
1687 not using this parameter you use sysrq-g to break into
1688 the kernel debugger.
1689
Jason Wessel84c08fd2010-05-20 21:04:24 -05001690 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001691 Requires a tty driver that supports console polling,
1692 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001693 Serial only format: <serial_device>[,baud]
1694 keyboard only format: kbd
1695 keyboard and serial format: kbd,<serial_device>[,baud]
1696 Optional Kernel mode setting:
1697 kms, kbd format: kms,kbd
1698 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001699
Jason Wessel84c08fd2010-05-20 21:04:24 -05001700 kgdbwait [KGDB] Stop kernel execution and enter the
1701 kernel debugger at the earliest opportunity.
1702
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001703 kmac= [MIPS] korina ethernet MAC address.
1704 Configure the RouterBoard 532 series on-chip
1705 Ethernet adapter MAC address.
1706
Catalin Marinas04f70332009-06-11 13:22:39 +01001707 kmemleak= [KNL] Boot-time kmemleak enable/disable
1708 Valid arguments: on, off
1709 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001710 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1711 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001712
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001713 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1714 Valid arguments: 0, 1, 2
1715 kmemcheck=0 (disabled)
1716 kmemcheck=1 (enabled)
1717 kmemcheck=2 (one-shot mode)
1718 Default: 2 (one-shot mode)
1719
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301720 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001721 in oops dumps.
1722
Andre Przywarafef07aa2009-07-10 14:20:35 +02001723 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1724 Default is 0 (don't ignore, but inject #GP)
1725
Xiao Guangronga182d872010-09-20 22:17:48 +08001726 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1727 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001728 Default is 0 (off)
1729
Andre Przywarafef07aa2009-07-10 14:20:35 +02001730 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001731 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001732
1733 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1734 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001735 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001736
Andre Przywarafef07aa2009-07-10 14:20:35 +02001737 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1738 (virtualized MMU) support on capable Intel chips.
1739 Default is 1 (enabled)
1740
1741 kvm-intel.emulate_invalid_guest_state=
1742 [KVM,Intel] Enable emulation of invalid guest states
1743 Default is 0 (disabled)
1744
1745 kvm-intel.flexpriority=
1746 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1747 Default is 1 (enabled)
1748
Sasha Levine1a72ae2011-08-09 14:28:35 +03001749 kvm-intel.nested=
1750 [KVM,Intel] Enable VMX nesting (nVMX).
1751 Default is 0 (disabled)
1752
Andre Przywarafef07aa2009-07-10 14:20:35 +02001753 kvm-intel.unrestricted_guest=
1754 [KVM,Intel] Disable unrestricted guest feature
1755 (virtualized real and unpaged mode) on capable
1756 Intel chips. Default is 1 (enabled)
1757
1758 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1759 feature (tagged TLBs) on capable Intel chips.
1760 Default is 1 (enabled)
1761
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 l2cr= [PPC]
1763
Robert Brosea78bfbf2008-03-29 07:20:23 +11001764 l3cr= [PPC]
1765
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001766 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001767 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001768
Suresh Siddha279f1462012-10-22 14:37:58 -07001769 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1770 value for LAPIC timer one-shot implementation. Default
1771 back to the programmable timer unit in the LAPIC.
1772
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301773 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001774 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001775
FD Camifcb71f62008-01-06 19:08:56 +01001776 libata.dma= [LIBATA] DMA control
1777 libata.dma=0 Disable all PATA and SATA DMA
1778 libata.dma=1 PATA and SATA Disk DMA only
1779 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001780 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001781 Combinations also work, so libata.dma=3 enables DMA
1782 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001783
Michael Prokop20308872009-08-06 00:14:10 +02001784 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1785 libata.ignore_hpa=0 keep BIOS limits (default)
1786 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001787
Dave Jones78e70c22007-09-27 11:50:13 -04001788 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1789 when set.
1790 Format: <int>
1791
Tejun Heo33267322008-02-13 09:15:09 +09001792 libata.force= [LIBATA] Force configurations. The format is comma
1793 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001794 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001795 matching port, link or device. Basically, it matches
1796 the ATA ID string printed on console by libata. If
1797 the whole ID part is omitted, the last PORT and DEVICE
1798 values are used. If ID hasn't been specified yet, the
1799 configuration applies to all ports, links and devices.
1800
1801 If only DEVICE is omitted, the parameter applies to
1802 the port and all links and devices behind it. DEVICE
1803 number of 0 either selects the first device or the
1804 first fan-out link behind PMP device. It does not
1805 select the host link. DEVICE number of 15 selects the
1806 host link and device attached to it.
1807
1808 The VAL specifies the configuration to force. As long
1809 as there's no ambiguity shortcut notation is allowed.
1810 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1811 The following configurations can be forced.
1812
1813 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1814 Any ID with matching PORT is used.
1815
1816 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1817
1818 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1819 udma[/][16,25,33,44,66,100,133] notation is also
1820 allowed.
1821
1822 * [no]ncq: Turn on or off NCQ.
1823
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001824 * [no]ncqtrim: Turn off queued DSM TRIM.
1825
Tejun Heo05944bd2008-08-13 20:19:09 +09001826 * nohrst, nosrst, norst: suppress hard, soft
1827 and both resets.
1828
Dan Williamsca6d43b2012-06-21 23:41:41 -07001829 * rstonce: only attempt one reset during
1830 hot-unplug link recovery
1831
Tejun Heo43c9c592010-05-23 12:59:11 +02001832 * dump_id: dump IDENTIFY data.
1833
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001834 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1835
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001836 * disable: Disable this device.
1837
Tejun Heo33267322008-02-13 09:15:09 +09001838 If there are multiple matching configurations changing
1839 the same attribute, the last one is used.
1840
Yinghai Lu95f72d12010-07-12 14:36:09 +10001841 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001842
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001844 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001846 lockd.nlm_grace_period=P [NFS] Assign grace period.
1847 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001849 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1850 Format: <integer>
1851
1852 lockd.nlm_timeout=T [NFS] Assign timeout value.
1853 Format: <integer>
1854
1855 lockd.nlm_udpport=M [NFS] Assign UDP port.
1856 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001858 locktorture.nreaders_stress= [KNL]
1859 Set the number of locking read-acquisition kthreads.
1860 Defaults to being automatically set based on the
1861 number of online CPUs.
1862
1863 locktorture.nwriters_stress= [KNL]
1864 Set the number of locking write-acquisition kthreads.
1865
1866 locktorture.onoff_holdoff= [KNL]
1867 Set time (s) after boot for CPU-hotplug testing.
1868
1869 locktorture.onoff_interval= [KNL]
1870 Set time (s) between CPU-hotplug operations, or
1871 zero to disable CPU-hotplug testing.
1872
1873 locktorture.shuffle_interval= [KNL]
1874 Set task-shuffle interval (jiffies). Shuffling
1875 tasks allows some CPUs to go into dyntick-idle
1876 mode during the locktorture test.
1877
1878 locktorture.shutdown_secs= [KNL]
1879 Set time (s) after boot system shutdown. This
1880 is useful for hands-off automated testing.
1881
1882 locktorture.stat_interval= [KNL]
1883 Time (s) between statistics printk()s.
1884
1885 locktorture.stutter= [KNL]
1886 Time (s) to stutter testing, for example,
1887 specifying five seconds causes the test to run for
1888 five seconds, wait for five seconds, and so on.
1889 This tests the locking primitive's ability to
1890 transition abruptly to and from idle.
1891
1892 locktorture.torture_runnable= [BOOT]
1893 Start locktorture running at boot time.
1894
1895 locktorture.torture_type= [KNL]
1896 Specify the locking implementation to test.
1897
1898 locktorture.verbose= [KNL]
1899 Enable additional printk() statements.
1900
Linus Torvalds1da177e2005-04-16 15:20:36 -07001901 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1902 Format: <irq>
1903
1904 loglevel= All Kernel Messages with a loglevel smaller than the
1905 console loglevel will be printed to the console. It can
1906 also be changed with klogd or other programs. The
1907 loglevels are defined as follows:
1908
1909 0 (KERN_EMERG) system is unusable
1910 1 (KERN_ALERT) action must be taken immediately
1911 2 (KERN_CRIT) critical conditions
1912 3 (KERN_ERR) error conditions
1913 4 (KERN_WARNING) warning conditions
1914 5 (KERN_NOTICE) normal but significant condition
1915 6 (KERN_INFO) informational
1916 7 (KERN_DEBUG) debug-level messages
1917
Randy Dunlapc756d082011-02-20 20:08:35 -08001918 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001919 in bytes. n must be a power of two and greater
1920 than the minimal size. The minimal size is defined
1921 by LOG_BUF_SHIFT kernel config parameter. There is
1922 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1923 that allows to increase the default size depending on
1924 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001925
Randy Dunlapaccaa242007-10-16 01:29:37 -07001926 logo.nologo [FB] Disables display of the built-in Linux logo.
1927 This may be used to provide more screen space for
1928 kernel log messages and is useful when debugging
1929 kernel boot problems.
1930
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931 lp=0 [LP] Specify parallel ports to use, e.g,
1932 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1933 lp=reset first parallel port). 'lp=0' disables the
1934 lp=auto printer driver. 'lp=reset' (which can be
1935 specified in addition to the ports) causes
1936 attached printers to be reset. Using
1937 lp=port1,port2,... specifies the parallel ports
1938 to associate lp devices with, starting with
1939 lp0. A port specification may be 'none' to skip
1940 that lp device, or a parport name such as
1941 'parport0'. Specifying 'lp=auto' instead of a
1942 port specification list means that device IDs
1943 from each port should be examined, to see if
1944 an IEEE 1284-compliant printer is attached; if
1945 so, the driver will manage that printer.
1946 See also header of drivers/char/lp.c.
1947
1948 lpj=n [KNL]
1949 Sets loops_per_jiffy to given constant, thus avoiding
1950 time-consuming boot-time autodetection (up to 250 ms per
1951 CPU). 0 enables autodetection (default). To determine
1952 the correct value for your kernel, boot with normal
1953 autodetection and see what value is printed. Note that
1954 on SMP systems the preset will be applied to all CPUs,
1955 which is likely to cause problems if your CPUs need
1956 significantly divergent settings. An incorrect value
1957 will cause delays in the kernel to be wrong, leading to
1958 unpredictable I/O errors and other breakage. Although
1959 unlikely, in the extreme case this might damage your
1960 hardware.
1961
1962 ltpc= [NET]
1963 Format: <io>,<irq>,<dma>
1964
Randy Dunlap16290242011-08-13 12:34:52 -07001965 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001966 (machvec) in a generic kernel.
1967 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001968
Wu Zhangjin3209e702009-07-02 23:27:12 +08001969 machtype= [Loongson] Share the same kernel image file between different
1970 yeeloong laptop.
1971 Example: machtype=lemote-yeeloong-2f-7inch
1972
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001973 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1974 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975
1976 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001977 should make use of. maxcpus=n : n >= 0 limits the
1978 kernel to using 'n' processors. n=0 is a special case,
1979 it is equivalent to "nosmp", which also disables
1980 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001981
Kay Sieversd134b002011-07-31 22:08:04 +02001982 max_loop= [LOOP] The number of loop block devices that get
1983 (loop.max_loop) unconditionally pre-created at init time. The default
1984 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1985 of statically allocating a predefined number, loop
1986 devices can be requested on-demand with the
1987 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001988
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001989 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990
Uwe Hermann71cced62008-10-20 09:32:21 -07001991 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001992
Linus Torvalds1da177e2005-04-16 15:20:36 -07001993 md= [HW] RAID subsystems devices and level
1994 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001995
Linus Torvalds1da177e2005-04-16 15:20:36 -07001996 mdacon= [MDA]
1997 Format: <first>,<last>
1998 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001999
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2001 Amount of memory to be used when the kernel is not able
2002 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002003 [X86] Work as limiting max address. Use together
2004 with memmap= to avoid physical address space collisions.
2005 Without memmap= PCI devices could be placed at addresses
2006 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002008 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002009 memory.
2010
Paul Mundt6902aa82008-09-21 17:14:42 +09002011 memchunk=nn[KMG]
2012 [KNL,SH] Allow user to override the default size for
2013 per-device physically contiguous DMA buffers.
2014
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302015 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002016 E820 memory map, as specified by the user.
2017 Such memmap=exactmap lines can be constructed based on
2018 BIOS output or other requirements. See the memmap=nn@ss
2019 option description.
2020
2021 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002022 [KNL] Force usage of a specific region of memory.
2023 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024
2025 memmap=nn[KMG]#ss[KMG]
2026 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002027 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028
2029 memmap=nn[KMG]$ss[KMG]
2030 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002031 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002032 Example: Exclude memory from 0x18690000-0x1869ffff
2033 memmap=64K$0x18690000
2034 or
2035 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002036
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002037 memmap=nn[KMG]!ss[KMG]
2038 [KNL,X86] Mark specific memory as protected.
2039 Region of memory to be used, from ss to ss+nn.
2040 The memory region may be marked as e820 type 12 (0xc)
2041 and is NVDIMM or ADR memory.
2042
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002043 memory_corruption_check=0/1 [X86]
2044 Some BIOSes seem to corrupt the first 64k of
2045 memory when doing things like suspend/resume.
2046 Setting this option will scan the memory
2047 looking for corruption. Enabling this will
2048 both detect corruption and prevent the kernel
2049 from using the memory being corrupted.
2050 However, its intended as a diagnostic tool; if
2051 repeatable BIOS-originated corruption always
2052 affects the same memory, you can use memmap=
2053 to prevent the kernel from using that memory.
2054
2055 memory_corruption_check_size=size [X86]
2056 By default it checks for corruption in the low
2057 64k, making this memory unavailable for normal
2058 use. Use this parameter to scan for
2059 corruption in more or less memory.
2060
2061 memory_corruption_check_period=seconds [X86]
2062 By default it checks for corruption every 60
2063 seconds. Use this parameter to check at some
2064 other rate. 0 disables periodic checking.
2065
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002066 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002067 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002068 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002069 Specifies the number of memtest passes to be
2070 performed. Each pass selects another test
2071 pattern from a given set of patterns. Memtest
2072 fills the memory with this pattern, validates
2073 memory contents and reserves bad memory
2074 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002075
Linus Torvalds1da177e2005-04-16 15:20:36 -07002076 meye.*= [HW] Set MotionEye Camera parameters
2077 See Documentation/video4linux/meye.txt.
2078
Andres Salomon8f368812007-10-12 23:04:06 +02002079 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2080 Multi-Function General Purpose Timers on AMD Geode
2081 platforms.
2082
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002083 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2084 the BIOS has incorrectly applied a workaround. TinyBIOS
2085 version 0.98 is known to be affected, 0.99 fixes the
2086 problem by letting the user disable the workaround.
2087
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088 mga= [HW,DRM]
2089
Randy Dunlap1c207f92008-11-19 15:36:16 -08002090 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2091 physical address is ignored.
2092
Michel Pollet39f45d72009-05-20 11:10:31 +01002093 mini2440= [ARM,HW,KNL]
2094 Format:[0..2][b][c][t]
2095 Default: "0tb"
2096 MINI2440 configuration specification:
2097 0 - The attached screen is the 3.5" TFT
2098 1 - The attached screen is the 7" TFT
2099 2 - The VGA Shield is attached (1024x768)
2100 Leaving out the screen size parameter will not load
2101 the TFT driver, and the framebuffer will be left
2102 unconfigured.
2103 b - Enable backlight. The TFT backlight pin will be
2104 linked to the kernel VESA blanking code and a GPIO
2105 LED. This parameter is not necessary when using the
2106 VGA shield.
2107 c - Enable the s3c camera interface.
2108 t - Reserved for enabling touchscreen support. The
2109 touchscreen support is not enabled in the mainstream
2110 kernel as of 2.6.30, a preliminary port can be found
2111 in the "bleeding edge" mini2440 support kernel at
2112 http://repo.or.cz/w/linux-2.6/mini2440.git
2113
Mel Gorman6b74ab92008-07-23 21:26:49 -07002114 mminit_loglevel=
2115 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2116 parameter allows control of the logging verbosity for
2117 the additional memory initialisation checks. A value
2118 of 0 disables mminit logging and a level of 4 will
2119 log everything. Information is printed at KERN_DEBUG
2120 so loglevel=8 may also need to be specified.
2121
Rusty Russell106a4ee2012-09-26 10:09:40 +01002122 module.sig_enforce
2123 [KNL] When CONFIG_MODULE_SIG is set, this means that
2124 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002125 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002126 is always true, so this option does nothing.
2127
Linus Torvalds1da177e2005-04-16 15:20:36 -07002128 mousedev.tap_time=
2129 [MOUSE] Maximum time between finger touching and
2130 leaving touchpad surface for touch to be considered
2131 a tap and be reported as a left button click (for
2132 touchpads working in absolute mode only).
2133 Format: <msecs>
2134 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2135 reporting absolute coordinates, such as tablets
2136 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2137 reporting absolute coordinates, such as tablets
2138
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302139 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002140 is similar to kernelcore except it specifies the
2141 amount of memory used for migratable allocations.
2142 If both kernelcore and movablecore is specified,
2143 then kernelcore will be at *least* the specified
2144 value but may be more. If movablecore on its own
2145 is specified, the administrator must be careful
2146 that the amount of memory usable for all allocations
2147 is not too small.
2148
Tang Chenc5320922013-11-12 15:08:10 -08002149 movable_node [KNL,X86] Boot-time switch to enable the effects
2150 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2151
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 MTD_Partition= [MTD]
2153 Format: <name>,<region-number>,<size>,<offset>
2154
Randy Dunlapa9913042005-10-23 12:57:11 -07002155 MTD_Region= [MTD] Format:
2156 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002157
2158 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002159 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002161 multitce=off [PPC] This parameter disables the use of the pSeries
2162 firmware feature for updating multiple TCE entries
2163 at a time.
2164
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002165 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2166
2167 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2168
2169 boundary - index of last SLC block on Flex-OneNAND.
2170 The remaining blocks are configured as MLC blocks.
2171 lock - Configure if Flex-OneNAND boundary should be locked.
2172 Once locked, the boundary cannot be changed.
2173 1 indicates lock status, 0 indicates unlock status.
2174
Ben Dooks9db829f2008-07-03 11:24:29 +01002175 mtdset= [ARM]
2176 ARM/S3C2412 JIVE boot control
2177
2178 See arch/arm/mach-s3c2412/mach-jive.c
2179
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002181 [HW] Make the MicroTouch USB driver use raw coordinates
2182 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002183
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002184 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002185 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002186 that could hold holes aka. UC entries.
2187
2188 mtrr_gran_size=nn[KMG] [X86]
2189 Used for mtrr cleanup. It is granularity of mtrr block.
2190 Default is 1.
2191 Large value could prevent small alignment from
2192 using up MTRRs.
2193
2194 mtrr_spare_reg_nr=n [X86]
2195 Format: <integer>
2196 Range: 0,7 : spare reg number
2197 Default : 1
2198 Used for mtrr cleanup. It is spare mtrr entries number.
2199 Set to 2 or more if your graphical card needs more.
2200
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2202
Linus Torvalds1da177e2005-04-16 15:20:36 -07002203 netdev= [NET] Network devices parameters
2204 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2205 Note that mem_start is often overloaded to mean
2206 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002207 This usage is only documented in each driver source
2208 file if at all.
2209
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002210 nf_conntrack.acct=
2211 [NETFILTER] Enable connection tracking flow accounting
2212 0 to disable accounting
2213 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002214 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002215
Chuck Lever306a0752010-09-17 10:54:37 -04002216 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002217 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002218
2219 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002220 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002221
Chuck Lever306a0752010-09-17 10:54:37 -04002222 nfsrootdebug [NFS] enable nfsroot debugging messages.
2223 See Documentation/filesystems/nfs/nfsroot.txt.
2224
Trond Myklebusta72b4422006-01-03 09:55:41 +01002225 nfs.callback_tcpport=
2226 [NFS] set the TCP port on which the NFSv4 callback
2227 channel should listen.
2228
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002229 nfs.cache_getent=
2230 [NFS] sets the pathname to the program which is used
2231 to update the NFS client cache entries.
2232
2233 nfs.cache_getent_timeout=
2234 [NFS] sets the timeout after which an attempt to
2235 update a cache entry is deemed to have failed.
2236
Trond Myklebust58df0952006-01-03 09:55:57 +01002237 nfs.idmap_cache_timeout=
2238 [NFS] set the maximum lifetime for idmapper cache
2239 entries.
2240
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002241 nfs.enable_ino64=
2242 [NFS] enable 64-bit inode numbers.
2243 If zero, the NFS client will fake up a 32-bit inode
2244 number for the readdir() and stat() syscalls instead
2245 of returning the full 64-bit number.
2246 The default is to return 64-bit inode numbers.
2247
Trond Myklebustef159e92012-02-06 19:50:40 -05002248 nfs.max_session_slots=
2249 [NFSv4.1] Sets the maximum number of session slots
2250 the client will attempt to negotiate with the server.
2251 This limits the number of simultaneous RPC requests
2252 that the client can send to the NFSv4.1 server.
2253 Note that there is little point in setting this
2254 value higher than the max_tcp_slot_table_limit.
2255
Trond Myklebustb064eca22011-02-22 15:44:32 -08002256 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002257 [NFSv4] When set to the default of '1', this option
2258 ensures that both the RPC level authentication
2259 scheme and the NFS level operations agree to use
2260 numeric uids/gids if the mount is using the
2261 'sec=sys' security flavour. In effect it is
2262 disabling idmapping, which can make migration from
2263 legacy NFSv2/v3 systems to NFSv4 easier.
2264 Servers that do not support this mode of operation
2265 will be autodetected by the client, and it will fall
2266 back to using the idmapper.
2267 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002268 nfs.nfs4_unique_id=
2269 [NFS4] Specify an additional fixed unique ident-
2270 ification string that NFSv4 clients can insert into
2271 their nfs_client_id4 string. This is typically a
2272 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002273
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002274 nfs.send_implementation_id =
2275 [NFSv4.1] Send client implementation identification
2276 information in exchange_id requests.
2277 If zero, no implementation identification information
2278 will be sent.
2279 The default is to send the implementation identification
2280 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002281
2282 nfs.recover_lost_locks =
2283 [NFSv4] Attempt to recover locks that were lost due
2284 to a lease timeout on the server. Please note that
2285 doing this risks data corruption, since there are
2286 no guarantees that the file will remain unchanged
2287 after the locks are lost.
2288 If you want to enable the kernel legacy behaviour of
2289 attempting to recover these locks, then set this
2290 parameter to '1'.
2291 The default parameter value of '0' causes the kernel
2292 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002293
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002294 nfs4.layoutstats_timer =
2295 [NFSv4.2] Change the rate at which the kernel sends
2296 layoutstats to the pNFS metadata server.
2297
2298 Setting this to value to 0 causes the kernel to use
2299 whatever value is the default set by the layout
2300 driver. A non-zero value sets the minimum interval
2301 in seconds between layoutstats transmissions.
2302
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002303 nfsd.nfs4_disable_idmapping=
2304 [NFSv4] When set to the default of '1', the NFSv4
2305 server will return only numeric uids and gids to
2306 clients using auth_sys, and will accept numeric uids
2307 and gids from such clients. This is intended to ease
2308 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002309
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002310 objlayoutdriver.osd_login_prog=
2311 [NFS] [OBJLAYOUT] sets the pathname to the program which
2312 is used to automatically discover and login into new
2313 osd-targets. Please see:
2314 Documentation/filesystems/pnfs.txt for more explanations
2315
Paul Mundt1e1030d2009-09-01 17:38:32 +09002316 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002317 when a NMI is triggered.
2318 Format: [state][,regs][,debounce][,die]
2319
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302320 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002321 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002322 Valid num: 0 or 1
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002323 0 - turn nmi_watchdog off
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002324 1 - turn nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002325 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002326 timeout occurs (or 'nopanic' to override the opposite
2327 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002328 This is useful when you use a panic=... timeout and
2329 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002330
Anton Vorontsovbff38772009-07-08 11:10:56 -07002331 netpoll.carrier_timeout=
2332 [NET] Specifies amount of time (in seconds) that
2333 netpoll should wait for a carrier. By default netpoll
2334 waits 4 seconds.
2335
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002336 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002337 emulation library even if a 387 maths coprocessor
2338 is present.
2339
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002340 no_console_suspend
2341 [HW] Never suspend the console
2342 Disable suspending of consoles during suspend and
2343 hibernate operations. Once disabled, debugging
2344 messages can reach various consoles while the rest
2345 of the system is being put to sleep (ie, while
2346 debugging driver suspend/resume hooks). This may
2347 not work reliably with all consoles, but is known
2348 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002349 To facilitate more flexible debugging, we also add
2350 console_suspend, a printk module parameter to control
2351 it. Users could use console_suspend (usually
2352 /sys/module/printk/parameters/console_suspend) to
2353 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002354
Christoph Lameterc1aee212007-05-31 00:40:47 -07002355 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2356 caches in the slab allocator. Saves per-node memory,
2357 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002358
Randy Dunlapa9913042005-10-23 12:57:11 -07002359 noalign [KNL,ARM]
2360
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361 noapic [SMP,APIC] Tells the kernel to not make use of any
2362 IOAPICs that may be present in the system.
2363
Mike Galbraith5091faa2010-11-30 14:18:03 +01002364 noautogroup Disable scheduler automatic task group creation.
2365
Linus Torvalds1da177e2005-04-16 15:20:36 -07002366 nobats [PPC] Do not use BATs for mapping kernel lowmem
2367 on "Classic" PPC cores.
2368
2369 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002370
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002371 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2372
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002373 nodelayacct [KNL] Disable per-task delay accounting
2374
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2376
Paul Mundt6902aa82008-09-21 17:14:42 +09002377 nodsp [SH] Disable hardware DSP at boot time.
2378
Dave Youngb2e0a542014-08-14 17:15:26 +08002379 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002380
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381 noexec [IA-64]
2382
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302383 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002384 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002385 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002386 noexec=off: disable non-executable mappings
2387
H. Peter Anvin52b61792012-09-21 12:43:13 -07002388 nosmap [X86]
2389 Disable SMAP (Supervisor Mode Access Prevention)
2390 even if it is supported by processor.
2391
Fenghua Yude5397a2011-05-11 16:51:05 -07002392 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002393 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002394 even if it is supported by processor.
2395
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002396 noexec32 [X86-64]
2397 This affects only 32-bit executables.
2398 noexec32=on: enable non-executable mappings (default)
2399 read doesn't imply executable mappings
2400 noexec32=off: disable non-executable mappings
2401 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002403 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002404
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002405 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002406 register save and restore. The kernel will only save
2407 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002409 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2410
Suresh Siddha0c752a92009-05-22 12:17:45 -07002411 noxsave [BUGS=X86] Disables x86 extended register state save
2412 and restore using xsave. The kernel will fallback to
2413 enabling legacy floating-point and sse state.
2414
Fenghua Yub6f42a42014-05-29 11:12:31 -07002415 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2416 register states. The kernel will fall back to use
2417 xsave to save the states. By using this parameter,
2418 performance of saving the states is degraded because
2419 xsave doesn't support modified optimization while
2420 xsaveopt supports it on xsaveopt enabled systems.
2421
2422 noxsaves [X86] Disables xsaves and xrstors used in saving and
2423 restoring x86 extended register state in compacted
2424 form of xsave area. The kernel will fall back to use
2425 xsaveopt and xrstor to save and restore the states
2426 in standard form of xsave area. By using this
2427 parameter, xsave area per process might occupy more
2428 memory on xsaves enabled systems.
2429
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002430 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2431 wfi(ARM) instruction doesn't work correctly and not to
2432 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002433
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002434 no_file_caps Tells the kernel not to honor file capabilities. The
2435 only way then for a file to be executed with privilege
2436 is to be setuid root or executed by root.
2437
Linus Torvalds1da177e2005-04-16 15:20:36 -07002438 nohalt [IA-64] Tells the kernel not to use the power saving
2439 function PAL_HALT_LIGHT when idle. This increases
2440 power-consumption. On the positive side, it reduces
2441 interrupt wake-up latency, which may improve performance
2442 in certain environments such as networked servers or
2443 real-time systems.
2444
Kees Cooka6e15a32014-06-13 13:30:35 -07002445 nohibernate [HIBERNATION] Disable hibernation and resume.
2446
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002447 nohz= [KNL] Boottime enable/disable dynamic ticks
2448 Valid arguments: on, off
2449 Default: on
2450
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002451 nohz_full= [KNL,BOOT]
2452 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002453 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002454 whenever possible. The boot CPU will be forced outside
2455 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002456 The CPUs in this range must also be included in the
2457 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002458
Paul Mundteeee7852009-04-02 12:31:16 +09002459 noiotrap [SH] Disables trapped I/O port accesses.
2460
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002461 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002462 disable unhandled interrupt sources.
2463
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302464 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002465 broken timer IRQ sources.
2466
Linus Torvalds1da177e2005-04-16 15:20:36 -07002467 noisapnp [ISAPNP] Disables ISA PnP code.
2468
2469 noinitrd [RAM] Tells the kernel not to load any configured
2470 initial RAM disk.
2471
Weidong Han03ea8152009-04-17 16:42:15 +08002472 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2473 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002474 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002475
Linus Torvalds1da177e2005-04-16 15:20:36 -07002476 nointroute [IA-64]
2477
Randy Dunlap16290242011-08-13 12:34:52 -07002478 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002479
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002480 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2481
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002482 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2483 fault handling.
2484
Glauber Costad910f5c2011-07-11 15:28:19 -04002485 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2486 steal time is computed, but won't influence scheduler
2487 behaviour
2488
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002489 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002491 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002492
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 noltlbs [PPC] Do not use large page/tlb entries for kernel
2494 lowmem mapping on PPC40x.
2495
Horms312f1f02006-02-22 09:57:55 +09002496 nomca [IA-64] Disable machine check abort handling
2497
Masanari Iida13696e02015-05-16 02:16:43 +09002498 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002499
Andres Salomon83d73842007-10-12 23:04:06 +02002500 nomfgpt [X86-32] Disable Multi-Function General Purpose
2501 Timer usage (for AMD Geode machines).
2502
Don Zickusbda62632011-10-13 15:14:27 -04002503 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2504 shutdown the other cpus. Instead use the REBOOT_VECTOR
2505 irq.
2506
Dave Young02608be2012-02-01 10:33:14 +08002507 nomodule Disable module load
2508
Jiri Kosina016ddd92010-01-18 17:05:40 +01002509 nopat [X86] Disable PAT (page attribute table extension of
2510 pagetables) support.
2511
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002512 norandmaps Don't use address space randomization. Equivalent to
2513 echo 0 > /proc/sys/kernel/randomize_va_space
2514
Jiri Kosinabbff2162010-08-11 18:34:09 +02002515 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002516
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002517 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002518 with UP alternatives
2519
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002520 nordrand [X86] Disable kernel use of the RDRAND and
2521 RDSEED instructions even if they are supported
2522 by the processor. RDRAND and RDSEED are still
2523 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002524
Randy Dunlapa9913042005-10-23 12:57:11 -07002525 noresume [SWSUSP] Disables resume and restores original swap
2526 space.
2527
Linus Torvalds1da177e2005-04-16 15:20:36 -07002528 no-scroll [VGA] Disables scrollback.
2529 This is required for the Braillex ib80-piezo Braille
2530 reader made by F.H. Papenmeier (Germany).
2531
2532 nosbagart [IA-64]
2533
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002534 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002535
Len Brown61ec7562007-08-16 03:34:22 -04002536 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2537 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538
Dave Jones97842212007-07-15 23:41:05 -07002539 nosoftlockup [KNL] Disable the soft-lockup detector.
2540
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541 nosync [HW,M68K] Disables sync negotiation for all devices.
2542
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002543 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544
2545 nousb [USB] Disable the USB subsystem
2546
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002547 nowatchdog [KNL] Disable both lockup detectors, i.e.
2548 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002549
Linus Torvalds1da177e2005-04-16 15:20:36 -07002550 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002551
Weidong Han2b2fd872009-04-17 16:42:12 +08002552 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2553
Fenghua Yuf78cff42012-11-13 11:32:38 -08002554 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2555 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2556 Some features depend on CPU0. Known dependencies are:
2557 1. Resume from suspend/hibernate depends on CPU0.
2558 Suspend/hibernate will fail if CPU0 is offline and you
2559 need to online CPU0 before suspend/hibernate.
2560 2. PIC interrupts also depend on CPU0. CPU0 can't be
2561 removed if a PIC interrupt is detected.
2562 It's said poweroff/reboot may depend on CPU0 on some
2563 machines although I haven't seen such issues so far
2564 after CPU0 is offline on a few tested machines.
2565 If the dependencies are under your control, you can
2566 turn on cpu0_hotplug.
2567
Randy Dunlap16290242011-08-13 12:34:52 -07002568 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002569 purges which is reported from either PAL_VM_SUMMARY or
2570 SAL PALO.
2571
Yinghai Lu2b633e32010-02-10 01:20:37 -08002572 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2573 could support. nr_cpus=n : n >= 1 limits the kernel to
2574 supporting 'n' processors. Later in runtime you can not
2575 use hotplug cpu feature to put more cpu back to online.
2576 just like you compile the kernel NR_CPUS=n
2577
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002578 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2579
Mel Gorman1a687c22012-11-22 11:16:36 +00002580 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2581 Allowed values are enable and disable
2582
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002583 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2584 one of ['zone', 'node', 'default'] can be specified
2585 This can be set from sysctl after boot.
2586 See Documentation/sysctl/vm.txt for details.
2587
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002588 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2589 See Documentation/debugging-via-ohci1394.txt for more
2590 info.
2591
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002592 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2593 Rather than timing out after 20 ms if an EC
2594 command is not properly ACKed, override the length
2595 of the timeout. We have interrupts disabled while
2596 waiting for the ACK, so if this is set too high
2597 interrupts *may* be lost!
2598
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002599 omap_mux= [OMAP] Override bootloader pin multiplexing.
2600 Format: <mux_mode0.mode_name=value>...
2601 For example, to override I2C bus2:
2602 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2603
Linus Torvalds1da177e2005-04-16 15:20:36 -07002604 oprofile.timer= [HW]
2605 Use timer interrupt instead of performance counters
2606
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002607 oprofile.cpu_type= Force an oprofile cpu type
2608 This might be useful if you have an older oprofile
2609 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002610 Format: { arch_perfmon }
2611 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002612 perfmon on Intel CPUs instead of the
2613 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002614 timer: [X86] Force use of architectural NMI
2615 timer mode (see also oprofile.timer
2616 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002617 [s390] Force legacy basic mode sampling
2618 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002619
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002620 oops=panic Always panic on oopses. Default is to just kill the
2621 process, but there is a small probability of
2622 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002623 This will also cause panics on machine check exceptions.
2624 Useful together with panic=30 to trigger a reboot.
2625
Randy Dunlapbcfde332010-06-07 17:10:38 -07002626 OSS [HW,OSS]
2627 See Documentation/sound/oss/oss-parameters.txt
2628
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002629 page_owner= [KNL] Boot-time page_owner enabling option.
2630 Storage of the information about who allocated
2631 each page is disabled in default. With this switch,
2632 we can turn it on.
2633 on: enable the feature
2634
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002635 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002636 timeout > 0: seconds before rebooting
2637 timeout = 0: wait forever
2638 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002639 Format: <timeout>
2640
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002641 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2642 on a WARN().
2643
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002644 crash_kexec_post_notifiers
2645 Run kdump after running panic-notifiers and dumping
2646 kmsg. This only for the users who doubt kdump always
2647 succeeds in any situation.
2648 Note that this also increases risks of kdump failure,
2649 because some panic notifiers can make the crashed
2650 kernel more unstable.
2651
Linus Torvalds1da177e2005-04-16 15:20:36 -07002652 parkbd.port= [HW] Parallel port number the keyboard adapter is
2653 connected to, default is 0.
2654 Format: <parport#>
2655 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2656 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002657 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002658
Randy Dunlapa9913042005-10-23 12:57:11 -07002659 parport= [HW,PPT] Specify parallel ports. 0 disables.
2660 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2661 Use 'auto' to force the driver to use any
2662 IRQ/DMA settings detected (the default is to
2663 ignore detected IRQ/DMA settings because of
2664 possible conflicts). You can specify the base
2665 address, IRQ, and DMA settings; IRQ and DMA
2666 should be numbers, or 'auto' (for using detected
2667 settings on that particular port), or 'nofifo'
2668 (to avoid using a FIFO even if it is detected).
2669 Parallel ports are assigned in the order they
2670 are specified on the command line, starting
2671 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002672
Randy Dunlapa9913042005-10-23 12:57:11 -07002673 parport_init_mode= [HW,PPT]
2674 Configure VIA parallel port to operate in
2675 a specific mode. This is necessary on Pegasos
2676 computer where firmware has no options for setting
2677 up parallel port mode and sets it to spp.
2678 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002679 Format: [spp|ps2|epp|ecp|ecpepp]
2680
Andrew Mortondd287792006-03-23 03:00:57 -08002681 pause_on_oops=
2682 Halt all CPUs after the first oops has been printed for
2683 the specified number of seconds. This is to be used if
2684 your oopses keep scrolling off the screen.
2685
Linus Torvalds1da177e2005-04-16 15:20:36 -07002686 pcbit= [HW,ISDN]
2687
2688 pcd. [PARIDE]
2689 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002690 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002691
Randy Dunlapa9913042005-10-23 12:57:11 -07002692 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002693 earlydump [X86] dump PCI config space before the kernel
2694 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002695 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002696 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002697 the hardware directly. Use this if your machine
2698 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002699 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002700 hardware access methods are allowed. Use this
2701 if you experience crashes upon bootup and you
2702 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002703 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002704 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002705 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002706 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002707 noaer [PCIE] If the PCIEAER kernel config parameter is
2708 enabled, this kernel boot option can be used to
2709 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea72007-10-11 16:57:27 -04002710 nodomains [PCI] Disable support for multiple PCI
2711 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302712 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002713 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002714 check_enable_amd_mmconf [X86] check for and enable
2715 properly configured MMIO access to PCI
2716 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002717 nomsi [MSI] If the PCI_MSI kernel config parameter is
2718 enabled, this kernel boot option can be used to
2719 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002720 noioapicquirk [APIC] Disable all boot interrupt quirks.
2721 Safety option to keep boot IRQs enabled. This
2722 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002723 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2724 primary IO-APIC for bridges that cannot disable
2725 boot IRQs. This fixes a source of spurious IRQs
2726 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002727 noioapicreroute [APIC] Disable workaround that uses the
2728 boot IRQ equivalent of an IRQ that connects to
2729 a chipset where boot IRQs cannot be disabled.
2730 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002731 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002732 routing table. These calls are known to be buggy
2733 on several machines and they hang the machine
2734 when used, but on other computers it's the only
2735 way to get the interrupt routing table. Try
2736 this option if the kernel is unable to allocate
2737 IRQs or discover secondary PCI buses on your
2738 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002739 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002740 Use with caution as certain devices share
2741 address decoders between ROMs and other
2742 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002743 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002744 expansion ROMs that do not already have
2745 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002746 nobar [X86] Do not assign address space to the
2747 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002748 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002749 assigned automatically to PCI devices. You can
2750 make the kernel exclude IRQs of your ISA cards
2751 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002752 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002753 of the PIRQ table (normally generated
2754 by the BIOS) if it is outside the
2755 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002756 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002757 useful if the kernel is unable to find your
2758 secondary buses and you want to tell it
2759 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002760 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002761 numbers ourselves, overriding
2762 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002763 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002764 in the BIOS $PIR table. This is needed on
2765 some systems with broken BIOSes, notably
2766 some HP Pavilion N5400 and Omnibook XE3
2767 notebooks. This will have no effect if ACPI
2768 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002769 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002770 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002771 use_crs [X86] Use PCI host bridge window information
2772 from ACPI. On BIOSes from 2008 or later, this
2773 is enabled by default. If you need to use this,
2774 please report a bug.
2775 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2776 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002777 routeirq Do IRQ routing for all PCI devices.
2778 This is normally done in pci_enable_device(),
2779 so this option is a temporary workaround
2780 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002781 skip_isa_align [X86] do not align io start addr, so can
2782 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002783 firmware [ARM] Do not re-enumerate the bus but instead
2784 just use the configuration from the
2785 bootloader. This is currently used on
2786 IXP2000 systems where the bus has to be
2787 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002788 noearly [X86] Don't do any early type 1 scanning.
2789 This might help on some broken boards which
2790 machine check when some devices' config space
2791 is read. But various workarounds are disabled
2792 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002793 bfsort Sort PCI devices into breadth-first order.
2794 This sorting is done to get a device
2795 order compatible with older (<= 2.4) kernels.
2796 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002797 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2798 tuning and use the BIOS-configured MPS defaults.
2799 pcie_bus_safe Set every device's MPS to the largest value
2800 supported by all devices below the root complex.
2801 pcie_bus_perf Set device MPS to the largest allowable MPS
2802 based on its parent bus. Also set MRRS (Max
2803 Read Request Size) to the largest supported
2804 value (no larger than the MPS that the device
2805 or bus can support) for best performance.
2806 pcie_bus_peer2peer Set every device's MPS to 128B, which
2807 every device is guaranteed to support. This
2808 configuration allows peer-to-peer DMA between
2809 any pair of devices, possibly at the cost of
2810 reduced performance. This also guarantees
2811 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002812 cbiosize=nn[KMG] The fixed amount of bus space which is
2813 reserved for the CardBus bridge's IO window.
2814 The default value is 256 bytes.
2815 cbmemsize=nn[KMG] The fixed amount of bus space which is
2816 reserved for the CardBus bridge's memory
2817 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002818 resource_alignment=
2819 Format:
2820 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2821 Specifies alignment and device to reassign
2822 aligned memory resources.
2823 If <order of align> is not specified,
2824 PAGE_SIZE is used as alignment.
2825 PCI-PCI bridge can be specified, if resource
2826 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002827 ecrc= Enable/disable PCIe ECRC (transaction layer
2828 end-to-end CRC checking).
2829 bios: Use BIOS/firmware settings. This is the
2830 the default.
2831 off: Turn ECRC off
2832 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002833 hpiosize=nn[KMG] The fixed amount of bus space which is
2834 reserved for hotplug bridge's IO window.
2835 Default size is 256 bytes.
2836 hpmemsize=nn[KMG] The fixed amount of bus space which is
2837 reserved for hotplug bridge's memory window.
2838 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002839 realloc= Enable/disable reallocating PCI bridge resources
2840 if allocations done by BIOS are too small to
2841 accommodate resources required by all child
2842 devices.
2843 off: Turn realloc off
2844 on: Turn realloc on
2845 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002846 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002847 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2848 only look for one device below a PCIe downstream
2849 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002850
Chuck Ebberte5665a42008-09-24 20:40:34 -04002851 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2852 Management.
2853 off Disable ASPM.
2854 force Enable ASPM even on devices that claim not to support it.
2855 WARNING: Forcing ASPM on may cause system lockups.
2856
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002857 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2858 nomsi Do not use MSI for PCI Express Native Hotplug (this
2859 makes all PCIe ports use INTx for hotplug services).
2860
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002861 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002862 auto Ask the BIOS whether or not to use native PCIe services
2863 associated with PCIe ports (PME, hot-plug, AER). Use
2864 them only if that is allowed by the BIOS.
2865 native Use native PCIe services associated with PCIe ports
2866 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002867 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2868 ports driver.
2869
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002870 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002871 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002872 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002873
Linus Torvalds1da177e2005-04-16 15:20:36 -07002874 pcmv= [HW,PCMCIA] BadgePAD 4
2875
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302876 pd_ignore_unused
2877 [PM]
2878 Keep all power-domains already enabled by bootloader on,
2879 even if no driver has claimed them. This is useful
2880 for debug and development, but should not be
2881 needed on a platform with proper driver support.
2882
Linus Torvalds1da177e2005-04-16 15:20:36 -07002883 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002884 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002885
2886 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2887 boot time.
2888 Format: { 0 | 1 }
2889 See arch/parisc/kernel/pdc_chassis.c
2890
Tejun Heof58dc012009-08-14 15:00:50 +09002891 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002892 Currently supported values are "embed" and "page".
2893 Archs may support subset or none of the selections.
2894 See comments in mm/percpu.c for details on each
2895 allocator. This parameter is primarily for debugging
2896 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002897
Linus Torvalds1da177e2005-04-16 15:20:36 -07002898 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002899 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900
2901 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002902 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002903
2904 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002905 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002906
2907 plip= [PPT,NET] Parallel port network link
2908 Format: { parport<nr> | timid | 0 }
2909 See also Documentation/parport.txt.
2910
Randy Dunlap16290242011-08-13 12:34:52 -07002911 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002912 Override pmtimer IOPort with a hex value.
2913 e.g. pmtmr=0x508
2914
Bjorn Helgaas96242112011-08-11 12:14:05 -06002915 pnp.debug=1 [PNP]
2916 Enable PNP debug messages (depends on the
2917 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2918 via /sys/module/pnp/parameters/debug. We always show
2919 current resource usage; turning this on also shows
2920 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002921
Linus Torvalds1da177e2005-04-16 15:20:36 -07002922 pnpacpi= [ACPI]
2923 { off }
2924
2925 pnpbios= [ISAPNP]
2926 { on | off | curr | res | no-curr | no-res }
2927
2928 pnp_reserve_irq=
2929 [ISAPNP] Exclude IRQs for the autoconfiguration
2930
2931 pnp_reserve_dma=
2932 [ISAPNP] Exclude DMAs for the autoconfiguration
2933
2934 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002935 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002936
2937 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002938 [ISAPNP] Exclude memory regions for the
2939 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940 Ranges are in pairs (memory base and size).
2941
Randy Dunlap4af94f32009-04-17 18:30:28 -07002942 ports= [IP_VS_FTP] IPVS ftp helper module
2943 Default is 21.
2944 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2945 may be specified.
2946 Format: <port>,<port>....
2947
Ingo Molnar45807a12007-07-15 23:40:10 -07002948 print-fatal-signals=
2949 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002950
2951 If enabled, warn about various signal handling
2952 related application anomalies: too many signals,
2953 too many POSIX.1 timers, fatal signals causing a
2954 coredump - etc.
2955
2956 If you hit the warning due to signal overflow,
2957 you might want to try "ulimit -i unlimited".
2958
Ingo Molnar45807a12007-07-15 23:40:10 -07002959 default: off.
2960
Matthew Garrettc22ab332012-03-05 14:59:10 -08002961 printk.always_kmsg_dump=
2962 Trigger kmsg_dump for cases other than kernel oops or
2963 panics
2964 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2965 default: disabled
2966
Randy Dunlape84845c2007-07-15 23:40:25 -07002967 printk.time= Show timing data prefixed to each printk message line
2968 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2969
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002970 processor.max_cstate= [HW,ACPI]
2971 Limit processor to maximum C-state
2972 max_cstate=9 overrides any DMI blacklist limit.
2973
2974 processor.nocst [HW,ACPI]
2975 Ignore the _CST method to determine C-states,
2976 instead using the legacy FADT method
2977
Linus Torvalds1da177e2005-04-16 15:20:36 -07002978 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002979 Format: [schedule,]<number>
2980 Param: "schedule" - profile schedule points.
2981 Param: <number> - step/bucket size as a power of 2 for
2982 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002983 Param: "sleep" - profile D-state sleeping (millisecs).
2984 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002985 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002986
Linus Torvalds1da177e2005-04-16 15:20:36 -07002987 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2988 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002989 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002990
Randy Dunlapa9913042005-10-23 12:57:11 -07002991 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2992 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002993 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2994 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002995 psmouse.resetafter= [HW,MOUSE]
2996 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002997 (0 = never).
2998 psmouse.resolution=
2999 [HW,MOUSE] Set desired mouse resolution, in dpi.
3000 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003001 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002 0 = disabled, 1 = enabled (default).
3003
Matthew Garrettdee28e72011-07-21 16:57:55 -04003004 pstore.backend= Specify the name of the pstore backend to use
3005
Linus Torvalds1da177e2005-04-16 15:20:36 -07003006 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003007 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003008
Kay Sieversdc8c8582007-08-15 12:25:38 +02003009 pty.legacy_count=
3010 [KNL] Number of legacy pty's. Overwrites compiled-in
3011 default number.
3012
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003013 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003014
Linus Torvalds1da177e2005-04-16 15:20:36 -07003015 r128= [HW,DRM]
3016
3017 raid= [HW,RAID]
3018 See Documentation/md.txt.
3019
Randy Dunlapa9913042005-10-23 12:57:11 -07003020 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003021 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07003022
Linus Torvalds1da177e2005-04-16 15:20:36 -07003023 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003024 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003025
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003026 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003027 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3028 the specified list of CPUs to be no-callback CPUs.
3029 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003030 be offloaded to "rcuox/N" kthreads created for
3031 that purpose, where "x" is "b" for RCU-bh, "p"
3032 for RCU-preempt, and "s" for RCU-sched, and "N"
3033 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003034 offloaded CPUs, which can be useful for HPC and
3035 real-time workloads. It can also improve energy
3036 efficiency for asymmetric multiprocessors.
3037
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003038 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003039 Rather than requiring that offloaded CPUs
3040 (specified by rcu_nocbs= above) explicitly
3041 awaken the corresponding "rcuoN" kthreads,
3042 make these kthreads poll for callbacks.
3043 This improves the real-time response for the
3044 offloaded CPUs by relieving them of the need to
3045 wake up the corresponding kthread, but degrades
3046 energy efficiency by requiring that the kthreads
3047 periodically wake up to do the polling.
3048
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003049 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003050 Set maximum number of finished RCU callbacks to
3051 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003052
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003053 rcutree.dump_tree= [KNL]
3054 Dump the structure of the rcu_node combining tree
3055 out at early boot. This is used for diagnostic
3056 purposes, to verify correct tree setup.
3057
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003058 rcutree.gp_cleanup_delay= [KNL]
3059 Set the number of jiffies to delay each step of
3060 RCU grace-period cleanup. This only has effect
3061 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3062
Paul E. McKenney37745d22015-01-22 18:24:08 -08003063 rcutree.gp_init_delay= [KNL]
3064 Set the number of jiffies to delay each step of
3065 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003066 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3067 is set.
3068
3069 rcutree.gp_preinit_delay= [KNL]
3070 Set the number of jiffies to delay each step of
3071 RCU grace-period pre-initialization, that is,
3072 the propagation of recent CPU-hotplug changes up
3073 the rcu_node combining tree. This only has effect
3074 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003075
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003076 rcutree.rcu_fanout_exact= [KNL]
3077 Disable autobalancing of the rcu_node combining
3078 tree. This is used by rcutorture, and might
3079 possibly be useful for architectures having high
3080 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003081
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003082 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003083 Increase the number of CPUs assigned to each
3084 leaf rcu_node structure. Useful for very large
3085 systems.
3086
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003087 rcutree.jiffies_till_sched_qs= [KNL]
3088 Set required age in jiffies for a
3089 given grace period before RCU starts
3090 soliciting quiescent-state help from
3091 rcu_note_context_switch().
3092
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003093 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003094 Set delay from grace-period initialization to
3095 first attempt to force quiescent states.
3096 Units are jiffies, minimum value is zero,
3097 and maximum value is HZ.
3098
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003099 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003100 Set delay between subsequent attempts to force
3101 quiescent states. Units are jiffies, minimum
3102 value is one, and maximum value is HZ.
3103
Clark Williams21871d72014-09-12 21:21:09 -05003104 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003105 Set the SCHED_FIFO priority of the RCU per-CPU
3106 kthreads (rcuc/N). This value is also used for
3107 the priority of the RCU boost threads (rcub/N)
3108 and for the RCU grace-period kthreads (rcu_bh,
3109 rcu_preempt, and rcu_sched). If RCU_BOOST is
3110 set, valid values are 1-99 and the default is 1
3111 (the least-favored priority). Otherwise, when
3112 RCU_BOOST is not set, valid values are 0-99 and
3113 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003114
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003115 rcutree.rcu_nocb_leader_stride= [KNL]
3116 Set the number of NOCB kthread groups, which
3117 defaults to the square root of the number of
3118 CPUs. Larger numbers reduces the wakeup overhead
3119 on the per-CPU grace-period kthreads, but increases
3120 that same overhead on each group's leader.
3121
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003122 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003123 Set threshold of queued RCU callbacks beyond which
3124 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003125
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003126 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003127 Set threshold of queued RCU callbacks below which
3128 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003129
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003130 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003131 Set wakeup interval for idle CPUs that have
3132 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003133
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003134 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003135 Set wakeup interval for idle CPUs that have
3136 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3137 Lazy RCU callbacks are those which RCU can
3138 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003139
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003140 rcutorture.cbflood_inter_holdoff= [KNL]
3141 Set holdoff time (jiffies) between successive
3142 callback-flood tests.
3143
3144 rcutorture.cbflood_intra_holdoff= [KNL]
3145 Set holdoff time (jiffies) between successive
3146 bursts of callbacks within a given callback-flood
3147 test.
3148
3149 rcutorture.cbflood_n_burst= [KNL]
3150 Set the number of bursts making up a given
3151 callback-flood test. Set this to zero to
3152 disable callback-flood testing.
3153
3154 rcutorture.cbflood_n_per_burst= [KNL]
3155 Set the number of callbacks to be registered
3156 in a given burst of a callback-flood test.
3157
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003158 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003159 Set duration of force_quiescent_state bursts
3160 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003161
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003162 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003163 Set holdoff time within force_quiescent_state bursts
3164 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003165
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003166 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003167 Set wait time between force_quiescent_state bursts
3168 in seconds.
3169
3170 rcutorture.gp_cond= [KNL]
3171 Use conditional/asynchronous update-side
3172 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003173
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003174 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003175 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003176
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003177 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003178 Use normal (non-expedited) asynchronous
3179 update-side primitives, if available.
3180
3181 rcutorture.gp_sync= [KNL]
3182 Use normal (non-expedited) synchronous
3183 update-side primitives, if available. If all
3184 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3185 rcutorture.gp_normal=, and rcutorture.gp_sync=
3186 are zero, rcutorture acts as if is interpreted
3187 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003188
3189 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003190 Set callbacks/threads for rcu_barrier() testing.
3191
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003192 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003193 Set number of concurrent RCU writers. These just
3194 stress RCU, they don't participate in the actual
3195 test, hence the "fake".
3196
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003197 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003198 Set number of RCU readers. The value -1 selects
3199 N-1, where N is the number of CPUs. A value
3200 "n" less than -1 selects N-n-2, where N is again
3201 the number of CPUs. For example, -2 selects N
3202 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003203
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003204 rcutorture.object_debug= [KNL]
3205 Enable debug-object double-call_rcu() testing.
3206
3207 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003208 Set time (s) after boot for CPU-hotplug testing.
3209
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003210 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003211 Set time (s) between CPU-hotplug operations, or
3212 zero to disable CPU-hotplug testing.
3213
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003214 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003215 Set task-shuffle interval (s). Shuffling tasks
3216 allows some CPUs to go into dyntick-idle mode
3217 during the rcutorture test.
3218
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003219 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003220 Set time (s) after boot system shutdown. This
3221 is useful for hands-off automated testing.
3222
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003223 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003224 Duration of CPU stall (s) to test RCU CPU stall
3225 warnings, zero to disable.
3226
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003227 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003228 Time to wait (s) after boot before inducing stall.
3229
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003230 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003231 Time (s) between statistics printk()s.
3232
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003233 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003234 Time (s) to stutter testing, for example, specifying
3235 five seconds causes the test to run for five seconds,
3236 wait for five seconds, and so on. This tests RCU's
3237 ability to transition abruptly to and from idle.
3238
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003239 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003240 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3241 "Maybe" means test if the RCU implementation
3242 under test support RCU priority boosting.
3243
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003244 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003245 Duration (s) of each individual boost test.
3246
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003247 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003248 Interval (s) between each boost test.
3249
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003250 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003251 Test RCU's dyntick-idle handling. See also the
3252 rcutorture.shuffle_interval parameter.
3253
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003254 rcutorture.torture_runnable= [BOOT]
3255 Start rcutorture running at boot time.
3256
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003257 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003258 Specify the RCU implementation to test.
3259
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003260 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003261 Enable additional printk() statements.
3262
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003263 rcupdate.rcu_expedited= [KNL]
3264 Use expedited grace-period primitives, for
3265 example, synchronize_rcu_expedited() instead
3266 of synchronize_rcu(). This reduces latency,
3267 but can increase CPU utilization, degrade
3268 real-time latency, and degrade energy efficiency.
3269
3270 rcupdate.rcu_cpu_stall_suppress= [KNL]
3271 Suppress RCU CPU stall warning messages.
3272
3273 rcupdate.rcu_cpu_stall_timeout= [KNL]
3274 Set timeout for RCU CPU stall warning messages.
3275
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003276 rcupdate.rcu_task_stall_timeout= [KNL]
3277 Set timeout in jiffies for RCU task stall warning
3278 messages. Disable with a value less than or equal
3279 to zero.
3280
Pranith Kumar74860fe2014-09-19 11:34:09 -04003281 rcupdate.rcu_self_test= [KNL]
3282 Run the RCU early boot self tests
3283
3284 rcupdate.rcu_self_test_bh= [KNL]
3285 Run the RCU bh early boot self tests
3286
3287 rcupdate.rcu_self_test_sched= [KNL]
3288 Run the RCU sched early boot self tests
3289
Olof Johanssonffdfc402005-09-06 15:17:19 -07003290 rdinit= [KNL]
3291 Format: <full_path>
3292 Run specified binary instead of /init from the ramdisk,
3293 used for early userspace startup. See initrd.
3294
Robin Holt1b3a5d02013-07-08 16:01:42 -07003295 reboot= [KNL]
3296 Format (x86 or x86_64):
3297 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3298 [[,]s[mp]#### \
3299 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3300 [[,]f[orce]
3301 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3302 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3303 reboot_force is either force or not specified,
3304 reboot_cpu is s[mp]#### with #### being the processor
3305 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003306
Paul Jackson46b6d942008-07-04 10:00:09 -07003307 relax_domain_level=
3308 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003309 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003310
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003311 relative_sleep_states=
3312 [SUSPEND] Use sleep state labeling where the deepest
3313 state available other than hibernation is always "mem".
3314 Format: { "0" | "1" }
3315 0 -- Traditional sleep state labels.
3316 1 -- Relative sleep state labels.
3317
Linus Torvalds1da177e2005-04-16 15:20:36 -07003318 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3319
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003320 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07003321 Format: nn[KMG]
3322 Reserves a hole at the top of the kernel virtual
3323 address space.
3324
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003325 reservelow= [X86]
3326 Format: nn[K]
3327 Set the amount of memory to reserve for BIOS at
3328 the bottom of the address space.
3329
Vivek Goyal7e962872006-09-27 01:50:44 -07003330 reset_devices [KNL] Force drivers to reset the underlying device
3331 during initialization.
3332
Randy Dunlapa9913042005-10-23 12:57:11 -07003333 resume= [SWSUSP]
3334 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003335 Format:
3336 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003337
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003338 resume_offset= [SWSUSP]
3339 Specify the offset from the beginning of the partition
3340 given by "resume=" at which the swap header is located,
3341 in <PAGE_SIZE> units (needed only for swap files).
3342 See Documentation/power/swsusp-and-swap-files.txt
3343
Barry Songf126f732011-10-10 23:38:41 +02003344 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3345 read the resume files
3346
Barry Song6f8d7022011-10-06 20:34:46 +02003347 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3348 Useful for devices that are detected asynchronously
3349 (e.g. USB and MMC devices).
3350
Bojan Smojverf996fc92010-09-09 23:06:23 +02003351 hibernate= [HIBERNATION]
3352 noresume Don't check if there's a hibernation image
3353 present during boot.
3354 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003355 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003356
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003357 retain_initrd [RAM] Keep initrd memory after extraction
3358
Andrew Clausen0efbb782015-01-09 20:24:55 +00003359 rfkill.default_state=
3360 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3361 etc. communication is blocked by default.
3362 1 Unblocked.
3363
3364 rfkill.master_switch_mode=
3365 0 The "airplane mode" button does nothing.
3366 1 The "airplane mode" button toggles between everything
3367 blocked and the previous configuration.
3368 2 The "airplane mode" button toggles between everything
3369 blocked and everything unblocked.
3370
Linus Torvalds1da177e2005-04-16 15:20:36 -07003371 rhash_entries= [KNL,NET]
3372 Set number of hash buckets for route cache
3373
Linus Torvalds1da177e2005-04-16 15:20:36 -07003374 ro [KNL] Mount root device read-only on boot
3375
3376 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07003377 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003378
3379 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3380 mount the root filesystem
3381
3382 rootflags= [KNL] Set root filesystem mount option string
3383
3384 rootfstype= [KNL] Set root filesystem type
3385
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003386 rootwait [KNL] Wait (indefinitely) for root device to show up.
3387 Useful for devices that are detected asynchronously
3388 (e.g. USB and MMC devices).
3389
Robert Tivy5c71d612013-03-28 18:41:46 -07003390 rproc_mem=nn[KMG][@address]
3391 [KNL,ARM,CMA] Remoteproc physical memory block.
3392 Memory area to be used by remote processor image,
3393 managed by CMA.
3394
Linus Torvalds1da177e2005-04-16 15:20:36 -07003395 rw [KNL] Mount root device read-write on boot
3396
3397 S [KNL] Run init in single mode
3398
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003399 s390_iommu= [HW,S390]
3400 Set s390 IOTLB flushing mode
3401 strict
3402 With strict flushing every unmap operation will result in
3403 an IOTLB flush. Default is lazy flushing before reuse,
3404 which is faster.
3405
Linus Torvalds1da177e2005-04-16 15:20:36 -07003406 sa1100ir [NET]
3407 See drivers/net/irda/sa1100_ir.c.
3408
Linus Torvalds1da177e2005-04-16 15:20:36 -07003409 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003410
Mike Travisf6630112009-11-17 18:22:15 -06003411 sched_debug [KNL] Enables verbose scheduler debug messages.
3412
Mike Galbraith5307c952012-05-08 12:20:58 +02003413 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3414 xtime_lock contention on larger systems, and/or RCU lock
3415 contention on all systems with CONFIG_MAXSMP set.
3416 Format: { "0" | "1" }
3417 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3418 1 -- enable.
3419 Note: increases power consumption, thus should only be
3420 enabled if running jitter sensitive (HPC/RT) workloads.
3421
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003422 security= [SECURITY] Choose a security module to enable at boot.
3423 If this boot parameter is not specified, only the first
3424 security module asking for security registration will be
3425 loaded. An invalid security module name will be treated
3426 as if no module has been chosen.
3427
3428 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003429 Format: { "0" | "1" }
3430 See security/selinux/Kconfig help text.
3431 0 -- disable.
3432 1 -- enable.
3433 Default value is set via kernel config option.
3434 If enabled at boot time, /selinux/disable can be used
3435 later to disable prior to initial policy load.
3436
John Johansenc1c124e2010-07-29 14:48:09 -07003437 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3438 Format: { "0" | "1" }
3439 See security/apparmor/Kconfig help text
3440 0 -- disable.
3441 1 -- enable.
3442 Default value is set via kernel config option.
3443
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003444 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003445
Linus Torvalds1da177e2005-04-16 15:20:36 -07003446 shapers= [NET]
3447 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003448
Yinghai Lub05f78f2008-08-22 01:32:50 -07003449 show_msr= [x86] show boot-time MSR settings
3450 Format: { <integer> }
3451 Show boot-time (BIOS-initialized) MSR settings.
3452 The parameter means the number of CPUs to show,
3453 for example 1 means boot CPU only.
3454
Linus Torvalds1da177e2005-04-16 15:20:36 -07003455 simeth= [IA-64]
3456 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003457
Linus Torvalds1da177e2005-04-16 15:20:36 -07003458 slram= [HW,MTD]
3459
Joonsoo Kim423c9292014-10-09 15:26:22 -07003460 slab_nomerge [MM]
3461 Disable merging of slabs with similar size. May be
3462 necessary if there is some reason to distinguish
3463 allocs to different slabs. Debug options disable
3464 merging on their own.
3465 For more information see Documentation/vm/slub.txt.
3466
David Rientjes3df1ccc2011-10-18 22:09:28 -07003467 slab_max_order= [MM, SLAB]
3468 Determines the maximum allowed order for slabs.
3469 A high setting may cause OOMs due to memory
3470 fragmentation. Defaults to 1 for systems with
3471 more than 32MB of RAM, 0 otherwise.
3472
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003473 slub_debug[=options[,slabs]] [MM, SLUB]
3474 Enabling slub_debug allows one to determine the
3475 culprit if slab objects become corrupted. Enabling
3476 slub_debug can create guard zones around objects and
3477 may poison objects when not in use. Also tracks the
3478 last alloc / free. For more information see
3479 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003480
3481 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003482 Determines the maximum allowed order for slabs.
3483 A high setting may cause OOMs due to memory
3484 fragmentation. For more information see
3485 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003486
3487 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003488 The minimum number of objects per slab. SLUB will
3489 increase the slab order up to slub_max_order to
3490 generate a sufficiently large slab able to contain
3491 the number of objects indicated. The higher the number
3492 of objects the smaller the overhead of tracking slabs
3493 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003494 For more information see Documentation/vm/slub.txt.
3495
3496 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003497 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003498 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003499 For more information see Documentation/vm/slub.txt.
3500
3501 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003502 Same with slab_nomerge. This is supported for legacy.
3503 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003504
Linus Torvalds1da177e2005-04-16 15:20:36 -07003505 smart2= [HW]
3506 Format: <io1>[,<io2>[,...,<io8>]]
3507
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003508 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3509 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3510 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3511 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3512 smsc-ircc2.ircc_irq= [HW] IRQ line
3513 smsc-ircc2.ircc_dma= [HW] DMA channel
3514 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3515 0: Toshiba Satellite 1800 (GP data pin select)
3516 1: Fast pin select (default)
3517 2: ATC IRMode
3518
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003519 softlockup_panic=
3520 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003521 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003522
Aaron Tomlined235872014-06-23 13:22:05 -07003523 softlockup_all_cpu_backtrace=
3524 [KNL] Should the soft-lockup detector generate
3525 backtraces on all cpus.
3526 Format: <integer>
3527
Linus Torvalds1da177e2005-04-16 15:20:36 -07003528 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003529 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003530
Linus Torvalds1da177e2005-04-16 15:20:36 -07003531 spia_io_base= [HW,MTD]
3532 spia_fio_base=
3533 spia_pedr=
3534 spia_peddr=
3535
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003536 stacktrace [FTRACE]
3537 Enabled the stack tracer on boot up.
3538
Steven Rostedt762e1202011-12-19 22:01:00 -05003539 stacktrace_filter=[function-list]
3540 [FTRACE] Limit the functions that the stack tracer
3541 will trace at boot up. function-list is a comma separated
3542 list of functions. This list can be changed at run
3543 time by the stack_trace_filter file in the debugfs
3544 tracing directory. Note, this enables stack tracing
3545 and the stacktrace above is not needed.
3546
Linus Torvalds1da177e2005-04-16 15:20:36 -07003547 sti= [PARISC,HW]
3548 Format: <num>
3549 Set the STI (builtin display/keyboard on the HP-PARISC
3550 machines) console (graphic card) which should be used
3551 as the initial boot-console.
3552 See also comment in drivers/video/console/sticore.c.
3553
3554 sti_font= [HW]
3555 See comment in drivers/video/console/sticore.c.
3556
3557 stifb= [HW]
3558 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3559
Trond Myklebustcbf11072009-08-09 15:06:19 -04003560 sunrpc.min_resvport=
3561 sunrpc.max_resvport=
3562 [NFS,SUNRPC]
3563 SunRPC servers often require that client requests
3564 originate from a privileged port (i.e. a port in the
3565 range 0 < portnr < 1024).
3566 An administrator who wishes to reserve some of these
3567 ports for other uses may adjust the range that the
3568 kernel's sunrpc client considers to be privileged
3569 using these two parameters to set the minimum and
3570 maximum port values.
3571
Greg Banks42a7fc42007-03-06 01:42:23 -08003572 sunrpc.pool_mode=
3573 [NFS]
3574 Control how the NFS server code allocates CPUs to
3575 service thread pools. Depending on how many NICs
3576 you have and where their interrupts are bound, this
3577 option will affect which CPUs will do NFS serving.
3578 Note: this parameter cannot be changed while the
3579 NFS server is running.
3580
3581 auto the server chooses an appropriate mode
3582 automatically using heuristics
3583 global a single global pool contains all CPUs
3584 percpu one pool for each CPU
3585 pernode one pool for each NUMA node (equivalent
3586 to global on non-NUMA machines)
3587
Trond Myklebustcbf11072009-08-09 15:06:19 -04003588 sunrpc.tcp_slot_table_entries=
3589 sunrpc.udp_slot_table_entries=
3590 [NFS,SUNRPC]
3591 Sets the upper limit on the number of simultaneous
3592 RPC calls that can be sent from the client to a
3593 server. Increasing these values may allow you to
3594 improve throughput, but will also increase the
3595 amount of memory reserved for use by the client.
3596
Brian Norris1d4a9c12015-02-22 21:16:49 -08003597 suspend.pm_test_delay=
3598 [SUSPEND]
3599 Sets the number of seconds to remain in a suspend test
3600 mode before resuming the system (see
3601 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3602 is set. Default value is 5.
3603
Michal Hocko07555ac2013-08-22 16:35:46 -07003604 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003605 [KNL] Enable accounting of swap in memory resource
3606 controller if no parameter or 1 is given or disable
3607 it if 0 is given (See Documentation/cgroups/memory.txt)
3608
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003609 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3610 Format: { <int> | force }
3611 <int> -- Number of I/O TLB slabs
3612 force -- force using of bounce buffers even if they
3613 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003614
Linus Torvalds1da177e2005-04-16 15:20:36 -07003615 switches= [HW,M68k]
3616
Andi Kleene52eec12010-09-08 16:54:17 +02003617 sysfs.deprecated=0|1 [KNL]
3618 Enable/disable old style sysfs layout for old udev
3619 on older distributions. When this option is enabled
3620 very new udev will not work anymore. When this option
3621 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3622 in older udev will not work anymore.
3623 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3624 the kernel configuration.
3625
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003626 sysrq_always_enabled
3627 [KNL]
3628 Ignore sysrq setting - this boot parameter will
3629 neutralize any effect of /proc/sys/kernel/sysrq.
3630 Useful for debugging.
3631
Fabian Frederick747029a2014-11-06 19:46:50 +01003632 tcpmhash_entries= [KNL,NET]
3633 Set the number of tcp_metrics_hash slots.
3634 Default value is 8192 or 16384 depending on total
3635 ram pages. This is used to specify the TCP metrics
3636 cache size. See Documentation/networking/ip-sysctl.txt
3637 "tcp_no_metrics_save" section for more details.
3638
Linus Torvalds1da177e2005-04-16 15:20:36 -07003639 tdfx= [HW,DRM]
3640
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003641 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003642 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003643 standby suspend) or "freeze" (for suspend type freeze)
3644 as the system sleep state during system startup with
3645 the optional capability to repeat N number of times.
3646 The system is woken from this state using a
3647 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003648
Linus Torvalds1da177e2005-04-16 15:20:36 -07003649 thash_entries= [KNL,NET]
3650 Set number of hash buckets for TCP connection
3651
Len Brownf8707ec2007-08-12 00:12:54 -04003652 thermal.act= [HW,ACPI]
3653 -1: disable all active trip points in all thermal zones
3654 <degrees C>: override all lowest active trip points
3655
Len Brownc52a7412007-08-14 15:49:32 -04003656 thermal.crt= [HW,ACPI]
3657 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003658 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003659
Len Brownf5487142007-08-12 00:12:44 -04003660 thermal.nocrt= [HW,ACPI]
3661 Set to disable actions on ACPI thermal zone
3662 critical and hot trip points.
3663
Len Brown72b33ef2007-08-12 00:12:17 -04003664 thermal.off= [HW,ACPI]
3665 1: disable ACPI thermal control
3666
Len Browna70cdc52007-08-12 00:12:35 -04003667 thermal.psv= [HW,ACPI]
3668 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003669 <degrees C>: override all passive trip points to this
3670 value
Len Browna70cdc52007-08-12 00:12:35 -04003671
Len Brown730ff342007-08-12 00:12:26 -04003672 thermal.tzp= [HW,ACPI]
3673 Specify global default ACPI thermal zone polling rate
3674 <deci-seconds>: poll all this frequency
3675 0: no polling (default)
3676
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003677 threadirqs [KNL]
3678 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003679 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003680
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003681 tmem [KNL,XEN]
3682 Enable the Transcendent memory driver if built-in.
3683
3684 tmem.cleancache=0|1 [KNL, XEN]
3685 Default is on (1). Disable the usage of the cleancache
3686 API to send anonymous pages to the hypervisor.
3687
3688 tmem.frontswap=0|1 [KNL, XEN]
3689 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003690 API to send swap pages to the hypervisor. If disabled
3691 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003692
3693 tmem.selfballooning=0|1 [KNL, XEN]
3694 Default is on (1). Disable the driving of swap pages
3695 to the hypervisor.
3696
3697 tmem.selfshrinking=0|1 [KNL, XEN]
3698 Default is on (1). Partial swapoff that immediately
3699 transfers pages from Xen hypervisor back to the
3700 kernel based on different criteria.
3701
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003702 topology= [S390]
3703 Format: {off | on}
3704 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003705 topology information if the hardware supports this.
3706 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003707 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003708 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003709
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003710 topology_updates= [KNL, PPC, NUMA]
3711 Format: {off}
3712 Specify if the kernel should ignore (off)
3713 topology updates sent by the hypervisor to this
3714 LPAR.
3715
Linus Torvalds1da177e2005-04-16 15:20:36 -07003716 tp720= [HW,PS2]
3717
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003718 tpm_suspend_pcr=[HW,TPM]
3719 Format: integer pcr id
3720 Specify that at suspend time, the tpm driver
3721 should extend the specified pcr with zeros,
3722 as a workaround for some chips which fail to
3723 flush the last written pcr on TPM_SaveState.
3724 This will guarantee that all the other pcrs
3725 are saved.
3726
Li Zefan9d612be2009-06-24 17:33:15 +08003727 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003728 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003729
Li Zefan020e5f82009-07-01 10:47:05 +08003730 trace_event=[event-list]
3731 [FTRACE] Set and start specified trace events in order
3732 to facilitate early boot debugging.
3733 See also Documentation/trace/events.txt
3734
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003735 trace_options=[option-list]
3736 [FTRACE] Enable or disable tracer options at boot.
3737 The option-list is a comma delimited list of options
3738 that can be enabled or disabled just as if you were
3739 to echo the option name into
3740
3741 /sys/kernel/debug/tracing/trace_options
3742
3743 For example, to enable stacktrace option (to dump the
3744 stack trace of each event), add to the command line:
3745
3746 trace_options=stacktrace
3747
3748 See also Documentation/trace/ftrace.txt "trace options"
3749 section.
3750
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003751 tp_printk[FTRACE]
3752 Have the tracepoints sent to printk as well as the
3753 tracing ring buffer. This is useful for early boot up
3754 where the system hangs or reboots and does not give the
3755 option for reading the tracing buffer or performing a
3756 ftrace_dump_on_oops.
3757
3758 To turn off having tracepoints sent to printk,
3759 echo 0 > /proc/sys/kernel/tracepoint_printk
3760 Note, echoing 1 into this file without the
3761 tracepoint_printk kernel cmdline option has no effect.
3762
3763 ** CAUTION **
3764
3765 Having tracepoints sent to printk() and activating high
3766 frequency tracepoints such as irq or sched, can cause
3767 the system to live lock.
3768
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003769 traceoff_on_warning
3770 [FTRACE] enable this option to disable tracing when a
3771 warning is hit. This turns off "tracing_on". Tracing can
3772 be enabled again by echoing '1' into the "tracing_on"
3773 file located in /sys/kernel/debug/tracing/
3774
3775 This option is useful, as it disables the trace before
3776 the WARNING dump is called, which prevents the trace to
3777 be filled with content caused by the warning output.
3778
3779 This option can also be set at run time via the sysctl
3780 option: kernel/traceoff_on_warning
3781
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003782 transparent_hugepage=
3783 [KNL]
3784 Format: [always|madvise|never]
3785 Can be used to control the default behavior of the system
3786 with respect to transparent hugepages.
3787 See Documentation/vm/transhuge.txt for more details.
3788
john stultzd3b8f882009-08-17 16:40:47 -07003789 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003790 Format: <string>
3791 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003792 disables clocksource verification at runtime, as well
3793 as the stability checks done at bootup. Used to enable
3794 high-resolution timer mode on older hardware, and in
3795 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003796 [x86] noirqtime: Do not use TSC to do irq accounting.
3797 Used to run time disable IRQ_TIME_ACCOUNTING on any
3798 platforms where RDTSC is slow and this accounting
3799 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003800
Randy Dunlapa9913042005-10-23 12:57:11 -07003801 turbografx.map[2|3]= [HW,JOY]
3802 TurboGraFX parallel port interface
3803 Format:
3804 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003805 See also Documentation/input/joystick-parport.txt
3806
Christian Kujaub6935f82011-05-31 15:22:05 +00003807 udbg-immortal [PPC] When debugging early kernel crashes that
3808 happen after console_init() and before a proper
3809 console driver takes over, this boot options might
3810 help "seeing" what's going on.
3811
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003812 uhash_entries= [KNL,NET]
3813 Set number of hash buckets for UDP/UDP-Lite connections
3814
Alan Stern5f8364b2006-12-05 16:29:55 -05003815 uhci-hcd.ignore_oc=
3816 [USB] Ignore overcurrent events (default N).
3817 Some badly-designed motherboards generate lots of
3818 bogus events, for ports that aren't wired to
3819 anything. Set this parameter to avoid log spamming.
3820 Note that genuine overcurrent events won't be
3821 reported either.
3822
Simon Arlotte3a61b02008-07-19 23:32:54 +01003823 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003824 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003825
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003826 usbcore.authorized_default=
3827 [USB] Default USB device authorization:
3828 (default -1 = authorized except for wireless USB,
3829 0 = not authorized, 1 = authorized)
3830
Alan Sternb5e795f2007-02-20 15:00:53 -05003831 usbcore.autosuspend=
3832 [USB] The autosuspend time delay (in seconds) used
3833 for newly-detected USB devices (default 2). This
3834 is the time required before an idle device will be
3835 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003836 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003837
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003838 usbcore.usbfs_snoop=
3839 [USB] Set to log all usbfs traffic (default 0 = off).
3840
3841 usbcore.blinkenlights=
3842 [USB] Set to cycle leds on hubs (default 0 = off).
3843
3844 usbcore.old_scheme_first=
3845 [USB] Start with the old device initialization
3846 scheme (default 0 = off).
3847
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003848 usbcore.usbfs_memory_mb=
3849 [USB] Memory limit (in MB) for buffers allocated by
3850 usbfs (default = 16, 0 = max = 2047).
3851
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003852 usbcore.use_both_schemes=
3853 [USB] Try the other device initialization scheme
3854 if the first one fails (default 1 = enabled).
3855
3856 usbcore.initial_descriptor_timeout=
3857 [USB] Specifies timeout for the initial 64-byte
3858 USB_REQ_GET_DESCRIPTOR request in milliseconds
3859 (default 5000 = 5.0 seconds).
3860
Linus Torvalds1da177e2005-04-16 15:20:36 -07003861 usbhid.mousepoll=
3862 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003863
Alan Sternd4f373e2008-11-10 14:07:45 -05003864 usb-storage.delay_use=
3865 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00003866 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05003867
3868 usb-storage.quirks=
3869 [UMS] A list of quirks entries to supplement or
3870 override the built-in unusual_devs list. List
3871 entries are separated by commas. Each entry has
3872 the form VID:PID:Flags where VID and PID are Vendor
3873 and Product ID values (4-digit hex numbers) and
3874 Flags is a set of characters, each corresponding
3875 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003876 a = SANE_SENSE (collect more than 18 bytes
3877 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003878 b = BAD_SENSE (don't collect more than 18
3879 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003880 c = FIX_CAPACITY (decrease the reported
3881 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003882 d = NO_READ_DISC_INFO (don't use
3883 READ_DISC_INFO command);
3884 e = NO_READ_CAPACITY_16 (don't use
3885 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003886 f = NO_REPORT_OPCODES (don't use report opcodes
3887 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02003888 g = MAX_SECTORS_240 (don't transfer more than
3889 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003890 h = CAPACITY_HEURISTICS (decrease the
3891 reported device capacity by one
3892 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003893 i = IGNORE_DEVICE (don't bind to this
3894 device);
3895 l = NOT_LOCKABLE (don't try to lock and
3896 unlock ejectable media);
3897 m = MAX_SECTORS_64 (don't transfer more
3898 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003899 n = INITIAL_READ10 (force a retry of the
3900 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003901 o = CAPACITY_OK (accept the capacity
3902 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003903 p = WRITE_CACHE (the device cache is ON
3904 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003905 r = IGNORE_RESIDUE (the device reports
3906 bogus residue values);
3907 s = SINGLE_LUN (the device has only one
3908 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003909 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3910 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003911 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003912 w = NO_WP_DETECT (don't test whether the
3913 medium is write-protected).
3914 Example: quirks=0419:aaf5:rl,0421:0433:rc
3915
Stephen Boydac1667d2011-08-13 12:34:50 -07003916 user_debug= [KNL,ARM]
3917 Format: <int>
3918 See arch/arm/Kconfig.debug help text.
3919 1 - undefined instruction events
3920 2 - system calls
3921 4 - invalid data aborts
3922 8 - SIGSEGV faults
3923 16 - SIGBUS faults
3924 Example: user_debug=31
3925
Ian Campbell14315592010-02-17 10:38:10 +00003926 userpte=
3927 [X86] Flags controlling user PTE allocations.
3928
3929 nohigh = do not allocate PTE pages in
3930 HIGHMEM regardless of setting
3931 of CONFIG_HIGHPTE.
3932
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303933 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003934 On X86_32, this is an alias for vdso32=. Otherwise:
3935
3936 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003937 vdso=0: disable VDSO mapping
3938
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003939 vdso32= [X86] Control the 32-bit vDSO
3940 vdso32=1: enable 32-bit VDSO
3941 vdso32=0 or vdso32=2: disable 32-bit VDSO
3942
3943 See the help text for CONFIG_COMPAT_VDSO for more
3944 details. If CONFIG_COMPAT_VDSO is set, the default is
3945 vdso32=0; otherwise, the default is vdso32=1.
3946
3947 For compatibility with older kernels, vdso32=2 is an
3948 alias for vdso32=0.
3949
3950 Try vdso32=0 if you encounter an error that says:
3951 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003952
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003953 vector= [IA-64,SMP]
3954 vector=percpu: enable percpu vector domain
3955
Linus Torvalds1da177e2005-04-16 15:20:36 -07003956 video= [FB] Frame buffer configuration
3957 See Documentation/fb/modedb.txt.
3958
Aaron Lu3afe6da2013-06-20 15:08:55 +08003959 video.brightness_switch_enabled= [0,1]
3960 If set to 1, on receiving an ACPI notify event
3961 generated by hotkey, video driver will adjust brightness
3962 level and then send out the event to user space through
3963 the allocated input device; If set to 0, video driver
3964 will only send out the event without touching backlight
3965 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02003966 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08003967
Pawel Moll81a054c2012-05-09 18:30:16 +01003968 virtio_mmio.device=
3969 [VMMIO] Memory mapped virtio (platform) device.
3970
3971 <size>@<baseaddr>:<irq>[:<id>]
3972 where:
3973 <size> := size (can use standard suffixes
3974 like K, M and G)
3975 <baseaddr> := physical base address
3976 <irq> := interrupt number (as passed to
3977 request_irq())
3978 <id> := (optional) platform device id
3979 example:
3980 virtio_mmio.device=1K@0x100b0000:48:7
3981
3982 Can be used multiple times for multiple devices.
3983
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003984 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003985 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003986 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003987 Use vga=ask for menu.
3988 This is actually a boot loader parameter; the value is
3989 passed to the kernel using a special protocol.
3990
Randy Dunlapa9913042005-10-23 12:57:11 -07003991 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003992 size of <nn>. This can be used to increase the
3993 minimum size (128MB on x86). It can also be used to
3994 decrease the size and leave more room for directly
3995 mapped kernel RAM.
3996
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003997 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3998 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003999
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004000 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4001 Format: <command>
4002
4003 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4004 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004005
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004006 vsyscall= [X86-64]
4007 Controls the behavior of vsyscalls (i.e. calls to
4008 fixed addresses of 0xffffffffff600x00 from legacy
4009 code). Most statically-linked binaries and older
4010 versions of glibc use these calls. Because these
4011 functions are at fixed addresses, they make nice
4012 targets for exploits that can control RIP.
4013
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004014 emulate [default] Vsyscalls turn into traps and are
4015 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004016
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004017 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004018 This is a little bit faster than trapping
4019 and makes a few dynamic recompilers work
4020 better than they would in emulation mode.
4021 It also makes exploits much easier to write.
4022
4023 none Vsyscalls don't work at all. This makes
4024 them quite hard to use for exploits but
4025 might break your system.
4026
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004027 vt.color= [VT] Default text color.
4028 Format: 0xYX, X = foreground, Y = background.
4029 Default: 0x07 = light gray on black.
4030
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004031 vt.cur_default= [VT] Default cursor shape.
4032 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4033 the parameters of the <Esc>[?A;B;Cc escape sequence;
4034 see VGA-softcursor.txt. Default: 2 = underline.
4035
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004036 vt.default_blu= [VT]
4037 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4038 Change the default blue palette of the console.
4039 This is a 16-member array composed of values
4040 ranging from 0-255.
4041
4042 vt.default_grn= [VT]
4043 Format: <green0>,<green1>,<green2>,...,<green15>
4044 Change the default green palette of the console.
4045 This is a 16-member array composed of values
4046 ranging from 0-255.
4047
4048 vt.default_red= [VT]
4049 Format: <red0>,<red1>,<red2>,...,<red15>
4050 Change the default red palette of the console.
4051 This is a 16-member array composed of values
4052 ranging from 0-255.
4053
4054 vt.default_utf8=
4055 [VT]
4056 Format=<0|1>
4057 Set system-wide default UTF-8 mode for all tty's.
4058 Default is 1, i.e. UTF-8 mode is enabled for all
4059 newly opened terminals.
4060
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004061 vt.global_cursor_default=
4062 [VT]
4063 Format=<-1|0|1>
4064 Set system-wide default for whether a cursor
4065 is shown on new VTs. Default is -1,
4066 i.e. cursors will be created by default unless
4067 overridden by individual drivers. 0 will hide
4068 cursors, 1 will display them.
4069
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004070 vt.italic= [VT] Default color for italic text; 0-15.
4071 Default: 2 = green.
4072
4073 vt.underline= [VT] Default color for underlined text; 0-15.
4074 Default: 3 = cyan.
4075
Randy Dunlap4724ba572010-05-03 11:42:52 -07004076 watchdog timers [HW,WDT] For information on watchdog timers,
4077 see Documentation/watchdog/watchdog-parameters.txt
4078 or other driver-specific files in the
4079 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004080
Tejun Heod55262c2013-04-01 11:23:38 -07004081 workqueue.disable_numa
4082 By default, all work items queued to unbound
4083 workqueues are affine to the NUMA nodes they're
4084 issued on, which results in better behavior in
4085 general. If NUMA affinity needs to be disabled for
4086 whatever reason, this option can be used. Note
4087 that this also can be controlled per-workqueue for
4088 workqueues visible under /sys/bus/workqueue/.
4089
Viresh Kumarcee22a12013-04-08 16:45:40 +05304090 workqueue.power_efficient
4091 Per-cpu workqueues are generally preferred because
4092 they show better performance thanks to cache
4093 locality; unfortunately, per-cpu workqueues tend to
4094 be more power hungry than unbound workqueues.
4095
4096 Enabling this makes the per-cpu workqueues which
4097 were observed to contribute significantly to power
4098 consumption unbound, leading to measurably lower
4099 power usage at the cost of small performance
4100 overhead.
4101
4102 The default value of this parameter is determined by
4103 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4104
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004105 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4106 default x2apic cluster mode on platforms
4107 supporting x2apic.
4108
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004109 x86_intel_mid_timer= [X86-32,APBT]
4110 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004111 Two valid options are apbt timer only and lapic timer
4112 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004113 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004114
Juergen Grossc70727a2015-07-17 06:51:36 +02004115 xen_512gb_limit [KNL,X86-64,XEN]
4116 Restricts the kernel running paravirtualized under Xen
4117 to use only up to 512 GB of RAM. The reason to do so is
4118 crash analysis tools and Xen tools for doing domain
4119 save/restore/migration must be enabled to handle larger
4120 domains.
4121
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004122 xen_emul_unplug= [HW,X86,XEN]
4123 Unplug Xen emulated devices
4124 Format: [unplug0,][unplug1]
4125 ide-disks -- unplug primary master IDE devices
4126 aux-ide-disks -- unplug non-primary-master IDE devices
4127 nics -- unplug network devices
4128 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004129 unnecessary -- unplugging emulated devices is
4130 unnecessary even if the host did not respond to
4131 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004132 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004133
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004134 xen_nopvspin [X86,XEN]
4135 Disables the ticketlock slowpath using Xen PV
4136 optimizations.
4137
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004138 xen_nopv [X86]
4139 Disables the PV optimizations forcing the HVM guest to
4140 run as generic HVM guest with no PV drivers.
4141
Linus Torvalds1da177e2005-04-16 15:20:36 -07004142 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004143 Format:
4144 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004145
Randy Dunlapa9913042005-10-23 12:57:11 -07004146______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004147
4148TODO:
4149
Linus Torvalds1da177e2005-04-16 15:20:36 -07004150 Add more DRM drivers.