Double-quotes can be used to protect spaces in values, e.g.:
param="spaces in here"
+cpu lists:
+----------
+
+Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
+nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
+
+ <cpu number>,...,<cpu number>
+
+or
+
+ <cpu number>-<cpu number>
+ (must be a positive range in ascending order)
+
+or a mixture
+
+<cpu number>,...,<cpu number>-<cpu number>
+
+Note that for the special case of a range one can split the range into equal
+sized groups and for each group use some amount from the beginning of that
+group:
+
+ <cpu number>-cpu number>:<used size>/<group size>
+
+For example one can add to the command line following parameter:
+
+ isolcpus=1,2,10-20,100-2000:2/25
+
+where the final item represents CPUs 100,101,125,126,150,151,...
+
+
+
This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
module. Loadable modules, after being loaded into the running kernel, also
More X86-64 boot options can be found in
Documentation/x86/x86_64/boot-options.txt .
X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
+ X86_UV SGI UV support is enabled.
XEN Xen support is enabled
In addition, the following text indicates that the option:
acpi= [HW,ACPI,X86,ARM64]
Advanced Configuration and Power Interface
- Format: { force | off | strict | noirq | rsdt |
+ 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]
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" or "acpi=force" are available
+ For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
+ are available
See also Documentation/power/runtime_pm.txt, pci=noacpi
acpi_osi=!* # remove all strings
acpi_osi=! # disable all built-in OS vendor
strings
+ acpi_osi=!! # enable all built-in OS vendor
+ strings
acpi_osi= # disable all strings
'acpi_osi=!' can be used in combination with single or
driver will print ACPI tables for AMD IOMMU during
IOMMU initialization.
+ amd_iommu_intr= [HW,X86-64]
+ Specifies one of the following AMD IOMMU interrupt
+ remapping modes:
+ legacy - Use legacy interrupt remapping mode.
+ vapic - Use virtual APIC mode, which allows IOMMU
+ to inject interrupts directly into guest.
+ This mode requires kvm-amd.avic=1.
+ (Default when IOMMU HW support is present.)
+
amijoy.map= [HW,JOY] Amiga joystick support
Map of devices attached to JOY0DAT and JOY1DAT
Format: <a>,<b>
Format: <int> (must be >=0)
Default: 64
+ bau= [X86_UV] Enable the BAU on SGI UV. The default
+ behavior is to disable the BAU (i.e. bau=0).
+ Format: { "0" | "1" }
+ 0 - Disable the BAU.
+ 1 - Enable the BAU.
+ unset - Disable the BAU.
+
baycom_epp= [HW,AX25]
Format: <io>,<mode>
bootmem_debug [KNL] Enable bootmem allocator debug messages.
+ bert_disable [ACPI]
+ Disable BERT OS support on buggy BIOSes.
+
bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
bttv.radio= Most important insmod options are available as
kernel args too.
[SPARC64] tick
[X86-64] hpet,tsc
+ clocksource.arm_arch_timer.evtstrm=
+ [ARM,ARM64]
+ Format: <bool>
+ Enable/disable the eventstream feature of the ARM
+ architected timer so that code using WFE-based polling
+ loops can be debugged more effectively on production
+ systems.
+
+ clocksource.arm_arch_timer.fsl-a008585=
+ [ARM64]
+ Format: <bool>
+ Enable/disable the workaround of Freescale/NXP
+ erratum A-008585. This can be useful for KVM
+ guests, if the guest device tree doesn't show the
+ erratum. If unspecified, the workaround is
+ enabled based on the device tree.
+
clearcpuid=BITNUM [X86]
Disable CPUID feature X for the kernel. See
arch/x86/include/asm/cpufeatures.h for the valid bit
It will be ignored when crashkernel=X,high is not used
or memory reserved is below 4G.
+ cryptomgr.notests
+ [KNL] Disable crypto self-tests
+
cs89x0_dma= [HW,NET]
Format: <dma>
dhash_entries= [KNL]
Set number of hash buckets for dentry cache.
+ disable_1tb_segments [PPC]
+ Disables the use of 1TB hash page table segments. This
+ causes the kernel to fall back to 256MB segments which
+ can be useful when debugging issues that require an SLB
+ miss to occur.
+
disable= [IPV6]
See Documentation/networking/ipv6.txt.
+ disable_radix [PPC]
+ Disable RADIX MMU mode on POWER9
+
disable_cpu_apicid= [X86,APIC,SMP]
Format: <int>
The number of initial APIC ID for the
determined by the stdout-path property in device
tree's chosen node.
- cdns,<addr>
- Start an early, polled-mode console on a cadence serial
- port at the specified address. The cadence serial port
- must already be setup and configured. Options are not
- yet supported.
+ cdns,<addr>[,options]
+ Start an early, polled-mode console on a Cadence
+ (xuartps) serial port at the specified address. Only
+ supported option is baud rate. If baud rate is not
+ specified, the serial port must already be setup and
+ configured.
uart[8250],io,<addr>[,options]
uart[8250],mmio,<addr>[,options]
the driver will use only 32-bit accessors to read/write
the device registers.
+ meson,<addr>
+ Start an early, polled-mode console on a meson serial
+ port at the specified address. The serial port must
+ already be setup and configured. Options are not yet
+ supported.
+
msm_serial,<addr>
Start an early, polled-mode console on an msm serial
port at the specified address. The serial port
Address Range Mirroring feature even if your box
doesn't support it.
+ efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
+ that is to be dynamically loaded by Linux. If there are
+ multiple variables with the same name but with different
+ vendor GUIDs, all of them will be loaded. See
+ Documentation/acpi/ssdt-overlays.txt for details.
+
+
eisa_irq_edge= [PARISC,HW]
See header of drivers/parisc/eisa.c.
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>...
+
hardlockup_all_cpu_backtrace=
[KNL] Should the hard-lockup detector generate
backtraces on all cpus.
initrd= [BOOT] Specify the location of the initial ramdisk
+ 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.
+
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
Format: <irq>
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
0 disables intel_idle and fall back on acpi_idle.
- 1 to 6 specify maximum depth of C-state.
+ 1 to 9 specify maximum depth of C-state.
intel_pstate= [X86]
disable
hwp_only
Only load intel_pstate on systems which support
hardware P state control (HWP) if available.
+ support_acpi_ppc
+ Enforce ACPI _PPC performance limits. If the Fixed ACPI
+ Description Table, specifies preferred power management
+ profile as "Enterprise Server" or "Performance Server",
+ then this feature is turned on by default.
intremap= [X86-64, Intel-IOMMU]
on enable Interrupt Remapping (default)
See Documentation/filesystems/nfs/nfsroot.txt.
irqaffinity= [SMP] Set the default irq affinity mask
- Format:
- <cpu number>,...,<cpu number>
- or
- <cpu number>-<cpu number>
- (must be a positive range in ascending order)
- or a mixture
- <cpu number>,...,<cpu number>-<cpu number>
+ The argument is a cpu list, as described above.
irqfixup [HW]
When an interrupt is not handled search all handlers
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
- Format:
- <cpu number>,...,<cpu number>
- or
- <cpu number>-<cpu number>
- (must be a positive range in ascending order)
- or a mixture
- <cpu number>,...,<cpu number>-<cpu number>
+ The argument is a cpu list, as described above.
This option can be used to specify one or more CPUs
to isolate from the general SMP balancing and scheduling
PCI device 00:14.0 write the parameter as:
ivrs_hpet[0]=00:14.0
+ 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:
+ ivrs_acpihid[00:14.5]=AMD0020:0
+
js= [HW,JOY] Analog joystick
See Documentation/input/joystick.txt.
- kaslr/nokaslr [X86]
- Enable/disable kernel and module base offset ASLR
- (Address Space Layout Randomization) if built into
- the kernel. When CONFIG_HIBERNATION is selected,
- kASLR is disabled by default. When kASLR is enabled,
- hibernation will be disabled.
+ nokaslr [KNL]
+ When CONFIG_RANDOMIZE_BASE is set, this disables
+ kernel and module base offset ASLR (Address Space
+ Layout Randomization).
keepinitrd [HW,ARM]
than or equal to this physical address is ignored.
maxcpus= [SMP] Maximum number of processors that an SMP kernel
- should make use of. maxcpus=n : n >= 0 limits the
- kernel to using 'n' processors. n=0 is a special case,
- it is equivalent to "nosmp", which also disables
- the IO APIC.
+ will bring up during bootup. maxcpus=n : n >= 0 limits
+ the kernel to bring up 'n' processors. Surely after
+ bootup you can bring up the other plugged cpu by executing
+ "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
+ only takes effect during system bootup.
+ While n=0 is a special case, it is equivalent to "nosmp",
+ which also disables the IO APIC.
max_loop= [LOOP] The number of loop block devices that get
(loop.max_loop) unconditionally pre-created at init time. The default
[KNL,SH] Allow user to override the default size for
per-device physically contiguous DMA buffers.
+ memhp_default_state=online/offline
+ [KNL] Set the initial state for the memory hotplug
+ onlining policy. If not specified, the default value is
+ set according to the
+ CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
+ option.
+ See Documentation/memory-hotplug.txt.
+
memmap=exactmap [KNL,X86] Enable setting of an exact
E820 memory map, as specified by the user.
Such memmap=exactmap lines can be constructed based on
Note that if CONFIG_MODULE_SIG_FORCE is set, that
is always true, so this option does nothing.
+ module_blacklist= [KNL] Do not load a comma-separated list of
+ modules. Useful for debugging problem modules.
+
mousedev.tap_time=
[MOUSE] Maximum time between finger touching and
leaving touchpad surface for touch to be considered
nfsrootdebug [NFS] enable nfsroot debugging messages.
See Documentation/filesystems/nfs/nfsroot.txt.
+ nfs.callback_nr_threads=
+ [NFSv4] set the total number of threads that the
+ NFS client will assign to service NFSv4 callback
+ requests.
+
nfs.callback_tcpport=
[NFS] set the TCP port on which the NFSv4 callback
channel should listen.
of returning the full 64-bit number.
The default is to return 64-bit inode numbers.
+ nfs.max_session_cb_slots=
+ [NFSv4.1] Sets the maximum number of session
+ slots the client will assign to the callback
+ channel. This determines the maximum number of
+ callbacks the client will process in parallel for
+ a particular server.
+
nfs.max_session_slots=
[NFSv4.1] Sets the maximum number of session slots
the client will attempt to negotiate with the server.
nodelayacct [KNL] Disable per-task delay accounting
- nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
-
nodsp [SH] Disable hardware DSP at boot time.
noefi Disable EFI runtime services support.
nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
+ nosmt [KNL,S390] Disable symmetric multithreading (SMT).
+ Equivalent to smt=1.
+
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.
Default: on
nohz_full= [KNL,BOOT]
+ The argument is a cpu list, as described above.
In kernels built with CONFIG_NO_HZ_FULL=y, set
the specified list of CPUs whose tick will be stopped
whenever possible. The boot CPU will be forced outside
nr_cpus= [SMP] Maximum number of processors that an SMP kernel
could support. nr_cpus=n : n >= 1 limits the kernel to
- supporting 'n' processors. Later in runtime you can not
- use hotplug cpu feature to put more cpu back to online.
- just like you compile the kernel NR_CPUS=n
+ support 'n' processors. It could be larger than the
+ number of already plugged CPU during bootup, later in
+ runtime you can physically add extra cpu until it reaches
+ n. So during boot up some boot time memory for per-cpu
+ variables need be pre-allocated for later physical cpu
+ hot plugging.
nr_uarts= [SERIAL] maximum number of UARTs to be registered.
timer: [X86] Force use of architectural NMI
timer mode (see also oprofile.timer
for generic hr timer mode)
- [s390] Force legacy basic mode sampling
- (report cpu_type "timer")
oops=panic Always panic on oopses. Default is to just kill the
process, but there is a small probability of
for broken drivers that don't call it.
skip_isa_align [X86] do not align io start addr, so can
handle more pci cards
- firmware [ARM] Do not re-enumerate the bus but instead
- just use the configuration from the
- bootloader. This is currently used on
- IXP2000 systems where the bus has to be
- configured a certain way for adjunct CPUs.
noearly [X86] Don't do any early type 1 scanning.
This might help on some broken boards which
machine check when some devices' config space
resource_alignment=
Format:
[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
+ [<order of align>@]pci:<vendor>:<device>\
+ [:<subvendor>:<subdevice>][; ...]
Specifies alignment and device to reassign
aligned memory resources.
If <order of align> is not specified,
PAGE_SIZE is used as alignment.
PCI-PCI bridge can be specified, if resource
windows need to be expanded.
+ To specify the alignment for several
+ instances of a device, the PCI vendor,
+ device, subvendor, and subdevice may be
+ specified, e.g., 4096@pci:8086:9c22:103c:198f
ecrc= Enable/disable PCIe ECRC (transaction layer
end-to-end CRC checking).
bios: Use BIOS/firmware settings. This is the
hpmemsize=nn[KMG] The fixed amount of bus space which is
reserved for hotplug bridge's memory window.
Default size is 2 megabytes.
+ hpbussize=nn The minimum amount of additional bus numbers
+ reserved for buses below a hotplug bridge.
+ Default is 1.
realloc= Enable/disable reallocating PCI bridge resources
if allocations done by BIOS are too small to
accommodate resources required by all child
compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
ports driver.
+ pcie_port_pm= [PCIE] PCIe port power management handling:
+ off Disable power management of all PCIe ports
+ force Forcibly enable power management of all PCIe ports
+
pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
nomsi Do not use MSI for native PCIe PME signaling (this makes
all PCIe root ports use INTx for all services).
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
default: disabled
+ printk.devkmsg={on,off,ratelimit}
+ Control writing to /dev/kmsg.
+ on - unlimited logging to /dev/kmsg from userspace
+ off - logging to /dev/kmsg disabled
+ ratelimit - ratelimit the logging
+ Default: ratelimit
+
printk.time= Show timing data prefixed to each printk message line
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
See Documentation/blockdev/ramdisk.txt.
rcu_nocbs= [KNL]
+ The argument is a cpu list, as described above.
+
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
Lazy RCU callbacks are those which RCU can
prove do nothing more than free memory.
+ rcuperf.gp_exp= [KNL]
+ Measure performance of expedited synchronous
+ grace-period primitives.
+
+ rcuperf.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]
+ 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
+ the number of CPUs. For example, -2 selects N
+ (the number of CPUs), -3 selects N+1, and so on.
+ A value of "n" less than or equal to -N selects
+ a single reader.
+
+ rcuperf.nwriters= [KNL]
+ Set number of RCU writers. The values operate
+ the same as for rcuperf.nreaders.
+ N, where N is the number of CPUs
+
+ rcuperf.perf_runnable= [BOOT]
+ Start rcuperf running at boot time.
+
+ rcuperf.shutdown= [KNL]
+ Shut the system down after performance tests
+ complete. This is useful for hands-off automated
+ testing.
+
+ rcuperf.perf_type= [KNL]
+ Specify the RCU implementation to test.
+
+ rcuperf.verbose= [KNL]
+ Enable additional printk() statements.
+
rcutorture.cbflood_inter_holdoff= [KNL]
Set holdoff time (jiffies) between successive
callback-flood tests.
relax_domain_level=
[KNL, SMP] Set scheduler's default relax_domain_level.
- See Documentation/cgroups/cpusets.txt.
+ See Documentation/cgroup-v1/cpusets.txt.
relative_sleep_states=
[SUSPEND] Use sleep state labeling where the deepest
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
1: Fast pin select (default)
2: ATC IRMode
+ smt [KNL,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.
+ Format: <integer>
+ Default: -1 (no limit)
+
softlockup_panic=
[KNL] Should the soft-lockup detector generate panics.
Format: <integer>
using these two parameters to set the minimum and
maximum port values.
+ sunrpc.svc_rpc_per_connection_limit=
+ [NFS,SUNRPC]
+ Limit the number of requests that the server will
+ process in parallel from a single connection.
+ The default value is 0 (no limit).
+
sunrpc.pool_mode=
[NFS]
Control how the NFS server code allocates CPUs to
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/cgroups/memory.txt)
+ it if 0 is given (See Documentation/cgroup-v1/memory.txt)
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Format: { <int> | force }
trace_event=[event-list]
[FTRACE] Set and start specified trace events in order
- to facilitate early boot debugging.
- See also Documentation/trace/events.txt
+ to facilitate early boot debugging. The event-list is a
+ comma separated list of trace events to enable. See
+ also Documentation/trace/events.txt
trace_options=[option-list]
[FTRACE] Enable or disable tracer options at boot.
u = IGNORE_UAS (don't bind to the uas driver);
w = NO_WP_DETECT (don't test whether the
medium is write-protected).
+ y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
+ even if the device claims no cache)
Example: quirks=0419:aaf5:rl,0421:0433:rc
user_debug= [KNL,ARM]
projects / cascardo / linux.git / blobdiff