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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 Zhengc1e94142017-04-04 19:32:17 +0000308 acpi_mask_gpe= [HW,ACPI]
309 Due to the existence of _Lxx/_Exx, some GPEs triggered
310 by unsupported hardware/firmware features can result in
311 GPE floodings that cannot be automatically disabled by
312 the GPE dispatcher.
313 This facility can be used to prevent such uncontrolled
314 GPE floodings.
315 Format: <int>
316 Support masking of GPEs numbered from 0x00 to 0x7f.
317
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800318 acpi_no_auto_serialize [HW,ACPI]
319 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800320 AML control methods that contain the opcodes to create
321 named objects will be marked as "Serialized" by the
322 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800323 This feature is enabled by default.
324 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800325
Dominik Brodowskief694492015-05-14 15:31:28 +0200326 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
327 kernels.
328
Lv Zhenga94e88c2014-04-04 12:39:11 +0800329 acpi_no_static_ssdt [HW,ACPI]
330 Disable installation of static SSDTs at early boot time
331 By default, SSDTs contained in the RSDT/XSDT will be
332 installed automatically and they will appear under
333 /sys/firmware/acpi/tables.
334 This option turns off this feature.
335 Note that specifying this option does not affect
336 dynamic table installation which will install SSDT
337 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700338
Dominik Brodowskief694492015-05-14 15:31:28 +0200339 acpi_rsdp= [ACPI,EFI,KEXEC]
340 Pass the RSDP address to the kernel, mostly used
341 on machines running EFI runtime service to boot the
342 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800343
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700344 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
345 Format: To spoof as Windows 98: ="Microsoft Windows"
346
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200347 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
348 of 2 which is mandated by ACPI 6) as the supported ACPI
349 specification revision (when using this switch, it may
350 be necessary to carry out a cold reboot _twice_ in a
351 row to make it take effect on the platform firmware).
352
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700353 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800354 acpi_osi="string1" # add string1
355 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800356 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800357 acpi_osi=! # disable all built-in OS vendor
358 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800359 acpi_osi=!! # enable all built-in OS vendor
360 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700361 acpi_osi= # disable all strings
362
Lv Zheng5dc17982013-07-22 16:08:25 +0800363 'acpi_osi=!' can be used in combination with single or
364 multiple 'acpi_osi="string1"' to support specific OS
365 vendor string(s). Note that such command can only
366 affect the default state of the OS vendor strings, thus
367 it cannot affect the default state of the feature group
368 strings and the current state of the OS vendor strings,
369 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800370 is meaningless. This command is useful when one do not
371 care about the state of the feature group strings which
372 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800373 Examples:
374 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
375 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
376 can make '_OSI("Windows 2000")' TRUE.
377
378 'acpi_osi=' cannot be used in combination with other
379 'acpi_osi=' command lines, the _OSI method will not
380 exist in the ACPI namespace. NOTE that such command can
381 only affect the _OSI support state, thus specifying it
382 multiple times through kernel command line is also
383 meaningless.
384 Examples:
385 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
386 FALSE.
387
Lv Zheng741d8122013-07-22 16:08:36 +0800388 'acpi_osi=!*' can be used in combination with single or
389 multiple 'acpi_osi="string1"' to support specific
390 string(s). Note that such command can affect the
391 current state of both the OS vendor strings and the
392 feature group strings, thus specifying it multiple times
393 through kernel command line is meaningful. But it may
394 still not able to affect the final state of a string if
395 there are quirks related to this string. This command
396 is useful when one want to control the state of the
397 feature group strings to debug BIOS issues related to
398 the OSPM features.
399 Examples:
400 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
401 '_OSI("Module Device")' FALSE.
402 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
403 '_OSI("Module Device")' TRUE.
404 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
405 equivalent to
406 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
407 and
408 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
409 they all will make '_OSI("Windows 2000")' TRUE.
410
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530411 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700412 Override the pmtimer bug detection: force the kernel
413 to assume that this machine's pmtimer latches its value
414 and always returns good values.
415
Randy Dunlap4af94f32009-04-17 18:30:28 -0700416 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
417 Format: { level | edge | high | low }
418
Randy Dunlap4af94f32009-04-17 18:30:28 -0700419 acpi_skip_timer_override [HW,ACPI]
420 Recognize and ignore IRQ0/pin2 Interrupt Override.
421 For broken nForce2 BIOS resulting in XT-PIC timer.
422
423 acpi_sleep= [HW,ACPI] Sleep options
424 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200425 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700426 See Documentation/power/video.txt for information on
427 s3_bios and s3_mode.
428 s3_beep is for debugging; it makes the PC's speaker beep
429 as soon as the kernel's real-mode entry point is called.
430 s4_nohwsig prevents ACPI hardware signature from being
431 used during resume from hibernation.
432 old_ordering causes the ACPI 1.0 ordering of the _PTS
433 control method, with respect to putting devices into
434 low power states, to be enforced (the ACPI 2.0 ordering
435 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200436 nonvs prevents the kernel from saving/restoring the
437 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800438 sci_force_enable causes the kernel to set SCI_EN directly
439 on resume from S1/S3 (which is against the ACPI spec,
440 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700441
442 acpi_use_timer_override [HW,ACPI]
443 Use timer override. For some broken Nvidia NF5 boards
444 that require a timer override, but don't have HPET
445
Randy Dunlap4af94f32009-04-17 18:30:28 -0700446 add_efi_memmap [EFI; X86] Include EFI memory map in
447 kernel's map of available physical RAM.
448
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700449 agp= [AGP]
450 { off | try_unsupported }
451 off: disable AGP support
452 try_unsupported: try to drive unsupported chipsets
453 (may crash computer or cause data corruption)
454
Randy Dunlapbcfde332010-06-07 17:10:38 -0700455 ALSA [HW,ALSA]
456 See Documentation/sound/alsa/alsa-parameters.txt
457
Russell Kingd944d542010-02-20 16:13:29 +0000458 alignment= [KNL,ARM]
459 Allow the default userspace alignment fault handler
460 behaviour to be specified. Bit 0 enables warnings,
461 bit 1 enables fixups, and bit 2 sends a segfault.
462
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200463 align_va_addr= [X86-64]
464 Align virtual addresses by clearing slice [14:12] when
465 allocating a VMA at process creation time. This option
466 gives you up to 3% performance improvement on AMD F15h
467 machines (where it is enabled by default) for a
468 CPU-intensive style benchmark, and it can vary highly in
469 a microbenchmark depending on workload and compiler.
470
Borislav Petkov8360ee22011-11-21 12:10:19 +0100471 32: only for 32-bit processes
472 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200473 on: enable for both 32- and 64-bit processes
474 off: disable for both 32- and 64-bit processes
475
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500476 alloc_snapshot [FTRACE]
477 Allocate the ftrace snapshot buffer on boot up when the
478 main buffer is allocated. This is handy if debugging
479 and you need to use tracing_snapshot() on boot up, and
480 do not want to use tracing_snapshot_alloc() as it needs
481 to be done where GFP_KERNEL allocations are allowed.
482
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100483 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200484 Pass parameters to the AMD IOMMU driver in the system.
485 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900486 fullflush - enable flushing of IO/TLB entries when
487 they are unmapped. Otherwise they are
488 flushed before they will be reused, which
489 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200490 off - do not initialize any AMD IOMMU found in
491 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100492 force_isolation - Force device isolation for all
493 devices. The IOMMU driver is not
494 allowed anymore to lift isolation
495 requirements as needed. This option
496 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900497
Shuah Khanc099cf12012-05-24 15:58:25 -0600498 amd_iommu_dump= [HW,X86-64]
499 Enable AMD IOMMU driver option to dump the ACPI table
500 for AMD IOMMU. With this option enabled, AMD IOMMU
501 driver will print ACPI tables for AMD IOMMU during
502 IOMMU initialization.
503
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500504 amd_iommu_intr= [HW,X86-64]
505 Specifies one of the following AMD IOMMU interrupt
506 remapping modes:
507 legacy - Use legacy interrupt remapping mode.
508 vapic - Use virtual APIC mode, which allows IOMMU
509 to inject interrupts directly into guest.
510 This mode requires kvm-amd.avic=1.
511 (Default when IOMMU HW support is present.)
512
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 amijoy.map= [HW,JOY] Amiga joystick support
514 Map of devices attached to JOY0DAT and JOY1DAT
515 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200516 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517
518 analog.map= [HW,JOY] Analog joystick and gamepad support
519 Specifies type or capabilities of an analog joystick
520 connected to one of 16 gameports
521 Format: <type1>,<type2>,..<type16>
522
Randy Dunlapa9913042005-10-23 12:57:11 -0700523 apc= [HW,SPARC]
524 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 Format: noidle
526 Disable APC CPU standby support. SPARCstation-Fox does
527 not play well with APC CPU idle - disable it if you have
528 APC and your system crashes randomly.
529
Randy Dunlapca1eda22009-05-06 16:02:58 -0700530 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700531 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 Format: { quiet (default) | verbose | debug }
533 Change the amount of debugging information output
534 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700535
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100536 apic_extnmi= [APIC,X86] External NMI delivery setting
537 Format: { bsp (default) | all | none }
538 bsp: External NMI is delivered only to CPU 0
539 all: External NMIs are broadcast to all CPUs as a
540 backup of CPU 0
541 none: External NMI is masked for all CPUs. This is
542 useful so that a dump capture kernel won't be
543 shot down by NMI
544
Brian Haleyb0f83b22010-02-04 13:36:50 -0800545 autoconf= [IPV6]
546 See Documentation/networking/ipv6.txt.
547
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400548 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
549 Limit apic dumping. The parameter defines the maximal
550 number of local apics being dumped. Also it is possible
551 to set it to "all" by meaning -- no limit here.
552 Format: { 1 (default) | 2 | ... | all }.
553 The parameter valid if only apic=debug or
554 apic=verbose is specified.
555 Example: apic=debug show_lapic=all
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700558 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
561 Format: <io>,<irq>,<nodeID>
562
563 ataflop= [HW,M68k]
564
565 atarimouse= [HW,MOUSE] Atari Mouse
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
568 EzKey and similar keyboards
569
570 atkbd.reset= [HW] Reset keyboard during initialization
571
Randy Dunlapa9913042005-10-23 12:57:11 -0700572 atkbd.set= [HW] Select keyboard code set
573 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574
575 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
576 keyboards
577
578 atkbd.softraw= [HW] Choose between synthetic and real raw mode
579 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700580
581 atkbd.softrepeat= [HW]
582 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400584 audit= [KNL] Enable the audit sub-system
585 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500586 0 - kernel audit is disabled and can not be enabled
587 until the next reboot
588 unset - kernel audit is initialized but disabled and
589 will be fully enabled by the userspace auditd.
590 1 - kernel audit is initialized and partially enabled,
591 storing at most audit_backlog_limit messages in
592 RAM until it is fully enabled by the userspace
593 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400594 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400595
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400596 audit_backlog_limit= [KNL] Set the audit queue size limit.
597 Format: <int> (must be >=0)
598 Default: 64
599
Alex Thorlton1c532e02016-03-31 14:18:29 -0500600 bau= [X86_UV] Enable the BAU on SGI UV. The default
601 behavior is to disable the BAU (i.e. bau=0).
602 Format: { "0" | "1" }
603 0 - Disable the BAU.
604 1 - Enable the BAU.
605 unset - Disable the BAU.
606
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 baycom_epp= [HW,AX25]
608 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700609
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
611 Format: <io>,<mode>
612 See header of drivers/net/hamradio/baycom_par.c.
613
Randy Dunlapa9913042005-10-23 12:57:11 -0700614 baycom_ser_fdx= [HW,AX25]
615 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 Format: <io>,<irq>,<mode>[,<baud>]
617 See header of drivers/net/hamradio/baycom_ser_fdx.c.
618
Randy Dunlapa9913042005-10-23 12:57:11 -0700619 baycom_ser_hdx= [HW,AX25]
620 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700621 Format: <io>,<irq>,<mode>
622 See header of drivers/net/hamradio/baycom_ser_hdx.c.
623
Paul Gortmaker080506a2013-09-30 13:45:19 -0700624 blkdevparts= Manual partition parsing of block device(s) for
625 embedded devices based on command line input.
626 See Documentation/block/cmdline-partition.txt
627
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700628 boot_delay= Milliseconds to delay each printk during boot.
629 Values larger than 10 seconds (10000) are changed to
630 no delay (0).
631 Format: integer
632
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700633 bootmem_debug [KNL] Enable bootmem allocator debug messages.
634
Huang Yinga3e2acc2016-06-29 13:04:29 -0700635 bert_disable [ACPI]
636 Disable BERT OS support on buggy BIOSes.
637
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700639 bttv.radio= Most important insmod options are available as
640 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200642 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000644 bulk_remove=off [PPC] This parameter disables the use of the pSeries
645 firmware feature for flushing multiple hpte entries
646 at a time.
647
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648 c101= [NET] Moxa C101 synchronous serial card
649
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700650 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 Sometimes CPU hardware bugs make them report the cache
652 size incorrectly. The kernel will attempt work arounds
653 to fix known problems, but for some CPUs it is not
654 possible to determine what the correct size should be.
655 This option provides an override for these situations.
656
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300657 ca_keys= [KEYS] This parameter identifies a specific key(s) on
658 the system trusted keyring to be used for certificate
659 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300660 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300661
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700662 cca= [MIPS] Override the kernel pages' cache coherency
663 algorithm. Accepted values range from 0 to 7
664 inclusive. See arch/mips/include/asm/pgtable-bits.h
665 for platform specific values (SB1, Loongson3 and
666 others).
667
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100668 ccw_timeout_log [S390]
669 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670
Paul Menage8bab8dd2008-04-04 14:29:57 -0700671 cgroup_disable= [KNL] Disable a particular controller
672 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800673 The effects of cgroup_disable=foo are:
674 - foo isn't auto-mounted if you mount all cgroups in
675 a single hierarchy
676 - foo isn't visible as an individually mountable
677 subsystem
678 {Currently only "memory" controller deal with this and
679 cut the overhead, others just disable the usage. So
680 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700681
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500682 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
683 Format: { controller[,controller...] | "all" }
684 Like cgroup_disable, but only applies to cgroup v1;
685 the blacklisted controllers remain available in cgroup2.
686
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800687 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
688 Format: <string>
689 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800690 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800691
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 checkreqprot [SELINUX] Set initial checkreqprot flag value.
693 Format: { "0" | "1" }
694 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700695 0 -- check protection applied by kernel (includes
696 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697 1 -- check protection requested by application.
698 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700699 Value can be changed at runtime via
700 /selinux/checkreqprot.
701
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100702 cio_ignore= [S390]
703 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700704 clk_ignore_unused
705 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700706 Prevents the clock framework from automatically gating
707 clocks that have not been explicitly enabled by a Linux
708 device driver but are enabled in hardware at reset or
709 by the bootloader/firmware. Note that this does not
710 force such clocks to be always-on nor does it reserve
711 those clocks in any way. This parameter is useful for
712 debug and development, but should not be needed on a
713 platform with proper driver support. For more
714 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100715
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700716 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700717 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200718 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700719 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200720 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721 Format: { pit | tsc | cyclone | pmtmr }
722
John Stultz592913e2010-07-13 17:56:20 -0700723 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700724 Format: <string>
725 Override the default clocksource and use the clocksource
726 with the name specified.
727 Some clocksource names to choose from, depending on
728 the platform:
729 [all] jiffies (this is the base, fallback clocksource)
730 [ACPI] acpi_pm
731 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
732 pxa_timer,timer3,32k_counter,timer0_1
733 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700734 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700735 scx200_hrt on Geode; cyclone on IBM x440
736 [MIPS] MIPS
737 [PARISC] cr16
738 [S390] tod
739 [SH] SuperH
740 [SPARC64] tick
741 [X86-64] hpet,tsc
742
Will Deacon46fd5c62016-06-27 17:30:13 +0100743 clocksource.arm_arch_timer.evtstrm=
744 [ARM,ARM64]
745 Format: <bool>
746 Enable/disable the eventstream feature of the ARM
747 architected timer so that code using WFE-based polling
748 loops can be debugged more effectively on production
749 systems.
750
Scott Woodf6dc1572016-09-22 03:35:17 -0500751 clocksource.arm_arch_timer.fsl-a008585=
752 [ARM64]
753 Format: <bool>
754 Enable/disable the workaround of Freescale/NXP
755 erratum A-008585. This can be useful for KVM
756 guests, if the guest device tree doesn't show the
757 erratum. If unspecified, the workaround is
758 enabled based on the device tree.
759
Andi Kleenac72e782008-01-30 13:33:21 +0100760 clearcpuid=BITNUM [X86]
761 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100762 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800763 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100764 stable over kernel options, but the vendor specific
765 ones should be.
766 Also note that user programs calling CPUID directly
767 or using the feature without checking anything
768 will still see it. This just prevents it from
769 being used by the kernel or shown in /proc/cpuinfo.
770 Also note the kernel might malfunction if you disable
771 some critical bits.
772
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700773 cma=nn[MG]@[start[MG][-end[MG]]]
774 [ARM,X86,KNL]
775 Sets the size of kernel global memory area for
776 contiguous memory allocations and optionally the
777 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700778 memory allocations. A value of 0 disables CMA
779 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100780 include/linux/dma-contiguous.h
781
Robert Jennings14f966e2009-04-15 05:55:32 +0000782 cmo_free_hint= [PPC] Format: { yes | no }
783 Specify whether pages are marked as being inactive
784 when they are freed. This is used in CMO environments
785 to determine OS memory pressure for page stealing by
786 a hypervisor.
787 Default: yes
788
Marek Szyprowskic7909502011-12-29 13:09:51 +0100789 coherent_pool=nn[KMG] [ARM,KNL]
790 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200791 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100792
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530793 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100794 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100795 Range: 0 - 8192
796 Default: 64
797
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700799 Format:
800 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801
802 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
803 Format: <io>[,<irq>]
804
Randy Dunlapa9913042005-10-23 12:57:11 -0700805 com90xx= [HW,NET]
806 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 Format: <io>[,<irq>[,<memstart>]]
808
809 condev= [HW,S390] console device
810 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700811
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 console= [KNL] Output console device and options.
813
814 tty<n> Use the virtual console device <n>.
815
816 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800817 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800819 the form "bbbbpnf", where "bbbb" is the baud rate,
820 "p" is parity ("n", "o", or "e"), "n" is number of
821 bits, and "f" is flow control ("r" for RTS or
822 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800824 See Documentation/serial-console.txt for more
825 information. See
826 Documentation/networking/netconsole.txt for an
827 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700829 uart[8250],io,<addr>[,options]
830 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900831 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400832 uart[8250],mmio32,<addr>[,options]
833 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834 Start an early, polled-mode console on the 8250/16550
835 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400836 switching to the matching ttyS device later.
837 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900838 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
839 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
840 to be equivalent to 'mmio'. 'options' are specified in
841 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400842 the h/w is not re-initialized.
843
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500844 hvc<n> Use the hypervisor console device <n>. This is for
845 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700847 If the device connected to the port is not a TTY but a braille
848 device, prepend "brl," before the device type, for instance
849 console=brl,ttyS0
850 For now, only VisioBraille is supported.
851
Daniel Mackf324edc2009-06-16 15:33:52 -0700852 consoleblank= [KNL] The console blank (screen saver) timeout in
853 seconds. Defaults to 10*60 = 10mins. A value of 0
854 disables the blank timer.
855
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800856 coredump_filter=
857 [KNL] Change the default value for
858 /proc/<pid>/coredump_filter.
859 See also Documentation/filesystems/proc.txt.
860
Len Brown62027ae2011-04-01 18:13:10 -0400861 cpuidle.off=1 [CPU_IDLE]
862 disable the cpuidle sub-system
863
Len Brownd68921f2015-05-11 17:27:09 -0400864 cpu_init_udelay=N
865 [X86] Delay for N microsec between assert and de-assert
866 of APIC INIT to start processors. This delay occurs
867 on every CPU online, such as boot, and resume from suspend.
868 Default: 10000
869
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700871 Format:
872 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700873
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800874 crashkernel=size[KMG][@offset[KMG]]
875 [KNL] Using kexec, Linux can switch to a 'crash kernel'
876 upon panic. This parameter reserves the physical
877 memory region [offset, offset + size] for that kernel
878 image. If '@offset' is omitted, then a suitable offset
879 is selected automatically. Check
880 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700881
Bernhard Wallefb391592007-10-18 23:41:02 -0700882 crashkernel=range1:size1[,range2:size2,...][@offset]
883 [KNL] Same as above, but depends on the memory
884 in the running system. The syntax of range is
885 start-[end] where start and end are both
886 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800887 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700888
Yinghai Luadbc7422013-04-15 22:23:48 -0700889 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700890 [KNL, x86_64] range could be above 4G. Allow kernel
891 to allocate physical memory region from top, so could
892 be above 4G if system have more than 4G ram installed.
893 Otherwise memory region will be allocated below 4G, if
894 available.
895 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700896 crashkernel=size[KMG],low
897 [KNL, x86_64] range under 4G. When crashkernel=X,high
898 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700899 above 4G, that cause second kernel crash on system
900 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800901 requires at least 64M+32K low memory, also enough extra
902 low memory is needed to make sure DMA buffers for 32-bit
903 devices won't run out. Kernel would try to allocate at
904 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700905 This one let user to specify own low range under 4G
906 for second kernel instead.
907 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700908 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700909 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700910
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100911 cryptomgr.notests
912 [KNL] Disable crypto self-tests
913
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914 cs89x0_dma= [HW,NET]
915 Format: <dma>
916
917 cs89x0_media= [HW,NET]
918 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700919
Randy Dunlapa9913042005-10-23 12:57:11 -0700920 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700921 See header of drivers/s390/block/dasd_devmap.c.
922
923 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
924 (one device per port)
925 Format: <port#>,<type>
926 See also Documentation/input/joystick-parport.txt
927
Thomas Renningera648ec02010-08-06 16:11:02 +0200928 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
929 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600930 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200931
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 debug [KNL] Enable kernel debugging (events log level).
933
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700934 debug_locks_verbose=
935 [KNL] verbose self-tests
936 Format=<0|1>
937 Print debugging info while doing the locking API
938 self-tests.
939 We default to 0 (no extra messages), setting it to
940 1 will print _a lot_ more information - normally
941 only useful to kernel developers.
942
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700943 debug_objects [KNL] Enable object debugging
944
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500945 no_debug_objects
946 [KNL] Disable object debugging
947
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800948 debug_guardpage_minorder=
949 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
950 parameter allows control of the order of pages that will
951 be intentionally kept free (and hence protected) by the
952 buddy allocator. Bigger value increase the probability
953 of catching random memory corruption, but reduce the
954 amount of memory for normal system use. The maximum
955 possible value is MAX_ORDER/2. Setting this parameter
956 to 1 or 2 should be enough to identify most random
957 memory corruption problems caused by bugs in kernel or
958 driver code when a CPU writes to (or reads from) a
959 random memory location. Note that there exists a class
960 of memory corruptions problems caused by buggy H/W or
961 F/W or by drivers badly programing DMA (basically when
962 memory is written at bus level and the CPU MMU is
963 bypassed) which are not detectable by
964 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
965 tracking down these problems.
966
Joonsoo Kim031bc572014-12-12 16:55:52 -0800967 debug_pagealloc=
968 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
969 parameter enables the feature at boot time. In
970 default, it is disabled. We can avoid allocating huge
971 chunk of memory for debug pagealloc if we don't enable
972 it at boot time and the system will work mostly same
973 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
974 on: enable the feature
975
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200976 debugpat [X86] Enable PAT debugging
977
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200978 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979 Format: <area>[,<node>]
980 See also Documentation/networking/decnet.txt.
981
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700982 default_hugepagesz=
983 [same as hugepagesz=] The size of the default
984 HugeTLB page size. This is the size represented by
985 the legacy /proc/ hugepages APIs, used for SHM, and
986 default size when mounting hugetlbfs filesystems.
987 Defaults to the default architecture's huge page size
988 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700989
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990 dhash_entries= [KNL]
991 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700992
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000993 disable_1tb_segments [PPC]
994 Disables the use of 1TB hash page table segments. This
995 causes the kernel to fall back to 256MB segments which
996 can be useful when debugging issues that require an SLB
997 miss to occur.
998
Brian Haleyb0f83b22010-02-04 13:36:50 -0800999 disable= [IPV6]
1000 See Documentation/networking/ipv6.txt.
1001
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +05301002 disable_radix [PPC]
1003 Disable RADIX MMU mode on POWER9
1004
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +09001005 disable_cpu_apicid= [X86,APIC,SMP]
1006 Format: <int>
1007 The number of initial APIC ID for the
1008 corresponding CPU to be disabled at boot,
1009 mostly used for the kdump 2nd kernel to
1010 disable BSP to wake up multiple CPUs without
1011 causing system reset or hang due to sending
1012 INIT from AP to BSP.
1013
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +00001014 disable_ddw [PPC/PSERIES]
1015 Disable Dynamic DMA Window support. Use this if
1016 to workaround buggy firmware.
1017
Brian Haleyb0f83b22010-02-04 13:36:50 -08001018 disable_ipv6= [IPV6]
1019 See Documentation/networking/ipv6.txt.
1020
Yinghai Lu95ffa242008-04-29 03:52:33 -07001021 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -07001022 The kernel tries to adjust MTRR layout from continuous
1023 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001024 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -07001025
Yinghai Lu093af8d2008-01-30 13:33:32 +01001026 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +01001027 By default the kernel will trim any uncacheable
1028 memory out of your available memory pool based on
1029 MTRR settings. This parameter disables that behavior,
1030 possibly causing your machine to run very slowly.
1031
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301032 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001033 Disable PIN 1 of APIC timer
1034 Can be useful to work around chipset bugs.
1035
Prarit Bhargavace14c582015-08-25 13:34:53 -04001036 dis_ucode_ldr [X86] Disable the microcode loader.
1037
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001038 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1039 this option disables the debugging code at boot.
1040
1041 dma_debug_entries=<number>
1042 This option allows to tune the number of preallocated
1043 entries for DMA-API debugging code. One entry is
1044 required per DMA-API allocation. Use this if the
1045 DMA-API debugging code disables itself because the
1046 architectural default is too low.
1047
Joerg Roedel1745de52009-05-22 21:49:51 +02001048 dma_debug_driver=<driver_name>
1049 With this option the DMA-API debugging driver
1050 filter feature can be enabled at boot time. Just
1051 pass the driver to filter for as the parameter.
1052 The filter can be disabled or changed to another
1053 driver later using sysfs.
1054
Bob Paauwe96206e22015-08-27 10:04:13 -07001055 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1056 Broken monitors, graphic adapters, KVMs and EDIDless
1057 panels may send no or incorrect EDID data sets.
1058 This parameter allows to specify an EDID data sets
1059 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +01001060 Generic built-in EDID data sets are used, if one of
1061 edid/1024x768.bin, edid/1280x1024.bin,
1062 edid/1680x1050.bin, or edid/1920x1080.bin is given
1063 and no file with the same name exists. Details and
1064 instructions how to build your own EDID data are
1065 available in Documentation/EDID/HOWTO.txt. An EDID
1066 data set will only be used for a particular connector,
1067 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -07001068 name. Each connector may use a unique EDID data
1069 set by separating the files with a comma. An EDID
1070 data set with no connector name will be used for
1071 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +01001072
Linus Torvalds1da177e2005-04-16 15:20:36 -07001073 dscc4.setup= [NET]
1074
Jim Cromie29e36c92012-04-27 14:30:41 -06001075 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1076 module.dyndbg[="val"]
1077 Enable debug messages at boot time. See
1078 Documentation/dynamic-debug-howto.txt for details.
1079
Dave Hansen8c3641e2015-06-07 11:37:02 -07001080 nompx [X86] Disables Intel Memory Protection Extensions.
1081 See Documentation/x86/intel_mpx.txt for more
1082 information about the feature.
1083
Dave Hansen06976942016-02-12 13:02:29 -08001084 nopku [X86] Disable Memory Protection Keys CPU feature found
1085 in some Intel CPUs.
1086
Borislav Petkovf29ba612015-03-27 16:15:18 +01001087 eagerfpu= [X86]
1088 on enable eager fpu restore
1089 off disable eager fpu restore
1090 auto selects the default scheme, which automatically
1091 enables eagerfpu restore for xsaveopt.
1092
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -07001093 module.async_probe [KNL]
1094 Enable asynchronous probe on this module.
1095
Mark Salter56aeeba2014-04-07 15:39:53 -07001096 early_ioremap_debug [KNL]
1097 Enable debug messages in early_ioremap support. This
1098 is useful for tracking down temporary early mappings
1099 which are not unmapped.
1100
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001101 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -05001102
Scott Wood5664f762015-09-14 19:54:07 -05001103 When used with no options, the early console is
1104 determined by the stdout-path property in device
1105 tree's chosen node.
1106
Scott Telfordc41251b2016-09-22 16:58:16 +01001107 cdns,<addr>[,options]
1108 Start an early, polled-mode console on a Cadence
1109 (xuartps) serial port at the specified address. Only
1110 supported option is baud rate. If baud rate is not
1111 specified, the serial port must already be setup and
1112 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +02001113
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001114 uart[8250],io,<addr>[,options]
1115 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -07001116 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +03001117 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -04001118 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001119 Start an early, polled-mode console on the 8250/16550
1120 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -07001121 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +03001122 (mmio) or 32-bit (mmio32 or mmio32be).
1123 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1124 to be equivalent to 'mmio'. 'options' are specified
1125 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -04001126 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001127
Rob Herring0d3c6732014-04-18 17:19:57 -05001128 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -06001129 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -05001130 Start an early, polled-mode console on a pl011 serial
1131 port at the specified address. The pl011 serial port
1132 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -06001133 yet supported. If 'mmio32' is specified, then only
1134 the driver will use only 32-bit accessors to read/write
1135 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -05001136
Andreas Färber736d5532016-03-06 12:21:24 +01001137 meson,<addr>
1138 Start an early, polled-mode console on a meson serial
1139 port at the specified address. The serial port must
1140 already be setup and configured. Options are not yet
1141 supported.
1142
Stephen Boyd0efe7292014-09-15 17:22:51 -07001143 msm_serial,<addr>
1144 Start an early, polled-mode console on an msm serial
1145 port at the specified address. The serial port
1146 must already be setup and configured. Options are not
1147 yet supported.
1148
1149 msm_serial_dm,<addr>
1150 Start an early, polled-mode console on an msm serial
1151 dm port at the specified address. The serial port
1152 must already be setup and configured. Options are not
1153 yet supported.
1154
Rob Herringd50d7262014-04-18 17:19:58 -05001155 smh Use ARM semihosting calls for early console.
1156
Tomasz Figab94ba032015-01-23 14:47:41 +01001157 s3c2410,<addr>
1158 s3c2412,<addr>
1159 s3c2440,<addr>
1160 s3c6400,<addr>
1161 s5pv210,<addr>
1162 exynos4210,<addr>
1163 Use early console provided by serial driver available
1164 on Samsung SoCs, requires selecting proper type and
1165 a correct base address of the selected UART port. The
1166 serial port must already be setup and configured.
1167 Options are not yet supported.
1168
Stefan Agner1d59b382015-10-17 00:45:55 -07001169 lpuart,<addr>
1170 lpuart32,<addr>
1171 Use early console provided by Freescale LP UART driver
1172 found on Freescale Vybrid and QorIQ LS1021A processors.
1173 A valid base address must be provided, and the serial
1174 port must already be setup and configured.
1175
Wilson Ding30530792016-02-16 19:14:53 +01001176 armada3700_uart,<addr>
1177 Start an early, polled-mode console on the
1178 Armada 3700 serial port at the specified
1179 address. The serial port must already be setup
1180 and configured. Options are not yet supported.
1181
Finn Thain7913ad12014-04-12 23:48:56 +10001182 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +01001184 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001185 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -07001187 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -05001188 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -05001189 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +06001190 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191
Dave Hansen147ea092013-04-10 14:03:38 -07001192 earlyprintk is useful when the kernel crashes before
1193 the normal console is initialized. It is not enabled by
1194 default because it has some cosmetic problems.
1195
Randy Dunlapa9913042005-10-23 12:57:11 -07001196 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197 takes over.
1198
Matt Fleming72548e82013-10-04 09:36:56 +01001199 Only one of vga, efi, serial, or usb debug port can
1200 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001201
Dave Hansen147ea092013-04-10 14:03:38 -07001202 Currently only ttyS0 and ttyS1 may be specified by
1203 name. Other I/O ports may be explicitly specified
1204 on some architectures (x86 and arm at least) by
1205 replacing ttySn with an I/O port address, like this:
1206 earlyprintk=serial,0x1008,115200
1207 You can find the port for a given device in
1208 /proc/tty/driver/serial:
1209 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210
1211 Interaction with the standard serial driver is not
1212 very good.
1213
Matt Fleming72548e82013-10-04 09:36:56 +01001214 The VGA and EFI output is eventually overwritten by
1215 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001216
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001217 The xen output can only be used by Xen PV guests.
1218
Chen, Gongc700f012013-12-06 01:17:08 -05001219 edac_report= [HW,EDAC] Control how to report EDAC event
1220 Format: {"on" | "off" | "force"}
1221 on: enable EDAC to report H/W event. May be overridden
1222 by other higher priority error reporting module.
1223 off: disable H/W event reporting through EDAC.
1224 force: enforce the use of EDAC to report H/W event.
1225 default: on.
1226
Jason Wessel97311912010-05-20 21:04:30 -05001227 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1228 ekgdboc=kbd
1229
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001230 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001231 the boot argument: earlyprintk=vga
1232
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001234 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001236 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001237 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001238 old_map [X86-64]: switch to the old ioremap-based EFI
1239 runtime services mapping. 32-bit still uses this one by
1240 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001241 nochunk: disable reading files in "chunks" in the EFI
1242 boot stub, as chunking can cause problems with some
1243 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001244 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001245 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001246
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001247 efi_no_storage_paranoia [EFI; X86]
1248 Using this parameter you can use more than 50% of
1249 your efi variable storage. Use this parameter only if
1250 you are really sure that your UEFI does sane gc and
1251 fulfills the spec otherwise your board may brick.
1252
Taku Izumi0f96a992015-09-30 23:01:56 +09001253 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1254 Add arbitrary attribute to specific memory range by
1255 updating original EFI memory map.
1256 Region of memory which aa attribute is added to is
1257 from ss to ss+nn.
1258 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1259 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1260 attribute is added to range 0x100000000-0x180000000 and
1261 0x10a0000000-0x1120000000.
1262
1263 Using this parameter you can do debugging of EFI memmap
1264 related feature. For example, you can do debugging of
1265 Address Range Mirroring feature even if your box
1266 doesn't support it.
1267
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001268 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1269 that is to be dynamically loaded by Linux. If there are
1270 multiple variables with the same name but with different
1271 vendor GUIDs, all of them will be loaded. See
1272 Documentation/acpi/ssdt-overlays.txt for details.
1273
1274
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275 eisa_irq_edge= [PARISC,HW]
1276 See header of drivers/parisc/eisa.c.
1277
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001278 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001280 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281
1282 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001283 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001284 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001285 Documentation/block/deadline-iosched.txt for details.
1286
Michael Holzheud3bf37952011-10-30 15:16:37 +01001287 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001288 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001289 image elf header and optionally the size. Generally
1290 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001291 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001293 enable_mtrr_cleanup [X86]
1294 The kernel tries to adjust MTRR layout from continuous
1295 to discrete, to make X server driver able to add WB
1296 entry later. This parameter enables that.
1297
Randy Dunlapca1eda22009-05-06 16:02:58 -07001298 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001299 Enable PIN 1 of APIC timer
1300 Can be useful to work around chipset bugs
1301 (in particular on some ATI chipsets).
1302 The kernel tries to set a reasonable default.
1303
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304 enforcing [SELINUX] Set initial enforcing status.
1305 Format: {"0" | "1"}
1306 See security/selinux/Kconfig help text.
1307 0 -- permissive (log only, no denials).
1308 1 -- enforcing (deny and log).
1309 Default value is 0.
1310 Value can be changed at runtime via /selinux/enforce.
1311
Huang Yinga08f82d2010-05-18 14:35:21 +08001312 erst_disable [ACPI]
1313 Disable Error Record Serialization Table (ERST)
1314 support.
1315
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 ether= [HW,NET] Ethernet cards parameters
1317 This option is obsoleted by the "netdev=" option, which
1318 has equivalent usage. See its documentation for details.
1319
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001320 evm= [EVM]
1321 Format: { "fix" }
1322 Permit 'security.evm' to be updated regardless of
1323 current integrity status.
1324
Akinobu Mitade1ba092006-12-08 02:39:42 -08001325 failslab=
1326 fail_page_alloc=
1327 fail_make_request=[KNL]
1328 General fault injection mechanism.
1329 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001330 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001331
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001333 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334
Alex Chiangf13ae302008-05-08 14:03:23 -06001335 force_pal_cache_flush
1336 [IA-64] Avoid check_sal_cache_flush which may hang on
1337 buggy SAL_CACHE_FLUSH implementations. Using this
1338 parameter will force ia64_sal_cache_flush to call
1339 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1340
Chris Bainbridge69f23662014-03-07 18:40:42 +07001341 forcepae [X86-32]
1342 Forcefully enable Physical Address Extension (PAE).
1343 Many Pentium M systems disable PAE but may have a
1344 functionally usable PAE implementation.
1345 Warning: use of this parameter will taint the kernel
1346 and may cause unknown problems.
1347
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001348 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001349 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001350 as early as possible in order to facilitate early
1351 boot debugging.
1352
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001353 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001354 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001355 If no parameter is passed, ftrace will dump
1356 buffers of all CPUs, but if you pass orig_cpu, it will
1357 dump only the buffer of the CPU that triggered the
1358 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001359
1360 ftrace_filter=[function-list]
1361 [FTRACE] Limit the functions traced by the function
1362 tracer at boot up. function-list is a comma separated
1363 list of functions. This list can be changed at run
1364 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001365 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001366
1367 ftrace_notrace=[function-list]
1368 [FTRACE] Do not trace the functions specified in
1369 function-list. This list can be changed at run time
1370 by the set_ftrace_notrace file in the debugfs
1371 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001372
Stefan Assmann369bc182009-10-12 22:17:21 +02001373 ftrace_graph_filter=[function-list]
1374 [FTRACE] Limit the top level callers functions traced
1375 by the function graph tracer at boot up.
1376 function-list is a comma separated list of functions
1377 that can be changed at run time by the
1378 set_graph_function file in the debugfs tracing directory.
1379
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001380 ftrace_graph_notrace=[function-list]
1381 [FTRACE] Do not trace from the functions specified in
1382 function-list. This list is a comma separated list of
1383 functions that can be changed at run time by the
1384 set_graph_notrace file in the debugfs tracing directory.
1385
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386 gamecon.map[2|3]=
1387 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1388 support via parallel port (up to 5 devices per port)
1389 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1390 See also Documentation/input/joystick-parport.txt
1391
1392 gamma= [HW,DRM]
1393
Yinghai Luaaf23042008-01-30 13:33:09 +01001394 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1395 Format: off | on
1396 default: on
1397
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001398 gcov_persist= [GCOV] When non-zero (default), profiling data for
1399 kernel modules is saved and remains accessible via
1400 debugfs, even when the module is unloaded/reloaded.
1401 When zero, profiling data is discarded and associated
1402 debugfs files are removed at module unload time.
1403
Thomas Gleixner2709c2a2017-02-15 11:11:50 +01001404 goldfish [X86] Enable the goldfish android emulator platform.
1405 Don't use this when you are not running on the
1406 android emulator
1407
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001409 invalid Protective MBR to be treated as GPT. If the
1410 primary GPT is corrupted, it enables the backup/alternate
1411 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001413 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1414 the "Enable 0" bit of the configuration register.
1415 Format: 0 | 1
1416 Default: 0
1417 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1418 the "Enable 0" bit of the configuration register.
1419 Format: 0 | 1
1420 Default: 0
1421 grcan.select= [HW] Select which physical interface to use.
1422 Format: 0 | 1
1423 Default: 0
1424 grcan.txsize= [HW] Sets the size of the tx buffer.
1425 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1426 Default: 1024
1427 grcan.rxsize= [HW] Sets the size of the rx buffer.
1428 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1429 Default: 1024
1430
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001431 gpio-mockup.gpio_mockup_ranges
1432 [HW] Sets the ranges of gpiochip of for this device.
1433 Format: <start1>,<end1>,<start2>,<end2>...
1434
Jiri Kosina55537872015-11-05 18:44:41 -08001435 hardlockup_all_cpu_backtrace=
1436 [KNL] Should the hard-lockup detector generate
1437 backtraces on all cpus.
1438 Format: <integer>
1439
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440 hashdist= [KNL,NUMA] Large hashes allocated during boot
1441 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001442 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001443 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444
1445 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1446
1447 hd= [EIDE] (E)IDE hard drive subsystem geometry
1448 Format: <cyl>,<head>,<sect>
1449
Huang Yingea8c0712010-05-18 14:35:15 +08001450 hest_disable [ACPI]
1451 Disable Hardware Error Source Table (HEST) support;
1452 corresponding firmware-first mode error processing
1453 logic will be disabled.
1454
Linus Torvalds1da177e2005-04-16 15:20:36 -07001455 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1456 size of <nn>. This works even on boxes that have no
1457 highmem otherwise. This also works to reduce highmem
1458 size on bigger boxes.
1459
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001460 highres= [KNL] Enable/disable high resolution timer mode.
1461 Valid parameters: "on", "off"
1462 Default: "on"
1463
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 hisax= [HW,ISDN]
1465 See Documentation/isdn/README.HiSax.
1466
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001467 hlt [BUGS=ARM,SH]
1468
1469 hpet= [X86-32,HPET] option to control HPET usage
1470 Format: { enable (default) | disable | force |
1471 verbose }
1472 disable: disable HPET and use PIT instead
1473 force: allow force enabled of undocumented chips (ICH4,
1474 VIA, nVidia)
1475 verbose: show contents of HPET registers during setup
1476
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001477 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1478 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1479
Andi Kleenb4718e62008-07-23 21:27:51 -07001480 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1481 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001482 On x86-64 and powerpc, this option can be specified
1483 multiple times interleaved with hugepages= to reserve
1484 huge pages of different sizes. Valid pages sizes on
1485 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001486 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001487
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001488 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1489 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001490 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1491 If specified, z/VM IUCV HVC accepts connections
1492 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001493
James Hoganfdabf522012-10-09 11:00:27 +01001494 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1495 hardware thread id mappings.
1496 Format: <cpu>:<hwthread>
1497
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001498 keep_bootcon [KNL]
1499 Do not unregister boot console at start. This is only
1500 useful for debugging when something happens in the window
1501 between unregistering the boot console and initializing
1502 the real console.
1503
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001504 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001505 or register an additional I2C bus that is not
1506 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001507 Format:
1508 <bus_id>,<clkrate>
1509
Jiri Kosina36d95732008-10-06 02:51:09 -04001510 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001511 i8042.unmask_kbd_data
1512 [HW] Enable printing of interrupt data from the KBD port
1513 (disabled by default, and as a pre-condition
1514 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001516 i8042.dumbkbd [HW] Pretend that controller can only read data from
1517 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518 (Don't attempt to blink the leds)
1519 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001520 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001521 i8042.noloop [HW] Disable the AUX Loopback command while probing
1522 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001524 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1526 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001527 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e1922016-10-01 12:07:35 -07001528 i8042.reset [HW] Reset the controller during init, cleanup and
1529 suspend-to-ram transitions, only during s2r
1530 transitions, or never reset
1531 Format: { 1 | Y | y | 0 | N | n }
1532 1, Y, y: always reset controller
1533 0, N, n: don't ever reset controller
1534 Default: only on s2r transitions on x86; most other
1535 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001536 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001537 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001538
1539 i810= [HW,DRM]
1540
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001541 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1542 indicates that the driver is running on unsupported
1543 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1545 does not match list of supported models.
1546 i8k.power_status
1547 [HW] Report power status in /proc/i8k
1548 (disabled by default)
1549 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1550 capability is set.
1551
Carsten Emde4dca20e2012-03-15 15:56:26 +01001552 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001553 [DRM] Invert the sense of the variable that is used to
1554 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001555 brightness value of 0 indicates backlight switched off,
1556 and the maximum of the brightness value sets the backlight
1557 to maximum brightness. If this parameter is set to 0
1558 (default) and the machine requires it, or this parameter
1559 is set to 1, a brightness value of 0 sets the backlight
1560 to maximum brightness, and the maximum of the brightness
1561 value switches the backlight off.
1562 -1 -- never invert brightness
1563 0 -- machine default
1564 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001565
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566 icn= [HW,ISDN]
1567 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1568
David Fries0af80c02009-02-25 20:28:21 +01001569 ide-core.nodma= [HW] (E)IDE subsystem
1570 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001571 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1572 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001573 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001575 ide-generic.probe-mask= [HW] (E)IDE subsystem
1576 Format: <int>
1577 Probe mask for legacy ISA IDE ports. Depending on
1578 platform up to 6 ports are supported, enabled by
1579 setting corresponding bits in the mask to 1. The
1580 default value is 0x0, which has a special meaning.
1581 On systems that have PCI, it triggers scanning the
1582 PCI bus for the first and the second port, which
1583 are then probed. On systems without PCI the value
1584 of 0x0 enables probing the two first ports as if it
1585 was 0x3.
1586
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001587 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1588 Claim all unknown PCI IDE storage controllers.
1589
Andi Kleenf039b752007-05-02 19:27:12 +02001590 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001591 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001592 Poll forces a polling idle loop that can slightly
1593 improve the performance of waking up a idle CPU, but
1594 will use a lot of power and make the system run hot.
1595 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001596 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001597 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001598 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001599
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001600 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1601 Format: { strict | legacy | 2008 | relaxed }
1602 Default: strict
1603
1604 Choose which programs will be accepted for execution
1605 based on the IEEE 754 NaN encoding(s) supported by
1606 the FPU and the NaN encoding requested with the value
1607 of an ELF file header flag individually set by each
1608 binary. Hardware implementations are permitted to
1609 support either or both of the legacy and the 2008 NaN
1610 encoding mode.
1611
1612 Available settings are as follows:
1613 strict accept binaries that request a NaN encoding
1614 supported by the FPU
1615 legacy only accept legacy-NaN binaries, if supported
1616 by the FPU
1617 2008 only accept 2008-NaN binaries, if supported
1618 by the FPU
1619 relaxed accept any binaries regardless of whether
1620 supported by the FPU
1621
1622 The FPU emulator is always able to support both NaN
1623 encodings, so if no FPU hardware is present or it has
1624 been disabled with 'nofpu', then the settings of
1625 'legacy' and '2008' strap the emulator accordingly,
1626 'relaxed' straps the emulator for both legacy-NaN and
1627 2008-NaN, whereas 'strict' enables legacy-NaN only on
1628 legacy processors and both NaN encodings on MIPS32 or
1629 MIPS64 CPUs.
1630
1631 The setting for ABS.fmt/NEG.fmt instruction execution
1632 mode generally follows that for the NaN encoding,
1633 except where unsupported by hardware.
1634
Ingo Molnar792908222006-12-06 20:40:51 -08001635 ignore_loglevel [KNL]
1636 Ignore loglevel setting - this will print /all/
1637 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001638 We also add it as printk module parameter, so users
1639 could change it dynamically, usually by
1640 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001641
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001642 ignore_rlimit_data
1643 Ignore RLIMIT_DATA setting for data mappings,
1644 print warning at first misuse. Can be changed via
1645 /sys/module/kernel/parameters/ignore_rlimit_data.
1646
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 ihash_entries= [KNL]
1648 Set number of hash buckets for inode cache.
1649
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001650 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001651 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001652 default: "enforce"
1653
Mimi Zohar07f6a792011-03-09 22:25:48 -05001654 ima_appraise_tcb [IMA]
1655 The builtin appraise policy appraises all files
1656 owned by uid=0.
1657
Mimi Zohar3323eec92009-02-04 09:06:58 -05001658 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001659 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1660 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001661 default: "sha1"
1662
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001663 The list of supported hash algorithms is defined
1664 in crypto/hash_info.h.
1665
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001666 ima_policy= [IMA]
1667 The builtin measurement policy to load during IMA
1668 setup. Specyfing "tcb" as the value, measures all
1669 programs exec'd, files mmap'd for exec, and all files
1670 opened with the read mode bit set by either the
1671 effective uid (euid=0) or uid=0.
1672 Format: "tcb"
1673
1674 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001675 Load a policy which meets the needs of the Trusted
1676 Computing Base. This means IMA will measure all
1677 programs exec'd, files mmap'd for exec, and all files
1678 opened for read by uid=0.
1679
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001680 ima_template= [IMA]
1681 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001682 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001683 Default: "ima-ng"
1684
Roberto Sassuc2426d22014-10-13 14:08:42 +02001685 ima_template_fmt=
1686 [IMA] Define a custom template format.
1687 Format: { "field1|...|fieldN" }
1688
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001689 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1690 Format: <min_file_size>
1691 Set the minimal file size for using asynchronous hash.
1692 If left unspecified, ahash usage is disabled.
1693
1694 ahash performance varies for different data sizes on
1695 different crypto accelerators. This option can be used
1696 to achieve the best performance for a particular HW.
1697
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001698 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1699 Format: <bufsize>
1700 Set hashing buffer size. Default: 4k.
1701
1702 ahash performance varies for different chunk sizes on
1703 different crypto accelerators. This option can be used
1704 to achieve best performance for particular HW.
1705
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706 init= [KNL]
1707 Format: <full_path>
1708 Run specified binary instead of /sbin/init as init
1709 process.
1710
1711 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1712 for working out where the kernel is dying during
1713 startup.
1714
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001715 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1716 initcall functions. Useful for debugging built-in
1717 modules and initcalls.
1718
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719 initrd= [BOOT] Specify the location of the initial ramdisk
1720
Dave Hansenacd547b2016-07-29 09:30:21 -07001721 init_pkru= [x86] Specify the default memory protection keys rights
1722 register contents for all processes. 0x55555554 by
1723 default (disallow access to all but pkey 0). Can
1724 override in debugfs after boot.
1725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1727 Format: <irq>
1728
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001729 int_pln_enable [x86] Enable power limit notification interrupt
1730
Mimi Zohard726d8d2013-03-18 14:48:02 -04001731 integrity_audit=[IMA]
1732 Format: { "0" | "1" }
1733 0 -- basic integrity auditing messages. (Default)
1734 1 -- additional integrity auditing messages.
1735
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001736 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001737 on
1738 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001739 off
1740 Disable intel iommu driver.
1741 igfx_off [Default Off]
1742 By default, gfx is mapped as normal device. If a gfx
1743 device has a dedicated DMAR unit, the DMAR unit is
1744 bypassed by not enabling DMAR with this option. In
1745 this case, gfx device will use physical address for
1746 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001747 forcedac [x86_64]
1748 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001749 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001750 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001751 than 32-bit addressing. The default is to look
1752 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001753 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001754 strict [Default Off]
1755 With this option on every unmap_single operation will
1756 result in a hardware IOTLB flush operation as opposed
1757 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001758 sp_off [Default Off]
1759 By default, super page will be supported if Intel IOMMU
1760 has the capability. With this option, super page will
1761 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001762 ecs_off [Default Off]
1763 By default, extended context tables will be supported if
1764 the hardware advertises that it has support both for the
1765 extended tables themselves, and also PASID support. With
1766 this option set, extended tables will not be used even
1767 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001768
1769 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1770 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001771 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001772
Dirk Brandewie6be26492013-02-15 22:55:10 +01001773 intel_pstate= [X86]
1774 disable
1775 Do not enable intel_pstate as the default
1776 scaling driver for the supported processors
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001777 force
1778 Enable intel_pstate on systems that prohibit it by default
1779 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1780 instead of acpi-cpufreq may disable platform features, such
1781 as thermal controls and power capping, that rely on ACPI
1782 P-States information being indicated to OSPM and therefore
1783 should be used with caution. This option does not work with
1784 processors that aren't supported by the intel_pstate driver
1785 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001786 no_hwp
1787 Do not enable hardware P state control (HWP)
1788 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001789 hwp_only
1790 Only load intel_pstate on systems which support
1791 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001792 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001793 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1794 Description Table, specifies preferred power management
1795 profile as "Enterprise Server" or "Performance Server",
1796 then this feature is turned on by default.
Dirk Brandewie6be26492013-02-15 22:55:10 +01001797
Chris Wrightd1423d52010-07-20 11:06:49 -07001798 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001799 on enable Interrupt Remapping (default)
1800 off disable Interrupt Remapping
1801 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001802 no_x2apic_optout
1803 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001804 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001805
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001806 iomem= Disable strict checking of access to MMIO memory
1807 strict regions from userspace.
1808 relaxed
1809
1810 iommu= [x86]
1811 off
1812 force
1813 noforce
1814 biomerge
1815 panic
1816 nopanic
1817 merge
1818 nomerge
1819 forcesac
1820 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001821 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001822 nobypass [PPC/POWERNV]
1823 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001824
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001825
1826 io7= [HW] IO7 for Marvel based alpha systems
1827 See comment before marvel_specify_io7 in
1828 arch/alpha/kernel/core_marvel.c.
1829
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301830 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001831 0x80
1832 Standard port 0x80 based delay
1833 0xed
1834 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001835 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001836 Simple two microseconds delay
1837 none
1838 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001839
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001841 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001842
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001843 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001844 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001845
Alan Cox200803d2005-06-28 20:45:18 -07001846 irqfixup [HW]
1847 When an interrupt is not handled search all handlers
1848 for it. Intended to get systems with badly broken
1849 firmware running.
1850
1851 irqpoll [HW]
1852 When an interrupt is not handled search all handlers
1853 for it. Also check all handlers each timer
1854 interrupt. Intended to get systems with badly broken
1855 firmware running.
1856
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001858 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001859
1860 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001861 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001862
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 This option can be used to specify one or more CPUs
1864 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001865 algorithms. You can move a process onto or off an
1866 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867 <cpu number> begins at 0 and the maximum value is
1868 "number of CPUs in system - 1".
1869
1870 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001871 alternative -- manually setting the CPU mask of all
1872 tasks in the system -- can cause problems and
1873 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001874
Randy Dunlapa9913042005-10-23 12:57:11 -07001875 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001876
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001877 ivrs_ioapic [HW,X86_64]
1878 Provide an override to the IOAPIC-ID<->DEVICE-ID
1879 mapping provided in the IVRS ACPI table. For
1880 example, to map IOAPIC-ID decimal 10 to
1881 PCI device 00:14.0 write the parameter as:
1882 ivrs_ioapic[10]=00:14.0
1883
1884 ivrs_hpet [HW,X86_64]
1885 Provide an override to the HPET-ID<->DEVICE-ID
1886 mapping provided in the IVRS ACPI table. For
1887 example, to map HPET-ID decimal 0 to
1888 PCI device 00:14.0 write the parameter as:
1889 ivrs_hpet[0]=00:14.0
1890
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001891 ivrs_acpihid [HW,X86_64]
1892 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1893 mapping provided in the IVRS ACPI table. For
1894 example, to map UART-HID:UID AMD0020:0 to
1895 PCI device 00:14.5 write the parameter as:
1896 ivrs_acpihid[00:14.5]=AMD0020:0
1897
Linus Torvalds1da177e2005-04-16 15:20:36 -07001898 js= [HW,JOY] Analog joystick
1899 See Documentation/input/joystick.txt.
1900
Kees Cook65fe9352016-06-13 15:10:02 -07001901 nokaslr [KNL]
1902 When CONFIG_RANDOMIZE_BASE is set, this disables
1903 kernel and module base offset ASLR (Address Space
1904 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001905
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001906 keepinitrd [HW,ARM]
1907
Taku Izumi342332e2016-03-15 14:55:22 -07001908 kernelcore= [KNL,X86,IA-64,PPC]
1909 Format: nn[KMGTPE] | "mirror"
1910 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001911 specifies the amount of memory usable by the kernel
1912 for non-movable allocations. The requested amount is
1913 spread evenly throughout all nodes in the system. The
1914 remaining memory in each node is used for Movable
1915 pages. In the event, a node is too small to have both
1916 kernelcore and Movable pages, kernelcore pages will
1917 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001918 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001919 allocation of pages that may be reclaimed or moved
1920 by the page migration subsystem. This means that
1921 HugeTLB pages may not be allocated from this zone.
1922 Note that allocations like PTEs-from-HighMem still
1923 use the HighMem zone if it exists, and the Normal
1924 zone if it does not.
1925
Taku Izumi342332e2016-03-15 14:55:22 -07001926 Instead of specifying the amount of memory (nn[KMGTPE]),
1927 you can specify "mirror" option. In case "mirror"
1928 option is specified, mirrored (reliable) memory is used
1929 for non-movable allocations and remaining memory is used
1930 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1931 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1932 time.
1933
Jason Wessel4fe1da42010-05-20 21:04:31 -05001934 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1935 Format: <Controller#>[,poll interval]
1936 The controller # is the number of the ehci usb debug
1937 port as it is probed via PCI. The poll interval is
1938 optional and is the number seconds in between
1939 each poll cycle to the debug port in case you need
1940 the functionality for interrupting the kernel with
1941 gdb or control-c on the dbgp connection. When
1942 not using this parameter you use sysrq-g to break into
1943 the kernel debugger.
1944
Jason Wessel84c08fd2010-05-20 21:04:24 -05001945 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001946 Requires a tty driver that supports console polling,
1947 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001948 Serial only format: <serial_device>[,baud]
1949 keyboard only format: kbd
1950 keyboard and serial format: kbd,<serial_device>[,baud]
1951 Optional Kernel mode setting:
1952 kms, kbd format: kms,kbd
1953 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001954
Jason Wessel84c08fd2010-05-20 21:04:24 -05001955 kgdbwait [KGDB] Stop kernel execution and enter the
1956 kernel debugger at the earliest opportunity.
1957
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001958 kmac= [MIPS] korina ethernet MAC address.
1959 Configure the RouterBoard 532 series on-chip
1960 Ethernet adapter MAC address.
1961
Catalin Marinas04f70332009-06-11 13:22:39 +01001962 kmemleak= [KNL] Boot-time kmemleak enable/disable
1963 Valid arguments: on, off
1964 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001965 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1966 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001967
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001968 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1969 Valid arguments: 0, 1, 2
1970 kmemcheck=0 (disabled)
1971 kmemcheck=1 (enabled)
1972 kmemcheck=2 (one-shot mode)
1973 Default: 2 (one-shot mode)
1974
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301975 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001976 in oops dumps.
1977
Andre Przywarafef07aa2009-07-10 14:20:35 +02001978 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1979 Default is 0 (don't ignore, but inject #GP)
1980
Xiao Guangronga182d872010-09-20 22:17:48 +08001981 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1982 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001983 Default is 0 (off)
1984
Andre Przywarafef07aa2009-07-10 14:20:35 +02001985 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001986 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001987
1988 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1989 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001990 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001991
Andre Przywarafef07aa2009-07-10 14:20:35 +02001992 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1993 (virtualized MMU) support on capable Intel chips.
1994 Default is 1 (enabled)
1995
1996 kvm-intel.emulate_invalid_guest_state=
1997 [KVM,Intel] Enable emulation of invalid guest states
1998 Default is 0 (disabled)
1999
2000 kvm-intel.flexpriority=
2001 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2002 Default is 1 (enabled)
2003
Sasha Levine1a72ae2011-08-09 14:28:35 +03002004 kvm-intel.nested=
2005 [KVM,Intel] Enable VMX nesting (nVMX).
2006 Default is 0 (disabled)
2007
Andre Przywarafef07aa2009-07-10 14:20:35 +02002008 kvm-intel.unrestricted_guest=
2009 [KVM,Intel] Disable unrestricted guest feature
2010 (virtualized real and unpaged mode) on capable
2011 Intel chips. Default is 1 (enabled)
2012
2013 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2014 feature (tagged TLBs) on capable Intel chips.
2015 Default is 1 (enabled)
2016
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 l2cr= [PPC]
2018
Robert Brosea78bfbf2008-03-29 07:20:23 +11002019 l3cr= [PPC]
2020
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002021 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07002022 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023
Suresh Siddha279f1462012-10-22 14:37:58 -07002024 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2025 value for LAPIC timer one-shot implementation. Default
2026 back to the programmable timer unit in the LAPIC.
2027
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302028 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002029 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01002030
FD Camifcb71f62008-01-06 19:08:56 +01002031 libata.dma= [LIBATA] DMA control
2032 libata.dma=0 Disable all PATA and SATA DMA
2033 libata.dma=1 PATA and SATA Disk DMA only
2034 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07002035 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01002036 Combinations also work, so libata.dma=3 enables DMA
2037 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07002038
Michael Prokop20308872009-08-06 00:14:10 +02002039 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2040 libata.ignore_hpa=0 keep BIOS limits (default)
2041 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01002042
Dave Jones78e70c22007-09-27 11:50:13 -04002043 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2044 when set.
2045 Format: <int>
2046
Tejun Heo33267322008-02-13 09:15:09 +09002047 libata.force= [LIBATA] Force configurations. The format is comma
2048 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02002049 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09002050 matching port, link or device. Basically, it matches
2051 the ATA ID string printed on console by libata. If
2052 the whole ID part is omitted, the last PORT and DEVICE
2053 values are used. If ID hasn't been specified yet, the
2054 configuration applies to all ports, links and devices.
2055
2056 If only DEVICE is omitted, the parameter applies to
2057 the port and all links and devices behind it. DEVICE
2058 number of 0 either selects the first device or the
2059 first fan-out link behind PMP device. It does not
2060 select the host link. DEVICE number of 15 selects the
2061 host link and device attached to it.
2062
2063 The VAL specifies the configuration to force. As long
2064 as there's no ambiguity shortcut notation is allowed.
2065 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2066 The following configurations can be forced.
2067
2068 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2069 Any ID with matching PORT is used.
2070
2071 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2072
2073 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2074 udma[/][16,25,33,44,66,100,133] notation is also
2075 allowed.
2076
2077 * [no]ncq: Turn on or off NCQ.
2078
Martin K. Petersend7b16e42015-05-04 21:54:18 -04002079 * [no]ncqtrim: Turn off queued DSM TRIM.
2080
Tejun Heo05944bd2008-08-13 20:19:09 +09002081 * nohrst, nosrst, norst: suppress hard, soft
2082 and both resets.
2083
Dan Williamsca6d43b2012-06-21 23:41:41 -07002084 * rstonce: only attempt one reset during
2085 hot-unplug link recovery
2086
Tejun Heo43c9c592010-05-23 12:59:11 +02002087 * dump_id: dump IDENTIFY data.
2088
Vincent Pelletier966fbe12013-05-21 22:30:58 +02002089 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2090
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08002091 * disable: Disable this device.
2092
Tejun Heo33267322008-02-13 09:15:09 +09002093 If there are multiple matching configurations changing
2094 the same attribute, the last one is used.
2095
Yinghai Lu95f72d12010-07-12 14:36:09 +10002096 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002097
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002099 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002101 lockd.nlm_grace_period=P [NFS] Assign grace period.
2102 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103
Randy Dunlapa6b25b62006-01-14 13:21:19 -08002104 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2105 Format: <integer>
2106
2107 lockd.nlm_timeout=T [NFS] Assign timeout value.
2108 Format: <integer>
2109
2110 lockd.nlm_udpport=M [NFS] Assign UDP port.
2111 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07002113 locktorture.nreaders_stress= [KNL]
2114 Set the number of locking read-acquisition kthreads.
2115 Defaults to being automatically set based on the
2116 number of online CPUs.
2117
2118 locktorture.nwriters_stress= [KNL]
2119 Set the number of locking write-acquisition kthreads.
2120
2121 locktorture.onoff_holdoff= [KNL]
2122 Set time (s) after boot for CPU-hotplug testing.
2123
2124 locktorture.onoff_interval= [KNL]
2125 Set time (s) between CPU-hotplug operations, or
2126 zero to disable CPU-hotplug testing.
2127
2128 locktorture.shuffle_interval= [KNL]
2129 Set task-shuffle interval (jiffies). Shuffling
2130 tasks allows some CPUs to go into dyntick-idle
2131 mode during the locktorture test.
2132
2133 locktorture.shutdown_secs= [KNL]
2134 Set time (s) after boot system shutdown. This
2135 is useful for hands-off automated testing.
2136
2137 locktorture.stat_interval= [KNL]
2138 Time (s) between statistics printk()s.
2139
2140 locktorture.stutter= [KNL]
2141 Time (s) to stutter testing, for example,
2142 specifying five seconds causes the test to run for
2143 five seconds, wait for five seconds, and so on.
2144 This tests the locking primitive's ability to
2145 transition abruptly to and from idle.
2146
2147 locktorture.torture_runnable= [BOOT]
2148 Start locktorture running at boot time.
2149
2150 locktorture.torture_type= [KNL]
2151 Specify the locking implementation to test.
2152
2153 locktorture.verbose= [KNL]
2154 Enable additional printk() statements.
2155
Linus Torvalds1da177e2005-04-16 15:20:36 -07002156 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2157 Format: <irq>
2158
2159 loglevel= All Kernel Messages with a loglevel smaller than the
2160 console loglevel will be printed to the console. It can
2161 also be changed with klogd or other programs. The
2162 loglevels are defined as follows:
2163
2164 0 (KERN_EMERG) system is unusable
2165 1 (KERN_ALERT) action must be taken immediately
2166 2 (KERN_CRIT) critical conditions
2167 3 (KERN_ERR) error conditions
2168 4 (KERN_WARNING) warning conditions
2169 5 (KERN_NOTICE) normal but significant condition
2170 6 (KERN_INFO) informational
2171 7 (KERN_DEBUG) debug-level messages
2172
Randy Dunlapc756d082011-02-20 20:08:35 -08002173 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07002174 in bytes. n must be a power of two and greater
2175 than the minimal size. The minimal size is defined
2176 by LOG_BUF_SHIFT kernel config parameter. There is
2177 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2178 that allows to increase the default size depending on
2179 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180
Randy Dunlapaccaa242007-10-16 01:29:37 -07002181 logo.nologo [FB] Disables display of the built-in Linux logo.
2182 This may be used to provide more screen space for
2183 kernel log messages and is useful when debugging
2184 kernel boot problems.
2185
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186 lp=0 [LP] Specify parallel ports to use, e.g,
2187 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2188 lp=reset first parallel port). 'lp=0' disables the
2189 lp=auto printer driver. 'lp=reset' (which can be
2190 specified in addition to the ports) causes
2191 attached printers to be reset. Using
2192 lp=port1,port2,... specifies the parallel ports
2193 to associate lp devices with, starting with
2194 lp0. A port specification may be 'none' to skip
2195 that lp device, or a parport name such as
2196 'parport0'. Specifying 'lp=auto' instead of a
2197 port specification list means that device IDs
2198 from each port should be examined, to see if
2199 an IEEE 1284-compliant printer is attached; if
2200 so, the driver will manage that printer.
2201 See also header of drivers/char/lp.c.
2202
2203 lpj=n [KNL]
2204 Sets loops_per_jiffy to given constant, thus avoiding
2205 time-consuming boot-time autodetection (up to 250 ms per
2206 CPU). 0 enables autodetection (default). To determine
2207 the correct value for your kernel, boot with normal
2208 autodetection and see what value is printed. Note that
2209 on SMP systems the preset will be applied to all CPUs,
2210 which is likely to cause problems if your CPUs need
2211 significantly divergent settings. An incorrect value
2212 will cause delays in the kernel to be wrong, leading to
2213 unpredictable I/O errors and other breakage. Although
2214 unlikely, in the extreme case this might damage your
2215 hardware.
2216
2217 ltpc= [NET]
2218 Format: <io>,<irq>,<dma>
2219
Randy Dunlap16290242011-08-13 12:34:52 -07002220 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002221 (machvec) in a generic kernel.
2222 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002223
Wu Zhangjin3209e702009-07-02 23:27:12 +08002224 machtype= [Loongson] Share the same kernel image file between different
2225 yeeloong laptop.
2226 Example: machtype=lemote-yeeloong-2f-7inch
2227
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002228 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2229 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002230
2231 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002232 will bring up during bootup. maxcpus=n : n >= 0 limits
2233 the kernel to bring up 'n' processors. Surely after
2234 bootup you can bring up the other plugged cpu by executing
2235 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2236 only takes effect during system bootup.
2237 While n=0 is a special case, it is equivalent to "nosmp",
2238 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239
Kay Sieversd134b002011-07-31 22:08:04 +02002240 max_loop= [LOOP] The number of loop block devices that get
2241 (loop.max_loop) unconditionally pre-created at init time. The default
2242 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2243 of statically allocating a predefined number, loop
2244 devices can be requested on-demand with the
2245 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002246
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002247 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248
Uwe Hermann71cced62008-10-20 09:32:21 -07002249 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002250
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251 md= [HW] RAID subsystems devices and level
2252 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002253
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254 mdacon= [MDA]
2255 Format: <first>,<last>
2256 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002257
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2259 Amount of memory to be used when the kernel is not able
2260 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002261 [X86] Work as limiting max address. Use together
2262 with memmap= to avoid physical address space collisions.
2263 Without memmap= PCI devices could be placed at addresses
2264 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002266 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267 memory.
2268
Paul Mundt6902aa82008-09-21 17:14:42 +09002269 memchunk=nn[KMG]
2270 [KNL,SH] Allow user to override the default size for
2271 per-device physically contiguous DMA buffers.
2272
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002273 memhp_default_state=online/offline
2274 [KNL] Set the initial state for the memory hotplug
2275 onlining policy. If not specified, the default value is
2276 set according to the
2277 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2278 option.
2279 See Documentation/memory-hotplug.txt.
2280
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302281 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 E820 memory map, as specified by the user.
2283 Such memmap=exactmap lines can be constructed based on
2284 BIOS output or other requirements. See the memmap=nn@ss
2285 option description.
2286
2287 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002288 [KNL] Force usage of a specific region of memory.
2289 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002290
2291 memmap=nn[KMG]#ss[KMG]
2292 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002293 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002294
2295 memmap=nn[KMG]$ss[KMG]
2296 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002297 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002298 Example: Exclude memory from 0x18690000-0x1869ffff
2299 memmap=64K$0x18690000
2300 or
2301 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002302
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002303 memmap=nn[KMG]!ss[KMG]
2304 [KNL,X86] Mark specific memory as protected.
2305 Region of memory to be used, from ss to ss+nn.
2306 The memory region may be marked as e820 type 12 (0xc)
2307 and is NVDIMM or ADR memory.
2308
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002309 memory_corruption_check=0/1 [X86]
2310 Some BIOSes seem to corrupt the first 64k of
2311 memory when doing things like suspend/resume.
2312 Setting this option will scan the memory
2313 looking for corruption. Enabling this will
2314 both detect corruption and prevent the kernel
2315 from using the memory being corrupted.
2316 However, its intended as a diagnostic tool; if
2317 repeatable BIOS-originated corruption always
2318 affects the same memory, you can use memmap=
2319 to prevent the kernel from using that memory.
2320
2321 memory_corruption_check_size=size [X86]
2322 By default it checks for corruption in the low
2323 64k, making this memory unavailable for normal
2324 use. Use this parameter to scan for
2325 corruption in more or less memory.
2326
2327 memory_corruption_check_period=seconds [X86]
2328 By default it checks for corruption every 60
2329 seconds. Use this parameter to check at some
2330 other rate. 0 disables periodic checking.
2331
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002332 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002333 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002334 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002335 Specifies the number of memtest passes to be
2336 performed. Each pass selects another test
2337 pattern from a given set of patterns. Memtest
2338 fills the memory with this pattern, validates
2339 memory contents and reserves bad memory
2340 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002341
Linus Torvalds1da177e2005-04-16 15:20:36 -07002342 meye.*= [HW] Set MotionEye Camera parameters
2343 See Documentation/video4linux/meye.txt.
2344
Andres Salomon8f368812007-10-12 23:04:06 +02002345 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2346 Multi-Function General Purpose Timers on AMD Geode
2347 platforms.
2348
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002349 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2350 the BIOS has incorrectly applied a workaround. TinyBIOS
2351 version 0.98 is known to be affected, 0.99 fixes the
2352 problem by letting the user disable the workaround.
2353
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354 mga= [HW,DRM]
2355
Randy Dunlap1c207f92008-11-19 15:36:16 -08002356 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2357 physical address is ignored.
2358
Michel Pollet39f45d72009-05-20 11:10:31 +01002359 mini2440= [ARM,HW,KNL]
2360 Format:[0..2][b][c][t]
2361 Default: "0tb"
2362 MINI2440 configuration specification:
2363 0 - The attached screen is the 3.5" TFT
2364 1 - The attached screen is the 7" TFT
2365 2 - The VGA Shield is attached (1024x768)
2366 Leaving out the screen size parameter will not load
2367 the TFT driver, and the framebuffer will be left
2368 unconfigured.
2369 b - Enable backlight. The TFT backlight pin will be
2370 linked to the kernel VESA blanking code and a GPIO
2371 LED. This parameter is not necessary when using the
2372 VGA shield.
2373 c - Enable the s3c camera interface.
2374 t - Reserved for enabling touchscreen support. The
2375 touchscreen support is not enabled in the mainstream
2376 kernel as of 2.6.30, a preliminary port can be found
2377 in the "bleeding edge" mini2440 support kernel at
2378 http://repo.or.cz/w/linux-2.6/mini2440.git
2379
Mel Gorman6b74ab92008-07-23 21:26:49 -07002380 mminit_loglevel=
2381 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2382 parameter allows control of the logging verbosity for
2383 the additional memory initialisation checks. A value
2384 of 0 disables mminit logging and a level of 4 will
2385 log everything. Information is printed at KERN_DEBUG
2386 so loglevel=8 may also need to be specified.
2387
Rusty Russell106a4ee2012-09-26 10:09:40 +01002388 module.sig_enforce
2389 [KNL] When CONFIG_MODULE_SIG is set, this means that
2390 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002391 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002392 is always true, so this option does nothing.
2393
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302394 module_blacklist= [KNL] Do not load a comma-separated list of
2395 modules. Useful for debugging problem modules.
2396
Linus Torvalds1da177e2005-04-16 15:20:36 -07002397 mousedev.tap_time=
2398 [MOUSE] Maximum time between finger touching and
2399 leaving touchpad surface for touch to be considered
2400 a tap and be reported as a left button click (for
2401 touchpads working in absolute mode only).
2402 Format: <msecs>
2403 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2404 reporting absolute coordinates, such as tablets
2405 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2406 reporting absolute coordinates, such as tablets
2407
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302408 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002409 is similar to kernelcore except it specifies the
2410 amount of memory used for migratable allocations.
2411 If both kernelcore and movablecore is specified,
2412 then kernelcore will be at *least* the specified
2413 value but may be more. If movablecore on its own
2414 is specified, the administrator must be careful
2415 that the amount of memory usable for all allocations
2416 is not too small.
2417
Tang Chenc5320922013-11-12 15:08:10 -08002418 movable_node [KNL,X86] Boot-time switch to enable the effects
2419 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2420
Linus Torvalds1da177e2005-04-16 15:20:36 -07002421 MTD_Partition= [MTD]
2422 Format: <name>,<region-number>,<size>,<offset>
2423
Randy Dunlapa9913042005-10-23 12:57:11 -07002424 MTD_Region= [MTD] Format:
2425 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002426
2427 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002428 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002429
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002430 multitce=off [PPC] This parameter disables the use of the pSeries
2431 firmware feature for updating multiple TCE entries
2432 at a time.
2433
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002434 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2435
2436 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2437
2438 boundary - index of last SLC block on Flex-OneNAND.
2439 The remaining blocks are configured as MLC blocks.
2440 lock - Configure if Flex-OneNAND boundary should be locked.
2441 Once locked, the boundary cannot be changed.
2442 1 indicates lock status, 0 indicates unlock status.
2443
Ben Dooks9db829f2008-07-03 11:24:29 +01002444 mtdset= [ARM]
2445 ARM/S3C2412 JIVE boot control
2446
2447 See arch/arm/mach-s3c2412/mach-jive.c
2448
Linus Torvalds1da177e2005-04-16 15:20:36 -07002449 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002450 [HW] Make the MicroTouch USB driver use raw coordinates
2451 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002452
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002453 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002454 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002455 that could hold holes aka. UC entries.
2456
2457 mtrr_gran_size=nn[KMG] [X86]
2458 Used for mtrr cleanup. It is granularity of mtrr block.
2459 Default is 1.
2460 Large value could prevent small alignment from
2461 using up MTRRs.
2462
2463 mtrr_spare_reg_nr=n [X86]
2464 Format: <integer>
2465 Range: 0,7 : spare reg number
2466 Default : 1
2467 Used for mtrr cleanup. It is spare mtrr entries number.
2468 Set to 2 or more if your graphical card needs more.
2469
Linus Torvalds1da177e2005-04-16 15:20:36 -07002470 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2471
Linus Torvalds1da177e2005-04-16 15:20:36 -07002472 netdev= [NET] Network devices parameters
2473 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2474 Note that mem_start is often overloaded to mean
2475 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002476 This usage is only documented in each driver source
2477 file if at all.
2478
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002479 nf_conntrack.acct=
2480 [NETFILTER] Enable connection tracking flow accounting
2481 0 to disable accounting
2482 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002483 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002484
Chuck Lever306a0752010-09-17 10:54:37 -04002485 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002486 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002487
2488 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002489 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490
Chuck Lever306a0752010-09-17 10:54:37 -04002491 nfsrootdebug [NFS] enable nfsroot debugging messages.
2492 See Documentation/filesystems/nfs/nfsroot.txt.
2493
Trond Myklebust5405fc42016-08-29 20:03:52 -04002494 nfs.callback_nr_threads=
2495 [NFSv4] set the total number of threads that the
2496 NFS client will assign to service NFSv4 callback
2497 requests.
2498
Trond Myklebusta72b4422006-01-03 09:55:41 +01002499 nfs.callback_tcpport=
2500 [NFS] set the TCP port on which the NFSv4 callback
2501 channel should listen.
2502
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002503 nfs.cache_getent=
2504 [NFS] sets the pathname to the program which is used
2505 to update the NFS client cache entries.
2506
2507 nfs.cache_getent_timeout=
2508 [NFS] sets the timeout after which an attempt to
2509 update a cache entry is deemed to have failed.
2510
Trond Myklebust58df0952006-01-03 09:55:57 +01002511 nfs.idmap_cache_timeout=
2512 [NFS] set the maximum lifetime for idmapper cache
2513 entries.
2514
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002515 nfs.enable_ino64=
2516 [NFS] enable 64-bit inode numbers.
2517 If zero, the NFS client will fake up a 32-bit inode
2518 number for the readdir() and stat() syscalls instead
2519 of returning the full 64-bit number.
2520 The default is to return 64-bit inode numbers.
2521
Trond Myklebust5405fc42016-08-29 20:03:52 -04002522 nfs.max_session_cb_slots=
2523 [NFSv4.1] Sets the maximum number of session
2524 slots the client will assign to the callback
2525 channel. This determines the maximum number of
2526 callbacks the client will process in parallel for
2527 a particular server.
2528
Trond Myklebustef159e92012-02-06 19:50:40 -05002529 nfs.max_session_slots=
2530 [NFSv4.1] Sets the maximum number of session slots
2531 the client will attempt to negotiate with the server.
2532 This limits the number of simultaneous RPC requests
2533 that the client can send to the NFSv4.1 server.
2534 Note that there is little point in setting this
2535 value higher than the max_tcp_slot_table_limit.
2536
Trond Myklebustb064eca22011-02-22 15:44:32 -08002537 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002538 [NFSv4] When set to the default of '1', this option
2539 ensures that both the RPC level authentication
2540 scheme and the NFS level operations agree to use
2541 numeric uids/gids if the mount is using the
2542 'sec=sys' security flavour. In effect it is
2543 disabling idmapping, which can make migration from
2544 legacy NFSv2/v3 systems to NFSv4 easier.
2545 Servers that do not support this mode of operation
2546 will be autodetected by the client, and it will fall
2547 back to using the idmapper.
2548 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002549 nfs.nfs4_unique_id=
2550 [NFS4] Specify an additional fixed unique ident-
2551 ification string that NFSv4 clients can insert into
2552 their nfs_client_id4 string. This is typically a
2553 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002554
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002555 nfs.send_implementation_id =
2556 [NFSv4.1] Send client implementation identification
2557 information in exchange_id requests.
2558 If zero, no implementation identification information
2559 will be sent.
2560 The default is to send the implementation identification
2561 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002562
2563 nfs.recover_lost_locks =
2564 [NFSv4] Attempt to recover locks that were lost due
2565 to a lease timeout on the server. Please note that
2566 doing this risks data corruption, since there are
2567 no guarantees that the file will remain unchanged
2568 after the locks are lost.
2569 If you want to enable the kernel legacy behaviour of
2570 attempting to recover these locks, then set this
2571 parameter to '1'.
2572 The default parameter value of '0' causes the kernel
2573 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002574
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002575 nfs4.layoutstats_timer =
2576 [NFSv4.2] Change the rate at which the kernel sends
2577 layoutstats to the pNFS metadata server.
2578
2579 Setting this to value to 0 causes the kernel to use
2580 whatever value is the default set by the layout
2581 driver. A non-zero value sets the minimum interval
2582 in seconds between layoutstats transmissions.
2583
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002584 nfsd.nfs4_disable_idmapping=
2585 [NFSv4] When set to the default of '1', the NFSv4
2586 server will return only numeric uids and gids to
2587 clients using auth_sys, and will accept numeric uids
2588 and gids from such clients. This is intended to ease
2589 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002590
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002591 objlayoutdriver.osd_login_prog=
2592 [NFS] [OBJLAYOUT] sets the pathname to the program which
2593 is used to automatically discover and login into new
2594 osd-targets. Please see:
2595 Documentation/filesystems/pnfs.txt for more explanations
2596
Paul Mundt1e1030d2009-09-01 17:38:32 +09002597 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002598 when a NMI is triggered.
2599 Format: [state][,regs][,debounce][,die]
2600
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302601 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002602 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002603 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002604 0 - turn hardlockup detector in nmi_watchdog off
2605 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002606 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002607 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002608 default). To disable both hard and soft lockup detectors,
2609 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002610 This is useful when you use a panic=... timeout and
2611 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612
Anton Vorontsovbff38772009-07-08 11:10:56 -07002613 netpoll.carrier_timeout=
2614 [NET] Specifies amount of time (in seconds) that
2615 netpoll should wait for a carrier. By default netpoll
2616 waits 4 seconds.
2617
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002618 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002619 emulation library even if a 387 maths coprocessor
2620 is present.
2621
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002622 no_console_suspend
2623 [HW] Never suspend the console
2624 Disable suspending of consoles during suspend and
2625 hibernate operations. Once disabled, debugging
2626 messages can reach various consoles while the rest
2627 of the system is being put to sleep (ie, while
2628 debugging driver suspend/resume hooks). This may
2629 not work reliably with all consoles, but is known
2630 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002631 To facilitate more flexible debugging, we also add
2632 console_suspend, a printk module parameter to control
2633 it. Users could use console_suspend (usually
2634 /sys/module/printk/parameters/console_suspend) to
2635 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002636
Christoph Lameterc1aee212007-05-31 00:40:47 -07002637 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2638 caches in the slab allocator. Saves per-node memory,
2639 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002640
Randy Dunlapa9913042005-10-23 12:57:11 -07002641 noalign [KNL,ARM]
2642
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643 noapic [SMP,APIC] Tells the kernel to not make use of any
2644 IOAPICs that may be present in the system.
2645
Mike Galbraith5091faa2010-11-30 14:18:03 +01002646 noautogroup Disable scheduler automatic task group creation.
2647
Linus Torvalds1da177e2005-04-16 15:20:36 -07002648 nobats [PPC] Do not use BATs for mapping kernel lowmem
2649 on "Classic" PPC cores.
2650
2651 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002652
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002653 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2654
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002655 nodelayacct [KNL] Disable per-task delay accounting
2656
Paul Mundt6902aa82008-09-21 17:14:42 +09002657 nodsp [SH] Disable hardware DSP at boot time.
2658
Dave Youngb2e0a542014-08-14 17:15:26 +08002659 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002660
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661 noexec [IA-64]
2662
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302663 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002664 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002665 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002666 noexec=off: disable non-executable mappings
2667
H. Peter Anvin52b61792012-09-21 12:43:13 -07002668 nosmap [X86]
2669 Disable SMAP (Supervisor Mode Access Prevention)
2670 even if it is supported by processor.
2671
Fenghua Yude5397a2011-05-11 16:51:05 -07002672 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002673 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002674 even if it is supported by processor.
2675
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002676 noexec32 [X86-64]
2677 This affects only 32-bit executables.
2678 noexec32=on: enable non-executable mappings (default)
2679 read doesn't imply executable mappings
2680 noexec32=off: disable non-executable mappings
2681 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002683 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002684
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002685 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002686 register save and restore. The kernel will only save
2687 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002688
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002689 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2690
Sascha Silbe52c48c52016-04-05 12:53:38 +02002691 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2692 Equivalent to smt=1.
2693
Suresh Siddha0c752a92009-05-22 12:17:45 -07002694 noxsave [BUGS=X86] Disables x86 extended register state save
2695 and restore using xsave. The kernel will fallback to
2696 enabling legacy floating-point and sse state.
2697
Fenghua Yub6f42a42014-05-29 11:12:31 -07002698 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2699 register states. The kernel will fall back to use
2700 xsave to save the states. By using this parameter,
2701 performance of saving the states is degraded because
2702 xsave doesn't support modified optimization while
2703 xsaveopt supports it on xsaveopt enabled systems.
2704
2705 noxsaves [X86] Disables xsaves and xrstors used in saving and
2706 restoring x86 extended register state in compacted
2707 form of xsave area. The kernel will fall back to use
2708 xsaveopt and xrstor to save and restore the states
2709 in standard form of xsave area. By using this
2710 parameter, xsave area per process might occupy more
2711 memory on xsaves enabled systems.
2712
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002713 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2714 wfi(ARM) instruction doesn't work correctly and not to
2715 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002716
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002717 no_file_caps Tells the kernel not to honor file capabilities. The
2718 only way then for a file to be executed with privilege
2719 is to be setuid root or executed by root.
2720
Linus Torvalds1da177e2005-04-16 15:20:36 -07002721 nohalt [IA-64] Tells the kernel not to use the power saving
2722 function PAL_HALT_LIGHT when idle. This increases
2723 power-consumption. On the positive side, it reduces
2724 interrupt wake-up latency, which may improve performance
2725 in certain environments such as networked servers or
2726 real-time systems.
2727
Kees Cooka6e15a32014-06-13 13:30:35 -07002728 nohibernate [HIBERNATION] Disable hibernation and resume.
2729
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002730 nohz= [KNL] Boottime enable/disable dynamic ticks
2731 Valid arguments: on, off
2732 Default: on
2733
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002734 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002735 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002736 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002737 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002738 whenever possible. The boot CPU will be forced outside
2739 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002740 The CPUs in this range must also be included in the
2741 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002742
Paul Mundteeee7852009-04-02 12:31:16 +09002743 noiotrap [SH] Disables trapped I/O port accesses.
2744
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002745 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002746 disable unhandled interrupt sources.
2747
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302748 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002749 broken timer IRQ sources.
2750
Linus Torvalds1da177e2005-04-16 15:20:36 -07002751 noisapnp [ISAPNP] Disables ISA PnP code.
2752
2753 noinitrd [RAM] Tells the kernel not to load any configured
2754 initial RAM disk.
2755
Weidong Han03ea8152009-04-17 16:42:15 +08002756 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2757 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002758 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002759
Linus Torvalds1da177e2005-04-16 15:20:36 -07002760 nointroute [IA-64]
2761
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002762 noinvpcid [X86] Disable the INVPCID cpu feature.
2763
Randy Dunlap16290242011-08-13 12:34:52 -07002764 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002765
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002766 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2767
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002768 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2769 fault handling.
2770
Glauber Costad910f5c2011-07-11 15:28:19 -04002771 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2772 steal time is computed, but won't influence scheduler
2773 behaviour
2774
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002775 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002776
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002777 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002778
Linus Torvalds1da177e2005-04-16 15:20:36 -07002779 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002780 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002781
Horms312f1f02006-02-22 09:57:55 +09002782 nomca [IA-64] Disable machine check abort handling
2783
Masanari Iida13696e02015-05-16 02:16:43 +09002784 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002785
Andres Salomon83d73842007-10-12 23:04:06 +02002786 nomfgpt [X86-32] Disable Multi-Function General Purpose
2787 Timer usage (for AMD Geode machines).
2788
Don Zickusbda62632011-10-13 15:14:27 -04002789 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2790 shutdown the other cpus. Instead use the REBOOT_VECTOR
2791 irq.
2792
Dave Young02608be2012-02-01 10:33:14 +08002793 nomodule Disable module load
2794
Jiri Kosina016ddd92010-01-18 17:05:40 +01002795 nopat [X86] Disable PAT (page attribute table extension of
2796 pagetables) support.
2797
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002798 norandmaps Don't use address space randomization. Equivalent to
2799 echo 0 > /proc/sys/kernel/randomize_va_space
2800
Jiri Kosinabbff2162010-08-11 18:34:09 +02002801 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002802
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002803 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002804 with UP alternatives
2805
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002806 nordrand [X86] Disable kernel use of the RDRAND and
2807 RDSEED instructions even if they are supported
2808 by the processor. RDRAND and RDSEED are still
2809 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002810
Randy Dunlapa9913042005-10-23 12:57:11 -07002811 noresume [SWSUSP] Disables resume and restores original swap
2812 space.
2813
Linus Torvalds1da177e2005-04-16 15:20:36 -07002814 no-scroll [VGA] Disables scrollback.
2815 This is required for the Braillex ib80-piezo Braille
2816 reader made by F.H. Papenmeier (Germany).
2817
2818 nosbagart [IA-64]
2819
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002820 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002821
Len Brown61ec7562007-08-16 03:34:22 -04002822 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2823 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824
Dave Jones97842212007-07-15 23:41:05 -07002825 nosoftlockup [KNL] Disable the soft-lockup detector.
2826
Linus Torvalds1da177e2005-04-16 15:20:36 -07002827 nosync [HW,M68K] Disables sync negotiation for all devices.
2828
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002829 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002830
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002831 nowatchdog [KNL] Disable both lockup detectors, i.e.
2832 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002833
Linus Torvalds1da177e2005-04-16 15:20:36 -07002834 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002835
Weidong Han2b2fd872009-04-17 16:42:12 +08002836 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2837
Fenghua Yuf78cff42012-11-13 11:32:38 -08002838 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2839 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2840 Some features depend on CPU0. Known dependencies are:
2841 1. Resume from suspend/hibernate depends on CPU0.
2842 Suspend/hibernate will fail if CPU0 is offline and you
2843 need to online CPU0 before suspend/hibernate.
2844 2. PIC interrupts also depend on CPU0. CPU0 can't be
2845 removed if a PIC interrupt is detected.
2846 It's said poweroff/reboot may depend on CPU0 on some
2847 machines although I haven't seen such issues so far
2848 after CPU0 is offline on a few tested machines.
2849 If the dependencies are under your control, you can
2850 turn on cpu0_hotplug.
2851
Randy Dunlap16290242011-08-13 12:34:52 -07002852 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002853 purges which is reported from either PAL_VM_SUMMARY or
2854 SAL PALO.
2855
Yinghai Lu2b633e32010-02-10 01:20:37 -08002856 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2857 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002858 support 'n' processors. It could be larger than the
2859 number of already plugged CPU during bootup, later in
2860 runtime you can physically add extra cpu until it reaches
2861 n. So during boot up some boot time memory for per-cpu
2862 variables need be pre-allocated for later physical cpu
2863 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002864
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002865 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2866
Mel Gorman1a687c22012-11-22 11:16:36 +00002867 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2868 Allowed values are enable and disable
2869
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002870 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2871 one of ['zone', 'node', 'default'] can be specified
2872 This can be set from sysctl after boot.
2873 See Documentation/sysctl/vm.txt for details.
2874
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002875 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2876 See Documentation/debugging-via-ohci1394.txt for more
2877 info.
2878
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002879 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2880 Rather than timing out after 20 ms if an EC
2881 command is not properly ACKed, override the length
2882 of the timeout. We have interrupts disabled while
2883 waiting for the ACK, so if this is set too high
2884 interrupts *may* be lost!
2885
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002886 omap_mux= [OMAP] Override bootloader pin multiplexing.
2887 Format: <mux_mode0.mode_name=value>...
2888 For example, to override I2C bus2:
2889 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2890
Linus Torvalds1da177e2005-04-16 15:20:36 -07002891 oprofile.timer= [HW]
2892 Use timer interrupt instead of performance counters
2893
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002894 oprofile.cpu_type= Force an oprofile cpu type
2895 This might be useful if you have an older oprofile
2896 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002897 Format: { arch_perfmon }
2898 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002899 perfmon on Intel CPUs instead of the
2900 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002901 timer: [X86] Force use of architectural NMI
2902 timer mode (see also oprofile.timer
2903 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002904
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002905 oops=panic Always panic on oopses. Default is to just kill the
2906 process, but there is a small probability of
2907 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002908 This will also cause panics on machine check exceptions.
2909 Useful together with panic=30 to trigger a reboot.
2910
Randy Dunlapbcfde332010-06-07 17:10:38 -07002911 OSS [HW,OSS]
2912 See Documentation/sound/oss/oss-parameters.txt
2913
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002914 page_owner= [KNL] Boot-time page_owner enabling option.
2915 Storage of the information about who allocated
2916 each page is disabled in default. With this switch,
2917 we can turn it on.
2918 on: enable the feature
2919
Laura Abbott8823b1d2016-03-15 14:56:27 -07002920 page_poison= [KNL] Boot-time parameter changing the state of
2921 poisoning on the buddy allocator.
2922 off: turn off poisoning
2923 on: turn on poisoning
2924
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002925 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002926 timeout > 0: seconds before rebooting
2927 timeout = 0: wait forever
2928 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002929 Format: <timeout>
2930
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002931 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2932 on a WARN().
2933
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002934 crash_kexec_post_notifiers
2935 Run kdump after running panic-notifiers and dumping
2936 kmsg. This only for the users who doubt kdump always
2937 succeeds in any situation.
2938 Note that this also increases risks of kdump failure,
2939 because some panic notifiers can make the crashed
2940 kernel more unstable.
2941
Linus Torvalds1da177e2005-04-16 15:20:36 -07002942 parkbd.port= [HW] Parallel port number the keyboard adapter is
2943 connected to, default is 0.
2944 Format: <parport#>
2945 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2946 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002947 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948
Randy Dunlapa9913042005-10-23 12:57:11 -07002949 parport= [HW,PPT] Specify parallel ports. 0 disables.
2950 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2951 Use 'auto' to force the driver to use any
2952 IRQ/DMA settings detected (the default is to
2953 ignore detected IRQ/DMA settings because of
2954 possible conflicts). You can specify the base
2955 address, IRQ, and DMA settings; IRQ and DMA
2956 should be numbers, or 'auto' (for using detected
2957 settings on that particular port), or 'nofifo'
2958 (to avoid using a FIFO even if it is detected).
2959 Parallel ports are assigned in the order they
2960 are specified on the command line, starting
2961 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962
Randy Dunlapa9913042005-10-23 12:57:11 -07002963 parport_init_mode= [HW,PPT]
2964 Configure VIA parallel port to operate in
2965 a specific mode. This is necessary on Pegasos
2966 computer where firmware has no options for setting
2967 up parallel port mode and sets it to spp.
2968 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002969 Format: [spp|ps2|epp|ecp|ecpepp]
2970
Andrew Mortondd287792006-03-23 03:00:57 -08002971 pause_on_oops=
2972 Halt all CPUs after the first oops has been printed for
2973 the specified number of seconds. This is to be used if
2974 your oopses keep scrolling off the screen.
2975
Linus Torvalds1da177e2005-04-16 15:20:36 -07002976 pcbit= [HW,ISDN]
2977
2978 pcd. [PARIDE]
2979 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002980 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002981
Randy Dunlapa9913042005-10-23 12:57:11 -07002982 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002983 earlydump [X86] dump PCI config space before the kernel
2984 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002985 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002986 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002987 the hardware directly. Use this if your machine
2988 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002989 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002990 hardware access methods are allowed. Use this
2991 if you experience crashes upon bootup and you
2992 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002993 conf1 [X86] Force use of PCI Configuration Access
2994 Mechanism 1 (config address in IO port 0xCF8,
2995 data in IO port 0xCFC, both 32-bit).
2996 conf2 [X86] Force use of PCI Configuration Access
2997 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2998 the function, IO port 0xCFA, also 8-bit, sets
2999 bus number. The config space is then accessed
3000 through ports 0xC000-0xCFFF).
3001 See http://wiki.osdev.org/PCI for more info
3002 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07003003 noaer [PCIE] If the PCIEAER kernel config parameter is
3004 enabled, this kernel boot option can be used to
3005 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04003006 nodomains [PCI] Disable support for multiple PCI
3007 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303008 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08003009 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02003010 check_enable_amd_mmconf [X86] check for and enable
3011 properly configured MMIO access to PCI
3012 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07003013 nomsi [MSI] If the PCI_MSI kernel config parameter is
3014 enabled, this kernel boot option can be used to
3015 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02003016 noioapicquirk [APIC] Disable all boot interrupt quirks.
3017 Safety option to keep boot IRQs enabled. This
3018 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02003019 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3020 primary IO-APIC for bridges that cannot disable
3021 boot IRQs. This fixes a source of spurious IRQs
3022 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02003023 noioapicreroute [APIC] Disable workaround that uses the
3024 boot IRQ equivalent of an IRQ that connects to
3025 a chipset where boot IRQs cannot be disabled.
3026 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003027 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07003028 routing table. These calls are known to be buggy
3029 on several machines and they hang the machine
3030 when used, but on other computers it's the only
3031 way to get the interrupt routing table. Try
3032 this option if the kernel is unable to allocate
3033 IRQs or discover secondary PCI buses on your
3034 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02003035 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07003036 Use with caution as certain devices share
3037 address decoders between ROMs and other
3038 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02003039 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07003040 expansion ROMs that do not already have
3041 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07003042 nobar [X86] Do not assign address space to the
3043 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02003044 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07003045 assigned automatically to PCI devices. You can
3046 make the kernel exclude IRQs of your ISA cards
3047 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02003048 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07003049 of the PIRQ table (normally generated
3050 by the BIOS) if it is outside the
3051 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02003052 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07003053 useful if the kernel is unable to find your
3054 secondary buses and you want to tell it
3055 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02003056 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07003057 numbers ourselves, overriding
3058 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02003059 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07003060 in the BIOS $PIR table. This is needed on
3061 some systems with broken BIOSes, notably
3062 some HP Pavilion N5400 and Omnibook XE3
3063 notebooks. This will have no effect if ACPI
3064 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02003065 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07003066 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07003067 use_crs [X86] Use PCI host bridge window information
3068 from ACPI. On BIOSes from 2008 or later, this
3069 is enabled by default. If you need to use this,
3070 please report a bug.
3071 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3072 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07003073 routeirq Do IRQ routing for all PCI devices.
3074 This is normally done in pci_enable_device(),
3075 so this option is a temporary workaround
3076 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07003077 skip_isa_align [X86] do not align io start addr, so can
3078 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02003079 noearly [X86] Don't do any early type 1 scanning.
3080 This might help on some broken boards which
3081 machine check when some devices' config space
3082 is read. But various workarounds are disabled
3083 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003084 bfsort Sort PCI devices into breadth-first order.
3085 This sorting is done to get a device
3086 order compatible with older (<= 2.4) kernels.
3087 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08003088 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3089 tuning and use the BIOS-configured MPS defaults.
3090 pcie_bus_safe Set every device's MPS to the largest value
3091 supported by all devices below the root complex.
3092 pcie_bus_perf Set device MPS to the largest allowable MPS
3093 based on its parent bus. Also set MRRS (Max
3094 Read Request Size) to the largest supported
3095 value (no larger than the MPS that the device
3096 or bus can support) for best performance.
3097 pcie_bus_peer2peer Set every device's MPS to 128B, which
3098 every device is guaranteed to support. This
3099 configuration allows peer-to-peer DMA between
3100 any pair of devices, possibly at the cost of
3101 reduced performance. This also guarantees
3102 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08003103 cbiosize=nn[KMG] The fixed amount of bus space which is
3104 reserved for the CardBus bridge's IO window.
3105 The default value is 256 bytes.
3106 cbmemsize=nn[KMG] The fixed amount of bus space which is
3107 reserved for the CardBus bridge's memory
3108 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003109 resource_alignment=
3110 Format:
3111 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00003112 [<order of align>@]pci:<vendor>:<device>\
3113 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09003114 Specifies alignment and device to reassign
3115 aligned memory resources.
3116 If <order of align> is not specified,
3117 PAGE_SIZE is used as alignment.
3118 PCI-PCI bridge can be specified, if resource
3119 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02003120 To specify the alignment for several
3121 instances of a device, the PCI vendor,
3122 device, subvendor, and subdevice may be
3123 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06003124 ecrc= Enable/disable PCIe ECRC (transaction layer
3125 end-to-end CRC checking).
3126 bios: Use BIOS/firmware settings. This is the
3127 the default.
3128 off: Turn ECRC off
3129 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08003130 hpiosize=nn[KMG] The fixed amount of bus space which is
3131 reserved for hotplug bridge's IO window.
3132 Default size is 256 bytes.
3133 hpmemsize=nn[KMG] The fixed amount of bus space which is
3134 reserved for hotplug bridge's memory window.
3135 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06003136 hpbussize=nn The minimum amount of additional bus numbers
3137 reserved for buses below a hotplug bridge.
3138 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08003139 realloc= Enable/disable reallocating PCI bridge resources
3140 if allocations done by BIOS are too small to
3141 accommodate resources required by all child
3142 devices.
3143 off: Turn realloc off
3144 on: Turn realloc on
3145 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01003146 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06003147 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3148 only look for one device below a PCIe downstream
3149 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05003150
Chuck Ebberte5665a42008-09-24 20:40:34 -04003151 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3152 Management.
3153 off Disable ASPM.
3154 force Enable ASPM even on devices that claim not to support it.
3155 WARNING: Forcing ASPM on may cause system lockups.
3156
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05003157 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3158 nomsi Do not use MSI for PCI Express Native Hotplug (this
3159 makes all PCIe ports use INTx for hotplug services).
3160
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003161 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003162 auto Ask the BIOS whether or not to use native PCIe services
3163 associated with PCIe ports (PME, hot-plug, AER). Use
3164 them only if that is allowed by the BIOS.
3165 native Use native PCIe services associated with PCIe ports
3166 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02003167 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3168 ports driver.
3169
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03003170 pcie_port_pm= [PCIE] PCIe port power management handling:
3171 off Disable power management of all PCIe ports
3172 force Forcibly enable power management of all PCIe ports
3173
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003174 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01003175 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02003176 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01003177
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178 pcmv= [HW,PCMCIA] BadgePAD 4
3179
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303180 pd_ignore_unused
3181 [PM]
3182 Keep all power-domains already enabled by bootloader on,
3183 even if no driver has claimed them. This is useful
3184 for debug and development, but should not be
3185 needed on a platform with proper driver support.
3186
Linus Torvalds1da177e2005-04-16 15:20:36 -07003187 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003188 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003189
3190 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3191 boot time.
3192 Format: { 0 | 1 }
3193 See arch/parisc/kernel/pdc_chassis.c
3194
Tejun Heof58dc012009-08-14 15:00:50 +09003195 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003196 Currently supported values are "embed" and "page".
3197 Archs may support subset or none of the selections.
3198 See comments in mm/percpu.c for details on each
3199 allocator. This parameter is primarily for debugging
3200 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003201
Linus Torvalds1da177e2005-04-16 15:20:36 -07003202 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003203 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003204
3205 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003206 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003207
3208 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003209 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003210
3211 plip= [PPT,NET] Parallel port network link
3212 Format: { parport<nr> | timid | 0 }
3213 See also Documentation/parport.txt.
3214
Randy Dunlap16290242011-08-13 12:34:52 -07003215 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003216 Override pmtimer IOPort with a hex value.
3217 e.g. pmtmr=0x508
3218
Bjorn Helgaas96242112011-08-11 12:14:05 -06003219 pnp.debug=1 [PNP]
3220 Enable PNP debug messages (depends on the
3221 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3222 via /sys/module/pnp/parameters/debug. We always show
3223 current resource usage; turning this on also shows
3224 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003225
Linus Torvalds1da177e2005-04-16 15:20:36 -07003226 pnpacpi= [ACPI]
3227 { off }
3228
3229 pnpbios= [ISAPNP]
3230 { on | off | curr | res | no-curr | no-res }
3231
3232 pnp_reserve_irq=
3233 [ISAPNP] Exclude IRQs for the autoconfiguration
3234
3235 pnp_reserve_dma=
3236 [ISAPNP] Exclude DMAs for the autoconfiguration
3237
3238 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003239 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003240
3241 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003242 [ISAPNP] Exclude memory regions for the
3243 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003244 Ranges are in pairs (memory base and size).
3245
Randy Dunlap4af94f32009-04-17 18:30:28 -07003246 ports= [IP_VS_FTP] IPVS ftp helper module
3247 Default is 21.
3248 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3249 may be specified.
3250 Format: <port>,<port>....
3251
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003252 ppc_strict_facility_enable
3253 [PPC] This option catches any kernel floating point,
3254 Altivec, VSX and SPE outside of regions specifically
3255 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3256 There is some performance impact when enabling this.
3257
Ingo Molnar45807a12007-07-15 23:40:10 -07003258 print-fatal-signals=
3259 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003260
3261 If enabled, warn about various signal handling
3262 related application anomalies: too many signals,
3263 too many POSIX.1 timers, fatal signals causing a
3264 coredump - etc.
3265
3266 If you hit the warning due to signal overflow,
3267 you might want to try "ulimit -i unlimited".
3268
Ingo Molnar45807a12007-07-15 23:40:10 -07003269 default: off.
3270
Matthew Garrettc22ab332012-03-05 14:59:10 -08003271 printk.always_kmsg_dump=
3272 Trigger kmsg_dump for cases other than kernel oops or
3273 panics
3274 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3275 default: disabled
3276
Borislav Petkov750afe72016-08-02 14:04:07 -07003277 printk.devkmsg={on,off,ratelimit}
3278 Control writing to /dev/kmsg.
3279 on - unlimited logging to /dev/kmsg from userspace
3280 off - logging to /dev/kmsg disabled
3281 ratelimit - ratelimit the logging
3282 Default: ratelimit
3283
Randy Dunlape84845c2007-07-15 23:40:25 -07003284 printk.time= Show timing data prefixed to each printk message line
3285 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3286
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003287 processor.max_cstate= [HW,ACPI]
3288 Limit processor to maximum C-state
3289 max_cstate=9 overrides any DMI blacklist limit.
3290
3291 processor.nocst [HW,ACPI]
3292 Ignore the _CST method to determine C-states,
3293 instead using the legacy FADT method
3294
Linus Torvalds1da177e2005-04-16 15:20:36 -07003295 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003296 Format: [schedule,]<number>
3297 Param: "schedule" - profile schedule points.
3298 Param: <number> - step/bucket size as a power of 2 for
3299 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003300 Param: "sleep" - profile D-state sleeping (millisecs).
3301 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003302 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003303
Linus Torvalds1da177e2005-04-16 15:20:36 -07003304 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3305 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003306 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003307
Randy Dunlapa9913042005-10-23 12:57:11 -07003308 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3309 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003310 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3311 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003312 psmouse.resetafter= [HW,MOUSE]
3313 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003314 (0 = never).
3315 psmouse.resolution=
3316 [HW,MOUSE] Set desired mouse resolution, in dpi.
3317 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003318 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319 0 = disabled, 1 = enabled (default).
3320
Matthew Garrettdee28e72011-07-21 16:57:55 -04003321 pstore.backend= Specify the name of the pstore backend to use
3322
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003324 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003325
Kay Sieversdc8c8582007-08-15 12:25:38 +02003326 pty.legacy_count=
3327 [KNL] Number of legacy pty's. Overwrites compiled-in
3328 default number.
3329
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003330 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003331
Linus Torvalds1da177e2005-04-16 15:20:36 -07003332 r128= [HW,DRM]
3333
3334 raid= [HW,RAID]
3335 See Documentation/md.txt.
3336
Linus Torvalds1da177e2005-04-16 15:20:36 -07003337 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003338 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003340 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003341 The argument is a cpu list, as described above.
3342
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003343 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3344 the specified list of CPUs to be no-callback CPUs.
3345 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003346 be offloaded to "rcuox/N" kthreads created for
3347 that purpose, where "x" is "b" for RCU-bh, "p"
3348 for RCU-preempt, and "s" for RCU-sched, and "N"
3349 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003350 offloaded CPUs, which can be useful for HPC and
3351 real-time workloads. It can also improve energy
3352 efficiency for asymmetric multiprocessors.
3353
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003354 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003355 Rather than requiring that offloaded CPUs
3356 (specified by rcu_nocbs= above) explicitly
3357 awaken the corresponding "rcuoN" kthreads,
3358 make these kthreads poll for callbacks.
3359 This improves the real-time response for the
3360 offloaded CPUs by relieving them of the need to
3361 wake up the corresponding kthread, but degrades
3362 energy efficiency by requiring that the kthreads
3363 periodically wake up to do the polling.
3364
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003365 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003366 Set maximum number of finished RCU callbacks to
3367 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003368
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003369 rcutree.dump_tree= [KNL]
3370 Dump the structure of the rcu_node combining tree
3371 out at early boot. This is used for diagnostic
3372 purposes, to verify correct tree setup.
3373
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003374 rcutree.gp_cleanup_delay= [KNL]
3375 Set the number of jiffies to delay each step of
3376 RCU grace-period cleanup. This only has effect
3377 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3378
Paul E. McKenney37745d22015-01-22 18:24:08 -08003379 rcutree.gp_init_delay= [KNL]
3380 Set the number of jiffies to delay each step of
3381 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003382 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3383 is set.
3384
3385 rcutree.gp_preinit_delay= [KNL]
3386 Set the number of jiffies to delay each step of
3387 RCU grace-period pre-initialization, that is,
3388 the propagation of recent CPU-hotplug changes up
3389 the rcu_node combining tree. This only has effect
3390 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003391
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003392 rcutree.rcu_fanout_exact= [KNL]
3393 Disable autobalancing of the rcu_node combining
3394 tree. This is used by rcutorture, and might
3395 possibly be useful for architectures having high
3396 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003397
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003398 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003399 Change the number of CPUs assigned to each
3400 leaf rcu_node structure. Useful for very
3401 large systems, which will choose the value 64,
3402 and for NUMA systems with large remote-access
3403 latencies, which will choose a value aligned
3404 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003405
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003406 rcutree.jiffies_till_sched_qs= [KNL]
3407 Set required age in jiffies for a
3408 given grace period before RCU starts
3409 soliciting quiescent-state help from
3410 rcu_note_context_switch().
3411
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003412 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003413 Set delay from grace-period initialization to
3414 first attempt to force quiescent states.
3415 Units are jiffies, minimum value is zero,
3416 and maximum value is HZ.
3417
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003418 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003419 Set delay between subsequent attempts to force
3420 quiescent states. Units are jiffies, minimum
3421 value is one, and maximum value is HZ.
3422
Clark Williams21871d72014-09-12 21:21:09 -05003423 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003424 Set the SCHED_FIFO priority of the RCU per-CPU
3425 kthreads (rcuc/N). This value is also used for
3426 the priority of the RCU boost threads (rcub/N)
3427 and for the RCU grace-period kthreads (rcu_bh,
3428 rcu_preempt, and rcu_sched). If RCU_BOOST is
3429 set, valid values are 1-99 and the default is 1
3430 (the least-favored priority). Otherwise, when
3431 RCU_BOOST is not set, valid values are 0-99 and
3432 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003433
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003434 rcutree.rcu_nocb_leader_stride= [KNL]
3435 Set the number of NOCB kthread groups, which
3436 defaults to the square root of the number of
3437 CPUs. Larger numbers reduces the wakeup overhead
3438 on the per-CPU grace-period kthreads, but increases
3439 that same overhead on each group's leader.
3440
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003441 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003442 Set threshold of queued RCU callbacks beyond which
3443 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003444
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003445 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003446 Set threshold of queued RCU callbacks below which
3447 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003448
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003449 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003450 Set wakeup interval for idle CPUs that have
3451 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003452
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003453 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003454 Set wakeup interval for idle CPUs that have
3455 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3456 Lazy RCU callbacks are those which RCU can
3457 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003458
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003459 rcuperf.gp_exp= [KNL]
3460 Measure performance of expedited synchronous
3461 grace-period primitives.
3462
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003463 rcuperf.holdoff= [KNL]
3464 Set test-start holdoff period. The purpose of
3465 this parameter is to delay the start of the
3466 test until boot completes in order to avoid
3467 interference.
3468
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003469 rcuperf.nreaders= [KNL]
3470 Set number of RCU readers. The value -1 selects
3471 N, where N is the number of CPUs. A value
3472 "n" less than -1 selects N-n+1, where N is again
3473 the number of CPUs. For example, -2 selects N
3474 (the number of CPUs), -3 selects N+1, and so on.
3475 A value of "n" less than or equal to -N selects
3476 a single reader.
3477
3478 rcuperf.nwriters= [KNL]
3479 Set number of RCU writers. The values operate
3480 the same as for rcuperf.nreaders.
3481 N, where N is the number of CPUs
3482
3483 rcuperf.perf_runnable= [BOOT]
3484 Start rcuperf running at boot time.
3485
3486 rcuperf.shutdown= [KNL]
3487 Shut the system down after performance tests
3488 complete. This is useful for hands-off automated
3489 testing.
3490
3491 rcuperf.perf_type= [KNL]
3492 Specify the RCU implementation to test.
3493
3494 rcuperf.verbose= [KNL]
3495 Enable additional printk() statements.
3496
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003497 rcutorture.cbflood_inter_holdoff= [KNL]
3498 Set holdoff time (jiffies) between successive
3499 callback-flood tests.
3500
3501 rcutorture.cbflood_intra_holdoff= [KNL]
3502 Set holdoff time (jiffies) between successive
3503 bursts of callbacks within a given callback-flood
3504 test.
3505
3506 rcutorture.cbflood_n_burst= [KNL]
3507 Set the number of bursts making up a given
3508 callback-flood test. Set this to zero to
3509 disable callback-flood testing.
3510
3511 rcutorture.cbflood_n_per_burst= [KNL]
3512 Set the number of callbacks to be registered
3513 in a given burst of a callback-flood test.
3514
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003515 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003516 Set duration of force_quiescent_state bursts
3517 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003518
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003519 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003520 Set holdoff time within force_quiescent_state bursts
3521 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003522
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003523 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003524 Set wait time between force_quiescent_state bursts
3525 in seconds.
3526
3527 rcutorture.gp_cond= [KNL]
3528 Use conditional/asynchronous update-side
3529 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003530
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003531 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003532 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003533
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003534 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003535 Use normal (non-expedited) asynchronous
3536 update-side primitives, if available.
3537
3538 rcutorture.gp_sync= [KNL]
3539 Use normal (non-expedited) synchronous
3540 update-side primitives, if available. If all
3541 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3542 rcutorture.gp_normal=, and rcutorture.gp_sync=
3543 are zero, rcutorture acts as if is interpreted
3544 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003545
3546 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003547 Set callbacks/threads for rcu_barrier() testing.
3548
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003549 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003550 Set number of concurrent RCU writers. These just
3551 stress RCU, they don't participate in the actual
3552 test, hence the "fake".
3553
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003554 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003555 Set number of RCU readers. The value -1 selects
3556 N-1, where N is the number of CPUs. A value
3557 "n" less than -1 selects N-n-2, where N is again
3558 the number of CPUs. For example, -2 selects N
3559 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003560
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003561 rcutorture.object_debug= [KNL]
3562 Enable debug-object double-call_rcu() testing.
3563
3564 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003565 Set time (s) after boot for CPU-hotplug testing.
3566
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003567 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003568 Set time (s) between CPU-hotplug operations, or
3569 zero to disable CPU-hotplug testing.
3570
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003571 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003572 Set task-shuffle interval (s). Shuffling tasks
3573 allows some CPUs to go into dyntick-idle mode
3574 during the rcutorture test.
3575
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003576 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003577 Set time (s) after boot system shutdown. This
3578 is useful for hands-off automated testing.
3579
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003580 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003581 Duration of CPU stall (s) to test RCU CPU stall
3582 warnings, zero to disable.
3583
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003584 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003585 Time to wait (s) after boot before inducing stall.
3586
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003587 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003588 Time (s) between statistics printk()s.
3589
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003590 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003591 Time (s) to stutter testing, for example, specifying
3592 five seconds causes the test to run for five seconds,
3593 wait for five seconds, and so on. This tests RCU's
3594 ability to transition abruptly to and from idle.
3595
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003596 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003597 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3598 "Maybe" means test if the RCU implementation
3599 under test support RCU priority boosting.
3600
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003601 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003602 Duration (s) of each individual boost test.
3603
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003604 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003605 Interval (s) between each boost test.
3606
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003607 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003608 Test RCU's dyntick-idle handling. See also the
3609 rcutorture.shuffle_interval parameter.
3610
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003611 rcutorture.torture_runnable= [BOOT]
3612 Start rcutorture running at boot time.
3613
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003614 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003615 Specify the RCU implementation to test.
3616
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003617 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003618 Enable additional printk() statements.
3619
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003620 rcupdate.rcu_cpu_stall_suppress= [KNL]
3621 Suppress RCU CPU stall warning messages.
3622
3623 rcupdate.rcu_cpu_stall_timeout= [KNL]
3624 Set timeout for RCU CPU stall warning messages.
3625
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003626 rcupdate.rcu_expedited= [KNL]
3627 Use expedited grace-period primitives, for
3628 example, synchronize_rcu_expedited() instead
3629 of synchronize_rcu(). This reduces latency,
3630 but can increase CPU utilization, degrade
3631 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003632 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003633
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003634 rcupdate.rcu_normal= [KNL]
3635 Use only normal grace-period primitives,
3636 for example, synchronize_rcu() instead of
3637 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003638 real-time latency, CPU utilization, and
3639 energy efficiency, but can expose users to
3640 increased grace-period latency. This parameter
3641 overrides rcupdate.rcu_expedited. No effect on
3642 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003643
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003644 rcupdate.rcu_normal_after_boot= [KNL]
3645 Once boot has completed (that is, after
3646 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003647 only normal grace-period primitives. No effect
3648 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003649
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003650 rcupdate.rcu_task_stall_timeout= [KNL]
3651 Set timeout in jiffies for RCU task stall warning
3652 messages. Disable with a value less than or equal
3653 to zero.
3654
Pranith Kumar74860fe2014-09-19 11:34:09 -04003655 rcupdate.rcu_self_test= [KNL]
3656 Run the RCU early boot self tests
3657
3658 rcupdate.rcu_self_test_bh= [KNL]
3659 Run the RCU bh early boot self tests
3660
3661 rcupdate.rcu_self_test_sched= [KNL]
3662 Run the RCU sched early boot self tests
3663
Olof Johanssonffdfc402005-09-06 15:17:19 -07003664 rdinit= [KNL]
3665 Format: <full_path>
3666 Run specified binary instead of /init from the ramdisk,
3667 used for early userspace startup. See initrd.
3668
Robin Holt1b3a5d02013-07-08 16:01:42 -07003669 reboot= [KNL]
3670 Format (x86 or x86_64):
3671 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3672 [[,]s[mp]#### \
3673 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3674 [[,]f[orce]
3675 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3676 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3677 reboot_force is either force or not specified,
3678 reboot_cpu is s[mp]#### with #### being the processor
3679 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003680
Paul Jackson46b6d942008-07-04 10:00:09 -07003681 relax_domain_level=
3682 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003683 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003684
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003685 relative_sleep_states=
3686 [SUSPEND] Use sleep state labeling where the deepest
3687 state available other than hibernation is always "mem".
3688 Format: { "0" | "1" }
3689 0 -- Traditional sleep state labels.
3690 1 -- Relative sleep state labels.
3691
Linus Torvalds1da177e2005-04-16 15:20:36 -07003692 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3693
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003694 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003695 Format: nn[KMG]
3696 Reserves a hole at the top of the kernel virtual
3697 address space.
3698
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003699 reservelow= [X86]
3700 Format: nn[K]
3701 Set the amount of memory to reserve for BIOS at
3702 the bottom of the address space.
3703
Vivek Goyal7e962872006-09-27 01:50:44 -07003704 reset_devices [KNL] Force drivers to reset the underlying device
3705 during initialization.
3706
Randy Dunlapa9913042005-10-23 12:57:11 -07003707 resume= [SWSUSP]
3708 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003709 Format:
3710 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003711
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003712 resume_offset= [SWSUSP]
3713 Specify the offset from the beginning of the partition
3714 given by "resume=" at which the swap header is located,
3715 in <PAGE_SIZE> units (needed only for swap files).
3716 See Documentation/power/swsusp-and-swap-files.txt
3717
Barry Songf126f732011-10-10 23:38:41 +02003718 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3719 read the resume files
3720
Barry Song6f8d7022011-10-06 20:34:46 +02003721 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3722 Useful for devices that are detected asynchronously
3723 (e.g. USB and MMC devices).
3724
Bojan Smojverf996fc92010-09-09 23:06:23 +02003725 hibernate= [HIBERNATION]
3726 noresume Don't check if there's a hibernation image
3727 present during boot.
3728 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003729 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003730 protect_image Turn on image protection during restoration
3731 (that will set all pages holding image data
3732 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003733
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003734 retain_initrd [RAM] Keep initrd memory after extraction
3735
Andrew Clausen0efbb782015-01-09 20:24:55 +00003736 rfkill.default_state=
3737 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3738 etc. communication is blocked by default.
3739 1 Unblocked.
3740
3741 rfkill.master_switch_mode=
3742 0 The "airplane mode" button does nothing.
3743 1 The "airplane mode" button toggles between everything
3744 blocked and the previous configuration.
3745 2 The "airplane mode" button toggles between everything
3746 blocked and everything unblocked.
3747
Linus Torvalds1da177e2005-04-16 15:20:36 -07003748 rhash_entries= [KNL,NET]
3749 Set number of hash buckets for route cache
3750
Linus Torvalds1da177e2005-04-16 15:20:36 -07003751 ro [KNL] Mount root device read-only on boot
3752
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003753 rodata= [KNL]
3754 on Mark read-only kernel memory as read-only (default).
3755 off Leave read-only kernel memory writable for debugging.
3756
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003757 rockchip.usb_uart
3758 Enable the uart passthrough on the designated usb port
3759 on Rockchip SoCs. When active, the signals of the
3760 debug-uart get routed to the D+ and D- pins of the usb
3761 port and the regular usb controller gets disabled.
3762
Linus Torvalds1da177e2005-04-16 15:20:36 -07003763 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003764 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003765
3766 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3767 mount the root filesystem
3768
3769 rootflags= [KNL] Set root filesystem mount option string
3770
3771 rootfstype= [KNL] Set root filesystem type
3772
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003773 rootwait [KNL] Wait (indefinitely) for root device to show up.
3774 Useful for devices that are detected asynchronously
3775 (e.g. USB and MMC devices).
3776
Robert Tivy5c71d612013-03-28 18:41:46 -07003777 rproc_mem=nn[KMG][@address]
3778 [KNL,ARM,CMA] Remoteproc physical memory block.
3779 Memory area to be used by remote processor image,
3780 managed by CMA.
3781
Linus Torvalds1da177e2005-04-16 15:20:36 -07003782 rw [KNL] Mount root device read-write on boot
3783
3784 S [KNL] Run init in single mode
3785
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003786 s390_iommu= [HW,S390]
3787 Set s390 IOTLB flushing mode
3788 strict
3789 With strict flushing every unmap operation will result in
3790 an IOTLB flush. Default is lazy flushing before reuse,
3791 which is faster.
3792
Linus Torvalds1da177e2005-04-16 15:20:36 -07003793 sa1100ir [NET]
3794 See drivers/net/irda/sa1100_ir.c.
3795
Linus Torvalds1da177e2005-04-16 15:20:36 -07003796 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003797
Mike Travisf6630112009-11-17 18:22:15 -06003798 sched_debug [KNL] Enables verbose scheduler debug messages.
3799
Mel Gormancb251762016-02-05 09:08:36 +00003800 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3801 Allowed values are enable and disable. This feature
3802 incurs a small amount of overhead in the scheduler
3803 but is useful for debugging and performance tuning.
3804
Mike Galbraith5307c952012-05-08 12:20:58 +02003805 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3806 xtime_lock contention on larger systems, and/or RCU lock
3807 contention on all systems with CONFIG_MAXSMP set.
3808 Format: { "0" | "1" }
3809 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3810 1 -- enable.
3811 Note: increases power consumption, thus should only be
3812 enabled if running jitter sensitive (HPC/RT) workloads.
3813
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003814 security= [SECURITY] Choose a security module to enable at boot.
3815 If this boot parameter is not specified, only the first
3816 security module asking for security registration will be
3817 loaded. An invalid security module name will be treated
3818 as if no module has been chosen.
3819
3820 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003821 Format: { "0" | "1" }
3822 See security/selinux/Kconfig help text.
3823 0 -- disable.
3824 1 -- enable.
3825 Default value is set via kernel config option.
3826 If enabled at boot time, /selinux/disable can be used
3827 later to disable prior to initial policy load.
3828
John Johansenc1c124e2010-07-29 14:48:09 -07003829 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3830 Format: { "0" | "1" }
3831 See security/apparmor/Kconfig help text
3832 0 -- disable.
3833 1 -- enable.
3834 Default value is set via kernel config option.
3835
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003836 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003837
Linus Torvalds1da177e2005-04-16 15:20:36 -07003838 shapers= [NET]
3839 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003840
Yinghai Lub05f78f2008-08-22 01:32:50 -07003841 show_msr= [x86] show boot-time MSR settings
3842 Format: { <integer> }
3843 Show boot-time (BIOS-initialized) MSR settings.
3844 The parameter means the number of CPUs to show,
3845 for example 1 means boot CPU only.
3846
Linus Torvalds1da177e2005-04-16 15:20:36 -07003847 simeth= [IA-64]
3848 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003849
Linus Torvalds1da177e2005-04-16 15:20:36 -07003850 slram= [HW,MTD]
3851
Joonsoo Kim423c9292014-10-09 15:26:22 -07003852 slab_nomerge [MM]
3853 Disable merging of slabs with similar size. May be
3854 necessary if there is some reason to distinguish
3855 allocs to different slabs. Debug options disable
3856 merging on their own.
3857 For more information see Documentation/vm/slub.txt.
3858
David Rientjes3df1ccc2011-10-18 22:09:28 -07003859 slab_max_order= [MM, SLAB]
3860 Determines the maximum allowed order for slabs.
3861 A high setting may cause OOMs due to memory
3862 fragmentation. Defaults to 1 for systems with
3863 more than 32MB of RAM, 0 otherwise.
3864
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003865 slub_debug[=options[,slabs]] [MM, SLUB]
3866 Enabling slub_debug allows one to determine the
3867 culprit if slab objects become corrupted. Enabling
3868 slub_debug can create guard zones around objects and
3869 may poison objects when not in use. Also tracks the
3870 last alloc / free. For more information see
3871 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003872
3873 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003874 Determines the maximum allowed order for slabs.
3875 A high setting may cause OOMs due to memory
3876 fragmentation. For more information see
3877 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003878
3879 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003880 The minimum number of objects per slab. SLUB will
3881 increase the slab order up to slub_max_order to
3882 generate a sufficiently large slab able to contain
3883 the number of objects indicated. The higher the number
3884 of objects the smaller the overhead of tracking slabs
3885 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003886 For more information see Documentation/vm/slub.txt.
3887
3888 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003889 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003890 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003891 For more information see Documentation/vm/slub.txt.
3892
3893 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003894 Same with slab_nomerge. This is supported for legacy.
3895 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003896
Linus Torvalds1da177e2005-04-16 15:20:36 -07003897 smart2= [HW]
3898 Format: <io1>[,<io2>[,...,<io8>]]
3899
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003900 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3901 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3902 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3903 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3904 smsc-ircc2.ircc_irq= [HW] IRQ line
3905 smsc-ircc2.ircc_dma= [HW] DMA channel
3906 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3907 0: Toshiba Satellite 1800 (GP data pin select)
3908 1: Fast pin select (default)
3909 2: ATC IRMode
3910
Sascha Silbe52c48c52016-04-05 12:53:38 +02003911 smt [KNL,S390] Set the maximum number of threads (logical
3912 CPUs) to use per physical CPU on systems capable of
3913 symmetric multithreading (SMT). Will be capped to the
3914 actual hardware limit.
3915 Format: <integer>
3916 Default: -1 (no limit)
3917
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003918 softlockup_panic=
3919 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003920 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003921
Aaron Tomlined235872014-06-23 13:22:05 -07003922 softlockup_all_cpu_backtrace=
3923 [KNL] Should the soft-lockup detector generate
3924 backtraces on all cpus.
3925 Format: <integer>
3926
Linus Torvalds1da177e2005-04-16 15:20:36 -07003927 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003928 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003929
Linus Torvalds1da177e2005-04-16 15:20:36 -07003930 spia_io_base= [HW,MTD]
3931 spia_fio_base=
3932 spia_pedr=
3933 spia_peddr=
3934
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003935 stacktrace [FTRACE]
3936 Enabled the stack tracer on boot up.
3937
Steven Rostedt762e1202011-12-19 22:01:00 -05003938 stacktrace_filter=[function-list]
3939 [FTRACE] Limit the functions that the stack tracer
3940 will trace at boot up. function-list is a comma separated
3941 list of functions. This list can be changed at run
3942 time by the stack_trace_filter file in the debugfs
3943 tracing directory. Note, this enables stack tracing
3944 and the stacktrace above is not needed.
3945
Linus Torvalds1da177e2005-04-16 15:20:36 -07003946 sti= [PARISC,HW]
3947 Format: <num>
3948 Set the STI (builtin display/keyboard on the HP-PARISC
3949 machines) console (graphic card) which should be used
3950 as the initial boot-console.
3951 See also comment in drivers/video/console/sticore.c.
3952
3953 sti_font= [HW]
3954 See comment in drivers/video/console/sticore.c.
3955
3956 stifb= [HW]
3957 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3958
Trond Myklebustcbf11072009-08-09 15:06:19 -04003959 sunrpc.min_resvport=
3960 sunrpc.max_resvport=
3961 [NFS,SUNRPC]
3962 SunRPC servers often require that client requests
3963 originate from a privileged port (i.e. a port in the
3964 range 0 < portnr < 1024).
3965 An administrator who wishes to reserve some of these
3966 ports for other uses may adjust the range that the
3967 kernel's sunrpc client considers to be privileged
3968 using these two parameters to set the minimum and
3969 maximum port values.
3970
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003971 sunrpc.svc_rpc_per_connection_limit=
3972 [NFS,SUNRPC]
3973 Limit the number of requests that the server will
3974 process in parallel from a single connection.
3975 The default value is 0 (no limit).
3976
Greg Banks42a7fc42007-03-06 01:42:23 -08003977 sunrpc.pool_mode=
3978 [NFS]
3979 Control how the NFS server code allocates CPUs to
3980 service thread pools. Depending on how many NICs
3981 you have and where their interrupts are bound, this
3982 option will affect which CPUs will do NFS serving.
3983 Note: this parameter cannot be changed while the
3984 NFS server is running.
3985
3986 auto the server chooses an appropriate mode
3987 automatically using heuristics
3988 global a single global pool contains all CPUs
3989 percpu one pool for each CPU
3990 pernode one pool for each NUMA node (equivalent
3991 to global on non-NUMA machines)
3992
Trond Myklebustcbf11072009-08-09 15:06:19 -04003993 sunrpc.tcp_slot_table_entries=
3994 sunrpc.udp_slot_table_entries=
3995 [NFS,SUNRPC]
3996 Sets the upper limit on the number of simultaneous
3997 RPC calls that can be sent from the client to a
3998 server. Increasing these values may allow you to
3999 improve throughput, but will also increase the
4000 amount of memory reserved for use by the client.
4001
Brian Norris1d4a9c12015-02-22 21:16:49 -08004002 suspend.pm_test_delay=
4003 [SUSPEND]
4004 Sets the number of seconds to remain in a suspend test
4005 mode before resuming the system (see
4006 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4007 is set. Default value is 5.
4008
Michal Hocko07555ac2013-08-22 16:35:46 -07004009 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08004010 [KNL] Enable accounting of swap in memory resource
4011 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09004012 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08004013
Jiri Kosina91fec0f2013-11-27 13:48:09 +01004014 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoeven41c6b3e2016-12-16 14:28:42 +01004015 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01004016 <int> -- Number of I/O TLB slabs
4017 force -- force using of bounce buffers even if they
4018 wouldn't be automatically used by the kernel
Geert Uytterhoeven41c6b3e2016-12-16 14:28:42 +01004019 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07004020
Linus Torvalds1da177e2005-04-16 15:20:36 -07004021 switches= [HW,M68k]
4022
Andi Kleene52eec12010-09-08 16:54:17 +02004023 sysfs.deprecated=0|1 [KNL]
4024 Enable/disable old style sysfs layout for old udev
4025 on older distributions. When this option is enabled
4026 very new udev will not work anymore. When this option
4027 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4028 in older udev will not work anymore.
4029 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4030 the kernel configuration.
4031
Ingo Molnar5d6f6472006-12-13 00:34:36 -08004032 sysrq_always_enabled
4033 [KNL]
4034 Ignore sysrq setting - this boot parameter will
4035 neutralize any effect of /proc/sys/kernel/sysrq.
4036 Useful for debugging.
4037
Fabian Frederick747029a2014-11-06 19:46:50 +01004038 tcpmhash_entries= [KNL,NET]
4039 Set the number of tcp_metrics_hash slots.
4040 Default value is 8192 or 16384 depending on total
4041 ram pages. This is used to specify the TCP metrics
4042 cache size. See Documentation/networking/ip-sysctl.txt
4043 "tcp_no_metrics_save" section for more details.
4044
Linus Torvalds1da177e2005-04-16 15:20:36 -07004045 tdfx= [HW,DRM]
4046
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004047 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07004048 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07004049 standby suspend) or "freeze" (for suspend type freeze)
4050 as the system sleep state during system startup with
4051 the optional capability to repeat N number of times.
4052 The system is woken from this state using a
4053 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07004054
Linus Torvalds1da177e2005-04-16 15:20:36 -07004055 thash_entries= [KNL,NET]
4056 Set number of hash buckets for TCP connection
4057
Len Brownf8707ec2007-08-12 00:12:54 -04004058 thermal.act= [HW,ACPI]
4059 -1: disable all active trip points in all thermal zones
4060 <degrees C>: override all lowest active trip points
4061
Len Brownc52a7412007-08-14 15:49:32 -04004062 thermal.crt= [HW,ACPI]
4063 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04004064 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04004065
Len Brownf5487142007-08-12 00:12:44 -04004066 thermal.nocrt= [HW,ACPI]
4067 Set to disable actions on ACPI thermal zone
4068 critical and hot trip points.
4069
Len Brown72b33ef2007-08-12 00:12:17 -04004070 thermal.off= [HW,ACPI]
4071 1: disable ACPI thermal control
4072
Len Browna70cdc52007-08-12 00:12:35 -04004073 thermal.psv= [HW,ACPI]
4074 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08004075 <degrees C>: override all passive trip points to this
4076 value
Len Browna70cdc52007-08-12 00:12:35 -04004077
Len Brown730ff342007-08-12 00:12:26 -04004078 thermal.tzp= [HW,ACPI]
4079 Specify global default ACPI thermal zone polling rate
4080 <deci-seconds>: poll all this frequency
4081 0: no polling (default)
4082
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004083 threadirqs [KNL]
4084 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09004085 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00004086
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004087 tmem [KNL,XEN]
4088 Enable the Transcendent memory driver if built-in.
4089
4090 tmem.cleancache=0|1 [KNL, XEN]
4091 Default is on (1). Disable the usage of the cleancache
4092 API to send anonymous pages to the hypervisor.
4093
4094 tmem.frontswap=0|1 [KNL, XEN]
4095 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04004096 API to send swap pages to the hypervisor. If disabled
4097 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04004098
4099 tmem.selfballooning=0|1 [KNL, XEN]
4100 Default is on (1). Disable the driving of swap pages
4101 to the hypervisor.
4102
4103 tmem.selfshrinking=0|1 [KNL, XEN]
4104 Default is on (1). Partial swapoff that immediately
4105 transfers pages from Xen hypervisor back to the
4106 kernel based on different criteria.
4107
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004108 topology= [S390]
4109 Format: {off | on}
4110 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07004111 topology information if the hardware supports this.
4112 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004113 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02004114 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01004115
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07004116 topology_updates= [KNL, PPC, NUMA]
4117 Format: {off}
4118 Specify if the kernel should ignore (off)
4119 topology updates sent by the hypervisor to this
4120 LPAR.
4121
Linus Torvalds1da177e2005-04-16 15:20:36 -07004122 tp720= [HW,PS2]
4123
Rajiv Andrade225a9be2010-03-25 00:55:32 -03004124 tpm_suspend_pcr=[HW,TPM]
4125 Format: integer pcr id
4126 Specify that at suspend time, the tpm driver
4127 should extend the specified pcr with zeros,
4128 as a workaround for some chips which fail to
4129 flush the last written pcr on TPM_SaveState.
4130 This will guarantee that all the other pcrs
4131 are saved.
4132
Li Zefan9d612be2009-06-24 17:33:15 +08004133 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09004134 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09004135
Li Zefan020e5f82009-07-01 10:47:05 +08004136 trace_event=[event-list]
4137 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07004138 to facilitate early boot debugging. The event-list is a
4139 comma separated list of trace events to enable. See
4140 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08004141
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04004142 trace_options=[option-list]
4143 [FTRACE] Enable or disable tracer options at boot.
4144 The option-list is a comma delimited list of options
4145 that can be enabled or disabled just as if you were
4146 to echo the option name into
4147
4148 /sys/kernel/debug/tracing/trace_options
4149
4150 For example, to enable stacktrace option (to dump the
4151 stack trace of each event), add to the command line:
4152
4153 trace_options=stacktrace
4154
4155 See also Documentation/trace/ftrace.txt "trace options"
4156 section.
4157
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05004158 tp_printk[FTRACE]
4159 Have the tracepoints sent to printk as well as the
4160 tracing ring buffer. This is useful for early boot up
4161 where the system hangs or reboots and does not give the
4162 option for reading the tracing buffer or performing a
4163 ftrace_dump_on_oops.
4164
4165 To turn off having tracepoints sent to printk,
4166 echo 0 > /proc/sys/kernel/tracepoint_printk
4167 Note, echoing 1 into this file without the
4168 tracepoint_printk kernel cmdline option has no effect.
4169
4170 ** CAUTION **
4171
4172 Having tracepoints sent to printk() and activating high
4173 frequency tracepoints such as irq or sched, can cause
4174 the system to live lock.
4175
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004176 traceoff_on_warning
4177 [FTRACE] enable this option to disable tracing when a
4178 warning is hit. This turns off "tracing_on". Tracing can
4179 be enabled again by echoing '1' into the "tracing_on"
4180 file located in /sys/kernel/debug/tracing/
4181
4182 This option is useful, as it disables the trace before
4183 the WARNING dump is called, which prevents the trace to
4184 be filled with content caused by the warning output.
4185
4186 This option can also be set at run time via the sysctl
4187 option: kernel/traceoff_on_warning
4188
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004189 transparent_hugepage=
4190 [KNL]
4191 Format: [always|madvise|never]
4192 Can be used to control the default behavior of the system
4193 with respect to transparent hugepages.
4194 See Documentation/vm/transhuge.txt for more details.
4195
john stultzd3b8f882009-08-17 16:40:47 -07004196 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004197 Format: <string>
4198 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004199 disables clocksource verification at runtime, as well
4200 as the stability checks done at bootup. Used to enable
4201 high-resolution timer mode on older hardware, and in
4202 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004203 [x86] noirqtime: Do not use TSC to do irq accounting.
4204 Used to run time disable IRQ_TIME_ACCOUNTING on any
4205 platforms where RDTSC is slow and this accounting
4206 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004207
Randy Dunlapa9913042005-10-23 12:57:11 -07004208 turbografx.map[2|3]= [HW,JOY]
4209 TurboGraFX parallel port interface
4210 Format:
4211 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004212 See also Documentation/input/joystick-parport.txt
4213
Christian Kujaub6935f82011-05-31 15:22:05 +00004214 udbg-immortal [PPC] When debugging early kernel crashes that
4215 happen after console_init() and before a proper
4216 console driver takes over, this boot options might
4217 help "seeing" what's going on.
4218
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004219 uhash_entries= [KNL,NET]
4220 Set number of hash buckets for UDP/UDP-Lite connections
4221
Alan Stern5f8364b2006-12-05 16:29:55 -05004222 uhci-hcd.ignore_oc=
4223 [USB] Ignore overcurrent events (default N).
4224 Some badly-designed motherboards generate lots of
4225 bogus events, for ports that aren't wired to
4226 anything. Set this parameter to avoid log spamming.
4227 Note that genuine overcurrent events won't be
4228 reported either.
4229
Simon Arlotte3a61b02008-07-19 23:32:54 +01004230 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004231 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004232
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004233 usbcore.authorized_default=
4234 [USB] Default USB device authorization:
4235 (default -1 = authorized except for wireless USB,
4236 0 = not authorized, 1 = authorized)
4237
Alan Sternb5e795f2007-02-20 15:00:53 -05004238 usbcore.autosuspend=
4239 [USB] The autosuspend time delay (in seconds) used
4240 for newly-detected USB devices (default 2). This
4241 is the time required before an idle device will be
4242 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004243 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004244
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004245 usbcore.usbfs_snoop=
4246 [USB] Set to log all usbfs traffic (default 0 = off).
4247
Alan Stern0290cc92015-11-20 13:53:22 -05004248 usbcore.usbfs_snoop_max=
4249 [USB] Maximum number of bytes to snoop in each URB
4250 (default = 65536).
4251
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004252 usbcore.blinkenlights=
4253 [USB] Set to cycle leds on hubs (default 0 = off).
4254
4255 usbcore.old_scheme_first=
4256 [USB] Start with the old device initialization
4257 scheme (default 0 = off).
4258
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004259 usbcore.usbfs_memory_mb=
4260 [USB] Memory limit (in MB) for buffers allocated by
4261 usbfs (default = 16, 0 = max = 2047).
4262
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004263 usbcore.use_both_schemes=
4264 [USB] Try the other device initialization scheme
4265 if the first one fails (default 1 = enabled).
4266
4267 usbcore.initial_descriptor_timeout=
4268 [USB] Specifies timeout for the initial 64-byte
4269 USB_REQ_GET_DESCRIPTOR request in milliseconds
4270 (default 5000 = 5.0 seconds).
4271
Oliver Neukum40d58142015-12-03 15:03:32 +01004272 usbcore.nousb [USB] Disable the USB subsystem
4273
Linus Torvalds1da177e2005-04-16 15:20:36 -07004274 usbhid.mousepoll=
4275 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004276
Alan Sternd4f373e2008-11-10 14:07:45 -05004277 usb-storage.delay_use=
4278 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004279 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004280
4281 usb-storage.quirks=
4282 [UMS] A list of quirks entries to supplement or
4283 override the built-in unusual_devs list. List
4284 entries are separated by commas. Each entry has
4285 the form VID:PID:Flags where VID and PID are Vendor
4286 and Product ID values (4-digit hex numbers) and
4287 Flags is a set of characters, each corresponding
4288 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004289 a = SANE_SENSE (collect more than 18 bytes
4290 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004291 b = BAD_SENSE (don't collect more than 18
4292 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004293 c = FIX_CAPACITY (decrease the reported
4294 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004295 d = NO_READ_DISC_INFO (don't use
4296 READ_DISC_INFO command);
4297 e = NO_READ_CAPACITY_16 (don't use
4298 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004299 f = NO_REPORT_OPCODES (don't use report opcodes
4300 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004301 g = MAX_SECTORS_240 (don't transfer more than
4302 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004303 h = CAPACITY_HEURISTICS (decrease the
4304 reported device capacity by one
4305 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004306 i = IGNORE_DEVICE (don't bind to this
4307 device);
Hans de Goede13630742016-04-12 12:27:09 +02004308 j = NO_REPORT_LUNS (don't use report luns
4309 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004310 l = NOT_LOCKABLE (don't try to lock and
4311 unlock ejectable media);
4312 m = MAX_SECTORS_64 (don't transfer more
4313 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004314 n = INITIAL_READ10 (force a retry of the
4315 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004316 o = CAPACITY_OK (accept the capacity
4317 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004318 p = WRITE_CACHE (the device cache is ON
4319 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004320 r = IGNORE_RESIDUE (the device reports
4321 bogus residue values);
4322 s = SINGLE_LUN (the device has only one
4323 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004324 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4325 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004326 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004327 w = NO_WP_DETECT (don't test whether the
4328 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004329 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4330 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004331 Example: quirks=0419:aaf5:rl,0421:0433:rc
4332
Stephen Boydac1667d2011-08-13 12:34:50 -07004333 user_debug= [KNL,ARM]
4334 Format: <int>
4335 See arch/arm/Kconfig.debug help text.
4336 1 - undefined instruction events
4337 2 - system calls
4338 4 - invalid data aborts
4339 8 - SIGSEGV faults
4340 16 - SIGBUS faults
4341 Example: user_debug=31
4342
Ian Campbell14315592010-02-17 10:38:10 +00004343 userpte=
4344 [X86] Flags controlling user PTE allocations.
4345
4346 nohigh = do not allocate PTE pages in
4347 HIGHMEM regardless of setting
4348 of CONFIG_HIGHPTE.
4349
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304350 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004351 On X86_32, this is an alias for vdso32=. Otherwise:
4352
4353 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004354 vdso=0: disable VDSO mapping
4355
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004356 vdso32= [X86] Control the 32-bit vDSO
4357 vdso32=1: enable 32-bit VDSO
4358 vdso32=0 or vdso32=2: disable 32-bit VDSO
4359
4360 See the help text for CONFIG_COMPAT_VDSO for more
4361 details. If CONFIG_COMPAT_VDSO is set, the default is
4362 vdso32=0; otherwise, the default is vdso32=1.
4363
4364 For compatibility with older kernels, vdso32=2 is an
4365 alias for vdso32=0.
4366
4367 Try vdso32=0 if you encounter an error that says:
4368 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004369
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004370 vector= [IA-64,SMP]
4371 vector=percpu: enable percpu vector domain
4372
Linus Torvalds1da177e2005-04-16 15:20:36 -07004373 video= [FB] Frame buffer configuration
4374 See Documentation/fb/modedb.txt.
4375
Aaron Lu3afe6da2013-06-20 15:08:55 +08004376 video.brightness_switch_enabled= [0,1]
4377 If set to 1, on receiving an ACPI notify event
4378 generated by hotkey, video driver will adjust brightness
4379 level and then send out the event to user space through
4380 the allocated input device; If set to 0, video driver
4381 will only send out the event without touching backlight
4382 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004383 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004384
Pawel Moll81a054c2012-05-09 18:30:16 +01004385 virtio_mmio.device=
4386 [VMMIO] Memory mapped virtio (platform) device.
4387
4388 <size>@<baseaddr>:<irq>[:<id>]
4389 where:
4390 <size> := size (can use standard suffixes
4391 like K, M and G)
4392 <baseaddr> := physical base address
4393 <irq> := interrupt number (as passed to
4394 request_irq())
4395 <id> := (optional) platform device id
4396 example:
4397 virtio_mmio.device=1K@0x100b0000:48:7
4398
4399 Can be used multiple times for multiple devices.
4400
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004401 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004402 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004403 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004404 Use vga=ask for menu.
4405 This is actually a boot loader parameter; the value is
4406 passed to the kernel using a special protocol.
4407
Randy Dunlapa9913042005-10-23 12:57:11 -07004408 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004409 size of <nn>. This can be used to increase the
4410 minimum size (128MB on x86). It can also be used to
4411 decrease the size and leave more room for directly
4412 mapped kernel RAM.
4413
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004414 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4415 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004416
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004417 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4418 Format: <command>
4419
4420 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4421 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004422
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004423 vsyscall= [X86-64]
4424 Controls the behavior of vsyscalls (i.e. calls to
4425 fixed addresses of 0xffffffffff600x00 from legacy
4426 code). Most statically-linked binaries and older
4427 versions of glibc use these calls. Because these
4428 functions are at fixed addresses, they make nice
4429 targets for exploits that can control RIP.
4430
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004431 emulate [default] Vsyscalls turn into traps and are
4432 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004433
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004434 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004435 This is a little bit faster than trapping
4436 and makes a few dynamic recompilers work
4437 better than they would in emulation mode.
4438 It also makes exploits much easier to write.
4439
4440 none Vsyscalls don't work at all. This makes
4441 them quite hard to use for exploits but
4442 might break your system.
4443
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004444 vt.color= [VT] Default text color.
4445 Format: 0xYX, X = foreground, Y = background.
4446 Default: 0x07 = light gray on black.
4447
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004448 vt.cur_default= [VT] Default cursor shape.
4449 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4450 the parameters of the <Esc>[?A;B;Cc escape sequence;
4451 see VGA-softcursor.txt. Default: 2 = underline.
4452
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004453 vt.default_blu= [VT]
4454 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4455 Change the default blue palette of the console.
4456 This is a 16-member array composed of values
4457 ranging from 0-255.
4458
4459 vt.default_grn= [VT]
4460 Format: <green0>,<green1>,<green2>,...,<green15>
4461 Change the default green palette of the console.
4462 This is a 16-member array composed of values
4463 ranging from 0-255.
4464
4465 vt.default_red= [VT]
4466 Format: <red0>,<red1>,<red2>,...,<red15>
4467 Change the default red palette of the console.
4468 This is a 16-member array composed of values
4469 ranging from 0-255.
4470
4471 vt.default_utf8=
4472 [VT]
4473 Format=<0|1>
4474 Set system-wide default UTF-8 mode for all tty's.
4475 Default is 1, i.e. UTF-8 mode is enabled for all
4476 newly opened terminals.
4477
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004478 vt.global_cursor_default=
4479 [VT]
4480 Format=<-1|0|1>
4481 Set system-wide default for whether a cursor
4482 is shown on new VTs. Default is -1,
4483 i.e. cursors will be created by default unless
4484 overridden by individual drivers. 0 will hide
4485 cursors, 1 will display them.
4486
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004487 vt.italic= [VT] Default color for italic text; 0-15.
4488 Default: 2 = green.
4489
4490 vt.underline= [VT] Default color for underlined text; 0-15.
4491 Default: 3 = cyan.
4492
Randy Dunlap4724ba572010-05-03 11:42:52 -07004493 watchdog timers [HW,WDT] For information on watchdog timers,
4494 see Documentation/watchdog/watchdog-parameters.txt
4495 or other driver-specific files in the
4496 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004497
Tejun Heo82607adc2015-12-08 11:28:04 -05004498 workqueue.watchdog_thresh=
4499 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4500 warn stall conditions and dump internal state to
4501 help debugging. 0 disables workqueue stall
4502 detection; otherwise, it's the stall threshold
4503 duration in seconds. The default value is 30 and
4504 it can be updated at runtime by writing to the
4505 corresponding sysfs file.
4506
Tejun Heod55262c2013-04-01 11:23:38 -07004507 workqueue.disable_numa
4508 By default, all work items queued to unbound
4509 workqueues are affine to the NUMA nodes they're
4510 issued on, which results in better behavior in
4511 general. If NUMA affinity needs to be disabled for
4512 whatever reason, this option can be used. Note
4513 that this also can be controlled per-workqueue for
4514 workqueues visible under /sys/bus/workqueue/.
4515
Viresh Kumarcee22a12013-04-08 16:45:40 +05304516 workqueue.power_efficient
4517 Per-cpu workqueues are generally preferred because
4518 they show better performance thanks to cache
4519 locality; unfortunately, per-cpu workqueues tend to
4520 be more power hungry than unbound workqueues.
4521
4522 Enabling this makes the per-cpu workqueues which
4523 were observed to contribute significantly to power
4524 consumption unbound, leading to measurably lower
4525 power usage at the cost of small performance
4526 overhead.
4527
4528 The default value of this parameter is determined by
4529 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4530
Tejun Heof303fcc2016-02-09 17:59:38 -05004531 workqueue.debug_force_rr_cpu
4532 Workqueue used to implicitly guarantee that work
4533 items queued without explicit CPU specified are put
4534 on the local CPU. This guarantee is no longer true
4535 and while local CPU is still preferred work items
4536 may be put on foreign CPUs. This debug option
4537 forces round-robin CPU selection to flush out
4538 usages which depend on the now broken guarantee.
4539 When enabled, memory and cache locality will be
4540 impacted.
4541
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004542 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4543 default x2apic cluster mode on platforms
4544 supporting x2apic.
4545
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004546 x86_intel_mid_timer= [X86-32,APBT]
4547 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004548 Two valid options are apbt timer only and lapic timer
4549 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004550 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004551
Juergen Grossc70727a2015-07-17 06:51:36 +02004552 xen_512gb_limit [KNL,X86-64,XEN]
4553 Restricts the kernel running paravirtualized under Xen
4554 to use only up to 512 GB of RAM. The reason to do so is
4555 crash analysis tools and Xen tools for doing domain
4556 save/restore/migration must be enabled to handle larger
4557 domains.
4558
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004559 xen_emul_unplug= [HW,X86,XEN]
4560 Unplug Xen emulated devices
4561 Format: [unplug0,][unplug1]
4562 ide-disks -- unplug primary master IDE devices
4563 aux-ide-disks -- unplug non-primary-master IDE devices
4564 nics -- unplug network devices
4565 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004566 unnecessary -- unplugging emulated devices is
4567 unnecessary even if the host did not respond to
4568 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004569 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004570
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004571 xen_nopvspin [X86,XEN]
4572 Disables the ticketlock slowpath using Xen PV
4573 optimizations.
4574
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004575 xen_nopv [X86]
4576 Disables the PV optimizations forcing the HVM guest to
4577 run as generic HVM guest with no PV drivers.
4578
Linus Torvalds1da177e2005-04-16 15:20:36 -07004579 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004580 Format:
4581 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07004582
Randy Dunlapa9913042005-10-23 12:57:11 -07004583______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07004584
4585TODO:
4586
Linus Torvalds1da177e2005-04-16 15:20:36 -07004587 Add more DRM drivers.