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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3474
1 files changed, 2685 insertions, 789 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ade4e6ec23e0..31b3a25680d0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1,17 +1,28 @@
- acpi= [HW,ACPI,X86,ARM64]
+ accept_memory= [MM]
+ Format: { eager | lazy }
+ default: lazy
+ By default, unaccepted memory is accepted lazily to
+ avoid prolonged boot times. The lazy option will add
+ some runtime overhead until all memory is eventually
+ accepted. In most cases the overhead is negligible.
+ For some workloads or for debugging purposes
+ accept_memory=eager can be used to accept all memory
+ at once during boot.
+
+ acpi= [HW,ACPI,X86,ARM64,RISCV64]
Advanced Configuration and Power Interface
Format: { force | on | off | strict | noirq | rsdt |
copy_dsdt }
force -- enable ACPI if default was off
- on -- enable ACPI but allow fallback to DT [arm64]
+ on -- enable ACPI but allow fallback to DT [arm64,riscv64]
off -- disable ACPI if default was on
noirq -- do not use ACPI for IRQ routing
strict -- Be less tolerant of platforms that are not
strictly ACPI specification compliant.
rsdt -- prefer RSDT over (default) XSDT
copy_dsdt -- copy DSDT to memory
- For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
- are available
+ For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or
+ "acpi=force" are available
See also Documentation/power/runtime_pm.rst, pci=noacpi
@@ -22,11 +33,13 @@
default: 0
acpi_backlight= [HW,ACPI]
- acpi_backlight=vendor
- acpi_backlight=video
- If set to vendor, prefer vendor specific driver
+ { vendor | video | native | none }
+ If set to vendor, prefer vendor-specific driver
(e.g. thinkpad_acpi, sony_acpi, etc.) instead
of the ACPI video.ko driver.
+ If set to video, use the ACPI video.ko driver.
+ If set to native, use the device's native backlight mode.
+ If set to none, disable the ACPI backlight interface.
acpi_force_32bit_fadt_addr
force FADT to use 32 bit addresses rather than the
@@ -48,7 +61,7 @@
CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
debug output. Bits in debug_layer correspond to a
_COMPONENT in an ACPI source file, e.g.,
- #define _COMPONENT ACPI_PCI_COMPONENT
+ #define _COMPONENT ACPI_EVENTS
Bits in debug_level correspond to a level in
ACPI_DEBUG_PRINT statements, e.g.,
ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
@@ -58,8 +71,6 @@
Enable processor driver info messages:
acpi.debug_layer=0x20000000
- Enable PCI/PCI interrupt routing info messages:
- acpi.debug_layer=0x400000
Enable AML "Debug" output, i.e., stores to the Debug
object while interpreting AML:
acpi.debug_layer=0xffffffff acpi.debug_level=0x2
@@ -113,7 +124,7 @@
the GPE dispatcher.
This facility can be used to prevent such uncontrolled
GPE floodings.
- Format: <byte>
+ Format: <byte> or <bitmap-list>
acpi_no_auto_serialize [HW,ACPI]
Disable auto-serialization of AML methods
@@ -136,6 +147,10 @@
dynamic table installation which will install SSDT
tables to /sys/firmware/acpi/tables/dynamic.
+ acpi_no_watchdog [HW,ACPI,WDT]
+ Ignore the ACPI-based watchdog interface (WDAT) and let
+ a native driver control the watchdog device instead.
+
acpi_rsdp= [ACPI,EFI,KEXEC]
Pass the RSDP address to the kernel, mostly used
on machines running EFI runtime service to boot the
@@ -221,14 +236,23 @@
For broken nForce2 BIOS resulting in XT-PIC timer.
acpi_sleep= [HW,ACPI] Sleep options
- Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
- old_ordering, nonvs, sci_force_enable, nobl }
+ Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
+ s4_nohwsig, old_ordering, nonvs,
+ sci_force_enable, nobl }
See Documentation/power/video.rst for information on
s3_bios and s3_mode.
s3_beep is for debugging; it makes the PC's speaker beep
as soon as the kernel's real-mode entry point is called.
+ s4_hwsig causes the kernel to check the ACPI hardware
+ signature during resume from hibernation, and gracefully
+ refuse to resume if it has changed. This complies with
+ the ACPI specification but not with reality, since
+ Windows does not do this and many laptops do change it
+ on docking. So the default behaviour is to allow resume
+ and simply warn when the signature changes, unless the
+ s4_hwsig option is enabled.
s4_nohwsig prevents ACPI hardware signature from being
- used during resume from hibernation.
+ used (or even warned about) during resume.
old_ordering causes the ACPI 1.0 ordering of the _PTS
control method, with respect to putting devices into
low power states, to be enforced (the ACPI 2.0 ordering
@@ -283,13 +307,21 @@
do not want to use tracing_snapshot_alloc() as it needs
to be done where GFP_KERNEL allocations are allowed.
+ allow_mismatched_32bit_el0 [ARM64]
+ Allow execve() of 32-bit applications and setting of the
+ PER_LINUX32 personality on systems where only a strict
+ subset of the CPUs support 32-bit EL0. When this
+ parameter is present, the set of CPUs supporting 32-bit
+ EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
+ and hot-unplug operations may be restricted.
+
+ See Documentation/arch/arm64/asymmetric-32bit.rst for more
+ information.
+
amd_iommu= [HW,X86-64]
Pass parameters to the AMD IOMMU driver in the system.
Possible values are:
- fullflush - enable flushing of IO/TLB entries when
- they are unmapped. Otherwise they are
- flushed before they will be reused, which
- is a lot of faster
+ fullflush - Deprecated, equivalent to iommu.strict=1
off - do not initialize any AMD IOMMU found in
the system
force_isolation - Force device isolation for all
@@ -297,6 +329,12 @@
allowed anymore to lift isolation
requirements as needed. This option
does not override iommu=pt
+ force_enable - Force enable the IOMMU on platforms known
+ to be buggy with IOMMU enabled. Use this
+ option with care.
+ pgtbl_v1 - Use v1 page table for DMA-API (Default).
+ pgtbl_v2 - Use v2 page table for DMA-API.
+ irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
amd_iommu_dump= [HW,X86-64]
Enable AMD IOMMU driver option to dump the ACPI table
@@ -313,6 +351,29 @@
This mode requires kvm-amd.avic=1.
(Default when IOMMU HW support is present.)
+ amd_pstate= [X86]
+ disable
+ Do not enable amd_pstate as the default
+ scaling driver for the supported processors
+ passive
+ Use amd_pstate with passive mode as a scaling driver.
+ In this mode autonomous selection is disabled.
+ Driver requests a desired performance level and platform
+ tries to match the same performance level if it is
+ satisfied by guaranteed performance level.
+ active
+ Use amd_pstate_epp driver instance as the scaling driver,
+ driver provides a hint to the hardware if software wants
+ to bias toward performance (0x0) or energy efficiency (0xff)
+ to the CPPC firmware. then CPPC power algorithm will
+ calculate the runtime workload and adjust the realtime cores
+ frequency.
+ guided
+ Activate guided autonomous mode. Driver requests minimum and
+ maximum performance level and the platform autonomously
+ selects a performance level in this range and appropriate
+ to the current workload.
+
amijoy.map= [HW,JOY] Amiga joystick support
Map of devices attached to JOY0DAT and JOY1DAT
Format: <a>,<b>
@@ -350,23 +411,39 @@
shot down by NMI
autoconf= [IPV6]
- See Documentation/networking/ipv6.txt.
-
- show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
- Limit apic dumping. The parameter defines the maximal
- number of local apics being dumped. Also it is possible
- to set it to "all" by meaning -- no limit here.
- Format: { 1 (default) | 2 | ... | all }.
- The parameter valid if only apic=debug or
- apic=verbose is specified.
- Example: apic=debug show_lapic=all
+ See Documentation/networking/ipv6.rst.
apm= [APM] Advanced Power Management
See header of arch/x86/kernel/apm_32.c.
+ apparmor= [APPARMOR] Disable or enable AppArmor at boot time
+ Format: { "0" | "1" }
+ See security/apparmor/Kconfig help text
+ 0 -- disable.
+ 1 -- enable.
+ Default value is set via kernel config option.
+
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
Format: <io>,<irq>,<nodeID>
+ arm64.nobti [ARM64] Unconditionally disable Branch Target
+ Identification support
+
+ arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
+ Set instructions support
+
+ arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
+ support
+
+ arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
+ support
+
+ arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
+ Extension support
+
+ arm64.nosve [ARM64] Unconditionally disable Scalable Vector
+ Extension support
+
ataflop= [HW,M68k]
atarimouse= [HW,MOUSE] Atari Mouse
@@ -428,22 +505,33 @@
Format: <io>,<irq>,<mode>
See header of drivers/net/hamradio/baycom_ser_hdx.c.
+ bert_disable [ACPI]
+ Disable BERT OS support on buggy BIOSes.
+
+ bgrt_disable [ACPI][X86]
+ Disable BGRT to avoid flickering OEM logo.
+
blkdevparts= Manual partition parsing of block device(s) for
embedded devices based on command line input.
See Documentation/block/cmdline-partition.rst
boot_delay= Milliseconds to delay each printk during boot.
- Values larger than 10 seconds (10000) are changed to
- no delay (0).
+ Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
+ and you may also have to specify "lpj=". Boot_delay
+ values larger than 10 seconds (10000) are assumed
+ erroneous and ignored.
Format: integer
- bert_disable [ACPI]
- Disable BERT OS support on buggy BIOSes.
+ bootconfig [KNL]
+ Extended command line options can be added to an initrd
+ and this will cause the kernel to look for it.
+
+ See Documentation/admin-guide/bootconfig.rst
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
bttv.radio= Most important insmod options are available as
kernel args too.
- bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
+ bttv.pll= See Documentation/admin-guide/media/bttv.rst
bttv.tuner=
bulk_remove=off [PPC] This parameter disables the use of the pSeries
@@ -476,18 +564,23 @@
others).
ccw_timeout_log [S390]
- See Documentation/s390/common_io.rst for details.
+ See Documentation/arch/s390/common_io.rst for details.
- cgroup_disable= [KNL] Disable a particular controller
- Format: {name of the controller(s) to disable}
+ cgroup_disable= [KNL] Disable a particular controller or optional feature
+ Format: {name of the controller(s) or feature(s) to disable}
The effects of cgroup_disable=foo are:
- foo isn't auto-mounted if you mount all cgroups in
a single hierarchy
- foo isn't visible as an individually mountable
subsystem
+ - if foo is an optional feature then the feature is
+ disabled and corresponding cgroup files are not
+ created
{Currently only "memory" controller deal with this and
cut the overhead, others just disable the usage. So
only cgroup_disable=memory is actually worthy}
+ Specifying "pressure" disables per-cgroup pressure
+ stall information accounting feature
cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
Format: { { controller | "all" | "named" }
@@ -498,12 +591,17 @@
named mounts. Specifying both "all" and "named" disables
all v1 hierarchies.
+ cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
+ Format: { "true" | "false" }
+ Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
+
cgroup.memory= [KNL] Pass options to the cgroup memory controller.
Format: <string>
nosocket -- Disable socket memory accounting.
nokmem -- Disable kernel memory accounting.
+ nobpf -- Disable BPF memory accounting.
- checkreqprot [SELINUX] Set initial checkreqprot flag value.
+ checkreqprot= [SELINUX] Set initial checkreqprot flag value.
Format: { "0" | "1" }
See security/selinux/Kconfig help text.
0 -- check protection applied by kernel (includes
@@ -511,10 +609,30 @@
1 -- check protection requested by application.
Default value is set via a kernel config option.
Value can be changed at runtime via
- /selinux/checkreqprot.
+ /sys/fs/selinux/checkreqprot.
+ Setting checkreqprot to 1 is deprecated.
cio_ignore= [S390]
- See Documentation/s390/common_io.rst for details.
+ See Documentation/arch/s390/common_io.rst for details.
+
+ clearcpuid=X[,X...] [X86]
+ Disable CPUID feature X for the kernel. See
+ arch/x86/include/asm/cpufeatures.h for the valid bit
+ numbers X. Note the Linux-specific bits are not necessarily
+ stable over kernel options, but the vendor-specific
+ ones should be.
+ X can also be a string as appearing in the flags: line
+ in /proc/cpuinfo which does not have the above
+ instability issue. However, not all features have names
+ in /proc/cpuinfo.
+ Note that using this option will taint your kernel.
+ Also note that user programs calling CPUID directly
+ or using the feature without checking anything
+ will still see it. This just prevents it from
+ being used by the kernel or shown in /proc/cpuinfo.
+ Also note the kernel might malfunction if you disable
+ some critical bits.
+
clk_ignore_unused
[CLK]
Prevents the clock framework from automatically gating
@@ -561,27 +679,58 @@
loops can be debugged more effectively on production
systems.
- clearcpuid=BITNUM [X86]
- Disable CPUID feature X for the kernel. See
- arch/x86/include/asm/cpufeatures.h for the valid bit
- numbers. Note the Linux specific bits are not necessarily
- stable over kernel options, but the vendor specific
- ones should be.
- Also note that user programs calling CPUID directly
- or using the feature without checking anything
- will still see it. This just prevents it from
- being used by the kernel or shown in /proc/cpuinfo.
- Also note the kernel might malfunction if you disable
- some critical bits.
+ clocksource.max_cswd_read_retries= [KNL]
+ Number of clocksource_watchdog() retries due to
+ external delays before the clock will be marked
+ unstable. Defaults to two retries, that is,
+ three attempts to read the clock under test.
+
+ clocksource.verify_n_cpus= [KNL]
+ Limit the number of CPUs checked for clocksources
+ marked with CLOCK_SOURCE_VERIFY_PERCPU that
+ are marked unstable due to excessive skew.
+ A negative value says to check all CPUs, while
+ zero says not to check any. Values larger than
+ nr_cpu_ids are silently truncated to nr_cpu_ids.
+ The actual CPUs are chosen randomly, with
+ no replacement if the same CPU is chosen twice.
+
+ clocksource-wdtest.holdoff= [KNL]
+ Set the time in seconds that the clocksource
+ watchdog test waits before commencing its tests.
+ Defaults to zero when built as a module and to
+ 10 seconds when built into the kernel.
cma=nn[MG]@[start[MG][-end[MG]]]
- [ARM,X86,KNL]
+ [KNL,CMA]
Sets the size of kernel global memory area for
contiguous memory allocations and optionally the
placement constraint by the physical address range of
memory allocations. A value of 0 disables CMA
altogether. For more information, see
- include/linux/dma-contiguous.h
+ kernel/dma/contiguous.c
+
+ cma_pernuma=nn[MG]
+ [KNL,CMA]
+ Sets the size of kernel per-numa memory area for
+ contiguous memory allocations. A value of 0 disables
+ per-numa CMA altogether. And If this option is not
+ specified, the default value is 0.
+ With per-numa CMA enabled, DMA users on node nid will
+ first try to allocate buffer from the pernuma area
+ which is located in node nid, if the allocation fails,
+ they will fallback to the global default memory area.
+
+ numa_cma=<node>:nn[MG][,<node>:nn[MG]]
+ [KNL,CMA]
+ Sets the size of kernel numa memory area for
+ contiguous memory allocations. It will reserve CMA
+ area for the specified node.
+
+ With numa CMA enabled, DMA users on node nid will
+ first try to allocate buffer from the numa area
+ which is located in node nid, if the allocation fails,
+ they will fallback to the global default memory area.
cmo_free_hint= [PPC] Format: { yes | no }
Specify whether pages are marked as being inactive
@@ -608,6 +757,17 @@
condev= [HW,S390] console device
conmode=
+ con3215_drop= [S390] 3215 console drop mode.
+ Format: y|n|Y|N|1|0
+ When set to true, drop data on the 3215 console when
+ the console buffer is full. In this case the
+ operator using a 3270 terminal emulator (for example
+ x3270) does not have to enter the clear key for the
+ console output to advance and the kernel to continue.
+ This leads to a much faster boot time when a 3270
+ terminal emulator is active. If no 3270 terminal
+ emulator is used, this parameter has no effect.
+
console= [KNL] Output console device and options.
tty<n> Use the virtual console device <n>.
@@ -622,7 +782,7 @@
See Documentation/admin-guide/serial-console.rst for more
information. See
- Documentation/networking/netconsole.txt for an
+ Documentation/networking/netconsole.rst for an
alternative.
uart[8250],io,<addr>[,options]
@@ -643,6 +803,12 @@
hvc<n> Use the hypervisor console device <n>. This is for
both Xen and PowerPC hypervisors.
+ { null | "" }
+ Use to disable console output, i.e., to have kernel
+ console messages discarded.
+ This must be the only console= parameter used on the
+ kernel command line.
+
If the device connected to the port is not a TTY but a braille
device, prepend "brl," before the device type, for instance
console=brl,ttyS0
@@ -669,7 +835,7 @@
coredump_filter=
[KNL] Change the default value for
/proc/<pid>/coredump_filter.
- See also Documentation/filesystems/proc.txt.
+ See also Documentation/filesystems/proc.rst.
coresight_cpu_debug.enable
[ARM,ARM64]
@@ -678,6 +844,10 @@
0: default value, disable debugging
1: enable debugging at boot time
+ cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
+ Format:
+ <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
+
cpuidle.off=1 [CPU_IDLE]
disable the cpuidle sub-system
@@ -687,15 +857,30 @@
cpufreq.off=1 [CPU_FREQ]
disable the cpufreq sub-system
+ cpufreq.default_governor=
+ [CPU_FREQ] Name of the default cpufreq governor or
+ policy to use. This governor must be registered in the
+ kernel before the cpufreq driver probes.
+
cpu_init_udelay=N
[X86] Delay for N microsec between assert and de-assert
of APIC INIT to start processors. This delay occurs
on every CPU online, such as boot, and resume from suspend.
Default: 10000
- cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
- Format:
- <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
+ cpuhp.parallel=
+ [SMP] Enable/disable parallel bringup of secondary CPUs
+ Format: <bool>
+ Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
+ the parameter has no effect.
+
+ crash_kexec_post_notifiers
+ Run kdump after running panic-notifiers and dumping
+ kmsg. This only for the users who doubt kdump always
+ succeeds in any situation.
+ Note that this also increases risks of kdump failure,
+ because some panic notifiers can make the crashed
+ kernel more unstable.
crashkernel=size[KMG][@offset[KMG]]
[KNL] Using kexec, Linux can switch to a 'crash kernel'
@@ -703,9 +888,9 @@
memory region [offset, offset + size] for that kernel
image. If '@offset' is omitted, then a suitable offset
is selected automatically.
- [KNL, x86_64] select a region under 4G first, and
- fall back to reserve region above 4G when '@offset'
- hasn't been specified.
+ [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
+ under 4G first, and fall back to reserve region above
+ 4G when '@offset' hasn't been specified.
See Documentation/admin-guide/kdump/kdump.rst for further details.
crashkernel=range1:size1[,range2:size2,...][@offset]
@@ -716,22 +901,28 @@
Documentation/admin-guide/kdump/kdump.rst for an example.
crashkernel=size[KMG],high
- [KNL, x86_64] range could be above 4G. Allow kernel
- to allocate physical memory region from top, so could
- be above 4G if system have more than 4G ram installed.
- Otherwise memory region will be allocated below 4G, if
- available.
+ [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
+ above 4G.
+ Allow kernel to allocate physical memory region from top,
+ so could be above 4G if system have more than 4G ram
+ installed. Otherwise memory region will be allocated
+ below 4G, if available.
It will be ignored if crashkernel=X is specified.
crashkernel=size[KMG],low
- [KNL, x86_64] range under 4G. When crashkernel=X,high
- is passed, kernel could allocate physical memory region
- above 4G, that cause second kernel crash on system
- that require some amount of low memory, e.g. swiotlb
- requires at least 64M+32K low memory, also enough extra
- low memory is needed to make sure DMA buffers for 32-bit
- devices won't run out. Kernel would try to allocate at
- at least 256M below 4G automatically.
- This one let user to specify own low range under 4G
+ [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
+ When crashkernel=X,high is passed, kernel could allocate
+ physical memory region above 4G, that cause second kernel
+ crash on system that require some amount of low memory,
+ e.g. swiotlb requires at least 64M+32K low memory, also
+ enough extra low memory is needed to make sure DMA buffers
+ for 32-bit devices won't run out. Kernel would try to allocate
+ default size of memory below 4G automatically. The default
+ size is platform dependent.
+ --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
+ --> arm64: 128MiB
+ --> riscv: 128MiB
+ --> loongarch: 128MiB
+ This one lets the user specify own low range under 4G
for second kernel instead.
0: to disable low allocation.
It will be ignored when crashkernel=X,high is not used
@@ -746,6 +937,15 @@
cs89x0_media= [HW,NET]
Format: { rj45 | aui | bnc }
+ csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
+ function call handling. When switched on,
+ additional debug data is printed to the console
+ in case a hanging CPU is detected, and that
+ CPU is pinged again in order to try to resolve
+ the hang situation. The default value of this
+ option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
+ Kconfig option.
+
dasd= [HW,NET]
See header of drivers/s390/block/dasd_devmap.c.
@@ -754,11 +954,6 @@
Format: <port#>,<type>
See also Documentation/input/devices/joystick-parport.rst
- ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
- time. See
- Documentation/admin-guide/dynamic-debug-howto.rst for
- details. Deprecated, see dyndbg.
-
debug [KNL] Enable kernel debugging (events log level).
debug_boot_weak_hash
@@ -770,19 +965,17 @@
insecure, please do not use on production kernels.
debug_locks_verbose=
- [KNL] verbose self-tests
- Format=<0|1>
+ [KNL] verbose locking self-tests
+ Format: <int>
Print debugging info while doing the locking API
self-tests.
- We default to 0 (no extra messages), setting it to
- 1 will print _a lot_ more information - normally
- only useful to kernel developers.
+ Bitmask for the various LOCKTYPE_ tests. Defaults to 0
+ (no extra messages), setting it to -1 (all bits set)
+ will print _a_lot_ more information - normally only
+ useful to lockdep developers.
debug_objects [KNL] Enable object debugging
- no_debug_objects
- [KNL] Disable object debugging
-
debug_guardpage_minorder=
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
parameter allows control of the order of pages that will
@@ -790,17 +983,17 @@
buddy allocator. Bigger value increase the probability
of catching random memory corruption, but reduce the
amount of memory for normal system use. The maximum
- possible value is MAX_ORDER/2. Setting this parameter
- to 1 or 2 should be enough to identify most random
- memory corruption problems caused by bugs in kernel or
- driver code when a CPU writes to (or reads from) a
- random memory location. Note that there exists a class
- of memory corruptions problems caused by buggy H/W or
- F/W or by drivers badly programing DMA (basically when
- memory is written at bus level and the CPU MMU is
- bypassed) which are not detectable by
- CONFIG_DEBUG_PAGEALLOC, hence this option will not help
- tracking down these problems.
+ possible value is MAX_PAGE_ORDER/2. Setting this
+ parameter to 1 or 2 should be enough to identify most
+ random memory corruption problems caused by bugs in
+ kernel or driver code when a CPU writes to (or reads
+ from) a random memory location. Note that there exists
+ a class of memory corruptions problems caused by buggy
+ H/W or F/W or by drivers badly programming DMA
+ (basically when memory is written at bus level and the
+ CPU MMU is bypassed) which are not detectable by
+ CONFIG_DEBUG_PAGEALLOC, hence this option will not
+ help tracking down these problems.
debug_pagealloc=
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
@@ -811,29 +1004,83 @@
useful to also enable the page_owner functionality.
on: enable the feature
- debugpat [X86] Enable PAT debugging
+ debugfs= [KNL] This parameter enables what is exposed to userspace
+ and debugfs internal clients.
+ Format: { on, no-mount, off }
+ on: All functions are enabled.
+ no-mount:
+ Filesystem is not registered but kernel clients can
+ access APIs and a crashkernel can be used to read
+ its content. There is nothing to mount.
+ off: Filesystem is not registered and clients
+ get a -EPERM as result when trying to register files
+ or directories within debugfs.
+ This is equivalent of the runtime functionality if
+ debugfs was not enabled in the kernel at all.
+ Default value is set in build-time with a kernel configuration.
- decnet.addr= [HW,NET]
- Format: <area>[,<node>]
- See also Documentation/networking/decnet.txt.
+ debugpat [X86] Enable PAT debugging
default_hugepagesz=
- [same as hugepagesz=] The size of the default
- HugeTLB page size. This is the size represented by
- the legacy /proc/ hugepages APIs, used for SHM, and
- default size when mounting hugetlbfs filesystems.
- Defaults to the default architecture's huge page size
- if not specified.
+ [HW] The size of the default HugeTLB page. This is
+ the size represented by the legacy /proc/ hugepages
+ APIs. In addition, this is the default hugetlb size
+ used for shmget(), mmap() and mounting hugetlbfs
+ filesystems. If not specified, defaults to the
+ architecture's default huge page size. Huge page
+ sizes are architecture dependent. See also
+ Documentation/admin-guide/mm/hugetlbpage.rst.
+ Format: size[KMG]
deferred_probe_timeout=
[KNL] Debugging option to set a timeout in seconds for
deferred probe to give up waiting on dependencies to
probe. Only specific dependencies (subsystems or
- drivers) that have opted in will be ignored. A timeout of 0
- will timeout at the end of initcalls. This option will also
+ drivers) that have opted in will be ignored. A timeout
+ of 0 will timeout at the end of initcalls. If the time
+ out hasn't expired, it'll be restarted by each
+ successful driver registration. This option will also
dump out devices still on the deferred probe list after
retrying.
+ delayacct [KNL] Enable per-task delay accounting
+
+ dell_smm_hwmon.ignore_dmi=
+ [HW] Continue probing hardware even if DMI data
+ indicates that the driver is running on unsupported
+ hardware.
+
+ dell_smm_hwmon.force=
+ [HW] Activate driver even if SMM BIOS signature does
+ not match list of supported models and enable otherwise
+ blacklisted features.
+
+ dell_smm_hwmon.power_status=
+ [HW] Report power status in /proc/i8k
+ (disabled by default).
+
+ dell_smm_hwmon.restricted=
+ [HW] Allow controlling fans only if SYS_ADMIN
+ capability is set.
+
+ dell_smm_hwmon.fan_mult=
+ [HW] Factor to multiply fan speed with.
+
+ dell_smm_hwmon.fan_max=
+ [HW] Maximum configurable fan speed.
+
+ dfltcc= [HW,S390]
+ Format: { on | off | def_only | inf_only | always }
+ on: s390 zlib hardware support for compression on
+ level 1 and decompression (default)
+ off: No s390 zlib hardware support
+ def_only: s390 zlib hardware support for deflate
+ only (compression on level 1)
+ inf_only: s390 zlib hardware support for inflate
+ only (decompression)
+ always: Same as 'on' but ignores the selected compression
+ level always using hardware support (used for debugging)
+
dhash_entries= [KNL]
Set number of hash buckets for dentry cache.
@@ -844,18 +1091,7 @@
miss to occur.
disable= [IPV6]
- See Documentation/networking/ipv6.txt.
-
- hardened_usercopy=
- [KNL] Under CONFIG_HARDENED_USERCOPY, whether
- hardening is enabled for this boot. Hardened
- usercopy checking is used to protect the kernel
- from reading or writing beyond known memory
- allocation boundaries as a proactive defense
- against bounds-checking flaws in the kernel's
- copy_to_user()/copy_from_user() interface.
- on Perform hardened usercopy checks (default).
- off Disable hardened usercopy checks.
+ See Documentation/networking/ipv6.rst.
disable_radix [PPC]
Disable RADIX MMU mode on POWER9
@@ -873,18 +1109,12 @@
causing system reset or hang due to sending
INIT from AP to BSP.
- perf_v4_pmi= [X86,INTEL]
- Format: <bool>
- Disable Intel PMU counter freezing feature.
- The feature only exists starting from
- Arch Perfmon v4 (Skylake and newer).
-
disable_ddw [PPC/PSERIES]
- Disable Dynamic DMA Window support. Use this if
+ Disable Dynamic DMA Window support. Use this
to workaround buggy firmware.
disable_ipv6= [IPV6]
- See Documentation/networking/ipv6.txt.
+ See Documentation/networking/ipv6.rst.
disable_mtrr_cleanup [X86]
The kernel tries to adjust MTRR layout from continuous
@@ -921,7 +1151,10 @@
driver later using sysfs.
driver_async_probe= [KNL]
- List of driver names to be probed asynchronously.
+ List of driver names to be probed asynchronously. *
+ matches with all driver names. If * is specified, the
+ rest of the listed driver names are those that will NOT
+ match the *.
Format: <driver_name1>,<driver_name2>...
drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
@@ -934,7 +1167,7 @@
edid/1680x1050.bin, or edid/1920x1080.bin is given
and no file with the same name exists. Details and
instructions how to build your own EDID data are
- available in Documentation/driver-api/edid.rst. An EDID
+ available in Documentation/admin-guide/edid.rst. An EDID
data set will only be used for a particular connector,
if its name and a colon are prepended to the EDID
name. Each connector may use a unique EDID data
@@ -959,21 +1192,11 @@
what data is available or for reverse-engineering.
dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
- module.dyndbg[="val"]
+ <module>.dyndbg[="val"]
Enable debug messages at boot time. See
Documentation/admin-guide/dynamic-debug-howto.rst
for details.
- nompx [X86] Disables Intel Memory Protection Extensions.
- See Documentation/x86/intel_mpx.rst for more
- information about the feature.
-
- nopku [X86] Disable Memory Protection Keys CPU feature found
- in some Intel CPUs.
-
- module.async_probe [KNL]
- Enable asynchronous probe on this module.
-
early_ioremap_debug [KNL]
Enable debug messages in early_ioremap support. This
is useful for tracking down temporary early mappings
@@ -993,10 +1216,10 @@
specified, the serial port must already be setup and
configured.
- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
- uart[8250],mmio32,<addr>[,options]
- uart[8250],mmio32be,<addr>[,options]
+ uart[8250],io,<addr>[,options[,uartclk]]
+ uart[8250],mmio,<addr>[,options[,uartclk]]
+ uart[8250],mmio32,<addr>[,options[,uartclk]]
+ uart[8250],mmio32be,<addr>[,options[,uartclk]]
uart[8250],0x<addr>[,options]
Start an early, polled-mode console on the 8250/16550
UART at the specified I/O port or MMIO address.
@@ -1005,7 +1228,9 @@
If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
to be equivalent to 'mmio'. 'options' are specified
in the same format described for "console=ttyS<n>"; if
- unspecified, the h/w is not initialized.
+ unspecified, the h/w is not initialized. 'uartclk' is
+ the uart clock frequency; if unspecified, it is set
+ to 'BASE_BAUD' * 16.
pl011,<addr>
pl011,mmio32,<addr>
@@ -1016,6 +1241,11 @@
the driver will use only 32-bit accessors to read/write
the device registers.
+ liteuart,<addr>
+ Start an early console on a litex serial port at the
+ specified address. The serial port must already be
+ setup and configured. Options are not yet supported.
+
meson,<addr>
Start an early, polled-mode console on a meson serial
port at the specified address. The serial port must
@@ -1077,6 +1307,12 @@
A valid base address must be provided, and the serial
port must already be setup and configured.
+ ec_imx21,<addr>
+ ec_imx6q,<addr>
+ Start an early, polled-mode, output-only console on the
+ Freescale i.MX UART at the specified address. The UART
+ must already be setup and configured.
+
ar3700_uart,<addr>
Start an early, polled-mode console on the
Armada 3700 serial port at the specified
@@ -1112,6 +1348,7 @@
earlyprintk=dbgp[debugController#]
earlyprintk=pciserial[,force],bus:device.function[,baudrate]
earlyprintk=xdbc[xhciController#]
+ earlyprintk=bios
earlyprintk is useful when the kernel crashes before
the normal console is initialized. It is not enabled by
@@ -1120,7 +1357,7 @@
Append ",keep" to not disable it when the real console
takes over.
- Only one of vga, efi, serial, or usb debug port can
+ Only one of vga, serial, or usb debug port can
be used at a time.
Currently only ttyS0 and ttyS1 may be specified by
@@ -1135,13 +1372,15 @@
Interaction with the standard serial driver is not
very good.
- The VGA and EFI output is eventually overwritten by
+ The VGA output is eventually overwritten by
the real console.
- The xen output can only be used by Xen PV guests.
+ The xen option can only be used in Xen domains.
The sclp output can only be used on s390.
+ The bios output can only be used on SuperH.
+
The optional "force" to "pciserial" enables use of a
PCI device even when its classcode is not of the
UART class.
@@ -1154,32 +1393,29 @@
force: enforce the use of EDAC to report H/W event.
default: on.
- ekgdboc= [X86,KGDB] Allow early kernel console debugging
- ekgdboc=kbd
-
- This is designed to be used in conjunction with
- the boot argument: earlyprintk=vga
-
edd= [EDD]
Format: {"off" | "on" | "skip[mbr]"}
efi= [EFI]
- Format: { "old_map", "nochunk", "noruntime", "debug",
- "nosoftreserve" }
- old_map [X86-64]: switch to the old ioremap-based EFI
- runtime services mapping. 32-bit still uses this one by
- default.
+ Format: { "debug", "disable_early_pci_dma",
+ "nochunk", "noruntime", "nosoftreserve",
+ "novamap", "no_disable_early_pci_dma" }
+ debug: enable misc debug output.
+ disable_early_pci_dma: disable the busmaster bit on all
+ PCI bridges while in the EFI boot stub.
nochunk: disable reading files in "chunks" in the EFI
boot stub, as chunking can cause problems with some
firmware implementations.
noruntime : disable EFI runtime services support
- debug: enable misc debug output
nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
attribute may cause the kernel to reserve the
memory range for a memory mapping driver to
claim. Specify efi=nosoftreserve to disable this
reservation and treat the memory by its base type
(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
+ novamap: do not call SetVirtualAddressMap().
+ no_disable_early_pci_dma: Leave the busmaster bit set
+ on all PCI bridges while in the EFI boot stub
efi_no_storage_paranoia [EFI; X86]
Using this parameter you can use more than 50% of
@@ -1218,11 +1454,22 @@
eisa_irq_edge= [PARISC,HW]
See header of drivers/parisc/eisa.c.
+ ekgdboc= [X86,KGDB] Allow early kernel console debugging
+ Format: ekgdboc=kbd
+
+ This is designed to be used in conjunction with
+ the boot argument: earlyprintk=vga
+
+ This parameter works in place of the kgdboc parameter
+ but can only be used if the backing tty is available
+ very early in the boot process. For early debugging
+ via a serial port see kgdboc_earlycon instead.
+
elanfreq= [X86-32]
See comment before function elanfreq_setup() in
arch/x86/kernel/cpu/cpufreq/elanfreq.c.
- elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
+ elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390]
Specifies physical address of start of kernel core
image elf header and optionally the size. Generally
kexec loader will pass this option to capture kernel.
@@ -1239,13 +1486,14 @@
(in particular on some ATI chipsets).
The kernel tries to set a reasonable default.
- enforcing [SELINUX] Set initial enforcing status.
+ enforcing= [SELINUX] Set initial enforcing status.
Format: {"0" | "1"}
See security/selinux/Kconfig help text.
0 -- permissive (log only, no denials).
1 -- enforcing (deny and log).
Default value is 0.
- Value can be changed at runtime via /selinux/enforce.
+ Value can be changed at runtime via
+ /sys/fs/selinux/enforce.
erst_disable [ACPI]
Disable Error Record Serialization Table (ERST)
@@ -1260,22 +1508,30 @@
Permit 'security.evm' to be updated regardless of
current integrity status.
+ early_page_ext [KNL] Enforces page_ext initialization to earlier
+ stages so cover more early boot allocations.
+ Please note that as side effect some optimizations
+ might be disabled to achieve that (e.g. parallelized
+ memory initialization is disabled) so the boot process
+ might take longer, especially on systems with a lot of
+ memory. Available with CONFIG_PAGE_EXTENSION=y.
+
failslab=
+ fail_usercopy=
fail_page_alloc=
fail_make_request=[KNL]
General fault injection mechanism.
Format: <interval>,<probability>,<space>,<times>
See also Documentation/fault-injection/.
+ fb_tunnels= [NET]
+ Format: { initns | none }
+ See Documentation/admin-guide/sysctl/net.rst for
+ fb_tunnels_only_for_init_ns
+
floppy= [HW]
See Documentation/admin-guide/blockdev/floppy.rst.
- force_pal_cache_flush
- [IA-64] Avoid check_sal_cache_flush which may hang on
- buggy SAL_CACHE_FLUSH implementations. Using this
- parameter will force ia64_sal_cache_flush to call
- ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
-
forcepae [X86-32]
Forcefully enable Physical Address Extension (PAE).
Many Pentium M systems disable PAE but may have a
@@ -1288,6 +1544,23 @@
as early as possible in order to facilitate early
boot debugging.
+ ftrace_boot_snapshot
+ [FTRACE] On boot up, a snapshot will be taken of the
+ ftrace ring buffer that can be read at:
+ /sys/kernel/tracing/snapshot.
+ This is useful if you need tracing information from kernel
+ boot up that is likely to be overridden by user space
+ start up functionality.
+
+ Optionally, the snapshot can also be defined for a tracing
+ instance that was created by the trace_instance= command
+ line parameter.
+
+ trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
+
+ The above will cause the "foo" tracing instance to trigger
+ a snapshot at the end of boot up.
+
ftrace_dump_on_oops[=orig_cpu]
[FTRACE] will dump the trace buffers on oops.
If no parameter is passed, ftrace will dump
@@ -1297,7 +1570,7 @@
ftrace_filter=[function-list]
[FTRACE] Limit the functions traced by the function
- tracer at boot up. function-list is a comma separated
+ tracer at boot up. function-list is a comma-separated
list of functions. This list can be changed at run
time by the set_ftrace_filter file in the debugfs
tracing directory.
@@ -1311,13 +1584,13 @@
ftrace_graph_filter=[function-list]
[FTRACE] Limit the top level callers functions traced
by the function graph tracer at boot up.
- function-list is a comma separated list of functions
+ function-list is a comma-separated list of functions
that can be changed at run time by the
set_graph_function file in the debugfs tracing directory.
ftrace_graph_notrace=[function-list]
[FTRACE] Do not trace from the functions specified in
- function-list. This list is a comma separated list of
+ function-list. This list is a comma-separated list of
functions that can be changed at run time by the
set_graph_notrace file in the debugfs tracing directory.
@@ -1327,6 +1600,43 @@
can be changed at run time by the max_graph_depth file
in the tracefs tracing directory. default: 0 (no limit)
+ fw_devlink= [KNL] Create device links between consumer and supplier
+ devices by scanning the firmware to infer the
+ consumer/supplier relationships. This feature is
+ especially useful when drivers are loaded as modules as
+ it ensures proper ordering of tasks like device probing
+ (suppliers first, then consumers), supplier boot state
+ clean up (only after all consumers have probed),
+ suspend/resume & runtime PM (consumers first, then
+ suppliers).
+ Format: { off | permissive | on | rpm }
+ off -- Don't create device links from firmware info.
+ permissive -- Create device links from firmware info
+ but use it only for ordering boot state clean
+ up (sync_state() calls).
+ on -- Create device links from firmware info and use it
+ to enforce probe and suspend/resume ordering.
+ rpm -- Like "on", but also use to order runtime PM.
+
+ fw_devlink.strict=<bool>
+ [KNL] Treat all inferred dependencies as mandatory
+ dependencies. This only applies for fw_devlink=on|rpm.
+ Format: <bool>
+
+ fw_devlink.sync_state =
+ [KNL] When all devices that could probe have finished
+ probing, this parameter controls what to do with
+ devices that haven't yet received their sync_state()
+ calls.
+ Format: { strict | timeout }
+ strict -- Default. Continue waiting on consumers to
+ probe successfully.
+ timeout -- Give up waiting on consumers and call
+ sync_state() on any devices that haven't yet
+ received their sync_state() calls after
+ deferred_probe_timeout has expired or by
+ late_initcall() if !CONFIG_MODULES.
+
gamecon.map[2|3]=
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
support via parallel port (up to 5 devices per port)
@@ -1335,10 +1645,30 @@
gamma= [HW,DRM]
- gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
+ gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
Format: off | on
default: on
+ gather_data_sampling=
+ [X86,INTEL] Control the Gather Data Sampling (GDS)
+ mitigation.
+
+ Gather Data Sampling is a hardware vulnerability which
+ allows unprivileged speculative access to data which was
+ previously stored in vector registers.
+
+ This issue is mitigated by default in updated microcode.
+ The mitigation may have a performance impact but can be
+ disabled. On systems without the microcode mitigation
+ disabling AVX serves as a mitigation.
+
+ force: Disable AVX to mitigate systems without
+ microcode mitigation. No effect if the microcode
+ mitigation is present. Known to cause crashes in
+ userspace with buggy AVX enumeration.
+
+ off: Disable GDS mitigation.
+
gcov_persist= [GCOV] When non-zero (default), profiling data for
kernel modules is saved and remains accessible via
debugfs, even when the module is unloaded/reloaded.
@@ -1349,6 +1679,12 @@
Don't use this when you are not running on the
android emulator
+ gpio-mockup.gpio_mockup_ranges
+ [HW] Sets the ranges of gpiochip of for this device.
+ Format: <start1>,<end1>,<start2>,<end2>...
+ gpio-mockup.gpio_mockup_named_lines
+ [HW] Let the driver know GPIO lines should be named.
+
gpt [EFI] Forces disk with valid GPT signature but
invalid Protective MBR to be treated as GPT. If the
primary GPT is corrupted, it enables the backup/alternate
@@ -1372,14 +1708,21 @@
Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
Default: 1024
- gpio-mockup.gpio_mockup_ranges
- [HW] Sets the ranges of gpiochip of for this device.
- Format: <start1>,<end1>,<start2>,<end2>...
+ hardened_usercopy=
+ [KNL] Under CONFIG_HARDENED_USERCOPY, whether
+ hardening is enabled for this boot. Hardened
+ usercopy checking is used to protect the kernel
+ from reading or writing beyond known memory
+ allocation boundaries as a proactive defense
+ against bounds-checking flaws in the kernel's
+ copy_to_user()/copy_from_user() interface.
+ on Perform hardened usercopy checks (default).
+ off Disable hardened usercopy checks.
hardlockup_all_cpu_backtrace=
[KNL] Should the hard-lockup detector generate
backtraces on all cpus.
- Format: <integer>
+ Format: 0 | 1
hashdist= [KNL,NUMA] Large hashes allocated during boot
are distributed across NUMA nodes. Defaults on
@@ -1396,6 +1739,15 @@
corresponding firmware-first mode error processing
logic will be disabled.
+ hibernate= [HIBERNATION]
+ noresume Don't check if there's a hibernation image
+ present during boot.
+ nocompress Don't compress/decompress hibernation images.
+ no Disable hibernation and resume.
+ protect_image Turn on image protection during restoration
+ (that will set all pages holding image data
+ during restoration read-only).
+
highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
size of <nn>. This works even on boxes that have no
highmem otherwise. This also works to reduce highmem
@@ -1407,6 +1759,19 @@
hlt [BUGS=ARM,SH]
+ hostname= [KNL] Set the hostname (aka UTS nodename).
+ Format: <string>
+ This allows setting the system's hostname during early
+ startup. This sets the name returned by gethostname.
+ Using this parameter to set the hostname makes it
+ possible to ensure the hostname is correctly set before
+ any userspace processes run, avoiding the possibility
+ that a process may call gethostname before the hostname
+ has been explicitly set, resulting in the calling
+ process getting an incorrect result. The string must
+ not exceed the maximum allowed hostname length (usually
+ 64 characters) and will be truncated otherwise.
+
hpet= [X86-32,HPET] option to control HPET usage
Format: { enable (default) | disable | force |
verbose }
@@ -1418,19 +1783,62 @@
hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
- hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
- hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
- On x86-64 and powerpc, this option can be specified
- multiple times interleaved with hugepages= to reserve
- huge pages of different sizes. Valid pages sizes on
- x86-64 are 2M (when the CPU supports "pse") and 1G
- (when the CPU supports the "pdpe1gb" cpuinfo flag).
+ hugepages= [HW] Number of HugeTLB pages to allocate at boot.
+ If this follows hugepagesz (below), it specifies
+ the number of pages of hugepagesz to be allocated.
+ If this is the first HugeTLB parameter on the command
+ line, it specifies the number of pages to allocate for
+ the default huge page size. If using node format, the
+ number of pages to allocate per-node can be specified.
+ See also Documentation/admin-guide/mm/hugetlbpage.rst.
+ Format: <integer> or (node format)
+ <node>:<integer>[,<node>:<integer>]
+
+ hugepagesz=
+ [HW] The size of the HugeTLB pages. This is used in
+ conjunction with hugepages (above) to allocate huge
+ pages of a specific size at boot. The pair
+ hugepagesz=X hugepages=Y can be specified once for
+ each supported huge page size. Huge page sizes are
+ architecture dependent. See also
+ Documentation/admin-guide/mm/hugetlbpage.rst.
+ Format: size[KMG]
+
+ hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
+ of gigantic hugepages. Or using node format, the size
+ of a CMA area per node can be specified.
+ Format: nn[KMGTPE] or (node format)
+ <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
+
+ Reserve a CMA area of given size and allocate gigantic
+ hugepages using the CMA allocator. If enabled, the
+ boot-time allocation of gigantic hugepages is skipped.
+
+ hugetlb_free_vmemmap=
+ [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+ enabled.
+ Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
+ Allows heavy hugetlb users to free up some more
+ memory (7 * PAGE_SIZE for each 2MB hugetlb page).
+ Format: { on | off (default) }
+
+ on: enable HVO
+ off: disable HVO
+
+ Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
+ the default is on.
+
+ Note that the vmemmap pages may be allocated from the added
+ memory block itself when memory_hotplug.memmap_on_memory is
+ enabled, those vmemmap pages cannot be optimized even if this
+ feature is enabled. Other vmemmap pages not allocated from
+ the added memory block itself do not be affected.
hung_task_panic=
[KNL] Should the hung task detector generate panics.
- Format: <integer>
+ Format: 0 | 1
- A nonzero value instructs the kernel to panic when a
+ A value of 1 instructs the kernel to panic when a
hung task is detected. The default value is controlled
by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
option. The value selected by this boot parameter can
@@ -1446,12 +1854,6 @@
which allow the hypervisor to 'idle' the
guest on lock contention.
- keep_bootcon [KNL]
- Do not unregister boot console at start. This is only
- useful for debugging when something happens in the window
- between unregistering the boot console and initializing
- the real console.
-
i2c_bus= [HW] Override the default board specific I2C bus speed
or register an additional I2C bus that is not
registered from board initialization code.
@@ -1486,20 +1888,11 @@
architectures force reset to be always executed
i8042.unlock [HW] Unlock (ignore) the keylock
i8042.kbdreset [HW] Reset device connected to KBD port
+ i8042.probe_defer
+ [HW] Allow deferred probing upon i8042 probe errors
i810= [HW,DRM]
- i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
- indicates that the driver is running on unsupported
- hardware.
- i8k.force [HW] Activate i8k driver even if SMM BIOS signature
- does not match list of supported models.
- i8k.power_status
- [HW] Report power status in /proc/i8k
- (disabled by default)
- i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
- capability is set.
-
i915.invert_brightness=
[DRM] Invert the sense of the variable that is used to
set the brightness of the panel backlight. Normally a
@@ -1514,29 +1907,15 @@
0 -- machine default
1 -- force brightness inversion
+ ia32_emulation= [X86-64]
+ Format: <bool>
+ When true, allows loading 32-bit programs and executing 32-bit
+ syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
+ boot time. When false, unconditionally disables IA32 emulation.
+
icn= [HW,ISDN]
Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
- ide-core.nodma= [HW] (E)IDE subsystem
- Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
- .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
- .cdrom .chs .ignore_cable are additional options
- See Documentation/ide/ide.rst.
-
- ide-generic.probe-mask= [HW] (E)IDE subsystem
- Format: <int>
- Probe mask for legacy ISA IDE ports. Depending on
- platform up to 6 ports are supported, enabled by
- setting corresponding bits in the mask to 1. The
- default value is 0x0, which has a special meaning.
- On systems that have PCI, it triggers scanning the
- PCI bus for the first and the second port, which
- are then probed. On systems without PCI the value
- of 0x0 enables probing the two first ports as if it
- was 0x3.
-
- ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
- Claim all unknown PCI IDE storage controllers.
idle= [X86]
Format: idle=poll, idle=halt, idle=nomwait
@@ -1548,6 +1927,17 @@
In such case C2/C3 won't be used again.
idle=nomwait: Disable mwait for CPU C-states
+ idxd.sva= [HW]
+ Format: <bool>
+ Allow force disabling of Shared Virtual Memory (SVA)
+ support for the idxd driver. By default it is set to
+ true (1).
+
+ idxd.tc_override= [HW]
+ Format: <bool>
+ Allow override of default traffic class configuration
+ for the device. By default it is set to false (0).
+
ieee754= [MIPS] Select IEEE Std 754 conformance mode
Format: { strict | legacy | 2008 | relaxed }
Default: strict
@@ -1621,7 +2011,7 @@
ima_policy= [IMA]
The builtin policies to load during IMA setup.
Format: "tcb | appraise_tcb | secure_boot |
- fail_securely"
+ fail_securely | critical_data"
The "tcb" policy measures all programs exec'd, files
mmap'd for exec, and all files opened with the read
@@ -1640,6 +2030,9 @@
filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
flag.
+ The "critical_data" policy measures kernel integrity
+ critical data.
+
ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Load a policy which meets the needs of the Trusted
Computing Base. This means IMA will measure all
@@ -1648,7 +2041,8 @@
ima_template= [IMA]
Select one of defined IMA measurements template formats.
- Formats: { "ima" | "ima-ng" | "ima-sig" }
+ Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
+ "ima-sigv2" }
Default: "ima-ng"
ima_template_fmt=
@@ -1685,8 +2079,27 @@
initcall functions. Useful for debugging built-in
modules and initcalls.
+ initramfs_async= [KNL]
+ Format: <bool>
+ Default: 1
+ This parameter controls whether the initramfs
+ image is unpacked asynchronously, concurrently
+ with devices being probed and
+ initialized. This should normally just work,
+ but as a debugging aid, one can get the
+ historical behaviour of the initramfs
+ unpacking being completed before device_ and
+ late_ initcalls.
+
initrd= [BOOT] Specify the location of the initial ramdisk
+ initrdmem= [KNL] Specify a physical address and size from which to
+ load the initrd. If an initrd is compiled in or
+ specified in the bootparams, it takes priority over this
+ setting.
+ Format: ss[KMG],nn[KMG]
+ Default is 0, 0
+
init_on_alloc= [MM] Fill newly allocated pages and heap objects with
zeroes.
Format: 0 | 1
@@ -1696,7 +2109,7 @@
Format: 0 | 1
Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
- init_pkru= [x86] Specify the default memory protection keys rights
+ init_pkru= [X86] Specify the default memory protection keys rights
register contents for all processes. 0x55555554 by
default (disallow access to all but pkey 0). Can
override in debugfs after boot.
@@ -1704,7 +2117,7 @@
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
Format: <irq>
- int_pln_enable [x86] Enable power limit notification interrupt
+ int_pln_enable [X86] Enable power limit notification interrupt
integrity_audit=[IMA]
Format: { "0" | "1" }
@@ -1722,26 +2135,18 @@
bypassed by not enabling DMAR with this option. In
this case, gfx device will use physical address for
DMA.
- forcedac [x86_64]
- With this option iommu will not optimize to look
- for io virtual address below 32-bit forcing dual
- address cycle on pci bus for cards supporting greater
- than 32-bit addressing. The default is to look
- for translation below 32-bit and if not available
- then look in the higher range.
strict [Default Off]
- With this option on every unmap_single operation will
- result in a hardware IOTLB flush operation as opposed
- to batching them for performance.
+ Deprecated, equivalent to iommu.strict=1.
sp_off [Default Off]
By default, super page will be supported if Intel IOMMU
has the capability. With this option, super page will
not be supported.
- sm_on [Default Off]
- By default, scalable mode will be disabled even if the
- hardware advertises that it has support for the scalable
- mode translation. With this option set, scalable mode
- will be used on hardware which claims to support it.
+ sm_on
+ Enable the Intel IOMMU scalable mode if the hardware
+ advertises that it has support for the scalable mode
+ translation.
+ sm_off
+ Disallow use of the Intel IOMMU scalable mode.
tboot_noforce [Default Off]
Do not force the Intel IOMMU enabled under tboot.
By default, tboot will force Intel IOMMU on, which
@@ -1751,11 +2156,6 @@
Note that using this option lowers the security
provided by tboot because it makes the system
vulnerable to DMA attacks.
- nobounce [Default off]
- Disable bounce buffer for unstrusted devices such as
- the Thunderbolt devices. This will treat the untrusted
- devices as the trusted ones, hence might expose security
- risks of DMA attacks.
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
0 disables intel_idle and fall back on acpi_idle.
@@ -1765,6 +2165,16 @@
disable
Do not enable intel_pstate as the default
scaling driver for the supported processors
+ active
+ Use intel_pstate driver to bypass the scaling
+ governors layer of cpufreq and provides it own
+ algorithms for p-state selection. There are two
+ P-state selection algorithms provided by
+ intel_pstate in the active mode: powersave and
+ performance. The way they both operate depends
+ on whether or not the hardware managed P-states
+ (HWP) feature has been enabled in the processor
+ and possibly on the processor model.
passive
Use intel_pstate as a scaling driver, but configure it
to work with generic cpufreq governors (instead of
@@ -1807,7 +2217,7 @@
strict regions from userspace.
relaxed
- iommu= [x86]
+ iommu= [X86]
off
force
noforce
@@ -1817,12 +2227,20 @@
merge
nomerge
soft
- pt [x86]
- nopt [x86]
+ pt [X86]
+ nopt [X86]
nobypass [PPC/POWERNV]
Disable IOMMU bypass, using IOMMU for PCI devices.
- iommu.strict= [ARM64] Configure TLB invalidation behaviour
+ iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
+ Format: { "0" | "1" }
+ 0 - Try to allocate a 32-bit DMA address first, before
+ falling back to the full range if needed.
+ 1 - Allocate directly from the full usable range,
+ forcing Dual Address Cycle for PCI cards supporting
+ greater than 32-bit addressing.
+
+ iommu.strict= [ARM64, X86, S390] Configure TLB invalidation behaviour
Format: { "0" | "1" }
0 - Lazy mode.
Request that DMA unmap operations use deferred
@@ -1830,9 +2248,12 @@
throughput at the cost of reduced device isolation.
Will fall back to strict mode if not supported by
the relevant IOMMU driver.
- 1 - Strict mode (default).
+ 1 - Strict mode.
DMA unmap operations invalidate IOMMU hardware TLBs
synchronously.
+ unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
+ Note: on x86, strict mode specified via one of the
+ legacy driver-specific options takes precedence.
iommu.passthrough=
[ARM64, X86] Configure DMA to bypass the IOMMU by default.
@@ -1841,7 +2262,7 @@
1 - Bypass the IOMMU for DMA.
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
- io7= [HW] IO7 for Marvel based alpha systems
+ io7= [HW] IO7 for Marvel-based Alpha systems
See comment before marvel_specify_io7 in
arch/alpha/kernel/core_marvel.c.
@@ -1856,7 +2277,7 @@
No delay
ip= [IP_PNP]
- See Documentation/filesystems/nfs/nfsroot.txt.
+ See Documentation/admin-guide/nfs/nfsroot.rst.
ipcmni_extend [KNL] Extend the maximum number of unique System V
IPC identifiers from 32,768 to 16,777,216.
@@ -1933,48 +2354,104 @@
<cpu number> begins at 0 and the maximum value is
"number of CPUs in system - 1".
- The format of <cpu-list> is described above.
-
+ managed_irq
+
+ Isolate from being targeted by managed interrupts
+ which have an interrupt mask containing isolated
+ CPUs. The affinity of managed interrupts is
+ handled by the kernel and cannot be changed via
+ the /proc/irq/* interfaces.
+
+ This isolation is best effort and only effective
+ if the automatically assigned interrupt mask of a
+ device queue contains isolated and housekeeping
+ CPUs. If housekeeping CPUs are online then such
+ interrupts are directed to the housekeeping CPU
+ so that IO submitted on the housekeeping CPU
+ cannot disturb the isolated CPU.
+
+ If a queue's affinity mask contains only isolated
+ CPUs then this parameter has no effect on the
+ interrupt routing decision, though interrupts are
+ only delivered when tasks running on those
+ isolated CPUs submit IO. IO submitted on
+ housekeeping CPUs has no influence on those
+ queues.
+ The format of <cpu-list> is described above.
iucv= [HW,NET]
- ivrs_ioapic [HW,X86_64]
+ ivrs_ioapic [HW,X86-64]
Provide an override to the IOAPIC-ID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map IOAPIC-ID decimal 10 to
- PCI device 00:14.0 write the parameter as:
+ mapping provided in the IVRS ACPI table.
+ By default, PCI segment is 0, and can be omitted.
+
+ For example, to map IOAPIC-ID decimal 10 to
+ PCI segment 0x1 and PCI device 00:14.0,
+ write the parameter as:
+ ivrs_ioapic=10@0001:00:14.0
+
+ Deprecated formats:
+ * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
+ write the parameter as:
ivrs_ioapic[10]=00:14.0
+ * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
+ PCI device 00:14.0 write the parameter as:
+ ivrs_ioapic[10]=0001:00:14.0
- ivrs_hpet [HW,X86_64]
+ ivrs_hpet [HW,X86-64]
Provide an override to the HPET-ID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map HPET-ID decimal 0 to
- PCI device 00:14.0 write the parameter as:
+ mapping provided in the IVRS ACPI table.
+ By default, PCI segment is 0, and can be omitted.
+
+ For example, to map HPET-ID decimal 10 to
+ PCI segment 0x1 and PCI device 00:14.0,
+ write the parameter as:
+ ivrs_hpet=10@0001:00:14.0
+
+ Deprecated formats:
+ * To map HPET-ID decimal 0 to PCI device 00:14.0
+ write the parameter as:
ivrs_hpet[0]=00:14.0
+ * To map HPET-ID decimal 10 to PCI segment 0x1 and
+ PCI device 00:14.0 write the parameter as:
+ ivrs_ioapic[10]=0001:00:14.0
- ivrs_acpihid [HW,X86_64]
+ ivrs_acpihid [HW,X86-64]
Provide an override to the ACPI-HID:UID<->DEVICE-ID
- mapping provided in the IVRS ACPI table. For
- example, to map UART-HID:UID AMD0020:0 to
- PCI device 00:14.5 write the parameter as:
+ mapping provided in the IVRS ACPI table.
+ By default, PCI segment is 0, and can be omitted.
+
+ For example, to map UART-HID:UID AMD0020:0 to
+ PCI segment 0x1 and PCI device ID 00:14.5,
+ write the parameter as:
+ ivrs_acpihid=AMD0020:0@0001:00:14.5
+
+ Deprecated formats:
+ * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
+ PCI device ID 00:14.5, write the parameter as:
ivrs_acpihid[00:14.5]=AMD0020:0
+ * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
+ PCI device ID 00:14.5, write the parameter as:
+ ivrs_acpihid[0001:00:14.5]=AMD0020:0
js= [HW,JOY] Analog joystick
See Documentation/input/joydev/joystick.rst.
- nokaslr [KNL]
- When CONFIG_RANDOMIZE_BASE is set, this disables
- kernel and module base offset ASLR (Address Space
- Layout Randomization).
-
kasan_multi_shot
[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
report on every invalid memory access. Without this
parameter KASAN will print report only for the first
invalid access.
- keepinitrd [HW,ARM]
+ keep_bootcon [KNL]
+ Do not unregister boot console at start. This is only
+ useful for debugging when something happens in the window
+ between unregistering the boot console and initializing
+ the real console.
+
+ keepinitrd [HW,ARM] See retain_initrd.
kernelcore= [KNL,X86,IA-64,PPC]
Format: nn[KMGTPE] | nn% | "mirror"
@@ -2022,10 +2499,25 @@
kms, kbd format: kms,kbd
kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
+ kgdboc_earlycon= [KGDB,HW]
+ If the boot console provides the ability to read
+ characters and can work in polling mode, you can use
+ this parameter to tell kgdb to use it as a backend
+ until the normal console is registered. Intended to
+ be used together with the kgdboc parameter which
+ specifies the normal console to transition to.
+
+ The name of the early console should be specified
+ as the value of this parameter. Note that the name of
+ the early console might be different than the tty
+ name passed to kgdboc. It's OK to leave the value
+ blank and the first boot console that implements
+ read() will be picked.
+
kgdbwait [KGDB] Stop kernel execution and enter the
kernel debugger at the earliest opportunity.
- kmac= [MIPS] korina ethernet MAC address.
+ kmac= [MIPS] Korina ethernet MAC address.
Configure the RouterBoard 532 series on-chip
Ethernet adapter MAC address.
@@ -2054,16 +2546,43 @@
0: force disabled
1: force enabled
+ kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
+ CONFIG_KUNIT to be set to be fully enabled. The
+ default value can be overridden via
+ KUNIT_DEFAULT_ENABLED.
+ Default is 1 (enabled)
+
kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
Default is 0 (don't ignore, but inject #GP)
+ kvm.eager_page_split=
+ [KVM,X86] Controls whether or not KVM will try to
+ proactively split all huge pages during dirty logging.
+ Eager page splitting reduces interruptions to vCPU
+ execution by eliminating the write-protection faults
+ and MMU lock contention that would otherwise be
+ required to split huge pages lazily.
+
+ VM workloads that rarely perform writes or that write
+ only to a small region of VM memory may benefit from
+ disabling eager page splitting to allow huge pages to
+ still be used for reads.
+
+ The behavior of eager page splitting depends on whether
+ KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
+ disabled, all huge pages in a memslot will be eagerly
+ split when dirty logging is enabled on that memslot. If
+ enabled, eager page splitting will be performed during
+ the KVM_CLEAR_DIRTY ioctl, and only for the pages being
+ cleared.
+
+ Eager page splitting is only supported when kvm.tdp_mmu=Y.
+
+ Default is Y (on).
+
kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
Default is false (don't support).
- kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
- KVM MMU at runtime.
- Default is 0 (off)
-
kvm.nx_huge_pages=
[KVM] Controls the software workaround for the
X86_BUG_ITLB_MULTIHIT bug.
@@ -2081,14 +2600,42 @@
[KVM] Controls how many 4KiB pages are periodically zapped
back to huge pages. 0 disables the recovery, otherwise if
the value is N KVM will zap 1/Nth of the 4KiB pages every
- minute. The default is 60.
+ period (see below). The default is 60.
- kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
- Default is 1 (enabled)
+ kvm.nx_huge_pages_recovery_period_ms=
+ [KVM] Controls the time period at which KVM zaps 4KiB pages
+ back to huge pages. If the value is a non-zero N, KVM will
+ zap a portion (see ratio above) of the pages every N msecs.
+ If the value is 0 (the default), KVM will pick a period based
+ on the ratio, such that a page is zapped after 1 hour on average.
+
+ kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
+ KVM/SVM. Default is 1 (enabled).
+
+ kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
+ a.k.a. Two-Dimensional Page Tables. Default is 1
+ (enabled). Disable by KVM if hardware lacks support
+ for NPT.
+
+ kvm-arm.mode=
+ [KVM,ARM] Select one of KVM/arm64's modes of operation.
+
+ none: Forcefully disable KVM.
+
+ nvhe: Standard nVHE-based mode, without support for
+ protected guests.
- kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
- for all guests.
- Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
+ protected: nVHE-based mode with support for guests whose
+ state is kept private from the host.
+
+ nested: VHE-based mode with support for nested
+ virtualization. Requires at least ARMv8.3
+ hardware.
+
+ Defaults to VHE/nVHE based on hardware support. Setting
+ mode to "protected" will disable kexec and hibernation
+ for the host. "nested" is experimental and should be
+ used with extreme caution.
kvm-arm.vgic_v3_group0_trap=
[KVM,ARM] Trap guest accesses to GICv3 group-0
@@ -2106,26 +2653,41 @@
[KVM,ARM] Allow use of GICv4 for direct injection of
LPIs.
- kvm-intel.ept= [KVM,Intel] Disable extended page tables
- (virtualized MMU) support on capable Intel chips.
- Default is 1 (enabled)
+ kvm_cma_resv_ratio=n [PPC]
+ Reserves given percentage from system memory area for
+ contiguous memory allocation for KVM hash pagetable
+ allocation.
+ By default it reserves 5% of total system memory.
+ Format: <integer>
+ Default: 5
+
+ kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
+ a.k.a. Two-Dimensional Page Tables. Default is 1
+ (enabled). Disable by KVM if hardware lacks support
+ for EPT.
kvm-intel.emulate_invalid_guest_state=
- [KVM,Intel] Enable emulation of invalid guest states
- Default is 0 (disabled)
+ [KVM,Intel] Control whether to emulate invalid guest
+ state. Ignored if kvm-intel.enable_unrestricted_guest=1,
+ as guest state is never invalid for unrestricted
+ guests. This param doesn't apply to nested guests (L2),
+ as KVM never emulates invalid L2 guest state.
+ Default is 1 (enabled).
kvm-intel.flexpriority=
- [KVM,Intel] Disable FlexPriority feature (TPR shadow).
- Default is 1 (enabled)
+ [KVM,Intel] Control KVM's use of FlexPriority feature
+ (TPR shadow). Default is 1 (enabled). Disable by KVM if
+ hardware lacks support for it.
kvm-intel.nested=
- [KVM,Intel] Enable VMX nesting (nVMX).
- Default is 0 (disabled)
+ [KVM,Intel] Control nested virtualization feature in
+ KVM/VMX. Default is 1 (enabled).
kvm-intel.unrestricted_guest=
- [KVM,Intel] Disable unrestricted guest feature
- (virtualized real and unpaged mode) on capable
- Intel chips. Default is 1 (enabled)
+ [KVM,Intel] Control KVM's use of unrestricted guest
+ feature (virtualized real and unpaged mode). Default
+ is 1 (enabled). Disable by KVM if EPT is disabled or
+ hardware lacks support for it.
kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
CVE-2018-3620.
@@ -2139,9 +2701,27 @@
Default is cond (do L1 cache flush in specific instances)
- kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
- feature (tagged TLBs) on capable Intel chips.
- Default is 1 (enabled)
+ kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
+ Identification feature (tagged TLBs). Default is 1
+ (enabled). Disable by KVM if hardware lacks support
+ for it.
+
+ l1d_flush= [X86,INTEL]
+ Control mitigation for L1D based snooping vulnerability.
+
+ Certain CPUs are vulnerable to an exploit against CPU
+ internal buffers which can forward information to a
+ disclosure gadget under certain conditions.
+
+ In vulnerable processors, the speculatively
+ forwarded data can be used in a cache side channel
+ attack, to access data to which the attacker does
+ not have direct access.
+
+ This parameter controls the mitigation. The
+ options are:
+
+ on - enable the interface for the mitigation
l1tf= [X86] Control mitigation of the L1TF vulnerability on
affected CPUs
@@ -2215,9 +2795,10 @@
lapic [X86-32,APIC] Enable the local APIC even if BIOS
disabled it.
- lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
+ lapic= [X86,APIC] Do not use TSC deadline
value for LAPIC timer one-shot implementation. Default
back to the programmable timer unit in the LAPIC.
+ Format: notscdeadline
lapic_timer_c2_ok [X86,APIC] trust the local apic timer
in C2 power state.
@@ -2238,14 +2819,14 @@
when set.
Format: <int>
- libata.force= [LIBATA] Force configurations. The format is comma
- separated list of "[ID:]VAL" where ID is
- PORT[.DEVICE]. PORT and DEVICE are decimal numbers
- matching port, link or device. Basically, it matches
- the ATA ID string printed on console by libata. If
- the whole ID part is omitted, the last PORT and DEVICE
- values are used. If ID hasn't been specified yet, the
- configuration applies to all ports, links and devices.
+ libata.force= [LIBATA] Force configurations. The format is a comma-
+ separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
+ PORT and DEVICE are decimal numbers matching port, link
+ or device. Basically, it matches the ATA ID string
+ printed on console by libata. If the whole ID part is
+ omitted, the last PORT and DEVICE values are used. If
+ ID hasn't been specified yet, the configuration applies
+ to all ports, links and devices.
If only DEVICE is omitted, the parameter applies to
the port and all links and devices behind it. DEVICE
@@ -2255,7 +2836,7 @@
host link and device attached to it.
The VAL specifies the configuration to force. As long
- as there's no ambiguity shortcut notation is allowed.
+ as there is no ambiguity, shortcut notation is allowed.
For example, both 1.5 and 1.5G would work for 1.5Gbps.
The following configurations can be forced.
@@ -2268,29 +2849,68 @@
udma[/][16,25,33,44,66,100,133] notation is also
allowed.
+ * nohrst, nosrst, norst: suppress hard, soft and both
+ resets.
+
+ * rstonce: only attempt one reset during hot-unplug
+ link recovery.
+
+ * [no]dbdelay: Enable or disable the extra 200ms delay
+ before debouncing a link PHY and device presence
+ detection.
+
* [no]ncq: Turn on or off NCQ.
- * [no]ncqtrim: Turn off queued DSM TRIM.
+ * [no]ncqtrim: Enable or disable queued DSM TRIM.
+
+ * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
+
+ * [no]trim: Enable or disable (unqueued) TRIM.
+
+ * trim_zero: Indicate that TRIM command zeroes data.
+
+ * max_trim_128m: Set 128M maximum trim size limit.
+
+ * [no]dma: Turn on or off DMA transfers.
+
+ * atapi_dmadir: Enable ATAPI DMADIR bridge support.
+
+ * atapi_mod16_dma: Enable the use of ATAPI DMA for
+ commands that are not a multiple of 16 bytes.
+
+ * [no]dmalog: Enable or disable the use of the
+ READ LOG DMA EXT command to access logs.
+
+ * [no]iddevlog: Enable or disable access to the
+ identify device data log.
+
+ * [no]logdir: Enable or disable access to the general
+ purpose log directory.
+
+ * max_sec_128: Set transfer size limit to 128 sectors.
+
+ * max_sec_1024: Set or clear transfer size limit to
+ 1024 sectors.
- * nohrst, nosrst, norst: suppress hard, soft
- and both resets.
+ * max_sec_lba48: Set or clear transfer size limit to
+ 65535 sectors.
- * rstonce: only attempt one reset during
- hot-unplug link recovery
+ * [no]lpm: Enable or disable link power management.
- * dump_id: dump IDENTIFY data.
+ * [no]setxfer: Indicate if transfer speed mode setting
+ should be skipped.
- * atapi_dmadir: Enable ATAPI DMADIR bridge support
+ * [no]fua: Disable or enable FUA (Force Unit Access)
+ support for devices supporting this feature.
+
+ * dump_id: Dump IDENTIFY data.
* disable: Disable this device.
If there are multiple matching configurations changing
the same attribute, the last one is used.
- memblock=debug [KNL] Enable memblock debug messages.
-
- load_ramdisk= [RAM] List of ramdisks to load from floppy
- See Documentation/admin-guide/blockdev/ramdisk.rst.
+ load_ramdisk= [RAM] [Deprecated]
lockd.nlm_grace_period=P [NFS] Assign grace period.
Format: <integer>
@@ -2313,6 +2933,38 @@
to extract confidential information from the kernel
are also disabled.
+ locktorture.acq_writer_lim= [KNL]
+ Set the time limit in jiffies for a lock
+ acquisition. Acquisitions exceeding this limit
+ will result in a splat once they do complete.
+
+ locktorture.bind_readers= [KNL]
+ Specify the list of CPUs to which the readers are
+ to be bound.
+
+ locktorture.bind_writers= [KNL]
+ Specify the list of CPUs to which the writers are
+ to be bound.
+
+ locktorture.call_rcu_chains= [KNL]
+ Specify the number of self-propagating call_rcu()
+ chains to set up. These are used to ensure that
+ there is a high probability of an RCU grace period
+ in progress at any given time. Defaults to 0,
+ which disables these call_rcu() chains.
+
+ locktorture.long_hold= [KNL]
+ Specify the duration in milliseconds for the
+ occasional long-duration lock hold time. Defaults
+ to 100 milliseconds. Select 0 to disable.
+
+ locktorture.nested_locks= [KNL]
+ Specify the maximum lock nesting depth that
+ locktorture is to exercise, up to a limit of 8
+ (MAX_NESTED_LOCKS). Specify zero to disable.
+ Note that this parameter is ineffective on types
+ of locks that do not support nested acquisition.
+
locktorture.nreaders_stress= [KNL]
Set the number of locking read-acquisition kthreads.
Defaults to being automatically set based on the
@@ -2328,6 +2980,25 @@
Set time (s) between CPU-hotplug operations, or
zero to disable CPU-hotplug testing.
+ locktorture.rt_boost= [KNL]
+ Do periodic testing of real-time lock priority
+ boosting. Select 0 to disable, 1 to boost
+ only rt_mutex, and 2 to boost unconditionally.
+ Defaults to 2, which might seem to be an
+ odd choice, but which should be harmless for
+ non-real-time spinlocks, due to their disabling
+ of preemption. Note that non-realtime mutexes
+ disable boosting.
+
+ locktorture.rt_boost_factor= [KNL]
+ Number that determines how often and for how
+ long priority boosting is exercised. This is
+ scaled down by the number of writers, so that the
+ number of boosts per unit time remains roughly
+ constant as the number of writers increases.
+ On the other hand, the duration of each boost
+ increases with the number of writers.
+
locktorture.shuffle_interval= [KNL]
Set task-shuffle interval (jiffies). Shuffling
tasks allows some CPUs to go into dyntick-idle
@@ -2353,6 +3024,10 @@
locktorture.verbose= [KNL]
Enable additional printk() statements.
+ locktorture.writer_fifo= [KNL]
+ Run the write-side locktorture kthreads at
+ sched_set_fifo() real-time priority.
+
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
Format: <irq>
@@ -2427,11 +3102,11 @@
(machvec) in a generic kernel.
Example: machvec=hpzx1
- machtype= [Loongson] Share the same kernel image file between different
- yeeloong laptop.
+ machtype= [Loongson] Share the same kernel image file between
+ different yeeloong laptops.
Example: machtype=lemote-yeeloong-2f-7inch
- max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
+ max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
than or equal to this physical address is ignored.
maxcpus= [SMP] Maximum number of processors that an SMP kernel
@@ -2452,7 +3127,7 @@
mce [X86-32] Machine Check Exception
- mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
+ mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
md= [HW] RAID subsystems devices and level
See Documentation/admin-guide/md.rst.
@@ -2493,22 +3168,51 @@
For details see: Documentation/admin-guide/hw-vuln/mds.rst
+ mem=nn[KMG] [HEXAGON] Set the memory size.
+ Must be specified, otherwise memory size will be 0.
+
mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
- Amount of memory to be used when the kernel is not able
- to see the whole system memory or for test.
+ Amount of memory to be used in cases as follows:
+
+ 1 for test;
+ 2 when the kernel is not able to see the whole system memory;
+ 3 memory that lies after 'mem=' boundary is excluded from
+ the hypervisor, then assigned to KVM guests.
+ 4 to limit the memory available for kdump kernel.
+
+ [ARC,MICROBLAZE] - the limit applies only to low memory,
+ high memory is not affected.
+
+ [ARM64] - only limits memory covered by the linear
+ mapping. The NOMAP regions are not affected.
+
[X86] Work as limiting max address. Use together
with memmap= to avoid physical address space collisions.
Without memmap= PCI devices could be placed at addresses
belonging to unused RAM.
+ Note that this only takes effects during boot time since
+ in above case 3, memory may need be hot added after boot
+ if system memory of hypervisor is not sufficient.
+
+ mem=nn[KMG]@ss[KMG]
+ [ARM,MIPS] - override the memory layout reported by
+ firmware.
+ Define a memory region of size nn[KMG] starting at
+ ss[KMG].
+ Multiple different regions can be specified with
+ multiple mem= parameters on the command line.
+
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
memory.
+ memblock=debug [KNL] Enable memblock debug messages.
+
memchunk=nn[KMG]
[KNL,SH] Allow user to override the default size for
per-device physically contiguous DMA buffers.
- memhp_default_state=online/offline
+ memhp_default_state=online/offline/online_kernel/online_movable
[KNL] Set the initial state for the memory hotplug
onlining policy. If not specified, the default value is
set according to the
@@ -2523,7 +3227,7 @@
option description.
memmap=nn[KMG]@ss[KMG]
- [KNL] Force usage of a specific region of memory.
+ [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
Region of memory to be used is from ss to ss+nn.
If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
which limits max address to nn[KMG].
@@ -2585,7 +3289,26 @@
seconds. Use this parameter to check at some
other rate. 0 disables periodic checking.
- memtest= [KNL,X86,ARM,PPC] Enable memtest
+ memory_hotplug.memmap_on_memory
+ [KNL,X86,ARM] Boolean flag to enable this feature.
+ Format: {on | off (default)}
+ When enabled, runtime hotplugged memory will
+ allocate its internal metadata (struct pages,
+ those vmemmap pages cannot be optimized even
+ if hugetlb_free_vmemmap is enabled) from the
+ hotadded memory which will allow to hotadd a
+ lot of memory without requiring additional
+ memory to do so.
+ This feature is disabled by default because it
+ has some implication on large (e.g. GB)
+ allocations in some configurations (e.g. small
+ memory blocks).
+ The state of the flag can be read in
+ /sys/module/memory_hotplug/parameters/memmap_on_memory.
+ Note that even when enabled, there are a few cases where
+ the feature is not effective.
+
+ memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
Format: <integer>
default : 0 <disable>
Specifies the number of memtest passes to be
@@ -2603,7 +3326,7 @@
mem_encrypt=on: Activate SME
mem_encrypt=off: Do not activate SME
- Refer to Documentation/virt/kvm/amd-memory-encryption.rst
+ Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
for details on when memory encryption can be activated.
mem_sleep_default= [SUSPEND] Default system suspend mode:
@@ -2612,9 +3335,6 @@
deep - Suspend-To-RAM or equivalent (if supported)
See Documentation/admin-guide/pm/sleep-states.rst.
- meye.*= [HW] Set MotionEye Camera parameters
- See Documentation/media/v4l-drivers/meye.rst.
-
mfgpt_irq= [IA-32] Specify the IRQ to use for the
Multi-Function General Purpose Timers on AMD Geode
platforms.
@@ -2626,7 +3346,12 @@
mga= [HW,DRM]
- min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
+ microcode.force_minrev= [X86]
+ Format: <bool>
+ Enable or disable the microcode minimal revision
+ enforcement for the runtime microcode loader.
+
+ min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
physical address is ignored.
mini2440= [ARM,HW,KNL]
@@ -2648,7 +3373,7 @@
touchscreen support is not enabled in the mainstream
kernel as of 2.6.30, a preliminary port can be found
in the "bleeding edge" mini2440 support kernel at
- http://repo.or.cz/w/linux-2.6/mini2440.git
+ https://repo.or.cz/w/linux-2.6/mini2440.git
mitigations=
[X86,PPC,S390,ARM64] Control optional mitigations for
@@ -2660,18 +3385,25 @@
Disable all optional CPU mitigations. This
improves system performance, but it may also
expose users to several CPU vulnerabilities.
- Equivalent to: nopti [X86,PPC]
- kpti=0 [ARM64]
- nospectre_v1 [X86,PPC]
+ Equivalent to: if nokaslr then kpti=0 [ARM64]
+ gather_data_sampling=off [X86]
+ kvm.nx_huge_pages=off [X86]
+ l1tf=off [X86]
+ mds=off [X86]
+ mmio_stale_data=off [X86]
+ no_entry_flush [PPC]
+ no_uaccess_flush [PPC]
nobp=0 [S390]
+ nopti [X86,PPC]
+ nospectre_bhb [ARM64]
+ nospectre_v1 [X86,PPC]
nospectre_v2 [X86,PPC,S390,ARM64]
- spectre_v2_user=off [X86]
+ retbleed=off [X86]
spec_store_bypass_disable=off [X86,PPC]
+ spectre_v2_user=off [X86]
+ srbds=off [X86,INTEL]
ssbd=force-off [ARM64]
- l1tf=off [X86]
- mds=off [X86]
tsx_async_abort=off [X86]
- kvm.nx_huge_pages=off [X86]
Exceptions:
This does not have any effect on
@@ -2693,6 +3425,8 @@
Equivalent to: l1tf=flush,nosmt [X86]
mds=full,nosmt [X86]
tsx_async_abort=full,nosmt [X86]
+ mmio_stale_data=full,nosmt [X86]
+ retbleed=auto,nosmt [X86]
mminit_loglevel=
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
@@ -2702,6 +3436,62 @@
log everything. Information is printed at KERN_DEBUG
so loglevel=8 may also need to be specified.
+ mmio_stale_data=
+ [X86,INTEL] Control mitigation for the Processor
+ MMIO Stale Data vulnerabilities.
+
+ Processor MMIO Stale Data is a class of
+ vulnerabilities that may expose data after an MMIO
+ operation. Exposed data could originate or end in
+ the same CPU buffers as affected by MDS and TAA.
+ Therefore, similar to MDS and TAA, the mitigation
+ is to clear the affected CPU buffers.
+
+ This parameter controls the mitigation. The
+ options are:
+
+ full - Enable mitigation on vulnerable CPUs
+
+ full,nosmt - Enable mitigation and disable SMT on
+ vulnerable CPUs.
+
+ off - Unconditionally disable mitigation
+
+ On MDS or TAA affected machines,
+ mmio_stale_data=off can be prevented by an active
+ MDS or TAA mitigation as these vulnerabilities are
+ mitigated with the same mechanism so in order to
+ disable this mitigation, you need to specify
+ mds=off and tsx_async_abort=off too.
+
+ Not specifying this option is equivalent to
+ mmio_stale_data=full.
+
+ For details see:
+ Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
+
+ <module>.async_probe[=<bool>] [KNL]
+ If no <bool> value is specified or if the value
+ specified is not a valid <bool>, enable asynchronous
+ probe on this module. Otherwise, enable/disable
+ asynchronous probe on this module as indicated by the
+ <bool> value. See also: module.async_probe
+
+ module.async_probe=<bool>
+ [KNL] When set to true, modules will use async probing
+ by default. To enable/disable async probing for a
+ specific module, use the module specific control that
+ is documented under <module>.async_probe. When both
+ module.async_probe and <module>.async_probe are
+ specified, <module>.async_probe takes precedence for
+ the specific module.
+
+ module.enable_dups_trace
+ [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
+ this means that duplicate request_module() calls will
+ trigger a WARN_ON() instead of a pr_warn(). Note that
+ if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
+ will always be issued and this option does nothing.
module.sig_enforce
[KNL] When CONFIG_MODULE_SIG is set, this means that
modules without (valid) signatures will fail to load.
@@ -2746,31 +3536,21 @@
<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
mtdparts= [MTD]
- See drivers/mtd/cmdlinepart.c.
-
- multitce=off [PPC] This parameter disables the use of the pSeries
- firmware feature for updating multiple TCE entries
- at a time.
-
- onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
-
- Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
-
- boundary - index of last SLC block on Flex-OneNAND.
- The remaining blocks are configured as MLC blocks.
- lock - Configure if Flex-OneNAND boundary should be locked.
- Once locked, the boundary cannot be changed.
- 1 indicates lock status, 0 indicates unlock status.
+ See drivers/mtd/parsers/cmdlinepart.c
mtdset= [ARM]
ARM/S3C2412 JIVE boot control
- See arch/arm/mach-s3c2412/mach-jive.c
+ See arch/arm/mach-s3c/mach-jive.c
mtouchusb.raw_coordinates=
[HW] Make the MicroTouch USB driver use raw coordinates
('y', default) or cooked coordinates ('n')
+ mtrr=debug [X86]
+ Enable printing debug information related to MTRR
+ registers at boot time.
+
mtrr_chunk_size=nn[KMG] [X86]
used for mtrr cleanup. It is largest continuous chunk
that could hold holes aka. UC entries.
@@ -2788,6 +3568,10 @@
Used for mtrr cleanup. It is spare mtrr entries number.
Set to 2 or more if your graphical card needs more.
+ multitce=off [PPC] This parameter disables the use of the pSeries
+ firmware feature for updating multiple TCE entries
+ at a time.
+
n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
netdev= [NET] Network devices parameters
@@ -2797,20 +3581,24 @@
This usage is only documented in each driver source
file if at all.
+ netpoll.carrier_timeout=
+ [NET] Specifies amount of time (in seconds) that
+ netpoll should wait for a carrier. By default netpoll
+ waits 4 seconds.
+
nf_conntrack.acct=
[NETFILTER] Enable connection tracking flow accounting
0 to disable accounting
1 to enable accounting
Default value is 0.
- nfsaddrs= [NFS] Deprecated. Use ip= instead.
- See Documentation/filesystems/nfs/nfsroot.txt.
-
- nfsroot= [NFS] nfs root filesystem for disk-less boxes.
- See Documentation/filesystems/nfs/nfsroot.txt.
+ nfs.cache_getent=
+ [NFS] sets the pathname to the program which is used
+ to update the NFS client cache entries.
- nfsrootdebug [NFS] enable nfsroot debugging messages.
- See Documentation/filesystems/nfs/nfsroot.txt.
+ nfs.cache_getent_timeout=
+ [NFS] sets the timeout after which an attempt to
+ update a cache entry is deemed to have failed.
nfs.callback_nr_threads=
[NFSv4] set the total number of threads that the
@@ -2821,17 +3609,12 @@
[NFS] set the TCP port on which the NFSv4 callback
channel should listen.
- nfs.cache_getent=
- [NFS] sets the pathname to the program which is used
- to update the NFS client cache entries.
-
- nfs.cache_getent_timeout=
- [NFS] sets the timeout after which an attempt to
- update a cache entry is deemed to have failed.
-
- nfs.idmap_cache_timeout=
- [NFS] set the maximum lifetime for idmapper cache
- entries.
+ nfs.delay_retrans=
+ [NFS] specifies the number of times the NFSv4 client
+ retries the request before returning an EAGAIN error,
+ after a reply of NFS4ERR_DELAY from the server.
+ Only applies if the softerr mount option is enabled,
+ and the specified value is >= 0.
nfs.enable_ino64=
[NFS] enable 64-bit inode numbers.
@@ -2840,6 +3623,10 @@
of returning the full 64-bit number.
The default is to return 64-bit inode numbers.
+ nfs.idmap_cache_timeout=
+ [NFS] set the maximum lifetime for idmapper cache
+ entries.
+
nfs.max_session_cb_slots=
[NFSv4.1] Sets the maximum number of session
slots the client will assign to the callback
@@ -2867,21 +3654,14 @@
will be autodetected by the client, and it will fall
back to using the idmapper.
To turn off this behaviour, set the value to '0'.
+
nfs.nfs4_unique_id=
[NFS4] Specify an additional fixed unique ident-
ification string that NFSv4 clients can insert into
their nfs_client_id4 string. This is typically a
UUID that is generated at system install time.
- nfs.send_implementation_id =
- [NFSv4.1] Send client implementation identification
- information in exchange_id requests.
- If zero, no implementation identification information
- will be sent.
- The default is to send the implementation identification
- information.
-
- nfs.recover_lost_locks =
+ nfs.recover_lost_locks=
[NFSv4] Attempt to recover locks that were lost due
to a lease timeout on the server. Please note that
doing this risks data corruption, since there are
@@ -2893,7 +3673,15 @@
The default parameter value of '0' causes the kernel
not to attempt recovery of lost locks.
- nfs4.layoutstats_timer =
+ nfs.send_implementation_id=
+ [NFSv4.1] Send client implementation identification
+ information in exchange_id requests.
+ If zero, no implementation identification information
+ will be sent.
+ The default is to send the implementation identification
+ information.
+
+ nfs4.layoutstats_timer=
[NFSv4.2] Change the rate at which the kernel sends
layoutstats to the pNFS metadata server.
@@ -2902,6 +3690,11 @@
driver. A non-zero value sets the minimum interval
in seconds between layoutstats transmissions.
+ nfsd.inter_copy_offload_enable=
+ [NFSv4.2] When set to 1, the server will support
+ server-to-server copies for which this server is
+ the destination of the copy.
+
nfsd.nfs4_disable_idmapping=
[NFSv4] When set to the default of '1', the NFSv4
server will return only numeric uids and gids to
@@ -2909,6 +3702,27 @@
and gids from such clients. This is intended to ease
migration from NFSv2/v3.
+ nfsd.nfsd4_ssc_umount_timeout=
+ [NFSv4.2] When used as the destination of a
+ server-to-server copy, knfsd temporarily mounts
+ the source server. It caches the mount in case
+ it will be needed again, and discards it if not
+ used for the number of milliseconds specified by
+ this parameter.
+
+ nfsaddrs= [NFS] Deprecated. Use ip= instead.
+ See Documentation/admin-guide/nfs/nfsroot.rst.
+
+ nfsroot= [NFS] nfs root filesystem for disk-less boxes.
+ See Documentation/admin-guide/nfs/nfsroot.rst.
+
+ nfsrootdebug [NFS] enable nfsroot debugging messages.
+ See Documentation/admin-guide/nfs/nfsroot.rst.
+
+ nmi_backtrace.backtrace_idle [KNL]
+ Dump stacks even of idle CPUs in response to an
+ NMI stack-backtrace request.
+
nmi_debug= [KNL,SH] Specify one or more actions to take
when a NMI is triggered.
Format: [state][,regs][,debounce][,die]
@@ -2929,43 +3743,15 @@
These settings can be accessed at runtime via
the nmi_watchdog and hardlockup_panic sysctls.
- netpoll.carrier_timeout=
- [NET] Specifies amount of time (in seconds) that
- netpoll should wait for a carrier. By default netpoll
- waits 4 seconds.
-
no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
emulation library even if a 387 maths coprocessor
is present.
- no5lvl [X86-64] Disable 5-level paging mode. Forces
- kernel to use 4-level paging instead.
+ no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces
+ kernel to use 3-level paging instead.
- no_console_suspend
- [HW] Never suspend the console
- Disable suspending of consoles during suspend and
- hibernate operations. Once disabled, debugging
- messages can reach various consoles while the rest
- of the system is being put to sleep (ie, while
- debugging driver suspend/resume hooks). This may
- not work reliably with all consoles, but is known
- to work with serial and VGA consoles.
- To facilitate more flexible debugging, we also add
- console_suspend, a printk module parameter to control
- it. Users could use console_suspend (usually
- /sys/module/printk/parameters/console_suspend) to
- turn on/off it dynamically.
-
- novmcoredd [KNL,KDUMP]
- Disable device dump. Device dump allows drivers to
- append dump data to vmcore so you can collect driver
- specified debug info. Drivers can append the data
- without any limit and this data is stored in memory,
- so this may cause significant memory stress. Disabling
- device dump can help save memory but the driver debug
- data will be no longer available. This parameter
- is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
- is set.
+ no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces
+ kernel to use 4-level paging instead.
noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
caches in the slab allocator. Saves per-node memory,
@@ -2981,33 +3767,33 @@
noautogroup Disable scheduler automatic task group creation.
- nobats [PPC] Do not use BATs for mapping kernel lowmem
- on "Classic" PPC cores.
-
nocache [ARM]
- noclflush [BUGS=X86] Don't use the CLFLUSH instruction
+ no_console_suspend
+ [HW] Never suspend the console
+ Disable suspending of consoles during suspend and
+ hibernate operations. Once disabled, debugging
+ messages can reach various consoles while the rest
+ of the system is being put to sleep (ie, while
+ debugging driver suspend/resume hooks). This may
+ not work reliably with all consoles, but is known
+ to work with serial and VGA consoles.
+ To facilitate more flexible debugging, we also add
+ console_suspend, a printk module parameter to control
+ it. Users could use console_suspend (usually
+ /sys/module/printk/parameters/console_suspend) to
+ turn on/off it dynamically.
- nodelayacct [KNL] Disable per-task delay accounting
+ no_debug_objects
+ [KNL] Disable object debugging
nodsp [SH] Disable hardware DSP at boot time.
noefi Disable EFI runtime services support.
- noexec [IA-64]
-
- noexec [X86]
- On X86-32 available only on PAE configured kernels.
- noexec=on: enable non-executable mappings (default)
- noexec=off: disable non-executable mappings
+ no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
- nosmap [X86,PPC]
- Disable SMAP (Supervisor Mode Access Prevention)
- even if it is supported by processor.
-
- nosmep [X86,PPC]
- Disable SMEP (Supervisor Mode Execution Prevention)
- even if it is supported by processor.
+ noexec [IA-64]
noexec32 [X86-64]
This affects only 32-bit executables.
@@ -3016,60 +3802,18 @@
noexec32=off: disable non-executable mappings
read implies executable mappings
+ no_file_caps Tells the kernel not to honor file capabilities. The
+ only way then for a file to be executed with privilege
+ is to be setuid root or executed by root.
+
nofpu [MIPS,SH] Disable hardware FPU at boot time.
+ nofsgsbase [X86] Disables FSGSBASE instructions.
+
nofxsr [BUGS=X86-32] Disables x86 floating point extended
register save and restore. The kernel will only save
legacy floating-point registers on task switch.
- nohugeiomap [KNL,x86,PPC] Disable kernel huge I/O mappings.
-
- nosmt [KNL,S390] Disable symmetric multithreading (SMT).
- Equivalent to smt=1.
-
- [KNL,x86] Disable symmetric multithreading (SMT).
- nosmt=force: Force disable SMT, cannot be undone
- via the sysfs control file.
-
- nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
- (bounds check bypass). With this option data leaks are
- possible in the system.
-
- nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
- the Spectre variant 2 (indirect branch prediction)
- vulnerability. System may allow data leaks with this
- option.
-
- nospec_store_bypass_disable
- [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
-
- noxsave [BUGS=X86] Disables x86 extended register state save
- and restore using xsave. The kernel will fallback to
- enabling legacy floating-point and sse state.
-
- noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
- register states. The kernel will fall back to use
- xsave to save the states. By using this parameter,
- performance of saving the states is degraded because
- xsave doesn't support modified optimization while
- xsaveopt supports it on xsaveopt enabled systems.
-
- noxsaves [X86] Disables xsaves and xrstors used in saving and
- restoring x86 extended register state in compacted
- form of xsave area. The kernel will fall back to use
- xsaveopt and xrstor to save and restore the states
- in standard form of xsave area. By using this
- parameter, xsave area per process might occupy more
- memory on xsaves enabled systems.
-
- nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
- wfi(ARM) instruction doesn't work correctly and not to
- use it. This is also useful when using JTAG debugger.
-
- no_file_caps Tells the kernel not to honor file capabilities. The
- only way then for a file to be executed with privilege
- is to be setuid root or executed by root.
-
nohalt [IA-64] Tells the kernel not to use the power saving
function PAL_HALT_LIGHT when idle. This increases
power-consumption. On the positive side, it reduces
@@ -3077,8 +3821,35 @@
in certain environments such as networked servers or
real-time systems.
+ no_hash_pointers
+ Force pointers printed to the console or buffers to be
+ unhashed. By default, when a pointer is printed via %p
+ format string, that pointer is "hashed", i.e. obscured
+ by hashing the pointer value. This is a security feature
+ that hides actual kernel addresses from unprivileged
+ users, but it also makes debugging the kernel more
+ difficult since unequal pointers can no longer be
+ compared. However, if this command-line option is
+ specified, then all normal pointers will have their true
+ value printed. This option should only be specified when
+ debugging the kernel. Please do not use on production
+ kernels.
+
nohibernate [HIBERNATION] Disable hibernation and resume.
+ nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to
+ busy wait in do_idle() and not use the arch_cpu_idle()
+ implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
+ to be effective. This is useful on platforms where the
+ sleep(SH) or wfi(ARM,ARM64) instructions do not work
+ correctly or when doing power measurements to evaluate
+ the impact of the sleep instructions. This is also
+ useful when using JTAG debugger.
+
+ nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
+
+ nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
+
nohz= [KNL] Boottime enable/disable dynamic ticks
Valid arguments: on, off
Default: on
@@ -3093,15 +3864,8 @@
just as if they had also been called out in the
rcu_nocbs= boot parameter.
- noiotrap [SH] Disables trapped I/O port accesses.
-
- noirqdebug [X86-32] Disables the code which attempts to detect and
- disable unhandled interrupt sources.
-
- no_timer_check [X86,APIC] Disables the code which tests for
- broken timer IRQ sources.
-
- noisapnp [ISAPNP] Disables ISA PnP code.
+ Note that this argument takes precedence over
+ the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
noinitrd [RAM] Tells the kernel not to load any configured
initial RAM disk.
@@ -3114,28 +3878,29 @@
noinvpcid [X86] Disable the INVPCID cpu feature.
+ noiotrap [SH] Disables trapped I/O port accesses.
+
+ noirqdebug [X86-32] Disables the code which attempts to detect and
+ disable unhandled interrupt sources.
+
+ noisapnp [ISAPNP] Disables ISA PnP code.
+
nojitter [IA-64] Disables jitter checking for ITC timers.
- no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
+ nokaslr [KNL]
+ When CONFIG_RANDOMIZE_BASE is set, this disables
+ kernel and module base offset ASLR (Address Space
+ Layout Randomization).
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
fault handling.
- no-vmw-sched-clock
- [X86,PV_OPS] Disable paravirtualized VMware scheduler
- clock and use the default one.
-
- no-steal-acc [X86,KVM,ARM64] Disable paravirtualized steal time
- accounting. steal time is computed, but won't
- influence scheduler behaviour
+ no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
nolapic [X86-32,APIC] Do not enable or use the local APIC.
nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
- noltlbs [PPC] Do not use large page/tlb entries for kernel
- lowmem mapping on PPC40x and PPC8xx
-
nomca [IA-64] Disable machine check abort handling
nomce [X86-32] Disable Machine Check Exception
@@ -3143,46 +3908,123 @@
nomfgpt [X86-32] Disable Multi-Function General Purpose
Timer usage (for AMD Geode machines).
+ nomodeset Disable kernel modesetting. Most systems' firmware
+ sets up a display mode and provides framebuffer memory
+ for output. With nomodeset, DRM and fbdev drivers will
+ not load if they could possibly displace the pre-
+ initialized output. Only the system framebuffer will
+ be available for use. The respective drivers will not
+ perform display-mode changes or accelerated rendering.
+
+ Useful as error fallback, or for testing and debugging.
+
+ nomodule Disable module load
+
nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
shutdown the other cpus. Instead use the REBOOT_VECTOR
irq.
- nomodule Disable module load
-
nopat [X86] Disable PAT (page attribute table extension of
pagetables) support.
nopcid [X86-64] Disable the PCID cpu feature.
+ nopku [X86] Disable Memory Protection Keys CPU feature found
+ in some Intel CPUs.
+
+ nopti [X86-64]
+ Equivalent to pti=off
+
+ nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
+ Disables the PV optimizations forcing the guest to run
+ as generic guest with no PV drivers. Currently support
+ XEN HVM, KVM, HYPER_V and VMWARE guest.
+
+ nopvspin [X86,XEN,KVM]
+ Disables the qspinlock slow path using PV optimizations
+ which allow the hypervisor to 'idle' the guest on lock
+ contention.
+
norandmaps Don't use address space randomization. Equivalent to
echo 0 > /proc/sys/kernel/randomize_va_space
noreplace-smp [X86-32,SMP] Don't replace SMP instructions
with UP alternatives
- nordrand [X86] Disable kernel use of the RDRAND and
- RDSEED instructions even if they are supported
- by the processor. RDRAND and RDSEED are still
- available to user space applications.
-
noresume [SWSUSP] Disables resume and restores original swap
space.
+ nosbagart [IA-64]
+
no-scroll [VGA] Disables scrollback.
This is required for the Braillex ib80-piezo Braille
reader made by F.H. Papenmeier (Germany).
- nosbagart [IA-64]
+ nosgx [X86-64,SGX] Disables Intel SGX kernel support.
- nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
+ nosmap [PPC]
+ Disable SMAP (Supervisor Mode Access Prevention)
+ even if it is supported by processor.
+
+ nosmep [PPC64s]
+ Disable SMEP (Supervisor Mode Execution Prevention)
+ even if it is supported by processor.
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
and disable the IO APIC. legacy for "maxcpus=0".
+ nosmt [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
+ Equivalent to smt=1.
+
+ [KNL,X86,PPC] Disable symmetric multithreading (SMT).
+ nosmt=force: Force disable SMT, cannot be undone
+ via the sysfs control file.
+
nosoftlockup [KNL] Disable the soft-lockup detector.
+ nospec_store_bypass_disable
+ [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
+
+ nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
+ history injection) vulnerability. System may allow data leaks
+ with this option.
+
+ nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
+ (bounds check bypass). With this option data leaks are
+ possible in the system.
+
+ nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
+ the Spectre variant 2 (indirect branch prediction)
+ vulnerability. System may allow data leaks with this
+ option.
+
+ no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV] Disable
+ paravirtualized steal time accounting. steal time is
+ computed, but won't influence scheduler behaviour
+
nosync [HW,M68K] Disables sync negotiation for all devices.
+ no_timer_check [X86,APIC] Disables the code which tests for
+ broken timer IRQ sources.
+
+ no_uaccess_flush
+ [PPC] Don't flush the L1-D cache after accessing user data.
+
+ novmcoredd [KNL,KDUMP]
+ Disable device dump. Device dump allows drivers to
+ append dump data to vmcore so you can collect driver
+ specified debug info. Drivers can append the data
+ without any limit and this data is stored in memory,
+ so this may cause significant memory stress. Disabling
+ device dump can help save memory but the driver debug
+ data will be no longer available. This parameter
+ is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
+ is set.
+
+ no-vmw-sched-clock
+ [X86,PV_OPS] Disable paravirtualized VMware scheduler
+ clock and use the default one.
+
nowatchdog [KNL] Disable both lockup detectors, i.e.
soft-lockup and NMI watchdog (hard-lockup).
@@ -3190,19 +4032,28 @@
nox2apic [X86-64,APIC] Do not enable x2APIC mode.
- cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
- CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
- Some features depend on CPU0. Known dependencies are:
- 1. Resume from suspend/hibernate depends on CPU0.
- Suspend/hibernate will fail if CPU0 is offline and you
- need to online CPU0 before suspend/hibernate.
- 2. PIC interrupts also depend on CPU0. CPU0 can't be
- removed if a PIC interrupt is detected.
- It's said poweroff/reboot may depend on CPU0 on some
- machines although I haven't seen such issues so far
- after CPU0 is offline on a few tested machines.
- If the dependencies are under your control, you can
- turn on cpu0_hotplug.
+ NOTE: this parameter will be ignored on systems with the
+ LEGACY_XAPIC_DISABLED bit set in the
+ IA32_XAPIC_DISABLE_STATUS MSR.
+
+ noxsave [BUGS=X86] Disables x86 extended register state save
+ and restore using xsave. The kernel will fallback to
+ enabling legacy floating-point and sse state.
+
+ noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
+ register states. The kernel will fall back to use
+ xsave to save the states. By using this parameter,
+ performance of saving the states is degraded because
+ xsave doesn't support modified optimization while
+ xsaveopt supports it on xsaveopt enabled systems.
+
+ noxsaves [X86] Disables xsaves and xrstors used in saving and
+ restoring x86 extended register state in compacted
+ form of xsave area. The kernel will fall back to use
+ xsaveopt and xrstor to save and restore the states
+ in standard form of xsave area. By using this
+ parameter, xsave area per process might occupy more
+ memory on xsaves enabled systems.
nps_mtm_hs_ctr= [KNL,ARC]
This parameter sets the maximum duration, in
@@ -3228,7 +4079,11 @@
nr_uarts= [SERIAL] maximum number of UARTs to be registered.
- numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
+ numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
+ set up a single NUMA node spanning all memory.
+
+ numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
+ NUMA balancing.
Allowed values are enable and disable
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
@@ -3236,14 +4091,8 @@
This can be set from sysctl after boot.
See Documentation/admin-guide/sysctl/vm.rst for details.
- of_devlink [OF, KNL] Create device links between consumer and
- supplier devices by scanning the devictree to infer the
- consumer/supplier relationships. A consumer device
- will not be probed until all the supplier devices have
- probed successfully.
-
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
- See Documentation/debugging-via-ohci1394.txt for more
+ See Documentation/core-api/debugging-via-ohci1394.rst for more
info.
olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
@@ -3258,19 +4107,15 @@
For example, to override I2C bus2:
omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
- oprofile.timer= [HW]
- Use timer interrupt instead of performance counters
+ onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
- oprofile.cpu_type= Force an oprofile cpu type
- This might be useful if you have an older oprofile
- userland or if you want common events.
- Format: { arch_perfmon }
- arch_perfmon: [X86] Force use of architectural
- perfmon on Intel CPUs instead of the
- CPU specific event set.
- timer: [X86] Force use of architectural NMI
- timer mode (see also oprofile.timer
- for generic hr timer mode)
+ Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
+
+ boundary - index of last SLC block on Flex-OneNAND.
+ The remaining blocks are configured as MLC blocks.
+ lock - Configure if Flex-OneNAND boundary should be locked.
+ Once locked, the boundary cannot be changed.
+ 1 indicates lock status, 0 indicates unlock status.
oops=panic Always panic on oopses. Default is to just kill the
process, but there is a small probability of
@@ -3300,12 +4145,34 @@
off: turn off poisoning (default)
on: turn on poisoning
+ page_reporting.page_reporting_order=
+ [KNL] Minimal page reporting order
+ Format: <integer>
+ Adjust the minimal page reporting order. The page
+ reporting is disabled when it exceeds MAX_PAGE_ORDER.
+
panic= [KNL] Kernel behaviour on panic: delay <timeout>
timeout > 0: seconds before rebooting
timeout = 0: wait forever
timeout < 0: reboot immediately
Format: <timeout>
+ panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
+ Format: <hex>[,nousertaint]
+ Hexadecimal bitmask representing the set of TAINT flags
+ that will cause the kernel to panic when add_taint() is
+ called with any of the flags in this set.
+ The optional switch "nousertaint" can be utilized to
+ prevent userspace forced crashes by writing to sysctl
+ /proc/sys/kernel/tainted any flagset matching with the
+ bitmask set on panic_on_taint.
+ See Documentation/admin-guide/tainted-kernels.rst for
+ extra details on the taint flags that users can pick
+ to compose the bitmask to assign to panic_on_taint.
+
+ panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump
+ on a WARN().
+
panic_print= Bitmask for printing system info when panic happens.
User can chose combination of the following bits:
bit 0: print all tasks info
@@ -3314,17 +4181,11 @@
bit 3: print locks info if CONFIG_LOCKDEP is on
bit 4: print ftrace buffer
bit 5: print all printk messages in buffer
-
- panic_on_warn panic() instead of WARN(). Useful to cause kdump
- on a WARN().
-
- crash_kexec_post_notifiers
- Run kdump after running panic-notifiers and dumping
- kmsg. This only for the users who doubt kdump always
- succeeds in any situation.
- Note that this also increases risks of kdump failure,
- because some panic notifiers can make the crashed
- kernel more unstable.
+ bit 6: print all CPUs backtrace (if available in the arch)
+ *Be aware* that this option may print a _lot_ of lines,
+ so there are risks of losing older messages in the log.
+ Use this option carefully, maybe worth to setup a
+ bigger log buffer with "log_buf_len" along with this.
parkbd.port= [HW] Parallel port number the keyboard adapter is
connected to, default is 0.
@@ -3355,17 +4216,103 @@
Currently this function knows 686a and 8231 chips.
Format: [spp|ps2|epp|ecp|ecpepp]
- pause_on_oops=
+ pata_legacy.all= [HW,LIBATA]
+ Format: <int>
+ Set to non-zero to probe primary and secondary ISA
+ port ranges on PCI systems where no PCI PATA device
+ has been found at either range. Disabled by default.
+
+ pata_legacy.autospeed= [HW,LIBATA]
+ Format: <int>
+ Set to non-zero if a chip is present that snoops speed
+ changes. Disabled by default.
+
+ pata_legacy.ht6560a= [HW,LIBATA]
+ Format: <int>
+ Set to 1, 2, or 3 for HT 6560A on the primary channel,
+ the secondary channel, or both channels respectively.
+ Disabled by default.
+
+ pata_legacy.ht6560b= [HW,LIBATA]
+ Format: <int>
+ Set to 1, 2, or 3 for HT 6560B on the primary channel,
+ the secondary channel, or both channels respectively.
+ Disabled by default.
+
+ pata_legacy.iordy_mask= [HW,LIBATA]
+ Format: <int>
+ IORDY enable mask. Set individual bits to allow IORDY
+ for the respective channel. Bit 0 is for the first
+ legacy channel handled by this driver, bit 1 is for
+ the second channel, and so on. The sequence will often
+ correspond to the primary legacy channel, the secondary
+ legacy channel, and so on, but the handling of a PCI
+ bus and the use of other driver options may interfere
+ with the sequence. By default IORDY is allowed across
+ all channels.
+
+ pata_legacy.opti82c46x= [HW,LIBATA]
+ Format: <int>
+ Set to 1, 2, or 3 for Opti 82c611A on the primary
+ channel, the secondary channel, or both channels
+ respectively. Disabled by default.
+
+ pata_legacy.opti82c611a= [HW,LIBATA]
+ Format: <int>
+ Set to 1, 2, or 3 for Opti 82c465MV on the primary
+ channel, the secondary channel, or both channels
+ respectively. Disabled by default.
+
+ pata_legacy.pio_mask= [HW,LIBATA]
+ Format: <int>
+ PIO mode mask for autospeed devices. Set individual
+ bits to allow the use of the respective PIO modes.
+ Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
+ All modes allowed by default.
+
+ pata_legacy.probe_all= [HW,LIBATA]
+ Format: <int>
+ Set to non-zero to probe tertiary and further ISA
+ port ranges on PCI systems. Disabled by default.
+
+ pata_legacy.probe_mask= [HW,LIBATA]
+ Format: <int>
+ Probe mask for legacy ISA PATA ports. Depending on
+ platform configuration and the use of other driver
+ options up to 6 legacy ports are supported: 0x1f0,
+ 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
+ of individual ports can be disabled by setting the
+ corresponding bits in the mask to 1. Bit 0 is for
+ the first port in the list above (0x1f0), and so on.
+ By default all supported ports are probed.
+
+ pata_legacy.qdi= [HW,LIBATA]
+ Format: <int>
+ Set to non-zero to probe QDI controllers. By default
+ set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
+
+ pata_legacy.winbond= [HW,LIBATA]
+ Format: <int>
+ Set to non-zero to probe Winbond controllers. Use
+ the standard I/O port (0x130) if 1, otherwise the
+ value given is the I/O port to use (typically 0x1b0).
+ By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
+ 0 otherwise.
+
+ pata_platform.pio_mask= [HW,LIBATA]
+ Format: <int>
+ Supported PIO mode mask. Set individual bits to allow
+ the use of the respective PIO modes. Bit 0 is for
+ mode 0, bit 1 is for mode 1, and so on. Mode 0 only
+ allowed by default.
+
+ pause_on_oops=<int>
Halt all CPUs after the first oops has been printed for
the specified number of seconds. This is to be used if
your oopses keep scrolling off the screen.
pcbit= [HW,ISDN]
- pcd. [PARIDE]
- See header of drivers/block/paride/pcd.c.
- See also Documentation/admin-guide/blockdev/paride.rst.
-
pci=option[,option...] [PCI] various PCI subsystem options.
Some options herein operate on a specific device
@@ -3480,6 +4427,15 @@
please report a bug.
nocrs [X86] Ignore PCI host bridge windows from ACPI.
If you need to use this, please report a bug.
+ use_e820 [X86] Use E820 reservations to exclude parts of
+ PCI host bridge windows. This is a workaround
+ for BIOS defects in host bridge _CRS methods.
+ If you need to use this, please report a bug to
+ <linux-pci@vger.kernel.org>.
+ no_e820 [X86] Ignore E820 reservations for PCI host
+ bridge windows. This is the default on modern
+ hardware. If you need to use this, please report
+ a bug to <linux-pci@vger.kernel.org>.
routeirq Do IRQ routing for all PCI devices.
This is normally done in pci_enable_device(),
so this option is a temporary workaround
@@ -3532,7 +4488,9 @@
specified, e.g., 12@pci:8086:9c22:103c:198f
for 4096-byte alignment.
ecrc= Enable/disable PCIe ECRC (transaction layer
- end-to-end CRC checking).
+ end-to-end CRC checking). Only effective if
+ OS has native AER control (either granted by
+ ACPI _OSC or forced via "pcie_ports=native")
bios: Use BIOS/firmware settings. This is the
the default.
off: Turn ECRC off
@@ -3583,6 +4541,8 @@
may put more devices in an IOMMU group.
force_floating [S390] Force usage of floating interrupts.
nomio [S390] Do not use MIO instructions.
+ norid [S390] ignore the RID field and force use of
+ one PCI domain per PCI function
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
@@ -3617,9 +4577,6 @@
for debug and development, but should not be
needed on a platform with proper driver support.
- pd. [PARIDE]
- See Documentation/admin-guide/blockdev/paride.rst.
-
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
boot time.
Format: { 0 | 1 }
@@ -3632,14 +4589,8 @@
allocator. This parameter is primarily for debugging
and performance comparison.
- pf. [PARIDE]
- See Documentation/admin-guide/blockdev/paride.rst.
-
- pg. [PARIDE]
- See Documentation/admin-guide/blockdev/paride.rst.
-
pirq= [SMP,APIC] Manual mp-table setup
- See Documentation/x86/i386/IO-APIC.rst.
+ See Documentation/arch/x86/i386/IO-APIC.rst.
plip= [PPT,NET] Parallel port network link
Format: { parport<nr> | timid | 0 }
@@ -3649,6 +4600,17 @@
Override pmtimer IOPort with a hex value.
e.g. pmtmr=0x508
+ pmu_override= [PPC] Override the PMU.
+ This option takes over the PMU facility, so it is no
+ longer usable by perf. Setting this option starts the
+ PMU counters by setting MMCR0 to 0 (the FC bit is
+ cleared). If a number is given, then MMCR1 is set to
+ that number, otherwise (e.g., 'pmu_override=on'), MMCR1
+ remains 0.
+
+ pm_debug_messages [SUSPEND,KNL]
+ Enable suspend/resume debug messages during boot up.
+
pnp.debug=1 [PNP]
Enable PNP debug messages (depends on the
CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
@@ -3698,6 +4660,13 @@
Format: {"off"}
Disable Hardware Transactional Memory
+ preempt= [KNL]
+ Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
+ none - Limited to cond_resched() calls
+ voluntary - Limited to cond_resched() and might_sleep() calls
+ full - Any section that isn't explicitly preempt disabled
+ can be preempted anytime.
+
print-fatal-signals=
[KNL] debug: print fatal signals
@@ -3717,6 +4686,15 @@
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
default: disabled
+ printk.console_no_auto_verbose=
+ Disable console loglevel raise on oops, panic
+ or lockdep-detected issues (only if lock debug is on).
+ With an exception to setups with low baudrate on
+ serial console, keeping this 0 is a good choice
+ in order to provide more debug information.
+ Format: <bool>
+ default: 0 (auto_verbose is enabled)
+
printk.devkmsg={on,off,ratelimit}
Control writing to /dev/kmsg.
on - unlimited logging to /dev/kmsg from userspace
@@ -3746,9 +4724,12 @@
Param: <number> - step/bucket size as a power of 2 for
statistical time based profiling.
- prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
- before loading.
- See Documentation/admin-guide/blockdev/ramdisk.rst.
+ prompt_ramdisk= [RAM] [Deprecated]
+
+ prot_virt= [S390] enable hosting protected virtual machines
+ isolated from the hypervisor (if hardware supports
+ that).
+ Format: <bool>
psi= [KNL] Enable or disable pressure stall information
tracking.
@@ -3769,10 +4750,7 @@
pstore.backend= Specify the name of the pstore backend to use
- pt. [PARIDE]
- See Documentation/admin-guide/blockdev/paride.rst.
-
- pti= [X86_64] Control Page Table Isolation of user and
+ pti= [X86-64] Control Page Table Isolation of user and
kernel address spaces. Disabling this feature
removes hardening, but improves performance of
system calls and interrupts.
@@ -3784,9 +4762,6 @@
Not specifying this option is equivalent to pti=auto.
- nopti [X86_64]
- Equivalent to pti=off
-
pty.legacy_count=
[KNL] Number of legacy pty's. Overwrites compiled-in
default number.
@@ -3795,17 +4770,38 @@
r128= [HW,DRM]
+ radix_hcall_invalidate=on [PPC/PSERIES]
+ Disable RADIX GTSE feature and use hcall for TLB
+ invalidate.
+
raid= [HW,RAID]
See Documentation/admin-guide/md.rst.
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
See Documentation/admin-guide/blockdev/ramdisk.rst.
- random.trust_cpu={on,off}
- [KNL] Enable or disable trusting the use of the
- CPU's random number generator (if available) to
- fully seed the kernel's CRNG. Default is controlled
- by CONFIG_RANDOM_TRUST_CPU.
+ ramdisk_start= [RAM] RAM disk image start address
+
+ random.trust_cpu=off
+ [KNL] Disable trusting the use of the CPU's
+ random number generator (if available) to
+ initialize the kernel's RNG.
+
+ random.trust_bootloader=off
+ [KNL] Disable trusting the use of the a seed
+ passed by the bootloader (if available) to
+ initialize the kernel's RNG.
+
+ randomize_kstack_offset=
+ [KNL] Enable or disable kernel stack offset
+ randomization, which provides roughly 5 bits of
+ entropy, frustrating memory corruption attacks
+ that depend on stack address determinism or
+ cross-syscall address exposures. This is only
+ available on architectures that have defined
+ CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
+ Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+ Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
ras=option[,option,...] [KNL] RAS-specific options
@@ -3813,21 +4809,33 @@
Disable the Correctable Errors Collector,
see CONFIG_RAS_CEC help text.
- rcu_nocbs= [KNL]
- The argument is a cpu list, as described above,
- except that the string "all" can be used to
- specify every CPU on the system.
-
- In kernels built with CONFIG_RCU_NOCB_CPU=y, set
- the specified list of CPUs to be no-callback CPUs.
- Invocation of these CPUs' RCU callbacks will be
- offloaded to "rcuox/N" kthreads created for that
- purpose, where "x" is "p" for RCU-preempt, and
- "s" for RCU-sched, and "N" is the CPU number.
- This reduces OS jitter on the offloaded CPUs,
- which can be useful for HPC and real-time
- workloads. It can also improve energy efficiency
- for asymmetric multiprocessors.
+ rcu_nocbs[=cpu-list]
+ [KNL] The optional argument is a cpu list,
+ as described above.
+
+ In kernels built with CONFIG_RCU_NOCB_CPU=y,
+ enable the no-callback CPU mode, which prevents
+ such CPUs' callbacks from being invoked in
+ softirq context. Invocation of such CPUs' RCU
+ callbacks will instead be offloaded to "rcuox/N"
+ kthreads created for that purpose, where "x" is
+ "p" for RCU-preempt, "s" for RCU-sched, and "g"
+ for the kthreads that mediate grace periods; and
+ "N" is the CPU number. This reduces OS jitter on
+ the offloaded CPUs, which can be useful for HPC
+ and real-time workloads. It can also improve
+ energy efficiency for asymmetric multiprocessors.
+
+ If a cpulist is passed as an argument, the specified
+ list of CPUs is set to no-callback mode from boot.
+
+ Otherwise, if the '=' sign and the cpulist
+ arguments are omitted, no CPU will be set to
+ no-callback mode from boot but the mode may be
+ toggled at runtime via cpusets.
+
+ Note that this argument takes precedence over
+ the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
rcu_nocb_poll [KNL]
Rather than requiring that offloaded CPUs
@@ -3844,6 +4852,13 @@
Set maximum number of finished RCU callbacks to
process in one batch.
+ rcutree.do_rcu_barrier= [KNL]
+ Request a call to rcu_barrier(). This is
+ throttled so that userspace tests can safely
+ hammer on the sysfs variable if they so choose.
+ If triggered before the RCU grace-period machinery
+ is fully active, this will error out with EAGAIN.
+
rcutree.dump_tree= [KNL]
Dump the structure of the rcu_node combining tree
out at early boot. This is used for diagnostic
@@ -3863,26 +4878,6 @@
the propagation of recent CPU-hotplug changes up
the rcu_node combining tree.
- rcutree.use_softirq= [KNL]
- If set to zero, move all RCU_SOFTIRQ processing to
- per-CPU rcuc kthreads. Defaults to a non-zero
- value, meaning that RCU_SOFTIRQ is used by default.
- Specify rcutree.use_softirq=0 to use rcuc kthreads.
-
- rcutree.rcu_fanout_exact= [KNL]
- Disable autobalancing of the rcu_node combining
- tree. This is used by rcutorture, and might
- possibly be useful for architectures having high
- cache-to-cache transfer latencies.
-
- rcutree.rcu_fanout_leaf= [KNL]
- Change the number of CPUs assigned to each
- leaf rcu_node structure. Useful for very
- large systems, which will choose the value 64,
- and for NUMA systems with large remote-access
- latencies, which will choose a value aligned
- with the appropriate hardware boundaries.
-
rcutree.jiffies_till_first_fqs= [KNL]
Set delay from grace-period initialization to
first attempt to force quiescent states.
@@ -3918,14 +4913,21 @@
(the least-favored priority). Otherwise, when
RCU_BOOST is not set, valid values are 0-99 and
the default is zero (non-realtime operation).
-
- rcutree.rcu_nocb_gp_stride= [KNL]
- Set the number of NOCB callback kthreads in
- each group, which defaults to the square root
- of the number of CPUs. Larger numbers reduce
- the wakeup overhead on the global grace-period
- kthread, but increases that same overhead on
- each group's NOCB grace-period kthread.
+ When RCU_NOCB_CPU is set, also adjust the
+ priority of NOCB callback kthreads.
+
+ rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
+ On callback-offloaded (rcu_nocbs) CPUs,
+ RCU reduces the lock contention that would
+ otherwise be caused by callback floods through
+ use of the ->nocb_bypass list. However, in the
+ common non-flooded case, RCU queues directly to
+ the main ->cblist in order to avoid the extra
+ overhead of the ->nocb_bypass list and its lock.
+ But if there are too many callbacks queued during
+ a single jiffy, RCU pre-queues the callbacks into
+ the ->nocb_bypass queue. The definition of "too
+ many" is supplied by this kernel boot parameter.
rcutree.qhimark= [KNL]
Set threshold of queued RCU callbacks beyond which
@@ -3935,15 +4937,64 @@
Set threshold of queued RCU callbacks below which
batch limiting is re-enabled.
- rcutree.rcu_idle_gp_delay= [KNL]
- Set wakeup interval for idle CPUs that have
- RCU callbacks (RCU_FAST_NO_HZ=y).
+ rcutree.qovld= [KNL]
+ Set threshold of queued RCU callbacks beyond which
+ RCU's force-quiescent-state scan will aggressively
+ enlist help from cond_resched() and sched IPIs to
+ help CPUs more quickly reach quiescent states.
+ Set to less than zero to make this be set based
+ on rcutree.qhimark at boot time and to zero to
+ disable more aggressive help enlistment.
+
+ rcutree.rcu_delay_page_cache_fill_msec= [KNL]
+ Set the page-cache refill delay (in milliseconds)
+ in response to low-memory conditions. The range
+ of permitted values is in the range 0:100000.
+
+ rcutree.rcu_divisor= [KNL]
+ Set the shift-right count to use to compute
+ the callback-invocation batch limit bl from
+ the number of callbacks queued on this CPU.
+ The result will be bounded below by the value of
+ the rcutree.blimit kernel parameter. Every bl
+ callbacks, the softirq handler will exit in
+ order to allow the CPU to do other work.
+
+ Please note that this callback-invocation batch
+ limit applies only to non-offloaded callback
+ invocation. Offloaded callbacks are instead
+ invoked in the context of an rcuoc kthread, which
+ scheduler will preempt as it does any other task.
- rcutree.rcu_idle_lazy_gp_delay= [KNL]
- Set wakeup interval for idle CPUs that have
- only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
- Lazy RCU callbacks are those which RCU can
- prove do nothing more than free memory.
+ rcutree.rcu_fanout_exact= [KNL]
+ Disable autobalancing of the rcu_node combining
+ tree. This is used by rcutorture, and might
+ possibly be useful for architectures having high
+ cache-to-cache transfer latencies.
+
+ rcutree.rcu_fanout_leaf= [KNL]
+ Change the number of CPUs assigned to each
+ leaf rcu_node structure. Useful for very
+ large systems, which will choose the value 64,
+ and for NUMA systems with large remote-access
+ latencies, which will choose a value aligned
+ with the appropriate hardware boundaries.
+
+ rcutree.rcu_min_cached_objs= [KNL]
+ Minimum number of objects which are cached and
+ maintained per one CPU. Object size is equal
+ to PAGE_SIZE. The cache allows to reduce the
+ pressure to page allocator, also it makes the
+ whole algorithm to behave better in low memory
+ condition.
+
+ rcutree.rcu_nocb_gp_stride= [KNL]
+ Set the number of NOCB callback kthreads in
+ each group, which defaults to the square root
+ of the number of CPUs. Larger numbers reduce
+ the wakeup overhead on the global grace-period
+ kthread, but increases that same overhead on
+ each group's NOCB grace-period kthread.
rcutree.rcu_kick_kthreads= [KNL]
Cause the grace-period kthread to get an extra
@@ -3952,33 +5003,99 @@
This wake_up() will be accompanied by a
WARN_ONCE() splat and an ftrace_dump().
+ rcutree.rcu_resched_ns= [KNL]
+ Limit the time spend invoking a batch of RCU
+ callbacks to the specified number of nanoseconds.
+ By default, this limit is checked only once
+ every 32 callbacks in order to limit the pain
+ inflicted by local_clock() overhead.
+
+ rcutree.rcu_unlock_delay= [KNL]
+ In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
+ this specifies an rcu_read_unlock()-time delay
+ in microseconds. This defaults to zero.
+ Larger delays increase the probability of
+ catching RCU pointer leaks, that is, buggy use
+ of RCU-protected pointers after the relevant
+ rcu_read_unlock() has completed.
+
rcutree.sysrq_rcu= [KNL]
Commandeer a sysrq key to dump out Tree RCU's
rcu_node tree with an eye towards determining
why a new grace period has not yet started.
- rcuperf.gp_async= [KNL]
+ rcutree.use_softirq= [KNL]
+ If set to zero, move all RCU_SOFTIRQ processing to
+ per-CPU rcuc kthreads. Defaults to a non-zero
+ value, meaning that RCU_SOFTIRQ is used by default.
+ Specify rcutree.use_softirq=0 to use rcuc kthreads.
+
+ But note that CONFIG_PREEMPT_RT=y kernels disable
+ this kernel boot parameter, forcibly setting it
+ to zero.
+
+ rcuscale.gp_async= [KNL]
Measure performance of asynchronous
grace-period primitives such as call_rcu().
- rcuperf.gp_async_max= [KNL]
+ rcuscale.gp_async_max= [KNL]
Specify the maximum number of outstanding
callbacks per writer thread. When a writer
thread exceeds this limit, it invokes the
corresponding flavor of rcu_barrier() to allow
previously posted callbacks to drain.
- rcuperf.gp_exp= [KNL]
+ rcuscale.gp_exp= [KNL]
Measure performance of expedited synchronous
grace-period primitives.
- rcuperf.holdoff= [KNL]
+ rcuscale.holdoff= [KNL]
Set test-start holdoff period. The purpose of
this parameter is to delay the start of the
test until boot completes in order to avoid
interference.
- rcuperf.nreaders= [KNL]
+ rcuscale.kfree_by_call_rcu= [KNL]
+ In kernels built with CONFIG_RCU_LAZY=y, test
+ call_rcu() instead of kfree_rcu().
+
+ rcuscale.kfree_mult= [KNL]
+ Instead of allocating an object of size kfree_obj,
+ allocate one of kfree_mult * sizeof(kfree_obj).
+ Defaults to 1.
+
+ rcuscale.kfree_rcu_test= [KNL]
+ Set to measure performance of kfree_rcu() flooding.
+
+ rcuscale.kfree_rcu_test_double= [KNL]
+ Test the double-argument variant of kfree_rcu().
+ If this parameter has the same value as
+ rcuscale.kfree_rcu_test_single, both the single-
+ and double-argument variants are tested.
+
+ rcuscale.kfree_rcu_test_single= [KNL]
+ Test the single-argument variant of kfree_rcu().
+ If this parameter has the same value as
+ rcuscale.kfree_rcu_test_double, both the single-
+ and double-argument variants are tested.
+
+ rcuscale.kfree_nthreads= [KNL]
+ The number of threads running loops of kfree_rcu().
+
+ rcuscale.kfree_alloc_num= [KNL]
+ Number of allocations and frees done in an iteration.
+
+ rcuscale.kfree_loops= [KNL]
+ Number of loops doing rcuscale.kfree_alloc_num number
+ of allocations and frees.
+
+ rcuscale.minruntime= [KNL]
+ Set the minimum test run time in seconds. This
+ does not affect the data-collection interval,
+ but instead allows better measurement of things
+ like CPU consumption.
+
+ rcuscale.nreaders= [KNL]
Set number of RCU readers. The value -1 selects
N, where N is the number of CPUs. A value
"n" less than -1 selects N-n+1, where N is again
@@ -3987,27 +5104,32 @@
A value of "n" less than or equal to -N selects
a single reader.
- rcuperf.nwriters= [KNL]
+ rcuscale.nwriters= [KNL]
Set number of RCU writers. The values operate
- the same as for rcuperf.nreaders.
+ the same as for rcuscale.nreaders.
N, where N is the number of CPUs
- rcuperf.perf_type= [KNL]
+ rcuscale.scale_type= [KNL]
Specify the RCU implementation to test.
- rcuperf.shutdown= [KNL]
+ rcuscale.shutdown= [KNL]
Shut the system down after performance tests
complete. This is useful for hands-off automated
testing.
- rcuperf.verbose= [KNL]
+ rcuscale.verbose= [KNL]
Enable additional printk() statements.
- rcuperf.writer_holdoff= [KNL]
+ rcuscale.writer_holdoff= [KNL]
Write-side holdoff between grace periods,
in microseconds. The default of zero says
no holdoff.
+ rcuscale.writer_holdoff_jiffies= [KNL]
+ Additional write-side holdoff between grace
+ periods, but in jiffies. The default of zero
+ says no holdoff.
+
rcutorture.fqs_duration= [KNL]
Set duration of force_quiescent_state bursts
in microseconds.
@@ -4021,8 +5143,12 @@
in seconds.
rcutorture.fwd_progress= [KNL]
- Enable RCU grace-period forward-progress testing
+ Specifies the number of kthreads to be used
+ for RCU grace-period forward-progress testing
for the types of RCU supporting this notion.
+ Defaults to 1 kthread, values less than zero or
+ greater than the number of CPUs cause the number
+ of CPUs to be used.
rcutorture.fwd_progress_div= [KNL]
Specify the fraction of a CPU-stall-warning
@@ -4056,6 +5182,18 @@
are zero, rcutorture acts as if is interpreted
they are all non-zero.
+ rcutorture.irqreader= [KNL]
+ Run RCU readers from irq handlers, or, more
+ accurately, from a timer handler. Not all RCU
+ flavors take kindly to this sort of thing.
+
+ rcutorture.leakpointer= [KNL]
+ Leak an RCU-protected pointer out of the reader.
+ This can of course result in splats, and is
+ intended to test the ability of things like
+ CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
+ such leaks.
+
rcutorture.n_barrier_cbs= [KNL]
Set callbacks/threads for rcu_barrier() testing.
@@ -4064,6 +5202,14 @@
stress RCU, they don't participate in the actual
test, hence the "fake".
+ rcutorture.nocbs_nthreads= [KNL]
+ Set number of RCU callback-offload togglers.
+ Zero (the default) disables toggling.
+
+ rcutorture.nocbs_toggle= [KNL]
+ Set the delay in milliseconds between successive
+ callback-offload toggling attempts.
+
rcutorture.nreaders= [KNL]
Set number of RCU readers. The value -1 selects
N-1, where N is the number of CPUs. A value
@@ -4081,6 +5227,20 @@
Set time (jiffies) between CPU-hotplug operations,
or zero to disable CPU-hotplug testing.
+ rcutorture.read_exit= [KNL]
+ Set the number of read-then-exit kthreads used
+ to test the interaction of RCU updaters and
+ task-exit processing.
+
+ rcutorture.read_exit_burst= [KNL]
+ The number of times in a given read-then-exit
+ episode that a set of read-then-exit kthreads
+ is spawned.
+
+ rcutorture.read_exit_delay= [KNL]
+ The delay, in seconds, between successive
+ read-then-exit testing episodes.
+
rcutorture.shuffle_interval= [KNL]
Set task-shuffle interval (s). Shuffling tasks
allows some CPUs to go into dyntick-idle mode
@@ -4094,12 +5254,33 @@
Duration of CPU stall (s) to test RCU CPU stall
warnings, zero to disable.
+ rcutorture.stall_cpu_block= [KNL]
+ Sleep while stalling if set. This will result
+ in warnings from preemptible RCU in addition to
+ any other stall-related activity. Note that
+ in kernels built with CONFIG_PREEMPTION=n and
+ CONFIG_PREEMPT_COUNT=y, this parameter will
+ cause the CPU to pass through a quiescent state.
+ Given CONFIG_PREEMPTION=n, this will suppress
+ RCU CPU stall warnings, but will instead result
+ in scheduling-while-atomic splats.
+
+ Use of this module parameter results in splats.
+
+
rcutorture.stall_cpu_holdoff= [KNL]
Time to wait (s) after boot before inducing stall.
rcutorture.stall_cpu_irqsoff= [KNL]
Disable interrupts while stalling if set.
+ rcutorture.stall_gp_kthread= [KNL]
+ Duration (s) of forced sleep within RCU
+ grace-period kthread to test RCU CPU stall
+ warnings, zero to disable. If both stall_cpu
+ and stall_gp_kthread are specified, the
+ kthread is starved first, then the CPU.
+
rcutorture.stat_interval= [KNL]
Time (s) between statistics printk()s.
@@ -4134,11 +5315,46 @@
Dump ftrace buffer after reporting RCU CPU
stall warning.
+ rcupdate.rcu_cpu_stall_notifiers= [KNL]
+ Provide RCU CPU stall notifiers, but see the
+ warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
+ option's help text. TL;DR: You almost certainly
+ do not want rcupdate.rcu_cpu_stall_notifiers.
+
rcupdate.rcu_cpu_stall_suppress= [KNL]
Suppress RCU CPU stall warning messages.
+ rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
+ Suppress RCU CPU stall warning messages and
+ rcutorture writer stall warnings that occur
+ during early boot, that is, during the time
+ before the init task is spawned.
+
rcupdate.rcu_cpu_stall_timeout= [KNL]
Set timeout for RCU CPU stall warning messages.
+ The value is in seconds and the maximum allowed
+ value is 300 seconds.
+
+ rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
+ Set timeout for expedited RCU CPU stall warning
+ messages. The value is in milliseconds
+ and the maximum allowed value is 21000
+ milliseconds. Please note that this value is
+ adjusted to an arch timer tick resolution.
+ Setting this to zero causes the value from
+ rcupdate.rcu_cpu_stall_timeout to be used (after
+ conversion from seconds to milliseconds).
+
+ rcupdate.rcu_cpu_stall_cputime= [KNL]
+ Provide statistics on the cputime and count of
+ interrupts and tasks during the sampling period. For
+ multiple continuous RCU stalls, all sampling periods
+ begin at half of the first RCU stall timeout.
+
+ rcupdate.rcu_exp_stall_task_details= [KNL]
+ Print stack dumps of any tasks blocking the
+ current expedited RCU grace period during an
+ expedited RCU CPU stall warning.
rcupdate.rcu_expedited= [KNL]
Use expedited grace-period primitives, for
@@ -4164,10 +5380,101 @@
only normal grace-period primitives. No effect
on CONFIG_TINY_RCU kernels.
+ But note that CONFIG_PREEMPT_RT=y kernels enables
+ this kernel boot parameter, forcibly setting
+ it to the value one, that is, converting any
+ post-boot attempt at an expedited RCU grace
+ period to instead use normal non-expedited
+ grace-period processing.
+
+ rcupdate.rcu_task_collapse_lim= [KNL]
+ Set the maximum number of callbacks present
+ at the beginning of a grace period that allows
+ the RCU Tasks flavors to collapse back to using
+ a single callback queue. This switching only
+ occurs when rcupdate.rcu_task_enqueue_lim is
+ set to the default value of -1.
+
+ rcupdate.rcu_task_contend_lim= [KNL]
+ Set the minimum number of callback-queuing-time
+ lock-contention events per jiffy required to
+ cause the RCU Tasks flavors to switch to per-CPU
+ callback queuing. This switching only occurs
+ when rcupdate.rcu_task_enqueue_lim is set to
+ the default value of -1.
+
+ rcupdate.rcu_task_enqueue_lim= [KNL]
+ Set the number of callback queues to use for the
+ RCU Tasks family of RCU flavors. The default
+ of -1 allows this to be automatically (and
+ dynamically) adjusted. This parameter is intended
+ for use in testing.
+
+ rcupdate.rcu_task_ipi_delay= [KNL]
+ Set time in jiffies during which RCU tasks will
+ avoid sending IPIs, starting with the beginning
+ of a given grace period. Setting a large
+ number avoids disturbing real-time workloads,
+ but lengthens grace periods.
+
+ rcupdate.rcu_task_lazy_lim= [KNL]
+ Number of callbacks on a given CPU that will
+ cancel laziness on that CPU. Use -1 to disable
+ cancellation of laziness, but be advised that
+ doing so increases the danger of OOM due to
+ callback flooding.
+
+ rcupdate.rcu_task_stall_info= [KNL]
+ Set initial timeout in jiffies for RCU task stall
+ informational messages, which give some indication
+ of the problem for those not patient enough to
+ wait for ten minutes. Informational messages are
+ only printed prior to the stall-warning message
+ for a given grace period. Disable with a value
+ less than or equal to zero. Defaults to ten
+ seconds. A change in value does not take effect
+ until the beginning of the next grace period.
+
+ rcupdate.rcu_task_stall_info_mult= [KNL]
+ Multiplier for time interval between successive
+ RCU task stall informational messages for a given
+ RCU tasks grace period. This value is clamped
+ to one through ten, inclusive. It defaults to
+ the value three, so that the first informational
+ message is printed 10 seconds into the grace
+ period, the second at 40 seconds, the third at
+ 160 seconds, and then the stall warning at 600
+ seconds would prevent a fourth at 640 seconds.
+
rcupdate.rcu_task_stall_timeout= [KNL]
- Set timeout in jiffies for RCU task stall warning
- messages. Disable with a value less than or equal
- to zero.
+ Set timeout in jiffies for RCU task stall
+ warning messages. Disable with a value less
+ than or equal to zero. Defaults to ten minutes.
+ A change in value does not take effect until
+ the beginning of the next grace period.
+
+ rcupdate.rcu_tasks_lazy_ms= [KNL]
+ Set timeout in milliseconds RCU Tasks asynchronous
+ callback batching for call_rcu_tasks().
+ A negative value will take the default. A value
+ of zero will disable batching. Batching is
+ always disabled for synchronize_rcu_tasks().
+
+ rcupdate.rcu_tasks_rude_lazy_ms= [KNL]
+ Set timeout in milliseconds RCU Tasks
+ Rude asynchronous callback batching for
+ call_rcu_tasks_rude(). A negative value
+ will take the default. A value of zero will
+ disable batching. Batching is always disabled
+ for synchronize_rcu_tasks_rude().
+
+ rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
+ Set timeout in milliseconds RCU Tasks
+ Trace asynchronous callback batching for
+ call_rcu_tasks_trace(). A negative value
+ will take the default. A value of zero will
+ disable batching. Batching is always disabled
+ for synchronize_rcu_tasks_trace().
rcupdate.rcu_self_test= [KNL]
Run the RCU early boot self tests
@@ -4187,13 +5494,13 @@
rdt= [HW,X86,RDT]
Turn on/off individual RDT features. List is:
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
- mba.
+ mba, smba, bmec.
E.g. to turn on cmt and turn off mba use:
rdt=cmt,!mba
reboot= [KNL]
Format (x86 or x86_64):
- [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
+ [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
[[,]s[mp]#### \
[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
[[,]f[orce]
@@ -4205,6 +5512,64 @@
reboot_cpu is s[mp]#### with #### being the processor
to be used for rebooting.
+ refscale.holdoff= [KNL]
+ Set test-start holdoff period. The purpose of
+ this parameter is to delay the start of the
+ test until boot completes in order to avoid
+ interference.
+
+ refscale.lookup_instances= [KNL]
+ Number of data elements to use for the forms of
+ SLAB_TYPESAFE_BY_RCU testing. A negative number
+ is negated and multiplied by nr_cpu_ids, while
+ zero specifies nr_cpu_ids.
+
+ refscale.loops= [KNL]
+ Set the number of loops over the synchronization
+ primitive under test. Increasing this number
+ reduces noise due to loop start/end overhead,
+ but the default has already reduced the per-pass
+ noise to a handful of picoseconds on ca. 2020
+ x86 laptops.
+
+ refscale.nreaders= [KNL]
+ Set number of readers. The default value of -1
+ selects N, where N is roughly 75% of the number
+ of CPUs. A value of zero is an interesting choice.
+
+ refscale.nruns= [KNL]
+ Set number of runs, each of which is dumped onto
+ the console log.
+
+ refscale.readdelay= [KNL]
+ Set the read-side critical-section duration,
+ measured in microseconds.
+
+ refscale.scale_type= [KNL]
+ Specify the read-protection implementation to test.
+
+ refscale.shutdown= [KNL]
+ Shut down the system at the end of the performance
+ test. This defaults to 1 (shut it down) when
+ refscale is built into the kernel and to 0 (leave
+ it running) when refscale is built as a module.
+
+ refscale.verbose= [KNL]
+ Enable additional printk() statements.
+
+ refscale.verbose_batched= [KNL]
+ Batch the additional printk() statements. If zero
+ (the default) or negative, print everything. Otherwise,
+ print every Nth verbose statement, where N is the value
+ specified.
+
+ regulator_ignore_unused
+ [REGULATOR]
+ Prevents regulator framework from disabling regulators
+ that are unused, due no driver claiming them. This may
+ be useful for debug and development, but should not be
+ needed on a platform with proper driver support.
+
relax_domain_level=
[KNL, SMP] Set scheduler's default relax_domain_level.
See Documentation/admin-guide/cgroup-v1/cpusets.rst.
@@ -4220,11 +5585,6 @@
Reserves a hole at the top of the kernel virtual
address space.
- reservelow= [X86]
- Format: nn[K]
- Set the amount of memory to reserve for BIOS at
- the bottom of the address space.
-
reset_devices [KNL] Force drivers to reset the underlying device
during initialization.
@@ -4246,16 +5606,45 @@
Useful for devices that are detected asynchronously
(e.g. USB and MMC devices).
- hibernate= [HIBERNATION]
- noresume Don't check if there's a hibernation image
- present during boot.
- nocompress Don't compress/decompress hibernation images.
- no Disable hibernation and resume.
- protect_image Turn on image protection during restoration
- (that will set all pages holding image data
- during restoration read-only).
-
- retain_initrd [RAM] Keep initrd memory after extraction
+ retain_initrd [RAM] Keep initrd memory after extraction. After boot, it will
+ be accessible via /sys/firmware/initrd.
+
+ retbleed= [X86] Control mitigation of RETBleed (Arbitrary
+ Speculative Code Execution with Return Instructions)
+ vulnerability.
+
+ AMD-based UNRET and IBPB mitigations alone do not stop
+ sibling threads from influencing the predictions of other
+ sibling threads. For that reason, STIBP is used on pro-
+ cessors that support it, and mitigate SMT on processors
+ that don't.
+
+ off - no mitigation
+ auto - automatically select a migitation
+ auto,nosmt - automatically select a mitigation,
+ disabling SMT if necessary for
+ the full mitigation (only on Zen1
+ and older without STIBP).
+ ibpb - On AMD, mitigate short speculation
+ windows on basic block boundaries too.
+ Safe, highest perf impact. It also
+ enables STIBP if present. Not suitable
+ on Intel.
+ ibpb,nosmt - Like "ibpb" above but will disable SMT
+ when STIBP is not available. This is
+ the alternative for systems which do not
+ have STIBP.
+ unret - Force enable untrained return thunks,
+ only effective on AMD f15h-f17h based
+ systems.
+ unret,nosmt - Like unret, but will disable SMT when STIBP
+ is not available. This is the alternative for
+ systems which do not have STIBP.
+
+ Selecting 'auto' will choose a mitigation method at run
+ time according to the CPU.
+
+ Not specifying this option is equivalent to retbleed=auto.
rfkill.default_state=
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
@@ -4276,11 +5665,20 @@
[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
CPUs.
+ riscv_isa_fallback [RISCV]
+ When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
+ falling back to detecting extension support by parsing
+ "riscv,isa" property on devicetree systems when the
+ replacement properties are not found. See the Kconfig
+ entry for RISCV_ISA_FALLBACK.
+
ro [KNL] Mount root device read-only on boot
rodata= [KNL]
on Mark read-only kernel memory as read-only (default).
off Leave read-only kernel memory writable for debugging.
+ full Mark read-only kernel memory and aliases as read-only
+ [arm64]
rockchip.usb_uart
Enable the uart passthrough on the designated usb port
@@ -4289,7 +5687,12 @@
port and the regular usb controller gets disabled.
root= [KNL] Root filesystem
- See name_to_dev_t comment in init/do_mounts.c.
+ Usually this a a block device specifier of some kind,
+ see the early_lookup_bdev comment in
+ block/early-lookup.c for details.
+ Alternatively this can be "ram" for the legacy initial
+ ramdisk, "nfs" and "cifs" for root on a network file
+ system, or "mtd" and "ubi" for mounting from raw flash.
rootdelay= [KNL] Delay (in seconds) to pause before attempting to
mount the root filesystem
@@ -4302,6 +5705,10 @@
Useful for devices that are detected asynchronously
(e.g. USB and MMC devices).
+ rootwait= [KNL] Maximum time (in seconds) to wait for root device
+ to show up before attempting to mount the root
+ filesystem.
+
rproc_mem=nn[KMG][@address]
[KNL,ARM,CMA] Remoteproc physical memory block.
Memory area to be used by remote processor image,
@@ -4314,22 +5721,141 @@
s390_iommu= [HW,S390]
Set s390 IOTLB flushing mode
strict
- With strict flushing every unmap operation will result in
- an IOTLB flush. Default is lazy flushing before reuse,
- which is faster.
+ With strict flushing every unmap operation will result
+ in an IOTLB flush. Default is lazy flushing before
+ reuse, which is faster. Deprecated, equivalent to
+ iommu.strict=1.
+
+ s390_iommu_aperture= [KNL,S390]
+ Specifies the size of the per device DMA address space
+ accessible through the DMA and IOMMU APIs as a decimal
+ factor of the size of main memory.
+ The default is 1 meaning that one can concurrently use
+ as many DMA addresses as physical memory is installed,
+ if supported by hardware, and thus map all of memory
+ once. With a value of 2 one can map all of memory twice
+ and so on. As a special case a factor of 0 imposes no
+ restrictions other than those given by hardware at the
+ cost of significant additional memory use for tables.
sa1100ir [NET]
See drivers/net/irda/sa1100_ir.c.
- sbni= [NET] Granch SBNI12 leased line adapter
-
- sched_debug [KNL] Enables verbose scheduler debug messages.
+ sched_verbose [KNL] Enables verbose scheduler debug messages.
schedstats= [KNL,X86] Enable or disable scheduled statistics.
Allowed values are enable and disable. This feature
incurs a small amount of overhead in the scheduler
but is useful for debugging and performance tuning.
+ sched_thermal_decay_shift=
+ [KNL, SMP] Set a decay shift for scheduler thermal
+ pressure signal. Thermal pressure signal follows the
+ default decay period of other scheduler pelt
+ signals(usually 32 ms but configurable). Setting
+ sched_thermal_decay_shift will left shift the decay
+ period for the thermal pressure signal by the shift
+ value.
+ i.e. with the default pelt decay period of 32 ms
+ sched_thermal_decay_shift thermal pressure decay pr
+ 1 64 ms
+ 2 128 ms
+ and so on.
+ Format: integer between 0 and 10
+ Default is 0.
+
+ scftorture.holdoff= [KNL]
+ Number of seconds to hold off before starting
+ test. Defaults to zero for module insertion and
+ to 10 seconds for built-in smp_call_function()
+ tests.
+
+ scftorture.longwait= [KNL]
+ Request ridiculously long waits randomly selected
+ up to the chosen limit in seconds. Zero (the
+ default) disables this feature. Please note
+ that requesting even small non-zero numbers of
+ seconds can result in RCU CPU stall warnings,
+ softlockup complaints, and so on.
+
+ scftorture.nthreads= [KNL]
+ Number of kthreads to spawn to invoke the
+ smp_call_function() family of functions.
+ The default of -1 specifies a number of kthreads
+ equal to the number of CPUs.
+
+ scftorture.onoff_holdoff= [KNL]
+ Number seconds to wait after the start of the
+ test before initiating CPU-hotplug operations.
+
+ scftorture.onoff_interval= [KNL]
+ Number seconds to wait between successive
+ CPU-hotplug operations. Specifying zero (which
+ is the default) disables CPU-hotplug operations.
+
+ scftorture.shutdown_secs= [KNL]
+ The number of seconds following the start of the
+ test after which to shut down the system. The
+ default of zero avoids shutting down the system.
+ Non-zero values are useful for automated tests.
+
+ scftorture.stat_interval= [KNL]
+ The number of seconds between outputting the
+ current test statistics to the console. A value
+ of zero disables statistics output.
+
+ scftorture.stutter_cpus= [KNL]
+ The number of jiffies to wait between each change
+ to the set of CPUs under test.
+
+ scftorture.use_cpus_read_lock= [KNL]
+ Use use_cpus_read_lock() instead of the default
+ preempt_disable() to disable CPU hotplug
+ while invoking one of the smp_call_function*()
+ functions.
+
+ scftorture.verbose= [KNL]
+ Enable additional printk() statements.
+
+ scftorture.weight_single= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a zero
+ "wait" parameter. A value of -1 selects the
+ default if all other weights are -1. However,
+ if at least one weight has some other value, a
+ value of -1 will instead select a weight of zero.
+
+ scftorture.weight_single_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a
+ non-zero "wait" parameter. See weight_single.
+
+ scftorture.weight_many= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a zero
+ "wait" parameter. See weight_single.
+ Note well that setting a high probability for
+ this weighting can place serious IPI load
+ on the system.
+
+ scftorture.weight_many_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
+ scftorture.weight_all= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a zero
+ "wait" parameter. See weight_single and
+ weight_many.
+
+ scftorture.weight_all_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
xtime_lock contention on larger systems, and/or RCU lock
contention on all systems with CONFIG_MAXSMP set.
@@ -4348,27 +5874,33 @@
See security/selinux/Kconfig help text.
0 -- disable.
1 -- enable.
- Default value is set via kernel config option.
- If enabled at boot time, /selinux/disable can be used
- later to disable prior to initial policy load.
-
- apparmor= [APPARMOR] Disable or enable AppArmor at boot time
- Format: { "0" | "1" }
- See security/apparmor/Kconfig help text
- 0 -- disable.
- 1 -- enable.
- Default value is set via kernel config option.
+ Default value is 1.
serialnumber [BUGS=X86-32]
+ sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
+
shapers= [NET]
Maximal number of shapers.
+ show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
+ Limit apic dumping. The parameter defines the maximal
+ number of local apics being dumped. Also it is possible
+ to set it to "all" by meaning -- no limit here.
+ Format: { 1 (default) | 2 | ... | all }.
+ The parameter valid if only apic=debug or
+ apic=verbose is specified.
+ Example: apic=debug show_lapic=all
+
simeth= [IA-64]
simscsi=
slram= [HW,MTD]
+ slab_merge [MM]
+ Enable merging of slabs with similar size when the
+ kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
+
slab_nomerge [MM]
Disable merging of slabs with similar size. May be
necessary if there is some reason to distinguish
@@ -4380,7 +5912,7 @@
cache (risks via metadata attacks are mostly
unchanged). Debug options disable merging on their
own.
- For more information see Documentation/vm/slub.rst.
+ For more information see Documentation/mm/slub.rst.
slab_max_order= [MM, SLAB]
Determines the maximum allowed order for slabs.
@@ -4388,27 +5920,19 @@
fragmentation. Defaults to 1 for systems with
more than 32MB of RAM, 0 otherwise.
- slub_debug[=options[,slabs]] [MM, SLUB]
+ slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
Enabling slub_debug allows one to determine the
culprit if slab objects become corrupted. Enabling
slub_debug can create guard zones around objects and
may poison objects when not in use. Also tracks the
last alloc / free. For more information see
- Documentation/vm/slub.rst.
-
- slub_memcg_sysfs= [MM, SLUB]
- Determines whether to enable sysfs directories for
- memory cgroup sub-caches. 1 to enable, 0 to disable.
- The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
- Enabling this can lead to a very high number of debug
- directories and files being created under
- /sys/kernel/slub.
+ Documentation/mm/slub.rst.
slub_max_order= [MM, SLUB]
Determines the maximum allowed order for slabs.
A high setting may cause OOMs due to memory
fragmentation. For more information see
- Documentation/vm/slub.rst.
+ Documentation/mm/slub.rst.
slub_min_objects= [MM, SLUB]
The minimum number of objects per slab. SLUB will
@@ -4417,12 +5941,15 @@
the number of objects indicated. The higher the number
of objects the smaller the overhead of tracking slabs
and the less frequently locks need to be acquired.
- For more information see Documentation/vm/slub.rst.
+ For more information see Documentation/mm/slub.rst.
slub_min_order= [MM, SLUB]
Determines the minimum page order for slabs. Must be
lower than slub_max_order.
- For more information see Documentation/vm/slub.rst.
+ For more information see Documentation/mm/slub.rst.
+
+ slub_merge [MM, SLUB]
+ Same with slab_merge.
slub_nomerge [MM, SLUB]
Same with slab_nomerge. This is supported for legacy.
@@ -4431,6 +5958,24 @@
smart2= [HW]
Format: <io1>[,<io2>[,...,<io8>]]
+ smp.csd_lock_timeout= [KNL]
+ Specify the period of time in milliseconds
+ that smp_call_function() and friends will wait
+ for a CPU to release the CSD lock. This is
+ useful when diagnosing bugs involving CPUs
+ disabling interrupts for extended periods
+ of time. Defaults to 5,000 milliseconds, and
+ setting a value of zero disables this feature.
+ This feature may be more efficiently disabled
+ using the csdlock_debug- kernel parameter.
+
+ smp.panic_on_ipistall= [KNL]
+ If a csd_lock_timeout extends for more than
+ the specified number of milliseconds, panic the
+ system. By default, let CSD-lock acquisition
+ take as long as they take. Specifying 300,000
+ for this value provides a 5-minute timeout.
+
smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
smsc-ircc2.ircc_sir= [HW] SIR base I/O port
@@ -4442,7 +5987,7 @@
1: Fast pin select (default)
2: ATC IRMode
- smt [KNL,S390] Set the maximum number of threads (logical
+ smt= [KNL,MIPS,S390] Set the maximum number of threads (logical
CPUs) to use per physical CPU on systems capable of
symmetric multithreading (SMT). Will be capped to the
actual hardware limit.
@@ -4451,18 +5996,18 @@
softlockup_panic=
[KNL] Should the soft-lockup detector generate panics.
- Format: <integer>
+ Format: 0 | 1
- A nonzero value instructs the soft-lockup detector
- to panic the machine when a soft-lockup occurs. This
- is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
- which is the respective build-time switch to that
- functionality.
+ A value of 1 instructs the soft-lockup detector
+ to panic the machine when a soft-lockup occurs. It is
+ also controlled by the kernel.softlockup_panic sysctl
+ and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
+ respective build-time switch to that functionality.
softlockup_all_cpu_backtrace=
[KNL] Should the soft-lockup detector generate
backtraces on all cpus.
- Format: <integer>
+ Format: 0 | 1
sonypi.*= [HW] Sony Programmable I/O Control Device driver
See Documentation/admin-guide/laptops/sonypi.rst
@@ -4494,8 +6039,13 @@
Specific mitigations can also be selected manually:
retpoline - replace indirect branches
- retpoline,generic - google's original retpoline
- retpoline,amd - AMD-specific minimal thunk
+ retpoline,generic - Retpolines
+ retpoline,lfence - LFENCE; indirect branch
+ retpoline,amd - alias for retpoline,lfence
+ eibrs - Enhanced/Auto IBRS
+ eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
+ eibrs,lfence - Enhanced/Auto IBRS + LFENCE
+ ibrs - use IBRS to protect kernel
Not specifying this option is equivalent to
spectre_v2=auto.
@@ -4536,12 +6086,22 @@
auto - Kernel selects the mitigation depending on
the available CPU features and vulnerability.
- Default mitigation:
- If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
+ Default mitigation: "prctl"
Not specifying this option is equivalent to
spectre_v2_user=auto.
+ spec_rstack_overflow=
+ [X86] Control RAS overflow mitigation on AMD Zen CPUs
+
+ off - Disable mitigation
+ microcode - Enable microcode mitigation only
+ safe-ret - Enable sw-only safe RET mitigation (default)
+ ibpb - Enable mitigation by issuing IBPB on
+ kernel entry
+ ibpb-vmexit - Issue IBPB only on VMEXIT
+ (cloud-specific mitigation)
+
spec_store_bypass_disable=
[HW] Control Speculative Store Bypass (SSB) Disable mitigation
(Speculative Store Bypass vulnerability)
@@ -4581,7 +6141,7 @@
will disable SSB unless they explicitly opt out.
Default mitigations:
- X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
+ X86: "prctl"
On powerpc the options are:
@@ -4599,6 +6159,90 @@
spia_pedr=
spia_peddr=
+ split_lock_detect=
+ [X86] Enable split lock detection or bus lock detection
+
+ When enabled (and if hardware support is present), atomic
+ instructions that access data across cache line
+ boundaries will result in an alignment check exception
+ for split lock detection or a debug exception for
+ bus lock detection.
+
+ off - not enabled
+
+ warn - the kernel will emit rate-limited warnings
+ about applications triggering the #AC
+ exception or the #DB exception. This mode is
+ the default on CPUs that support split lock
+ detection or bus lock detection. Default
+ behavior is by #AC if both features are
+ enabled in hardware.
+
+ fatal - the kernel will send SIGBUS to applications
+ that trigger the #AC exception or the #DB
+ exception. Default behavior is by #AC if
+ both features are enabled in hardware.
+
+ ratelimit:N -
+ Set system wide rate limit to N bus locks
+ per second for bus lock detection.
+ 0 < N <= 1000.
+
+ N/A for split lock detection.
+
+
+ If an #AC exception is hit in the kernel or in
+ firmware (i.e. not while executing in user mode)
+ the kernel will oops in either "warn" or "fatal"
+ mode.
+
+ #DB exception for bus lock is triggered only when
+ CPL > 0.
+
+ srbds= [X86,INTEL]
+ Control the Special Register Buffer Data Sampling
+ (SRBDS) mitigation.
+
+ Certain CPUs are vulnerable to an MDS-like
+ exploit which can leak bits from the random
+ number generator.
+
+ By default, this issue is mitigated by
+ microcode. However, the microcode fix can cause
+ the RDRAND and RDSEED instructions to become
+ much slower. Among other effects, this will
+ result in reduced throughput from /dev/urandom.
+
+ The microcode mitigation can be disabled with
+ the following option:
+
+ off: Disable mitigation and remove
+ performance impact to RDRAND and RDSEED
+
+ srcutree.big_cpu_lim [KNL]
+ Specifies the number of CPUs constituting a
+ large system, such that srcu_struct structures
+ should immediately allocate an srcu_node array.
+ This kernel-boot parameter defaults to 128,
+ but takes effect only when the low-order four
+ bits of srcutree.convert_to_big is equal to 3
+ (decide at boot).
+
+ srcutree.convert_to_big [KNL]
+ Specifies under what conditions an SRCU tree
+ srcu_struct structure will be converted to big
+ form, that is, with an rcu_node tree:
+
+ 0: Never.
+ 1: At init_srcu_struct() time.
+ 2: When rcutorture decides to.
+ 3: Decide at boot time (default).
+ 0x1X: Above plus if high contention.
+
+ Either way, the srcu_node tree will be sized based
+ on the actual runtime number of CPUs (nr_cpu_ids)
+ instead of the compile-time CONFIG_NR_CPUS.
+
srcutree.counter_wrap_check [KNL]
Specifies how frequently to check for
grace-period sequence counter wrap for the
@@ -4616,6 +6260,32 @@
expediting. Set to zero to disable automatic
expediting.
+ srcutree.srcu_max_nodelay [KNL]
+ Specifies the number of no-delay instances
+ per jiffy for which the SRCU grace period
+ worker thread will be rescheduled with zero
+ delay. Beyond this limit, worker thread will
+ be rescheduled with a sleep delay of one jiffy.
+
+ srcutree.srcu_max_nodelay_phase [KNL]
+ Specifies the per-grace-period phase, number of
+ non-sleeping polls of readers. Beyond this limit,
+ grace period worker thread will be rescheduled
+ with a sleep delay of one jiffy, between each
+ rescan of the readers, for a grace period phase.
+
+ srcutree.srcu_retry_check_delay [KNL]
+ Specifies number of microseconds of non-sleeping
+ delay between each non-sleeping poll of readers.
+
+ srcutree.small_contention_lim [KNL]
+ Specifies the number of update-side contention
+ events per jiffy will be tolerated before
+ initiating a conversion of an srcu_struct
+ structure to big form. Note that the value of
+ srcutree.convert_to_big must have the 0x10 bit
+ set for contention-based conversions to occur.
+
ssbd= [ARM64,HW]
Speculative Store Bypass Disable control
@@ -4640,12 +6310,18 @@
growing up) the main stack are reserved for no other
mapping. Default value is 256 pages.
+ stack_depot_disable= [KNL]
+ Setting this to true through kernel command line will
+ disable the stack depot thereby saving the static memory
+ consumed by the stack hash table. By default this is set
+ to false.
+
stacktrace [FTRACE]
Enabled the stack tracer on boot up.
stacktrace_filter=[function-list]
[FTRACE] Limit the functions that the stack tracer
- will trace at boot up. function-list is a comma separated
+ will trace at boot up. function-list is a comma-separated
list of functions. This list can be changed at run
time by the stack_trace_filter file in the debugfs
tracing directory. Note, this enables stack tracing
@@ -4664,6 +6340,25 @@
stifb= [HW]
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
+ strict_sas_size=
+ [X86]
+ Format: <bool>
+ Enable or disable strict sigaltstack size checks
+ against the required signal frame size which
+ depends on the supported FPU features. This can
+ be used to filter out binaries which have
+ not yet been made aware of AT_MINSIGSTKSZ.
+
+ stress_hpt [PPC]
+ Limits the number of kernel HPT entries in the hash
+ page table to increase the rate of hash page table
+ faults on kernel addresses.
+
+ stress_slb [PPC]
+ Limits the number of kernel SLB entries, and flushes
+ them frequently to increase the rate of SLB faults
+ on kernel addresses.
+
sunrpc.min_resvport=
sunrpc.max_resvport=
[NFS,SUNRPC]
@@ -4719,28 +6414,26 @@
This parameter controls use of the Protected
Execution Facility on pSeries.
- swapaccount=[0|1]
- [KNL] Enable accounting of swap in memory resource
- controller if no parameter or 1 is given or disable
- it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
-
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
- Format: { <int> | force | noforce }
+ Format: { <int> [,<int>] | force | noforce }
<int> -- Number of I/O TLB slabs
+ <int> -- Second integer after comma. Number of swiotlb
+ areas with their own lock. Will be rounded up
+ to a power of 2.
force -- force using of bounce buffers even if they
wouldn't be automatically used by the kernel
noforce -- Never use bounce buffers (for debugging)
switches= [HW,M68k]
- sysfs.deprecated=0|1 [KNL]
- Enable/disable old style sysfs layout for old udev
- on older distributions. When this option is enabled
- very new udev will not work anymore. When this option
- is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
- in older udev will not work anymore.
- Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
- the kernel configuration.
+ sysctl.*= [KNL]
+ Set a sysctl parameter, right before loading the init
+ process, as if the value was written to the respective
+ /proc/sys/... file. Both '.' and '/' are recognized as
+ separators. Unrecognized parameters and invalid values
+ are reported in the kernel log. Sysctls registered
+ later by a loaded module cannot be set this way.
+ Example: sysctl.vm.swappiness=40
sysrq_always_enabled
[KNL]
@@ -4752,12 +6445,13 @@
Set the number of tcp_metrics_hash slots.
Default value is 8192 or 16384 depending on total
ram pages. This is used to specify the TCP metrics
- cache size. See Documentation/networking/ip-sysctl.txt
+ cache size. See Documentation/networking/ip-sysctl.rst
"tcp_no_metrics_save" section for more details.
tdfx= [HW,DRM]
- test_suspend= [SUSPEND][,N]
+ test_suspend= [SUSPEND]
+ Format: { "mem" | "standby" | "freeze" }[,N]
Specify "mem" (for Suspend-to-RAM) or "standby" (for
standby suspend) or "freeze" (for suspend type freeze)
as the system sleep state during system startup with
@@ -4776,10 +6470,6 @@
-1: disable all critical trip points in all thermal zones
<degrees C>: override all critical trip points
- thermal.nocrt= [HW,ACPI]
- Set to disable actions on ACPI thermal zone
- critical and hot trip points.
-
thermal.off= [HW,ACPI]
1: disable ACPI thermal control
@@ -4811,6 +6501,25 @@
topology updates sent by the hypervisor to this
LPAR.
+ torture.disable_onoff_at_boot= [KNL]
+ Prevent the CPU-hotplug component of torturing
+ until after init has spawned.
+
+ torture.ftrace_dump_at_shutdown= [KNL]
+ Dump the ftrace buffer at torture-test shutdown,
+ even if there were no errors. This can be a
+ very costly operation when many torture tests
+ are running concurrently, especially on systems
+ with rotating-rust storage.
+
+ torture.verbose_sleep_frequency= [KNL]
+ Specifies how many verbose printk()s should be
+ emitted between each sleep. The default of zero
+ disables verbose-printk() sleeping.
+
+ torture.verbose_sleep_duration= [KNL]
+ Duration of each verbose-printk() sleep in jiffies.
+
tp720= [HW,PS2]
tpm_suspend_pcr=[HW,TPM]
@@ -4822,22 +6531,102 @@
This will guarantee that all the other pcrs
are saved.
+ tpm_tis.interrupts= [HW,TPM]
+ Enable interrupts for the MMIO based physical layer
+ for the FIFO interface. By default it is set to false
+ (0). For more information about TPM hardware interfaces
+ defined by Trusted Computing Group (TCG) see
+ https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+
+ tp_printk [FTRACE]
+ Have the tracepoints sent to printk as well as the
+ tracing ring buffer. This is useful for early boot up
+ where the system hangs or reboots and does not give the
+ option for reading the tracing buffer or performing a
+ ftrace_dump_on_oops.
+
+ To turn off having tracepoints sent to printk,
+ echo 0 > /proc/sys/kernel/tracepoint_printk
+ Note, echoing 1 into this file without the
+ tracepoint_printk kernel cmdline option has no effect.
+
+ The tp_printk_stop_on_boot (see below) can also be used
+ to stop the printing of events to console at
+ late_initcall_sync.
+
+ ** CAUTION **
+
+ Having tracepoints sent to printk() and activating high
+ frequency tracepoints such as irq or sched, can cause
+ the system to live lock.
+
+ tp_printk_stop_on_boot [FTRACE]
+ When tp_printk (above) is set, it can cause a lot of noise
+ on the console. It may be useful to only include the
+ printing of events during boot up, as user space may
+ make the system inoperable.
+
+ This command line option will stop the printing of events
+ to console at the late_initcall_sync() time frame.
+
trace_buf_size=nn[KMG]
[FTRACE] will set tracing buffer size on each cpu.
+ trace_clock= [FTRACE] Set the clock used for tracing events
+ at boot up.
+ local - Use the per CPU time stamp counter
+ (converted into nanoseconds). Fast, but
+ depending on the architecture, may not be
+ in sync between CPUs.
+ global - Event time stamps are synchronize across
+ CPUs. May be slower than the local clock,
+ but better for some race conditions.
+ counter - Simple counting of events (1, 2, ..)
+ note, some counts may be skipped due to the
+ infrastructure grabbing the clock more than
+ once per event.
+ uptime - Use jiffies as the time stamp.
+ perf - Use the same clock that perf uses.
+ mono - Use ktime_get_mono_fast_ns() for time stamps.
+ mono_raw - Use ktime_get_raw_fast_ns() for time
+ stamps.
+ boot - Use ktime_get_boot_fast_ns() for time stamps.
+ Architectures may add more clocks. See
+ Documentation/trace/ftrace.rst for more details.
+
trace_event=[event-list]
[FTRACE] Set and start specified trace events in order
to facilitate early boot debugging. The event-list is a
- comma separated list of trace events to enable. See
+ comma-separated list of trace events to enable. See
also Documentation/trace/events.rst
+ trace_instance=[instance-info]
+ [FTRACE] Create a ring buffer instance early in boot up.
+ This will be listed in:
+
+ /sys/kernel/tracing/instances
+
+ Events can be enabled at the time the instance is created
+ via:
+
+ trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
+
+ Note, the "<system*>:" portion is optional if the event is
+ unique.
+
+ trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
+
+ will enable the "sched_switch" event (note, the "sched:" is optional, and
+ the same thing would happen if it was left off). The irq_handler_entry
+ event, and all events under the "initcall" system.
+
trace_options=[option-list]
[FTRACE] Enable or disable tracer options at boot.
The option-list is a comma delimited list of options
that can be enabled or disabled just as if you were
to echo the option name into
- /sys/kernel/debug/tracing/trace_options
+ /sys/kernel/tracing/trace_options
For example, to enable stacktrace option (to dump the
stack trace of each event), add to the command line:
@@ -4847,29 +6636,30 @@
See also Documentation/trace/ftrace.rst "trace options"
section.
- tp_printk[FTRACE]
- Have the tracepoints sent to printk as well as the
- tracing ring buffer. This is useful for early boot up
- where the system hangs or reboots and does not give the
- option for reading the tracing buffer or performing a
- ftrace_dump_on_oops.
+ trace_trigger=[trigger-list]
+ [FTRACE] Add a event trigger on specific events.
+ Set a trigger on top of a specific event, with an optional
+ filter.
- To turn off having tracepoints sent to printk,
- echo 0 > /proc/sys/kernel/tracepoint_printk
- Note, echoing 1 into this file without the
- tracepoint_printk kernel cmdline option has no effect.
+ The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
+ Where more than one trigger may be specified that are comma deliminated.
- ** CAUTION **
+ For example:
+
+ trace_trigger="sched_switch.stacktrace if prev_state == 2"
+
+ The above will enable the "stacktrace" trigger on the "sched_switch"
+ event but only trigger it if the "prev_state" of the "sched_switch"
+ event is "2" (TASK_UNINTERUPTIBLE).
+
+ See also "Event triggers" in Documentation/trace/events.rst
- Having tracepoints sent to printk() and activating high
- frequency tracepoints such as irq or sched, can cause
- the system to live lock.
traceoff_on_warning
[FTRACE] enable this option to disable tracing when a
warning is hit. This turns off "tracing_on". Tracing can
be enabled again by echoing '1' into the "tracing_on"
- file located in /sys/kernel/debug/tracing/
+ file located in /sys/kernel/tracing/
This option is useful, as it disables the trace before
the WARNING dump is called, which prevents the trace to
@@ -4886,6 +6676,29 @@
See Documentation/admin-guide/mm/transhuge.rst
for more details.
+ trusted.source= [KEYS]
+ Format: <string>
+ This parameter identifies the trust source as a backend
+ for trusted keys implementation. Supported trust
+ sources:
+ - "tpm"
+ - "tee"
+ - "caam"
+ If not specified then it defaults to iterating through
+ the trust source list starting with TPM and assigns the
+ first trust source as a backend which is initialized
+ successfully during iteration.
+
+ trusted.rng= [KEYS]
+ Format: <string>
+ The RNG used to generate key material for trusted keys.
+ Can be one of:
+ - "kernel"
+ - the same value as trusted.source: "tpm" or "tee"
+ - "default"
+ If not specified, "default" is used. In this case,
+ the RNG's choice is left to each individual trust source.
+
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
@@ -4904,6 +6717,22 @@
in situations with strict latency requirements (where
interruptions from clocksource watchdog are not
acceptable).
+ [x86] recalibrate: force recalibration against a HW timer
+ (HPET or PM timer) on systems whose TSC frequency was
+ obtained from HW or FW using either an MSR or CPUID(0x15).
+ Warn if the difference is more than 500 ppm.
+ [x86] watchdog: Use TSC as the watchdog clocksource with
+ which to check other HW timers (HPET or PM timer), but
+ only on systems where TSC has been deemed trustworthy.
+ This will be suppressed by an earlier tsc=nowatchdog and
+ can be overridden by a later tsc=nowatchdog. A console
+ message will flag any such suppression or overriding.
+
+ tsc_early_khz= [X86] Skip early TSC calibration and use the given
+ value instead. Useful when the early TSC frequency discovery
+ procedure is not reliable, such as on overclocked systems
+ with CPUID.16h support and partial CPUID.15h support.
+ Format: <unsigned int>
tsx= [X86] Control Transactional Synchronization
Extensions (TSX) feature in Intel processors that
@@ -5000,9 +6829,15 @@
unknown_nmi_panic
[X86] Cause panic on unknown NMI.
+ unwind_debug [X86-64]
+ Enable unwinder debug output. This can be
+ useful for debugging certain unwinder error
+ conditions, including corrupt stacks and
+ bad/missing unwinder metadata.
+
usbcore.authorized_default=
[USB] Default USB device authorization:
- (default -1 = authorized except for wireless USB,
+ (default -1 = authorized (same as 1),
0 = not authorized, 1 = authorized, 2 = authorized
if device connected to internal port)
@@ -5025,8 +6860,7 @@
usbcore.old_scheme_first=
[USB] Start with the old device initialization
- scheme, applies only to low and full-speed devices
- (default 0 = off).
+ scheme (default 0 = off).
usbcore.usbfs_memory_mb=
[USB] Memory limit (in MB) for buffers allocated by
@@ -5101,6 +6935,9 @@
pause after every control message);
o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
delay after resetting its port);
+ p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
+ (Reduce timeout of the SET_ADDRESS
+ request from 5000 ms to 500 ms);
Example: quirks=0781:5580:bk,0a5c:5834:gij
usbhid.mousepoll=
@@ -5145,6 +6982,7 @@
device);
j = NO_REPORT_LUNS (don't use report luns
command, uas only);
+ k = NO_SAME (do not use WRITE_SAME, uas only)
l = NOT_LOCKABLE (don't try to lock and
unlock ejectable media, not on uas);
m = MAX_SECTORS_64 (don't transfer more
@@ -5187,7 +7025,7 @@
HIGHMEM regardless of setting
of CONFIG_HIGHPTE.
- vdso= [X86,SH]
+ vdso= [X86,SH,SPARC]
On X86_32, this is an alias for vdso32=. Otherwise:
vdso=1: enable VDSO (the default)
@@ -5213,11 +7051,12 @@
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.rst.
- video.brightness_switch_enabled= [0,1]
+ video.brightness_switch_enabled= [ACPI]
+ Format: [0|1]
If set to 1, on receiving an ACPI notify event
generated by hotkey, video driver will adjust brightness
level and then send out the event to user space through
- the allocated input device; If set to 0, video driver
+ the allocated input device. If set to 0, video driver
will only send out the event without touching backlight
brightness level.
default: 1
@@ -5239,7 +7078,7 @@
Can be used multiple times for multiple devices.
vga= [BOOT,X86-32] Select a particular video mode
- See Documentation/x86/boot.rst and
+ See Documentation/arch/x86/boot.rst and
Documentation/admin-guide/svga.rst.
Use vga=ask for menu.
This is actually a boot loader parameter; the value is
@@ -5284,11 +7123,11 @@
functions are at fixed addresses, they make nice
targets for exploits that can control RIP.
- emulate [default] Vsyscalls turn into traps and are
- emulated reasonably safely. The vsyscall
- page is readable.
+ emulate Vsyscalls turn into traps and are emulated
+ reasonably safely. The vsyscall page is
+ readable.
- xonly Vsyscalls turn into traps and are
+ xonly [default] Vsyscalls turn into traps and are
emulated reasonably safely. The vsyscall
page is not readable.
@@ -5358,6 +7197,13 @@
disables both lockup detectors. Default is 10
seconds.
+ workqueue.unbound_cpus=
+ [KNL,SMP] Specify to constrain one or some CPUs
+ to use in unbound workqueues.
+ Format: <cpu-list>
+ By default, all online CPUs are available for
+ unbound workqueues.
+
workqueue.watchdog_thresh=
If CONFIG_WQ_WATCHDOG is configured, workqueue can
warn stall conditions and dump internal state to
@@ -5367,14 +7213,17 @@
it can be updated at runtime by writing to the
corresponding sysfs file.
- workqueue.disable_numa
- By default, all work items queued to unbound
- workqueues are affine to the NUMA nodes they're
- issued on, which results in better behavior in
- general. If NUMA affinity needs to be disabled for
- whatever reason, this option can be used. Note
- that this also can be controlled per-workqueue for
- workqueues visible under /sys/bus/workqueue/.
+ workqueue.cpu_intensive_thresh_us=
+ Per-cpu work items which run for longer than this
+ threshold are automatically considered CPU intensive
+ and excluded from concurrency management to prevent
+ them from noticeably delaying other per-cpu work
+ items. Default is 10000 (10ms).
+
+ If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
+ will report the work functions which violate this
+ threshold repeatedly. They are likely good
+ candidates for using WQ_UNBOUND workqueues instead.
workqueue.power_efficient
Per-cpu workqueues are generally preferred because
@@ -5391,6 +7240,18 @@
The default value of this parameter is determined by
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
+ workqueue.default_affinity_scope=
+ Select the default affinity scope to use for unbound
+ workqueues. Can be one of "cpu", "smt", "cache",
+ "numa" and "system". Default is "cache". For more
+ information, see the Affinity Scopes section in
+ Documentation/core-api/workqueue.rst.
+
+ This can be changed after boot by writing to the
+ matching /sys/module/workqueue/parameters file. All
+ workqueues with the "default" affinity scope will be
+ updated accordignly.
+
workqueue.debug_force_rr_cpu
Workqueue used to implicitly guarantee that work
items queued without explicit CPU specified are put
@@ -5402,16 +7263,16 @@
When enabled, memory and cache locality will be
impacted.
+ writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of
+ ioremap_wc().
+
+ on - Enable writecombine, use WUC for ioremap_wc()
+ off - Disable writecombine, use SUC for ioremap_wc()
+
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
default x2apic cluster mode on platforms
supporting x2apic.
- x86_intel_mid_timer= [X86-32,APBT]
- Choose timer option for x86 Intel MID platform.
- Two valid options are apbt timer only and lapic timer
- plus one apbt timer for broadcast timer.
- x86_intel_mid_timer=apbt_only | lapic_and_apbt
-
xen_512gb_limit [KNL,X86-64,XEN]
Restricts the kernel running paravirtualized under Xen
to use only up to 512 GB of RAM. The reason to do so is
@@ -5435,9 +7296,16 @@
Crash from Xen panic notifier, without executing late
panic() code such as dumping handler.
+ xen_msr_safe= [X86,XEN]
+ Format: <bool>
+ Select whether to always use non-faulting (safe) MSR
+ access functions when running as Xen PV guest. The
+ default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
+
xen_nopvspin [X86,XEN]
- Disables the ticketlock slowpath using Xen PV
- optimizations.
+ Disables the qspinlock slowpath using Xen PV optimizations.
+ This parameter is obsoleted by "nopvspin" parameter, which
+ has equivalent effect for XEN platform.
xen_nopv [X86]
Disables the PV optimizations forcing the HVM guest to
@@ -5445,6 +7313,10 @@
This option is obsoleted by the "nopv" option, which
has equivalent effect for XEN platform.
+ xen_no_vector_callback
+ [KNL,X86,XEN] Disable the vector callback for Xen
+ event channel interrupts.
+
xen_scrub_pages= [XEN]
Boolean option to control scrubbing pages before giving them back
to Xen, for use by other domains. Can be also changed at runtime
@@ -5458,10 +7330,27 @@
improve timer resolution at the expense of processing
more timer interrupts.
- nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
- Disables the PV optimizations forcing the guest to run
- as generic guest with no PV drivers. Currently support
- XEN HVM, KVM, HYPER_V and VMWARE guest.
+ xen.balloon_boot_timeout= [XEN]
+ The time (in seconds) to wait before giving up to boot
+ in case initial ballooning fails to free enough memory.
+ Applies only when running as HVM or PVH guest and
+ started with less memory configured than allowed at
+ max. Default is 180.
+
+ xen.event_eoi_delay= [XEN]
+ How long to delay EOI handling in case of event
+ storms (jiffies). Default is 10.
+
+ xen.event_loop_timeout= [XEN]
+ After which time (jiffies) the event handling loop
+ should start to delay EOI handling. Default is 2.
+
+ xen.fifo_events= [XEN]
+ Boolean parameter to disable using fifo event handling
+ even if available. Normally fifo event handling is
+ preferred over the 2-level event handling, as it is
+ fairer and the number of possible event channels is
+ much higher. Default is on (use fifo events).
xirc2ps_cs= [NET,PCMCIA]
Format:
@@ -5476,6 +7365,12 @@
controller on both pseries and powernv
platforms. Only useful on POWER9 and above.
+ xive.store-eoi=off [PPC]
+ By default on POWER10 and above, the kernel will use
+ stores for EOI handling when the XIVE interrupt mode
+ is active. This option allows the XIVE driver to use
+ loads instead, as on POWER9.
+
xhci-hcd.quirks [USB,KNL]
A hex value specifying bitmask with supplemental xhci
host controller quirks. Meaning of each bit can be
@@ -5499,3 +7394,4 @@
memory, and other data can't be written using
xmon commands.
off xmon is disabled.
+