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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
Noam Camus2d13e6c2016-10-11 13:51:35 -070036cpu lists:
37----------
38
39Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
40nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
41
42 <cpu number>,...,<cpu number>
43
44or
45
46 <cpu number>-<cpu number>
47 (must be a positive range in ascending order)
48
49or a mixture
50
51<cpu number>,...,<cpu number>-<cpu number>
52
53Note that for the special case of a range one can split the range into equal
54sized groups and for each group use some amount from the beginning of that
55group:
56
57 <cpu number>-cpu number>:<used size>/<group size>
58
59For example one can add to the command line following parameter:
60
61 isolcpus=1,2,10-20,100-2000:2/25
62
63where the final item represents CPUs 100,101,125,126,150,151,...
64
65
66
Stefan Richtera901ebb2006-04-01 01:43:18 +020067This document may not be entirely up to date and comprehensive. The command
68"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
69module. Loadable modules, after being loaded into the running kernel, also
70reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
71parameters may be changed at runtime by the command
72"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
73
Stefan Richter6585fa82006-04-01 01:44:30 +020074The parameters listed below are only valid if certain kernel build options were
75enabled and if respective hardware is present. The text in square brackets at
76the beginning of each description states the restrictions within which a
77parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070078
79 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100080 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 ALSA ALSA sound support is enabled.
82 APIC APIC support is enabled.
83 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070084 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020085 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080087 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070088 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070089 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000090 DRM Direct Rendering Management support is enabled.
91 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070092 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
93 EFI EFI Partitioning (GPT) is enabled
94 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040095 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070097 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070098 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -0500101 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -0700103 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -0800104 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 ISAPNP ISA PnP code is enabled.
106 ISDN Appropriate ISDN support is enabled.
107 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -0500108 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +0200109 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -0700110 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 LP Printer support is enabled.
112 LOOP Loopback device support is enabled.
113 M68k M68k architecture is enabled.
114 These options have more detailed description inside of
115 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -0700117 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -0700119 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700120 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 NET Appropriate network support is enabled.
122 NUMA NUMA support is enabled.
123 NFS Appropriate NFS support is enabled.
124 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700125 PV_OPS A paravirtualized kernel is enabled.
126 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127 PARISC The PA-RISC architecture is enabled.
128 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -0700129 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 PCMCIA The PCMCIA subsystem is enabled.
131 PNP Plug & Play support is enabled.
132 PPC PowerPC architecture is enabled.
133 PPT Parallel port support is enabled.
134 PS2 Appropriate PS/2 support is enabled.
135 RAM RAM disk support is enabled.
136 S390 S390 architecture is enabled.
137 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -0700138 A lot of drivers have their options described inside
139 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -0700140 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700142 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900144 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 SMP The kernel is an SMP kernel.
146 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700147 SWSUSP Software suspend (hibernation) is enabled.
148 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300149 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500151 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 USB USB support is enabled.
153 USBHID USB Human Interface Device support is enabled.
154 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100155 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 VGA The VGA console has been enabled.
157 VT Virtual terminal support is enabled.
158 WDT Watchdog support is enabled.
159 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700160 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 X86-64 X86-64 architecture is enabled.
162 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700163 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700164 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Alex Thorlton1c532e02016-03-31 14:18:29 -0500165 X86_UV SGI UV support is enabled.
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100166 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167
168In addition, the following text indicates that the option:
169
170 BUGS= Relates to possible processor bugs on the said processor.
171 KNL Is a kernel start-up parameter.
172 BOOT Is a boot loader parameter.
173
174Parameters denoted with BOOT are actually interpreted by the boot
175loader, and have no meaning to the kernel directly.
176Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500177need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
Karsten Weiss55588702007-02-13 13:26:21 +0100179There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700180See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100181
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
183a trailing = on the name of any parameter states that that parameter will
184be entered as an environment variable, whereas its absence indicates that
185it will appear as a kernel argument readable via /proc/cmdline by programs
186running once the system is up.
187
jens m. noedler9c4751f2006-09-29 02:00:27 -0700188The number of kernel parameters is not limited, but the length of the
189complete command line (parameters including spaces etc.) is limited to
190a fixed number of characters. This limit depends on the architecture
191and is between 256 and 4096 characters. It is defined in the file
192./include/asm/setup.h as COMMAND_LINE_SIZE.
193
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800194Finally, the [KMG] suffix is commonly described after a number of kernel
195parameter values. These 'K', 'M', and 'G' letters represent the _binary_
196multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
197bytes respectively. Such letter suffixes can also be entirely omitted.
198
jens m. noedler9c4751f2006-09-29 02:00:27 -0700199
Al Stoneb10d79f2015-03-24 14:02:41 +0000200 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800201 Advanced Configuration and Power Interface
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200202 Format: { force | on | off | strict | noirq | rsdt |
Rami Rosene58d1542015-09-26 19:27:57 +0300203 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 force -- enable ACPI if default was off
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200205 on -- enable ACPI but allow fallback to DT [arm64]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206 off -- disable ACPI if default was on
207 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700208 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800210 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800211 copy_dsdt -- copy DSDT to memory
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +0200212 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
213 are available
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
Paul Bolle395cf962011-08-15 02:02:26 +0200215 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216
Len Browna1fdcc02007-03-11 03:26:14 -0400217 acpi_apic_instance= [ACPI, IOAPIC]
218 Format: <int>
219 2: use 2nd APIC table, if available
220 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400221 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400222
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200223 acpi_backlight= [HW,ACPI]
224 acpi_backlight=vendor
225 acpi_backlight=video
226 If set to vendor, prefer vendor specific driver
227 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
228 of the ACPI video.ko driver.
229
Colin Ian Kingb2ca5da2016-01-21 17:05:47 +0000230 acpi_force_32bit_fadt_addr
231 force FADT to use 32 bit addresses rather than the
232 64 bit X_* addresses. Some firmware have broken 64
233 bit addresses for force ACPI ignore these and use
234 the older legacy 32 bit addresses.
235
Dominik Brodowskief694492015-05-14 15:31:28 +0200236 acpica_no_return_repair [HW, ACPI]
237 Disable AML predefined validation mechanism
238 This mechanism can repair the evaluation result to make
239 the return objects more ACPI specification compliant.
240 This option is useful for developers to identify the
241 root cause of an AML interpreter issue when the issue
242 has something to do with the repair mechanism.
243
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700244 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
245 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700247 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
248 debug output. Bits in debug_layer correspond to a
249 _COMPONENT in an ACPI source file, e.g.,
250 #define _COMPONENT ACPI_PCI_COMPONENT
251 Bits in debug_level correspond to a level in
252 ACPI_DEBUG_PRINT statements, e.g.,
253 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600254 The debug_level mask defaults to "info". See
255 Documentation/acpi/debug.txt for more information about
256 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600258 Enable processor driver info messages:
259 acpi.debug_layer=0x20000000
260 Enable PCI/PCI interrupt routing info messages:
261 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700262 Enable AML "Debug" output, i.e., stores to the Debug
263 object while interpreting AML:
264 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700265 Enable all messages related to ACPI hardware:
266 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200267
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700268 Some values produce so much output that the system is
269 unusable. The "log_buf_len" parameter may be useful
270 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800271
Dominik Brodowskief694492015-05-14 15:31:28 +0200272 acpi_enforce_resources= [ACPI]
273 { strict | lax | no }
274 Check for resource conflicts between native drivers
275 and ACPI OperationRegions (SystemIO and SystemMemory
276 only). IO ports and memory declared in ACPI might be
277 used by the ACPI subsystem in arbitrary AML code and
278 can interfere with legacy drivers.
279 strict (default): access to resources claimed by ACPI
280 is denied; legacy drivers trying to access reserved
281 resources will fail to bind to device using them.
282 lax: access to resources claimed by ACPI is allowed;
283 legacy drivers trying to access reserved resources
284 will bind successfully but a warning message is logged.
285 no: ACPI OperationRegions are not marked as reserved,
286 no further checks are performed.
287
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800288 acpi_force_table_verification [HW,ACPI]
289 Enable table checksum verification during early stage.
290 By default, this is disabled due to x86 early mapping
291 size limitation.
292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700293 acpi_irq_balance [HW,ACPI]
294 ACPI will balance active IRQs
295 default in APIC mode
296
297 acpi_irq_nobalance [HW,ACPI]
298 ACPI will not move active IRQs (default)
299 default in PIC mode
300
301 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
302 Format: <irq>,<irq>...
303
304 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
305 use by PCI
306 Format: <irq>,<irq>...
307
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800308 acpi_no_auto_serialize [HW,ACPI]
309 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800310 AML control methods that contain the opcodes to create
311 named objects will be marked as "Serialized" by the
312 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800313 This feature is enabled by default.
314 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800315
Dominik Brodowskief694492015-05-14 15:31:28 +0200316 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
317 kernels.
318
Lv Zhenga94e88c2014-04-04 12:39:11 +0800319 acpi_no_static_ssdt [HW,ACPI]
320 Disable installation of static SSDTs at early boot time
321 By default, SSDTs contained in the RSDT/XSDT will be
322 installed automatically and they will appear under
323 /sys/firmware/acpi/tables.
324 This option turns off this feature.
325 Note that specifying this option does not affect
326 dynamic table installation which will install SSDT
327 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700328
Dominik Brodowskief694492015-05-14 15:31:28 +0200329 acpi_rsdp= [ACPI,EFI,KEXEC]
330 Pass the RSDP address to the kernel, mostly used
331 on machines running EFI runtime service to boot the
332 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800333
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700334 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
335 Format: To spoof as Windows 98: ="Microsoft Windows"
336
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200337 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
338 of 2 which is mandated by ACPI 6) as the supported ACPI
339 specification revision (when using this switch, it may
340 be necessary to carry out a cold reboot _twice_ in a
341 row to make it take effect on the platform firmware).
342
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700343 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800344 acpi_osi="string1" # add string1
345 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800346 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800347 acpi_osi=! # disable all built-in OS vendor
348 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800349 acpi_osi=!! # enable all built-in OS vendor
350 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700351 acpi_osi= # disable all strings
352
Lv Zheng5dc17982013-07-22 16:08:25 +0800353 'acpi_osi=!' can be used in combination with single or
354 multiple 'acpi_osi="string1"' to support specific OS
355 vendor string(s). Note that such command can only
356 affect the default state of the OS vendor strings, thus
357 it cannot affect the default state of the feature group
358 strings and the current state of the OS vendor strings,
359 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800360 is meaningless. This command is useful when one do not
361 care about the state of the feature group strings which
362 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800363 Examples:
364 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
365 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
366 can make '_OSI("Windows 2000")' TRUE.
367
368 'acpi_osi=' cannot be used in combination with other
369 'acpi_osi=' command lines, the _OSI method will not
370 exist in the ACPI namespace. NOTE that such command can
371 only affect the _OSI support state, thus specifying it
372 multiple times through kernel command line is also
373 meaningless.
374 Examples:
375 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
376 FALSE.
377
Lv Zheng741d8122013-07-22 16:08:36 +0800378 'acpi_osi=!*' can be used in combination with single or
379 multiple 'acpi_osi="string1"' to support specific
380 string(s). Note that such command can affect the
381 current state of both the OS vendor strings and the
382 feature group strings, thus specifying it multiple times
383 through kernel command line is meaningful. But it may
384 still not able to affect the final state of a string if
385 there are quirks related to this string. This command
386 is useful when one want to control the state of the
387 feature group strings to debug BIOS issues related to
388 the OSPM features.
389 Examples:
390 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
391 '_OSI("Module Device")' FALSE.
392 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
393 '_OSI("Module Device")' TRUE.
394 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
395 equivalent to
396 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
397 and
398 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
399 they all will make '_OSI("Windows 2000")' TRUE.
400
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530401 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700402 Override the pmtimer bug detection: force the kernel
403 to assume that this machine's pmtimer latches its value
404 and always returns good values.
405
Randy Dunlap4af94f32009-04-17 18:30:28 -0700406 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
407 Format: { level | edge | high | low }
408
Randy Dunlap4af94f32009-04-17 18:30:28 -0700409 acpi_skip_timer_override [HW,ACPI]
410 Recognize and ignore IRQ0/pin2 Interrupt Override.
411 For broken nForce2 BIOS resulting in XT-PIC timer.
412
413 acpi_sleep= [HW,ACPI] Sleep options
414 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200415 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700416 See Documentation/power/video.txt for information on
417 s3_bios and s3_mode.
418 s3_beep is for debugging; it makes the PC's speaker beep
419 as soon as the kernel's real-mode entry point is called.
420 s4_nohwsig prevents ACPI hardware signature from being
421 used during resume from hibernation.
422 old_ordering causes the ACPI 1.0 ordering of the _PTS
423 control method, with respect to putting devices into
424 low power states, to be enforced (the ACPI 2.0 ordering
425 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200426 nonvs prevents the kernel from saving/restoring the
427 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800428 sci_force_enable causes the kernel to set SCI_EN directly
429 on resume from S1/S3 (which is against the ACPI spec,
430 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700431
432 acpi_use_timer_override [HW,ACPI]
433 Use timer override. For some broken Nvidia NF5 boards
434 that require a timer override, but don't have HPET
435
Randy Dunlap4af94f32009-04-17 18:30:28 -0700436 add_efi_memmap [EFI; X86] Include EFI memory map in
437 kernel's map of available physical RAM.
438
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700439 agp= [AGP]
440 { off | try_unsupported }
441 off: disable AGP support
442 try_unsupported: try to drive unsupported chipsets
443 (may crash computer or cause data corruption)
444
Randy Dunlapbcfde332010-06-07 17:10:38 -0700445 ALSA [HW,ALSA]
446 See Documentation/sound/alsa/alsa-parameters.txt
447
Russell Kingd944d542010-02-20 16:13:29 +0000448 alignment= [KNL,ARM]
449 Allow the default userspace alignment fault handler
450 behaviour to be specified. Bit 0 enables warnings,
451 bit 1 enables fixups, and bit 2 sends a segfault.
452
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200453 align_va_addr= [X86-64]
454 Align virtual addresses by clearing slice [14:12] when
455 allocating a VMA at process creation time. This option
456 gives you up to 3% performance improvement on AMD F15h
457 machines (where it is enabled by default) for a
458 CPU-intensive style benchmark, and it can vary highly in
459 a microbenchmark depending on workload and compiler.
460
Borislav Petkov8360ee22011-11-21 12:10:19 +0100461 32: only for 32-bit processes
462 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200463 on: enable for both 32- and 64-bit processes
464 off: disable for both 32- and 64-bit processes
465
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500466 alloc_snapshot [FTRACE]
467 Allocate the ftrace snapshot buffer on boot up when the
468 main buffer is allocated. This is handy if debugging
469 and you need to use tracing_snapshot() on boot up, and
470 do not want to use tracing_snapshot_alloc() as it needs
471 to be done where GFP_KERNEL allocations are allowed.
472
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100473 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200474 Pass parameters to the AMD IOMMU driver in the system.
475 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900476 fullflush - enable flushing of IO/TLB entries when
477 they are unmapped. Otherwise they are
478 flushed before they will be reused, which
479 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200480 off - do not initialize any AMD IOMMU found in
481 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100482 force_isolation - Force device isolation for all
483 devices. The IOMMU driver is not
484 allowed anymore to lift isolation
485 requirements as needed. This option
486 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900487
Shuah Khanc099cf12012-05-24 15:58:25 -0600488 amd_iommu_dump= [HW,X86-64]
489 Enable AMD IOMMU driver option to dump the ACPI table
490 for AMD IOMMU. With this option enabled, AMD IOMMU
491 driver will print ACPI tables for AMD IOMMU during
492 IOMMU initialization.
493
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500494 amd_iommu_intr= [HW,X86-64]
495 Specifies one of the following AMD IOMMU interrupt
496 remapping modes:
497 legacy - Use legacy interrupt remapping mode.
498 vapic - Use virtual APIC mode, which allows IOMMU
499 to inject interrupts directly into guest.
500 This mode requires kvm-amd.avic=1.
501 (Default when IOMMU HW support is present.)
502
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503 amijoy.map= [HW,JOY] Amiga joystick support
504 Map of devices attached to JOY0DAT and JOY1DAT
505 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200506 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507
508 analog.map= [HW,JOY] Analog joystick and gamepad support
509 Specifies type or capabilities of an analog joystick
510 connected to one of 16 gameports
511 Format: <type1>,<type2>,..<type16>
512
Randy Dunlapa9913042005-10-23 12:57:11 -0700513 apc= [HW,SPARC]
514 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 Format: noidle
516 Disable APC CPU standby support. SPARCstation-Fox does
517 not play well with APC CPU idle - disable it if you have
518 APC and your system crashes randomly.
519
Randy Dunlapca1eda22009-05-06 16:02:58 -0700520 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700521 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 Format: { quiet (default) | verbose | debug }
523 Change the amount of debugging information output
524 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700525
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100526 apic_extnmi= [APIC,X86] External NMI delivery setting
527 Format: { bsp (default) | all | none }
528 bsp: External NMI is delivered only to CPU 0
529 all: External NMIs are broadcast to all CPUs as a
530 backup of CPU 0
531 none: External NMI is masked for all CPUs. This is
532 useful so that a dump capture kernel won't be
533 shot down by NMI
534
Brian Haleyb0f83b22010-02-04 13:36:50 -0800535 autoconf= [IPV6]
536 See Documentation/networking/ipv6.txt.
537
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400538 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
539 Limit apic dumping. The parameter defines the maximal
540 number of local apics being dumped. Also it is possible
541 to set it to "all" by meaning -- no limit here.
542 Format: { 1 (default) | 2 | ... | all }.
543 The parameter valid if only apic=debug or
544 apic=verbose is specified.
545 Example: apic=debug show_lapic=all
546
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700548 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
551 Format: <io>,<irq>,<nodeID>
552
553 ataflop= [HW,M68k]
554
555 atarimouse= [HW,MOUSE] Atari Mouse
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
558 EzKey and similar keyboards
559
560 atkbd.reset= [HW] Reset keyboard during initialization
561
Randy Dunlapa9913042005-10-23 12:57:11 -0700562 atkbd.set= [HW] Select keyboard code set
563 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564
565 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
566 keyboards
567
568 atkbd.softraw= [HW] Choose between synthetic and real raw mode
569 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700570
571 atkbd.softrepeat= [HW]
572 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400574 audit= [KNL] Enable the audit sub-system
575 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500576 0 - kernel audit is disabled and can not be enabled
577 until the next reboot
578 unset - kernel audit is initialized but disabled and
579 will be fully enabled by the userspace auditd.
580 1 - kernel audit is initialized and partially enabled,
581 storing at most audit_backlog_limit messages in
582 RAM until it is fully enabled by the userspace
583 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400584 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400585
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400586 audit_backlog_limit= [KNL] Set the audit queue size limit.
587 Format: <int> (must be >=0)
588 Default: 64
589
Alex Thorlton1c532e02016-03-31 14:18:29 -0500590 bau= [X86_UV] Enable the BAU on SGI UV. The default
591 behavior is to disable the BAU (i.e. bau=0).
592 Format: { "0" | "1" }
593 0 - Disable the BAU.
594 1 - Enable the BAU.
595 unset - Disable the BAU.
596
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 baycom_epp= [HW,AX25]
598 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700599
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
601 Format: <io>,<mode>
602 See header of drivers/net/hamradio/baycom_par.c.
603
Randy Dunlapa9913042005-10-23 12:57:11 -0700604 baycom_ser_fdx= [HW,AX25]
605 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 Format: <io>,<irq>,<mode>[,<baud>]
607 See header of drivers/net/hamradio/baycom_ser_fdx.c.
608
Randy Dunlapa9913042005-10-23 12:57:11 -0700609 baycom_ser_hdx= [HW,AX25]
610 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 Format: <io>,<irq>,<mode>
612 See header of drivers/net/hamradio/baycom_ser_hdx.c.
613
Paul Gortmaker080506a2013-09-30 13:45:19 -0700614 blkdevparts= Manual partition parsing of block device(s) for
615 embedded devices based on command line input.
616 See Documentation/block/cmdline-partition.txt
617
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700618 boot_delay= Milliseconds to delay each printk during boot.
619 Values larger than 10 seconds (10000) are changed to
620 no delay (0).
621 Format: integer
622
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700623 bootmem_debug [KNL] Enable bootmem allocator debug messages.
624
Huang Yinga3e2acc2016-06-29 13:04:29 -0700625 bert_disable [ACPI]
626 Disable BERT OS support on buggy BIOSes.
627
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700629 bttv.radio= Most important insmod options are available as
630 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200632 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000634 bulk_remove=off [PPC] This parameter disables the use of the pSeries
635 firmware feature for flushing multiple hpte entries
636 at a time.
637
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 c101= [NET] Moxa C101 synchronous serial card
639
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700640 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 Sometimes CPU hardware bugs make them report the cache
642 size incorrectly. The kernel will attempt work arounds
643 to fix known problems, but for some CPUs it is not
644 possible to determine what the correct size should be.
645 This option provides an override for these situations.
646
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300647 ca_keys= [KEYS] This parameter identifies a specific key(s) on
648 the system trusted keyring to be used for certificate
649 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300650 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300651
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700652 cca= [MIPS] Override the kernel pages' cache coherency
653 algorithm. Accepted values range from 0 to 7
654 inclusive. See arch/mips/include/asm/pgtable-bits.h
655 for platform specific values (SB1, Loongson3 and
656 others).
657
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100658 ccw_timeout_log [S390]
659 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700660
Paul Menage8bab8dd2008-04-04 14:29:57 -0700661 cgroup_disable= [KNL] Disable a particular controller
662 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800663 The effects of cgroup_disable=foo are:
664 - foo isn't auto-mounted if you mount all cgroups in
665 a single hierarchy
666 - foo isn't visible as an individually mountable
667 subsystem
668 {Currently only "memory" controller deal with this and
669 cut the overhead, others just disable the usage. So
670 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700671
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500672 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
673 Format: { controller[,controller...] | "all" }
674 Like cgroup_disable, but only applies to cgroup v1;
675 the blacklisted controllers remain available in cgroup2.
676
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800677 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
678 Format: <string>
679 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800680 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800681
Linus Torvalds1da177e2005-04-16 15:20:36 -0700682 checkreqprot [SELINUX] Set initial checkreqprot flag value.
683 Format: { "0" | "1" }
684 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700685 0 -- check protection applied by kernel (includes
686 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 1 -- check protection requested by application.
688 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700689 Value can be changed at runtime via
690 /selinux/checkreqprot.
691
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100692 cio_ignore= [S390]
693 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700694 clk_ignore_unused
695 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700696 Prevents the clock framework from automatically gating
697 clocks that have not been explicitly enabled by a Linux
698 device driver but are enabled in hardware at reset or
699 by the bootloader/firmware. Note that this does not
700 force such clocks to be always-on nor does it reserve
701 those clocks in any way. This parameter is useful for
702 debug and development, but should not be needed on a
703 platform with proper driver support. For more
704 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100705
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700706 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700707 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200708 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700709 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200710 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 Format: { pit | tsc | cyclone | pmtmr }
712
John Stultz592913e2010-07-13 17:56:20 -0700713 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700714 Format: <string>
715 Override the default clocksource and use the clocksource
716 with the name specified.
717 Some clocksource names to choose from, depending on
718 the platform:
719 [all] jiffies (this is the base, fallback clocksource)
720 [ACPI] acpi_pm
721 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
722 pxa_timer,timer3,32k_counter,timer0_1
723 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700724 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700725 scx200_hrt on Geode; cyclone on IBM x440
726 [MIPS] MIPS
727 [PARISC] cr16
728 [S390] tod
729 [SH] SuperH
730 [SPARC64] tick
731 [X86-64] hpet,tsc
732
Will Deacon46fd5c62016-06-27 17:30:13 +0100733 clocksource.arm_arch_timer.evtstrm=
734 [ARM,ARM64]
735 Format: <bool>
736 Enable/disable the eventstream feature of the ARM
737 architected timer so that code using WFE-based polling
738 loops can be debugged more effectively on production
739 systems.
740
Scott Woodf6dc1572016-09-22 03:35:17 -0500741 clocksource.arm_arch_timer.fsl-a008585=
742 [ARM64]
743 Format: <bool>
744 Enable/disable the workaround of Freescale/NXP
745 erratum A-008585. This can be useful for KVM
746 guests, if the guest device tree doesn't show the
747 erratum. If unspecified, the workaround is
748 enabled based on the device tree.
749
Andi Kleenac72e782008-01-30 13:33:21 +0100750 clearcpuid=BITNUM [X86]
751 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100752 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800753 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100754 stable over kernel options, but the vendor specific
755 ones should be.
756 Also note that user programs calling CPUID directly
757 or using the feature without checking anything
758 will still see it. This just prevents it from
759 being used by the kernel or shown in /proc/cpuinfo.
760 Also note the kernel might malfunction if you disable
761 some critical bits.
762
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700763 cma=nn[MG]@[start[MG][-end[MG]]]
764 [ARM,X86,KNL]
765 Sets the size of kernel global memory area for
766 contiguous memory allocations and optionally the
767 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700768 memory allocations. A value of 0 disables CMA
769 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100770 include/linux/dma-contiguous.h
771
Robert Jennings14f966e2009-04-15 05:55:32 +0000772 cmo_free_hint= [PPC] Format: { yes | no }
773 Specify whether pages are marked as being inactive
774 when they are freed. This is used in CMO environments
775 to determine OS memory pressure for page stealing by
776 a hypervisor.
777 Default: yes
778
Marek Szyprowskic7909502011-12-29 13:09:51 +0100779 coherent_pool=nn[KMG] [ARM,KNL]
780 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200781 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100782
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530783 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100784 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100785 Range: 0 - 8192
786 Default: 64
787
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700789 Format:
790 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791
792 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
793 Format: <io>[,<irq>]
794
Randy Dunlapa9913042005-10-23 12:57:11 -0700795 com90xx= [HW,NET]
796 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 Format: <io>[,<irq>[,<memstart>]]
798
799 condev= [HW,S390] console device
800 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700801
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802 console= [KNL] Output console device and options.
803
804 tty<n> Use the virtual console device <n>.
805
806 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800807 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700808 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800809 the form "bbbbpnf", where "bbbb" is the baud rate,
810 "p" is parity ("n", "o", or "e"), "n" is number of
811 bits, and "f" is flow control ("r" for RTS or
812 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800814 See Documentation/serial-console.txt for more
815 information. See
816 Documentation/networking/netconsole.txt for an
817 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700819 uart[8250],io,<addr>[,options]
820 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900821 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400822 uart[8250],mmio32,<addr>[,options]
823 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 Start an early, polled-mode console on the 8250/16550
825 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400826 switching to the matching ttyS device later.
827 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900828 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
829 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
830 to be equivalent to 'mmio'. 'options' are specified in
831 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400832 the h/w is not re-initialized.
833
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500834 hvc<n> Use the hypervisor console device <n>. This is for
835 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700837 If the device connected to the port is not a TTY but a braille
838 device, prepend "brl," before the device type, for instance
839 console=brl,ttyS0
840 For now, only VisioBraille is supported.
841
Daniel Mackf324edc2009-06-16 15:33:52 -0700842 consoleblank= [KNL] The console blank (screen saver) timeout in
843 seconds. Defaults to 10*60 = 10mins. A value of 0
844 disables the blank timer.
845
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800846 coredump_filter=
847 [KNL] Change the default value for
848 /proc/<pid>/coredump_filter.
849 See also Documentation/filesystems/proc.txt.
850
Len Brown62027ae2011-04-01 18:13:10 -0400851 cpuidle.off=1 [CPU_IDLE]
852 disable the cpuidle sub-system
853
Len Brownd68921f2015-05-11 17:27:09 -0400854 cpu_init_udelay=N
855 [X86] Delay for N microsec between assert and de-assert
856 of APIC INIT to start processors. This delay occurs
857 on every CPU online, such as boot, and resume from suspend.
858 Default: 10000
859
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700861 Format:
862 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800864 crashkernel=size[KMG][@offset[KMG]]
865 [KNL] Using kexec, Linux can switch to a 'crash kernel'
866 upon panic. This parameter reserves the physical
867 memory region [offset, offset + size] for that kernel
868 image. If '@offset' is omitted, then a suitable offset
869 is selected automatically. Check
870 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700871
Bernhard Wallefb391592007-10-18 23:41:02 -0700872 crashkernel=range1:size1[,range2:size2,...][@offset]
873 [KNL] Same as above, but depends on the memory
874 in the running system. The syntax of range is
875 start-[end] where start and end are both
876 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800877 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700878
Yinghai Luadbc7422013-04-15 22:23:48 -0700879 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700880 [KNL, x86_64] range could be above 4G. Allow kernel
881 to allocate physical memory region from top, so could
882 be above 4G if system have more than 4G ram installed.
883 Otherwise memory region will be allocated below 4G, if
884 available.
885 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700886 crashkernel=size[KMG],low
887 [KNL, x86_64] range under 4G. When crashkernel=X,high
888 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700889 above 4G, that cause second kernel crash on system
890 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800891 requires at least 64M+32K low memory, also enough extra
892 low memory is needed to make sure DMA buffers for 32-bit
893 devices won't run out. Kernel would try to allocate at
894 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700895 This one let user to specify own low range under 4G
896 for second kernel instead.
897 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700898 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700899 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700900
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100901 cryptomgr.notests
902 [KNL] Disable crypto self-tests
903
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 cs89x0_dma= [HW,NET]
905 Format: <dma>
906
907 cs89x0_media= [HW,NET]
908 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700909
Randy Dunlapa9913042005-10-23 12:57:11 -0700910 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700911 See header of drivers/s390/block/dasd_devmap.c.
912
913 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
914 (one device per port)
915 Format: <port#>,<type>
916 See also Documentation/input/joystick-parport.txt
917
Thomas Renningera648ec02010-08-06 16:11:02 +0200918 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
919 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600920 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200921
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 debug [KNL] Enable kernel debugging (events log level).
923
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700924 debug_locks_verbose=
925 [KNL] verbose self-tests
926 Format=<0|1>
927 Print debugging info while doing the locking API
928 self-tests.
929 We default to 0 (no extra messages), setting it to
930 1 will print _a lot_ more information - normally
931 only useful to kernel developers.
932
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700933 debug_objects [KNL] Enable object debugging
934
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500935 no_debug_objects
936 [KNL] Disable object debugging
937
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800938 debug_guardpage_minorder=
939 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
940 parameter allows control of the order of pages that will
941 be intentionally kept free (and hence protected) by the
942 buddy allocator. Bigger value increase the probability
943 of catching random memory corruption, but reduce the
944 amount of memory for normal system use. The maximum
945 possible value is MAX_ORDER/2. Setting this parameter
946 to 1 or 2 should be enough to identify most random
947 memory corruption problems caused by bugs in kernel or
948 driver code when a CPU writes to (or reads from) a
949 random memory location. Note that there exists a class
950 of memory corruptions problems caused by buggy H/W or
951 F/W or by drivers badly programing DMA (basically when
952 memory is written at bus level and the CPU MMU is
953 bypassed) which are not detectable by
954 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
955 tracking down these problems.
956
Joonsoo Kim031bc572014-12-12 16:55:52 -0800957 debug_pagealloc=
958 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
959 parameter enables the feature at boot time. In
960 default, it is disabled. We can avoid allocating huge
961 chunk of memory for debug pagealloc if we don't enable
962 it at boot time and the system will work mostly same
963 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
964 on: enable the feature
965
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200966 debugpat [X86] Enable PAT debugging
967
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200968 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 Format: <area>[,<node>]
970 See also Documentation/networking/decnet.txt.
971
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700972 default_hugepagesz=
973 [same as hugepagesz=] The size of the default
974 HugeTLB page size. This is the size represented by
975 the legacy /proc/ hugepages APIs, used for SHM, and
976 default size when mounting hugetlbfs filesystems.
977 Defaults to the default architecture's huge page size
978 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700979
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980 dhash_entries= [KNL]
981 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700982
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000983 disable_1tb_segments [PPC]
984 Disables the use of 1TB hash page table segments. This
985 causes the kernel to fall back to 256MB segments which
986 can be useful when debugging issues that require an SLB
987 miss to occur.
988
Brian Haleyb0f83b22010-02-04 13:36:50 -0800989 disable= [IPV6]
990 See Documentation/networking/ipv6.txt.
991
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530992 disable_radix [PPC]
993 Disable RADIX MMU mode on POWER9
994
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900995 disable_cpu_apicid= [X86,APIC,SMP]
996 Format: <int>
997 The number of initial APIC ID for the
998 corresponding CPU to be disabled at boot,
999 mostly used for the kdump 2nd kernel to
1000 disable BSP to wake up multiple CPUs without
1001 causing system reset or hang due to sending
1002 INIT from AP to BSP.
1003
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +00001004 disable_ddw [PPC/PSERIES]
1005 Disable Dynamic DMA Window support. Use this if
1006 to workaround buggy firmware.
1007
Brian Haleyb0f83b22010-02-04 13:36:50 -08001008 disable_ipv6= [IPV6]
1009 See Documentation/networking/ipv6.txt.
1010
Yinghai Lu95ffa242008-04-29 03:52:33 -07001011 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -07001012 The kernel tries to adjust MTRR layout from continuous
1013 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001014 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -07001015
Yinghai Lu093af8d2008-01-30 13:33:32 +01001016 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +01001017 By default the kernel will trim any uncacheable
1018 memory out of your available memory pool based on
1019 MTRR settings. This parameter disables that behavior,
1020 possibly causing your machine to run very slowly.
1021
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301022 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001023 Disable PIN 1 of APIC timer
1024 Can be useful to work around chipset bugs.
1025
Prarit Bhargavace14c582015-08-25 13:34:53 -04001026 dis_ucode_ldr [X86] Disable the microcode loader.
1027
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001028 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1029 this option disables the debugging code at boot.
1030
1031 dma_debug_entries=<number>
1032 This option allows to tune the number of preallocated
1033 entries for DMA-API debugging code. One entry is
1034 required per DMA-API allocation. Use this if the
1035 DMA-API debugging code disables itself because the
1036 architectural default is too low.
1037
Joerg Roedel1745de52009-05-22 21:49:51 +02001038 dma_debug_driver=<driver_name>
1039 With this option the DMA-API debugging driver
1040 filter feature can be enabled at boot time. Just
1041 pass the driver to filter for as the parameter.
1042 The filter can be disabled or changed to another
1043 driver later using sysfs.
1044
Bob Paauwe96206e22015-08-27 10:04:13 -07001045 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1046 Broken monitors, graphic adapters, KVMs and EDIDless
1047 panels may send no or incorrect EDID data sets.
1048 This parameter allows to specify an EDID data sets
1049 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +01001050 Generic built-in EDID data sets are used, if one of
1051 edid/1024x768.bin, edid/1280x1024.bin,
1052 edid/1680x1050.bin, or edid/1920x1080.bin is given
1053 and no file with the same name exists. Details and
1054 instructions how to build your own EDID data are
1055 available in Documentation/EDID/HOWTO.txt. An EDID
1056 data set will only be used for a particular connector,
1057 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -07001058 name. Each connector may use a unique EDID data
1059 set by separating the files with a comma. An EDID
1060 data set with no connector name will be used for
1061 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +01001062
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063 dscc4.setup= [NET]
1064
Jim Cromie29e36c92012-04-27 14:30:41 -06001065 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1066 module.dyndbg[="val"]
1067 Enable debug messages at boot time. See
1068 Documentation/dynamic-debug-howto.txt for details.
1069
Dave Hansen8c3641e2015-06-07 11:37:02 -07001070 nompx [X86] Disables Intel Memory Protection Extensions.
1071 See Documentation/x86/intel_mpx.txt for more
1072 information about the feature.
1073
Dave Hansen06976942016-02-12 13:02:29 -08001074 nopku [X86] Disable Memory Protection Keys CPU feature found
1075 in some Intel CPUs.
1076
Borislav Petkovf29ba612015-03-27 16:15:18 +01001077 eagerfpu= [X86]
1078 on enable eager fpu restore
1079 off disable eager fpu restore
1080 auto selects the default scheme, which automatically
1081 enables eagerfpu restore for xsaveopt.
1082
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -07001083 module.async_probe [KNL]
1084 Enable asynchronous probe on this module.
1085
Mark Salter56aeeba2014-04-07 15:39:53 -07001086 early_ioremap_debug [KNL]
1087 Enable debug messages in early_ioremap support. This
1088 is useful for tracking down temporary early mappings
1089 which are not unmapped.
1090
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001091 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -05001092
Scott Wood5664f762015-09-14 19:54:07 -05001093 When used with no options, the early console is
1094 determined by the stdout-path property in device
1095 tree's chosen node.
1096
Scott Telfordc41251b2016-09-22 16:58:16 +01001097 cdns,<addr>[,options]
1098 Start an early, polled-mode console on a Cadence
1099 (xuartps) serial port at the specified address. Only
1100 supported option is baud rate. If baud rate is not
1101 specified, the serial port must already be setup and
1102 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +02001103
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001104 uart[8250],io,<addr>[,options]
1105 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001106 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001107 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001108 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001109 Start an early, polled-mode console on the 8250/16550
1110 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001111 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001112 (mmio) or 32-bit (mmio32 or mmio32be).
1113 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1114 to be equivalent to 'mmio'. 'options' are specified
1115 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001116 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001117
Rob Herring0d3c6732014-04-18 17:19:57 -05001118 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001119 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001120 Start an early, polled-mode console on a pl011 serial
1121 port at the specified address. The pl011 serial port
1122 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001123 yet supported. If 'mmio32' is specified, then only
1124 the driver will use only 32-bit accessors to read/write
1125 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001126
Andreas Färber736d5532016-03-06 12:21:24 +01001127 meson,<addr>
1128 Start an early, polled-mode console on a meson serial
1129 port at the specified address. The serial port must
1130 already be setup and configured. Options are not yet
1131 supported.
1132
Stephen Boyd0efe7292014-09-15 17:22:51 -07001133 msm_serial,<addr>
1134 Start an early, polled-mode console on an msm serial
1135 port at the specified address. The serial port
1136 must already be setup and configured. Options are not
1137 yet supported.
1138
1139 msm_serial_dm,<addr>
1140 Start an early, polled-mode console on an msm serial
1141 dm port at the specified address. The serial port
1142 must already be setup and configured. Options are not
1143 yet supported.
1144
Rob Herringd50d7262014-04-18 17:19:58 -05001145 smh Use ARM semihosting calls for early console.
1146
Tomasz Figab94ba032015-01-23 14:47:41 +01001147 s3c2410,<addr>
1148 s3c2412,<addr>
1149 s3c2440,<addr>
1150 s3c6400,<addr>
1151 s5pv210,<addr>
1152 exynos4210,<addr>
1153 Use early console provided by serial driver available
1154 on Samsung SoCs, requires selecting proper type and
1155 a correct base address of the selected UART port. The
1156 serial port must already be setup and configured.
1157 Options are not yet supported.
1158
Stefan Agner1d59b382015-10-17 00:45:55 -07001159 lpuart,<addr>
1160 lpuart32,<addr>
1161 Use early console provided by Freescale LP UART driver
1162 found on Freescale Vybrid and QorIQ LS1021A processors.
1163 A valid base address must be provided, and the serial
1164 port must already be setup and configured.
1165
Wilson Ding30530792016-02-16 19:14:53 +01001166 armada3700_uart,<addr>
1167 Start an early, polled-mode console on the
1168 Armada 3700 serial port at the specified
1169 address. The serial port must already be setup
1170 and configured. Options are not yet supported.
1171
Finn Thain7913ad12014-04-12 23:48:56 +10001172 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001174 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001175 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001177 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001178 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001179 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001180 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181
Dave Hansen147ea092013-04-10 14:03:38 -07001182 earlyprintk is useful when the kernel crashes before
1183 the normal console is initialized. It is not enabled by
1184 default because it has some cosmetic problems.
1185
Randy Dunlapa9913042005-10-23 12:57:11 -07001186 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001187 takes over.
1188
Matt Fleming72548e82013-10-04 09:36:56 +01001189 Only one of vga, efi, serial, or usb debug port can
1190 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191
Dave Hansen147ea092013-04-10 14:03:38 -07001192 Currently only ttyS0 and ttyS1 may be specified by
1193 name. Other I/O ports may be explicitly specified
1194 on some architectures (x86 and arm at least) by
1195 replacing ttySn with an I/O port address, like this:
1196 earlyprintk=serial,0x1008,115200
1197 You can find the port for a given device in
1198 /proc/tty/driver/serial:
1199 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200
1201 Interaction with the standard serial driver is not
1202 very good.
1203
Matt Fleming72548e82013-10-04 09:36:56 +01001204 The VGA and EFI output is eventually overwritten by
1205 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001206
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001207 The xen output can only be used by Xen PV guests.
1208
Chen, Gongc700f012013-12-06 01:17:08 -05001209 edac_report= [HW,EDAC] Control how to report EDAC event
1210 Format: {"on" | "off" | "force"}
1211 on: enable EDAC to report H/W event. May be overridden
1212 by other higher priority error reporting module.
1213 off: disable H/W event reporting through EDAC.
1214 force: enforce the use of EDAC to report H/W event.
1215 default: on.
1216
Jason Wessel97311912010-05-20 21:04:30 -05001217 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1218 ekgdboc=kbd
1219
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001220 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001221 the boot argument: earlyprintk=vga
1222
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001224 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001225
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001226 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001227 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001228 old_map [X86-64]: switch to the old ioremap-based EFI
1229 runtime services mapping. 32-bit still uses this one by
1230 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001231 nochunk: disable reading files in "chunks" in the EFI
1232 boot stub, as chunking can cause problems with some
1233 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001234 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001235 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001236
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001237 efi_no_storage_paranoia [EFI; X86]
1238 Using this parameter you can use more than 50% of
1239 your efi variable storage. Use this parameter only if
1240 you are really sure that your UEFI does sane gc and
1241 fulfills the spec otherwise your board may brick.
1242
Taku Izumi0f96a992015-09-30 23:01:56 +09001243 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1244 Add arbitrary attribute to specific memory range by
1245 updating original EFI memory map.
1246 Region of memory which aa attribute is added to is
1247 from ss to ss+nn.
1248 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1249 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1250 attribute is added to range 0x100000000-0x180000000 and
1251 0x10a0000000-0x1120000000.
1252
1253 Using this parameter you can do debugging of EFI memmap
1254 related feature. For example, you can do debugging of
1255 Address Range Mirroring feature even if your box
1256 doesn't support it.
1257
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001258 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1259 that is to be dynamically loaded by Linux. If there are
1260 multiple variables with the same name but with different
1261 vendor GUIDs, all of them will be loaded. See
1262 Documentation/acpi/ssdt-overlays.txt for details.
1263
1264
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 eisa_irq_edge= [PARISC,HW]
1266 See header of drivers/parisc/eisa.c.
1267
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001268 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001270 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271
1272 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001273 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001274 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001275 Documentation/block/deadline-iosched.txt for details.
1276
Michael Holzheud3bf37952011-10-30 15:16:37 +01001277 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001278 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001279 image elf header and optionally the size. Generally
1280 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001281 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001283 enable_mtrr_cleanup [X86]
1284 The kernel tries to adjust MTRR layout from continuous
1285 to discrete, to make X server driver able to add WB
1286 entry later. This parameter enables that.
1287
Randy Dunlapca1eda22009-05-06 16:02:58 -07001288 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001289 Enable PIN 1 of APIC timer
1290 Can be useful to work around chipset bugs
1291 (in particular on some ATI chipsets).
1292 The kernel tries to set a reasonable default.
1293
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294 enforcing [SELINUX] Set initial enforcing status.
1295 Format: {"0" | "1"}
1296 See security/selinux/Kconfig help text.
1297 0 -- permissive (log only, no denials).
1298 1 -- enforcing (deny and log).
1299 Default value is 0.
1300 Value can be changed at runtime via /selinux/enforce.
1301
Huang Yinga08f82d2010-05-18 14:35:21 +08001302 erst_disable [ACPI]
1303 Disable Error Record Serialization Table (ERST)
1304 support.
1305
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 ether= [HW,NET] Ethernet cards parameters
1307 This option is obsoleted by the "netdev=" option, which
1308 has equivalent usage. See its documentation for details.
1309
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001310 evm= [EVM]
1311 Format: { "fix" }
1312 Permit 'security.evm' to be updated regardless of
1313 current integrity status.
1314
Akinobu Mitade1ba092006-12-08 02:39:42 -08001315 failslab=
1316 fail_page_alloc=
1317 fail_make_request=[KNL]
1318 General fault injection mechanism.
1319 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001320 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001321
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001323 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324
Alex Chiangf13ae302008-05-08 14:03:23 -06001325 force_pal_cache_flush
1326 [IA-64] Avoid check_sal_cache_flush which may hang on
1327 buggy SAL_CACHE_FLUSH implementations. Using this
1328 parameter will force ia64_sal_cache_flush to call
1329 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1330
Chris Bainbridge69f23662014-03-07 18:40:42 +07001331 forcepae [X86-32]
1332 Forcefully enable Physical Address Extension (PAE).
1333 Many Pentium M systems disable PAE but may have a
1334 functionally usable PAE implementation.
1335 Warning: use of this parameter will taint the kernel
1336 and may cause unknown problems.
1337
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001338 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001339 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001340 as early as possible in order to facilitate early
1341 boot debugging.
1342
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001343 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001344 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001345 If no parameter is passed, ftrace will dump
1346 buffers of all CPUs, but if you pass orig_cpu, it will
1347 dump only the buffer of the CPU that triggered the
1348 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001349
1350 ftrace_filter=[function-list]
1351 [FTRACE] Limit the functions traced by the function
1352 tracer at boot up. function-list is a comma separated
1353 list of functions. This list can be changed at run
1354 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001355 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001356
1357 ftrace_notrace=[function-list]
1358 [FTRACE] Do not trace the functions specified in
1359 function-list. This list can be changed at run time
1360 by the set_ftrace_notrace file in the debugfs
1361 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001362
Stefan Assmann369bc182009-10-12 22:17:21 +02001363 ftrace_graph_filter=[function-list]
1364 [FTRACE] Limit the top level callers functions traced
1365 by the function graph tracer at boot up.
1366 function-list is a comma separated list of functions
1367 that can be changed at run time by the
1368 set_graph_function file in the debugfs tracing directory.
1369
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001370 ftrace_graph_notrace=[function-list]
1371 [FTRACE] Do not trace from the functions specified in
1372 function-list. This list is a comma separated list of
1373 functions that can be changed at run time by the
1374 set_graph_notrace file in the debugfs tracing directory.
1375
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376 gamecon.map[2|3]=
1377 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1378 support via parallel port (up to 5 devices per port)
1379 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1380 See also Documentation/input/joystick-parport.txt
1381
1382 gamma= [HW,DRM]
1383
Yinghai Luaaf23042008-01-30 13:33:09 +01001384 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1385 Format: off | on
1386 default: on
1387
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001388 gcov_persist= [GCOV] When non-zero (default), profiling data for
1389 kernel modules is saved and remains accessible via
1390 debugfs, even when the module is unloaded/reloaded.
1391 When zero, profiling data is discarded and associated
1392 debugfs files are removed at module unload time.
1393
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001395 invalid Protective MBR to be treated as GPT. If the
1396 primary GPT is corrupted, it enables the backup/alternate
1397 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001399 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1400 the "Enable 0" bit of the configuration register.
1401 Format: 0 | 1
1402 Default: 0
1403 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1404 the "Enable 0" bit of the configuration register.
1405 Format: 0 | 1
1406 Default: 0
1407 grcan.select= [HW] Select which physical interface to use.
1408 Format: 0 | 1
1409 Default: 0
1410 grcan.txsize= [HW] Sets the size of the tx buffer.
1411 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1412 Default: 1024
1413 grcan.rxsize= [HW] Sets the size of the rx buffer.
1414 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1415 Default: 1024
1416
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001417 gpio-mockup.gpio_mockup_ranges
1418 [HW] Sets the ranges of gpiochip of for this device.
1419 Format: <start1>,<end1>,<start2>,<end2>...
1420
Jiri Kosina55537872015-11-05 18:44:41 -08001421 hardlockup_all_cpu_backtrace=
1422 [KNL] Should the hard-lockup detector generate
1423 backtraces on all cpus.
1424 Format: <integer>
1425
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 hashdist= [KNL,NUMA] Large hashes allocated during boot
1427 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001428 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001429 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430
1431 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1432
1433 hd= [EIDE] (E)IDE hard drive subsystem geometry
1434 Format: <cyl>,<head>,<sect>
1435
Huang Yingea8c0712010-05-18 14:35:15 +08001436 hest_disable [ACPI]
1437 Disable Hardware Error Source Table (HEST) support;
1438 corresponding firmware-first mode error processing
1439 logic will be disabled.
1440
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1442 size of <nn>. This works even on boxes that have no
1443 highmem otherwise. This also works to reduce highmem
1444 size on bigger boxes.
1445
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001446 highres= [KNL] Enable/disable high resolution timer mode.
1447 Valid parameters: "on", "off"
1448 Default: "on"
1449
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450 hisax= [HW,ISDN]
1451 See Documentation/isdn/README.HiSax.
1452
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001453 hlt [BUGS=ARM,SH]
1454
1455 hpet= [X86-32,HPET] option to control HPET usage
1456 Format: { enable (default) | disable | force |
1457 verbose }
1458 disable: disable HPET and use PIT instead
1459 force: allow force enabled of undocumented chips (ICH4,
1460 VIA, nVidia)
1461 verbose: show contents of HPET registers during setup
1462
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001463 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1464 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1465
Andi Kleenb4718e62008-07-23 21:27:51 -07001466 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1467 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001468 On x86-64 and powerpc, this option can be specified
1469 multiple times interleaved with hugepages= to reserve
1470 huge pages of different sizes. Valid pages sizes on
1471 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001472 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001473
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001474 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1475 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001476 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1477 If specified, z/VM IUCV HVC accepts connections
1478 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001479
James Hoganfdabf522012-10-09 11:00:27 +01001480 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1481 hardware thread id mappings.
1482 Format: <cpu>:<hwthread>
1483
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001484 keep_bootcon [KNL]
1485 Do not unregister boot console at start. This is only
1486 useful for debugging when something happens in the window
1487 between unregistering the boot console and initializing
1488 the real console.
1489
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001490 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001491 or register an additional I2C bus that is not
1492 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001493 Format:
1494 <bus_id>,<clkrate>
1495
Jiri Kosina36d95732008-10-06 02:51:09 -04001496 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001497 i8042.unmask_kbd_data
1498 [HW] Enable printing of interrupt data from the KBD port
1499 (disabled by default, and as a pre-condition
1500 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001502 i8042.dumbkbd [HW] Pretend that controller can only read data from
1503 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 (Don't attempt to blink the leds)
1505 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001506 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001507 i8042.noloop [HW] Disable the AUX Loopback command while probing
1508 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001510 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1512 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001513 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e1922016-10-01 12:07:35 -07001514 i8042.reset [HW] Reset the controller during init, cleanup and
1515 suspend-to-ram transitions, only during s2r
1516 transitions, or never reset
1517 Format: { 1 | Y | y | 0 | N | n }
1518 1, Y, y: always reset controller
1519 0, N, n: don't ever reset controller
1520 Default: only on s2r transitions on x86; most other
1521 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001523 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524
1525 i810= [HW,DRM]
1526
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001527 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1528 indicates that the driver is running on unsupported
1529 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1531 does not match list of supported models.
1532 i8k.power_status
1533 [HW] Report power status in /proc/i8k
1534 (disabled by default)
1535 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1536 capability is set.
1537
Carsten Emde4dca20e2012-03-15 15:56:26 +01001538 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001539 [DRM] Invert the sense of the variable that is used to
1540 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001541 brightness value of 0 indicates backlight switched off,
1542 and the maximum of the brightness value sets the backlight
1543 to maximum brightness. If this parameter is set to 0
1544 (default) and the machine requires it, or this parameter
1545 is set to 1, a brightness value of 0 sets the backlight
1546 to maximum brightness, and the maximum of the brightness
1547 value switches the backlight off.
1548 -1 -- never invert brightness
1549 0 -- machine default
1550 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001551
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 icn= [HW,ISDN]
1553 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1554
David Fries0af80c02009-02-25 20:28:21 +01001555 ide-core.nodma= [HW] (E)IDE subsystem
1556 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001557 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1558 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001559 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001561 ide-generic.probe-mask= [HW] (E)IDE subsystem
1562 Format: <int>
1563 Probe mask for legacy ISA IDE ports. Depending on
1564 platform up to 6 ports are supported, enabled by
1565 setting corresponding bits in the mask to 1. The
1566 default value is 0x0, which has a special meaning.
1567 On systems that have PCI, it triggers scanning the
1568 PCI bus for the first and the second port, which
1569 are then probed. On systems without PCI the value
1570 of 0x0 enables probing the two first ports as if it
1571 was 0x3.
1572
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001573 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1574 Claim all unknown PCI IDE storage controllers.
1575
Andi Kleenf039b752007-05-02 19:27:12 +02001576 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001577 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001578 Poll forces a polling idle loop that can slightly
1579 improve the performance of waking up a idle CPU, but
1580 will use a lot of power and make the system run hot.
1581 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001582 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001583 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001584 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001585
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001586 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1587 Format: { strict | legacy | 2008 | relaxed }
1588 Default: strict
1589
1590 Choose which programs will be accepted for execution
1591 based on the IEEE 754 NaN encoding(s) supported by
1592 the FPU and the NaN encoding requested with the value
1593 of an ELF file header flag individually set by each
1594 binary. Hardware implementations are permitted to
1595 support either or both of the legacy and the 2008 NaN
1596 encoding mode.
1597
1598 Available settings are as follows:
1599 strict accept binaries that request a NaN encoding
1600 supported by the FPU
1601 legacy only accept legacy-NaN binaries, if supported
1602 by the FPU
1603 2008 only accept 2008-NaN binaries, if supported
1604 by the FPU
1605 relaxed accept any binaries regardless of whether
1606 supported by the FPU
1607
1608 The FPU emulator is always able to support both NaN
1609 encodings, so if no FPU hardware is present or it has
1610 been disabled with 'nofpu', then the settings of
1611 'legacy' and '2008' strap the emulator accordingly,
1612 'relaxed' straps the emulator for both legacy-NaN and
1613 2008-NaN, whereas 'strict' enables legacy-NaN only on
1614 legacy processors and both NaN encodings on MIPS32 or
1615 MIPS64 CPUs.
1616
1617 The setting for ABS.fmt/NEG.fmt instruction execution
1618 mode generally follows that for the NaN encoding,
1619 except where unsupported by hardware.
1620
Ingo Molnar792908222006-12-06 20:40:51 -08001621 ignore_loglevel [KNL]
1622 Ignore loglevel setting - this will print /all/
1623 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001624 We also add it as printk module parameter, so users
1625 could change it dynamically, usually by
1626 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001627
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001628 ignore_rlimit_data
1629 Ignore RLIMIT_DATA setting for data mappings,
1630 print warning at first misuse. Can be changed via
1631 /sys/module/kernel/parameters/ignore_rlimit_data.
1632
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 ihash_entries= [KNL]
1634 Set number of hash buckets for inode cache.
1635
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001636 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001637 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001638 default: "enforce"
1639
Mimi Zohar07f6a792011-03-09 22:25:48 -05001640 ima_appraise_tcb [IMA]
1641 The builtin appraise policy appraises all files
1642 owned by uid=0.
1643
Mimi Zohar3323eec92009-02-04 09:06:58 -05001644 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001645 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1646 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001647 default: "sha1"
1648
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001649 The list of supported hash algorithms is defined
1650 in crypto/hash_info.h.
1651
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001652 ima_policy= [IMA]
1653 The builtin measurement policy to load during IMA
1654 setup. Specyfing "tcb" as the value, measures all
1655 programs exec'd, files mmap'd for exec, and all files
1656 opened with the read mode bit set by either the
1657 effective uid (euid=0) or uid=0.
1658 Format: "tcb"
1659
1660 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001661 Load a policy which meets the needs of the Trusted
1662 Computing Base. This means IMA will measure all
1663 programs exec'd, files mmap'd for exec, and all files
1664 opened for read by uid=0.
1665
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001666 ima_template= [IMA]
1667 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001668 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001669 Default: "ima-ng"
1670
Roberto Sassuc2426d22014-10-13 14:08:42 +02001671 ima_template_fmt=
1672 [IMA] Define a custom template format.
1673 Format: { "field1|...|fieldN" }
1674
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001675 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1676 Format: <min_file_size>
1677 Set the minimal file size for using asynchronous hash.
1678 If left unspecified, ahash usage is disabled.
1679
1680 ahash performance varies for different data sizes on
1681 different crypto accelerators. This option can be used
1682 to achieve the best performance for a particular HW.
1683
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001684 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1685 Format: <bufsize>
1686 Set hashing buffer size. Default: 4k.
1687
1688 ahash performance varies for different chunk sizes on
1689 different crypto accelerators. This option can be used
1690 to achieve best performance for particular HW.
1691
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 init= [KNL]
1693 Format: <full_path>
1694 Run specified binary instead of /sbin/init as init
1695 process.
1696
1697 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1698 for working out where the kernel is dying during
1699 startup.
1700
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001701 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1702 initcall functions. Useful for debugging built-in
1703 modules and initcalls.
1704
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705 initrd= [BOOT] Specify the location of the initial ramdisk
1706
Dave Hansenacd547b2016-07-29 09:30:21 -07001707 init_pkru= [x86] Specify the default memory protection keys rights
1708 register contents for all processes. 0x55555554 by
1709 default (disallow access to all but pkey 0). Can
1710 override in debugfs after boot.
1711
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1713 Format: <irq>
1714
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001715 int_pln_enable [x86] Enable power limit notification interrupt
1716
Mimi Zohard726d8d2013-03-18 14:48:02 -04001717 integrity_audit=[IMA]
1718 Format: { "0" | "1" }
1719 0 -- basic integrity auditing messages. (Default)
1720 1 -- additional integrity auditing messages.
1721
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001722 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001723 on
1724 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001725 off
1726 Disable intel iommu driver.
1727 igfx_off [Default Off]
1728 By default, gfx is mapped as normal device. If a gfx
1729 device has a dedicated DMAR unit, the DMAR unit is
1730 bypassed by not enabling DMAR with this option. In
1731 this case, gfx device will use physical address for
1732 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001733 forcedac [x86_64]
1734 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001735 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001736 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001737 than 32-bit addressing. The default is to look
1738 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001739 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001740 strict [Default Off]
1741 With this option on every unmap_single operation will
1742 result in a hardware IOTLB flush operation as opposed
1743 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001744 sp_off [Default Off]
1745 By default, super page will be supported if Intel IOMMU
1746 has the capability. With this option, super page will
1747 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001748 ecs_off [Default Off]
1749 By default, extended context tables will be supported if
1750 the hardware advertises that it has support both for the
1751 extended tables themselves, and also PASID support. With
1752 this option set, extended tables will not be used even
1753 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001754
1755 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1756 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001757 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001758
Dirk Brandewie6be26492013-02-15 22:55:10 +01001759 intel_pstate= [X86]
1760 disable
1761 Do not enable intel_pstate as the default
1762 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001763 force
1764 Enable intel_pstate on systems that prohibit it by default
1765 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1766 instead of acpi-cpufreq may disable platform features, such
1767 as thermal controls and power capping, that rely on ACPI
1768 P-States information being indicated to OSPM and therefore
1769 should be used with caution. This option does not work with
1770 processors that aren't supported by the intel_pstate driver
1771 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001772 no_hwp
1773 Do not enable hardware P state control (HWP)
1774 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001775 hwp_only
1776 Only load intel_pstate on systems which support
1777 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001778 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001779 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1780 Description Table, specifies preferred power management
1781 profile as "Enterprise Server" or "Performance Server",
1782 then this feature is turned on by default.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001783
Chris Wrightd1423d52010-07-20 11:06:49 -07001784 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001785 on enable Interrupt Remapping (default)
1786 off disable Interrupt Remapping
1787 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001788 no_x2apic_optout
1789 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001790 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001791
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001792 iomem= Disable strict checking of access to MMIO memory
1793 strict regions from userspace.
1794 relaxed
1795
1796 iommu= [x86]
1797 off
1798 force
1799 noforce
1800 biomerge
1801 panic
1802 nopanic
1803 merge
1804 nomerge
1805 forcesac
1806 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001807 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001808 nobypass [PPC/POWERNV]
1809 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001810
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001811
1812 io7= [HW] IO7 for Marvel based alpha systems
1813 See comment before marvel_specify_io7 in
1814 arch/alpha/kernel/core_marvel.c.
1815
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301816 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001817 0x80
1818 Standard port 0x80 based delay
1819 0xed
1820 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001821 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001822 Simple two microseconds delay
1823 none
1824 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001825
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001827 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001829 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001830 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001831
Alan Cox200803d2005-06-28 20:45:18 -07001832 irqfixup [HW]
1833 When an interrupt is not handled search all handlers
1834 for it. Intended to get systems with badly broken
1835 firmware running.
1836
1837 irqpoll [HW]
1838 When an interrupt is not handled search all handlers
1839 for it. Also check all handlers each timer
1840 interrupt. Intended to get systems with badly broken
1841 firmware running.
1842
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001844 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845
1846 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001847 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001848
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 This option can be used to specify one or more CPUs
1850 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001851 algorithms. You can move a process onto or off an
1852 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001853 <cpu number> begins at 0 and the maximum value is
1854 "number of CPUs in system - 1".
1855
1856 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001857 alternative -- manually setting the CPU mask of all
1858 tasks in the system -- can cause problems and
1859 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860
Randy Dunlapa9913042005-10-23 12:57:11 -07001861 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001862
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001863 ivrs_ioapic [HW,X86_64]
1864 Provide an override to the IOAPIC-ID<->DEVICE-ID
1865 mapping provided in the IVRS ACPI table. For
1866 example, to map IOAPIC-ID decimal 10 to
1867 PCI device 00:14.0 write the parameter as:
1868 ivrs_ioapic[10]=00:14.0
1869
1870 ivrs_hpet [HW,X86_64]
1871 Provide an override to the HPET-ID<->DEVICE-ID
1872 mapping provided in the IVRS ACPI table. For
1873 example, to map HPET-ID decimal 0 to
1874 PCI device 00:14.0 write the parameter as:
1875 ivrs_hpet[0]=00:14.0
1876
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001877 ivrs_acpihid [HW,X86_64]
1878 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1879 mapping provided in the IVRS ACPI table. For
1880 example, to map UART-HID:UID AMD0020:0 to
1881 PCI device 00:14.5 write the parameter as:
1882 ivrs_acpihid[00:14.5]=AMD0020:0
1883
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884 js= [HW,JOY] Analog joystick
1885 See Documentation/input/joystick.txt.
1886
Kees Cook65fe9352016-06-13 15:10:02 -07001887 nokaslr [KNL]
1888 When CONFIG_RANDOMIZE_BASE is set, this disables
1889 kernel and module base offset ASLR (Address Space
1890 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001891
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001892 keepinitrd [HW,ARM]
1893
Taku Izumi342332e2016-03-15 14:55:22 -07001894 kernelcore= [KNL,X86,IA-64,PPC]
1895 Format: nn[KMGTPE] | "mirror"
1896 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001897 specifies the amount of memory usable by the kernel
1898 for non-movable allocations. The requested amount is
1899 spread evenly throughout all nodes in the system. The
1900 remaining memory in each node is used for Movable
1901 pages. In the event, a node is too small to have both
1902 kernelcore and Movable pages, kernelcore pages will
1903 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001904 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001905 allocation of pages that may be reclaimed or moved
1906 by the page migration subsystem. This means that
1907 HugeTLB pages may not be allocated from this zone.
1908 Note that allocations like PTEs-from-HighMem still
1909 use the HighMem zone if it exists, and the Normal
1910 zone if it does not.
1911
Taku Izumi342332e2016-03-15 14:55:22 -07001912 Instead of specifying the amount of memory (nn[KMGTPE]),
1913 you can specify "mirror" option. In case "mirror"
1914 option is specified, mirrored (reliable) memory is used
1915 for non-movable allocations and remaining memory is used
1916 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1917 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1918 time.
1919
Jason Wessel4fe1da42010-05-20 21:04:31 -05001920 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1921 Format: <Controller#>[,poll interval]
1922 The controller # is the number of the ehci usb debug
1923 port as it is probed via PCI. The poll interval is
1924 optional and is the number seconds in between
1925 each poll cycle to the debug port in case you need
1926 the functionality for interrupting the kernel with
1927 gdb or control-c on the dbgp connection. When
1928 not using this parameter you use sysrq-g to break into
1929 the kernel debugger.
1930
Jason Wessel84c08fd2010-05-20 21:04:24 -05001931 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001932 Requires a tty driver that supports console polling,
1933 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001934 Serial only format: <serial_device>[,baud]
1935 keyboard only format: kbd
1936 keyboard and serial format: kbd,<serial_device>[,baud]
1937 Optional Kernel mode setting:
1938 kms, kbd format: kms,kbd
1939 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001940
Jason Wessel84c08fd2010-05-20 21:04:24 -05001941 kgdbwait [KGDB] Stop kernel execution and enter the
1942 kernel debugger at the earliest opportunity.
1943
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001944 kmac= [MIPS] korina ethernet MAC address.
1945 Configure the RouterBoard 532 series on-chip
1946 Ethernet adapter MAC address.
1947
Catalin Marinas04f70332009-06-11 13:22:39 +01001948 kmemleak= [KNL] Boot-time kmemleak enable/disable
1949 Valid arguments: on, off
1950 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001951 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1952 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001953
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001954 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1955 Valid arguments: 0, 1, 2
1956 kmemcheck=0 (disabled)
1957 kmemcheck=1 (enabled)
1958 kmemcheck=2 (one-shot mode)
1959 Default: 2 (one-shot mode)
1960
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301961 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001962 in oops dumps.
1963
Andre Przywarafef07aa2009-07-10 14:20:35 +02001964 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1965 Default is 0 (don't ignore, but inject #GP)
1966
Xiao Guangronga182d872010-09-20 22:17:48 +08001967 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1968 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001969 Default is 0 (off)
1970
Andre Przywarafef07aa2009-07-10 14:20:35 +02001971 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001972 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001973
1974 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1975 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001976 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001977
Andre Przywarafef07aa2009-07-10 14:20:35 +02001978 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1979 (virtualized MMU) support on capable Intel chips.
1980 Default is 1 (enabled)
1981
1982 kvm-intel.emulate_invalid_guest_state=
1983 [KVM,Intel] Enable emulation of invalid guest states
1984 Default is 0 (disabled)
1985
1986 kvm-intel.flexpriority=
1987 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1988 Default is 1 (enabled)
1989
Sasha Levine1a72ae2011-08-09 14:28:35 +03001990 kvm-intel.nested=
1991 [KVM,Intel] Enable VMX nesting (nVMX).
1992 Default is 0 (disabled)
1993
Andre Przywarafef07aa2009-07-10 14:20:35 +02001994 kvm-intel.unrestricted_guest=
1995 [KVM,Intel] Disable unrestricted guest feature
1996 (virtualized real and unpaged mode) on capable
1997 Intel chips. Default is 1 (enabled)
1998
1999 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2000 feature (tagged TLBs) on capable Intel chips.
2001 Default is 1 (enabled)
2002
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003 l2cr= [PPC]
2004
Robert Brosea78bfbf2008-03-29 07:20:23 +11002005 l3cr= [PPC]
2006
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002007 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07002008 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002009
Suresh Siddha279f1462012-10-22 14:37:58 -07002010 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2011 value for LAPIC timer one-shot implementation. Default
2012 back to the programmable timer unit in the LAPIC.
2013
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302014 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002015 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01002016
FD Camifcb71f62008-01-06 19:08:56 +01002017 libata.dma= [LIBATA] DMA control
2018 libata.dma=0 Disable all PATA and SATA DMA
2019 libata.dma=1 PATA and SATA Disk DMA only
2020 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07002021 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01002022 Combinations also work, so libata.dma=3 enables DMA
2023 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07002024
Michael Prokop20308872009-08-06 00:14:10 +02002025 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2026 libata.ignore_hpa=0 keep BIOS limits (default)
2027 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01002028
Dave Jones78e70c22007-09-27 11:50:13 -04002029 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2030 when set.
2031 Format: <int>
2032
Tejun Heo33267322008-02-13 09:15:09 +09002033 libata.force= [LIBATA] Force configurations. The format is comma
2034 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02002035 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09002036 matching port, link or device. Basically, it matches
2037 the ATA ID string printed on console by libata. If
2038 the whole ID part is omitted, the last PORT and DEVICE
2039 values are used. If ID hasn't been specified yet, the
2040 configuration applies to all ports, links and devices.
2041
2042 If only DEVICE is omitted, the parameter applies to
2043 the port and all links and devices behind it. DEVICE
2044 number of 0 either selects the first device or the
2045 first fan-out link behind PMP device. It does not
2046 select the host link. DEVICE number of 15 selects the
2047 host link and device attached to it.
2048
2049 The VAL specifies the configuration to force. As long
2050 as there's no ambiguity shortcut notation is allowed.
2051 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2052 The following configurations can be forced.
2053
2054 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2055 Any ID with matching PORT is used.
2056
2057 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2058
2059 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2060 udma[/][16,25,33,44,66,100,133] notation is also
2061 allowed.
2062
2063 * [no]ncq: Turn on or off NCQ.
2064
Martin K. Petersend7b16e42015-05-04 21:54:18 -04002065 * [no]ncqtrim: Turn off queued DSM TRIM.
2066
Tejun Heo05944bd2008-08-13 20:19:09 +09002067 * nohrst, nosrst, norst: suppress hard, soft
2068 and both resets.
2069
Dan Williamsca6d43b2012-06-21 23:41:41 -07002070 * rstonce: only attempt one reset during
2071 hot-unplug link recovery
2072
Tejun Heo43c9c592010-05-23 12:59:11 +02002073 * dump_id: dump IDENTIFY data.
2074
Vincent Pelletier966fbe12013-05-21 22:30:58 +02002075 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2076
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08002077 * disable: Disable this device.
2078
Tejun Heo33267322008-02-13 09:15:09 +09002079 If there are multiple matching configurations changing
2080 the same attribute, the last one is used.
2081
Yinghai Lu95f72d12010-07-12 14:36:09 +10002082 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002083
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002085 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002087 lockd.nlm_grace_period=P [NFS] Assign grace period.
2088 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002090 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2091 Format: <integer>
2092
2093 lockd.nlm_timeout=T [NFS] Assign timeout value.
2094 Format: <integer>
2095
2096 lockd.nlm_udpport=M [NFS] Assign UDP port.
2097 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002099 locktorture.nreaders_stress= [KNL]
2100 Set the number of locking read-acquisition kthreads.
2101 Defaults to being automatically set based on the
2102 number of online CPUs.
2103
2104 locktorture.nwriters_stress= [KNL]
2105 Set the number of locking write-acquisition kthreads.
2106
2107 locktorture.onoff_holdoff= [KNL]
2108 Set time (s) after boot for CPU-hotplug testing.
2109
2110 locktorture.onoff_interval= [KNL]
2111 Set time (s) between CPU-hotplug operations, or
2112 zero to disable CPU-hotplug testing.
2113
2114 locktorture.shuffle_interval= [KNL]
2115 Set task-shuffle interval (jiffies). Shuffling
2116 tasks allows some CPUs to go into dyntick-idle
2117 mode during the locktorture test.
2118
2119 locktorture.shutdown_secs= [KNL]
2120 Set time (s) after boot system shutdown. This
2121 is useful for hands-off automated testing.
2122
2123 locktorture.stat_interval= [KNL]
2124 Time (s) between statistics printk()s.
2125
2126 locktorture.stutter= [KNL]
2127 Time (s) to stutter testing, for example,
2128 specifying five seconds causes the test to run for
2129 five seconds, wait for five seconds, and so on.
2130 This tests the locking primitive's ability to
2131 transition abruptly to and from idle.
2132
2133 locktorture.torture_runnable= [BOOT]
2134 Start locktorture running at boot time.
2135
2136 locktorture.torture_type= [KNL]
2137 Specify the locking implementation to test.
2138
2139 locktorture.verbose= [KNL]
2140 Enable additional printk() statements.
2141
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2143 Format: <irq>
2144
2145 loglevel= All Kernel Messages with a loglevel smaller than the
2146 console loglevel will be printed to the console. It can
2147 also be changed with klogd or other programs. The
2148 loglevels are defined as follows:
2149
2150 0 (KERN_EMERG) system is unusable
2151 1 (KERN_ALERT) action must be taken immediately
2152 2 (KERN_CRIT) critical conditions
2153 3 (KERN_ERR) error conditions
2154 4 (KERN_WARNING) warning conditions
2155 5 (KERN_NOTICE) normal but significant condition
2156 6 (KERN_INFO) informational
2157 7 (KERN_DEBUG) debug-level messages
2158
Randy Dunlapc756d082011-02-20 20:08:35 -08002159 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002160 in bytes. n must be a power of two and greater
2161 than the minimal size. The minimal size is defined
2162 by LOG_BUF_SHIFT kernel config parameter. There is
2163 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2164 that allows to increase the default size depending on
2165 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166
Randy Dunlapaccaa242007-10-16 01:29:37 -07002167 logo.nologo [FB] Disables display of the built-in Linux logo.
2168 This may be used to provide more screen space for
2169 kernel log messages and is useful when debugging
2170 kernel boot problems.
2171
Linus Torvalds1da177e2005-04-16 15:20:36 -07002172 lp=0 [LP] Specify parallel ports to use, e.g,
2173 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2174 lp=reset first parallel port). 'lp=0' disables the
2175 lp=auto printer driver. 'lp=reset' (which can be
2176 specified in addition to the ports) causes
2177 attached printers to be reset. Using
2178 lp=port1,port2,... specifies the parallel ports
2179 to associate lp devices with, starting with
2180 lp0. A port specification may be 'none' to skip
2181 that lp device, or a parport name such as
2182 'parport0'. Specifying 'lp=auto' instead of a
2183 port specification list means that device IDs
2184 from each port should be examined, to see if
2185 an IEEE 1284-compliant printer is attached; if
2186 so, the driver will manage that printer.
2187 See also header of drivers/char/lp.c.
2188
2189 lpj=n [KNL]
2190 Sets loops_per_jiffy to given constant, thus avoiding
2191 time-consuming boot-time autodetection (up to 250 ms per
2192 CPU). 0 enables autodetection (default). To determine
2193 the correct value for your kernel, boot with normal
2194 autodetection and see what value is printed. Note that
2195 on SMP systems the preset will be applied to all CPUs,
2196 which is likely to cause problems if your CPUs need
2197 significantly divergent settings. An incorrect value
2198 will cause delays in the kernel to be wrong, leading to
2199 unpredictable I/O errors and other breakage. Although
2200 unlikely, in the extreme case this might damage your
2201 hardware.
2202
2203 ltpc= [NET]
2204 Format: <io>,<irq>,<dma>
2205
Randy Dunlap16290242011-08-13 12:34:52 -07002206 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002207 (machvec) in a generic kernel.
2208 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209
Wu Zhangjin3209e702009-07-02 23:27:12 +08002210 machtype= [Loongson] Share the same kernel image file between different
2211 yeeloong laptop.
2212 Example: machtype=lemote-yeeloong-2f-7inch
2213
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002214 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2215 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002216
2217 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002218 will bring up during bootup. maxcpus=n : n >= 0 limits
2219 the kernel to bring up 'n' processors. Surely after
2220 bootup you can bring up the other plugged cpu by executing
2221 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2222 only takes effect during system bootup.
2223 While n=0 is a special case, it is equivalent to "nosmp",
2224 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225
Kay Sieversd134b002011-07-31 22:08:04 +02002226 max_loop= [LOOP] The number of loop block devices that get
2227 (loop.max_loop) unconditionally pre-created at init time. The default
2228 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2229 of statically allocating a predefined number, loop
2230 devices can be requested on-demand with the
2231 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002232
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002233 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002234
Uwe Hermann71cced62008-10-20 09:32:21 -07002235 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002236
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 md= [HW] RAID subsystems devices and level
2238 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002239
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 mdacon= [MDA]
2241 Format: <first>,<last>
2242 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002243
Linus Torvalds1da177e2005-04-16 15:20:36 -07002244 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2245 Amount of memory to be used when the kernel is not able
2246 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002247 [X86] Work as limiting max address. Use together
2248 with memmap= to avoid physical address space collisions.
2249 Without memmap= PCI devices could be placed at addresses
2250 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002252 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253 memory.
2254
Paul Mundt6902aa82008-09-21 17:14:42 +09002255 memchunk=nn[KMG]
2256 [KNL,SH] Allow user to override the default size for
2257 per-device physically contiguous DMA buffers.
2258
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002259 memhp_default_state=online/offline
2260 [KNL] Set the initial state for the memory hotplug
2261 onlining policy. If not specified, the default value is
2262 set according to the
2263 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2264 option.
2265 See Documentation/memory-hotplug.txt.
2266
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302267 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 E820 memory map, as specified by the user.
2269 Such memmap=exactmap lines can be constructed based on
2270 BIOS output or other requirements. See the memmap=nn@ss
2271 option description.
2272
2273 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002274 [KNL] Force usage of a specific region of memory.
2275 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276
2277 memmap=nn[KMG]#ss[KMG]
2278 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002279 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002280
2281 memmap=nn[KMG]$ss[KMG]
2282 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002283 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002284 Example: Exclude memory from 0x18690000-0x1869ffff
2285 memmap=64K$0x18690000
2286 or
2287 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002288
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002289 memmap=nn[KMG]!ss[KMG]
2290 [KNL,X86] Mark specific memory as protected.
2291 Region of memory to be used, from ss to ss+nn.
2292 The memory region may be marked as e820 type 12 (0xc)
2293 and is NVDIMM or ADR memory.
2294
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002295 memory_corruption_check=0/1 [X86]
2296 Some BIOSes seem to corrupt the first 64k of
2297 memory when doing things like suspend/resume.
2298 Setting this option will scan the memory
2299 looking for corruption. Enabling this will
2300 both detect corruption and prevent the kernel
2301 from using the memory being corrupted.
2302 However, its intended as a diagnostic tool; if
2303 repeatable BIOS-originated corruption always
2304 affects the same memory, you can use memmap=
2305 to prevent the kernel from using that memory.
2306
2307 memory_corruption_check_size=size [X86]
2308 By default it checks for corruption in the low
2309 64k, making this memory unavailable for normal
2310 use. Use this parameter to scan for
2311 corruption in more or less memory.
2312
2313 memory_corruption_check_period=seconds [X86]
2314 By default it checks for corruption every 60
2315 seconds. Use this parameter to check at some
2316 other rate. 0 disables periodic checking.
2317
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002318 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002319 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002320 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002321 Specifies the number of memtest passes to be
2322 performed. Each pass selects another test
2323 pattern from a given set of patterns. Memtest
2324 fills the memory with this pattern, validates
2325 memory contents and reserves bad memory
2326 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002327
Linus Torvalds1da177e2005-04-16 15:20:36 -07002328 meye.*= [HW] Set MotionEye Camera parameters
2329 See Documentation/video4linux/meye.txt.
2330
Andres Salomon8f368812007-10-12 23:04:06 +02002331 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2332 Multi-Function General Purpose Timers on AMD Geode
2333 platforms.
2334
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002335 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2336 the BIOS has incorrectly applied a workaround. TinyBIOS
2337 version 0.98 is known to be affected, 0.99 fixes the
2338 problem by letting the user disable the workaround.
2339
Linus Torvalds1da177e2005-04-16 15:20:36 -07002340 mga= [HW,DRM]
2341
Randy Dunlap1c207f92008-11-19 15:36:16 -08002342 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2343 physical address is ignored.
2344
Michel Pollet39f45d72009-05-20 11:10:31 +01002345 mini2440= [ARM,HW,KNL]
2346 Format:[0..2][b][c][t]
2347 Default: "0tb"
2348 MINI2440 configuration specification:
2349 0 - The attached screen is the 3.5" TFT
2350 1 - The attached screen is the 7" TFT
2351 2 - The VGA Shield is attached (1024x768)
2352 Leaving out the screen size parameter will not load
2353 the TFT driver, and the framebuffer will be left
2354 unconfigured.
2355 b - Enable backlight. The TFT backlight pin will be
2356 linked to the kernel VESA blanking code and a GPIO
2357 LED. This parameter is not necessary when using the
2358 VGA shield.
2359 c - Enable the s3c camera interface.
2360 t - Reserved for enabling touchscreen support. The
2361 touchscreen support is not enabled in the mainstream
2362 kernel as of 2.6.30, a preliminary port can be found
2363 in the "bleeding edge" mini2440 support kernel at
2364 http://repo.or.cz/w/linux-2.6/mini2440.git
2365
Mel Gorman6b74ab92008-07-23 21:26:49 -07002366 mminit_loglevel=
2367 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2368 parameter allows control of the logging verbosity for
2369 the additional memory initialisation checks. A value
2370 of 0 disables mminit logging and a level of 4 will
2371 log everything. Information is printed at KERN_DEBUG
2372 so loglevel=8 may also need to be specified.
2373
Rusty Russell106a4ee2012-09-26 10:09:40 +01002374 module.sig_enforce
2375 [KNL] When CONFIG_MODULE_SIG is set, this means that
2376 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002377 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002378 is always true, so this option does nothing.
2379
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302380 module_blacklist= [KNL] Do not load a comma-separated list of
2381 modules. Useful for debugging problem modules.
2382
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383 mousedev.tap_time=
2384 [MOUSE] Maximum time between finger touching and
2385 leaving touchpad surface for touch to be considered
2386 a tap and be reported as a left button click (for
2387 touchpads working in absolute mode only).
2388 Format: <msecs>
2389 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2390 reporting absolute coordinates, such as tablets
2391 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2392 reporting absolute coordinates, such as tablets
2393
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302394 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002395 is similar to kernelcore except it specifies the
2396 amount of memory used for migratable allocations.
2397 If both kernelcore and movablecore is specified,
2398 then kernelcore will be at *least* the specified
2399 value but may be more. If movablecore on its own
2400 is specified, the administrator must be careful
2401 that the amount of memory usable for all allocations
2402 is not too small.
2403
Tang Chenc5320922013-11-12 15:08:10 -08002404 movable_node [KNL,X86] Boot-time switch to enable the effects
2405 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2406
Linus Torvalds1da177e2005-04-16 15:20:36 -07002407 MTD_Partition= [MTD]
2408 Format: <name>,<region-number>,<size>,<offset>
2409
Randy Dunlapa9913042005-10-23 12:57:11 -07002410 MTD_Region= [MTD] Format:
2411 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412
2413 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002414 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002416 multitce=off [PPC] This parameter disables the use of the pSeries
2417 firmware feature for updating multiple TCE entries
2418 at a time.
2419
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002420 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2421
2422 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2423
2424 boundary - index of last SLC block on Flex-OneNAND.
2425 The remaining blocks are configured as MLC blocks.
2426 lock - Configure if Flex-OneNAND boundary should be locked.
2427 Once locked, the boundary cannot be changed.
2428 1 indicates lock status, 0 indicates unlock status.
2429
Ben Dooks9db829f2008-07-03 11:24:29 +01002430 mtdset= [ARM]
2431 ARM/S3C2412 JIVE boot control
2432
2433 See arch/arm/mach-s3c2412/mach-jive.c
2434
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002436 [HW] Make the MicroTouch USB driver use raw coordinates
2437 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002438
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002439 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002440 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002441 that could hold holes aka. UC entries.
2442
2443 mtrr_gran_size=nn[KMG] [X86]
2444 Used for mtrr cleanup. It is granularity of mtrr block.
2445 Default is 1.
2446 Large value could prevent small alignment from
2447 using up MTRRs.
2448
2449 mtrr_spare_reg_nr=n [X86]
2450 Format: <integer>
2451 Range: 0,7 : spare reg number
2452 Default : 1
2453 Used for mtrr cleanup. It is spare mtrr entries number.
2454 Set to 2 or more if your graphical card needs more.
2455
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2457
Linus Torvalds1da177e2005-04-16 15:20:36 -07002458 netdev= [NET] Network devices parameters
2459 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2460 Note that mem_start is often overloaded to mean
2461 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002462 This usage is only documented in each driver source
2463 file if at all.
2464
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002465 nf_conntrack.acct=
2466 [NETFILTER] Enable connection tracking flow accounting
2467 0 to disable accounting
2468 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002469 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002470
Chuck Lever306a0752010-09-17 10:54:37 -04002471 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002472 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002473
2474 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002475 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002476
Chuck Lever306a0752010-09-17 10:54:37 -04002477 nfsrootdebug [NFS] enable nfsroot debugging messages.
2478 See Documentation/filesystems/nfs/nfsroot.txt.
2479
Trond Myklebust5405fc42016-08-29 20:03:52 -04002480 nfs.callback_nr_threads=
2481 [NFSv4] set the total number of threads that the
2482 NFS client will assign to service NFSv4 callback
2483 requests.
2484
Trond Myklebusta72b4422006-01-03 09:55:41 +01002485 nfs.callback_tcpport=
2486 [NFS] set the TCP port on which the NFSv4 callback
2487 channel should listen.
2488
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002489 nfs.cache_getent=
2490 [NFS] sets the pathname to the program which is used
2491 to update the NFS client cache entries.
2492
2493 nfs.cache_getent_timeout=
2494 [NFS] sets the timeout after which an attempt to
2495 update a cache entry is deemed to have failed.
2496
Trond Myklebust58df0952006-01-03 09:55:57 +01002497 nfs.idmap_cache_timeout=
2498 [NFS] set the maximum lifetime for idmapper cache
2499 entries.
2500
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002501 nfs.enable_ino64=
2502 [NFS] enable 64-bit inode numbers.
2503 If zero, the NFS client will fake up a 32-bit inode
2504 number for the readdir() and stat() syscalls instead
2505 of returning the full 64-bit number.
2506 The default is to return 64-bit inode numbers.
2507
Trond Myklebust5405fc42016-08-29 20:03:52 -04002508 nfs.max_session_cb_slots=
2509 [NFSv4.1] Sets the maximum number of session
2510 slots the client will assign to the callback
2511 channel. This determines the maximum number of
2512 callbacks the client will process in parallel for
2513 a particular server.
2514
Trond Myklebustef159e92012-02-06 19:50:40 -05002515 nfs.max_session_slots=
2516 [NFSv4.1] Sets the maximum number of session slots
2517 the client will attempt to negotiate with the server.
2518 This limits the number of simultaneous RPC requests
2519 that the client can send to the NFSv4.1 server.
2520 Note that there is little point in setting this
2521 value higher than the max_tcp_slot_table_limit.
2522
Trond Myklebustb064eca22011-02-22 15:44:32 -08002523 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002524 [NFSv4] When set to the default of '1', this option
2525 ensures that both the RPC level authentication
2526 scheme and the NFS level operations agree to use
2527 numeric uids/gids if the mount is using the
2528 'sec=sys' security flavour. In effect it is
2529 disabling idmapping, which can make migration from
2530 legacy NFSv2/v3 systems to NFSv4 easier.
2531 Servers that do not support this mode of operation
2532 will be autodetected by the client, and it will fall
2533 back to using the idmapper.
2534 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002535 nfs.nfs4_unique_id=
2536 [NFS4] Specify an additional fixed unique ident-
2537 ification string that NFSv4 clients can insert into
2538 their nfs_client_id4 string. This is typically a
2539 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002540
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002541 nfs.send_implementation_id =
2542 [NFSv4.1] Send client implementation identification
2543 information in exchange_id requests.
2544 If zero, no implementation identification information
2545 will be sent.
2546 The default is to send the implementation identification
2547 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002548
2549 nfs.recover_lost_locks =
2550 [NFSv4] Attempt to recover locks that were lost due
2551 to a lease timeout on the server. Please note that
2552 doing this risks data corruption, since there are
2553 no guarantees that the file will remain unchanged
2554 after the locks are lost.
2555 If you want to enable the kernel legacy behaviour of
2556 attempting to recover these locks, then set this
2557 parameter to '1'.
2558 The default parameter value of '0' causes the kernel
2559 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002560
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002561 nfs4.layoutstats_timer =
2562 [NFSv4.2] Change the rate at which the kernel sends
2563 layoutstats to the pNFS metadata server.
2564
2565 Setting this to value to 0 causes the kernel to use
2566 whatever value is the default set by the layout
2567 driver. A non-zero value sets the minimum interval
2568 in seconds between layoutstats transmissions.
2569
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002570 nfsd.nfs4_disable_idmapping=
2571 [NFSv4] When set to the default of '1', the NFSv4
2572 server will return only numeric uids and gids to
2573 clients using auth_sys, and will accept numeric uids
2574 and gids from such clients. This is intended to ease
2575 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002576
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002577 objlayoutdriver.osd_login_prog=
2578 [NFS] [OBJLAYOUT] sets the pathname to the program which
2579 is used to automatically discover and login into new
2580 osd-targets. Please see:
2581 Documentation/filesystems/pnfs.txt for more explanations
2582
Paul Mundt1e1030d2009-09-01 17:38:32 +09002583 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002584 when a NMI is triggered.
2585 Format: [state][,regs][,debounce][,die]
2586
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302587 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002588 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002589 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002590 0 - turn hardlockup detector in nmi_watchdog off
2591 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002592 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002593 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002594 default). To disable both hard and soft lockup detectors,
2595 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002596 This is useful when you use a panic=... timeout and
2597 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002598
Anton Vorontsovbff38772009-07-08 11:10:56 -07002599 netpoll.carrier_timeout=
2600 [NET] Specifies amount of time (in seconds) that
2601 netpoll should wait for a carrier. By default netpoll
2602 waits 4 seconds.
2603
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002604 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605 emulation library even if a 387 maths coprocessor
2606 is present.
2607
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002608 no_console_suspend
2609 [HW] Never suspend the console
2610 Disable suspending of consoles during suspend and
2611 hibernate operations. Once disabled, debugging
2612 messages can reach various consoles while the rest
2613 of the system is being put to sleep (ie, while
2614 debugging driver suspend/resume hooks). This may
2615 not work reliably with all consoles, but is known
2616 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002617 To facilitate more flexible debugging, we also add
2618 console_suspend, a printk module parameter to control
2619 it. Users could use console_suspend (usually
2620 /sys/module/printk/parameters/console_suspend) to
2621 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002622
Christoph Lameterc1aee212007-05-31 00:40:47 -07002623 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2624 caches in the slab allocator. Saves per-node memory,
2625 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002626
Randy Dunlapa9913042005-10-23 12:57:11 -07002627 noalign [KNL,ARM]
2628
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629 noapic [SMP,APIC] Tells the kernel to not make use of any
2630 IOAPICs that may be present in the system.
2631
Mike Galbraith5091faa2010-11-30 14:18:03 +01002632 noautogroup Disable scheduler automatic task group creation.
2633
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634 nobats [PPC] Do not use BATs for mapping kernel lowmem
2635 on "Classic" PPC cores.
2636
2637 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002638
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002639 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2640
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002641 nodelayacct [KNL] Disable per-task delay accounting
2642
Paul Mundt6902aa82008-09-21 17:14:42 +09002643 nodsp [SH] Disable hardware DSP at boot time.
2644
Dave Youngb2e0a542014-08-14 17:15:26 +08002645 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002646
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647 noexec [IA-64]
2648
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302649 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002650 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002651 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002652 noexec=off: disable non-executable mappings
2653
H. Peter Anvin52b61792012-09-21 12:43:13 -07002654 nosmap [X86]
2655 Disable SMAP (Supervisor Mode Access Prevention)
2656 even if it is supported by processor.
2657
Fenghua Yude5397a2011-05-11 16:51:05 -07002658 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002659 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002660 even if it is supported by processor.
2661
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002662 noexec32 [X86-64]
2663 This affects only 32-bit executables.
2664 noexec32=on: enable non-executable mappings (default)
2665 read doesn't imply executable mappings
2666 noexec32=off: disable non-executable mappings
2667 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002668
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002669 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002670
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002671 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002672 register save and restore. The kernel will only save
2673 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002674
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002675 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2676
Sascha Silbe52c48c52016-04-05 12:53:38 +02002677 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2678 Equivalent to smt=1.
2679
Suresh Siddha0c752a92009-05-22 12:17:45 -07002680 noxsave [BUGS=X86] Disables x86 extended register state save
2681 and restore using xsave. The kernel will fallback to
2682 enabling legacy floating-point and sse state.
2683
Fenghua Yub6f42a42014-05-29 11:12:31 -07002684 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2685 register states. The kernel will fall back to use
2686 xsave to save the states. By using this parameter,
2687 performance of saving the states is degraded because
2688 xsave doesn't support modified optimization while
2689 xsaveopt supports it on xsaveopt enabled systems.
2690
2691 noxsaves [X86] Disables xsaves and xrstors used in saving and
2692 restoring x86 extended register state in compacted
2693 form of xsave area. The kernel will fall back to use
2694 xsaveopt and xrstor to save and restore the states
2695 in standard form of xsave area. By using this
2696 parameter, xsave area per process might occupy more
2697 memory on xsaves enabled systems.
2698
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002699 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2700 wfi(ARM) instruction doesn't work correctly and not to
2701 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002702
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002703 no_file_caps Tells the kernel not to honor file capabilities. The
2704 only way then for a file to be executed with privilege
2705 is to be setuid root or executed by root.
2706
Linus Torvalds1da177e2005-04-16 15:20:36 -07002707 nohalt [IA-64] Tells the kernel not to use the power saving
2708 function PAL_HALT_LIGHT when idle. This increases
2709 power-consumption. On the positive side, it reduces
2710 interrupt wake-up latency, which may improve performance
2711 in certain environments such as networked servers or
2712 real-time systems.
2713
Kees Cooka6e15a32014-06-13 13:30:35 -07002714 nohibernate [HIBERNATION] Disable hibernation and resume.
2715
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002716 nohz= [KNL] Boottime enable/disable dynamic ticks
2717 Valid arguments: on, off
2718 Default: on
2719
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002720 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002721 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002722 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002723 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002724 whenever possible. The boot CPU will be forced outside
2725 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002726 The CPUs in this range must also be included in the
2727 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002728
Paul Mundteeee7852009-04-02 12:31:16 +09002729 noiotrap [SH] Disables trapped I/O port accesses.
2730
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002731 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732 disable unhandled interrupt sources.
2733
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302734 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002735 broken timer IRQ sources.
2736
Linus Torvalds1da177e2005-04-16 15:20:36 -07002737 noisapnp [ISAPNP] Disables ISA PnP code.
2738
2739 noinitrd [RAM] Tells the kernel not to load any configured
2740 initial RAM disk.
2741
Weidong Han03ea8152009-04-17 16:42:15 +08002742 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2743 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002744 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002745
Linus Torvalds1da177e2005-04-16 15:20:36 -07002746 nointroute [IA-64]
2747
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002748 noinvpcid [X86] Disable the INVPCID cpu feature.
2749
Randy Dunlap16290242011-08-13 12:34:52 -07002750 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002751
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002752 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2753
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002754 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2755 fault handling.
2756
Glauber Costad910f5c2011-07-11 15:28:19 -04002757 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2758 steal time is computed, but won't influence scheduler
2759 behaviour
2760
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002761 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002762
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002763 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002764
Linus Torvalds1da177e2005-04-16 15:20:36 -07002765 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002766 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767
Horms312f1f02006-02-22 09:57:55 +09002768 nomca [IA-64] Disable machine check abort handling
2769
Masanari Iida13696e02015-05-16 02:16:43 +09002770 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002771
Andres Salomon83d73842007-10-12 23:04:06 +02002772 nomfgpt [X86-32] Disable Multi-Function General Purpose
2773 Timer usage (for AMD Geode machines).
2774
Don Zickusbda62632011-10-13 15:14:27 -04002775 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2776 shutdown the other cpus. Instead use the REBOOT_VECTOR
2777 irq.
2778
Dave Young02608be2012-02-01 10:33:14 +08002779 nomodule Disable module load
2780
Jiri Kosina016ddd92010-01-18 17:05:40 +01002781 nopat [X86] Disable PAT (page attribute table extension of
2782 pagetables) support.
2783
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002784 norandmaps Don't use address space randomization. Equivalent to
2785 echo 0 > /proc/sys/kernel/randomize_va_space
2786
Jiri Kosinabbff2162010-08-11 18:34:09 +02002787 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002788
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002789 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002790 with UP alternatives
2791
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002792 nordrand [X86] Disable kernel use of the RDRAND and
2793 RDSEED instructions even if they are supported
2794 by the processor. RDRAND and RDSEED are still
2795 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002796
Randy Dunlapa9913042005-10-23 12:57:11 -07002797 noresume [SWSUSP] Disables resume and restores original swap
2798 space.
2799
Linus Torvalds1da177e2005-04-16 15:20:36 -07002800 no-scroll [VGA] Disables scrollback.
2801 This is required for the Braillex ib80-piezo Braille
2802 reader made by F.H. Papenmeier (Germany).
2803
2804 nosbagart [IA-64]
2805
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002806 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002807
Len Brown61ec7562007-08-16 03:34:22 -04002808 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2809 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002810
Dave Jones97842212007-07-15 23:41:05 -07002811 nosoftlockup [KNL] Disable the soft-lockup detector.
2812
Linus Torvalds1da177e2005-04-16 15:20:36 -07002813 nosync [HW,M68K] Disables sync negotiation for all devices.
2814
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002815 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002816
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002817 nowatchdog [KNL] Disable both lockup detectors, i.e.
2818 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002819
Linus Torvalds1da177e2005-04-16 15:20:36 -07002820 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002821
Weidong Han2b2fd872009-04-17 16:42:12 +08002822 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2823
Fenghua Yuf78cff42012-11-13 11:32:38 -08002824 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2825 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2826 Some features depend on CPU0. Known dependencies are:
2827 1. Resume from suspend/hibernate depends on CPU0.
2828 Suspend/hibernate will fail if CPU0 is offline and you
2829 need to online CPU0 before suspend/hibernate.
2830 2. PIC interrupts also depend on CPU0. CPU0 can't be
2831 removed if a PIC interrupt is detected.
2832 It's said poweroff/reboot may depend on CPU0 on some
2833 machines although I haven't seen such issues so far
2834 after CPU0 is offline on a few tested machines.
2835 If the dependencies are under your control, you can
2836 turn on cpu0_hotplug.
2837
Randy Dunlap16290242011-08-13 12:34:52 -07002838 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002839 purges which is reported from either PAL_VM_SUMMARY or
2840 SAL PALO.
2841
Yinghai Lu2b633e32010-02-10 01:20:37 -08002842 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2843 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002844 support 'n' processors. It could be larger than the
2845 number of already plugged CPU during bootup, later in
2846 runtime you can physically add extra cpu until it reaches
2847 n. So during boot up some boot time memory for per-cpu
2848 variables need be pre-allocated for later physical cpu
2849 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002850
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002851 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2852
Mel Gorman1a687c22012-11-22 11:16:36 +00002853 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2854 Allowed values are enable and disable
2855
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002856 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2857 one of ['zone', 'node', 'default'] can be specified
2858 This can be set from sysctl after boot.
2859 See Documentation/sysctl/vm.txt for details.
2860
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002861 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2862 See Documentation/debugging-via-ohci1394.txt for more
2863 info.
2864
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002865 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2866 Rather than timing out after 20 ms if an EC
2867 command is not properly ACKed, override the length
2868 of the timeout. We have interrupts disabled while
2869 waiting for the ACK, so if this is set too high
2870 interrupts *may* be lost!
2871
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002872 omap_mux= [OMAP] Override bootloader pin multiplexing.
2873 Format: <mux_mode0.mode_name=value>...
2874 For example, to override I2C bus2:
2875 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2876
Linus Torvalds1da177e2005-04-16 15:20:36 -07002877 oprofile.timer= [HW]
2878 Use timer interrupt instead of performance counters
2879
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002880 oprofile.cpu_type= Force an oprofile cpu type
2881 This might be useful if you have an older oprofile
2882 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002883 Format: { arch_perfmon }
2884 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002885 perfmon on Intel CPUs instead of the
2886 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002887 timer: [X86] Force use of architectural NMI
2888 timer mode (see also oprofile.timer
2889 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002890
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002891 oops=panic Always panic on oopses. Default is to just kill the
2892 process, but there is a small probability of
2893 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002894 This will also cause panics on machine check exceptions.
2895 Useful together with panic=30 to trigger a reboot.
2896
Randy Dunlapbcfde332010-06-07 17:10:38 -07002897 OSS [HW,OSS]
2898 See Documentation/sound/oss/oss-parameters.txt
2899
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002900 page_owner= [KNL] Boot-time page_owner enabling option.
2901 Storage of the information about who allocated
2902 each page is disabled in default. With this switch,
2903 we can turn it on.
2904 on: enable the feature
2905
Laura Abbott8823b1d2016-03-15 14:56:27 -07002906 page_poison= [KNL] Boot-time parameter changing the state of
2907 poisoning on the buddy allocator.
2908 off: turn off poisoning
2909 on: turn on poisoning
2910
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002911 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002912 timeout > 0: seconds before rebooting
2913 timeout = 0: wait forever
2914 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002915 Format: <timeout>
2916
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002917 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2918 on a WARN().
2919
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002920 crash_kexec_post_notifiers
2921 Run kdump after running panic-notifiers and dumping
2922 kmsg. This only for the users who doubt kdump always
2923 succeeds in any situation.
2924 Note that this also increases risks of kdump failure,
2925 because some panic notifiers can make the crashed
2926 kernel more unstable.
2927
Linus Torvalds1da177e2005-04-16 15:20:36 -07002928 parkbd.port= [HW] Parallel port number the keyboard adapter is
2929 connected to, default is 0.
2930 Format: <parport#>
2931 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2932 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002933 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934
Randy Dunlapa9913042005-10-23 12:57:11 -07002935 parport= [HW,PPT] Specify parallel ports. 0 disables.
2936 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2937 Use 'auto' to force the driver to use any
2938 IRQ/DMA settings detected (the default is to
2939 ignore detected IRQ/DMA settings because of
2940 possible conflicts). You can specify the base
2941 address, IRQ, and DMA settings; IRQ and DMA
2942 should be numbers, or 'auto' (for using detected
2943 settings on that particular port), or 'nofifo'
2944 (to avoid using a FIFO even if it is detected).
2945 Parallel ports are assigned in the order they
2946 are specified on the command line, starting
2947 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948
Randy Dunlapa9913042005-10-23 12:57:11 -07002949 parport_init_mode= [HW,PPT]
2950 Configure VIA parallel port to operate in
2951 a specific mode. This is necessary on Pegasos
2952 computer where firmware has no options for setting
2953 up parallel port mode and sets it to spp.
2954 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955 Format: [spp|ps2|epp|ecp|ecpepp]
2956
Andrew Mortondd287792006-03-23 03:00:57 -08002957 pause_on_oops=
2958 Halt all CPUs after the first oops has been printed for
2959 the specified number of seconds. This is to be used if
2960 your oopses keep scrolling off the screen.
2961
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962 pcbit= [HW,ISDN]
2963
2964 pcd. [PARIDE]
2965 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002966 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002967
Randy Dunlapa9913042005-10-23 12:57:11 -07002968 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002969 earlydump [X86] dump PCI config space before the kernel
2970 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002971 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002972 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002973 the hardware directly. Use this if your machine
2974 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002975 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002976 hardware access methods are allowed. Use this
2977 if you experience crashes upon bootup and you
2978 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002979 conf1 [X86] Force use of PCI Configuration Access
2980 Mechanism 1 (config address in IO port 0xCF8,
2981 data in IO port 0xCFC, both 32-bit).
2982 conf2 [X86] Force use of PCI Configuration Access
2983 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2984 the function, IO port 0xCFA, also 8-bit, sets
2985 bus number. The config space is then accessed
2986 through ports 0xC000-0xCFFF).
2987 See http://wiki.osdev.org/PCI for more info
2988 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002989 noaer [PCIE] If the PCIEAER kernel config parameter is
2990 enabled, this kernel boot option can be used to
2991 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002992 nodomains [PCI] Disable support for multiple PCI
2993 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302994 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002995 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002996 check_enable_amd_mmconf [X86] check for and enable
2997 properly configured MMIO access to PCI
2998 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002999 nomsi [MSI] If the PCI_MSI kernel config parameter is
3000 enabled, this kernel boot option can be used to
3001 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02003002 noioapicquirk [APIC] Disable all boot interrupt quirks.
3003 Safety option to keep boot IRQs enabled. This
3004 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02003005 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3006 primary IO-APIC for bridges that cannot disable
3007 boot IRQs. This fixes a source of spurious IRQs
3008 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02003009 noioapicreroute [APIC] Disable workaround that uses the
3010 boot IRQ equivalent of an IRQ that connects to
3011 a chipset where boot IRQs cannot be disabled.
3012 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003013 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07003014 routing table. These calls are known to be buggy
3015 on several machines and they hang the machine
3016 when used, but on other computers it's the only
3017 way to get the interrupt routing table. Try
3018 this option if the kernel is unable to allocate
3019 IRQs or discover secondary PCI buses on your
3020 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02003021 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07003022 Use with caution as certain devices share
3023 address decoders between ROMs and other
3024 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02003025 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07003026 expansion ROMs that do not already have
3027 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07003028 nobar [X86] Do not assign address space to the
3029 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02003030 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07003031 assigned automatically to PCI devices. You can
3032 make the kernel exclude IRQs of your ISA cards
3033 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02003034 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07003035 of the PIRQ table (normally generated
3036 by the BIOS) if it is outside the
3037 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02003038 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07003039 useful if the kernel is unable to find your
3040 secondary buses and you want to tell it
3041 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02003042 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07003043 numbers ourselves, overriding
3044 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02003045 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07003046 in the BIOS $PIR table. This is needed on
3047 some systems with broken BIOSes, notably
3048 some HP Pavilion N5400 and Omnibook XE3
3049 notebooks. This will have no effect if ACPI
3050 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02003051 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07003052 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07003053 use_crs [X86] Use PCI host bridge window information
3054 from ACPI. On BIOSes from 2008 or later, this
3055 is enabled by default. If you need to use this,
3056 please report a bug.
3057 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3058 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07003059 routeirq Do IRQ routing for all PCI devices.
3060 This is normally done in pci_enable_device(),
3061 so this option is a temporary workaround
3062 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07003063 skip_isa_align [X86] do not align io start addr, so can
3064 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02003065 noearly [X86] Don't do any early type 1 scanning.
3066 This might help on some broken boards which
3067 machine check when some devices' config space
3068 is read. But various workarounds are disabled
3069 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003070 bfsort Sort PCI devices into breadth-first order.
3071 This sorting is done to get a device
3072 order compatible with older (<= 2.4) kernels.
3073 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08003074 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3075 tuning and use the BIOS-configured MPS defaults.
3076 pcie_bus_safe Set every device's MPS to the largest value
3077 supported by all devices below the root complex.
3078 pcie_bus_perf Set device MPS to the largest allowable MPS
3079 based on its parent bus. Also set MRRS (Max
3080 Read Request Size) to the largest supported
3081 value (no larger than the MPS that the device
3082 or bus can support) for best performance.
3083 pcie_bus_peer2peer Set every device's MPS to 128B, which
3084 every device is guaranteed to support. This
3085 configuration allows peer-to-peer DMA between
3086 any pair of devices, possibly at the cost of
3087 reduced performance. This also guarantees
3088 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08003089 cbiosize=nn[KMG] The fixed amount of bus space which is
3090 reserved for the CardBus bridge's IO window.
3091 The default value is 256 bytes.
3092 cbmemsize=nn[KMG] The fixed amount of bus space which is
3093 reserved for the CardBus bridge's memory
3094 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003095 resource_alignment=
3096 Format:
3097 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00003098 [<order of align>@]pci:<vendor>:<device>\
3099 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003100 Specifies alignment and device to reassign
3101 aligned memory resources.
3102 If <order of align> is not specified,
3103 PAGE_SIZE is used as alignment.
3104 PCI-PCI bridge can be specified, if resource
3105 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02003106 To specify the alignment for several
3107 instances of a device, the PCI vendor,
3108 device, subvendor, and subdevice may be
3109 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06003110 ecrc= Enable/disable PCIe ECRC (transaction layer
3111 end-to-end CRC checking).
3112 bios: Use BIOS/firmware settings. This is the
3113 the default.
3114 off: Turn ECRC off
3115 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08003116 hpiosize=nn[KMG] The fixed amount of bus space which is
3117 reserved for hotplug bridge's IO window.
3118 Default size is 256 bytes.
3119 hpmemsize=nn[KMG] The fixed amount of bus space which is
3120 reserved for hotplug bridge's memory window.
3121 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06003122 hpbussize=nn The minimum amount of additional bus numbers
3123 reserved for buses below a hotplug bridge.
3124 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08003125 realloc= Enable/disable reallocating PCI bridge resources
3126 if allocations done by BIOS are too small to
3127 accommodate resources required by all child
3128 devices.
3129 off: Turn realloc off
3130 on: Turn realloc on
3131 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01003132 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003133 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3134 only look for one device below a PCIe downstream
3135 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003136
Chuck Ebberte5665a42008-09-24 20:40:34 -04003137 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3138 Management.
3139 off Disable ASPM.
3140 force Enable ASPM even on devices that claim not to support it.
3141 WARNING: Forcing ASPM on may cause system lockups.
3142
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003143 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3144 nomsi Do not use MSI for PCI Express Native Hotplug (this
3145 makes all PCIe ports use INTx for hotplug services).
3146
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003147 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003148 auto Ask the BIOS whether or not to use native PCIe services
3149 associated with PCIe ports (PME, hot-plug, AER). Use
3150 them only if that is allowed by the BIOS.
3151 native Use native PCIe services associated with PCIe ports
3152 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003153 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3154 ports driver.
3155
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03003156 pcie_port_pm= [PCIE] PCIe port power management handling:
3157 off Disable power management of all PCIe ports
3158 force Forcibly enable power management of all PCIe ports
3159
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003160 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003161 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003162 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003163
Linus Torvalds1da177e2005-04-16 15:20:36 -07003164 pcmv= [HW,PCMCIA] BadgePAD 4
3165
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303166 pd_ignore_unused
3167 [PM]
3168 Keep all power-domains already enabled by bootloader on,
3169 even if no driver has claimed them. This is useful
3170 for debug and development, but should not be
3171 needed on a platform with proper driver support.
3172
Linus Torvalds1da177e2005-04-16 15:20:36 -07003173 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003174 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003175
3176 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3177 boot time.
3178 Format: { 0 | 1 }
3179 See arch/parisc/kernel/pdc_chassis.c
3180
Tejun Heof58dc012009-08-14 15:00:50 +09003181 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003182 Currently supported values are "embed" and "page".
3183 Archs may support subset or none of the selections.
3184 See comments in mm/percpu.c for details on each
3185 allocator. This parameter is primarily for debugging
3186 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003187
Linus Torvalds1da177e2005-04-16 15:20:36 -07003188 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003189 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190
3191 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003192 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003193
3194 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003195 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196
3197 plip= [PPT,NET] Parallel port network link
3198 Format: { parport<nr> | timid | 0 }
3199 See also Documentation/parport.txt.
3200
Randy Dunlap16290242011-08-13 12:34:52 -07003201 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003202 Override pmtimer IOPort with a hex value.
3203 e.g. pmtmr=0x508
3204
Bjorn Helgaas96242112011-08-11 12:14:05 -06003205 pnp.debug=1 [PNP]
3206 Enable PNP debug messages (depends on the
3207 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3208 via /sys/module/pnp/parameters/debug. We always show
3209 current resource usage; turning this on also shows
3210 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003211
Linus Torvalds1da177e2005-04-16 15:20:36 -07003212 pnpacpi= [ACPI]
3213 { off }
3214
3215 pnpbios= [ISAPNP]
3216 { on | off | curr | res | no-curr | no-res }
3217
3218 pnp_reserve_irq=
3219 [ISAPNP] Exclude IRQs for the autoconfiguration
3220
3221 pnp_reserve_dma=
3222 [ISAPNP] Exclude DMAs for the autoconfiguration
3223
3224 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003225 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003226
3227 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003228 [ISAPNP] Exclude memory regions for the
3229 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003230 Ranges are in pairs (memory base and size).
3231
Randy Dunlap4af94f32009-04-17 18:30:28 -07003232 ports= [IP_VS_FTP] IPVS ftp helper module
3233 Default is 21.
3234 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3235 may be specified.
3236 Format: <port>,<port>....
3237
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003238 ppc_strict_facility_enable
3239 [PPC] This option catches any kernel floating point,
3240 Altivec, VSX and SPE outside of regions specifically
3241 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3242 There is some performance impact when enabling this.
3243
Ingo Molnar45807a12007-07-15 23:40:10 -07003244 print-fatal-signals=
3245 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003246
3247 If enabled, warn about various signal handling
3248 related application anomalies: too many signals,
3249 too many POSIX.1 timers, fatal signals causing a
3250 coredump - etc.
3251
3252 If you hit the warning due to signal overflow,
3253 you might want to try "ulimit -i unlimited".
3254
Ingo Molnar45807a12007-07-15 23:40:10 -07003255 default: off.
3256
Matthew Garrettc22ab332012-03-05 14:59:10 -08003257 printk.always_kmsg_dump=
3258 Trigger kmsg_dump for cases other than kernel oops or
3259 panics
3260 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3261 default: disabled
3262
Borislav Petkov750afe72016-08-02 14:04:07 -07003263 printk.devkmsg={on,off,ratelimit}
3264 Control writing to /dev/kmsg.
3265 on - unlimited logging to /dev/kmsg from userspace
3266 off - logging to /dev/kmsg disabled
3267 ratelimit - ratelimit the logging
3268 Default: ratelimit
3269
Randy Dunlape84845c2007-07-15 23:40:25 -07003270 printk.time= Show timing data prefixed to each printk message line
3271 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3272
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003273 processor.max_cstate= [HW,ACPI]
3274 Limit processor to maximum C-state
3275 max_cstate=9 overrides any DMI blacklist limit.
3276
3277 processor.nocst [HW,ACPI]
3278 Ignore the _CST method to determine C-states,
3279 instead using the legacy FADT method
3280
Linus Torvalds1da177e2005-04-16 15:20:36 -07003281 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003282 Format: [schedule,]<number>
3283 Param: "schedule" - profile schedule points.
3284 Param: <number> - step/bucket size as a power of 2 for
3285 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003286 Param: "sleep" - profile D-state sleeping (millisecs).
3287 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003288 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003289
Linus Torvalds1da177e2005-04-16 15:20:36 -07003290 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3291 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003292 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003293
Randy Dunlapa9913042005-10-23 12:57:11 -07003294 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3295 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003296 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3297 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003298 psmouse.resetafter= [HW,MOUSE]
3299 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003300 (0 = never).
3301 psmouse.resolution=
3302 [HW,MOUSE] Set desired mouse resolution, in dpi.
3303 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003304 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003305 0 = disabled, 1 = enabled (default).
3306
Matthew Garrettdee28e72011-07-21 16:57:55 -04003307 pstore.backend= Specify the name of the pstore backend to use
3308
Linus Torvalds1da177e2005-04-16 15:20:36 -07003309 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003310 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003311
Kay Sieversdc8c8582007-08-15 12:25:38 +02003312 pty.legacy_count=
3313 [KNL] Number of legacy pty's. Overwrites compiled-in
3314 default number.
3315
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003316 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003317
Linus Torvalds1da177e2005-04-16 15:20:36 -07003318 r128= [HW,DRM]
3319
3320 raid= [HW,RAID]
3321 See Documentation/md.txt.
3322
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003324 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003325
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003326 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003327 The argument is a cpu list, as described above.
3328
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003329 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3330 the specified list of CPUs to be no-callback CPUs.
3331 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003332 be offloaded to "rcuox/N" kthreads created for
3333 that purpose, where "x" is "b" for RCU-bh, "p"
3334 for RCU-preempt, and "s" for RCU-sched, and "N"
3335 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003336 offloaded CPUs, which can be useful for HPC and
3337 real-time workloads. It can also improve energy
3338 efficiency for asymmetric multiprocessors.
3339
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003340 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003341 Rather than requiring that offloaded CPUs
3342 (specified by rcu_nocbs= above) explicitly
3343 awaken the corresponding "rcuoN" kthreads,
3344 make these kthreads poll for callbacks.
3345 This improves the real-time response for the
3346 offloaded CPUs by relieving them of the need to
3347 wake up the corresponding kthread, but degrades
3348 energy efficiency by requiring that the kthreads
3349 periodically wake up to do the polling.
3350
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003351 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003352 Set maximum number of finished RCU callbacks to
3353 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003354
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003355 rcutree.dump_tree= [KNL]
3356 Dump the structure of the rcu_node combining tree
3357 out at early boot. This is used for diagnostic
3358 purposes, to verify correct tree setup.
3359
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003360 rcutree.gp_cleanup_delay= [KNL]
3361 Set the number of jiffies to delay each step of
3362 RCU grace-period cleanup. This only has effect
3363 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3364
Paul E. McKenney37745d22015-01-22 18:24:08 -08003365 rcutree.gp_init_delay= [KNL]
3366 Set the number of jiffies to delay each step of
3367 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003368 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3369 is set.
3370
3371 rcutree.gp_preinit_delay= [KNL]
3372 Set the number of jiffies to delay each step of
3373 RCU grace-period pre-initialization, that is,
3374 the propagation of recent CPU-hotplug changes up
3375 the rcu_node combining tree. This only has effect
3376 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003377
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003378 rcutree.rcu_fanout_exact= [KNL]
3379 Disable autobalancing of the rcu_node combining
3380 tree. This is used by rcutorture, and might
3381 possibly be useful for architectures having high
3382 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003383
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003384 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003385 Change the number of CPUs assigned to each
3386 leaf rcu_node structure. Useful for very
3387 large systems, which will choose the value 64,
3388 and for NUMA systems with large remote-access
3389 latencies, which will choose a value aligned
3390 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003391
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003392 rcutree.jiffies_till_sched_qs= [KNL]
3393 Set required age in jiffies for a
3394 given grace period before RCU starts
3395 soliciting quiescent-state help from
3396 rcu_note_context_switch().
3397
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003398 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003399 Set delay from grace-period initialization to
3400 first attempt to force quiescent states.
3401 Units are jiffies, minimum value is zero,
3402 and maximum value is HZ.
3403
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003404 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003405 Set delay between subsequent attempts to force
3406 quiescent states. Units are jiffies, minimum
3407 value is one, and maximum value is HZ.
3408
Clark Williams21871d72014-09-12 21:21:09 -05003409 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003410 Set the SCHED_FIFO priority of the RCU per-CPU
3411 kthreads (rcuc/N). This value is also used for
3412 the priority of the RCU boost threads (rcub/N)
3413 and for the RCU grace-period kthreads (rcu_bh,
3414 rcu_preempt, and rcu_sched). If RCU_BOOST is
3415 set, valid values are 1-99 and the default is 1
3416 (the least-favored priority). Otherwise, when
3417 RCU_BOOST is not set, valid values are 0-99 and
3418 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003419
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003420 rcutree.rcu_nocb_leader_stride= [KNL]
3421 Set the number of NOCB kthread groups, which
3422 defaults to the square root of the number of
3423 CPUs. Larger numbers reduces the wakeup overhead
3424 on the per-CPU grace-period kthreads, but increases
3425 that same overhead on each group's leader.
3426
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003427 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003428 Set threshold of queued RCU callbacks beyond which
3429 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003430
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003431 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003432 Set threshold of queued RCU callbacks below which
3433 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003434
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003435 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003436 Set wakeup interval for idle CPUs that have
3437 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003438
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003439 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003440 Set wakeup interval for idle CPUs that have
3441 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3442 Lazy RCU callbacks are those which RCU can
3443 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003444
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003445 rcuperf.gp_exp= [KNL]
3446 Measure performance of expedited synchronous
3447 grace-period primitives.
3448
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003449 rcuperf.holdoff= [KNL]
3450 Set test-start holdoff period. The purpose of
3451 this parameter is to delay the start of the
3452 test until boot completes in order to avoid
3453 interference.
3454
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003455 rcuperf.nreaders= [KNL]
3456 Set number of RCU readers. The value -1 selects
3457 N, where N is the number of CPUs. A value
3458 "n" less than -1 selects N-n+1, where N is again
3459 the number of CPUs. For example, -2 selects N
3460 (the number of CPUs), -3 selects N+1, and so on.
3461 A value of "n" less than or equal to -N selects
3462 a single reader.
3463
3464 rcuperf.nwriters= [KNL]
3465 Set number of RCU writers. The values operate
3466 the same as for rcuperf.nreaders.
3467 N, where N is the number of CPUs
3468
3469 rcuperf.perf_runnable= [BOOT]
3470 Start rcuperf running at boot time.
3471
3472 rcuperf.shutdown= [KNL]
3473 Shut the system down after performance tests
3474 complete. This is useful for hands-off automated
3475 testing.
3476
3477 rcuperf.perf_type= [KNL]
3478 Specify the RCU implementation to test.
3479
3480 rcuperf.verbose= [KNL]
3481 Enable additional printk() statements.
3482
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003483 rcutorture.cbflood_inter_holdoff= [KNL]
3484 Set holdoff time (jiffies) between successive
3485 callback-flood tests.
3486
3487 rcutorture.cbflood_intra_holdoff= [KNL]
3488 Set holdoff time (jiffies) between successive
3489 bursts of callbacks within a given callback-flood
3490 test.
3491
3492 rcutorture.cbflood_n_burst= [KNL]
3493 Set the number of bursts making up a given
3494 callback-flood test. Set this to zero to
3495 disable callback-flood testing.
3496
3497 rcutorture.cbflood_n_per_burst= [KNL]
3498 Set the number of callbacks to be registered
3499 in a given burst of a callback-flood test.
3500
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003501 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003502 Set duration of force_quiescent_state bursts
3503 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003504
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003505 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003506 Set holdoff time within force_quiescent_state bursts
3507 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003508
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003509 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003510 Set wait time between force_quiescent_state bursts
3511 in seconds.
3512
3513 rcutorture.gp_cond= [KNL]
3514 Use conditional/asynchronous update-side
3515 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003516
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003517 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003518 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003519
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003520 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003521 Use normal (non-expedited) asynchronous
3522 update-side primitives, if available.
3523
3524 rcutorture.gp_sync= [KNL]
3525 Use normal (non-expedited) synchronous
3526 update-side primitives, if available. If all
3527 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3528 rcutorture.gp_normal=, and rcutorture.gp_sync=
3529 are zero, rcutorture acts as if is interpreted
3530 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003531
3532 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003533 Set callbacks/threads for rcu_barrier() testing.
3534
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003535 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003536 Set number of concurrent RCU writers. These just
3537 stress RCU, they don't participate in the actual
3538 test, hence the "fake".
3539
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003540 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003541 Set number of RCU readers. The value -1 selects
3542 N-1, where N is the number of CPUs. A value
3543 "n" less than -1 selects N-n-2, where N is again
3544 the number of CPUs. For example, -2 selects N
3545 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003546
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003547 rcutorture.object_debug= [KNL]
3548 Enable debug-object double-call_rcu() testing.
3549
3550 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003551 Set time (s) after boot for CPU-hotplug testing.
3552
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003553 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003554 Set time (s) between CPU-hotplug operations, or
3555 zero to disable CPU-hotplug testing.
3556
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003557 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003558 Set task-shuffle interval (s). Shuffling tasks
3559 allows some CPUs to go into dyntick-idle mode
3560 during the rcutorture test.
3561
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003562 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003563 Set time (s) after boot system shutdown. This
3564 is useful for hands-off automated testing.
3565
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003566 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003567 Duration of CPU stall (s) to test RCU CPU stall
3568 warnings, zero to disable.
3569
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003570 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003571 Time to wait (s) after boot before inducing stall.
3572
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003573 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003574 Time (s) between statistics printk()s.
3575
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003576 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003577 Time (s) to stutter testing, for example, specifying
3578 five seconds causes the test to run for five seconds,
3579 wait for five seconds, and so on. This tests RCU's
3580 ability to transition abruptly to and from idle.
3581
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003582 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003583 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3584 "Maybe" means test if the RCU implementation
3585 under test support RCU priority boosting.
3586
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003587 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003588 Duration (s) of each individual boost test.
3589
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003590 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003591 Interval (s) between each boost test.
3592
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003593 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003594 Test RCU's dyntick-idle handling. See also the
3595 rcutorture.shuffle_interval parameter.
3596
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003597 rcutorture.torture_runnable= [BOOT]
3598 Start rcutorture running at boot time.
3599
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003600 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003601 Specify the RCU implementation to test.
3602
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003603 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003604 Enable additional printk() statements.
3605
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003606 rcupdate.rcu_cpu_stall_suppress= [KNL]
3607 Suppress RCU CPU stall warning messages.
3608
3609 rcupdate.rcu_cpu_stall_timeout= [KNL]
3610 Set timeout for RCU CPU stall warning messages.
3611
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003612 rcupdate.rcu_expedited= [KNL]
3613 Use expedited grace-period primitives, for
3614 example, synchronize_rcu_expedited() instead
3615 of synchronize_rcu(). This reduces latency,
3616 but can increase CPU utilization, degrade
3617 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003618 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003619
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003620 rcupdate.rcu_normal= [KNL]
3621 Use only normal grace-period primitives,
3622 for example, synchronize_rcu() instead of
3623 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003624 real-time latency, CPU utilization, and
3625 energy efficiency, but can expose users to
3626 increased grace-period latency. This parameter
3627 overrides rcupdate.rcu_expedited. No effect on
3628 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003629
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003630 rcupdate.rcu_normal_after_boot= [KNL]
3631 Once boot has completed (that is, after
3632 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003633 only normal grace-period primitives. No effect
3634 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003635
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003636 rcupdate.rcu_task_stall_timeout= [KNL]
3637 Set timeout in jiffies for RCU task stall warning
3638 messages. Disable with a value less than or equal
3639 to zero.
3640
Pranith Kumar74860fe2014-09-19 11:34:09 -04003641 rcupdate.rcu_self_test= [KNL]
3642 Run the RCU early boot self tests
3643
3644 rcupdate.rcu_self_test_bh= [KNL]
3645 Run the RCU bh early boot self tests
3646
3647 rcupdate.rcu_self_test_sched= [KNL]
3648 Run the RCU sched early boot self tests
3649
Olof Johanssonffdfc402005-09-06 15:17:19 -07003650 rdinit= [KNL]
3651 Format: <full_path>
3652 Run specified binary instead of /init from the ramdisk,
3653 used for early userspace startup. See initrd.
3654
Robin Holt1b3a5d02013-07-08 16:01:42 -07003655 reboot= [KNL]
3656 Format (x86 or x86_64):
3657 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3658 [[,]s[mp]#### \
3659 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3660 [[,]f[orce]
3661 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3662 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3663 reboot_force is either force or not specified,
3664 reboot_cpu is s[mp]#### with #### being the processor
3665 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003666
Paul Jackson46b6d942008-07-04 10:00:09 -07003667 relax_domain_level=
3668 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003669 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003670
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003671 relative_sleep_states=
3672 [SUSPEND] Use sleep state labeling where the deepest
3673 state available other than hibernation is always "mem".
3674 Format: { "0" | "1" }
3675 0 -- Traditional sleep state labels.
3676 1 -- Relative sleep state labels.
3677
Linus Torvalds1da177e2005-04-16 15:20:36 -07003678 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3679
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003680 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003681 Format: nn[KMG]
3682 Reserves a hole at the top of the kernel virtual
3683 address space.
3684
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003685 reservelow= [X86]
3686 Format: nn[K]
3687 Set the amount of memory to reserve for BIOS at
3688 the bottom of the address space.
3689
Vivek Goyal7e962872006-09-27 01:50:44 -07003690 reset_devices [KNL] Force drivers to reset the underlying device
3691 during initialization.
3692
Randy Dunlapa9913042005-10-23 12:57:11 -07003693 resume= [SWSUSP]
3694 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003695 Format:
3696 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003697
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003698 resume_offset= [SWSUSP]
3699 Specify the offset from the beginning of the partition
3700 given by "resume=" at which the swap header is located,
3701 in <PAGE_SIZE> units (needed only for swap files).
3702 See Documentation/power/swsusp-and-swap-files.txt
3703
Barry Songf126f732011-10-10 23:38:41 +02003704 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3705 read the resume files
3706
Barry Song6f8d7022011-10-06 20:34:46 +02003707 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3708 Useful for devices that are detected asynchronously
3709 (e.g. USB and MMC devices).
3710
Bojan Smojverf996fc92010-09-09 23:06:23 +02003711 hibernate= [HIBERNATION]
3712 noresume Don't check if there's a hibernation image
3713 present during boot.
3714 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003715 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003716 protect_image Turn on image protection during restoration
3717 (that will set all pages holding image data
3718 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003719
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003720 retain_initrd [RAM] Keep initrd memory after extraction
3721
Andrew Clausen0efbb782015-01-09 20:24:55 +00003722 rfkill.default_state=
3723 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3724 etc. communication is blocked by default.
3725 1 Unblocked.
3726
3727 rfkill.master_switch_mode=
3728 0 The "airplane mode" button does nothing.
3729 1 The "airplane mode" button toggles between everything
3730 blocked and the previous configuration.
3731 2 The "airplane mode" button toggles between everything
3732 blocked and everything unblocked.
3733
Linus Torvalds1da177e2005-04-16 15:20:36 -07003734 rhash_entries= [KNL,NET]
3735 Set number of hash buckets for route cache
3736
Linus Torvalds1da177e2005-04-16 15:20:36 -07003737 ro [KNL] Mount root device read-only on boot
3738
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003739 rodata= [KNL]
3740 on Mark read-only kernel memory as read-only (default).
3741 off Leave read-only kernel memory writable for debugging.
3742
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003743 rockchip.usb_uart
3744 Enable the uart passthrough on the designated usb port
3745 on Rockchip SoCs. When active, the signals of the
3746 debug-uart get routed to the D+ and D- pins of the usb
3747 port and the regular usb controller gets disabled.
3748
Linus Torvalds1da177e2005-04-16 15:20:36 -07003749 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003750 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003751
3752 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3753 mount the root filesystem
3754
3755 rootflags= [KNL] Set root filesystem mount option string
3756
3757 rootfstype= [KNL] Set root filesystem type
3758
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003759 rootwait [KNL] Wait (indefinitely) for root device to show up.
3760 Useful for devices that are detected asynchronously
3761 (e.g. USB and MMC devices).
3762
Robert Tivy5c71d612013-03-28 18:41:46 -07003763 rproc_mem=nn[KMG][@address]
3764 [KNL,ARM,CMA] Remoteproc physical memory block.
3765 Memory area to be used by remote processor image,
3766 managed by CMA.
3767
Linus Torvalds1da177e2005-04-16 15:20:36 -07003768 rw [KNL] Mount root device read-write on boot
3769
3770 S [KNL] Run init in single mode
3771
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003772 s390_iommu= [HW,S390]
3773 Set s390 IOTLB flushing mode
3774 strict
3775 With strict flushing every unmap operation will result in
3776 an IOTLB flush. Default is lazy flushing before reuse,
3777 which is faster.
3778
Linus Torvalds1da177e2005-04-16 15:20:36 -07003779 sa1100ir [NET]
3780 See drivers/net/irda/sa1100_ir.c.
3781
Linus Torvalds1da177e2005-04-16 15:20:36 -07003782 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003783
Mike Travisf6630112009-11-17 18:22:15 -06003784 sched_debug [KNL] Enables verbose scheduler debug messages.
3785
Mel Gormancb251762016-02-05 09:08:36 +00003786 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3787 Allowed values are enable and disable. This feature
3788 incurs a small amount of overhead in the scheduler
3789 but is useful for debugging and performance tuning.
3790
Mike Galbraith5307c952012-05-08 12:20:58 +02003791 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3792 xtime_lock contention on larger systems, and/or RCU lock
3793 contention on all systems with CONFIG_MAXSMP set.
3794 Format: { "0" | "1" }
3795 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3796 1 -- enable.
3797 Note: increases power consumption, thus should only be
3798 enabled if running jitter sensitive (HPC/RT) workloads.
3799
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003800 security= [SECURITY] Choose a security module to enable at boot.
3801 If this boot parameter is not specified, only the first
3802 security module asking for security registration will be
3803 loaded. An invalid security module name will be treated
3804 as if no module has been chosen.
3805
3806 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003807 Format: { "0" | "1" }
3808 See security/selinux/Kconfig help text.
3809 0 -- disable.
3810 1 -- enable.
3811 Default value is set via kernel config option.
3812 If enabled at boot time, /selinux/disable can be used
3813 later to disable prior to initial policy load.
3814
John Johansenc1c124e2010-07-29 14:48:09 -07003815 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3816 Format: { "0" | "1" }
3817 See security/apparmor/Kconfig help text
3818 0 -- disable.
3819 1 -- enable.
3820 Default value is set via kernel config option.
3821
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003822 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003823
Linus Torvalds1da177e2005-04-16 15:20:36 -07003824 shapers= [NET]
3825 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003826
Yinghai Lub05f78f2008-08-22 01:32:50 -07003827 show_msr= [x86] show boot-time MSR settings
3828 Format: { <integer> }
3829 Show boot-time (BIOS-initialized) MSR settings.
3830 The parameter means the number of CPUs to show,
3831 for example 1 means boot CPU only.
3832
Linus Torvalds1da177e2005-04-16 15:20:36 -07003833 simeth= [IA-64]
3834 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003835
Linus Torvalds1da177e2005-04-16 15:20:36 -07003836 slram= [HW,MTD]
3837
Joonsoo Kim423c9292014-10-09 15:26:22 -07003838 slab_nomerge [MM]
3839 Disable merging of slabs with similar size. May be
3840 necessary if there is some reason to distinguish
3841 allocs to different slabs. Debug options disable
3842 merging on their own.
3843 For more information see Documentation/vm/slub.txt.
3844
David Rientjes3df1ccc2011-10-18 22:09:28 -07003845 slab_max_order= [MM, SLAB]
3846 Determines the maximum allowed order for slabs.
3847 A high setting may cause OOMs due to memory
3848 fragmentation. Defaults to 1 for systems with
3849 more than 32MB of RAM, 0 otherwise.
3850
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003851 slub_debug[=options[,slabs]] [MM, SLUB]
3852 Enabling slub_debug allows one to determine the
3853 culprit if slab objects become corrupted. Enabling
3854 slub_debug can create guard zones around objects and
3855 may poison objects when not in use. Also tracks the
3856 last alloc / free. For more information see
3857 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003858
3859 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003860 Determines the maximum allowed order for slabs.
3861 A high setting may cause OOMs due to memory
3862 fragmentation. For more information see
3863 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003864
3865 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003866 The minimum number of objects per slab. SLUB will
3867 increase the slab order up to slub_max_order to
3868 generate a sufficiently large slab able to contain
3869 the number of objects indicated. The higher the number
3870 of objects the smaller the overhead of tracking slabs
3871 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003872 For more information see Documentation/vm/slub.txt.
3873
3874 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003875 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003876 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003877 For more information see Documentation/vm/slub.txt.
3878
3879 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003880 Same with slab_nomerge. This is supported for legacy.
3881 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003882
Linus Torvalds1da177e2005-04-16 15:20:36 -07003883 smart2= [HW]
3884 Format: <io1>[,<io2>[,...,<io8>]]
3885
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003886 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3887 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3888 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3889 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3890 smsc-ircc2.ircc_irq= [HW] IRQ line
3891 smsc-ircc2.ircc_dma= [HW] DMA channel
3892 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3893 0: Toshiba Satellite 1800 (GP data pin select)
3894 1: Fast pin select (default)
3895 2: ATC IRMode
3896
Sascha Silbe52c48c52016-04-05 12:53:38 +02003897 smt [KNL,S390] Set the maximum number of threads (logical
3898 CPUs) to use per physical CPU on systems capable of
3899 symmetric multithreading (SMT). Will be capped to the
3900 actual hardware limit.
3901 Format: <integer>
3902 Default: -1 (no limit)
3903
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003904 softlockup_panic=
3905 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003906 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003907
Aaron Tomlined235872014-06-23 13:22:05 -07003908 softlockup_all_cpu_backtrace=
3909 [KNL] Should the soft-lockup detector generate
3910 backtraces on all cpus.
3911 Format: <integer>
3912
Linus Torvalds1da177e2005-04-16 15:20:36 -07003913 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003914 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003915
Linus Torvalds1da177e2005-04-16 15:20:36 -07003916 spia_io_base= [HW,MTD]
3917 spia_fio_base=
3918 spia_pedr=
3919 spia_peddr=
3920
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003921 stacktrace [FTRACE]
3922 Enabled the stack tracer on boot up.
3923
Steven Rostedt762e1202011-12-19 22:01:00 -05003924 stacktrace_filter=[function-list]
3925 [FTRACE] Limit the functions that the stack tracer
3926 will trace at boot up. function-list is a comma separated
3927 list of functions. This list can be changed at run
3928 time by the stack_trace_filter file in the debugfs
3929 tracing directory. Note, this enables stack tracing
3930 and the stacktrace above is not needed.
3931
Linus Torvalds1da177e2005-04-16 15:20:36 -07003932 sti= [PARISC,HW]
3933 Format: <num>
3934 Set the STI (builtin display/keyboard on the HP-PARISC
3935 machines) console (graphic card) which should be used
3936 as the initial boot-console.
3937 See also comment in drivers/video/console/sticore.c.
3938
3939 sti_font= [HW]
3940 See comment in drivers/video/console/sticore.c.
3941
3942 stifb= [HW]
3943 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3944
Trond Myklebustcbf11072009-08-09 15:06:19 -04003945 sunrpc.min_resvport=
3946 sunrpc.max_resvport=
3947 [NFS,SUNRPC]
3948 SunRPC servers often require that client requests
3949 originate from a privileged port (i.e. a port in the
3950 range 0 < portnr < 1024).
3951 An administrator who wishes to reserve some of these
3952 ports for other uses may adjust the range that the
3953 kernel's sunrpc client considers to be privileged
3954 using these two parameters to set the minimum and
3955 maximum port values.
3956
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003957 sunrpc.svc_rpc_per_connection_limit=
3958 [NFS,SUNRPC]
3959 Limit the number of requests that the server will
3960 process in parallel from a single connection.
3961 The default value is 0 (no limit).
3962
Greg Banks42a7fc42007-03-06 01:42:23 -08003963 sunrpc.pool_mode=
3964 [NFS]
3965 Control how the NFS server code allocates CPUs to
3966 service thread pools. Depending on how many NICs
3967 you have and where their interrupts are bound, this
3968 option will affect which CPUs will do NFS serving.
3969 Note: this parameter cannot be changed while the
3970 NFS server is running.
3971
3972 auto the server chooses an appropriate mode
3973 automatically using heuristics
3974 global a single global pool contains all CPUs
3975 percpu one pool for each CPU
3976 pernode one pool for each NUMA node (equivalent
3977 to global on non-NUMA machines)
3978
Trond Myklebustcbf11072009-08-09 15:06:19 -04003979 sunrpc.tcp_slot_table_entries=
3980 sunrpc.udp_slot_table_entries=
3981 [NFS,SUNRPC]
3982 Sets the upper limit on the number of simultaneous
3983 RPC calls that can be sent from the client to a
3984 server. Increasing these values may allow you to
3985 improve throughput, but will also increase the
3986 amount of memory reserved for use by the client.
3987
Brian Norris1d4a9c12015-02-22 21:16:49 -08003988 suspend.pm_test_delay=
3989 [SUSPEND]
3990 Sets the number of seconds to remain in a suspend test
3991 mode before resuming the system (see
3992 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3993 is set. Default value is 5.
3994
Michal Hocko07555ac2013-08-22 16:35:46 -07003995 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003996 [KNL] Enable accounting of swap in memory resource
3997 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003998 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003999
Jiri Kosina91fec0f2013-11-27 13:48:09 +01004000 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4001 Format: { <int> | force }
4002 <int> -- Number of I/O TLB slabs
4003 force -- force using of bounce buffers even if they
4004 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07004005
Linus Torvalds1da177e2005-04-16 15:20:36 -07004006 switches= [HW,M68k]
4007
Andi Kleene52eec12010-09-08 16:54:17 +02004008 sysfs.deprecated=0|1 [KNL]
4009 Enable/disable old style sysfs layout for old udev
4010 on older distributions. When this option is enabled
4011 very new udev will not work anymore. When this option
4012 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4013 in older udev will not work anymore.
4014 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4015 the kernel configuration.
4016
Ingo Molnar5d6f6472006-12-13 00:34:36 -08004017 sysrq_always_enabled
4018 [KNL]
4019 Ignore sysrq setting - this boot parameter will
4020 neutralize any effect of /proc/sys/kernel/sysrq.
4021 Useful for debugging.
4022
Fabian Frederick747029a2014-11-06 19:46:50 +01004023 tcpmhash_entries= [KNL,NET]
4024 Set the number of tcp_metrics_hash slots.
4025 Default value is 8192 or 16384 depending on total
4026 ram pages. This is used to specify the TCP metrics
4027 cache size. See Documentation/networking/ip-sysctl.txt
4028 "tcp_no_metrics_save" section for more details.
4029
Linus Torvalds1da177e2005-04-16 15:20:36 -07004030 tdfx= [HW,DRM]
4031
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004032 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07004033 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004034 standby suspend) or "freeze" (for suspend type freeze)
4035 as the system sleep state during system startup with
4036 the optional capability to repeat N number of times.
4037 The system is woken from this state using a
4038 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07004039
Linus Torvalds1da177e2005-04-16 15:20:36 -07004040 thash_entries= [KNL,NET]
4041 Set number of hash buckets for TCP connection
4042
Len Brownf8707ec2007-08-12 00:12:54 -04004043 thermal.act= [HW,ACPI]
4044 -1: disable all active trip points in all thermal zones
4045 <degrees C>: override all lowest active trip points
4046
Len Brownc52a7412007-08-14 15:49:32 -04004047 thermal.crt= [HW,ACPI]
4048 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04004049 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04004050
Len Brownf5487142007-08-12 00:12:44 -04004051 thermal.nocrt= [HW,ACPI]
4052 Set to disable actions on ACPI thermal zone
4053 critical and hot trip points.
4054
Len Brown72b33ef2007-08-12 00:12:17 -04004055 thermal.off= [HW,ACPI]
4056 1: disable ACPI thermal control
4057
Len Browna70cdc52007-08-12 00:12:35 -04004058 thermal.psv= [HW,ACPI]
4059 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08004060 <degrees C>: override all passive trip points to this
4061 value
Len Browna70cdc52007-08-12 00:12:35 -04004062
Len Brown730ff342007-08-12 00:12:26 -04004063 thermal.tzp= [HW,ACPI]
4064 Specify global default ACPI thermal zone polling rate
4065 <deci-seconds>: poll all this frequency
4066 0: no polling (default)
4067
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004068 threadirqs [KNL]
4069 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09004070 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004071
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004072 tmem [KNL,XEN]
4073 Enable the Transcendent memory driver if built-in.
4074
4075 tmem.cleancache=0|1 [KNL, XEN]
4076 Default is on (1). Disable the usage of the cleancache
4077 API to send anonymous pages to the hypervisor.
4078
4079 tmem.frontswap=0|1 [KNL, XEN]
4080 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04004081 API to send swap pages to the hypervisor. If disabled
4082 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004083
4084 tmem.selfballooning=0|1 [KNL, XEN]
4085 Default is on (1). Disable the driving of swap pages
4086 to the hypervisor.
4087
4088 tmem.selfshrinking=0|1 [KNL, XEN]
4089 Default is on (1). Partial swapoff that immediately
4090 transfers pages from Xen hypervisor back to the
4091 kernel based on different criteria.
4092
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004093 topology= [S390]
4094 Format: {off | on}
4095 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07004096 topology information if the hardware supports this.
4097 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004098 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02004099 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004100
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07004101 topology_updates= [KNL, PPC, NUMA]
4102 Format: {off}
4103 Specify if the kernel should ignore (off)
4104 topology updates sent by the hypervisor to this
4105 LPAR.
4106
Linus Torvalds1da177e2005-04-16 15:20:36 -07004107 tp720= [HW,PS2]
4108
Rajiv Andrade225a9be2010-03-25 00:55:32 -03004109 tpm_suspend_pcr=[HW,TPM]
4110 Format: integer pcr id
4111 Specify that at suspend time, the tpm driver
4112 should extend the specified pcr with zeros,
4113 as a workaround for some chips which fail to
4114 flush the last written pcr on TPM_SaveState.
4115 This will guarantee that all the other pcrs
4116 are saved.
4117
Li Zefan9d612be2009-06-24 17:33:15 +08004118 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09004119 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09004120
Li Zefan020e5f82009-07-01 10:47:05 +08004121 trace_event=[event-list]
4122 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07004123 to facilitate early boot debugging. The event-list is a
4124 comma separated list of trace events to enable. See
4125 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08004126
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04004127 trace_options=[option-list]
4128 [FTRACE] Enable or disable tracer options at boot.
4129 The option-list is a comma delimited list of options
4130 that can be enabled or disabled just as if you were
4131 to echo the option name into
4132
4133 /sys/kernel/debug/tracing/trace_options
4134
4135 For example, to enable stacktrace option (to dump the
4136 stack trace of each event), add to the command line:
4137
4138 trace_options=stacktrace
4139
4140 See also Documentation/trace/ftrace.txt "trace options"
4141 section.
4142
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004143 tp_printk[FTRACE]
4144 Have the tracepoints sent to printk as well as the
4145 tracing ring buffer. This is useful for early boot up
4146 where the system hangs or reboots and does not give the
4147 option for reading the tracing buffer or performing a
4148 ftrace_dump_on_oops.
4149
4150 To turn off having tracepoints sent to printk,
4151 echo 0 > /proc/sys/kernel/tracepoint_printk
4152 Note, echoing 1 into this file without the
4153 tracepoint_printk kernel cmdline option has no effect.
4154
4155 ** CAUTION **
4156
4157 Having tracepoints sent to printk() and activating high
4158 frequency tracepoints such as irq or sched, can cause
4159 the system to live lock.
4160
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004161 traceoff_on_warning
4162 [FTRACE] enable this option to disable tracing when a
4163 warning is hit. This turns off "tracing_on". Tracing can
4164 be enabled again by echoing '1' into the "tracing_on"
4165 file located in /sys/kernel/debug/tracing/
4166
4167 This option is useful, as it disables the trace before
4168 the WARNING dump is called, which prevents the trace to
4169 be filled with content caused by the warning output.
4170
4171 This option can also be set at run time via the sysctl
4172 option: kernel/traceoff_on_warning
4173
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004174 transparent_hugepage=
4175 [KNL]
4176 Format: [always|madvise|never]
4177 Can be used to control the default behavior of the system
4178 with respect to transparent hugepages.
4179 See Documentation/vm/transhuge.txt for more details.
4180
john stultzd3b8f882009-08-17 16:40:47 -07004181 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004182 Format: <string>
4183 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004184 disables clocksource verification at runtime, as well
4185 as the stability checks done at bootup. Used to enable
4186 high-resolution timer mode on older hardware, and in
4187 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004188 [x86] noirqtime: Do not use TSC to do irq accounting.
4189 Used to run time disable IRQ_TIME_ACCOUNTING on any
4190 platforms where RDTSC is slow and this accounting
4191 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004192
Randy Dunlapa9913042005-10-23 12:57:11 -07004193 turbografx.map[2|3]= [HW,JOY]
4194 TurboGraFX parallel port interface
4195 Format:
4196 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004197 See also Documentation/input/joystick-parport.txt
4198
Christian Kujaub6935f82011-05-31 15:22:05 +00004199 udbg-immortal [PPC] When debugging early kernel crashes that
4200 happen after console_init() and before a proper
4201 console driver takes over, this boot options might
4202 help "seeing" what's going on.
4203
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004204 uhash_entries= [KNL,NET]
4205 Set number of hash buckets for UDP/UDP-Lite connections
4206
Alan Stern5f8364b2006-12-05 16:29:55 -05004207 uhci-hcd.ignore_oc=
4208 [USB] Ignore overcurrent events (default N).
4209 Some badly-designed motherboards generate lots of
4210 bogus events, for ports that aren't wired to
4211 anything. Set this parameter to avoid log spamming.
4212 Note that genuine overcurrent events won't be
4213 reported either.
4214
Simon Arlotte3a61b02008-07-19 23:32:54 +01004215 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004216 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004217
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004218 usbcore.authorized_default=
4219 [USB] Default USB device authorization:
4220 (default -1 = authorized except for wireless USB,
4221 0 = not authorized, 1 = authorized)
4222
Alan Sternb5e795f2007-02-20 15:00:53 -05004223 usbcore.autosuspend=
4224 [USB] The autosuspend time delay (in seconds) used
4225 for newly-detected USB devices (default 2). This
4226 is the time required before an idle device will be
4227 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004228 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004229
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004230 usbcore.usbfs_snoop=
4231 [USB] Set to log all usbfs traffic (default 0 = off).
4232
Alan Stern0290cc92015-11-20 13:53:22 -05004233 usbcore.usbfs_snoop_max=
4234 [USB] Maximum number of bytes to snoop in each URB
4235 (default = 65536).
4236
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004237 usbcore.blinkenlights=
4238 [USB] Set to cycle leds on hubs (default 0 = off).
4239
4240 usbcore.old_scheme_first=
4241 [USB] Start with the old device initialization
4242 scheme (default 0 = off).
4243
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004244 usbcore.usbfs_memory_mb=
4245 [USB] Memory limit (in MB) for buffers allocated by
4246 usbfs (default = 16, 0 = max = 2047).
4247
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004248 usbcore.use_both_schemes=
4249 [USB] Try the other device initialization scheme
4250 if the first one fails (default 1 = enabled).
4251
4252 usbcore.initial_descriptor_timeout=
4253 [USB] Specifies timeout for the initial 64-byte
4254 USB_REQ_GET_DESCRIPTOR request in milliseconds
4255 (default 5000 = 5.0 seconds).
4256
Oliver Neukum40d58142015-12-03 15:03:32 +01004257 usbcore.nousb [USB] Disable the USB subsystem
4258
Linus Torvalds1da177e2005-04-16 15:20:36 -07004259 usbhid.mousepoll=
4260 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004261
Alan Sternd4f373e2008-11-10 14:07:45 -05004262 usb-storage.delay_use=
4263 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004264 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004265
4266 usb-storage.quirks=
4267 [UMS] A list of quirks entries to supplement or
4268 override the built-in unusual_devs list. List
4269 entries are separated by commas. Each entry has
4270 the form VID:PID:Flags where VID and PID are Vendor
4271 and Product ID values (4-digit hex numbers) and
4272 Flags is a set of characters, each corresponding
4273 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004274 a = SANE_SENSE (collect more than 18 bytes
4275 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004276 b = BAD_SENSE (don't collect more than 18
4277 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004278 c = FIX_CAPACITY (decrease the reported
4279 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004280 d = NO_READ_DISC_INFO (don't use
4281 READ_DISC_INFO command);
4282 e = NO_READ_CAPACITY_16 (don't use
4283 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004284 f = NO_REPORT_OPCODES (don't use report opcodes
4285 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004286 g = MAX_SECTORS_240 (don't transfer more than
4287 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004288 h = CAPACITY_HEURISTICS (decrease the
4289 reported device capacity by one
4290 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004291 i = IGNORE_DEVICE (don't bind to this
4292 device);
Hans de Goede13630742016-04-12 12:27:09 +02004293 j = NO_REPORT_LUNS (don't use report luns
4294 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004295 l = NOT_LOCKABLE (don't try to lock and
4296 unlock ejectable media);
4297 m = MAX_SECTORS_64 (don't transfer more
4298 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004299 n = INITIAL_READ10 (force a retry of the
4300 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004301 o = CAPACITY_OK (accept the capacity
4302 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004303 p = WRITE_CACHE (the device cache is ON
4304 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004305 r = IGNORE_RESIDUE (the device reports
4306 bogus residue values);
4307 s = SINGLE_LUN (the device has only one
4308 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004309 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4310 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004311 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004312 w = NO_WP_DETECT (don't test whether the
4313 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004314 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4315 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004316 Example: quirks=0419:aaf5:rl,0421:0433:rc
4317
Stephen Boydac1667d2011-08-13 12:34:50 -07004318 user_debug= [KNL,ARM]
4319 Format: <int>
4320 See arch/arm/Kconfig.debug help text.
4321 1 - undefined instruction events
4322 2 - system calls
4323 4 - invalid data aborts
4324 8 - SIGSEGV faults
4325 16 - SIGBUS faults
4326 Example: user_debug=31
4327
Ian Campbell14315592010-02-17 10:38:10 +00004328 userpte=
4329 [X86] Flags controlling user PTE allocations.
4330
4331 nohigh = do not allocate PTE pages in
4332 HIGHMEM regardless of setting
4333 of CONFIG_HIGHPTE.
4334
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304335 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004336 On X86_32, this is an alias for vdso32=. Otherwise:
4337
4338 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004339 vdso=0: disable VDSO mapping
4340
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004341 vdso32= [X86] Control the 32-bit vDSO
4342 vdso32=1: enable 32-bit VDSO
4343 vdso32=0 or vdso32=2: disable 32-bit VDSO
4344
4345 See the help text for CONFIG_COMPAT_VDSO for more
4346 details. If CONFIG_COMPAT_VDSO is set, the default is
4347 vdso32=0; otherwise, the default is vdso32=1.
4348
4349 For compatibility with older kernels, vdso32=2 is an
4350 alias for vdso32=0.
4351
4352 Try vdso32=0 if you encounter an error that says:
4353 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004354
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004355 vector= [IA-64,SMP]
4356 vector=percpu: enable percpu vector domain
4357
Linus Torvalds1da177e2005-04-16 15:20:36 -07004358 video= [FB] Frame buffer configuration
4359 See Documentation/fb/modedb.txt.
4360
Aaron Lu3afe6da2013-06-20 15:08:55 +08004361 video.brightness_switch_enabled= [0,1]
4362 If set to 1, on receiving an ACPI notify event
4363 generated by hotkey, video driver will adjust brightness
4364 level and then send out the event to user space through
4365 the allocated input device; If set to 0, video driver
4366 will only send out the event without touching backlight
4367 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004368 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004369
Pawel Moll81a054c2012-05-09 18:30:16 +01004370 virtio_mmio.device=
4371 [VMMIO] Memory mapped virtio (platform) device.
4372
4373 <size>@<baseaddr>:<irq>[:<id>]
4374 where:
4375 <size> := size (can use standard suffixes
4376 like K, M and G)
4377 <baseaddr> := physical base address
4378 <irq> := interrupt number (as passed to
4379 request_irq())
4380 <id> := (optional) platform device id
4381 example:
4382 virtio_mmio.device=1K@0x100b0000:48:7
4383
4384 Can be used multiple times for multiple devices.
4385
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004386 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004387 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004388 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004389 Use vga=ask for menu.
4390 This is actually a boot loader parameter; the value is
4391 passed to the kernel using a special protocol.
4392
Randy Dunlapa9913042005-10-23 12:57:11 -07004393 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004394 size of <nn>. This can be used to increase the
4395 minimum size (128MB on x86). It can also be used to
4396 decrease the size and leave more room for directly
4397 mapped kernel RAM.
4398
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004399 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4400 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004401
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004402 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4403 Format: <command>
4404
4405 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4406 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004407
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004408 vsyscall= [X86-64]
4409 Controls the behavior of vsyscalls (i.e. calls to
4410 fixed addresses of 0xffffffffff600x00 from legacy
4411 code). Most statically-linked binaries and older
4412 versions of glibc use these calls. Because these
4413 functions are at fixed addresses, they make nice
4414 targets for exploits that can control RIP.
4415
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004416 emulate [default] Vsyscalls turn into traps and are
4417 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004418
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004419 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004420 This is a little bit faster than trapping
4421 and makes a few dynamic recompilers work
4422 better than they would in emulation mode.
4423 It also makes exploits much easier to write.
4424
4425 none Vsyscalls don't work at all. This makes
4426 them quite hard to use for exploits but
4427 might break your system.
4428
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004429 vt.color= [VT] Default text color.
4430 Format: 0xYX, X = foreground, Y = background.
4431 Default: 0x07 = light gray on black.
4432
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004433 vt.cur_default= [VT] Default cursor shape.
4434 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4435 the parameters of the <Esc>[?A;B;Cc escape sequence;
4436 see VGA-softcursor.txt. Default: 2 = underline.
4437
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004438 vt.default_blu= [VT]
4439 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4440 Change the default blue palette of the console.
4441 This is a 16-member array composed of values
4442 ranging from 0-255.
4443
4444 vt.default_grn= [VT]
4445 Format: <green0>,<green1>,<green2>,...,<green15>
4446 Change the default green palette of the console.
4447 This is a 16-member array composed of values
4448 ranging from 0-255.
4449
4450 vt.default_red= [VT]
4451 Format: <red0>,<red1>,<red2>,...,<red15>
4452 Change the default red palette of the console.
4453 This is a 16-member array composed of values
4454 ranging from 0-255.
4455
4456 vt.default_utf8=
4457 [VT]
4458 Format=<0|1>
4459 Set system-wide default UTF-8 mode for all tty's.
4460 Default is 1, i.e. UTF-8 mode is enabled for all
4461 newly opened terminals.
4462
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004463 vt.global_cursor_default=
4464 [VT]
4465 Format=<-1|0|1>
4466 Set system-wide default for whether a cursor
4467 is shown on new VTs. Default is -1,
4468 i.e. cursors will be created by default unless
4469 overridden by individual drivers. 0 will hide
4470 cursors, 1 will display them.
4471
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004472 vt.italic= [VT] Default color for italic text; 0-15.
4473 Default: 2 = green.
4474
4475 vt.underline= [VT] Default color for underlined text; 0-15.
4476 Default: 3 = cyan.
4477
Randy Dunlap4724ba572010-05-03 11:42:52 -07004478 watchdog timers [HW,WDT] For information on watchdog timers,
4479 see Documentation/watchdog/watchdog-parameters.txt
4480 or other driver-specific files in the
4481 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004482
Tejun Heo82607adc2015-12-08 11:28:04 -05004483 workqueue.watchdog_thresh=
4484 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4485 warn stall conditions and dump internal state to
4486 help debugging. 0 disables workqueue stall
4487 detection; otherwise, it's the stall threshold
4488 duration in seconds. The default value is 30 and
4489 it can be updated at runtime by writing to the
4490 corresponding sysfs file.
4491
Tejun Heod55262c2013-04-01 11:23:38 -07004492 workqueue.disable_numa
4493 By default, all work items queued to unbound
4494 workqueues are affine to the NUMA nodes they're
4495 issued on, which results in better behavior in
4496 general. If NUMA affinity needs to be disabled for
4497 whatever reason, this option can be used. Note
4498 that this also can be controlled per-workqueue for
4499 workqueues visible under /sys/bus/workqueue/.
4500
Viresh Kumarcee22a12013-04-08 16:45:40 +05304501 workqueue.power_efficient
4502 Per-cpu workqueues are generally preferred because
4503 they show better performance thanks to cache
4504 locality; unfortunately, per-cpu workqueues tend to
4505 be more power hungry than unbound workqueues.
4506
4507 Enabling this makes the per-cpu workqueues which
4508 were observed to contribute significantly to power
4509 consumption unbound, leading to measurably lower
4510 power usage at the cost of small performance
4511 overhead.
4512
4513 The default value of this parameter is determined by
4514 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4515
Tejun Heof303fcc2016-02-09 17:59:38 -05004516 workqueue.debug_force_rr_cpu
4517 Workqueue used to implicitly guarantee that work
4518 items queued without explicit CPU specified are put
4519 on the local CPU. This guarantee is no longer true
4520 and while local CPU is still preferred work items
4521 may be put on foreign CPUs. This debug option
4522 forces round-robin CPU selection to flush out
4523 usages which depend on the now broken guarantee.
4524 When enabled, memory and cache locality will be
4525 impacted.
4526
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004527 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4528 default x2apic cluster mode on platforms
4529 supporting x2apic.
4530
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004531 x86_intel_mid_timer= [X86-32,APBT]
4532 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004533 Two valid options are apbt timer only and lapic timer
4534 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004535 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004536
Juergen Grossc70727a2015-07-17 06:51:36 +02004537 xen_512gb_limit [KNL,X86-64,XEN]
4538 Restricts the kernel running paravirtualized under Xen
4539 to use only up to 512 GB of RAM. The reason to do so is
4540 crash analysis tools and Xen tools for doing domain
4541 save/restore/migration must be enabled to handle larger
4542 domains.
4543
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004544 xen_emul_unplug= [HW,X86,XEN]
4545 Unplug Xen emulated devices
4546 Format: [unplug0,][unplug1]
4547 ide-disks -- unplug primary master IDE devices
4548 aux-ide-disks -- unplug non-primary-master IDE devices
4549 nics -- unplug network devices
4550 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004551 unnecessary -- unplugging emulated devices is
4552 unnecessary even if the host did not respond to
4553 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004554 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004555
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004556 xen_nopvspin [X86,XEN]
4557 Disables the ticketlock slowpath using Xen PV
4558 optimizations.
4559
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004560 xen_nopv [X86]
4561 Disables the PV optimizations forcing the HVM guest to
4562 run as generic HVM guest with no PV drivers.
4563
Linus Torvalds1da177e2005-04-16 15:20:36 -07004564 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004565 Format:
4566 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004567
Randy Dunlapa9913042005-10-23 12:57:11 -07004568______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004569
4570TODO:
4571
Linus Torvalds1da177e2005-04-16 15:20:36 -07004572 Add more DRM drivers.