1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
18 acpi_apic_instance= [ACPI, IOAPIC]
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
24 acpi_backlight= [HW,ACPI]
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
73 acpi_enforce_resources= [ACPI]
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
107 Format: <irq>,<irq>...
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
114 This facility can be used to prevent such uncontrolled
118 acpi_no_auto_serialize [HW,ACPI]
119 Disable auto-serialization of AML methods
120 AML control methods that contain the opcodes to create
121 named objects will be marked as "Serialized" by the
122 auto-serialization feature.
123 This feature is enabled by default.
124 This option allows to turn off the feature.
126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
129 acpi_no_static_ssdt [HW,ACPI]
130 Disable installation of static SSDTs at early boot time
131 By default, SSDTs contained in the RSDT/XSDT will be
132 installed automatically and they will appear under
133 /sys/firmware/acpi/tables.
134 This option turns off this feature.
135 Note that specifying this option does not affect
136 dynamic table installation which will install SSDT
137 tables to /sys/firmware/acpi/tables/dynamic.
139 acpi_rsdp= [ACPI,EFI,KEXEC]
140 Pass the RSDP address to the kernel, mostly used
141 on machines running EFI runtime service to boot the
142 second kernel for kdump.
144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
145 Format: To spoof as Windows 98: ="Microsoft Windows"
147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148 of 2 which is mandated by ACPI 6) as the supported ACPI
149 specification revision (when using this switch, it may
150 be necessary to carry out a cold reboot _twice_ in a
151 row to make it take effect on the platform firmware).
153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
154 acpi_osi="string1" # add string1
155 acpi_osi="!string2" # remove string2
156 acpi_osi=!* # remove all strings
157 acpi_osi=! # disable all built-in OS vendor
159 acpi_osi=!! # enable all built-in OS vendor
161 acpi_osi= # disable all strings
163 'acpi_osi=!' can be used in combination with single or
164 multiple 'acpi_osi="string1"' to support specific OS
165 vendor string(s). Note that such command can only
166 affect the default state of the OS vendor strings, thus
167 it cannot affect the default state of the feature group
168 strings and the current state of the OS vendor strings,
169 specifying it multiple times through kernel command line
170 is meaningless. This command is useful when one do not
171 care about the state of the feature group strings which
172 should be controlled by the OSPM.
174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176 can make '_OSI("Windows 2000")' TRUE.
178 'acpi_osi=' cannot be used in combination with other
179 'acpi_osi=' command lines, the _OSI method will not
180 exist in the ACPI namespace. NOTE that such command can
181 only affect the _OSI support state, thus specifying it
182 multiple times through kernel command line is also
185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
188 'acpi_osi=!*' can be used in combination with single or
189 multiple 'acpi_osi="string1"' to support specific
190 string(s). Note that such command can affect the
191 current state of both the OS vendor strings and the
192 feature group strings, thus specifying it multiple times
193 through kernel command line is meaningful. But it may
194 still not able to affect the final state of a string if
195 there are quirks related to this string. This command
196 is useful when one want to control the state of the
197 feature group strings to debug BIOS issues related to
200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201 '_OSI("Module Device")' FALSE.
202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203 '_OSI("Module Device")' TRUE.
204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209 they all will make '_OSI("Windows 2000")' TRUE.
212 Override the pmtimer bug detection: force the kernel
213 to assume that this machine's pmtimer latches its value
214 and always returns good values.
216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
217 Format: { level | edge | high | low }
219 acpi_skip_timer_override [HW,ACPI]
220 Recognize and ignore IRQ0/pin2 Interrupt Override.
221 For broken nForce2 BIOS resulting in XT-PIC timer.
223 acpi_sleep= [HW,ACPI] Sleep options
224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
225 old_ordering, nonvs, sci_force_enable, nobl }
226 See Documentation/power/video.txt for information on
228 s3_beep is for debugging; it makes the PC's speaker beep
229 as soon as the kernel's real-mode entry point is called.
230 s4_nohwsig prevents ACPI hardware signature from being
231 used during resume from hibernation.
232 old_ordering causes the ACPI 1.0 ordering of the _PTS
233 control method, with respect to putting devices into
234 low power states, to be enforced (the ACPI 2.0 ordering
235 of _PTS is used by default).
236 nonvs prevents the kernel from saving/restoring the
237 ACPI NVS memory during suspend/hibernation and resume.
238 sci_force_enable causes the kernel to set SCI_EN directly
239 on resume from S1/S3 (which is against the ACPI spec,
240 but some broken systems don't work without it).
241 nobl causes the internal blacklist of systems known to
242 behave incorrectly in some ways with respect to system
243 suspend and resume to be ignored (use wisely).
245 acpi_use_timer_override [HW,ACPI]
246 Use timer override. For some broken Nvidia NF5 boards
247 that require a timer override, but don't have HPET
249 add_efi_memmap [EFI; X86] Include EFI memory map in
250 kernel's map of available physical RAM.
253 { off | try_unsupported }
254 off: disable AGP support
255 try_unsupported: try to drive unsupported chipsets
256 (may crash computer or cause data corruption)
259 See Documentation/sound/alsa-configuration.rst
262 Allow the default userspace alignment fault handler
263 behaviour to be specified. Bit 0 enables warnings,
264 bit 1 enables fixups, and bit 2 sends a segfault.
266 align_va_addr= [X86-64]
267 Align virtual addresses by clearing slice [14:12] when
268 allocating a VMA at process creation time. This option
269 gives you up to 3% performance improvement on AMD F15h
270 machines (where it is enabled by default) for a
271 CPU-intensive style benchmark, and it can vary highly in
272 a microbenchmark depending on workload and compiler.
274 32: only for 32-bit processes
275 64: only for 64-bit processes
276 on: enable for both 32- and 64-bit processes
277 off: disable for both 32- and 64-bit processes
279 alloc_snapshot [FTRACE]
280 Allocate the ftrace snapshot buffer on boot up when the
281 main buffer is allocated. This is handy if debugging
282 and you need to use tracing_snapshot() on boot up, and
283 do not want to use tracing_snapshot_alloc() as it needs
284 to be done where GFP_KERNEL allocations are allowed.
286 amd_iommu= [HW,X86-64]
287 Pass parameters to the AMD IOMMU driver in the system.
289 fullflush - enable flushing of IO/TLB entries when
290 they are unmapped. Otherwise they are
291 flushed before they will be reused, which
293 off - do not initialize any AMD IOMMU found in
295 force_isolation - Force device isolation for all
296 devices. The IOMMU driver is not
297 allowed anymore to lift isolation
298 requirements as needed. This option
299 does not override iommu=pt
301 amd_iommu_dump= [HW,X86-64]
302 Enable AMD IOMMU driver option to dump the ACPI table
303 for AMD IOMMU. With this option enabled, AMD IOMMU
304 driver will print ACPI tables for AMD IOMMU during
305 IOMMU initialization.
307 amd_iommu_intr= [HW,X86-64]
308 Specifies one of the following AMD IOMMU interrupt
310 legacy - Use legacy interrupt remapping mode.
311 vapic - Use virtual APIC mode, which allows IOMMU
312 to inject interrupts directly into guest.
313 This mode requires kvm-amd.avic=1.
314 (Default when IOMMU HW support is present.)
316 amijoy.map= [HW,JOY] Amiga joystick support
317 Map of devices attached to JOY0DAT and JOY1DAT
319 See also Documentation/input/joydev/joystick.rst
321 analog.map= [HW,JOY] Analog joystick and gamepad support
322 Specifies type or capabilities of an analog joystick
323 connected to one of 16 gameports
324 Format: <type1>,<type2>,..<type16>
327 Power management functions (SPARCstation-4/5 + deriv.)
329 Disable APC CPU standby support. SPARCstation-Fox does
330 not play well with APC CPU idle - disable it if you have
331 APC and your system crashes randomly.
333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Change the output verbosity whilst booting
335 Format: { quiet (default) | verbose | debug }
336 Change the amount of debugging information output
337 when initialising the APIC and IO-APIC components.
338 For X86-32, this can also be used to specify an APIC
340 Format: apic=driver_name
341 Examples: apic=bigsmp
343 apic_extnmi= [APIC,X86] External NMI delivery setting
344 Format: { bsp (default) | all | none }
345 bsp: External NMI is delivered only to CPU 0
346 all: External NMIs are broadcast to all CPUs as a
348 none: External NMI is masked for all CPUs. This is
349 useful so that a dump capture kernel won't be
353 See Documentation/networking/ipv6.txt.
355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
364 apm= [APM] Advanced Power Management
365 See header of arch/x86/kernel/apm_32.c.
367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
372 atarimouse= [HW,MOUSE] Atari Mouse
374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
375 EzKey and similar keyboards
377 atkbd.reset= [HW] Reset keyboard during initialization
379 atkbd.set= [HW] Select keyboard code set
380 Format: <int> (2 = AT (default), 3 = PS/2)
382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
386 Format: <bool> (0 = real, 1 = synthetic (default))
388 atkbd.softrepeat= [HW]
389 Use software keyboard repeat
391 audit= [KNL] Enable the audit sub-system
392 Format: { "0" | "1" | "off" | "on" }
393 0 | off - kernel audit is disabled and can not be
394 enabled until the next reboot
395 unset - kernel audit is initialized but disabled and
396 will be fully enabled by the userspace auditd.
397 1 | on - kernel audit is initialized and partially
398 enabled, storing at most audit_backlog_limit
399 messages in RAM until it is fully enabled by the
403 audit_backlog_limit= [KNL] Set the audit queue size limit.
404 Format: <int> (must be >=0)
407 bau= [X86_UV] Enable the BAU on SGI UV. The default
408 behavior is to disable the BAU (i.e. bau=0).
409 Format: { "0" | "1" }
412 unset - Disable the BAU.
414 baycom_epp= [HW,AX25]
417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
419 See header of drivers/net/hamradio/baycom_par.c.
421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
431 blkdevparts= Manual partition parsing of block device(s) for
432 embedded devices based on command line input.
433 See Documentation/block/cmdline-partition.txt
435 boot_delay= Milliseconds to delay each printk during boot.
436 Values larger than 10 seconds (10000) are changed to
440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
443 Disable BERT OS support on buggy BIOSes.
445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
446 bttv.radio= Most important insmod options are available as
448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
452 firmware feature for flushing multiple hpte entries
455 c101= [NET] Moxa C101 synchronous serial card
457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
458 Sometimes CPU hardware bugs make them report the cache
459 size incorrectly. The kernel will attempt work arounds
460 to fix known problems, but for some CPUs it is not
461 possible to determine what the correct size should be.
462 This option provides an override for these situations.
464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
465 the system trusted keyring to be used for certificate
467 format: { id:<keyid> | builtin }
469 cca= [MIPS] Override the kernel pages' cache coherency
470 algorithm. Accepted values range from 0 to 7
471 inclusive. See arch/mips/include/asm/pgtable-bits.h
472 for platform specific values (SB1, Loongson3 and
475 ccw_timeout_log [S390]
476 See Documentation/s390/CommonIO for details.
478 cgroup_disable= [KNL] Disable a particular controller
479 Format: {name of the controller(s) to disable}
480 The effects of cgroup_disable=foo are:
481 - foo isn't auto-mounted if you mount all cgroups in
483 - foo isn't visible as an individually mountable
485 {Currently only "memory" controller deal with this and
486 cut the overhead, others just disable the usage. So
487 only cgroup_disable=memory is actually worthy}
489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
490 Format: { controller[,controller...] | "all" }
491 Like cgroup_disable, but only applies to cgroup v1;
492 the blacklisted controllers remain available in cgroup2.
494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
496 nosocket -- Disable socket memory accounting.
497 nokmem -- Disable kernel memory accounting.
499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
500 Format: { "0" | "1" }
501 See security/selinux/Kconfig help text.
502 0 -- check protection applied by kernel (includes
503 any implied execute protection).
504 1 -- check protection requested by application.
505 Default value is set via a kernel config option.
506 Value can be changed at runtime via
507 /selinux/checkreqprot.
510 See Documentation/s390/CommonIO for details.
513 Prevents the clock framework from automatically gating
514 clocks that have not been explicitly enabled by a Linux
515 device driver but are enabled in hardware at reset or
516 by the bootloader/firmware. Note that this does not
517 force such clocks to be always-on nor does it reserve
518 those clocks in any way. This parameter is useful for
519 debug and development, but should not be needed on a
520 platform with proper driver support. For more
521 information, see Documentation/driver-api/clk.rst.
523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
525 Forces specified clocksource (if available) to be used
526 when calculating gettimeofday(). If specified
527 clocksource is not available, it defaults to PIT.
528 Format: { pit | tsc | cyclone | pmtmr }
530 clocksource= Override the default clocksource
532 Override the default clocksource and use the clocksource
533 with the name specified.
534 Some clocksource names to choose from, depending on
536 [all] jiffies (this is the base, fallback clocksource)
538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
539 pxa_timer,timer3,32k_counter,timer0_1
540 [X86-32] pit,hpet,tsc;
541 scx200_hrt on Geode; cyclone on IBM x440
549 clocksource.arm_arch_timer.evtstrm=
552 Enable/disable the eventstream feature of the ARM
553 architected timer so that code using WFE-based polling
554 loops can be debugged more effectively on production
557 clearcpuid=BITNUM [X86]
558 Disable CPUID feature X for the kernel. See
559 arch/x86/include/asm/cpufeatures.h for the valid bit
560 numbers. Note the Linux specific bits are not necessarily
561 stable over kernel options, but the vendor specific
563 Also note that user programs calling CPUID directly
564 or using the feature without checking anything
565 will still see it. This just prevents it from
566 being used by the kernel or shown in /proc/cpuinfo.
567 Also note the kernel might malfunction if you disable
570 cma=nn[MG]@[start[MG][-end[MG]]]
572 Sets the size of kernel global memory area for
573 contiguous memory allocations and optionally the
574 placement constraint by the physical address range of
575 memory allocations. A value of 0 disables CMA
576 altogether. For more information, see
577 include/linux/dma-contiguous.h
579 cmo_free_hint= [PPC] Format: { yes | no }
580 Specify whether pages are marked as being inactive
581 when they are freed. This is used in CMO environments
582 to determine OS memory pressure for page stealing by
586 coherent_pool=nn[KMG] [ARM,KNL]
587 Sets the size of memory pool for coherent, atomic dma
588 allocations, by default set to 256K.
590 com20020= [HW,NET] ARCnet - COM20020 chipset
592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
598 ARCnet - COM90xx chipset (memory-mapped buffers)
599 Format: <io>[,<irq>[,<memstart>]]
601 condev= [HW,S390] console device
604 console= [KNL] Output console device and options.
606 tty<n> Use the virtual console device <n>.
610 Use the specified serial port. The options are of
611 the form "bbbbpnf", where "bbbb" is the baud rate,
612 "p" is parity ("n", "o", or "e"), "n" is number of
613 bits, and "f" is flow control ("r" for RTS or
614 omit it). Default is "9600n8".
616 See Documentation/admin-guide/serial-console.rst for more
618 Documentation/networking/netconsole.txt for an
621 uart[8250],io,<addr>[,options]
622 uart[8250],mmio,<addr>[,options]
623 uart[8250],mmio16,<addr>[,options]
624 uart[8250],mmio32,<addr>[,options]
625 uart[8250],0x<addr>[,options]
626 Start an early, polled-mode console on the 8250/16550
627 UART at the specified I/O port or MMIO address,
628 switching to the matching ttyS device later.
629 MMIO inter-register address stride is either 8-bit
630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
632 to be equivalent to 'mmio'. 'options' are specified in
633 the same format described for ttyS above; if unspecified,
634 the h/w is not re-initialized.
636 hvc<n> Use the hypervisor console device <n>. This is for
637 both Xen and PowerPC hypervisors.
639 If the device connected to the port is not a TTY but a braille
640 device, prepend "brl," before the device type, for instance
642 For now, only VisioBraille is supported.
645 [KNL] Change console messages format
647 By default we print messages on consoles in
648 "[time stamp] text\n" format (time stamp may not be
649 printed, depending on CONFIG_PRINTK_TIME or
650 `printk_time' param).
652 Switch to syslog format: "<%u>[time stamp] text\n"
653 IOW, each message will have a facility and loglevel
654 prefix. The format is similar to one used by syslog()
655 syscall, or to executing "dmesg -S --raw" or to reading
658 consoleblank= [KNL] The console blank (screen saver) timeout in
659 seconds. A value of 0 disables the blank timer.
663 [KNL] Change the default value for
664 /proc/<pid>/coredump_filter.
665 See also Documentation/filesystems/proc.txt.
667 coresight_cpu_debug.enable
670 Enable/disable the CPU sampling based debugging.
671 0: default value, disable debugging
672 1: enable debugging at boot time
674 cpuidle.off=1 [CPU_IDLE]
675 disable the cpuidle sub-system
677 cpufreq.off=1 [CPU_FREQ]
678 disable the cpufreq sub-system
681 [X86] Delay for N microsec between assert and de-assert
682 of APIC INIT to start processors. This delay occurs
683 on every CPU online, such as boot, and resume from suspend.
686 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
688 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
690 crashkernel=size[KMG][@offset[KMG]]
691 [KNL] Using kexec, Linux can switch to a 'crash kernel'
692 upon panic. This parameter reserves the physical
693 memory region [offset, offset + size] for that kernel
694 image. If '@offset' is omitted, then a suitable offset
695 is selected automatically. Check
696 Documentation/kdump/kdump.txt for further details.
698 crashkernel=range1:size1[,range2:size2,...][@offset]
699 [KNL] Same as above, but depends on the memory
700 in the running system. The syntax of range is
701 start-[end] where start and end are both
702 a memory unit (amount[KMG]). See also
703 Documentation/kdump/kdump.txt for an example.
705 crashkernel=size[KMG],high
706 [KNL, x86_64] range could be above 4G. Allow kernel
707 to allocate physical memory region from top, so could
708 be above 4G if system have more than 4G ram installed.
709 Otherwise memory region will be allocated below 4G, if
711 It will be ignored if crashkernel=X is specified.
712 crashkernel=size[KMG],low
713 [KNL, x86_64] range under 4G. When crashkernel=X,high
714 is passed, kernel could allocate physical memory region
715 above 4G, that cause second kernel crash on system
716 that require some amount of low memory, e.g. swiotlb
717 requires at least 64M+32K low memory, also enough extra
718 low memory is needed to make sure DMA buffers for 32-bit
719 devices won't run out. Kernel would try to allocate at
720 at least 256M below 4G automatically.
721 This one let user to specify own low range under 4G
722 for second kernel instead.
723 0: to disable low allocation.
724 It will be ignored when crashkernel=X,high is not used
725 or memory reserved is below 4G.
728 [KNL] Disable crypto self-tests
733 cs89x0_media= [HW,NET]
734 Format: { rj45 | aui | bnc }
737 See header of drivers/s390/block/dasd_devmap.c.
739 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
740 (one device per port)
741 Format: <port#>,<type>
742 See also Documentation/input/devices/joystick-parport.rst
744 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
746 Documentation/admin-guide/dynamic-debug-howto.rst for
747 details. Deprecated, see dyndbg.
749 debug [KNL] Enable kernel debugging (events log level).
752 [KNL] Enable printing [hashed] pointers early in the
753 boot sequence. If enabled, we use a weak hash instead
754 of siphash to hash pointers. Use this option if you are
755 seeing instances of '(___ptrval___)') and need to see a
756 value (hashed pointer) instead. Cryptographically
757 insecure, please do not use on production kernels.
760 [KNL] verbose self-tests
762 Print debugging info while doing the locking API
764 We default to 0 (no extra messages), setting it to
765 1 will print _a lot_ more information - normally
766 only useful to kernel developers.
768 debug_objects [KNL] Enable object debugging
771 [KNL] Disable object debugging
773 debug_guardpage_minorder=
774 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
775 parameter allows control of the order of pages that will
776 be intentionally kept free (and hence protected) by the
777 buddy allocator. Bigger value increase the probability
778 of catching random memory corruption, but reduce the
779 amount of memory for normal system use. The maximum
780 possible value is MAX_ORDER/2. Setting this parameter
781 to 1 or 2 should be enough to identify most random
782 memory corruption problems caused by bugs in kernel or
783 driver code when a CPU writes to (or reads from) a
784 random memory location. Note that there exists a class
785 of memory corruptions problems caused by buggy H/W or
786 F/W or by drivers badly programing DMA (basically when
787 memory is written at bus level and the CPU MMU is
788 bypassed) which are not detectable by
789 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
790 tracking down these problems.
793 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
794 parameter enables the feature at boot time. In
795 default, it is disabled. We can avoid allocating huge
796 chunk of memory for debug pagealloc if we don't enable
797 it at boot time and the system will work mostly same
798 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
799 on: enable the feature
801 debugpat [X86] Enable PAT debugging
803 decnet.addr= [HW,NET]
804 Format: <area>[,<node>]
805 See also Documentation/networking/decnet.txt.
808 [same as hugepagesz=] The size of the default
809 HugeTLB page size. This is the size represented by
810 the legacy /proc/ hugepages APIs, used for SHM, and
811 default size when mounting hugetlbfs filesystems.
812 Defaults to the default architecture's huge page size
815 deferred_probe_timeout=
816 [KNL] Debugging option to set a timeout in seconds for
817 deferred probe to give up waiting on dependencies to
818 probe. Only specific dependencies (subsystems or
819 drivers) that have opted in will be ignored. A timeout of 0
820 will timeout at the end of initcalls. This option will also
821 dump out devices still on the deferred probe list after
825 Set number of hash buckets for dentry cache.
827 disable_1tb_segments [PPC]
828 Disables the use of 1TB hash page table segments. This
829 causes the kernel to fall back to 256MB segments which
830 can be useful when debugging issues that require an SLB
834 See Documentation/networking/ipv6.txt.
837 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
838 hardening is enabled for this boot. Hardened
839 usercopy checking is used to protect the kernel
840 from reading or writing beyond known memory
841 allocation boundaries as a proactive defense
842 against bounds-checking flaws in the kernel's
843 copy_to_user()/copy_from_user() interface.
844 on Perform hardened usercopy checks (default).
845 off Disable hardened usercopy checks.
848 Disable RADIX MMU mode on POWER9
850 disable_cpu_apicid= [X86,APIC,SMP]
852 The number of initial APIC ID for the
853 corresponding CPU to be disabled at boot,
854 mostly used for the kdump 2nd kernel to
855 disable BSP to wake up multiple CPUs without
856 causing system reset or hang due to sending
859 disable_ddw [PPC/PSERIES]
860 Disable Dynamic DMA Window support. Use this if
861 to workaround buggy firmware.
864 See Documentation/networking/ipv6.txt.
866 disable_mtrr_cleanup [X86]
867 The kernel tries to adjust MTRR layout from continuous
868 to discrete, to make X server driver able to add WB
869 entry later. This parameter disables that.
871 disable_mtrr_trim [X86, Intel and AMD only]
872 By default the kernel will trim any uncacheable
873 memory out of your available memory pool based on
874 MTRR settings. This parameter disables that behavior,
875 possibly causing your machine to run very slowly.
877 disable_timer_pin_1 [X86]
878 Disable PIN 1 of APIC timer
879 Can be useful to work around chipset bugs.
881 dis_ucode_ldr [X86] Disable the microcode loader.
883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
900 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
901 Broken monitors, graphic adapters, KVMs and EDIDless
902 panels may send no or incorrect EDID data sets.
903 This parameter allows to specify an EDID data sets
904 in the /lib/firmware directory that are used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
913 name. Each connector may use a unique EDID data
914 set by separating the files with a comma. An EDID
915 data set with no connector name will be used for
916 any connectors not explicitly specified.
921 Format: {"off" | "known"}
922 Control how the dt_cpu_ftrs device-tree binding is
923 used for CPU feature discovery and setup (if it
925 off: Do not use it, fall back to legacy cpu table.
926 known: Do not pass through unknown features to guests
927 or userspace, only those that the kernel is aware of.
929 dump_apple_properties [X86]
930 Dump name and content of EFI device properties on
931 x86 Macs. Useful for driver authors to determine
932 what data is available or for reverse-engineering.
934 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
935 module.dyndbg[="val"]
936 Enable debug messages at boot time. See
937 Documentation/admin-guide/dynamic-debug-howto.rst
940 nompx [X86] Disables Intel Memory Protection Extensions.
941 See Documentation/x86/intel_mpx.txt for more
942 information about the feature.
944 nopku [X86] Disable Memory Protection Keys CPU feature found
947 module.async_probe [KNL]
948 Enable asynchronous probe on this module.
950 early_ioremap_debug [KNL]
951 Enable debug messages in early_ioremap support. This
952 is useful for tracking down temporary early mappings
953 which are not unmapped.
955 earlycon= [KNL] Output early console device and options.
957 [ARM64] The early console is determined by the
958 stdout-path property in device tree's chosen node,
959 or determined by the ACPI SPCR table.
961 [X86] When used with no options the early console is
962 determined by the ACPI SPCR table.
964 cdns,<addr>[,options]
965 Start an early, polled-mode console on a Cadence
966 (xuartps) serial port at the specified address. Only
967 supported option is baud rate. If baud rate is not
968 specified, the serial port must already be setup and
971 uart[8250],io,<addr>[,options]
972 uart[8250],mmio,<addr>[,options]
973 uart[8250],mmio32,<addr>[,options]
974 uart[8250],mmio32be,<addr>[,options]
975 uart[8250],0x<addr>[,options]
976 Start an early, polled-mode console on the 8250/16550
977 UART at the specified I/O port or MMIO address.
978 MMIO inter-register address stride is either 8-bit
979 (mmio) or 32-bit (mmio32 or mmio32be).
980 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
981 to be equivalent to 'mmio'. 'options' are specified
982 in the same format described for "console=ttyS<n>"; if
983 unspecified, the h/w is not initialized.
987 Start an early, polled-mode console on a pl011 serial
988 port at the specified address. The pl011 serial port
989 must already be setup and configured. Options are not
990 yet supported. If 'mmio32' is specified, then only
991 the driver will use only 32-bit accessors to read/write
992 the device registers.
995 Start an early, polled-mode console on a meson serial
996 port at the specified address. The serial port must
997 already be setup and configured. Options are not yet
1001 Start an early, polled-mode console on an msm serial
1002 port at the specified address. The serial port
1003 must already be setup and configured. Options are not
1006 msm_serial_dm,<addr>
1007 Start an early, polled-mode console on an msm serial
1008 dm port at the specified address. The serial port
1009 must already be setup and configured. Options are not
1013 Start an early, polled-mode console on a serial port
1014 of an Actions Semi SoC, such as S500 or S900, at the
1015 specified address. The serial port must already be
1016 setup and configured. Options are not yet supported.
1018 smh Use ARM semihosting calls for early console.
1026 Use early console provided by serial driver available
1027 on Samsung SoCs, requires selecting proper type and
1028 a correct base address of the selected UART port. The
1029 serial port must already be setup and configured.
1030 Options are not yet supported.
1033 Start an early, polled-mode console on a lantiq serial
1034 (lqasc) port at the specified address. The serial port
1035 must already be setup and configured. Options are not
1040 Use early console provided by Freescale LP UART driver
1041 found on Freescale Vybrid and QorIQ LS1021A processors.
1042 A valid base address must be provided, and the serial
1043 port must already be setup and configured.
1046 Start an early, polled-mode console on the
1047 Armada 3700 serial port at the specified
1048 address. The serial port must already be setup
1049 and configured. Options are not yet supported.
1052 Start an early, polled-mode console on a Qualcomm
1053 Generic Interface (GENI) based serial port at the
1054 specified address. The serial port must already be
1055 setup and configured. Options are not yet supported.
1057 earlyprintk= [X86,SH,ARM,M68k,S390]
1062 earlyprintk=serial[,ttySn[,baudrate]]
1063 earlyprintk=serial[,0x...[,baudrate]]
1064 earlyprintk=ttySn[,baudrate]
1065 earlyprintk=dbgp[debugController#]
1066 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1067 earlyprintk=xdbc[xhciController#]
1069 earlyprintk is useful when the kernel crashes before
1070 the normal console is initialized. It is not enabled by
1071 default because it has some cosmetic problems.
1073 Append ",keep" to not disable it when the real console
1076 Only one of vga, efi, serial, or usb debug port can
1079 Currently only ttyS0 and ttyS1 may be specified by
1080 name. Other I/O ports may be explicitly specified
1081 on some architectures (x86 and arm at least) by
1082 replacing ttySn with an I/O port address, like this:
1083 earlyprintk=serial,0x1008,115200
1084 You can find the port for a given device in
1085 /proc/tty/driver/serial:
1086 2: uart:ST16650V2 port:00001008 irq:18 ...
1088 Interaction with the standard serial driver is not
1091 The VGA and EFI output is eventually overwritten by
1094 The xen output can only be used by Xen PV guests.
1096 The sclp output can only be used on s390.
1098 The optional "force" to "pciserial" enables use of a
1099 PCI device even when its classcode is not of the
1102 edac_report= [HW,EDAC] Control how to report EDAC event
1103 Format: {"on" | "off" | "force"}
1104 on: enable EDAC to report H/W event. May be overridden
1105 by other higher priority error reporting module.
1106 off: disable H/W event reporting through EDAC.
1107 force: enforce the use of EDAC to report H/W event.
1110 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1113 This is designed to be used in conjunction with
1114 the boot argument: earlyprintk=vga
1117 Format: {"off" | "on" | "skip[mbr]"}
1120 Format: { "old_map", "nochunk", "noruntime", "debug" }
1121 old_map [X86-64]: switch to the old ioremap-based EFI
1122 runtime services mapping. 32-bit still uses this one by
1124 nochunk: disable reading files in "chunks" in the EFI
1125 boot stub, as chunking can cause problems with some
1126 firmware implementations.
1127 noruntime : disable EFI runtime services support
1128 debug: enable misc debug output
1130 efi_no_storage_paranoia [EFI; X86]
1131 Using this parameter you can use more than 50% of
1132 your efi variable storage. Use this parameter only if
1133 you are really sure that your UEFI does sane gc and
1134 fulfills the spec otherwise your board may brick.
1136 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1137 Add arbitrary attribute to specific memory range by
1138 updating original EFI memory map.
1139 Region of memory which aa attribute is added to is
1141 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1142 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1143 attribute is added to range 0x100000000-0x180000000 and
1144 0x10a0000000-0x1120000000.
1146 Using this parameter you can do debugging of EFI memmap
1147 related feature. For example, you can do debugging of
1148 Address Range Mirroring feature even if your box
1151 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1152 that is to be dynamically loaded by Linux. If there are
1153 multiple variables with the same name but with different
1154 vendor GUIDs, all of them will be loaded. See
1155 Documentation/acpi/ssdt-overlays.txt for details.
1158 eisa_irq_edge= [PARISC,HW]
1159 See header of drivers/parisc/eisa.c.
1162 See comment before function elanfreq_setup() in
1163 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1166 Format: {"cfq" | "deadline" | "noop"}
1167 See Documentation/block/cfq-iosched.txt and
1168 Documentation/block/deadline-iosched.txt for details.
1170 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1171 Specifies physical address of start of kernel core
1172 image elf header and optionally the size. Generally
1173 kexec loader will pass this option to capture kernel.
1174 See Documentation/kdump/kdump.txt for details.
1176 enable_mtrr_cleanup [X86]
1177 The kernel tries to adjust MTRR layout from continuous
1178 to discrete, to make X server driver able to add WB
1179 entry later. This parameter enables that.
1181 enable_timer_pin_1 [X86]
1182 Enable PIN 1 of APIC timer
1183 Can be useful to work around chipset bugs
1184 (in particular on some ATI chipsets).
1185 The kernel tries to set a reasonable default.
1187 enforcing [SELINUX] Set initial enforcing status.
1189 See security/selinux/Kconfig help text.
1190 0 -- permissive (log only, no denials).
1191 1 -- enforcing (deny and log).
1193 Value can be changed at runtime via /selinux/enforce.
1196 Disable Error Record Serialization Table (ERST)
1199 ether= [HW,NET] Ethernet cards parameters
1200 This option is obsoleted by the "netdev=" option, which
1201 has equivalent usage. See its documentation for details.
1205 Permit 'security.evm' to be updated regardless of
1206 current integrity status.
1210 fail_make_request=[KNL]
1211 General fault injection mechanism.
1212 Format: <interval>,<probability>,<space>,<times>
1213 See also Documentation/fault-injection/.
1216 See Documentation/blockdev/floppy.txt.
1218 force_pal_cache_flush
1219 [IA-64] Avoid check_sal_cache_flush which may hang on
1220 buggy SAL_CACHE_FLUSH implementations. Using this
1221 parameter will force ia64_sal_cache_flush to call
1222 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1225 Forcefully enable Physical Address Extension (PAE).
1226 Many Pentium M systems disable PAE but may have a
1227 functionally usable PAE implementation.
1228 Warning: use of this parameter will taint the kernel
1229 and may cause unknown problems.
1232 [FTRACE] will set and start the specified tracer
1233 as early as possible in order to facilitate early
1236 ftrace_dump_on_oops[=orig_cpu]
1237 [FTRACE] will dump the trace buffers on oops.
1238 If no parameter is passed, ftrace will dump
1239 buffers of all CPUs, but if you pass orig_cpu, it will
1240 dump only the buffer of the CPU that triggered the
1243 ftrace_filter=[function-list]
1244 [FTRACE] Limit the functions traced by the function
1245 tracer at boot up. function-list is a comma separated
1246 list of functions. This list can be changed at run
1247 time by the set_ftrace_filter file in the debugfs
1250 ftrace_notrace=[function-list]
1251 [FTRACE] Do not trace the functions specified in
1252 function-list. This list can be changed at run time
1253 by the set_ftrace_notrace file in the debugfs
1256 ftrace_graph_filter=[function-list]
1257 [FTRACE] Limit the top level callers functions traced
1258 by the function graph tracer at boot up.
1259 function-list is a comma separated list of functions
1260 that can be changed at run time by the
1261 set_graph_function file in the debugfs tracing directory.
1263 ftrace_graph_notrace=[function-list]
1264 [FTRACE] Do not trace from the functions specified in
1265 function-list. This list is a comma separated list of
1266 functions that can be changed at run time by the
1267 set_graph_notrace file in the debugfs tracing directory.
1269 ftrace_graph_max_depth=<uint>
1270 [FTRACE] Used with the function graph tracer. This is
1271 the max depth it will trace into a function. This value
1272 can be changed at run time by the max_graph_depth file
1273 in the tracefs tracing directory. default: 0 (no limit)
1276 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1277 support via parallel port (up to 5 devices per port)
1278 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1279 See also Documentation/input/devices/joystick-parport.rst
1283 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1287 gcov_persist= [GCOV] When non-zero (default), profiling data for
1288 kernel modules is saved and remains accessible via
1289 debugfs, even when the module is unloaded/reloaded.
1290 When zero, profiling data is discarded and associated
1291 debugfs files are removed at module unload time.
1293 goldfish [X86] Enable the goldfish android emulator platform.
1294 Don't use this when you are not running on the
1297 gpt [EFI] Forces disk with valid GPT signature but
1298 invalid Protective MBR to be treated as GPT. If the
1299 primary GPT is corrupted, it enables the backup/alternate
1300 GPT to be used instead.
1302 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1303 the "Enable 0" bit of the configuration register.
1306 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1307 the "Enable 0" bit of the configuration register.
1310 grcan.select= [HW] Select which physical interface to use.
1313 grcan.txsize= [HW] Sets the size of the tx buffer.
1314 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1316 grcan.rxsize= [HW] Sets the size of the rx buffer.
1317 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1320 gpio-mockup.gpio_mockup_ranges
1321 [HW] Sets the ranges of gpiochip of for this device.
1322 Format: <start1>,<end1>,<start2>,<end2>...
1324 hardlockup_all_cpu_backtrace=
1325 [KNL] Should the hard-lockup detector generate
1326 backtraces on all cpus.
1329 hashdist= [KNL,NUMA] Large hashes allocated during boot
1330 are distributed across NUMA nodes. Defaults on
1331 for 64-bit NUMA, off otherwise.
1332 Format: 0 | 1 (for off | on)
1334 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1336 hd= [EIDE] (E)IDE hard drive subsystem geometry
1337 Format: <cyl>,<head>,<sect>
1340 Disable Hardware Error Source Table (HEST) support;
1341 corresponding firmware-first mode error processing
1342 logic will be disabled.
1344 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1345 size of <nn>. This works even on boxes that have no
1346 highmem otherwise. This also works to reduce highmem
1347 size on bigger boxes.
1349 highres= [KNL] Enable/disable high resolution timer mode.
1350 Valid parameters: "on", "off"
1354 See Documentation/isdn/README.HiSax.
1358 hpet= [X86-32,HPET] option to control HPET usage
1359 Format: { enable (default) | disable | force |
1361 disable: disable HPET and use PIT instead
1362 force: allow force enabled of undocumented chips (ICH4,
1364 verbose: show contents of HPET registers during setup
1366 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1367 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1369 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1370 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1371 On x86-64 and powerpc, this option can be specified
1372 multiple times interleaved with hugepages= to reserve
1373 huge pages of different sizes. Valid pages sizes on
1374 x86-64 are 2M (when the CPU supports "pse") and 1G
1375 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1378 [KNL] Should the hung task detector generate panics.
1381 A nonzero value instructs the kernel to panic when a
1382 hung task is detected. The default value is controlled
1383 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1384 option. The value selected by this boot parameter can
1385 be changed later by the kernel.hung_task_panic sysctl.
1387 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1388 terminal devices. Valid values: 0..8
1389 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1390 If specified, z/VM IUCV HVC accepts connections
1391 from listed z/VM user IDs only.
1393 Do not unregister boot console at start. This is only
1394 useful for debugging when something happens in the window
1395 between unregistering the boot console and initializing
1398 i2c_bus= [HW] Override the default board specific I2C bus speed
1399 or register an additional I2C bus that is not
1400 registered from board initialization code.
1404 i8042.debug [HW] Toggle i8042 debug mode
1405 i8042.unmask_kbd_data
1406 [HW] Enable printing of interrupt data from the KBD port
1407 (disabled by default, and as a pre-condition
1408 requires that i8042.debug=1 be enabled)
1409 i8042.direct [HW] Put keyboard port into non-translated mode
1410 i8042.dumbkbd [HW] Pretend that controller can only read data from
1411 keyboard and cannot control its state
1412 (Don't attempt to blink the leds)
1413 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1414 i8042.nokbd [HW] Don't check/create keyboard port
1415 i8042.noloop [HW] Disable the AUX Loopback command while probing
1417 i8042.nomux [HW] Don't check presence of an active multiplexing
1419 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1421 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1422 i8042.reset [HW] Reset the controller during init, cleanup and
1423 suspend-to-ram transitions, only during s2r
1424 transitions, or never reset
1425 Format: { 1 | Y | y | 0 | N | n }
1426 1, Y, y: always reset controller
1427 0, N, n: don't ever reset controller
1428 Default: only on s2r transitions on x86; most other
1429 architectures force reset to be always executed
1430 i8042.unlock [HW] Unlock (ignore) the keylock
1431 i8042.kbdreset [HW] Reset device connected to KBD port
1435 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1436 indicates that the driver is running on unsupported
1438 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1439 does not match list of supported models.
1441 [HW] Report power status in /proc/i8k
1442 (disabled by default)
1443 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1446 i915.invert_brightness=
1447 [DRM] Invert the sense of the variable that is used to
1448 set the brightness of the panel backlight. Normally a
1449 brightness value of 0 indicates backlight switched off,
1450 and the maximum of the brightness value sets the backlight
1451 to maximum brightness. If this parameter is set to 0
1452 (default) and the machine requires it, or this parameter
1453 is set to 1, a brightness value of 0 sets the backlight
1454 to maximum brightness, and the maximum of the brightness
1455 value switches the backlight off.
1456 -1 -- never invert brightness
1457 0 -- machine default
1458 1 -- force brightness inversion
1461 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1463 ide-core.nodma= [HW] (E)IDE subsystem
1464 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1465 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1466 .cdrom .chs .ignore_cable are additional options
1467 See Documentation/ide/ide.txt.
1469 ide-generic.probe-mask= [HW] (E)IDE subsystem
1471 Probe mask for legacy ISA IDE ports. Depending on
1472 platform up to 6 ports are supported, enabled by
1473 setting corresponding bits in the mask to 1. The
1474 default value is 0x0, which has a special meaning.
1475 On systems that have PCI, it triggers scanning the
1476 PCI bus for the first and the second port, which
1477 are then probed. On systems without PCI the value
1478 of 0x0 enables probing the two first ports as if it
1481 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1482 Claim all unknown PCI IDE storage controllers.
1485 Format: idle=poll, idle=halt, idle=nomwait
1486 Poll forces a polling idle loop that can slightly
1487 improve the performance of waking up a idle CPU, but
1488 will use a lot of power and make the system run hot.
1490 idle=halt: Halt is forced to be used for CPU idle.
1491 In such case C2/C3 won't be used again.
1492 idle=nomwait: Disable mwait for CPU C-states
1494 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1495 Format: { strict | legacy | 2008 | relaxed }
1498 Choose which programs will be accepted for execution
1499 based on the IEEE 754 NaN encoding(s) supported by
1500 the FPU and the NaN encoding requested with the value
1501 of an ELF file header flag individually set by each
1502 binary. Hardware implementations are permitted to
1503 support either or both of the legacy and the 2008 NaN
1506 Available settings are as follows:
1507 strict accept binaries that request a NaN encoding
1508 supported by the FPU
1509 legacy only accept legacy-NaN binaries, if supported
1511 2008 only accept 2008-NaN binaries, if supported
1513 relaxed accept any binaries regardless of whether
1514 supported by the FPU
1516 The FPU emulator is always able to support both NaN
1517 encodings, so if no FPU hardware is present or it has
1518 been disabled with 'nofpu', then the settings of
1519 'legacy' and '2008' strap the emulator accordingly,
1520 'relaxed' straps the emulator for both legacy-NaN and
1521 2008-NaN, whereas 'strict' enables legacy-NaN only on
1522 legacy processors and both NaN encodings on MIPS32 or
1525 The setting for ABS.fmt/NEG.fmt instruction execution
1526 mode generally follows that for the NaN encoding,
1527 except where unsupported by hardware.
1529 ignore_loglevel [KNL]
1530 Ignore loglevel setting - this will print /all/
1531 kernel messages to the console. Useful for debugging.
1532 We also add it as printk module parameter, so users
1533 could change it dynamically, usually by
1534 /sys/module/printk/parameters/ignore_loglevel.
1537 Ignore RLIMIT_DATA setting for data mappings,
1538 print warning at first misuse. Can be changed via
1539 /sys/module/kernel/parameters/ignore_rlimit_data.
1541 ihash_entries= [KNL]
1542 Set number of hash buckets for inode cache.
1544 ima_appraise= [IMA] appraise integrity measurements
1545 Format: { "off" | "enforce" | "fix" | "log" }
1548 ima_appraise_tcb [IMA]
1549 The builtin appraise policy appraises all files
1552 ima_canonical_fmt [IMA]
1553 Use the canonical format for the binary runtime
1554 measurements, instead of host native format.
1557 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1561 The list of supported hash algorithms is defined
1562 in crypto/hash_info.h.
1565 The builtin policies to load during IMA setup.
1566 Format: "tcb | appraise_tcb | secure_boot |
1569 The "tcb" policy measures all programs exec'd, files
1570 mmap'd for exec, and all files opened with the read
1571 mode bit set by either the effective uid (euid=0) or
1574 The "appraise_tcb" policy appraises the integrity of
1575 all files owned by root. (This is the equivalent
1576 of ima_appraise_tcb.)
1578 The "secure_boot" policy appraises the integrity
1579 of files (eg. kexec kernel image, kernel modules,
1580 firmware, policy, etc) based on file signatures.
1582 The "fail_securely" policy forces file signature
1583 verification failure also on privileged mounted
1584 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1587 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1588 Load a policy which meets the needs of the Trusted
1589 Computing Base. This means IMA will measure all
1590 programs exec'd, files mmap'd for exec, and all files
1591 opened for read by uid=0.
1594 Select one of defined IMA measurements template formats.
1595 Formats: { "ima" | "ima-ng" | "ima-sig" }
1599 [IMA] Define a custom template format.
1600 Format: { "field1|...|fieldN" }
1602 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1603 Format: <min_file_size>
1604 Set the minimal file size for using asynchronous hash.
1605 If left unspecified, ahash usage is disabled.
1607 ahash performance varies for different data sizes on
1608 different crypto accelerators. This option can be used
1609 to achieve the best performance for a particular HW.
1611 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1613 Set hashing buffer size. Default: 4k.
1615 ahash performance varies for different chunk sizes on
1616 different crypto accelerators. This option can be used
1617 to achieve best performance for particular HW.
1621 Run specified binary instead of /sbin/init as init
1624 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1625 for working out where the kernel is dying during
1628 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1629 initcall functions. Useful for debugging built-in
1630 modules and initcalls.
1632 initrd= [BOOT] Specify the location of the initial ramdisk
1634 init_pkru= [x86] Specify the default memory protection keys rights
1635 register contents for all processes. 0x55555554 by
1636 default (disallow access to all but pkey 0). Can
1637 override in debugfs after boot.
1639 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1642 int_pln_enable [x86] Enable power limit notification interrupt
1644 integrity_audit=[IMA]
1645 Format: { "0" | "1" }
1646 0 -- basic integrity auditing messages. (Default)
1647 1 -- additional integrity auditing messages.
1649 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1651 Enable intel iommu driver.
1653 Disable intel iommu driver.
1654 igfx_off [Default Off]
1655 By default, gfx is mapped as normal device. If a gfx
1656 device has a dedicated DMAR unit, the DMAR unit is
1657 bypassed by not enabling DMAR with this option. In
1658 this case, gfx device will use physical address for
1661 With this option iommu will not optimize to look
1662 for io virtual address below 32-bit forcing dual
1663 address cycle on pci bus for cards supporting greater
1664 than 32-bit addressing. The default is to look
1665 for translation below 32-bit and if not available
1666 then look in the higher range.
1667 strict [Default Off]
1668 With this option on every unmap_single operation will
1669 result in a hardware IOTLB flush operation as opposed
1670 to batching them for performance.
1671 sp_off [Default Off]
1672 By default, super page will be supported if Intel IOMMU
1673 has the capability. With this option, super page will
1675 ecs_off [Default Off]
1676 By default, extended context tables will be supported if
1677 the hardware advertises that it has support both for the
1678 extended tables themselves, and also PASID support. With
1679 this option set, extended tables will not be used even
1680 on hardware which claims to support them.
1681 tboot_noforce [Default Off]
1682 Do not force the Intel IOMMU enabled under tboot.
1683 By default, tboot will force Intel IOMMU on, which
1684 could harm performance of some high-throughput
1685 devices like 40GBit network cards, even if identity
1687 Note that using this option lowers the security
1688 provided by tboot because it makes the system
1689 vulnerable to DMA attacks.
1691 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1692 0 disables intel_idle and fall back on acpi_idle.
1693 1 to 9 specify maximum depth of C-state.
1697 Do not enable intel_pstate as the default
1698 scaling driver for the supported processors
1700 Use intel_pstate as a scaling driver, but configure it
1701 to work with generic cpufreq governors (instead of
1702 enabling its internal governor). This mode cannot be
1703 used along with the hardware-managed P-states (HWP)
1706 Enable intel_pstate on systems that prohibit it by default
1707 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1708 instead of acpi-cpufreq may disable platform features, such
1709 as thermal controls and power capping, that rely on ACPI
1710 P-States information being indicated to OSPM and therefore
1711 should be used with caution. This option does not work with
1712 processors that aren't supported by the intel_pstate driver
1713 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1715 Do not enable hardware P state control (HWP)
1718 Only load intel_pstate on systems which support
1719 hardware P state control (HWP) if available.
1721 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1722 Description Table, specifies preferred power management
1723 profile as "Enterprise Server" or "Performance Server",
1724 then this feature is turned on by default.
1726 Allow per-logical-CPU P-State performance control limits using
1727 cpufreq sysfs interface
1729 intremap= [X86-64, Intel-IOMMU]
1730 on enable Interrupt Remapping (default)
1731 off disable Interrupt Remapping
1732 nosid disable Source ID checking
1734 BIOS x2APIC opt-out request will be ignored
1735 nopost disable Interrupt Posting
1737 iomem= Disable strict checking of access to MMIO memory
1738 strict regions from userspace.
1753 nobypass [PPC/POWERNV]
1754 Disable IOMMU bypass, using IOMMU for PCI devices.
1757 [ARM64] Configure DMA to bypass the IOMMU by default.
1758 Format: { "0" | "1" }
1759 0 - Use IOMMU translation for DMA.
1760 1 - Bypass the IOMMU for DMA.
1761 unset - Use IOMMU translation for DMA.
1763 io7= [HW] IO7 for Marvel based alpha systems
1764 See comment before marvel_specify_io7 in
1765 arch/alpha/kernel/core_marvel.c.
1767 io_delay= [X86] I/O delay method
1769 Standard port 0x80 based delay
1771 Alternate port 0xed based delay (needed on some systems)
1773 Simple two microseconds delay
1778 See Documentation/filesystems/nfs/nfsroot.txt.
1780 irqaffinity= [SMP] Set the default irq affinity mask
1781 The argument is a cpu list, as described above.
1783 irqchip.gicv2_force_probe=
1786 Force the kernel to look for the second 4kB page
1787 of a GICv2 controller even if the memory range
1788 exposed by the device tree is too small.
1790 irqchip.gicv3_nolpi=
1792 Force the kernel to ignore the availability of
1793 LPIs (and by consequence ITSs). Intended for system
1794 that use the kernel as a bootloader, and thus want
1795 to let secondary kernels in charge of setting up
1799 When an interrupt is not handled search all handlers
1800 for it. Intended to get systems with badly broken
1804 When an interrupt is not handled search all handlers
1805 for it. Also check all handlers each timer
1806 interrupt. Intended to get systems with badly broken
1810 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1812 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1813 [Deprecated - use cpusets instead]
1814 Format: [flag-list,]<cpu-list>
1816 Specify one or more CPUs to isolate from disturbances
1817 specified in the flag list (default: domain):
1820 Disable the tick when a single task runs.
1822 A residual 1Hz tick is offloaded to workqueues, which you
1823 need to affine to housekeeping through the global
1824 workqueue's affinity configured via the
1825 /sys/devices/virtual/workqueue/cpumask sysfs file, or
1826 by using the 'domain' flag described below.
1828 NOTE: by default the global workqueue runs on all CPUs,
1829 so to protect individual CPUs the 'cpumask' file has to
1830 be configured manually after bootup.
1833 Isolate from the general SMP balancing and scheduling
1834 algorithms. Note that performing domain isolation this way
1835 is irreversible: it's not possible to bring back a CPU to
1836 the domains once isolated through isolcpus. It's strongly
1837 advised to use cpusets instead to disable scheduler load
1838 balancing through the "cpuset.sched_load_balance" file.
1839 It offers a much more flexible interface where CPUs can
1840 move in and out of an isolated set anytime.
1842 You can move a process onto or off an "isolated" CPU via
1843 the CPU affinity syscalls or cpuset.
1844 <cpu number> begins at 0 and the maximum value is
1845 "number of CPUs in system - 1".
1847 The format of <cpu-list> is described above.
1853 ivrs_ioapic [HW,X86_64]
1854 Provide an override to the IOAPIC-ID<->DEVICE-ID
1855 mapping provided in the IVRS ACPI table. For
1856 example, to map IOAPIC-ID decimal 10 to
1857 PCI device 00:14.0 write the parameter as:
1858 ivrs_ioapic[10]=00:14.0
1860 ivrs_hpet [HW,X86_64]
1861 Provide an override to the HPET-ID<->DEVICE-ID
1862 mapping provided in the IVRS ACPI table. For
1863 example, to map HPET-ID decimal 0 to
1864 PCI device 00:14.0 write the parameter as:
1865 ivrs_hpet[0]=00:14.0
1867 ivrs_acpihid [HW,X86_64]
1868 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1869 mapping provided in the IVRS ACPI table. For
1870 example, to map UART-HID:UID AMD0020:0 to
1871 PCI device 00:14.5 write the parameter as:
1872 ivrs_acpihid[00:14.5]=AMD0020:0
1874 js= [HW,JOY] Analog joystick
1875 See Documentation/input/joydev/joystick.rst.
1878 When CONFIG_RANDOMIZE_BASE is set, this disables
1879 kernel and module base offset ASLR (Address Space
1880 Layout Randomization).
1883 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1884 report on every invalid memory access. Without this
1885 parameter KASAN will print report only for the first
1890 kernelcore= [KNL,X86,IA-64,PPC]
1891 Format: nn[KMGTPE] | nn% | "mirror"
1892 This parameter specifies the amount of memory usable by
1893 the kernel for non-movable allocations. The requested
1894 amount is spread evenly throughout all nodes in the
1895 system as ZONE_NORMAL. The remaining memory is used for
1896 movable memory in its own zone, ZONE_MOVABLE. In the
1897 event, a node is too small to have both ZONE_NORMAL and
1898 ZONE_MOVABLE, kernelcore memory will take priority and
1899 other nodes will have a larger ZONE_MOVABLE.
1901 ZONE_MOVABLE is used for the allocation of pages that
1902 may be reclaimed or moved by the page migration
1903 subsystem. Note that allocations like PTEs-from-HighMem
1904 still use the HighMem zone if it exists, and the Normal
1905 zone if it does not.
1907 It is possible to specify the exact amount of memory in
1908 the form of "nn[KMGTPE]", a percentage of total system
1909 memory in the form of "nn%", or "mirror". If "mirror"
1910 option is specified, mirrored (reliable) memory is used
1911 for non-movable allocations and remaining memory is used
1912 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
1913 are exclusive, so you cannot specify multiple forms.
1915 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1916 Format: <Controller#>[,poll interval]
1917 The controller # is the number of the ehci usb debug
1918 port as it is probed via PCI. The poll interval is
1919 optional and is the number seconds in between
1920 each poll cycle to the debug port in case you need
1921 the functionality for interrupting the kernel with
1922 gdb or control-c on the dbgp connection. When
1923 not using this parameter you use sysrq-g to break into
1924 the kernel debugger.
1926 kgdboc= [KGDB,HW] kgdb over consoles.
1927 Requires a tty driver that supports console polling,
1928 or a supported polling keyboard driver (non-usb).
1929 Serial only format: <serial_device>[,baud]
1930 keyboard only format: kbd
1931 keyboard and serial format: kbd,<serial_device>[,baud]
1932 Optional Kernel mode setting:
1933 kms, kbd format: kms,kbd
1934 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1936 kgdbwait [KGDB] Stop kernel execution and enter the
1937 kernel debugger at the earliest opportunity.
1939 kmac= [MIPS] korina ethernet MAC address.
1940 Configure the RouterBoard 532 series on-chip
1941 Ethernet adapter MAC address.
1943 kmemleak= [KNL] Boot-time kmemleak enable/disable
1944 Valid arguments: on, off
1946 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1949 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1950 Default is 0 (don't ignore, but inject #GP)
1952 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
1953 Default is false (don't support).
1955 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1959 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1960 Default is 1 (enabled)
1962 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1964 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1966 kvm-arm.vgic_v3_group0_trap=
1967 [KVM,ARM] Trap guest accesses to GICv3 group-0
1970 kvm-arm.vgic_v3_group1_trap=
1971 [KVM,ARM] Trap guest accesses to GICv3 group-1
1974 kvm-arm.vgic_v3_common_trap=
1975 [KVM,ARM] Trap guest accesses to GICv3 common
1978 kvm-arm.vgic_v4_enable=
1979 [KVM,ARM] Allow use of GICv4 for direct injection of
1982 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1983 (virtualized MMU) support on capable Intel chips.
1984 Default is 1 (enabled)
1986 kvm-intel.emulate_invalid_guest_state=
1987 [KVM,Intel] Enable emulation of invalid guest states
1988 Default is 0 (disabled)
1990 kvm-intel.flexpriority=
1991 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1992 Default is 1 (enabled)
1995 [KVM,Intel] Enable VMX nesting (nVMX).
1996 Default is 0 (disabled)
1998 kvm-intel.unrestricted_guest=
1999 [KVM,Intel] Disable unrestricted guest feature
2000 (virtualized real and unpaged mode) on capable
2001 Intel chips. Default is 1 (enabled)
2003 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2006 Valid arguments: never, cond, always
2008 always: L1D cache flush on every VMENTER.
2009 cond: Flush L1D on VMENTER only when the code between
2010 VMEXIT and VMENTER can leak host memory.
2011 never: Disables the mitigation
2013 Default is cond (do L1 cache flush in specific instances)
2015 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2016 feature (tagged TLBs) on capable Intel chips.
2017 Default is 1 (enabled)
2019 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2022 The kernel PTE inversion protection is unconditionally
2023 enabled and cannot be disabled.
2026 Provides all available mitigations for the
2027 L1TF vulnerability. Disables SMT and
2028 enables all mitigations in the
2029 hypervisors, i.e. unconditional L1D flush.
2031 SMT control and L1D flush control via the
2032 sysfs interface is still possible after
2033 boot. Hypervisors will issue a warning
2034 when the first VM is started in a
2035 potentially insecure configuration,
2036 i.e. SMT enabled or L1D flush disabled.
2039 Same as 'full', but disables SMT and L1D
2040 flush runtime control. Implies the
2041 'nosmt=force' command line option.
2042 (i.e. sysfs control of SMT is disabled.)
2045 Leaves SMT enabled and enables the default
2046 hypervisor mitigation, i.e. conditional
2049 SMT control and L1D flush control via the
2050 sysfs interface is still possible after
2051 boot. Hypervisors will issue a warning
2052 when the first VM is started in a
2053 potentially insecure configuration,
2054 i.e. SMT enabled or L1D flush disabled.
2058 Disables SMT and enables the default
2059 hypervisor mitigation.
2061 SMT control and L1D flush control via the
2062 sysfs interface is still possible after
2063 boot. Hypervisors will issue a warning
2064 when the first VM is started in a
2065 potentially insecure configuration,
2066 i.e. SMT enabled or L1D flush disabled.
2069 Same as 'flush', but hypervisors will not
2070 warn when a VM is started in a potentially
2071 insecure configuration.
2074 Disables hypervisor mitigations and doesn't
2076 It also drops the swap size and available
2077 RAM limit restriction on both hypervisor and
2082 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2088 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2091 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2092 value for LAPIC timer one-shot implementation. Default
2093 back to the programmable timer unit in the LAPIC.
2095 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2098 libata.dma= [LIBATA] DMA control
2099 libata.dma=0 Disable all PATA and SATA DMA
2100 libata.dma=1 PATA and SATA Disk DMA only
2101 libata.dma=2 ATAPI (CDROM) DMA only
2102 libata.dma=4 Compact Flash DMA only
2103 Combinations also work, so libata.dma=3 enables DMA
2104 for disks and CDROMs, but not CFs.
2106 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2107 libata.ignore_hpa=0 keep BIOS limits (default)
2108 libata.ignore_hpa=1 ignore limits, using full disk
2110 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2114 libata.force= [LIBATA] Force configurations. The format is comma
2115 separated list of "[ID:]VAL" where ID is
2116 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2117 matching port, link or device. Basically, it matches
2118 the ATA ID string printed on console by libata. If
2119 the whole ID part is omitted, the last PORT and DEVICE
2120 values are used. If ID hasn't been specified yet, the
2121 configuration applies to all ports, links and devices.
2123 If only DEVICE is omitted, the parameter applies to
2124 the port and all links and devices behind it. DEVICE
2125 number of 0 either selects the first device or the
2126 first fan-out link behind PMP device. It does not
2127 select the host link. DEVICE number of 15 selects the
2128 host link and device attached to it.
2130 The VAL specifies the configuration to force. As long
2131 as there's no ambiguity shortcut notation is allowed.
2132 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2133 The following configurations can be forced.
2135 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2136 Any ID with matching PORT is used.
2138 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2140 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2141 udma[/][16,25,33,44,66,100,133] notation is also
2144 * [no]ncq: Turn on or off NCQ.
2146 * [no]ncqtrim: Turn off queued DSM TRIM.
2148 * nohrst, nosrst, norst: suppress hard, soft
2151 * rstonce: only attempt one reset during
2152 hot-unplug link recovery
2154 * dump_id: dump IDENTIFY data.
2156 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2158 * disable: Disable this device.
2160 If there are multiple matching configurations changing
2161 the same attribute, the last one is used.
2163 memblock=debug [KNL] Enable memblock debug messages.
2165 load_ramdisk= [RAM] List of ramdisks to load from floppy
2166 See Documentation/blockdev/ramdisk.txt.
2168 lockd.nlm_grace_period=P [NFS] Assign grace period.
2171 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2174 lockd.nlm_timeout=T [NFS] Assign timeout value.
2177 lockd.nlm_udpport=M [NFS] Assign UDP port.
2180 locktorture.nreaders_stress= [KNL]
2181 Set the number of locking read-acquisition kthreads.
2182 Defaults to being automatically set based on the
2183 number of online CPUs.
2185 locktorture.nwriters_stress= [KNL]
2186 Set the number of locking write-acquisition kthreads.
2188 locktorture.onoff_holdoff= [KNL]
2189 Set time (s) after boot for CPU-hotplug testing.
2191 locktorture.onoff_interval= [KNL]
2192 Set time (s) between CPU-hotplug operations, or
2193 zero to disable CPU-hotplug testing.
2195 locktorture.shuffle_interval= [KNL]
2196 Set task-shuffle interval (jiffies). Shuffling
2197 tasks allows some CPUs to go into dyntick-idle
2198 mode during the locktorture test.
2200 locktorture.shutdown_secs= [KNL]
2201 Set time (s) after boot system shutdown. This
2202 is useful for hands-off automated testing.
2204 locktorture.stat_interval= [KNL]
2205 Time (s) between statistics printk()s.
2207 locktorture.stutter= [KNL]
2208 Time (s) to stutter testing, for example,
2209 specifying five seconds causes the test to run for
2210 five seconds, wait for five seconds, and so on.
2211 This tests the locking primitive's ability to
2212 transition abruptly to and from idle.
2214 locktorture.torture_type= [KNL]
2215 Specify the locking implementation to test.
2217 locktorture.verbose= [KNL]
2218 Enable additional printk() statements.
2220 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2223 loglevel= All Kernel Messages with a loglevel smaller than the
2224 console loglevel will be printed to the console. It can
2225 also be changed with klogd or other programs. The
2226 loglevels are defined as follows:
2228 0 (KERN_EMERG) system is unusable
2229 1 (KERN_ALERT) action must be taken immediately
2230 2 (KERN_CRIT) critical conditions
2231 3 (KERN_ERR) error conditions
2232 4 (KERN_WARNING) warning conditions
2233 5 (KERN_NOTICE) normal but significant condition
2234 6 (KERN_INFO) informational
2235 7 (KERN_DEBUG) debug-level messages
2237 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2238 in bytes. n must be a power of two and greater
2239 than the minimal size. The minimal size is defined
2240 by LOG_BUF_SHIFT kernel config parameter. There is
2241 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2242 that allows to increase the default size depending on
2243 the number of CPUs. See init/Kconfig for more details.
2245 logo.nologo [FB] Disables display of the built-in Linux logo.
2246 This may be used to provide more screen space for
2247 kernel log messages and is useful when debugging
2248 kernel boot problems.
2250 lp=0 [LP] Specify parallel ports to use, e.g,
2251 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2252 lp=reset first parallel port). 'lp=0' disables the
2253 lp=auto printer driver. 'lp=reset' (which can be
2254 specified in addition to the ports) causes
2255 attached printers to be reset. Using
2256 lp=port1,port2,... specifies the parallel ports
2257 to associate lp devices with, starting with
2258 lp0. A port specification may be 'none' to skip
2259 that lp device, or a parport name such as
2260 'parport0'. Specifying 'lp=auto' instead of a
2261 port specification list means that device IDs
2262 from each port should be examined, to see if
2263 an IEEE 1284-compliant printer is attached; if
2264 so, the driver will manage that printer.
2265 See also header of drivers/char/lp.c.
2268 Sets loops_per_jiffy to given constant, thus avoiding
2269 time-consuming boot-time autodetection (up to 250 ms per
2270 CPU). 0 enables autodetection (default). To determine
2271 the correct value for your kernel, boot with normal
2272 autodetection and see what value is printed. Note that
2273 on SMP systems the preset will be applied to all CPUs,
2274 which is likely to cause problems if your CPUs need
2275 significantly divergent settings. An incorrect value
2276 will cause delays in the kernel to be wrong, leading to
2277 unpredictable I/O errors and other breakage. Although
2278 unlikely, in the extreme case this might damage your
2282 Format: <io>,<irq>,<dma>
2284 machvec= [IA-64] Force the use of a particular machine-vector
2285 (machvec) in a generic kernel.
2286 Example: machvec=hpzx1_swiotlb
2288 machtype= [Loongson] Share the same kernel image file between different
2290 Example: machtype=lemote-yeeloong-2f-7inch
2292 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2293 than or equal to this physical address is ignored.
2295 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2296 will bring up during bootup. maxcpus=n : n >= 0 limits
2297 the kernel to bring up 'n' processors. Surely after
2298 bootup you can bring up the other plugged cpu by executing
2299 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2300 only takes effect during system bootup.
2301 While n=0 is a special case, it is equivalent to "nosmp",
2302 which also disables the IO APIC.
2304 max_loop= [LOOP] The number of loop block devices that get
2305 (loop.max_loop) unconditionally pre-created at init time. The default
2306 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2307 of statically allocating a predefined number, loop
2308 devices can be requested on-demand with the
2309 /dev/loop-control interface.
2311 mce [X86-32] Machine Check Exception
2313 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2315 md= [HW] RAID subsystems devices and level
2316 See Documentation/admin-guide/md.rst.
2319 Format: <first>,<last>
2320 Specifies range of consoles to be captured by the MDA.
2323 Control mitigation for the Micro-architectural Data
2324 Sampling (MDS) vulnerability.
2326 Certain CPUs are vulnerable to an exploit against CPU
2327 internal buffers which can forward information to a
2328 disclosure gadget under certain conditions.
2330 In vulnerable processors, the speculatively
2331 forwarded data can be used in a cache side channel
2332 attack, to access data to which the attacker does
2333 not have direct access.
2335 This parameter controls the MDS mitigation. The
2338 full - Enable MDS mitigation on vulnerable CPUs
2339 full,nosmt - Enable MDS mitigation and disable
2340 SMT on vulnerable CPUs
2341 off - Unconditionally disable MDS mitigation
2343 Not specifying this option is equivalent to
2346 For details see: Documentation/admin-guide/hw-vuln/mds.rst
2348 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2349 Amount of memory to be used when the kernel is not able
2350 to see the whole system memory or for test.
2351 [X86] Work as limiting max address. Use together
2352 with memmap= to avoid physical address space collisions.
2353 Without memmap= PCI devices could be placed at addresses
2354 belonging to unused RAM.
2356 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2360 [KNL,SH] Allow user to override the default size for
2361 per-device physically contiguous DMA buffers.
2363 memhp_default_state=online/offline
2364 [KNL] Set the initial state for the memory hotplug
2365 onlining policy. If not specified, the default value is
2366 set according to the
2367 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2369 See Documentation/memory-hotplug.txt.
2371 memmap=exactmap [KNL,X86] Enable setting of an exact
2372 E820 memory map, as specified by the user.
2373 Such memmap=exactmap lines can be constructed based on
2374 BIOS output or other requirements. See the memmap=nn@ss
2377 memmap=nn[KMG]@ss[KMG]
2378 [KNL] Force usage of a specific region of memory.
2379 Region of memory to be used is from ss to ss+nn.
2380 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2381 which limits max address to nn[KMG].
2382 Multiple different regions can be specified,
2385 memmap=100M@2G,100M#3G,1G!1024G
2387 memmap=nn[KMG]#ss[KMG]
2388 [KNL,ACPI] Mark specific memory as ACPI data.
2389 Region of memory to be marked is from ss to ss+nn.
2391 memmap=nn[KMG]$ss[KMG]
2392 [KNL,ACPI] Mark specific memory as reserved.
2393 Region of memory to be reserved is from ss to ss+nn.
2394 Example: Exclude memory from 0x18690000-0x1869ffff
2395 memmap=64K$0x18690000
2397 memmap=0x10000$0x18690000
2398 Some bootloaders may need an escape character before '$',
2399 like Grub2, otherwise '$' and the following number
2402 memmap=nn[KMG]!ss[KMG]
2403 [KNL,X86] Mark specific memory as protected.
2404 Region of memory to be used, from ss to ss+nn.
2405 The memory region may be marked as e820 type 12 (0xc)
2406 and is NVDIMM or ADR memory.
2408 memmap=<size>%<offset>-<oldtype>+<newtype>
2409 [KNL,ACPI] Convert memory within the specified region
2410 from <oldtype> to <newtype>. If "-<oldtype>" is left
2411 out, the whole region will be marked as <newtype>,
2412 even if previously unavailable. If "+<newtype>" is left
2413 out, matching memory will be removed. Types are
2414 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2415 3 = ACPI, 12 = PRAM.
2417 memory_corruption_check=0/1 [X86]
2418 Some BIOSes seem to corrupt the first 64k of
2419 memory when doing things like suspend/resume.
2420 Setting this option will scan the memory
2421 looking for corruption. Enabling this will
2422 both detect corruption and prevent the kernel
2423 from using the memory being corrupted.
2424 However, its intended as a diagnostic tool; if
2425 repeatable BIOS-originated corruption always
2426 affects the same memory, you can use memmap=
2427 to prevent the kernel from using that memory.
2429 memory_corruption_check_size=size [X86]
2430 By default it checks for corruption in the low
2431 64k, making this memory unavailable for normal
2432 use. Use this parameter to scan for
2433 corruption in more or less memory.
2435 memory_corruption_check_period=seconds [X86]
2436 By default it checks for corruption every 60
2437 seconds. Use this parameter to check at some
2438 other rate. 0 disables periodic checking.
2440 memtest= [KNL,X86,ARM] Enable memtest
2442 default : 0 <disable>
2443 Specifies the number of memtest passes to be
2444 performed. Each pass selects another test
2445 pattern from a given set of patterns. Memtest
2446 fills the memory with this pattern, validates
2447 memory contents and reserves bad memory
2448 regions that are detected.
2450 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2451 Valid arguments: on, off
2452 Default (depends on kernel configuration option):
2453 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2454 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2455 mem_encrypt=on: Activate SME
2456 mem_encrypt=off: Do not activate SME
2458 Refer to Documentation/x86/amd-memory-encryption.txt
2459 for details on when memory encryption can be activated.
2461 mem_sleep_default= [SUSPEND] Default system suspend mode:
2462 s2idle - Suspend-To-Idle
2463 shallow - Power-On Suspend or equivalent (if supported)
2464 deep - Suspend-To-RAM or equivalent (if supported)
2465 See Documentation/admin-guide/pm/sleep-states.rst.
2467 meye.*= [HW] Set MotionEye Camera parameters
2468 See Documentation/media/v4l-drivers/meye.rst.
2470 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2471 Multi-Function General Purpose Timers on AMD Geode
2474 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2475 the BIOS has incorrectly applied a workaround. TinyBIOS
2476 version 0.98 is known to be affected, 0.99 fixes the
2477 problem by letting the user disable the workaround.
2481 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2482 physical address is ignored.
2484 mini2440= [ARM,HW,KNL]
2485 Format:[0..2][b][c][t]
2487 MINI2440 configuration specification:
2488 0 - The attached screen is the 3.5" TFT
2489 1 - The attached screen is the 7" TFT
2490 2 - The VGA Shield is attached (1024x768)
2491 Leaving out the screen size parameter will not load
2492 the TFT driver, and the framebuffer will be left
2494 b - Enable backlight. The TFT backlight pin will be
2495 linked to the kernel VESA blanking code and a GPIO
2496 LED. This parameter is not necessary when using the
2498 c - Enable the s3c camera interface.
2499 t - Reserved for enabling touchscreen support. The
2500 touchscreen support is not enabled in the mainstream
2501 kernel as of 2.6.30, a preliminary port can be found
2502 in the "bleeding edge" mini2440 support kernel at
2503 http://repo.or.cz/w/linux-2.6/mini2440.git
2506 [X86,PPC,S390] Control optional mitigations for CPU
2507 vulnerabilities. This is a set of curated,
2508 arch-independent options, each of which is an
2509 aggregation of existing arch-specific options.
2512 Disable all optional CPU mitigations. This
2513 improves system performance, but it may also
2514 expose users to several CPU vulnerabilities.
2515 Equivalent to: nopti [X86,PPC]
2519 nospectre_v2 [X86,PPC,S390]
2520 spectre_v2_user=off [X86]
2521 spec_store_bypass_disable=off [X86,PPC]
2526 Mitigate all CPU vulnerabilities, but leave SMT
2527 enabled, even if it's vulnerable. This is for
2528 users who don't want to be surprised by SMT
2529 getting disabled across kernel upgrades, or who
2530 have other ways of avoiding SMT-based attacks.
2531 Equivalent to: (default behavior)
2534 Mitigate all CPU vulnerabilities, disabling SMT
2535 if needed. This is for users who always want to
2536 be fully mitigated, even if it means losing SMT.
2537 Equivalent to: l1tf=flush,nosmt [X86]
2538 mds=full,nosmt [X86]
2541 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2542 parameter allows control of the logging verbosity for
2543 the additional memory initialisation checks. A value
2544 of 0 disables mminit logging and a level of 4 will
2545 log everything. Information is printed at KERN_DEBUG
2546 so loglevel=8 may also need to be specified.
2549 [KNL] When CONFIG_MODULE_SIG is set, this means that
2550 modules without (valid) signatures will fail to load.
2551 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2552 is always true, so this option does nothing.
2554 module_blacklist= [KNL] Do not load a comma-separated list of
2555 modules. Useful for debugging problem modules.
2558 [MOUSE] Maximum time between finger touching and
2559 leaving touchpad surface for touch to be considered
2560 a tap and be reported as a left button click (for
2561 touchpads working in absolute mode only).
2563 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2564 reporting absolute coordinates, such as tablets
2565 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2566 reporting absolute coordinates, such as tablets
2568 movablecore= [KNL,X86,IA-64,PPC]
2569 Format: nn[KMGTPE] | nn%
2570 This parameter is the complement to kernelcore=, it
2571 specifies the amount of memory used for migratable
2572 allocations. If both kernelcore and movablecore is
2573 specified, then kernelcore will be at *least* the
2574 specified value but may be more. If movablecore on its
2575 own is specified, the administrator must be careful
2576 that the amount of memory usable for all allocations
2579 movable_node [KNL] Boot-time switch to make hotplugable memory
2580 NUMA nodes to be movable. This means that the memory
2581 of such nodes will be usable only for movable
2582 allocations which rules out almost all kernel
2583 allocations. Use with caution!
2585 MTD_Partition= [MTD]
2586 Format: <name>,<region-number>,<size>,<offset>
2588 MTD_Region= [MTD] Format:
2589 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2592 See drivers/mtd/cmdlinepart.c.
2594 multitce=off [PPC] This parameter disables the use of the pSeries
2595 firmware feature for updating multiple TCE entries
2598 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2600 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2602 boundary - index of last SLC block on Flex-OneNAND.
2603 The remaining blocks are configured as MLC blocks.
2604 lock - Configure if Flex-OneNAND boundary should be locked.
2605 Once locked, the boundary cannot be changed.
2606 1 indicates lock status, 0 indicates unlock status.
2609 ARM/S3C2412 JIVE boot control
2611 See arch/arm/mach-s3c2412/mach-jive.c
2613 mtouchusb.raw_coordinates=
2614 [HW] Make the MicroTouch USB driver use raw coordinates
2615 ('y', default) or cooked coordinates ('n')
2617 mtrr_chunk_size=nn[KMG] [X86]
2618 used for mtrr cleanup. It is largest continuous chunk
2619 that could hold holes aka. UC entries.
2621 mtrr_gran_size=nn[KMG] [X86]
2622 Used for mtrr cleanup. It is granularity of mtrr block.
2624 Large value could prevent small alignment from
2627 mtrr_spare_reg_nr=n [X86]
2629 Range: 0,7 : spare reg number
2631 Used for mtrr cleanup. It is spare mtrr entries number.
2632 Set to 2 or more if your graphical card needs more.
2634 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2636 netdev= [NET] Network devices parameters
2637 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2638 Note that mem_start is often overloaded to mean
2639 something different and driver-specific.
2640 This usage is only documented in each driver source
2644 [NETFILTER] Enable connection tracking flow accounting
2645 0 to disable accounting
2646 1 to enable accounting
2649 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2650 See Documentation/filesystems/nfs/nfsroot.txt.
2652 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2653 See Documentation/filesystems/nfs/nfsroot.txt.
2655 nfsrootdebug [NFS] enable nfsroot debugging messages.
2656 See Documentation/filesystems/nfs/nfsroot.txt.
2658 nfs.callback_nr_threads=
2659 [NFSv4] set the total number of threads that the
2660 NFS client will assign to service NFSv4 callback
2663 nfs.callback_tcpport=
2664 [NFS] set the TCP port on which the NFSv4 callback
2665 channel should listen.
2668 [NFS] sets the pathname to the program which is used
2669 to update the NFS client cache entries.
2671 nfs.cache_getent_timeout=
2672 [NFS] sets the timeout after which an attempt to
2673 update a cache entry is deemed to have failed.
2675 nfs.idmap_cache_timeout=
2676 [NFS] set the maximum lifetime for idmapper cache
2680 [NFS] enable 64-bit inode numbers.
2681 If zero, the NFS client will fake up a 32-bit inode
2682 number for the readdir() and stat() syscalls instead
2683 of returning the full 64-bit number.
2684 The default is to return 64-bit inode numbers.
2686 nfs.max_session_cb_slots=
2687 [NFSv4.1] Sets the maximum number of session
2688 slots the client will assign to the callback
2689 channel. This determines the maximum number of
2690 callbacks the client will process in parallel for
2691 a particular server.
2693 nfs.max_session_slots=
2694 [NFSv4.1] Sets the maximum number of session slots
2695 the client will attempt to negotiate with the server.
2696 This limits the number of simultaneous RPC requests
2697 that the client can send to the NFSv4.1 server.
2698 Note that there is little point in setting this
2699 value higher than the max_tcp_slot_table_limit.
2701 nfs.nfs4_disable_idmapping=
2702 [NFSv4] When set to the default of '1', this option
2703 ensures that both the RPC level authentication
2704 scheme and the NFS level operations agree to use
2705 numeric uids/gids if the mount is using the
2706 'sec=sys' security flavour. In effect it is
2707 disabling idmapping, which can make migration from
2708 legacy NFSv2/v3 systems to NFSv4 easier.
2709 Servers that do not support this mode of operation
2710 will be autodetected by the client, and it will fall
2711 back to using the idmapper.
2712 To turn off this behaviour, set the value to '0'.
2714 [NFS4] Specify an additional fixed unique ident-
2715 ification string that NFSv4 clients can insert into
2716 their nfs_client_id4 string. This is typically a
2717 UUID that is generated at system install time.
2719 nfs.send_implementation_id =
2720 [NFSv4.1] Send client implementation identification
2721 information in exchange_id requests.
2722 If zero, no implementation identification information
2724 The default is to send the implementation identification
2727 nfs.recover_lost_locks =
2728 [NFSv4] Attempt to recover locks that were lost due
2729 to a lease timeout on the server. Please note that
2730 doing this risks data corruption, since there are
2731 no guarantees that the file will remain unchanged
2732 after the locks are lost.
2733 If you want to enable the kernel legacy behaviour of
2734 attempting to recover these locks, then set this
2736 The default parameter value of '0' causes the kernel
2737 not to attempt recovery of lost locks.
2739 nfs4.layoutstats_timer =
2740 [NFSv4.2] Change the rate at which the kernel sends
2741 layoutstats to the pNFS metadata server.
2743 Setting this to value to 0 causes the kernel to use
2744 whatever value is the default set by the layout
2745 driver. A non-zero value sets the minimum interval
2746 in seconds between layoutstats transmissions.
2748 nfsd.nfs4_disable_idmapping=
2749 [NFSv4] When set to the default of '1', the NFSv4
2750 server will return only numeric uids and gids to
2751 clients using auth_sys, and will accept numeric uids
2752 and gids from such clients. This is intended to ease
2753 migration from NFSv2/v3.
2755 nmi_debug= [KNL,SH] Specify one or more actions to take
2756 when a NMI is triggered.
2757 Format: [state][,regs][,debounce][,die]
2759 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2760 Format: [panic,][nopanic,][num]
2762 0 - turn hardlockup detector in nmi_watchdog off
2763 1 - turn hardlockup detector in nmi_watchdog on
2764 When panic is specified, panic when an NMI watchdog
2765 timeout occurs (or 'nopanic' to override the opposite
2766 default). To disable both hard and soft lockup detectors,
2767 please see 'nowatchdog'.
2768 This is useful when you use a panic=... timeout and
2769 need the box quickly up again.
2771 These settings can be accessed at runtime via
2772 the nmi_watchdog and hardlockup_panic sysctls.
2774 netpoll.carrier_timeout=
2775 [NET] Specifies amount of time (in seconds) that
2776 netpoll should wait for a carrier. By default netpoll
2779 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2780 emulation library even if a 387 maths coprocessor
2783 no5lvl [X86-64] Disable 5-level paging mode. Forces
2784 kernel to use 4-level paging instead.
2787 [HW] Never suspend the console
2788 Disable suspending of consoles during suspend and
2789 hibernate operations. Once disabled, debugging
2790 messages can reach various consoles while the rest
2791 of the system is being put to sleep (ie, while
2792 debugging driver suspend/resume hooks). This may
2793 not work reliably with all consoles, but is known
2794 to work with serial and VGA consoles.
2795 To facilitate more flexible debugging, we also add
2796 console_suspend, a printk module parameter to control
2797 it. Users could use console_suspend (usually
2798 /sys/module/printk/parameters/console_suspend) to
2799 turn on/off it dynamically.
2801 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2802 caches in the slab allocator. Saves per-node memory,
2803 but will impact performance.
2807 noaltinstr [S390] Disables alternative instructions patching
2808 (CPU alternatives feature).
2810 noapic [SMP,APIC] Tells the kernel to not make use of any
2811 IOAPICs that may be present in the system.
2813 noautogroup Disable scheduler automatic task group creation.
2815 nobats [PPC] Do not use BATs for mapping kernel lowmem
2816 on "Classic" PPC cores.
2820 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2822 nodelayacct [KNL] Disable per-task delay accounting
2824 nodsp [SH] Disable hardware DSP at boot time.
2826 noefi Disable EFI runtime services support.
2831 On X86-32 available only on PAE configured kernels.
2832 noexec=on: enable non-executable mappings (default)
2833 noexec=off: disable non-executable mappings
2836 Disable SMAP (Supervisor Mode Access Prevention)
2837 even if it is supported by processor.
2840 Disable SMEP (Supervisor Mode Execution Prevention)
2841 even if it is supported by processor.
2844 This affects only 32-bit executables.
2845 noexec32=on: enable non-executable mappings (default)
2846 read doesn't imply executable mappings
2847 noexec32=off: disable non-executable mappings
2848 read implies executable mappings
2850 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2852 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2853 register save and restore. The kernel will only save
2854 legacy floating-point registers on task switch.
2856 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2858 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2859 Equivalent to smt=1.
2861 [KNL,x86] Disable symmetric multithreading (SMT).
2862 nosmt=force: Force disable SMT, cannot be undone
2863 via the sysfs control file.
2865 nospectre_v1 [X66, PPC] Disable mitigations for Spectre Variant 1
2866 (bounds check bypass). With this option data leaks
2867 are possible in the system.
2869 nospectre_v2 [X86,PPC_FSL_BOOK3E] Disable all mitigations for the Spectre variant 2
2870 (indirect branch prediction) vulnerability. System may
2871 allow data leaks with this option, which is equivalent
2874 nospec_store_bypass_disable
2875 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
2877 noxsave [BUGS=X86] Disables x86 extended register state save
2878 and restore using xsave. The kernel will fallback to
2879 enabling legacy floating-point and sse state.
2881 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2882 register states. The kernel will fall back to use
2883 xsave to save the states. By using this parameter,
2884 performance of saving the states is degraded because
2885 xsave doesn't support modified optimization while
2886 xsaveopt supports it on xsaveopt enabled systems.
2888 noxsaves [X86] Disables xsaves and xrstors used in saving and
2889 restoring x86 extended register state in compacted
2890 form of xsave area. The kernel will fall back to use
2891 xsaveopt and xrstor to save and restore the states
2892 in standard form of xsave area. By using this
2893 parameter, xsave area per process might occupy more
2894 memory on xsaves enabled systems.
2896 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2897 wfi(ARM) instruction doesn't work correctly and not to
2898 use it. This is also useful when using JTAG debugger.
2900 no_file_caps Tells the kernel not to honor file capabilities. The
2901 only way then for a file to be executed with privilege
2902 is to be setuid root or executed by root.
2904 nohalt [IA-64] Tells the kernel not to use the power saving
2905 function PAL_HALT_LIGHT when idle. This increases
2906 power-consumption. On the positive side, it reduces
2907 interrupt wake-up latency, which may improve performance
2908 in certain environments such as networked servers or
2911 nohibernate [HIBERNATION] Disable hibernation and resume.
2913 nohz= [KNL] Boottime enable/disable dynamic ticks
2914 Valid arguments: on, off
2917 nohz_full= [KNL,BOOT,SMP,ISOL]
2918 The argument is a cpu list, as described above.
2919 In kernels built with CONFIG_NO_HZ_FULL=y, set
2920 the specified list of CPUs whose tick will be stopped
2921 whenever possible. The boot CPU will be forced outside
2922 the range to maintain the timekeeping. Any CPUs
2923 in this list will have their RCU callbacks offloaded,
2924 just as if they had also been called out in the
2925 rcu_nocbs= boot parameter.
2927 noiotrap [SH] Disables trapped I/O port accesses.
2929 noirqdebug [X86-32] Disables the code which attempts to detect and
2930 disable unhandled interrupt sources.
2932 no_timer_check [X86,APIC] Disables the code which tests for
2933 broken timer IRQ sources.
2935 noisapnp [ISAPNP] Disables ISA PnP code.
2937 noinitrd [RAM] Tells the kernel not to load any configured
2940 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2942 [Deprecated - use intremap=off]
2946 noinvpcid [X86] Disable the INVPCID cpu feature.
2948 nojitter [IA-64] Disables jitter checking for ITC timers.
2950 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2952 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2956 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2957 clock and use the default one.
2959 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2960 steal time is computed, but won't influence scheduler
2963 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2965 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2967 noltlbs [PPC] Do not use large page/tlb entries for kernel
2968 lowmem mapping on PPC40x and PPC8xx
2970 nomca [IA-64] Disable machine check abort handling
2972 nomce [X86-32] Disable Machine Check Exception
2974 nomfgpt [X86-32] Disable Multi-Function General Purpose
2975 Timer usage (for AMD Geode machines).
2977 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2978 shutdown the other cpus. Instead use the REBOOT_VECTOR
2981 nomodule Disable module load
2983 nopat [X86] Disable PAT (page attribute table extension of
2984 pagetables) support.
2986 nopcid [X86-64] Disable the PCID cpu feature.
2988 norandmaps Don't use address space randomization. Equivalent to
2989 echo 0 > /proc/sys/kernel/randomize_va_space
2991 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2992 with UP alternatives
2994 nordrand [X86] Disable kernel use of the RDRAND and
2995 RDSEED instructions even if they are supported
2996 by the processor. RDRAND and RDSEED are still
2997 available to user space applications.
2999 noresume [SWSUSP] Disables resume and restores original swap
3002 no-scroll [VGA] Disables scrollback.
3003 This is required for the Braillex ib80-piezo Braille
3004 reader made by F.H. Papenmeier (Germany).
3008 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
3010 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
3011 and disable the IO APIC. legacy for "maxcpus=0".
3013 nosoftlockup [KNL] Disable the soft-lockup detector.
3015 nosync [HW,M68K] Disables sync negotiation for all devices.
3017 nowatchdog [KNL] Disable both lockup detectors, i.e.
3018 soft-lockup and NMI watchdog (hard-lockup).
3022 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
3024 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
3025 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
3026 Some features depend on CPU0. Known dependencies are:
3027 1. Resume from suspend/hibernate depends on CPU0.
3028 Suspend/hibernate will fail if CPU0 is offline and you
3029 need to online CPU0 before suspend/hibernate.
3030 2. PIC interrupts also depend on CPU0. CPU0 can't be
3031 removed if a PIC interrupt is detected.
3032 It's said poweroff/reboot may depend on CPU0 on some
3033 machines although I haven't seen such issues so far
3034 after CPU0 is offline on a few tested machines.
3035 If the dependencies are under your control, you can
3036 turn on cpu0_hotplug.
3038 nps_mtm_hs_ctr= [KNL,ARC]
3039 This parameter sets the maximum duration, in
3040 cycles, each HW thread of the CTOP can run
3041 without interruptions, before HW switches it.
3042 The actual maximum duration is 16 times this
3044 Format: integer between 1 and 255
3047 nptcg= [IA-64] Override max number of concurrent global TLB
3048 purges which is reported from either PAL_VM_SUMMARY or
3051 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
3052 could support. nr_cpus=n : n >= 1 limits the kernel to
3053 support 'n' processors. It could be larger than the
3054 number of already plugged CPU during bootup, later in
3055 runtime you can physically add extra cpu until it reaches
3056 n. So during boot up some boot time memory for per-cpu
3057 variables need be pre-allocated for later physical cpu
3060 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
3062 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
3063 Allowed values are enable and disable
3065 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
3066 'node', 'default' can be specified
3067 This can be set from sysctl after boot.
3068 See Documentation/sysctl/vm.txt for details.
3070 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
3071 See Documentation/debugging-via-ohci1394.txt for more
3074 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
3075 Rather than timing out after 20 ms if an EC
3076 command is not properly ACKed, override the length
3077 of the timeout. We have interrupts disabled while
3078 waiting for the ACK, so if this is set too high
3079 interrupts *may* be lost!
3081 omap_mux= [OMAP] Override bootloader pin multiplexing.
3082 Format: <mux_mode0.mode_name=value>...
3083 For example, to override I2C bus2:
3084 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
3086 oprofile.timer= [HW]
3087 Use timer interrupt instead of performance counters
3089 oprofile.cpu_type= Force an oprofile cpu type
3090 This might be useful if you have an older oprofile
3091 userland or if you want common events.
3092 Format: { arch_perfmon }
3093 arch_perfmon: [X86] Force use of architectural
3094 perfmon on Intel CPUs instead of the
3095 CPU specific event set.
3096 timer: [X86] Force use of architectural NMI
3097 timer mode (see also oprofile.timer
3098 for generic hr timer mode)
3100 oops=panic Always panic on oopses. Default is to just kill the
3101 process, but there is a small probability of
3102 deadlocking the machine.
3103 This will also cause panics on machine check exceptions.
3104 Useful together with panic=30 to trigger a reboot.
3106 page_owner= [KNL] Boot-time page_owner enabling option.
3107 Storage of the information about who allocated
3108 each page is disabled in default. With this switch,
3110 on: enable the feature
3112 page_poison= [KNL] Boot-time parameter changing the state of
3113 poisoning on the buddy allocator, available with
3114 CONFIG_PAGE_POISONING=y.
3115 off: turn off poisoning (default)
3116 on: turn on poisoning
3118 panic= [KNL] Kernel behaviour on panic: delay <timeout>
3119 timeout > 0: seconds before rebooting
3120 timeout = 0: wait forever
3121 timeout < 0: reboot immediately
3124 panic_on_warn panic() instead of WARN(). Useful to cause kdump
3127 crash_kexec_post_notifiers
3128 Run kdump after running panic-notifiers and dumping
3129 kmsg. This only for the users who doubt kdump always
3130 succeeds in any situation.
3131 Note that this also increases risks of kdump failure,
3132 because some panic notifiers can make the crashed
3133 kernel more unstable.
3135 parkbd.port= [HW] Parallel port number the keyboard adapter is
3136 connected to, default is 0.
3138 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
3139 0 for XT, 1 for AT (default is AT).
3142 parport= [HW,PPT] Specify parallel ports. 0 disables.
3143 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
3144 Use 'auto' to force the driver to use any
3145 IRQ/DMA settings detected (the default is to
3146 ignore detected IRQ/DMA settings because of
3147 possible conflicts). You can specify the base
3148 address, IRQ, and DMA settings; IRQ and DMA
3149 should be numbers, or 'auto' (for using detected
3150 settings on that particular port), or 'nofifo'
3151 (to avoid using a FIFO even if it is detected).
3152 Parallel ports are assigned in the order they
3153 are specified on the command line, starting
3156 parport_init_mode= [HW,PPT]
3157 Configure VIA parallel port to operate in
3158 a specific mode. This is necessary on Pegasos
3159 computer where firmware has no options for setting
3160 up parallel port mode and sets it to spp.
3161 Currently this function knows 686a and 8231 chips.
3162 Format: [spp|ps2|epp|ecp|ecpepp]
3165 Halt all CPUs after the first oops has been printed for
3166 the specified number of seconds. This is to be used if
3167 your oopses keep scrolling off the screen.
3172 See header of drivers/block/paride/pcd.c.
3173 See also Documentation/blockdev/paride.txt.
3175 pci=option[,option...] [PCI] various PCI subsystem options.
3177 Some options herein operate on a specific device
3178 or a set of devices (<pci_dev>). These are
3179 specified in one of the following formats:
3181 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
3182 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
3184 Note: the first format specifies a PCI
3185 bus/device/function address which may change
3186 if new hardware is inserted, if motherboard
3187 firmware changes, or due to changes caused
3188 by other kernel parameters. If the
3189 domain is left unspecified, it is
3190 taken to be zero. Optionally, a path
3191 to a device through multiple device/function
3192 addresses can be specified after the base
3193 address (this is more robust against
3194 renumbering issues). The second format
3195 selects devices using IDs from the
3196 configuration space which may match multiple
3197 devices in the system.
3199 earlydump dump PCI config space before the kernel
3201 off [X86] don't probe for the PCI bus
3202 bios [X86-32] force use of PCI BIOS, don't access
3203 the hardware directly. Use this if your machine
3204 has a non-standard PCI host bridge.
3205 nobios [X86-32] disallow use of PCI BIOS, only direct
3206 hardware access methods are allowed. Use this
3207 if you experience crashes upon bootup and you
3208 suspect they are caused by the BIOS.
3209 conf1 [X86] Force use of PCI Configuration Access
3210 Mechanism 1 (config address in IO port 0xCF8,
3211 data in IO port 0xCFC, both 32-bit).
3212 conf2 [X86] Force use of PCI Configuration Access
3213 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3214 the function, IO port 0xCFA, also 8-bit, sets
3215 bus number. The config space is then accessed
3216 through ports 0xC000-0xCFFF).
3217 See http://wiki.osdev.org/PCI for more info
3218 on the configuration access mechanisms.
3219 noaer [PCIE] If the PCIEAER kernel config parameter is
3220 enabled, this kernel boot option can be used to
3221 disable the use of PCIE advanced error reporting.
3222 nodomains [PCI] Disable support for multiple PCI
3223 root domains (aka PCI segments, in ACPI-speak).
3224 nommconf [X86] Disable use of MMCONFIG for PCI
3226 check_enable_amd_mmconf [X86] check for and enable
3227 properly configured MMIO access to PCI
3228 config space on AMD family 10h CPU
3229 nomsi [MSI] If the PCI_MSI kernel config parameter is
3230 enabled, this kernel boot option can be used to
3231 disable the use of MSI interrupts system-wide.
3232 noioapicquirk [APIC] Disable all boot interrupt quirks.
3233 Safety option to keep boot IRQs enabled. This
3234 should never be necessary.
3235 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3236 primary IO-APIC for bridges that cannot disable
3237 boot IRQs. This fixes a source of spurious IRQs
3238 when the system masks IRQs.
3239 noioapicreroute [APIC] Disable workaround that uses the
3240 boot IRQ equivalent of an IRQ that connects to
3241 a chipset where boot IRQs cannot be disabled.
3242 The opposite of ioapicreroute.
3243 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3244 routing table. These calls are known to be buggy
3245 on several machines and they hang the machine
3246 when used, but on other computers it's the only
3247 way to get the interrupt routing table. Try
3248 this option if the kernel is unable to allocate
3249 IRQs or discover secondary PCI buses on your
3251 rom [X86] Assign address space to expansion ROMs.
3252 Use with caution as certain devices share
3253 address decoders between ROMs and other
3255 norom [X86] Do not assign address space to
3256 expansion ROMs that do not already have
3257 BIOS assigned address ranges.
3258 nobar [X86] Do not assign address space to the
3259 BARs that weren't assigned by the BIOS.
3260 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3261 assigned automatically to PCI devices. You can
3262 make the kernel exclude IRQs of your ISA cards
3264 pirqaddr=0xAAAAA [X86] Specify the physical address
3265 of the PIRQ table (normally generated
3266 by the BIOS) if it is outside the
3267 F0000h-100000h range.
3268 lastbus=N [X86] Scan all buses thru bus #N. Can be
3269 useful if the kernel is unable to find your
3270 secondary buses and you want to tell it
3271 explicitly which ones they are.
3272 assign-busses [X86] Always assign all PCI bus
3273 numbers ourselves, overriding
3274 whatever the firmware may have done.
3275 usepirqmask [X86] Honor the possible IRQ mask stored
3276 in the BIOS $PIR table. This is needed on
3277 some systems with broken BIOSes, notably
3278 some HP Pavilion N5400 and Omnibook XE3
3279 notebooks. This will have no effect if ACPI
3280 IRQ routing is enabled.
3281 noacpi [X86] Do not use ACPI for IRQ routing
3282 or for PCI scanning.
3283 use_crs [X86] Use PCI host bridge window information
3284 from ACPI. On BIOSes from 2008 or later, this
3285 is enabled by default. If you need to use this,
3286 please report a bug.
3287 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3288 If you need to use this, please report a bug.
3289 routeirq Do IRQ routing for all PCI devices.
3290 This is normally done in pci_enable_device(),
3291 so this option is a temporary workaround
3292 for broken drivers that don't call it.
3293 skip_isa_align [X86] do not align io start addr, so can
3294 handle more pci cards
3295 noearly [X86] Don't do any early type 1 scanning.
3296 This might help on some broken boards which
3297 machine check when some devices' config space
3298 is read. But various workarounds are disabled
3299 and some IOMMU drivers will not work.
3300 bfsort Sort PCI devices into breadth-first order.
3301 This sorting is done to get a device
3302 order compatible with older (<= 2.4) kernels.
3303 nobfsort Don't sort PCI devices into breadth-first order.
3304 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3305 tuning and use the BIOS-configured MPS defaults.
3306 pcie_bus_safe Set every device's MPS to the largest value
3307 supported by all devices below the root complex.
3308 pcie_bus_perf Set device MPS to the largest allowable MPS
3309 based on its parent bus. Also set MRRS (Max
3310 Read Request Size) to the largest supported
3311 value (no larger than the MPS that the device
3312 or bus can support) for best performance.
3313 pcie_bus_peer2peer Set every device's MPS to 128B, which
3314 every device is guaranteed to support. This
3315 configuration allows peer-to-peer DMA between
3316 any pair of devices, possibly at the cost of
3317 reduced performance. This also guarantees
3318 that hot-added devices will work.
3319 cbiosize=nn[KMG] The fixed amount of bus space which is
3320 reserved for the CardBus bridge's IO window.
3321 The default value is 256 bytes.
3322 cbmemsize=nn[KMG] The fixed amount of bus space which is
3323 reserved for the CardBus bridge's memory
3324 window. The default value is 64 megabytes.
3327 [<order of align>@]<pci_dev>[; ...]
3328 Specifies alignment and device to reassign
3329 aligned memory resources. How to
3330 specify the device is described above.
3331 If <order of align> is not specified,
3332 PAGE_SIZE is used as alignment.
3333 PCI-PCI bridge can be specified, if resource
3334 windows need to be expanded.
3335 To specify the alignment for several
3336 instances of a device, the PCI vendor,
3337 device, subvendor, and subdevice may be
3338 specified, e.g., 4096@pci:8086:9c22:103c:198f
3339 ecrc= Enable/disable PCIe ECRC (transaction layer
3340 end-to-end CRC checking).
3341 bios: Use BIOS/firmware settings. This is the
3345 hpiosize=nn[KMG] The fixed amount of bus space which is
3346 reserved for hotplug bridge's IO window.
3347 Default size is 256 bytes.
3348 hpmemsize=nn[KMG] The fixed amount of bus space which is
3349 reserved for hotplug bridge's memory window.
3350 Default size is 2 megabytes.
3351 hpbussize=nn The minimum amount of additional bus numbers
3352 reserved for buses below a hotplug bridge.
3354 realloc= Enable/disable reallocating PCI bridge resources
3355 if allocations done by BIOS are too small to
3356 accommodate resources required by all child
3358 off: Turn realloc off
3360 realloc same as realloc=on
3361 noari do not use PCIe ARI.
3362 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
3363 do not use PCIe ATS (and IOMMU device IOTLB).
3364 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3365 only look for one device below a PCIe downstream
3367 big_root_window Try to add a big 64bit memory window to the PCIe
3368 root complex on AMD CPUs. Some GFX hardware
3369 can resize a BAR to allow access to all VRAM.
3370 Adding the window is slightly risky (it may
3371 conflict with unreported devices), so this
3373 disable_acs_redir=<pci_dev>[; ...]
3374 Specify one or more PCI devices (in the format
3375 specified above) separated by semicolons.
3376 Each device specified will have the PCI ACS
3377 redirect capabilities forced off which will
3378 allow P2P traffic between devices through
3379 bridges without forcing it upstream. Note:
3380 this removes isolation between devices and
3381 may put more devices in an IOMMU group.
3383 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3386 force Enable ASPM even on devices that claim not to support it.
3387 WARNING: Forcing ASPM on may cause system lockups.
3389 pcie_ports= [PCIE] PCIe port services handling:
3390 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
3391 even if the platform doesn't give the OS permission to
3392 use them. This may cause conflicts if the platform
3393 also tries to use these services.
3394 compat Disable native PCIe services (PME, AER, DPC, PCIe
3397 pcie_port_pm= [PCIE] PCIe port power management handling:
3398 off Disable power management of all PCIe ports
3399 force Forcibly enable power management of all PCIe ports
3401 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3402 nomsi Do not use MSI for native PCIe PME signaling (this makes
3403 all PCIe root ports use INTx for all services).
3405 pcmv= [HW,PCMCIA] BadgePAD 4
3409 Keep all power-domains already enabled by bootloader on,
3410 even if no driver has claimed them. This is useful
3411 for debug and development, but should not be
3412 needed on a platform with proper driver support.
3415 See Documentation/blockdev/paride.txt.
3417 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3420 See arch/parisc/kernel/pdc_chassis.c
3422 percpu_alloc= Select which percpu first chunk allocator to use.
3423 Currently supported values are "embed" and "page".
3424 Archs may support subset or none of the selections.
3425 See comments in mm/percpu.c for details on each
3426 allocator. This parameter is primarily for debugging
3427 and performance comparison.
3430 See Documentation/blockdev/paride.txt.
3433 See Documentation/blockdev/paride.txt.
3435 pirq= [SMP,APIC] Manual mp-table setup
3436 See Documentation/x86/i386/IO-APIC.txt.
3438 plip= [PPT,NET] Parallel port network link
3439 Format: { parport<nr> | timid | 0 }
3440 See also Documentation/admin-guide/parport.rst.
3442 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3443 Override pmtimer IOPort with a hex value.
3447 Enable PNP debug messages (depends on the
3448 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3449 via /sys/module/pnp/parameters/debug. We always show
3450 current resource usage; turning this on also shows
3451 possible settings and some assignment information.
3457 { on | off | curr | res | no-curr | no-res }
3460 [ISAPNP] Exclude IRQs for the autoconfiguration
3463 [ISAPNP] Exclude DMAs for the autoconfiguration
3465 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3466 Ranges are in pairs (I/O port base and size).
3469 [ISAPNP] Exclude memory regions for the
3471 Ranges are in pairs (memory base and size).
3473 ports= [IP_VS_FTP] IPVS ftp helper module
3475 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3477 Format: <port>,<port>....
3479 powersave=off [PPC] This option disables power saving features.
3480 It specifically disables cpuidle and sets the
3481 platform machine description specific power_save
3482 function to NULL. On Idle the CPU just reduces
3485 ppc_strict_facility_enable
3486 [PPC] This option catches any kernel floating point,
3487 Altivec, VSX and SPE outside of regions specifically
3488 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3489 There is some performance impact when enabling this.
3493 Disable Hardware Transactional Memory
3495 print-fatal-signals=
3496 [KNL] debug: print fatal signals
3498 If enabled, warn about various signal handling
3499 related application anomalies: too many signals,
3500 too many POSIX.1 timers, fatal signals causing a
3503 If you hit the warning due to signal overflow,
3504 you might want to try "ulimit -i unlimited".
3508 printk.always_kmsg_dump=
3509 Trigger kmsg_dump for cases other than kernel oops or
3511 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3514 printk.devkmsg={on,off,ratelimit}
3515 Control writing to /dev/kmsg.
3516 on - unlimited logging to /dev/kmsg from userspace
3517 off - logging to /dev/kmsg disabled
3518 ratelimit - ratelimit the logging
3521 printk.time= Show timing data prefixed to each printk message line
3522 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3524 processor.max_cstate= [HW,ACPI]
3525 Limit processor to maximum C-state
3526 max_cstate=9 overrides any DMI blacklist limit.
3528 processor.nocst [HW,ACPI]
3529 Ignore the _CST method to determine C-states,
3530 instead using the legacy FADT method
3532 profile= [KNL] Enable kernel profiling via /proc/profile
3533 Format: [<profiletype>,]<number>
3534 Param: <profiletype>: "schedule", "sleep", or "kvm"
3535 [defaults to kernel profiling]
3536 Param: "schedule" - profile schedule points.
3537 Param: "sleep" - profile D-state sleeping (millisecs).
3538 Requires CONFIG_SCHEDSTATS
3539 Param: "kvm" - profile VM exits.
3540 Param: <number> - step/bucket size as a power of 2 for
3541 statistical time based profiling.
3543 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3545 See Documentation/blockdev/ramdisk.txt.
3547 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3548 probe for; one of (bare|imps|exps|lifebook|any).
3549 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3551 psmouse.resetafter= [HW,MOUSE]
3552 Try to reset the device after so many bad packets
3555 [HW,MOUSE] Set desired mouse resolution, in dpi.
3556 psmouse.smartscroll=
3557 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3558 0 = disabled, 1 = enabled (default).
3560 pstore.backend= Specify the name of the pstore backend to use
3563 See Documentation/blockdev/paride.txt.
3565 pti= [X86_64] Control Page Table Isolation of user and
3566 kernel address spaces. Disabling this feature
3567 removes hardening, but improves performance of
3568 system calls and interrupts.
3570 on - unconditionally enable
3571 off - unconditionally disable
3572 auto - kernel detects whether your CPU model is
3573 vulnerable to issues that PTI mitigates
3575 Not specifying this option is equivalent to pti=auto.
3578 Equivalent to pti=off
3581 [KNL] Number of legacy pty's. Overwrites compiled-in
3584 quiet [KNL] Disable most log messages
3589 See Documentation/admin-guide/md.rst.
3591 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3592 See Documentation/blockdev/ramdisk.txt.
3594 random.trust_cpu={on,off}
3595 [KNL] Enable or disable trusting the use of the
3596 CPU's random number generator (if available) to
3597 fully seed the kernel's CRNG. Default is controlled
3598 by CONFIG_RANDOM_TRUST_CPU.
3600 ras=option[,option,...] [KNL] RAS-specific options
3603 Disable the Correctable Errors Collector,
3604 see CONFIG_RAS_CEC help text.
3607 The argument is a cpu list, as described above.
3609 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3610 the specified list of CPUs to be no-callback CPUs.
3611 Invocation of these CPUs' RCU callbacks will
3612 be offloaded to "rcuox/N" kthreads created for
3613 that purpose, where "x" is "b" for RCU-bh, "p"
3614 for RCU-preempt, and "s" for RCU-sched, and "N"
3615 is the CPU number. This reduces OS jitter on the
3616 offloaded CPUs, which can be useful for HPC and
3617 real-time workloads. It can also improve energy
3618 efficiency for asymmetric multiprocessors.
3621 Rather than requiring that offloaded CPUs
3622 (specified by rcu_nocbs= above) explicitly
3623 awaken the corresponding "rcuoN" kthreads,
3624 make these kthreads poll for callbacks.
3625 This improves the real-time response for the
3626 offloaded CPUs by relieving them of the need to
3627 wake up the corresponding kthread, but degrades
3628 energy efficiency by requiring that the kthreads
3629 periodically wake up to do the polling.
3631 rcutree.blimit= [KNL]
3632 Set maximum number of finished RCU callbacks to
3633 process in one batch.
3635 rcutree.dump_tree= [KNL]
3636 Dump the structure of the rcu_node combining tree
3637 out at early boot. This is used for diagnostic
3638 purposes, to verify correct tree setup.
3640 rcutree.gp_cleanup_delay= [KNL]
3641 Set the number of jiffies to delay each step of
3642 RCU grace-period cleanup.
3644 rcutree.gp_init_delay= [KNL]
3645 Set the number of jiffies to delay each step of
3646 RCU grace-period initialization.
3648 rcutree.gp_preinit_delay= [KNL]
3649 Set the number of jiffies to delay each step of
3650 RCU grace-period pre-initialization, that is,
3651 the propagation of recent CPU-hotplug changes up
3652 the rcu_node combining tree.
3654 rcutree.rcu_fanout_exact= [KNL]
3655 Disable autobalancing of the rcu_node combining
3656 tree. This is used by rcutorture, and might
3657 possibly be useful for architectures having high
3658 cache-to-cache transfer latencies.
3660 rcutree.rcu_fanout_leaf= [KNL]
3661 Change the number of CPUs assigned to each
3662 leaf rcu_node structure. Useful for very
3663 large systems, which will choose the value 64,
3664 and for NUMA systems with large remote-access
3665 latencies, which will choose a value aligned
3666 with the appropriate hardware boundaries.
3668 rcutree.jiffies_till_sched_qs= [KNL]
3669 Set required age in jiffies for a
3670 given grace period before RCU starts
3671 soliciting quiescent-state help from
3672 rcu_note_context_switch().
3674 rcutree.jiffies_till_first_fqs= [KNL]
3675 Set delay from grace-period initialization to
3676 first attempt to force quiescent states.
3677 Units are jiffies, minimum value is zero,
3678 and maximum value is HZ.
3680 rcutree.jiffies_till_next_fqs= [KNL]
3681 Set delay between subsequent attempts to force
3682 quiescent states. Units are jiffies, minimum
3683 value is one, and maximum value is HZ.
3685 rcutree.kthread_prio= [KNL,BOOT]
3686 Set the SCHED_FIFO priority of the RCU per-CPU
3687 kthreads (rcuc/N). This value is also used for
3688 the priority of the RCU boost threads (rcub/N)
3689 and for the RCU grace-period kthreads (rcu_bh,
3690 rcu_preempt, and rcu_sched). If RCU_BOOST is
3691 set, valid values are 1-99 and the default is 1
3692 (the least-favored priority). Otherwise, when
3693 RCU_BOOST is not set, valid values are 0-99 and
3694 the default is zero (non-realtime operation).
3696 rcutree.rcu_nocb_leader_stride= [KNL]
3697 Set the number of NOCB kthread groups, which
3698 defaults to the square root of the number of
3699 CPUs. Larger numbers reduces the wakeup overhead
3700 on the per-CPU grace-period kthreads, but increases
3701 that same overhead on each group's leader.
3703 rcutree.qhimark= [KNL]
3704 Set threshold of queued RCU callbacks beyond which
3705 batch limiting is disabled.
3707 rcutree.qlowmark= [KNL]
3708 Set threshold of queued RCU callbacks below which
3709 batch limiting is re-enabled.
3711 rcutree.rcu_idle_gp_delay= [KNL]
3712 Set wakeup interval for idle CPUs that have
3713 RCU callbacks (RCU_FAST_NO_HZ=y).
3715 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3716 Set wakeup interval for idle CPUs that have
3717 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3718 Lazy RCU callbacks are those which RCU can
3719 prove do nothing more than free memory.
3721 rcutree.rcu_kick_kthreads= [KNL]
3722 Cause the grace-period kthread to get an extra
3723 wake_up() if it sleeps three times longer than
3724 it should at force-quiescent-state time.
3725 This wake_up() will be accompanied by a
3726 WARN_ONCE() splat and an ftrace_dump().
3728 rcuperf.gp_async= [KNL]
3729 Measure performance of asynchronous
3730 grace-period primitives such as call_rcu().
3732 rcuperf.gp_async_max= [KNL]
3733 Specify the maximum number of outstanding
3734 callbacks per writer thread. When a writer
3735 thread exceeds this limit, it invokes the
3736 corresponding flavor of rcu_barrier() to allow
3737 previously posted callbacks to drain.
3739 rcuperf.gp_exp= [KNL]
3740 Measure performance of expedited synchronous
3741 grace-period primitives.
3743 rcuperf.holdoff= [KNL]
3744 Set test-start holdoff period. The purpose of
3745 this parameter is to delay the start of the
3746 test until boot completes in order to avoid
3749 rcuperf.nreaders= [KNL]
3750 Set number of RCU readers. The value -1 selects
3751 N, where N is the number of CPUs. A value
3752 "n" less than -1 selects N-n+1, where N is again
3753 the number of CPUs. For example, -2 selects N
3754 (the number of CPUs), -3 selects N+1, and so on.
3755 A value of "n" less than or equal to -N selects
3758 rcuperf.nwriters= [KNL]
3759 Set number of RCU writers. The values operate
3760 the same as for rcuperf.nreaders.
3761 N, where N is the number of CPUs
3763 rcuperf.perf_type= [KNL]
3764 Specify the RCU implementation to test.
3766 rcuperf.shutdown= [KNL]
3767 Shut the system down after performance tests
3768 complete. This is useful for hands-off automated
3771 rcuperf.verbose= [KNL]
3772 Enable additional printk() statements.
3774 rcuperf.writer_holdoff= [KNL]
3775 Write-side holdoff between grace periods,
3776 in microseconds. The default of zero says
3779 rcutorture.cbflood_inter_holdoff= [KNL]
3780 Set holdoff time (jiffies) between successive
3781 callback-flood tests.
3783 rcutorture.cbflood_intra_holdoff= [KNL]
3784 Set holdoff time (jiffies) between successive
3785 bursts of callbacks within a given callback-flood
3788 rcutorture.cbflood_n_burst= [KNL]
3789 Set the number of bursts making up a given
3790 callback-flood test. Set this to zero to
3791 disable callback-flood testing.
3793 rcutorture.cbflood_n_per_burst= [KNL]
3794 Set the number of callbacks to be registered
3795 in a given burst of a callback-flood test.
3797 rcutorture.fqs_duration= [KNL]
3798 Set duration of force_quiescent_state bursts
3801 rcutorture.fqs_holdoff= [KNL]
3802 Set holdoff time within force_quiescent_state bursts
3805 rcutorture.fqs_stutter= [KNL]
3806 Set wait time between force_quiescent_state bursts
3809 rcutorture.gp_cond= [KNL]
3810 Use conditional/asynchronous update-side
3811 primitives, if available.
3813 rcutorture.gp_exp= [KNL]
3814 Use expedited update-side primitives, if available.
3816 rcutorture.gp_normal= [KNL]
3817 Use normal (non-expedited) asynchronous
3818 update-side primitives, if available.
3820 rcutorture.gp_sync= [KNL]
3821 Use normal (non-expedited) synchronous
3822 update-side primitives, if available. If all
3823 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3824 rcutorture.gp_normal=, and rcutorture.gp_sync=
3825 are zero, rcutorture acts as if is interpreted
3826 they are all non-zero.
3828 rcutorture.n_barrier_cbs= [KNL]
3829 Set callbacks/threads for rcu_barrier() testing.
3831 rcutorture.nfakewriters= [KNL]
3832 Set number of concurrent RCU writers. These just
3833 stress RCU, they don't participate in the actual
3834 test, hence the "fake".
3836 rcutorture.nreaders= [KNL]
3837 Set number of RCU readers. The value -1 selects
3838 N-1, where N is the number of CPUs. A value
3839 "n" less than -1 selects N-n-2, where N is again
3840 the number of CPUs. For example, -2 selects N
3841 (the number of CPUs), -3 selects N+1, and so on.
3843 rcutorture.object_debug= [KNL]
3844 Enable debug-object double-call_rcu() testing.
3846 rcutorture.onoff_holdoff= [KNL]
3847 Set time (s) after boot for CPU-hotplug testing.
3849 rcutorture.onoff_interval= [KNL]
3850 Set time (jiffies) between CPU-hotplug operations,
3851 or zero to disable CPU-hotplug testing.
3853 rcutorture.shuffle_interval= [KNL]
3854 Set task-shuffle interval (s). Shuffling tasks
3855 allows some CPUs to go into dyntick-idle mode
3856 during the rcutorture test.
3858 rcutorture.shutdown_secs= [KNL]
3859 Set time (s) after boot system shutdown. This
3860 is useful for hands-off automated testing.
3862 rcutorture.stall_cpu= [KNL]
3863 Duration of CPU stall (s) to test RCU CPU stall
3864 warnings, zero to disable.
3866 rcutorture.stall_cpu_holdoff= [KNL]
3867 Time to wait (s) after boot before inducing stall.
3869 rcutorture.stall_cpu_irqsoff= [KNL]
3870 Disable interrupts while stalling if set.
3872 rcutorture.stat_interval= [KNL]
3873 Time (s) between statistics printk()s.
3875 rcutorture.stutter= [KNL]
3876 Time (s) to stutter testing, for example, specifying
3877 five seconds causes the test to run for five seconds,
3878 wait for five seconds, and so on. This tests RCU's
3879 ability to transition abruptly to and from idle.
3881 rcutorture.test_boost= [KNL]
3882 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3883 "Maybe" means test if the RCU implementation
3884 under test support RCU priority boosting.
3886 rcutorture.test_boost_duration= [KNL]
3887 Duration (s) of each individual boost test.
3889 rcutorture.test_boost_interval= [KNL]
3890 Interval (s) between each boost test.
3892 rcutorture.test_no_idle_hz= [KNL]
3893 Test RCU's dyntick-idle handling. See also the
3894 rcutorture.shuffle_interval parameter.
3896 rcutorture.torture_type= [KNL]
3897 Specify the RCU implementation to test.
3899 rcutorture.verbose= [KNL]
3900 Enable additional printk() statements.
3902 rcupdate.rcu_cpu_stall_suppress= [KNL]
3903 Suppress RCU CPU stall warning messages.
3905 rcupdate.rcu_cpu_stall_timeout= [KNL]
3906 Set timeout for RCU CPU stall warning messages.
3908 rcupdate.rcu_expedited= [KNL]
3909 Use expedited grace-period primitives, for
3910 example, synchronize_rcu_expedited() instead
3911 of synchronize_rcu(). This reduces latency,
3912 but can increase CPU utilization, degrade
3913 real-time latency, and degrade energy efficiency.
3914 No effect on CONFIG_TINY_RCU kernels.
3916 rcupdate.rcu_normal= [KNL]
3917 Use only normal grace-period primitives,
3918 for example, synchronize_rcu() instead of
3919 synchronize_rcu_expedited(). This improves
3920 real-time latency, CPU utilization, and
3921 energy efficiency, but can expose users to
3922 increased grace-period latency. This parameter
3923 overrides rcupdate.rcu_expedited. No effect on
3924 CONFIG_TINY_RCU kernels.
3926 rcupdate.rcu_normal_after_boot= [KNL]
3927 Once boot has completed (that is, after
3928 rcu_end_inkernel_boot() has been invoked), use
3929 only normal grace-period primitives. No effect
3930 on CONFIG_TINY_RCU kernels.
3932 rcupdate.rcu_task_stall_timeout= [KNL]
3933 Set timeout in jiffies for RCU task stall warning
3934 messages. Disable with a value less than or equal
3937 rcupdate.rcu_self_test= [KNL]
3938 Run the RCU early boot self tests
3940 rcupdate.rcu_self_test_bh= [KNL]
3941 Run the RCU bh early boot self tests
3943 rcupdate.rcu_self_test_sched= [KNL]
3944 Run the RCU sched early boot self tests
3948 Run specified binary instead of /init from the ramdisk,
3949 used for early userspace startup. See initrd.
3952 force - Override the decision by the kernel to hide the
3953 advertisement of RDRAND support (this affects
3954 certain AMD processors because of buggy BIOS
3955 support, specifically around the suspend/resume
3959 Turn on/off individual RDT features. List is:
3960 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
3962 E.g. to turn on cmt and turn off mba use:
3966 Format (x86 or x86_64):
3967 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3969 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3971 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3972 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3973 reboot_force is either force or not specified,
3974 reboot_cpu is s[mp]#### with #### being the processor
3975 to be used for rebooting.
3978 [KNL, SMP] Set scheduler's default relax_domain_level.
3979 See Documentation/cgroup-v1/cpusets.txt.
3981 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
3982 Format: <base1>,<size1>[,<base2>,<size2>,...]
3983 Reserve I/O ports or memory so the kernel won't use
3984 them. If <base> is less than 0x10000, the region
3985 is assumed to be I/O ports; otherwise it is memory.
3987 reservetop= [X86-32]
3989 Reserves a hole at the top of the kernel virtual
3994 Set the amount of memory to reserve for BIOS at
3995 the bottom of the address space.
3997 reset_devices [KNL] Force drivers to reset the underlying device
3998 during initialization.
4001 Specify the partition device for software suspend
4003 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
4005 resume_offset= [SWSUSP]
4006 Specify the offset from the beginning of the partition
4007 given by "resume=" at which the swap header is located,
4008 in <PAGE_SIZE> units (needed only for swap files).
4009 See Documentation/power/swsusp-and-swap-files.txt
4011 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
4012 read the resume files
4014 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
4015 Useful for devices that are detected asynchronously
4016 (e.g. USB and MMC devices).
4018 hibernate= [HIBERNATION]
4019 noresume Don't check if there's a hibernation image
4020 present during boot.
4021 nocompress Don't compress/decompress hibernation images.
4022 no Disable hibernation and resume.
4023 protect_image Turn on image protection during restoration
4024 (that will set all pages holding image data
4025 during restoration read-only).
4027 retain_initrd [RAM] Keep initrd memory after extraction
4029 rfkill.default_state=
4030 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
4031 etc. communication is blocked by default.
4034 rfkill.master_switch_mode=
4035 0 The "airplane mode" button does nothing.
4036 1 The "airplane mode" button toggles between everything
4037 blocked and the previous configuration.
4038 2 The "airplane mode" button toggles between everything
4039 blocked and everything unblocked.
4041 rhash_entries= [KNL,NET]
4042 Set number of hash buckets for route cache
4045 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
4048 ro [KNL] Mount root device read-only on boot
4051 on Mark read-only kernel memory as read-only (default).
4052 off Leave read-only kernel memory writable for debugging.
4055 Enable the uart passthrough on the designated usb port
4056 on Rockchip SoCs. When active, the signals of the
4057 debug-uart get routed to the D+ and D- pins of the usb
4058 port and the regular usb controller gets disabled.
4060 root= [KNL] Root filesystem
4061 See name_to_dev_t comment in init/do_mounts.c.
4063 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
4064 mount the root filesystem
4066 rootflags= [KNL] Set root filesystem mount option string
4068 rootfstype= [KNL] Set root filesystem type
4070 rootwait [KNL] Wait (indefinitely) for root device to show up.
4071 Useful for devices that are detected asynchronously
4072 (e.g. USB and MMC devices).
4074 rproc_mem=nn[KMG][@address]
4075 [KNL,ARM,CMA] Remoteproc physical memory block.
4076 Memory area to be used by remote processor image,
4079 rw [KNL] Mount root device read-write on boot
4081 S [KNL] Run init in single mode
4083 s390_iommu= [HW,S390]
4084 Set s390 IOTLB flushing mode
4086 With strict flushing every unmap operation will result in
4087 an IOTLB flush. Default is lazy flushing before reuse,
4091 See drivers/net/irda/sa1100_ir.c.
4093 sbni= [NET] Granch SBNI12 leased line adapter
4095 sched_debug [KNL] Enables verbose scheduler debug messages.
4097 schedstats= [KNL,X86] Enable or disable scheduled statistics.
4098 Allowed values are enable and disable. This feature
4099 incurs a small amount of overhead in the scheduler
4100 but is useful for debugging and performance tuning.
4102 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
4103 xtime_lock contention on larger systems, and/or RCU lock
4104 contention on all systems with CONFIG_MAXSMP set.
4105 Format: { "0" | "1" }
4106 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
4108 Note: increases power consumption, thus should only be
4109 enabled if running jitter sensitive (HPC/RT) workloads.
4111 security= [SECURITY] Choose a security module to enable at boot.
4112 If this boot parameter is not specified, only the first
4113 security module asking for security registration will be
4114 loaded. An invalid security module name will be treated
4115 as if no module has been chosen.
4117 selinux= [SELINUX] Disable or enable SELinux at boot time.
4118 Format: { "0" | "1" }
4119 See security/selinux/Kconfig help text.
4122 Default value is set via kernel config option.
4123 If enabled at boot time, /selinux/disable can be used
4124 later to disable prior to initial policy load.
4126 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
4127 Format: { "0" | "1" }
4128 See security/apparmor/Kconfig help text
4131 Default value is set via kernel config option.
4133 serialnumber [BUGS=X86-32]
4136 Maximal number of shapers.
4144 Disable merging of slabs with similar size. May be
4145 necessary if there is some reason to distinguish
4146 allocs to different slabs, especially in hardened
4147 environments where the risk of heap overflows and
4148 layout control by attackers can usually be
4149 frustrated by disabling merging. This will reduce
4150 most of the exposure of a heap attack to a single
4151 cache (risks via metadata attacks are mostly
4152 unchanged). Debug options disable merging on their
4154 For more information see Documentation/vm/slub.rst.
4156 slab_max_order= [MM, SLAB]
4157 Determines the maximum allowed order for slabs.
4158 A high setting may cause OOMs due to memory
4159 fragmentation. Defaults to 1 for systems with
4160 more than 32MB of RAM, 0 otherwise.
4162 slub_debug[=options[,slabs]] [MM, SLUB]
4163 Enabling slub_debug allows one to determine the
4164 culprit if slab objects become corrupted. Enabling
4165 slub_debug can create guard zones around objects and
4166 may poison objects when not in use. Also tracks the
4167 last alloc / free. For more information see
4168 Documentation/vm/slub.rst.
4170 slub_memcg_sysfs= [MM, SLUB]
4171 Determines whether to enable sysfs directories for
4172 memory cgroup sub-caches. 1 to enable, 0 to disable.
4173 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
4174 Enabling this can lead to a very high number of debug
4175 directories and files being created under
4178 slub_max_order= [MM, SLUB]
4179 Determines the maximum allowed order for slabs.
4180 A high setting may cause OOMs due to memory
4181 fragmentation. For more information see
4182 Documentation/vm/slub.rst.
4184 slub_min_objects= [MM, SLUB]
4185 The minimum number of objects per slab. SLUB will
4186 increase the slab order up to slub_max_order to
4187 generate a sufficiently large slab able to contain
4188 the number of objects indicated. The higher the number
4189 of objects the smaller the overhead of tracking slabs
4190 and the less frequently locks need to be acquired.
4191 For more information see Documentation/vm/slub.rst.
4193 slub_min_order= [MM, SLUB]
4194 Determines the minimum page order for slabs. Must be
4195 lower than slub_max_order.
4196 For more information see Documentation/vm/slub.rst.
4198 slub_nomerge [MM, SLUB]
4199 Same with slab_nomerge. This is supported for legacy.
4200 See slab_nomerge for more information.
4203 Format: <io1>[,<io2>[,...,<io8>]]
4205 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
4206 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
4207 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
4208 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
4209 smsc-ircc2.ircc_irq= [HW] IRQ line
4210 smsc-ircc2.ircc_dma= [HW] DMA channel
4211 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
4212 0: Toshiba Satellite 1800 (GP data pin select)
4213 1: Fast pin select (default)
4216 smt [KNL,S390] Set the maximum number of threads (logical
4217 CPUs) to use per physical CPU on systems capable of
4218 symmetric multithreading (SMT). Will be capped to the
4219 actual hardware limit.
4221 Default: -1 (no limit)
4224 [KNL] Should the soft-lockup detector generate panics.
4227 A nonzero value instructs the soft-lockup detector
4228 to panic the machine when a soft-lockup occurs. This
4229 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
4230 which is the respective build-time switch to that
4233 softlockup_all_cpu_backtrace=
4234 [KNL] Should the soft-lockup detector generate
4235 backtraces on all cpus.
4238 sonypi.*= [HW] Sony Programmable I/O Control Device driver
4239 See Documentation/laptops/sonypi.txt
4241 spectre_v2= [X86] Control mitigation of Spectre variant 2
4242 (indirect branch speculation) vulnerability.
4243 The default operation protects the kernel from
4246 on - unconditionally enable, implies
4248 off - unconditionally disable, implies
4250 auto - kernel detects whether your CPU model is
4253 Selecting 'on' will, and 'auto' may, choose a
4254 mitigation method at run time according to the
4255 CPU, the available microcode, the setting of the
4256 CONFIG_RETPOLINE configuration option, and the
4257 compiler with which the kernel was built.
4259 Selecting 'on' will also enable the mitigation
4260 against user space to user space task attacks.
4262 Selecting 'off' will disable both the kernel and
4263 the user space protections.
4265 Specific mitigations can also be selected manually:
4267 retpoline - replace indirect branches
4268 retpoline,generic - google's original retpoline
4269 retpoline,amd - AMD-specific minimal thunk
4271 Not specifying this option is equivalent to
4275 [X86] Control mitigation of Spectre variant 2
4276 (indirect branch speculation) vulnerability between
4279 on - Unconditionally enable mitigations. Is
4280 enforced by spectre_v2=on
4282 off - Unconditionally disable mitigations. Is
4283 enforced by spectre_v2=off
4285 prctl - Indirect branch speculation is enabled,
4286 but mitigation can be enabled via prctl
4287 per thread. The mitigation control state
4288 is inherited on fork.
4291 - Like "prctl" above, but only STIBP is
4292 controlled per thread. IBPB is issued
4293 always when switching between different user
4297 - Same as "prctl" above, but all seccomp
4298 threads will enable the mitigation unless
4299 they explicitly opt out.
4302 - Like "seccomp" above, but only STIBP is
4303 controlled per thread. IBPB is issued
4304 always when switching between different
4305 user space processes.
4307 auto - Kernel selects the mitigation depending on
4308 the available CPU features and vulnerability.
4311 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
4313 Not specifying this option is equivalent to
4314 spectre_v2_user=auto.
4316 spec_store_bypass_disable=
4317 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
4318 (Speculative Store Bypass vulnerability)
4320 Certain CPUs are vulnerable to an exploit against a
4321 a common industry wide performance optimization known
4322 as "Speculative Store Bypass" in which recent stores
4323 to the same memory location may not be observed by
4324 later loads during speculative execution. The idea
4325 is that such stores are unlikely and that they can
4326 be detected prior to instruction retirement at the
4327 end of a particular speculation execution window.
4329 In vulnerable processors, the speculatively forwarded
4330 store can be used in a cache side channel attack, for
4331 example to read memory to which the attacker does not
4332 directly have access (e.g. inside sandboxed code).
4334 This parameter controls whether the Speculative Store
4335 Bypass optimization is used.
4337 On x86 the options are:
4339 on - Unconditionally disable Speculative Store Bypass
4340 off - Unconditionally enable Speculative Store Bypass
4341 auto - Kernel detects whether the CPU model contains an
4342 implementation of Speculative Store Bypass and
4343 picks the most appropriate mitigation. If the
4344 CPU is not vulnerable, "off" is selected. If the
4345 CPU is vulnerable the default mitigation is
4346 architecture and Kconfig dependent. See below.
4347 prctl - Control Speculative Store Bypass per thread
4348 via prctl. Speculative Store Bypass is enabled
4349 for a process by default. The state of the control
4350 is inherited on fork.
4351 seccomp - Same as "prctl" above, but all seccomp threads
4352 will disable SSB unless they explicitly opt out.
4354 Default mitigations:
4355 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
4357 On powerpc the options are:
4359 on,auto - On Power8 and Power9 insert a store-forwarding
4360 barrier on kernel entry and exit. On Power7
4361 perform a software flush on kernel entry and
4365 Not specifying this option is equivalent to
4366 spec_store_bypass_disable=auto.
4368 spia_io_base= [HW,MTD]
4373 srcutree.counter_wrap_check [KNL]
4374 Specifies how frequently to check for
4375 grace-period sequence counter wrap for the
4376 srcu_data structure's ->srcu_gp_seq_needed field.
4377 The greater the number of bits set in this kernel
4378 parameter, the less frequently counter wrap will
4379 be checked for. Note that the bottom two bits
4382 srcutree.exp_holdoff [KNL]
4383 Specifies how many nanoseconds must elapse
4384 since the end of the last SRCU grace period for
4385 a given srcu_struct until the next normal SRCU
4386 grace period will be considered for automatic
4387 expediting. Set to zero to disable automatic
4391 Speculative Store Bypass Disable control
4393 On CPUs that are vulnerable to the Speculative
4394 Store Bypass vulnerability and offer a
4395 firmware based mitigation, this parameter
4396 indicates how the mitigation should be used:
4398 force-on: Unconditionally enable mitigation for
4399 for both kernel and userspace
4400 force-off: Unconditionally disable mitigation for
4401 for both kernel and userspace
4402 kernel: Always enable mitigation in the
4403 kernel, and offer a prctl interface
4404 to allow userspace to register its
4405 interest in being mitigated too.
4407 stack_guard_gap= [MM]
4408 override the default stack gap protection. The value
4409 is in page units and it defines how many pages prior
4410 to (for stacks growing down) resp. after (for stacks
4411 growing up) the main stack are reserved for no other
4412 mapping. Default value is 256 pages.
4415 Enabled the stack tracer on boot up.
4417 stacktrace_filter=[function-list]
4418 [FTRACE] Limit the functions that the stack tracer
4419 will trace at boot up. function-list is a comma separated
4420 list of functions. This list can be changed at run
4421 time by the stack_trace_filter file in the debugfs
4422 tracing directory. Note, this enables stack tracing
4423 and the stacktrace above is not needed.
4427 Set the STI (builtin display/keyboard on the HP-PARISC
4428 machines) console (graphic card) which should be used
4429 as the initial boot-console.
4430 See also comment in drivers/video/console/sticore.c.
4433 See comment in drivers/video/console/sticore.c.
4436 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4438 sunrpc.min_resvport=
4439 sunrpc.max_resvport=
4441 SunRPC servers often require that client requests
4442 originate from a privileged port (i.e. a port in the
4443 range 0 < portnr < 1024).
4444 An administrator who wishes to reserve some of these
4445 ports for other uses may adjust the range that the
4446 kernel's sunrpc client considers to be privileged
4447 using these two parameters to set the minimum and
4448 maximum port values.
4450 sunrpc.svc_rpc_per_connection_limit=
4452 Limit the number of requests that the server will
4453 process in parallel from a single connection.
4454 The default value is 0 (no limit).
4458 Control how the NFS server code allocates CPUs to
4459 service thread pools. Depending on how many NICs
4460 you have and where their interrupts are bound, this
4461 option will affect which CPUs will do NFS serving.
4462 Note: this parameter cannot be changed while the
4463 NFS server is running.
4465 auto the server chooses an appropriate mode
4466 automatically using heuristics
4467 global a single global pool contains all CPUs
4468 percpu one pool for each CPU
4469 pernode one pool for each NUMA node (equivalent
4470 to global on non-NUMA machines)
4472 sunrpc.tcp_slot_table_entries=
4473 sunrpc.udp_slot_table_entries=
4475 Sets the upper limit on the number of simultaneous
4476 RPC calls that can be sent from the client to a
4477 server. Increasing these values may allow you to
4478 improve throughput, but will also increase the
4479 amount of memory reserved for use by the client.
4481 suspend.pm_test_delay=
4483 Sets the number of seconds to remain in a suspend test
4484 mode before resuming the system (see
4485 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4486 is set. Default value is 5.
4489 [KNL] Enable accounting of swap in memory resource
4490 controller if no parameter or 1 is given or disable
4491 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4493 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4494 Format: { <int> | force | noforce }
4495 <int> -- Number of I/O TLB slabs
4496 force -- force using of bounce buffers even if they
4497 wouldn't be automatically used by the kernel
4498 noforce -- Never use bounce buffers (for debugging)
4502 sysfs.deprecated=0|1 [KNL]
4503 Enable/disable old style sysfs layout for old udev
4504 on older distributions. When this option is enabled
4505 very new udev will not work anymore. When this option
4506 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4507 in older udev will not work anymore.
4508 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4509 the kernel configuration.
4511 sysrq_always_enabled
4513 Ignore sysrq setting - this boot parameter will
4514 neutralize any effect of /proc/sys/kernel/sysrq.
4515 Useful for debugging.
4517 tcpmhash_entries= [KNL,NET]
4518 Set the number of tcp_metrics_hash slots.
4519 Default value is 8192 or 16384 depending on total
4520 ram pages. This is used to specify the TCP metrics
4521 cache size. See Documentation/networking/ip-sysctl.txt
4522 "tcp_no_metrics_save" section for more details.
4526 test_suspend= [SUSPEND][,N]
4527 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4528 standby suspend) or "freeze" (for suspend type freeze)
4529 as the system sleep state during system startup with
4530 the optional capability to repeat N number of times.
4531 The system is woken from this state using a
4532 wakeup-capable RTC alarm.
4534 thash_entries= [KNL,NET]
4535 Set number of hash buckets for TCP connection
4537 thermal.act= [HW,ACPI]
4538 -1: disable all active trip points in all thermal zones
4539 <degrees C>: override all lowest active trip points
4541 thermal.crt= [HW,ACPI]
4542 -1: disable all critical trip points in all thermal zones
4543 <degrees C>: override all critical trip points
4545 thermal.nocrt= [HW,ACPI]
4546 Set to disable actions on ACPI thermal zone
4547 critical and hot trip points.
4549 thermal.off= [HW,ACPI]
4550 1: disable ACPI thermal control
4552 thermal.psv= [HW,ACPI]
4553 -1: disable all passive trip points
4554 <degrees C>: override all passive trip points to this
4557 thermal.tzp= [HW,ACPI]
4558 Specify global default ACPI thermal zone polling rate
4559 <deci-seconds>: poll all this frequency
4560 0: no polling (default)
4563 Force threading of all interrupt handlers except those
4564 marked explicitly IRQF_NO_THREAD.
4567 Enable the Transcendent memory driver if built-in.
4569 tmem.cleancache=0|1 [KNL, XEN]
4570 Default is on (1). Disable the usage of the cleancache
4571 API to send anonymous pages to the hypervisor.
4573 tmem.frontswap=0|1 [KNL, XEN]
4574 Default is on (1). Disable the usage of the frontswap
4575 API to send swap pages to the hypervisor. If disabled
4576 the selfballooning and selfshrinking are force disabled.
4578 tmem.selfballooning=0|1 [KNL, XEN]
4579 Default is on (1). Disable the driving of swap pages
4582 tmem.selfshrinking=0|1 [KNL, XEN]
4583 Default is on (1). Partial swapoff that immediately
4584 transfers pages from Xen hypervisor back to the
4585 kernel based on different criteria.
4589 Specify if the kernel should make use of the cpu
4590 topology information if the hardware supports this.
4591 The scheduler will make use of this information and
4592 e.g. base its process migration decisions on it.
4595 topology_updates= [KNL, PPC, NUMA]
4597 Specify if the kernel should ignore (off)
4598 topology updates sent by the hypervisor to this
4603 tpm_suspend_pcr=[HW,TPM]
4604 Format: integer pcr id
4605 Specify that at suspend time, the tpm driver
4606 should extend the specified pcr with zeros,
4607 as a workaround for some chips which fail to
4608 flush the last written pcr on TPM_SaveState.
4609 This will guarantee that all the other pcrs
4612 trace_buf_size=nn[KMG]
4613 [FTRACE] will set tracing buffer size on each cpu.
4615 trace_event=[event-list]
4616 [FTRACE] Set and start specified trace events in order
4617 to facilitate early boot debugging. The event-list is a
4618 comma separated list of trace events to enable. See
4619 also Documentation/trace/events.rst
4621 trace_options=[option-list]
4622 [FTRACE] Enable or disable tracer options at boot.
4623 The option-list is a comma delimited list of options
4624 that can be enabled or disabled just as if you were
4625 to echo the option name into
4627 /sys/kernel/debug/tracing/trace_options
4629 For example, to enable stacktrace option (to dump the
4630 stack trace of each event), add to the command line:
4632 trace_options=stacktrace
4634 See also Documentation/trace/ftrace.rst "trace options"
4638 Have the tracepoints sent to printk as well as the
4639 tracing ring buffer. This is useful for early boot up
4640 where the system hangs or reboots and does not give the
4641 option for reading the tracing buffer or performing a
4642 ftrace_dump_on_oops.
4644 To turn off having tracepoints sent to printk,
4645 echo 0 > /proc/sys/kernel/tracepoint_printk
4646 Note, echoing 1 into this file without the
4647 tracepoint_printk kernel cmdline option has no effect.
4651 Having tracepoints sent to printk() and activating high
4652 frequency tracepoints such as irq or sched, can cause
4653 the system to live lock.
4656 [FTRACE] enable this option to disable tracing when a
4657 warning is hit. This turns off "tracing_on". Tracing can
4658 be enabled again by echoing '1' into the "tracing_on"
4659 file located in /sys/kernel/debug/tracing/
4661 This option is useful, as it disables the trace before
4662 the WARNING dump is called, which prevents the trace to
4663 be filled with content caused by the warning output.
4665 This option can also be set at run time via the sysctl
4666 option: kernel/traceoff_on_warning
4668 transparent_hugepage=
4670 Format: [always|madvise|never]
4671 Can be used to control the default behavior of the system
4672 with respect to transparent hugepages.
4673 See Documentation/admin-guide/mm/transhuge.rst
4676 tsc= Disable clocksource stability checks for TSC.
4678 [x86] reliable: mark tsc clocksource as reliable, this
4679 disables clocksource verification at runtime, as well
4680 as the stability checks done at bootup. Used to enable
4681 high-resolution timer mode on older hardware, and in
4682 virtualized environment.
4683 [x86] noirqtime: Do not use TSC to do irq accounting.
4684 Used to run time disable IRQ_TIME_ACCOUNTING on any
4685 platforms where RDTSC is slow and this accounting
4687 [x86] unstable: mark the TSC clocksource as unstable, this
4688 marks the TSC unconditionally unstable at bootup and
4689 avoids any further wobbles once the TSC watchdog notices.
4691 turbografx.map[2|3]= [HW,JOY]
4692 TurboGraFX parallel port interface
4694 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4695 See also Documentation/input/devices/joystick-parport.rst
4697 udbg-immortal [PPC] When debugging early kernel crashes that
4698 happen after console_init() and before a proper
4699 console driver takes over, this boot options might
4700 help "seeing" what's going on.
4702 uhash_entries= [KNL,NET]
4703 Set number of hash buckets for UDP/UDP-Lite connections
4706 [USB] Ignore overcurrent events (default N).
4707 Some badly-designed motherboards generate lots of
4708 bogus events, for ports that aren't wired to
4709 anything. Set this parameter to avoid log spamming.
4710 Note that genuine overcurrent events won't be
4714 [X86] Cause panic on unknown NMI.
4716 usbcore.authorized_default=
4717 [USB] Default USB device authorization:
4718 (default -1 = authorized except for wireless USB,
4719 0 = not authorized, 1 = authorized)
4721 usbcore.autosuspend=
4722 [USB] The autosuspend time delay (in seconds) used
4723 for newly-detected USB devices (default 2). This
4724 is the time required before an idle device will be
4725 autosuspended. Devices for which the delay is set
4726 to a negative value won't be autosuspended at all.
4728 usbcore.usbfs_snoop=
4729 [USB] Set to log all usbfs traffic (default 0 = off).
4731 usbcore.usbfs_snoop_max=
4732 [USB] Maximum number of bytes to snoop in each URB
4735 usbcore.blinkenlights=
4736 [USB] Set to cycle leds on hubs (default 0 = off).
4738 usbcore.old_scheme_first=
4739 [USB] Start with the old device initialization
4740 scheme (default 0 = off).
4742 usbcore.usbfs_memory_mb=
4743 [USB] Memory limit (in MB) for buffers allocated by
4744 usbfs (default = 16, 0 = max = 2047).
4746 usbcore.use_both_schemes=
4747 [USB] Try the other device initialization scheme
4748 if the first one fails (default 1 = enabled).
4750 usbcore.initial_descriptor_timeout=
4751 [USB] Specifies timeout for the initial 64-byte
4752 USB_REQ_GET_DESCRIPTOR request in milliseconds
4753 (default 5000 = 5.0 seconds).
4755 usbcore.nousb [USB] Disable the USB subsystem
4758 [USB] A list of quirk entries to augment the built-in
4759 usb core quirk list. List entries are separated by
4760 commas. Each entry has the form
4761 VendorID:ProductID:Flags. The IDs are 4-digit hex
4762 numbers and Flags is a set of letters. Each letter
4763 will change the built-in quirk; setting it if it is
4764 clear and clearing it if it is set. The letters have
4765 the following meanings:
4766 a = USB_QUIRK_STRING_FETCH_255 (string
4767 descriptors must not be fetched using
4769 b = USB_QUIRK_RESET_RESUME (device can't resume
4770 correctly so reset it instead);
4771 c = USB_QUIRK_NO_SET_INTF (device can't handle
4772 Set-Interface requests);
4773 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
4774 handle its Configuration or Interface
4776 e = USB_QUIRK_RESET (device can't be reset
4777 (e.g morph devices), don't use reset);
4778 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
4779 more interface descriptions than the
4780 bNumInterfaces count, and can't handle
4781 talking to these interfaces);
4782 g = USB_QUIRK_DELAY_INIT (device needs a pause
4783 during initialization, after we read
4784 the device descriptor);
4785 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
4786 high speed and super speed interrupt
4787 endpoints, the USB 2.0 and USB 3.0 spec
4788 require the interval in microframes (1
4789 microframe = 125 microseconds) to be
4790 calculated as interval = 2 ^
4792 Devices with this quirk report their
4793 bInterval as the result of this
4794 calculation instead of the exponent
4795 variable used in the calculation);
4796 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
4797 handle device_qualifier descriptor
4799 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
4800 generates spurious wakeup, ignore
4801 remote wakeup capability);
4802 k = USB_QUIRK_NO_LPM (device can't handle Link
4804 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
4805 (Device reports its bInterval as linear
4806 frames instead of the USB 2.0
4808 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
4809 to be disconnected before suspend to
4810 prevent spurious wakeup);
4811 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
4812 pause after every control message);
4813 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
4814 delay after resetting its port);
4815 Example: quirks=0781:5580:bk,0a5c:5834:gij
4818 [USBHID] The interval which mice are to be polled at.
4821 [USBHID] The interval which joysticks are to be polled at.
4824 [USBHID] The interval which keyboards are to be polled at.
4826 usb-storage.delay_use=
4827 [UMS] The delay in seconds before a new device is
4828 scanned for Logical Units (default 1).
4831 [UMS] A list of quirks entries to supplement or
4832 override the built-in unusual_devs list. List
4833 entries are separated by commas. Each entry has
4834 the form VID:PID:Flags where VID and PID are Vendor
4835 and Product ID values (4-digit hex numbers) and
4836 Flags is a set of characters, each corresponding
4837 to a common usb-storage quirk flag as follows:
4838 a = SANE_SENSE (collect more than 18 bytes
4840 b = BAD_SENSE (don't collect more than 18
4841 bytes of sense data);
4842 c = FIX_CAPACITY (decrease the reported
4843 device capacity by one sector);
4844 d = NO_READ_DISC_INFO (don't use
4845 READ_DISC_INFO command);
4846 e = NO_READ_CAPACITY_16 (don't use
4847 READ_CAPACITY_16 command);
4848 f = NO_REPORT_OPCODES (don't use report opcodes
4850 g = MAX_SECTORS_240 (don't transfer more than
4851 240 sectors at a time, uas only);
4852 h = CAPACITY_HEURISTICS (decrease the
4853 reported device capacity by one
4854 sector if the number is odd);
4855 i = IGNORE_DEVICE (don't bind to this
4857 j = NO_REPORT_LUNS (don't use report luns
4859 l = NOT_LOCKABLE (don't try to lock and
4860 unlock ejectable media);
4861 m = MAX_SECTORS_64 (don't transfer more
4862 than 64 sectors = 32 KB at a time);
4863 n = INITIAL_READ10 (force a retry of the
4864 initial READ(10) command);
4865 o = CAPACITY_OK (accept the capacity
4866 reported by the device);
4867 p = WRITE_CACHE (the device cache is ON
4869 r = IGNORE_RESIDUE (the device reports
4870 bogus residue values);
4871 s = SINGLE_LUN (the device has only one
4873 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4874 commands, uas only);
4875 u = IGNORE_UAS (don't bind to the uas driver);
4876 w = NO_WP_DETECT (don't test whether the
4877 medium is write-protected).
4878 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4879 even if the device claims no cache)
4880 Example: quirks=0419:aaf5:rl,0421:0433:rc
4882 user_debug= [KNL,ARM]
4884 See arch/arm/Kconfig.debug help text.
4885 1 - undefined instruction events
4887 4 - invalid data aborts
4890 Example: user_debug=31
4893 [X86] Flags controlling user PTE allocations.
4895 nohigh = do not allocate PTE pages in
4896 HIGHMEM regardless of setting
4900 On X86_32, this is an alias for vdso32=. Otherwise:
4902 vdso=1: enable VDSO (the default)
4903 vdso=0: disable VDSO mapping
4905 vdso32= [X86] Control the 32-bit vDSO
4906 vdso32=1: enable 32-bit VDSO
4907 vdso32=0 or vdso32=2: disable 32-bit VDSO
4909 See the help text for CONFIG_COMPAT_VDSO for more
4910 details. If CONFIG_COMPAT_VDSO is set, the default is
4911 vdso32=0; otherwise, the default is vdso32=1.
4913 For compatibility with older kernels, vdso32=2 is an
4916 Try vdso32=0 if you encounter an error that says:
4917 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4920 vector=percpu: enable percpu vector domain
4922 video= [FB] Frame buffer configuration
4923 See Documentation/fb/modedb.txt.
4925 video.brightness_switch_enabled= [0,1]
4926 If set to 1, on receiving an ACPI notify event
4927 generated by hotkey, video driver will adjust brightness
4928 level and then send out the event to user space through
4929 the allocated input device; If set to 0, video driver
4930 will only send out the event without touching backlight
4935 [VMMIO] Memory mapped virtio (platform) device.
4937 <size>@<baseaddr>:<irq>[:<id>]
4939 <size> := size (can use standard suffixes
4941 <baseaddr> := physical base address
4942 <irq> := interrupt number (as passed to
4944 <id> := (optional) platform device id
4946 virtio_mmio.device=1K@0x100b0000:48:7
4948 Can be used multiple times for multiple devices.
4950 vga= [BOOT,X86-32] Select a particular video mode
4951 See Documentation/x86/boot.txt and
4952 Documentation/svga.txt.
4953 Use vga=ask for menu.
4954 This is actually a boot loader parameter; the value is
4955 passed to the kernel using a special protocol.
4957 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4958 size of <nn>. This can be used to increase the
4959 minimum size (128MB on x86). It can also be used to
4960 decrease the size and leave more room for directly
4963 vmcp_cma=nn[MG] [KNL,S390]
4964 Sets the memory size reserved for contiguous memory
4965 allocations for the vmcp device driver.
4967 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4970 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4973 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4977 Controls the behavior of vsyscalls (i.e. calls to
4978 fixed addresses of 0xffffffffff600x00 from legacy
4979 code). Most statically-linked binaries and older
4980 versions of glibc use these calls. Because these
4981 functions are at fixed addresses, they make nice
4982 targets for exploits that can control RIP.
4984 emulate [default] Vsyscalls turn into traps and are
4985 emulated reasonably safely.
4987 none Vsyscalls don't work at all. This makes
4988 them quite hard to use for exploits but
4989 might break your system.
4991 vt.color= [VT] Default text color.
4992 Format: 0xYX, X = foreground, Y = background.
4993 Default: 0x07 = light gray on black.
4995 vt.cur_default= [VT] Default cursor shape.
4996 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4997 the parameters of the <Esc>[?A;B;Cc escape sequence;
4998 see VGA-softcursor.txt. Default: 2 = underline.
5000 vt.default_blu= [VT]
5001 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
5002 Change the default blue palette of the console.
5003 This is a 16-member array composed of values
5006 vt.default_grn= [VT]
5007 Format: <green0>,<green1>,<green2>,...,<green15>
5008 Change the default green palette of the console.
5009 This is a 16-member array composed of values
5012 vt.default_red= [VT]
5013 Format: <red0>,<red1>,<red2>,...,<red15>
5014 Change the default red palette of the console.
5015 This is a 16-member array composed of values
5021 Set system-wide default UTF-8 mode for all tty's.
5022 Default is 1, i.e. UTF-8 mode is enabled for all
5023 newly opened terminals.
5025 vt.global_cursor_default=
5028 Set system-wide default for whether a cursor
5029 is shown on new VTs. Default is -1,
5030 i.e. cursors will be created by default unless
5031 overridden by individual drivers. 0 will hide
5032 cursors, 1 will display them.
5034 vt.italic= [VT] Default color for italic text; 0-15.
5037 vt.underline= [VT] Default color for underlined text; 0-15.
5040 watchdog timers [HW,WDT] For information on watchdog timers,
5041 see Documentation/watchdog/watchdog-parameters.txt
5042 or other driver-specific files in the
5043 Documentation/watchdog/ directory.
5045 workqueue.watchdog_thresh=
5046 If CONFIG_WQ_WATCHDOG is configured, workqueue can
5047 warn stall conditions and dump internal state to
5048 help debugging. 0 disables workqueue stall
5049 detection; otherwise, it's the stall threshold
5050 duration in seconds. The default value is 30 and
5051 it can be updated at runtime by writing to the
5052 corresponding sysfs file.
5054 workqueue.disable_numa
5055 By default, all work items queued to unbound
5056 workqueues are affine to the NUMA nodes they're
5057 issued on, which results in better behavior in
5058 general. If NUMA affinity needs to be disabled for
5059 whatever reason, this option can be used. Note
5060 that this also can be controlled per-workqueue for
5061 workqueues visible under /sys/bus/workqueue/.
5063 workqueue.power_efficient
5064 Per-cpu workqueues are generally preferred because
5065 they show better performance thanks to cache
5066 locality; unfortunately, per-cpu workqueues tend to
5067 be more power hungry than unbound workqueues.
5069 Enabling this makes the per-cpu workqueues which
5070 were observed to contribute significantly to power
5071 consumption unbound, leading to measurably lower
5072 power usage at the cost of small performance
5075 The default value of this parameter is determined by
5076 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
5078 workqueue.debug_force_rr_cpu
5079 Workqueue used to implicitly guarantee that work
5080 items queued without explicit CPU specified are put
5081 on the local CPU. This guarantee is no longer true
5082 and while local CPU is still preferred work items
5083 may be put on foreign CPUs. This debug option
5084 forces round-robin CPU selection to flush out
5085 usages which depend on the now broken guarantee.
5086 When enabled, memory and cache locality will be
5089 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
5090 default x2apic cluster mode on platforms
5093 x86_intel_mid_timer= [X86-32,APBT]
5094 Choose timer option for x86 Intel MID platform.
5095 Two valid options are apbt timer only and lapic timer
5096 plus one apbt timer for broadcast timer.
5097 x86_intel_mid_timer=apbt_only | lapic_and_apbt
5099 xen_512gb_limit [KNL,X86-64,XEN]
5100 Restricts the kernel running paravirtualized under Xen
5101 to use only up to 512 GB of RAM. The reason to do so is
5102 crash analysis tools and Xen tools for doing domain
5103 save/restore/migration must be enabled to handle larger
5106 xen_emul_unplug= [HW,X86,XEN]
5107 Unplug Xen emulated devices
5108 Format: [unplug0,][unplug1]
5109 ide-disks -- unplug primary master IDE devices
5110 aux-ide-disks -- unplug non-primary-master IDE devices
5111 nics -- unplug network devices
5112 all -- unplug all emulated devices (NICs and IDE disks)
5113 unnecessary -- unplugging emulated devices is
5114 unnecessary even if the host did not respond to
5116 never -- do not unplug even if version check succeeds
5118 xen_nopvspin [X86,XEN]
5119 Disables the ticketlock slowpath using Xen PV
5123 Disables the PV optimizations forcing the HVM guest to
5124 run as generic HVM guest with no PV drivers.
5126 xen_scrub_pages= [XEN]
5127 Boolean option to control scrubbing pages before giving them back
5128 to Xen, for use by other domains. Can be also changed at runtime
5129 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
5130 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
5132 xirc2ps_cs= [NET,PCMCIA]
5134 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
5136 xhci-hcd.quirks [USB,KNL]
5137 A hex value specifying bitmask with supplemental xhci
5138 host controller quirks. Meaning of each bit can be
5139 consulted in header drivers/usb/host/xhci.h.
projects / platform / kernel / linux-rpi.git / blob