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a205982598
The previous commit added macro calls in the entry code which mitigate the
Spectre v1 swapgs issue if the X86_FEATURE_FENCE_SWAPGS_* features are
enabled. Enable those features where applicable.
The mitigations may be disabled with "nospectre_v1" or "mitigations=off".
There are different features which can affect the risk of attack:
- When FSGSBASE is enabled, unprivileged users are able to place any
value in GS, using the wrgsbase instruction. This means they can
write a GS value which points to any value in kernel space, which can
be useful with the following gadget in an interrupt/exception/NMI
handler:
if (coming from user space)
swapgs
mov %gs:<percpu_offset>, %reg1
// dependent load or store based on the value of %reg
// for example: mov %(reg1), %reg2
If an interrupt is coming from user space, and the entry code
speculatively skips the swapgs (due to user branch mistraining), it
may speculatively execute the GS-based load and a subsequent dependent
load or store, exposing the kernel data to an L1 side channel leak.
Note that, on Intel, a similar attack exists in the above gadget when
coming from kernel space, if the swapgs gets speculatively executed to
switch back to the user GS. On AMD, this variant isn't possible
because swapgs is serializing with respect to future GS-based
accesses.
NOTE: The FSGSBASE patch set hasn't been merged yet, so the above case
doesn't exist quite yet.
- When FSGSBASE is disabled, the issue is mitigated somewhat because
unprivileged users must use prctl(ARCH_SET_GS) to set GS, which
restricts GS values to user space addresses only. That means the
gadget would need an additional step, since the target kernel address
needs to be read from user space first. Something like:
if (coming from user space)
swapgs
mov %gs:<percpu_offset>, %reg1
mov (%reg1), %reg2
// dependent load or store based on the value of %reg2
// for example: mov %(reg2), %reg3
It's difficult to audit for this gadget in all the handlers, so while
there are no known instances of it, it's entirely possible that it
exists somewhere (or could be introduced in the future). Without
tooling to analyze all such code paths, consider it vulnerable.
Effects of SMAP on the !FSGSBASE case:
- If SMAP is enabled, and the CPU reports RDCL_NO (i.e., not
susceptible to Meltdown), the kernel is prevented from speculatively
reading user space memory, even L1 cached values. This effectively
disables the !FSGSBASE attack vector.
- If SMAP is enabled, but the CPU *is* susceptible to Meltdown, SMAP
still prevents the kernel from speculatively reading user space
memory. But it does *not* prevent the kernel from reading the
user value from L1, if it has already been cached. This is probably
only a small hurdle for an attacker to overcome.
Thanks to Dave Hansen for contributing the speculative_smap() function.
Thanks to Andrew Cooper for providing the inside scoop on whether swapgs
is serializing on AMD.
[ tglx: Fixed the USER fence decision and polished the comment as suggested
by Dave Hansen ]
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
5284 lines
185 KiB
Plaintext
5284 lines
185 KiB
Plaintext
acpi= [HW,ACPI,X86,ARM64]
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Advanced Configuration and Power Interface
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Format: { force | on | off | strict | noirq | rsdt |
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copy_dsdt }
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force -- enable ACPI if default was off
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on -- enable ACPI but allow fallback to DT [arm64]
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off -- disable ACPI if default was on
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noirq -- do not use ACPI for IRQ routing
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strict -- Be less tolerant of platforms that are not
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strictly ACPI specification compliant.
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rsdt -- prefer RSDT over (default) XSDT
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copy_dsdt -- copy DSDT to memory
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For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
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are available
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See also Documentation/power/runtime_pm.txt, pci=noacpi
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acpi_apic_instance= [ACPI, IOAPIC]
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Format: <int>
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2: use 2nd APIC table, if available
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1,0: use 1st APIC table
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default: 0
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acpi_backlight= [HW,ACPI]
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acpi_backlight=vendor
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acpi_backlight=video
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If set to vendor, prefer vendor specific driver
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(e.g. thinkpad_acpi, sony_acpi, etc.) instead
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of the ACPI video.ko driver.
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acpi_force_32bit_fadt_addr
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force FADT to use 32 bit addresses rather than the
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64 bit X_* addresses. Some firmware have broken 64
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bit addresses for force ACPI ignore these and use
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the older legacy 32 bit addresses.
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acpica_no_return_repair [HW, ACPI]
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Disable AML predefined validation mechanism
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This mechanism can repair the evaluation result to make
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the return objects more ACPI specification compliant.
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This option is useful for developers to identify the
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root cause of an AML interpreter issue when the issue
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has something to do with the repair mechanism.
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acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
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acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
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Format: <int>
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CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
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debug output. Bits in debug_layer correspond to a
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_COMPONENT in an ACPI source file, e.g.,
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#define _COMPONENT ACPI_PCI_COMPONENT
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Bits in debug_level correspond to a level in
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ACPI_DEBUG_PRINT statements, e.g.,
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ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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The debug_level mask defaults to "info". See
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Documentation/acpi/debug.txt for more information about
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debug layers and levels.
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Enable processor driver info messages:
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acpi.debug_layer=0x20000000
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Enable PCI/PCI interrupt routing info messages:
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acpi.debug_layer=0x400000
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Enable AML "Debug" output, i.e., stores to the Debug
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object while interpreting AML:
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acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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Enable all messages related to ACPI hardware:
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acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
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Some values produce so much output that the system is
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unusable. The "log_buf_len" parameter may be useful
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if you need to capture more output.
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acpi_enforce_resources= [ACPI]
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{ strict | lax | no }
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Check for resource conflicts between native drivers
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and ACPI OperationRegions (SystemIO and SystemMemory
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only). IO ports and memory declared in ACPI might be
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used by the ACPI subsystem in arbitrary AML code and
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can interfere with legacy drivers.
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strict (default): access to resources claimed by ACPI
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is denied; legacy drivers trying to access reserved
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resources will fail to bind to device using them.
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lax: access to resources claimed by ACPI is allowed;
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legacy drivers trying to access reserved resources
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will bind successfully but a warning message is logged.
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no: ACPI OperationRegions are not marked as reserved,
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no further checks are performed.
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acpi_force_table_verification [HW,ACPI]
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Enable table checksum verification during early stage.
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By default, this is disabled due to x86 early mapping
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size limitation.
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acpi_irq_balance [HW,ACPI]
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ACPI will balance active IRQs
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default in APIC mode
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acpi_irq_nobalance [HW,ACPI]
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ACPI will not move active IRQs (default)
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default in PIC mode
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acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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Format: <irq>,<irq>...
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acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
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use by PCI
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Format: <irq>,<irq>...
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acpi_mask_gpe= [HW,ACPI]
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Due to the existence of _Lxx/_Exx, some GPEs triggered
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by unsupported hardware/firmware features can result in
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GPE floodings that cannot be automatically disabled by
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the GPE dispatcher.
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This facility can be used to prevent such uncontrolled
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GPE floodings.
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Format: <int>
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acpi_no_auto_serialize [HW,ACPI]
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Disable auto-serialization of AML methods
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AML control methods that contain the opcodes to create
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named objects will be marked as "Serialized" by the
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auto-serialization feature.
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This feature is enabled by default.
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This option allows to turn off the feature.
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acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
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kernels.
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acpi_no_static_ssdt [HW,ACPI]
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Disable installation of static SSDTs at early boot time
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By default, SSDTs contained in the RSDT/XSDT will be
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installed automatically and they will appear under
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/sys/firmware/acpi/tables.
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This option turns off this feature.
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Note that specifying this option does not affect
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dynamic table installation which will install SSDT
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tables to /sys/firmware/acpi/tables/dynamic.
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acpi_rsdp= [ACPI,EFI,KEXEC]
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Pass the RSDP address to the kernel, mostly used
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on machines running EFI runtime service to boot the
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second kernel for kdump.
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acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
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Format: To spoof as Windows 98: ="Microsoft Windows"
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acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
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of 2 which is mandated by ACPI 6) as the supported ACPI
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specification revision (when using this switch, it may
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be necessary to carry out a cold reboot _twice_ in a
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row to make it take effect on the platform firmware).
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acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
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acpi_osi="string1" # add string1
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acpi_osi="!string2" # remove string2
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acpi_osi=!* # remove all strings
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acpi_osi=! # disable all built-in OS vendor
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strings
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acpi_osi=!! # enable all built-in OS vendor
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strings
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acpi_osi= # disable all strings
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'acpi_osi=!' can be used in combination with single or
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multiple 'acpi_osi="string1"' to support specific OS
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vendor string(s). Note that such command can only
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affect the default state of the OS vendor strings, thus
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it cannot affect the default state of the feature group
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strings and the current state of the OS vendor strings,
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specifying it multiple times through kernel command line
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is meaningless. This command is useful when one do not
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care about the state of the feature group strings which
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should be controlled by the OSPM.
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Examples:
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1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
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to 'acpi_osi="Windows 2000" acpi_osi=!', they all
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can make '_OSI("Windows 2000")' TRUE.
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'acpi_osi=' cannot be used in combination with other
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'acpi_osi=' command lines, the _OSI method will not
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exist in the ACPI namespace. NOTE that such command can
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only affect the _OSI support state, thus specifying it
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multiple times through kernel command line is also
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meaningless.
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Examples:
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1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
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FALSE.
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'acpi_osi=!*' can be used in combination with single or
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multiple 'acpi_osi="string1"' to support specific
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string(s). Note that such command can affect the
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current state of both the OS vendor strings and the
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feature group strings, thus specifying it multiple times
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through kernel command line is meaningful. But it may
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still not able to affect the final state of a string if
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there are quirks related to this string. This command
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is useful when one want to control the state of the
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feature group strings to debug BIOS issues related to
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the OSPM features.
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Examples:
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1. 'acpi_osi="Module Device" acpi_osi=!*' can make
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'_OSI("Module Device")' FALSE.
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2. 'acpi_osi=!* acpi_osi="Module Device"' can make
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'_OSI("Module Device")' TRUE.
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3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
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equivalent to
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'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
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and
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'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
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they all will make '_OSI("Windows 2000")' TRUE.
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acpi_pm_good [X86]
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Override the pmtimer bug detection: force the kernel
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to assume that this machine's pmtimer latches its value
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and always returns good values.
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acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
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Format: { level | edge | high | low }
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acpi_skip_timer_override [HW,ACPI]
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Recognize and ignore IRQ0/pin2 Interrupt Override.
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For broken nForce2 BIOS resulting in XT-PIC timer.
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acpi_sleep= [HW,ACPI] Sleep options
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Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
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old_ordering, nonvs, sci_force_enable, nobl }
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See Documentation/power/video.txt for information on
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s3_bios and s3_mode.
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s3_beep is for debugging; it makes the PC's speaker beep
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as soon as the kernel's real-mode entry point is called.
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s4_nohwsig prevents ACPI hardware signature from being
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used during resume from hibernation.
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old_ordering causes the ACPI 1.0 ordering of the _PTS
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control method, with respect to putting devices into
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low power states, to be enforced (the ACPI 2.0 ordering
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of _PTS is used by default).
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nonvs prevents the kernel from saving/restoring the
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ACPI NVS memory during suspend/hibernation and resume.
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sci_force_enable causes the kernel to set SCI_EN directly
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on resume from S1/S3 (which is against the ACPI spec,
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but some broken systems don't work without it).
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nobl causes the internal blacklist of systems known to
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behave incorrectly in some ways with respect to system
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suspend and resume to be ignored (use wisely).
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acpi_use_timer_override [HW,ACPI]
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Use timer override. For some broken Nvidia NF5 boards
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that require a timer override, but don't have HPET
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add_efi_memmap [EFI; X86] Include EFI memory map in
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kernel's map of available physical RAM.
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agp= [AGP]
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{ off | try_unsupported }
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off: disable AGP support
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try_unsupported: try to drive unsupported chipsets
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(may crash computer or cause data corruption)
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ALSA [HW,ALSA]
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See Documentation/sound/alsa-configuration.rst
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alignment= [KNL,ARM]
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Allow the default userspace alignment fault handler
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behaviour to be specified. Bit 0 enables warnings,
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bit 1 enables fixups, and bit 2 sends a segfault.
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align_va_addr= [X86-64]
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Align virtual addresses by clearing slice [14:12] when
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allocating a VMA at process creation time. This option
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gives you up to 3% performance improvement on AMD F15h
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machines (where it is enabled by default) for a
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CPU-intensive style benchmark, and it can vary highly in
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a microbenchmark depending on workload and compiler.
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32: only for 32-bit processes
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64: only for 64-bit processes
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on: enable for both 32- and 64-bit processes
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off: disable for both 32- and 64-bit processes
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alloc_snapshot [FTRACE]
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Allocate the ftrace snapshot buffer on boot up when the
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main buffer is allocated. This is handy if debugging
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and you need to use tracing_snapshot() on boot up, and
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do not want to use tracing_snapshot_alloc() as it needs
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to be done where GFP_KERNEL allocations are allowed.
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amd_iommu= [HW,X86-64]
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Pass parameters to the AMD IOMMU driver in the system.
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Possible values are:
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fullflush - enable flushing of IO/TLB entries when
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they are unmapped. Otherwise they are
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flushed before they will be reused, which
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is a lot of faster
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off - do not initialize any AMD IOMMU found in
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the system
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force_isolation - Force device isolation for all
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devices. The IOMMU driver is not
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allowed anymore to lift isolation
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requirements as needed. This option
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does not override iommu=pt
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amd_iommu_dump= [HW,X86-64]
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Enable AMD IOMMU driver option to dump the ACPI table
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for AMD IOMMU. With this option enabled, AMD IOMMU
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driver will print ACPI tables for AMD IOMMU during
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IOMMU initialization.
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amd_iommu_intr= [HW,X86-64]
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Specifies one of the following AMD IOMMU interrupt
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remapping modes:
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legacy - Use legacy interrupt remapping mode.
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vapic - Use virtual APIC mode, which allows IOMMU
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to inject interrupts directly into guest.
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This mode requires kvm-amd.avic=1.
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(Default when IOMMU HW support is present.)
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amijoy.map= [HW,JOY] Amiga joystick support
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Map of devices attached to JOY0DAT and JOY1DAT
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Format: <a>,<b>
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See also Documentation/input/joydev/joystick.rst
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analog.map= [HW,JOY] Analog joystick and gamepad support
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Specifies type or capabilities of an analog joystick
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connected to one of 16 gameports
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Format: <type1>,<type2>,..<type16>
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apc= [HW,SPARC]
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Power management functions (SPARCstation-4/5 + deriv.)
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Format: noidle
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Disable APC CPU standby support. SPARCstation-Fox does
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not play well with APC CPU idle - disable it if you have
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APC and your system crashes randomly.
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apic= [APIC,X86] Advanced Programmable Interrupt Controller
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Change the output verbosity while booting
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Format: { quiet (default) | verbose | debug }
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Change the amount of debugging information output
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when initialising the APIC and IO-APIC components.
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For X86-32, this can also be used to specify an APIC
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driver name.
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Format: apic=driver_name
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Examples: apic=bigsmp
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apic_extnmi= [APIC,X86] External NMI delivery setting
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Format: { bsp (default) | all | none }
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bsp: External NMI is delivered only to CPU 0
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all: External NMIs are broadcast to all CPUs as a
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backup of CPU 0
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none: External NMI is masked for all CPUs. This is
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useful so that a dump capture kernel won't be
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shot down by NMI
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autoconf= [IPV6]
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See Documentation/networking/ipv6.txt.
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show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
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Limit apic dumping. The parameter defines the maximal
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number of local apics being dumped. Also it is possible
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to set it to "all" by meaning -- no limit here.
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Format: { 1 (default) | 2 | ... | all }.
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The parameter valid if only apic=debug or
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apic=verbose is specified.
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Example: apic=debug show_lapic=all
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apm= [APM] Advanced Power Management
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See header of arch/x86/kernel/apm_32.c.
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arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
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Format: <io>,<irq>,<nodeID>
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ataflop= [HW,M68k]
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atarimouse= [HW,MOUSE] Atari Mouse
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atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
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EzKey and similar keyboards
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atkbd.reset= [HW] Reset keyboard during initialization
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atkbd.set= [HW] Select keyboard code set
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Format: <int> (2 = AT (default), 3 = PS/2)
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atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
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keyboards
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atkbd.softraw= [HW] Choose between synthetic and real raw mode
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Format: <bool> (0 = real, 1 = synthetic (default))
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atkbd.softrepeat= [HW]
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Use software keyboard repeat
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audit= [KNL] Enable the audit sub-system
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Format: { "0" | "1" | "off" | "on" }
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0 | off - kernel audit is disabled and can not be
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enabled until the next reboot
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unset - kernel audit is initialized but disabled and
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will be fully enabled by the userspace auditd.
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1 | on - kernel audit is initialized and partially
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enabled, storing at most audit_backlog_limit
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messages in RAM until it is fully enabled by the
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userspace auditd.
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Default: unset
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audit_backlog_limit= [KNL] Set the audit queue size limit.
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Format: <int> (must be >=0)
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Default: 64
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bau= [X86_UV] Enable the BAU on SGI UV. The default
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behavior is to disable the BAU (i.e. bau=0).
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Format: { "0" | "1" }
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0 - Disable the BAU.
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1 - Enable the BAU.
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unset - Disable the BAU.
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baycom_epp= [HW,AX25]
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Format: <io>,<mode>
|
|
|
|
baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
|
|
Format: <io>,<mode>
|
|
See header of drivers/net/hamradio/baycom_par.c.
|
|
|
|
baycom_ser_fdx= [HW,AX25]
|
|
BayCom Serial Port AX.25 Modem (Full Duplex Mode)
|
|
Format: <io>,<irq>,<mode>[,<baud>]
|
|
See header of drivers/net/hamradio/baycom_ser_fdx.c.
|
|
|
|
baycom_ser_hdx= [HW,AX25]
|
|
BayCom Serial Port AX.25 Modem (Half Duplex Mode)
|
|
Format: <io>,<irq>,<mode>
|
|
See header of drivers/net/hamradio/baycom_ser_hdx.c.
|
|
|
|
blkdevparts= Manual partition parsing of block device(s) for
|
|
embedded devices based on command line input.
|
|
See Documentation/block/cmdline-partition.txt
|
|
|
|
boot_delay= Milliseconds to delay each printk during boot.
|
|
Values larger than 10 seconds (10000) are changed to
|
|
no delay (0).
|
|
Format: integer
|
|
|
|
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.
|
|
bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
|
|
bttv.tuner=
|
|
|
|
bulk_remove=off [PPC] This parameter disables the use of the pSeries
|
|
firmware feature for flushing multiple hpte entries
|
|
at a time.
|
|
|
|
c101= [NET] Moxa C101 synchronous serial card
|
|
|
|
cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
|
|
Sometimes CPU hardware bugs make them report the cache
|
|
size incorrectly. The kernel will attempt work arounds
|
|
to fix known problems, but for some CPUs it is not
|
|
possible to determine what the correct size should be.
|
|
This option provides an override for these situations.
|
|
|
|
carrier_timeout=
|
|
[NET] Specifies amount of time (in seconds) that
|
|
the kernel should wait for a network carrier. By default
|
|
it waits 120 seconds.
|
|
|
|
ca_keys= [KEYS] This parameter identifies a specific key(s) on
|
|
the system trusted keyring to be used for certificate
|
|
trust validation.
|
|
format: { id:<keyid> | builtin }
|
|
|
|
cca= [MIPS] Override the kernel pages' cache coherency
|
|
algorithm. Accepted values range from 0 to 7
|
|
inclusive. See arch/mips/include/asm/pgtable-bits.h
|
|
for platform specific values (SB1, Loongson3 and
|
|
others).
|
|
|
|
ccw_timeout_log [S390]
|
|
See Documentation/s390/common_io.rst for details.
|
|
|
|
cgroup_disable= [KNL] Disable a particular controller
|
|
Format: {name of the controller(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
|
|
{Currently only "memory" controller deal with this and
|
|
cut the overhead, others just disable the usage. So
|
|
only cgroup_disable=memory is actually worthy}
|
|
|
|
cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
|
|
Format: { { controller | "all" | "named" }
|
|
[,{ controller | "all" | "named" }...] }
|
|
Like cgroup_disable, but only applies to cgroup v1;
|
|
the blacklisted controllers remain available in cgroup2.
|
|
"all" blacklists all controllers and "named" disables
|
|
named mounts. Specifying both "all" and "named" disables
|
|
all v1 hierarchies.
|
|
|
|
cgroup.memory= [KNL] Pass options to the cgroup memory controller.
|
|
Format: <string>
|
|
nosocket -- Disable socket memory accounting.
|
|
nokmem -- Disable kernel memory accounting.
|
|
|
|
checkreqprot [SELINUX] Set initial checkreqprot flag value.
|
|
Format: { "0" | "1" }
|
|
See security/selinux/Kconfig help text.
|
|
0 -- check protection applied by kernel (includes
|
|
any implied execute protection).
|
|
1 -- check protection requested by application.
|
|
Default value is set via a kernel config option.
|
|
Value can be changed at runtime via
|
|
/selinux/checkreqprot.
|
|
|
|
cio_ignore= [S390]
|
|
See Documentation/s390/common_io.rst for details.
|
|
clk_ignore_unused
|
|
[CLK]
|
|
Prevents the clock framework from automatically gating
|
|
clocks that have not been explicitly enabled by a Linux
|
|
device driver but are enabled in hardware at reset or
|
|
by the bootloader/firmware. Note that this does not
|
|
force such clocks to be always-on nor does it reserve
|
|
those clocks in any way. This parameter is useful for
|
|
debug and development, but should not be needed on a
|
|
platform with proper driver support. For more
|
|
information, see Documentation/driver-api/clk.rst.
|
|
|
|
clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
|
|
[Deprecated]
|
|
Forces specified clocksource (if available) to be used
|
|
when calculating gettimeofday(). If specified
|
|
clocksource is not available, it defaults to PIT.
|
|
Format: { pit | tsc | cyclone | pmtmr }
|
|
|
|
clocksource= Override the default clocksource
|
|
Format: <string>
|
|
Override the default clocksource and use the clocksource
|
|
with the name specified.
|
|
Some clocksource names to choose from, depending on
|
|
the platform:
|
|
[all] jiffies (this is the base, fallback clocksource)
|
|
[ACPI] acpi_pm
|
|
[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
|
|
pxa_timer,timer3,32k_counter,timer0_1
|
|
[X86-32] pit,hpet,tsc;
|
|
scx200_hrt on Geode; cyclone on IBM x440
|
|
[MIPS] MIPS
|
|
[PARISC] cr16
|
|
[S390] tod
|
|
[SH] SuperH
|
|
[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.
|
|
|
|
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.
|
|
|
|
cma=nn[MG]@[start[MG][-end[MG]]]
|
|
[ARM,X86,KNL]
|
|
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
|
|
|
|
cmo_free_hint= [PPC] Format: { yes | no }
|
|
Specify whether pages are marked as being inactive
|
|
when they are freed. This is used in CMO environments
|
|
to determine OS memory pressure for page stealing by
|
|
a hypervisor.
|
|
Default: yes
|
|
|
|
coherent_pool=nn[KMG] [ARM,KNL]
|
|
Sets the size of memory pool for coherent, atomic dma
|
|
allocations, by default set to 256K.
|
|
|
|
com20020= [HW,NET] ARCnet - COM20020 chipset
|
|
Format:
|
|
<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
|
|
|
|
com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
|
|
Format: <io>[,<irq>]
|
|
|
|
com90xx= [HW,NET]
|
|
ARCnet - COM90xx chipset (memory-mapped buffers)
|
|
Format: <io>[,<irq>[,<memstart>]]
|
|
|
|
condev= [HW,S390] console device
|
|
conmode=
|
|
|
|
console= [KNL] Output console device and options.
|
|
|
|
tty<n> Use the virtual console device <n>.
|
|
|
|
ttyS<n>[,options]
|
|
ttyUSB0[,options]
|
|
Use the specified serial port. The options are of
|
|
the form "bbbbpnf", where "bbbb" is the baud rate,
|
|
"p" is parity ("n", "o", or "e"), "n" is number of
|
|
bits, and "f" is flow control ("r" for RTS or
|
|
omit it). Default is "9600n8".
|
|
|
|
See Documentation/admin-guide/serial-console.rst for more
|
|
information. See
|
|
Documentation/networking/netconsole.txt for an
|
|
alternative.
|
|
|
|
uart[8250],io,<addr>[,options]
|
|
uart[8250],mmio,<addr>[,options]
|
|
uart[8250],mmio16,<addr>[,options]
|
|
uart[8250],mmio32,<addr>[,options]
|
|
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,
|
|
switching to the matching ttyS device later.
|
|
MMIO inter-register address stride is either 8-bit
|
|
(mmio), 16-bit (mmio16), or 32-bit (mmio32).
|
|
If none of [io|mmio|mmio16|mmio32], <addr> is assumed
|
|
to be equivalent to 'mmio'. 'options' are specified in
|
|
the same format described for ttyS above; if unspecified,
|
|
the h/w is not re-initialized.
|
|
|
|
hvc<n> Use the hypervisor console device <n>. This is for
|
|
both Xen and PowerPC hypervisors.
|
|
|
|
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
|
|
For now, only VisioBraille is supported.
|
|
|
|
console_msg_format=
|
|
[KNL] Change console messages format
|
|
default
|
|
By default we print messages on consoles in
|
|
"[time stamp] text\n" format (time stamp may not be
|
|
printed, depending on CONFIG_PRINTK_TIME or
|
|
`printk_time' param).
|
|
syslog
|
|
Switch to syslog format: "<%u>[time stamp] text\n"
|
|
IOW, each message will have a facility and loglevel
|
|
prefix. The format is similar to one used by syslog()
|
|
syscall, or to executing "dmesg -S --raw" or to reading
|
|
from /proc/kmsg.
|
|
|
|
consoleblank= [KNL] The console blank (screen saver) timeout in
|
|
seconds. A value of 0 disables the blank timer.
|
|
Defaults to 0.
|
|
|
|
coredump_filter=
|
|
[KNL] Change the default value for
|
|
/proc/<pid>/coredump_filter.
|
|
See also Documentation/filesystems/proc.txt.
|
|
|
|
coresight_cpu_debug.enable
|
|
[ARM,ARM64]
|
|
Format: <bool>
|
|
Enable/disable the CPU sampling based debugging.
|
|
0: default value, disable debugging
|
|
1: enable debugging at boot time
|
|
|
|
cpuidle.off=1 [CPU_IDLE]
|
|
disable the cpuidle sub-system
|
|
|
|
cpuidle.governor=
|
|
[CPU_IDLE] Name of the cpuidle governor to use.
|
|
|
|
cpufreq.off=1 [CPU_FREQ]
|
|
disable the cpufreq sub-system
|
|
|
|
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>]
|
|
|
|
crashkernel=size[KMG][@offset[KMG]]
|
|
[KNL] Using kexec, Linux can switch to a 'crash kernel'
|
|
upon panic. This parameter reserves the physical
|
|
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.
|
|
See Documentation/kdump/kdump.txt for further details.
|
|
|
|
crashkernel=range1:size1[,range2:size2,...][@offset]
|
|
[KNL] Same as above, but depends on the memory
|
|
in the running system. The syntax of range is
|
|
start-[end] where start and end are both
|
|
a memory unit (amount[KMG]). See also
|
|
Documentation/kdump/kdump.txt 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.
|
|
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
|
|
for second kernel instead.
|
|
0: to disable low allocation.
|
|
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>
|
|
|
|
cs89x0_media= [HW,NET]
|
|
Format: { rj45 | aui | bnc }
|
|
|
|
dasd= [HW,NET]
|
|
See header of drivers/s390/block/dasd_devmap.c.
|
|
|
|
db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
|
|
(one device per port)
|
|
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
|
|
[KNL] Enable printing [hashed] pointers early in the
|
|
boot sequence. If enabled, we use a weak hash instead
|
|
of siphash to hash pointers. Use this option if you are
|
|
seeing instances of '(___ptrval___)') and need to see a
|
|
value (hashed pointer) instead. Cryptographically
|
|
insecure, please do not use on production kernels.
|
|
|
|
debug_locks_verbose=
|
|
[KNL] verbose self-tests
|
|
Format=<0|1>
|
|
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.
|
|
|
|
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
|
|
be intentionally kept free (and hence protected) by the
|
|
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.
|
|
|
|
debug_pagealloc=
|
|
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
|
|
parameter enables the feature at boot time. In
|
|
default, it is disabled. We can avoid allocating huge
|
|
chunk of memory for debug pagealloc if we don't enable
|
|
it at boot time and the system will work mostly same
|
|
with the kernel built without CONFIG_DEBUG_PAGEALLOC.
|
|
on: enable the feature
|
|
|
|
debugpat [X86] Enable PAT debugging
|
|
|
|
decnet.addr= [HW,NET]
|
|
Format: <area>[,<node>]
|
|
See also Documentation/networking/decnet.txt.
|
|
|
|
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.
|
|
|
|
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
|
|
dump out devices still on the deferred probe list after
|
|
retrying.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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
|
|
corresponding CPU to be disabled at boot,
|
|
mostly used for the kdump 2nd kernel to
|
|
disable BSP to wake up multiple CPUs without
|
|
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
|
|
to workaround buggy firmware.
|
|
|
|
disable_ipv6= [IPV6]
|
|
See Documentation/networking/ipv6.txt.
|
|
|
|
disable_mtrr_cleanup [X86]
|
|
The kernel tries to adjust MTRR layout from continuous
|
|
to discrete, to make X server driver able to add WB
|
|
entry later. This parameter disables that.
|
|
|
|
disable_mtrr_trim [X86, Intel and AMD only]
|
|
By default the kernel will trim any uncacheable
|
|
memory out of your available memory pool based on
|
|
MTRR settings. This parameter disables that behavior,
|
|
possibly causing your machine to run very slowly.
|
|
|
|
disable_timer_pin_1 [X86]
|
|
Disable PIN 1 of APIC timer
|
|
Can be useful to work around chipset bugs.
|
|
|
|
dis_ucode_ldr [X86] Disable the microcode loader.
|
|
|
|
dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
|
|
this option disables the debugging code at boot.
|
|
|
|
dma_debug_entries=<number>
|
|
This option allows to tune the number of preallocated
|
|
entries for DMA-API debugging code. One entry is
|
|
required per DMA-API allocation. Use this if the
|
|
DMA-API debugging code disables itself because the
|
|
architectural default is too low.
|
|
|
|
dma_debug_driver=<driver_name>
|
|
With this option the DMA-API debugging driver
|
|
filter feature can be enabled at boot time. Just
|
|
pass the driver to filter for as the parameter.
|
|
The filter can be disabled or changed to another
|
|
driver later using sysfs.
|
|
|
|
driver_async_probe= [KNL]
|
|
List of driver names to be probed asynchronously.
|
|
Format: <driver_name1>,<driver_name2>...
|
|
|
|
drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
|
|
Broken monitors, graphic adapters, KVMs and EDIDless
|
|
panels may send no or incorrect EDID data sets.
|
|
This parameter allows to specify an EDID data sets
|
|
in the /lib/firmware directory that are used instead.
|
|
Generic built-in EDID data sets are used, if one of
|
|
edid/1024x768.bin, edid/1280x1024.bin,
|
|
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/EDID/HOWTO.txt. 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
|
|
set by separating the files with a comma. An EDID
|
|
data set with no connector name will be used for
|
|
any connectors not explicitly specified.
|
|
|
|
dscc4.setup= [NET]
|
|
|
|
dt_cpu_ftrs= [PPC]
|
|
Format: {"off" | "known"}
|
|
Control how the dt_cpu_ftrs device-tree binding is
|
|
used for CPU feature discovery and setup (if it
|
|
exists).
|
|
off: Do not use it, fall back to legacy cpu table.
|
|
known: Do not pass through unknown features to guests
|
|
or userspace, only those that the kernel is aware of.
|
|
|
|
dump_apple_properties [X86]
|
|
Dump name and content of EFI device properties on
|
|
x86 Macs. Useful for driver authors to determine
|
|
what data is available or for reverse-engineering.
|
|
|
|
dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
|
|
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.txt 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
|
|
which are not unmapped.
|
|
|
|
earlycon= [KNL] Output early console device and options.
|
|
|
|
[ARM64] The early console is determined by the
|
|
stdout-path property in device tree's chosen node,
|
|
or determined by the ACPI SPCR table.
|
|
|
|
[X86] When used with no options the early console is
|
|
determined by the ACPI SPCR table.
|
|
|
|
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]
|
|
uart[8250],mmio32,<addr>[,options]
|
|
uart[8250],mmio32be,<addr>[,options]
|
|
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.
|
|
MMIO inter-register address stride is either 8-bit
|
|
(mmio) or 32-bit (mmio32 or mmio32be).
|
|
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.
|
|
|
|
pl011,<addr>
|
|
pl011,mmio32,<addr>
|
|
Start an early, polled-mode console on a pl011 serial
|
|
port at the specified address. The pl011 serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported. If 'mmio32' is specified, then only
|
|
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
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
msm_serial_dm,<addr>
|
|
Start an early, polled-mode console on an msm serial
|
|
dm port at the specified address. The serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
owl,<addr>
|
|
Start an early, polled-mode console on a serial port
|
|
of an Actions Semi SoC, such as S500 or S900, at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
rda,<addr>
|
|
Start an early, polled-mode console on a serial port
|
|
of an RDA Micro SoC, such as RDA8810PL, at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
smh Use ARM semihosting calls for early console.
|
|
|
|
s3c2410,<addr>
|
|
s3c2412,<addr>
|
|
s3c2440,<addr>
|
|
s3c6400,<addr>
|
|
s5pv210,<addr>
|
|
exynos4210,<addr>
|
|
Use early console provided by serial driver available
|
|
on Samsung SoCs, requires selecting proper type and
|
|
a correct base address of the selected UART port. The
|
|
serial port must already be setup and configured.
|
|
Options are not yet supported.
|
|
|
|
lantiq,<addr>
|
|
Start an early, polled-mode console on a lantiq serial
|
|
(lqasc) port at the specified address. The serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
lpuart,<addr>
|
|
lpuart32,<addr>
|
|
Use early console provided by Freescale LP UART driver
|
|
found on Freescale Vybrid and QorIQ LS1021A processors.
|
|
A valid base address must be provided, and the serial
|
|
port must already be setup and configured.
|
|
|
|
ar3700_uart,<addr>
|
|
Start an early, polled-mode console on the
|
|
Armada 3700 serial port at the specified
|
|
address. The serial port must already be setup
|
|
and configured. Options are not yet supported.
|
|
|
|
qcom_geni,<addr>
|
|
Start an early, polled-mode console on a Qualcomm
|
|
Generic Interface (GENI) based serial port at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
efifb,[options]
|
|
Start an early, unaccelerated console on the EFI
|
|
memory mapped framebuffer (if available). On cache
|
|
coherent non-x86 systems that use system memory for
|
|
the framebuffer, pass the 'ram' option so that it is
|
|
mapped with the correct attributes.
|
|
|
|
earlyprintk= [X86,SH,ARM,M68k,S390]
|
|
earlyprintk=vga
|
|
earlyprintk=sclp
|
|
earlyprintk=xen
|
|
earlyprintk=serial[,ttySn[,baudrate]]
|
|
earlyprintk=serial[,0x...[,baudrate]]
|
|
earlyprintk=ttySn[,baudrate]
|
|
earlyprintk=dbgp[debugController#]
|
|
earlyprintk=pciserial[,force],bus:device.function[,baudrate]
|
|
earlyprintk=xdbc[xhciController#]
|
|
|
|
earlyprintk is useful when the kernel crashes before
|
|
the normal console is initialized. It is not enabled by
|
|
default because it has some cosmetic problems.
|
|
|
|
Append ",keep" to not disable it when the real console
|
|
takes over.
|
|
|
|
Only one of vga, efi, serial, or usb debug port can
|
|
be used at a time.
|
|
|
|
Currently only ttyS0 and ttyS1 may be specified by
|
|
name. Other I/O ports may be explicitly specified
|
|
on some architectures (x86 and arm at least) by
|
|
replacing ttySn with an I/O port address, like this:
|
|
earlyprintk=serial,0x1008,115200
|
|
You can find the port for a given device in
|
|
/proc/tty/driver/serial:
|
|
2: uart:ST16650V2 port:00001008 irq:18 ...
|
|
|
|
Interaction with the standard serial driver is not
|
|
very good.
|
|
|
|
The VGA and EFI output is eventually overwritten by
|
|
the real console.
|
|
|
|
The xen output can only be used by Xen PV guests.
|
|
|
|
The sclp output can only be used on s390.
|
|
|
|
The optional "force" to "pciserial" enables use of a
|
|
PCI device even when its classcode is not of the
|
|
UART class.
|
|
|
|
edac_report= [HW,EDAC] Control how to report EDAC event
|
|
Format: {"on" | "off" | "force"}
|
|
on: enable EDAC to report H/W event. May be overridden
|
|
by other higher priority error reporting module.
|
|
off: disable H/W event reporting through EDAC.
|
|
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" }
|
|
old_map [X86-64]: switch to the old ioremap-based EFI
|
|
runtime services mapping. 32-bit still uses this one by
|
|
default.
|
|
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
|
|
|
|
efi_no_storage_paranoia [EFI; X86]
|
|
Using this parameter you can use more than 50% of
|
|
your efi variable storage. Use this parameter only if
|
|
you are really sure that your UEFI does sane gc and
|
|
fulfills the spec otherwise your board may brick.
|
|
|
|
efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
|
|
Add arbitrary attribute to specific memory range by
|
|
updating original EFI memory map.
|
|
Region of memory which aa attribute is added to is
|
|
from ss to ss+nn.
|
|
If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
|
|
is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
|
|
attribute is added to range 0x100000000-0x180000000 and
|
|
0x10a0000000-0x1120000000.
|
|
|
|
Using this parameter you can do debugging of EFI memmap
|
|
related feature. For example, you can do debugging of
|
|
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.
|
|
|
|
elanfreq= [X86-32]
|
|
See comment before function elanfreq_setup() in
|
|
arch/x86/kernel/cpu/cpufreq/elanfreq.c.
|
|
|
|
elevator= [IOSCHED]
|
|
Format: { "mq-deadline" | "kyber" | "bfq" }
|
|
See Documentation/block/deadline-iosched.txt,
|
|
Documentation/block/kyber-iosched.txt and
|
|
Documentation/block/bfq-iosched.txt for details.
|
|
|
|
elfcorehdr=[size[KMG]@]offset[KMG] [IA64,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.
|
|
See Documentation/kdump/kdump.txt for details.
|
|
|
|
enable_mtrr_cleanup [X86]
|
|
The kernel tries to adjust MTRR layout from continuous
|
|
to discrete, to make X server driver able to add WB
|
|
entry later. This parameter enables that.
|
|
|
|
enable_timer_pin_1 [X86]
|
|
Enable PIN 1 of APIC timer
|
|
Can be useful to work around chipset bugs
|
|
(in particular on some ATI chipsets).
|
|
The kernel tries to set a reasonable default.
|
|
|
|
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.
|
|
|
|
erst_disable [ACPI]
|
|
Disable Error Record Serialization Table (ERST)
|
|
support.
|
|
|
|
ether= [HW,NET] Ethernet cards parameters
|
|
This option is obsoleted by the "netdev=" option, which
|
|
has equivalent usage. See its documentation for details.
|
|
|
|
evm= [EVM]
|
|
Format: { "fix" }
|
|
Permit 'security.evm' to be updated regardless of
|
|
current integrity status.
|
|
|
|
failslab=
|
|
fail_page_alloc=
|
|
fail_make_request=[KNL]
|
|
General fault injection mechanism.
|
|
Format: <interval>,<probability>,<space>,<times>
|
|
See also Documentation/fault-injection/.
|
|
|
|
floppy= [HW]
|
|
See Documentation/blockdev/floppy.txt.
|
|
|
|
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
|
|
functionally usable PAE implementation.
|
|
Warning: use of this parameter will taint the kernel
|
|
and may cause unknown problems.
|
|
|
|
ftrace=[tracer]
|
|
[FTRACE] will set and start the specified tracer
|
|
as early as possible in order to facilitate early
|
|
boot debugging.
|
|
|
|
ftrace_dump_on_oops[=orig_cpu]
|
|
[FTRACE] will dump the trace buffers on oops.
|
|
If no parameter is passed, ftrace will dump
|
|
buffers of all CPUs, but if you pass orig_cpu, it will
|
|
dump only the buffer of the CPU that triggered the
|
|
oops.
|
|
|
|
ftrace_filter=[function-list]
|
|
[FTRACE] Limit the functions traced by the function
|
|
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.
|
|
|
|
ftrace_notrace=[function-list]
|
|
[FTRACE] Do not trace the functions specified in
|
|
function-list. This list can be changed at run time
|
|
by the set_ftrace_notrace file in the debugfs
|
|
tracing directory.
|
|
|
|
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
|
|
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
|
|
functions that can be changed at run time by the
|
|
set_graph_notrace file in the debugfs tracing directory.
|
|
|
|
ftrace_graph_max_depth=<uint>
|
|
[FTRACE] Used with the function graph tracer. This is
|
|
the max depth it will trace into a function. This value
|
|
can be changed at run time by the max_graph_depth file
|
|
in the tracefs tracing directory. default: 0 (no limit)
|
|
|
|
gamecon.map[2|3]=
|
|
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
|
|
support via parallel port (up to 5 devices per port)
|
|
Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
|
|
See also Documentation/input/devices/joystick-parport.rst
|
|
|
|
gamma= [HW,DRM]
|
|
|
|
gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
|
|
Format: off | on
|
|
default: on
|
|
|
|
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.
|
|
When zero, profiling data is discarded and associated
|
|
debugfs files are removed at module unload time.
|
|
|
|
goldfish [X86] Enable the goldfish android emulator platform.
|
|
Don't use this when you are not running on the
|
|
android emulator
|
|
|
|
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
|
|
GPT to be used instead.
|
|
|
|
grcan.enable0= [HW] Configuration of physical interface 0. Determines
|
|
the "Enable 0" bit of the configuration register.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.enable1= [HW] Configuration of physical interface 1. Determines
|
|
the "Enable 0" bit of the configuration register.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.select= [HW] Select which physical interface to use.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.txsize= [HW] Sets the size of the tx buffer.
|
|
Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
|
|
Default: 1024
|
|
grcan.rxsize= [HW] Sets the size of the rx buffer.
|
|
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.
|
|
Format: <integer>
|
|
|
|
hashdist= [KNL,NUMA] Large hashes allocated during boot
|
|
are distributed across NUMA nodes. Defaults on
|
|
for 64-bit NUMA, off otherwise.
|
|
Format: 0 | 1 (for off | on)
|
|
|
|
hcl= [IA-64] SGI's Hardware Graph compatibility layer
|
|
|
|
hd= [EIDE] (E)IDE hard drive subsystem geometry
|
|
Format: <cyl>,<head>,<sect>
|
|
|
|
hest_disable [ACPI]
|
|
Disable Hardware Error Source Table (HEST) support;
|
|
corresponding firmware-first mode error processing
|
|
logic will be disabled.
|
|
|
|
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
|
|
size on bigger boxes.
|
|
|
|
highres= [KNL] Enable/disable high resolution timer mode.
|
|
Valid parameters: "on", "off"
|
|
Default: "on"
|
|
|
|
hisax= [HW,ISDN]
|
|
See Documentation/isdn/README.HiSax.
|
|
|
|
hlt [BUGS=ARM,SH]
|
|
|
|
hpet= [X86-32,HPET] option to control HPET usage
|
|
Format: { enable (default) | disable | force |
|
|
verbose }
|
|
disable: disable HPET and use PIT instead
|
|
force: allow force enabled of undocumented chips (ICH4,
|
|
VIA, nVidia)
|
|
verbose: show contents of HPET registers during setup
|
|
|
|
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).
|
|
|
|
hung_task_panic=
|
|
[KNL] Should the hung task detector generate panics.
|
|
Format: <integer>
|
|
|
|
A nonzero value 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
|
|
be changed later by the kernel.hung_task_panic sysctl.
|
|
|
|
hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
|
|
terminal devices. Valid values: 0..8
|
|
hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
|
|
If specified, z/VM IUCV HVC accepts connections
|
|
from listed z/VM user IDs only.
|
|
|
|
hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
|
|
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.
|
|
Format:
|
|
<bus_id>,<clkrate>
|
|
|
|
i8042.debug [HW] Toggle i8042 debug mode
|
|
i8042.unmask_kbd_data
|
|
[HW] Enable printing of interrupt data from the KBD port
|
|
(disabled by default, and as a pre-condition
|
|
requires that i8042.debug=1 be enabled)
|
|
i8042.direct [HW] Put keyboard port into non-translated mode
|
|
i8042.dumbkbd [HW] Pretend that controller can only read data from
|
|
keyboard and cannot control its state
|
|
(Don't attempt to blink the leds)
|
|
i8042.noaux [HW] Don't check for auxiliary (== mouse) port
|
|
i8042.nokbd [HW] Don't check/create keyboard port
|
|
i8042.noloop [HW] Disable the AUX Loopback command while probing
|
|
for the AUX port
|
|
i8042.nomux [HW] Don't check presence of an active multiplexing
|
|
controller
|
|
i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
|
|
controllers
|
|
i8042.notimeout [HW] Ignore timeout condition signalled by controller
|
|
i8042.reset [HW] Reset the controller during init, cleanup and
|
|
suspend-to-ram transitions, only during s2r
|
|
transitions, or never reset
|
|
Format: { 1 | Y | y | 0 | N | n }
|
|
1, Y, y: always reset controller
|
|
0, N, n: don't ever reset controller
|
|
Default: only on s2r transitions on x86; most other
|
|
architectures force reset to be always executed
|
|
i8042.unlock [HW] Unlock (ignore) the keylock
|
|
i8042.kbdreset [HW] Reset device connected to KBD port
|
|
|
|
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
|
|
brightness value of 0 indicates backlight switched off,
|
|
and the maximum of the brightness value sets the backlight
|
|
to maximum brightness. If this parameter is set to 0
|
|
(default) and the machine requires it, or this parameter
|
|
is set to 1, a brightness value of 0 sets the backlight
|
|
to maximum brightness, and the maximum of the brightness
|
|
value switches the backlight off.
|
|
-1 -- never invert brightness
|
|
0 -- machine default
|
|
1 -- force brightness inversion
|
|
|
|
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.txt.
|
|
|
|
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
|
|
Poll forces a polling idle loop that can slightly
|
|
improve the performance of waking up a idle CPU, but
|
|
will use a lot of power and make the system run hot.
|
|
Not recommended.
|
|
idle=halt: Halt is forced to be used for CPU idle.
|
|
In such case C2/C3 won't be used again.
|
|
idle=nomwait: Disable mwait for CPU C-states
|
|
|
|
ieee754= [MIPS] Select IEEE Std 754 conformance mode
|
|
Format: { strict | legacy | 2008 | relaxed }
|
|
Default: strict
|
|
|
|
Choose which programs will be accepted for execution
|
|
based on the IEEE 754 NaN encoding(s) supported by
|
|
the FPU and the NaN encoding requested with the value
|
|
of an ELF file header flag individually set by each
|
|
binary. Hardware implementations are permitted to
|
|
support either or both of the legacy and the 2008 NaN
|
|
encoding mode.
|
|
|
|
Available settings are as follows:
|
|
strict accept binaries that request a NaN encoding
|
|
supported by the FPU
|
|
legacy only accept legacy-NaN binaries, if supported
|
|
by the FPU
|
|
2008 only accept 2008-NaN binaries, if supported
|
|
by the FPU
|
|
relaxed accept any binaries regardless of whether
|
|
supported by the FPU
|
|
|
|
The FPU emulator is always able to support both NaN
|
|
encodings, so if no FPU hardware is present or it has
|
|
been disabled with 'nofpu', then the settings of
|
|
'legacy' and '2008' strap the emulator accordingly,
|
|
'relaxed' straps the emulator for both legacy-NaN and
|
|
2008-NaN, whereas 'strict' enables legacy-NaN only on
|
|
legacy processors and both NaN encodings on MIPS32 or
|
|
MIPS64 CPUs.
|
|
|
|
The setting for ABS.fmt/NEG.fmt instruction execution
|
|
mode generally follows that for the NaN encoding,
|
|
except where unsupported by hardware.
|
|
|
|
ignore_loglevel [KNL]
|
|
Ignore loglevel setting - this will print /all/
|
|
kernel messages to the console. Useful for debugging.
|
|
We also add it as printk module parameter, so users
|
|
could change it dynamically, usually by
|
|
/sys/module/printk/parameters/ignore_loglevel.
|
|
|
|
ignore_rlimit_data
|
|
Ignore RLIMIT_DATA setting for data mappings,
|
|
print warning at first misuse. Can be changed via
|
|
/sys/module/kernel/parameters/ignore_rlimit_data.
|
|
|
|
ihash_entries= [KNL]
|
|
Set number of hash buckets for inode cache.
|
|
|
|
ima_appraise= [IMA] appraise integrity measurements
|
|
Format: { "off" | "enforce" | "fix" | "log" }
|
|
default: "enforce"
|
|
|
|
ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
|
|
The builtin appraise policy appraises all files
|
|
owned by uid=0.
|
|
|
|
ima_canonical_fmt [IMA]
|
|
Use the canonical format for the binary runtime
|
|
measurements, instead of host native format.
|
|
|
|
ima_hash= [IMA]
|
|
Format: { md5 | sha1 | rmd160 | sha256 | sha384
|
|
| sha512 | ... }
|
|
default: "sha1"
|
|
|
|
The list of supported hash algorithms is defined
|
|
in crypto/hash_info.h.
|
|
|
|
ima_policy= [IMA]
|
|
The builtin policies to load during IMA setup.
|
|
Format: "tcb | appraise_tcb | secure_boot |
|
|
fail_securely"
|
|
|
|
The "tcb" policy measures all programs exec'd, files
|
|
mmap'd for exec, and all files opened with the read
|
|
mode bit set by either the effective uid (euid=0) or
|
|
uid=0.
|
|
|
|
The "appraise_tcb" policy appraises the integrity of
|
|
all files owned by root.
|
|
|
|
The "secure_boot" policy appraises the integrity
|
|
of files (eg. kexec kernel image, kernel modules,
|
|
firmware, policy, etc) based on file signatures.
|
|
|
|
The "fail_securely" policy forces file signature
|
|
verification failure also on privileged mounted
|
|
filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
|
|
flag.
|
|
|
|
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
|
|
programs exec'd, files mmap'd for exec, and all files
|
|
opened for read by uid=0.
|
|
|
|
ima_template= [IMA]
|
|
Select one of defined IMA measurements template formats.
|
|
Formats: { "ima" | "ima-ng" | "ima-sig" }
|
|
Default: "ima-ng"
|
|
|
|
ima_template_fmt=
|
|
[IMA] Define a custom template format.
|
|
Format: { "field1|...|fieldN" }
|
|
|
|
ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
|
|
Format: <min_file_size>
|
|
Set the minimal file size for using asynchronous hash.
|
|
If left unspecified, ahash usage is disabled.
|
|
|
|
ahash performance varies for different data sizes on
|
|
different crypto accelerators. This option can be used
|
|
to achieve the best performance for a particular HW.
|
|
|
|
ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
|
|
Format: <bufsize>
|
|
Set hashing buffer size. Default: 4k.
|
|
|
|
ahash performance varies for different chunk sizes on
|
|
different crypto accelerators. This option can be used
|
|
to achieve best performance for particular HW.
|
|
|
|
init= [KNL]
|
|
Format: <full_path>
|
|
Run specified binary instead of /sbin/init as init
|
|
process.
|
|
|
|
initcall_debug [KNL] Trace initcalls as they are executed. Useful
|
|
for working out where the kernel is dying during
|
|
startup.
|
|
|
|
initcall_blacklist= [KNL] Do not execute a comma-separated list of
|
|
initcall functions. Useful for debugging built-in
|
|
modules and initcalls.
|
|
|
|
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>
|
|
|
|
int_pln_enable [x86] Enable power limit notification interrupt
|
|
|
|
integrity_audit=[IMA]
|
|
Format: { "0" | "1" }
|
|
0 -- basic integrity auditing messages. (Default)
|
|
1 -- additional integrity auditing messages.
|
|
|
|
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
|
|
on
|
|
Enable intel iommu driver.
|
|
off
|
|
Disable intel iommu driver.
|
|
igfx_off [Default Off]
|
|
By default, gfx is mapped as normal device. If a gfx
|
|
device has a dedicated DMAR unit, the DMAR unit is
|
|
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.
|
|
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.
|
|
tboot_noforce [Default Off]
|
|
Do not force the Intel IOMMU enabled under tboot.
|
|
By default, tboot will force Intel IOMMU on, which
|
|
could harm performance of some high-throughput
|
|
devices like 40GBit network cards, even if identity
|
|
mapping is enabled.
|
|
Note that using this option lowers the security
|
|
provided by tboot because it makes the system
|
|
vulnerable to DMA attacks.
|
|
|
|
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
|
|
0 disables intel_idle and fall back on acpi_idle.
|
|
1 to 9 specify maximum depth of C-state.
|
|
|
|
intel_pstate= [X86]
|
|
disable
|
|
Do not enable intel_pstate as the default
|
|
scaling driver for the supported processors
|
|
passive
|
|
Use intel_pstate as a scaling driver, but configure it
|
|
to work with generic cpufreq governors (instead of
|
|
enabling its internal governor). This mode cannot be
|
|
used along with the hardware-managed P-states (HWP)
|
|
feature.
|
|
force
|
|
Enable intel_pstate on systems that prohibit it by default
|
|
in favor of acpi-cpufreq. Forcing the intel_pstate driver
|
|
instead of acpi-cpufreq may disable platform features, such
|
|
as thermal controls and power capping, that rely on ACPI
|
|
P-States information being indicated to OSPM and therefore
|
|
should be used with caution. This option does not work with
|
|
processors that aren't supported by the intel_pstate driver
|
|
or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
|
|
no_hwp
|
|
Do not enable hardware P state control (HWP)
|
|
if available.
|
|
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.
|
|
per_cpu_perf_limits
|
|
Allow per-logical-CPU P-State performance control limits using
|
|
cpufreq sysfs interface
|
|
|
|
intremap= [X86-64, Intel-IOMMU]
|
|
on enable Interrupt Remapping (default)
|
|
off disable Interrupt Remapping
|
|
nosid disable Source ID checking
|
|
no_x2apic_optout
|
|
BIOS x2APIC opt-out request will be ignored
|
|
nopost disable Interrupt Posting
|
|
|
|
iomem= Disable strict checking of access to MMIO memory
|
|
strict regions from userspace.
|
|
relaxed
|
|
|
|
iommu= [x86]
|
|
off
|
|
force
|
|
noforce
|
|
biomerge
|
|
panic
|
|
nopanic
|
|
merge
|
|
nomerge
|
|
soft
|
|
pt [x86]
|
|
nopt [x86]
|
|
nobypass [PPC/POWERNV]
|
|
Disable IOMMU bypass, using IOMMU for PCI devices.
|
|
|
|
iommu.strict= [ARM64] Configure TLB invalidation behaviour
|
|
Format: { "0" | "1" }
|
|
0 - Lazy mode.
|
|
Request that DMA unmap operations use deferred
|
|
invalidation of hardware TLBs, for increased
|
|
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).
|
|
DMA unmap operations invalidate IOMMU hardware TLBs
|
|
synchronously.
|
|
|
|
iommu.passthrough=
|
|
[ARM64] Configure DMA to bypass the IOMMU by default.
|
|
Format: { "0" | "1" }
|
|
0 - Use IOMMU translation for DMA.
|
|
1 - Bypass the IOMMU for DMA.
|
|
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
|
|
|
|
io7= [HW] IO7 for Marvel based alpha systems
|
|
See comment before marvel_specify_io7 in
|
|
arch/alpha/kernel/core_marvel.c.
|
|
|
|
io_delay= [X86] I/O delay method
|
|
0x80
|
|
Standard port 0x80 based delay
|
|
0xed
|
|
Alternate port 0xed based delay (needed on some systems)
|
|
udelay
|
|
Simple two microseconds delay
|
|
none
|
|
No delay
|
|
|
|
ip= [IP_PNP]
|
|
See Documentation/filesystems/nfs/nfsroot.txt.
|
|
|
|
ipcmni_extend [KNL] Extend the maximum number of unique System V
|
|
IPC identifiers from 32,768 to 16,777,216.
|
|
|
|
irqaffinity= [SMP] Set the default irq affinity mask
|
|
The argument is a cpu list, as described above.
|
|
|
|
irqchip.gicv2_force_probe=
|
|
[ARM, ARM64]
|
|
Format: <bool>
|
|
Force the kernel to look for the second 4kB page
|
|
of a GICv2 controller even if the memory range
|
|
exposed by the device tree is too small.
|
|
|
|
irqchip.gicv3_nolpi=
|
|
[ARM, ARM64]
|
|
Force the kernel to ignore the availability of
|
|
LPIs (and by consequence ITSs). Intended for system
|
|
that use the kernel as a bootloader, and thus want
|
|
to let secondary kernels in charge of setting up
|
|
LPIs.
|
|
|
|
irqchip.gicv3_pseudo_nmi= [ARM64]
|
|
Enables support for pseudo-NMIs in the kernel. This
|
|
requires the kernel to be built with
|
|
CONFIG_ARM64_PSEUDO_NMI.
|
|
|
|
irqfixup [HW]
|
|
When an interrupt is not handled search all handlers
|
|
for it. Intended to get systems with badly broken
|
|
firmware running.
|
|
|
|
irqpoll [HW]
|
|
When an interrupt is not handled search all handlers
|
|
for it. Also check all handlers each timer
|
|
interrupt. Intended to get systems with badly broken
|
|
firmware running.
|
|
|
|
isapnp= [ISAPNP]
|
|
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
|
|
|
|
isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
|
|
[Deprecated - use cpusets instead]
|
|
Format: [flag-list,]<cpu-list>
|
|
|
|
Specify one or more CPUs to isolate from disturbances
|
|
specified in the flag list (default: domain):
|
|
|
|
nohz
|
|
Disable the tick when a single task runs.
|
|
|
|
A residual 1Hz tick is offloaded to workqueues, which you
|
|
need to affine to housekeeping through the global
|
|
workqueue's affinity configured via the
|
|
/sys/devices/virtual/workqueue/cpumask sysfs file, or
|
|
by using the 'domain' flag described below.
|
|
|
|
NOTE: by default the global workqueue runs on all CPUs,
|
|
so to protect individual CPUs the 'cpumask' file has to
|
|
be configured manually after bootup.
|
|
|
|
domain
|
|
Isolate from the general SMP balancing and scheduling
|
|
algorithms. Note that performing domain isolation this way
|
|
is irreversible: it's not possible to bring back a CPU to
|
|
the domains once isolated through isolcpus. It's strongly
|
|
advised to use cpusets instead to disable scheduler load
|
|
balancing through the "cpuset.sched_load_balance" file.
|
|
It offers a much more flexible interface where CPUs can
|
|
move in and out of an isolated set anytime.
|
|
|
|
You can move a process onto or off an "isolated" CPU via
|
|
the CPU affinity syscalls or cpuset.
|
|
<cpu number> begins at 0 and the maximum value is
|
|
"number of CPUs in system - 1".
|
|
|
|
The format of <cpu-list> is described above.
|
|
|
|
|
|
|
|
iucv= [HW,NET]
|
|
|
|
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:
|
|
ivrs_ioapic[10]=00:14.0
|
|
|
|
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:
|
|
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/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]
|
|
|
|
kernelcore= [KNL,X86,IA-64,PPC]
|
|
Format: nn[KMGTPE] | nn% | "mirror"
|
|
This parameter specifies the amount of memory usable by
|
|
the kernel for non-movable allocations. The requested
|
|
amount is spread evenly throughout all nodes in the
|
|
system as ZONE_NORMAL. The remaining memory is used for
|
|
movable memory in its own zone, ZONE_MOVABLE. In the
|
|
event, a node is too small to have both ZONE_NORMAL and
|
|
ZONE_MOVABLE, kernelcore memory will take priority and
|
|
other nodes will have a larger ZONE_MOVABLE.
|
|
|
|
ZONE_MOVABLE is used for the allocation of pages that
|
|
may be reclaimed or moved by the page migration
|
|
subsystem. Note that allocations like PTEs-from-HighMem
|
|
still use the HighMem zone if it exists, and the Normal
|
|
zone if it does not.
|
|
|
|
It is possible to specify the exact amount of memory in
|
|
the form of "nn[KMGTPE]", a percentage of total system
|
|
memory in the form of "nn%", or "mirror". If "mirror"
|
|
option is specified, mirrored (reliable) memory is used
|
|
for non-movable allocations and remaining memory is used
|
|
for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
|
|
are exclusive, so you cannot specify multiple forms.
|
|
|
|
kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
|
|
Format: <Controller#>[,poll interval]
|
|
The controller # is the number of the ehci usb debug
|
|
port as it is probed via PCI. The poll interval is
|
|
optional and is the number seconds in between
|
|
each poll cycle to the debug port in case you need
|
|
the functionality for interrupting the kernel with
|
|
gdb or control-c on the dbgp connection. When
|
|
not using this parameter you use sysrq-g to break into
|
|
the kernel debugger.
|
|
|
|
kgdboc= [KGDB,HW] kgdb over consoles.
|
|
Requires a tty driver that supports console polling,
|
|
or a supported polling keyboard driver (non-usb).
|
|
Serial only format: <serial_device>[,baud]
|
|
keyboard only format: kbd
|
|
keyboard and serial format: kbd,<serial_device>[,baud]
|
|
Optional Kernel mode setting:
|
|
kms, kbd format: kms,kbd
|
|
kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
|
|
|
|
kgdbwait [KGDB] Stop kernel execution and enter the
|
|
kernel debugger at the earliest opportunity.
|
|
|
|
kmac= [MIPS] korina ethernet MAC address.
|
|
Configure the RouterBoard 532 series on-chip
|
|
Ethernet adapter MAC address.
|
|
|
|
kmemleak= [KNL] Boot-time kmemleak enable/disable
|
|
Valid arguments: on, off
|
|
Default: on
|
|
Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
|
|
the default is off.
|
|
|
|
kpti= [ARM64] Control page table isolation of user
|
|
and kernel address spaces.
|
|
Default: enabled on cores which need mitigation.
|
|
0: force disabled
|
|
1: force enabled
|
|
|
|
kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
|
|
Default is 0 (don't ignore, but inject #GP)
|
|
|
|
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-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
|
|
Default is 1 (enabled)
|
|
|
|
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.
|
|
|
|
kvm-arm.vgic_v3_group0_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 group-0
|
|
system registers
|
|
|
|
kvm-arm.vgic_v3_group1_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 group-1
|
|
system registers
|
|
|
|
kvm-arm.vgic_v3_common_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 common
|
|
system registers
|
|
|
|
kvm-arm.vgic_v4_enable=
|
|
[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-intel.emulate_invalid_guest_state=
|
|
[KVM,Intel] Enable emulation of invalid guest states
|
|
Default is 0 (disabled)
|
|
|
|
kvm-intel.flexpriority=
|
|
[KVM,Intel] Disable FlexPriority feature (TPR shadow).
|
|
Default is 1 (enabled)
|
|
|
|
kvm-intel.nested=
|
|
[KVM,Intel] Enable VMX nesting (nVMX).
|
|
Default is 0 (disabled)
|
|
|
|
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.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
|
|
CVE-2018-3620.
|
|
|
|
Valid arguments: never, cond, always
|
|
|
|
always: L1D cache flush on every VMENTER.
|
|
cond: Flush L1D on VMENTER only when the code between
|
|
VMEXIT and VMENTER can leak host memory.
|
|
never: Disables the mitigation
|
|
|
|
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)
|
|
|
|
l1tf= [X86] Control mitigation of the L1TF vulnerability on
|
|
affected CPUs
|
|
|
|
The kernel PTE inversion protection is unconditionally
|
|
enabled and cannot be disabled.
|
|
|
|
full
|
|
Provides all available mitigations for the
|
|
L1TF vulnerability. Disables SMT and
|
|
enables all mitigations in the
|
|
hypervisors, i.e. unconditional L1D flush.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
full,force
|
|
Same as 'full', but disables SMT and L1D
|
|
flush runtime control. Implies the
|
|
'nosmt=force' command line option.
|
|
(i.e. sysfs control of SMT is disabled.)
|
|
|
|
flush
|
|
Leaves SMT enabled and enables the default
|
|
hypervisor mitigation, i.e. conditional
|
|
L1D flush.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
flush,nosmt
|
|
|
|
Disables SMT and enables the default
|
|
hypervisor mitigation.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
flush,nowarn
|
|
Same as 'flush', but hypervisors will not
|
|
warn when a VM is started in a potentially
|
|
insecure configuration.
|
|
|
|
off
|
|
Disables hypervisor mitigations and doesn't
|
|
emit any warnings.
|
|
It also drops the swap size and available
|
|
RAM limit restriction on both hypervisor and
|
|
bare metal.
|
|
|
|
Default is 'flush'.
|
|
|
|
For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
|
|
|
|
l2cr= [PPC]
|
|
|
|
l3cr= [PPC]
|
|
|
|
lapic [X86-32,APIC] Enable the local APIC even if BIOS
|
|
disabled it.
|
|
|
|
lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
|
|
value for LAPIC timer one-shot implementation. Default
|
|
back to the programmable timer unit in the LAPIC.
|
|
|
|
lapic_timer_c2_ok [X86,APIC] trust the local apic timer
|
|
in C2 power state.
|
|
|
|
libata.dma= [LIBATA] DMA control
|
|
libata.dma=0 Disable all PATA and SATA DMA
|
|
libata.dma=1 PATA and SATA Disk DMA only
|
|
libata.dma=2 ATAPI (CDROM) DMA only
|
|
libata.dma=4 Compact Flash DMA only
|
|
Combinations also work, so libata.dma=3 enables DMA
|
|
for disks and CDROMs, but not CFs.
|
|
|
|
libata.ignore_hpa= [LIBATA] Ignore HPA limit
|
|
libata.ignore_hpa=0 keep BIOS limits (default)
|
|
libata.ignore_hpa=1 ignore limits, using full disk
|
|
|
|
libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
|
|
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.
|
|
|
|
If only DEVICE is omitted, the parameter applies to
|
|
the port and all links and devices behind it. DEVICE
|
|
number of 0 either selects the first device or the
|
|
first fan-out link behind PMP device. It does not
|
|
select the host link. DEVICE number of 15 selects the
|
|
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.
|
|
For example, both 1.5 and 1.5G would work for 1.5Gbps.
|
|
The following configurations can be forced.
|
|
|
|
* Cable type: 40c, 80c, short40c, unk, ign or sata.
|
|
Any ID with matching PORT is used.
|
|
|
|
* SATA link speed limit: 1.5Gbps or 3.0Gbps.
|
|
|
|
* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
|
|
udma[/][16,25,33,44,66,100,133] notation is also
|
|
allowed.
|
|
|
|
* [no]ncq: Turn on or off NCQ.
|
|
|
|
* [no]ncqtrim: Turn off queued DSM TRIM.
|
|
|
|
* nohrst, nosrst, norst: suppress hard, soft
|
|
and both resets.
|
|
|
|
* rstonce: only attempt one reset during
|
|
hot-unplug link recovery
|
|
|
|
* dump_id: dump IDENTIFY data.
|
|
|
|
* atapi_dmadir: Enable ATAPI DMADIR bridge support
|
|
|
|
* 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/blockdev/ramdisk.txt.
|
|
|
|
lockd.nlm_grace_period=P [NFS] Assign grace period.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_tcpport=N [NFS] Assign TCP port.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_timeout=T [NFS] Assign timeout value.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_udpport=M [NFS] Assign UDP port.
|
|
Format: <integer>
|
|
|
|
locktorture.nreaders_stress= [KNL]
|
|
Set the number of locking read-acquisition kthreads.
|
|
Defaults to being automatically set based on the
|
|
number of online CPUs.
|
|
|
|
locktorture.nwriters_stress= [KNL]
|
|
Set the number of locking write-acquisition kthreads.
|
|
|
|
locktorture.onoff_holdoff= [KNL]
|
|
Set time (s) after boot for CPU-hotplug testing.
|
|
|
|
locktorture.onoff_interval= [KNL]
|
|
Set time (s) between CPU-hotplug operations, or
|
|
zero to disable CPU-hotplug testing.
|
|
|
|
locktorture.shuffle_interval= [KNL]
|
|
Set task-shuffle interval (jiffies). Shuffling
|
|
tasks allows some CPUs to go into dyntick-idle
|
|
mode during the locktorture test.
|
|
|
|
locktorture.shutdown_secs= [KNL]
|
|
Set time (s) after boot system shutdown. This
|
|
is useful for hands-off automated testing.
|
|
|
|
locktorture.stat_interval= [KNL]
|
|
Time (s) between statistics printk()s.
|
|
|
|
locktorture.stutter= [KNL]
|
|
Time (s) to stutter testing, for example,
|
|
specifying five seconds causes the test to run for
|
|
five seconds, wait for five seconds, and so on.
|
|
This tests the locking primitive's ability to
|
|
transition abruptly to and from idle.
|
|
|
|
locktorture.torture_type= [KNL]
|
|
Specify the locking implementation to test.
|
|
|
|
locktorture.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
|
|
Format: <irq>
|
|
|
|
loglevel= All Kernel Messages with a loglevel smaller than the
|
|
console loglevel will be printed to the console. It can
|
|
also be changed with klogd or other programs. The
|
|
loglevels are defined as follows:
|
|
|
|
0 (KERN_EMERG) system is unusable
|
|
1 (KERN_ALERT) action must be taken immediately
|
|
2 (KERN_CRIT) critical conditions
|
|
3 (KERN_ERR) error conditions
|
|
4 (KERN_WARNING) warning conditions
|
|
5 (KERN_NOTICE) normal but significant condition
|
|
6 (KERN_INFO) informational
|
|
7 (KERN_DEBUG) debug-level messages
|
|
|
|
log_buf_len=n[KMG] Sets the size of the printk ring buffer,
|
|
in bytes. n must be a power of two and greater
|
|
than the minimal size. The minimal size is defined
|
|
by LOG_BUF_SHIFT kernel config parameter. There is
|
|
also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
|
|
that allows to increase the default size depending on
|
|
the number of CPUs. See init/Kconfig for more details.
|
|
|
|
logo.nologo [FB] Disables display of the built-in Linux logo.
|
|
This may be used to provide more screen space for
|
|
kernel log messages and is useful when debugging
|
|
kernel boot problems.
|
|
|
|
lp=0 [LP] Specify parallel ports to use, e.g,
|
|
lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
|
|
lp=reset first parallel port). 'lp=0' disables the
|
|
lp=auto printer driver. 'lp=reset' (which can be
|
|
specified in addition to the ports) causes
|
|
attached printers to be reset. Using
|
|
lp=port1,port2,... specifies the parallel ports
|
|
to associate lp devices with, starting with
|
|
lp0. A port specification may be 'none' to skip
|
|
that lp device, or a parport name such as
|
|
'parport0'. Specifying 'lp=auto' instead of a
|
|
port specification list means that device IDs
|
|
from each port should be examined, to see if
|
|
an IEEE 1284-compliant printer is attached; if
|
|
so, the driver will manage that printer.
|
|
See also header of drivers/char/lp.c.
|
|
|
|
lpj=n [KNL]
|
|
Sets loops_per_jiffy to given constant, thus avoiding
|
|
time-consuming boot-time autodetection (up to 250 ms per
|
|
CPU). 0 enables autodetection (default). To determine
|
|
the correct value for your kernel, boot with normal
|
|
autodetection and see what value is printed. Note that
|
|
on SMP systems the preset will be applied to all CPUs,
|
|
which is likely to cause problems if your CPUs need
|
|
significantly divergent settings. An incorrect value
|
|
will cause delays in the kernel to be wrong, leading to
|
|
unpredictable I/O errors and other breakage. Although
|
|
unlikely, in the extreme case this might damage your
|
|
hardware.
|
|
|
|
ltpc= [NET]
|
|
Format: <io>,<irq>,<dma>
|
|
|
|
lsm.debug [SECURITY] Enable LSM initialization debugging output.
|
|
|
|
lsm=lsm1,...,lsmN
|
|
[SECURITY] Choose order of LSM initialization. This
|
|
overrides CONFIG_LSM, and the "security=" parameter.
|
|
|
|
machvec= [IA-64] Force the use of a particular machine-vector
|
|
(machvec) in a generic kernel.
|
|
Example: machvec=hpzx1_swiotlb
|
|
|
|
machtype= [Loongson] Share the same kernel image file between different
|
|
yeeloong laptop.
|
|
Example: machtype=lemote-yeeloong-2f-7inch
|
|
|
|
max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
|
|
than or equal to this physical address is ignored.
|
|
|
|
maxcpus= [SMP] Maximum number of processors that an SMP kernel
|
|
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
|
|
number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
|
|
of statically allocating a predefined number, loop
|
|
devices can be requested on-demand with the
|
|
/dev/loop-control interface.
|
|
|
|
mce [X86-32] Machine Check Exception
|
|
|
|
mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
|
|
|
|
md= [HW] RAID subsystems devices and level
|
|
See Documentation/admin-guide/md.rst.
|
|
|
|
mdacon= [MDA]
|
|
Format: <first>,<last>
|
|
Specifies range of consoles to be captured by the MDA.
|
|
|
|
mds= [X86,INTEL]
|
|
Control mitigation for the Micro-architectural Data
|
|
Sampling (MDS) 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 MDS mitigation. The
|
|
options are:
|
|
|
|
full - Enable MDS mitigation on vulnerable CPUs
|
|
full,nosmt - Enable MDS mitigation and disable
|
|
SMT on vulnerable CPUs
|
|
off - Unconditionally disable MDS mitigation
|
|
|
|
Not specifying this option is equivalent to
|
|
mds=full.
|
|
|
|
For details see: Documentation/admin-guide/hw-vuln/mds.rst
|
|
|
|
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.
|
|
[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.
|
|
|
|
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
|
|
memory.
|
|
|
|
memchunk=nn[KMG]
|
|
[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
|
|
BIOS output or other requirements. See the memmap=nn@ss
|
|
option description.
|
|
|
|
memmap=nn[KMG]@ss[KMG]
|
|
[KNL] 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].
|
|
Multiple different regions can be specified,
|
|
comma delimited.
|
|
Example:
|
|
memmap=100M@2G,100M#3G,1G!1024G
|
|
|
|
memmap=nn[KMG]#ss[KMG]
|
|
[KNL,ACPI] Mark specific memory as ACPI data.
|
|
Region of memory to be marked is from ss to ss+nn.
|
|
|
|
memmap=nn[KMG]$ss[KMG]
|
|
[KNL,ACPI] Mark specific memory as reserved.
|
|
Region of memory to be reserved is from ss to ss+nn.
|
|
Example: Exclude memory from 0x18690000-0x1869ffff
|
|
memmap=64K$0x18690000
|
|
or
|
|
memmap=0x10000$0x18690000
|
|
Some bootloaders may need an escape character before '$',
|
|
like Grub2, otherwise '$' and the following number
|
|
will be eaten.
|
|
|
|
memmap=nn[KMG]!ss[KMG]
|
|
[KNL,X86] Mark specific memory as protected.
|
|
Region of memory to be used, from ss to ss+nn.
|
|
The memory region may be marked as e820 type 12 (0xc)
|
|
and is NVDIMM or ADR memory.
|
|
|
|
memmap=<size>%<offset>-<oldtype>+<newtype>
|
|
[KNL,ACPI] Convert memory within the specified region
|
|
from <oldtype> to <newtype>. If "-<oldtype>" is left
|
|
out, the whole region will be marked as <newtype>,
|
|
even if previously unavailable. If "+<newtype>" is left
|
|
out, matching memory will be removed. Types are
|
|
specified as e820 types, e.g., 1 = RAM, 2 = reserved,
|
|
3 = ACPI, 12 = PRAM.
|
|
|
|
memory_corruption_check=0/1 [X86]
|
|
Some BIOSes seem to corrupt the first 64k of
|
|
memory when doing things like suspend/resume.
|
|
Setting this option will scan the memory
|
|
looking for corruption. Enabling this will
|
|
both detect corruption and prevent the kernel
|
|
from using the memory being corrupted.
|
|
However, its intended as a diagnostic tool; if
|
|
repeatable BIOS-originated corruption always
|
|
affects the same memory, you can use memmap=
|
|
to prevent the kernel from using that memory.
|
|
|
|
memory_corruption_check_size=size [X86]
|
|
By default it checks for corruption in the low
|
|
64k, making this memory unavailable for normal
|
|
use. Use this parameter to scan for
|
|
corruption in more or less memory.
|
|
|
|
memory_corruption_check_period=seconds [X86]
|
|
By default it checks for corruption every 60
|
|
seconds. Use this parameter to check at some
|
|
other rate. 0 disables periodic checking.
|
|
|
|
memtest= [KNL,X86,ARM,PPC] Enable memtest
|
|
Format: <integer>
|
|
default : 0 <disable>
|
|
Specifies the number of memtest passes to be
|
|
performed. Each pass selects another test
|
|
pattern from a given set of patterns. Memtest
|
|
fills the memory with this pattern, validates
|
|
memory contents and reserves bad memory
|
|
regions that are detected.
|
|
|
|
mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
|
|
Valid arguments: on, off
|
|
Default (depends on kernel configuration option):
|
|
on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
|
|
off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
|
|
mem_encrypt=on: Activate SME
|
|
mem_encrypt=off: Do not activate SME
|
|
|
|
Refer to Documentation/x86/amd-memory-encryption.txt
|
|
for details on when memory encryption can be activated.
|
|
|
|
mem_sleep_default= [SUSPEND] Default system suspend mode:
|
|
s2idle - Suspend-To-Idle
|
|
shallow - Power-On Suspend or equivalent (if supported)
|
|
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.
|
|
|
|
mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
|
|
the BIOS has incorrectly applied a workaround. TinyBIOS
|
|
version 0.98 is known to be affected, 0.99 fixes the
|
|
problem by letting the user disable the workaround.
|
|
|
|
mga= [HW,DRM]
|
|
|
|
min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
|
|
physical address is ignored.
|
|
|
|
mini2440= [ARM,HW,KNL]
|
|
Format:[0..2][b][c][t]
|
|
Default: "0tb"
|
|
MINI2440 configuration specification:
|
|
0 - The attached screen is the 3.5" TFT
|
|
1 - The attached screen is the 7" TFT
|
|
2 - The VGA Shield is attached (1024x768)
|
|
Leaving out the screen size parameter will not load
|
|
the TFT driver, and the framebuffer will be left
|
|
unconfigured.
|
|
b - Enable backlight. The TFT backlight pin will be
|
|
linked to the kernel VESA blanking code and a GPIO
|
|
LED. This parameter is not necessary when using the
|
|
VGA shield.
|
|
c - Enable the s3c camera interface.
|
|
t - Reserved for enabling touchscreen support. The
|
|
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
|
|
|
|
mitigations=
|
|
[X86,PPC,S390,ARM64] Control optional mitigations for
|
|
CPU vulnerabilities. This is a set of curated,
|
|
arch-independent options, each of which is an
|
|
aggregation of existing arch-specific options.
|
|
|
|
off
|
|
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]
|
|
nobp=0 [S390]
|
|
nospectre_v2 [X86,PPC,S390,ARM64]
|
|
spectre_v2_user=off [X86]
|
|
spec_store_bypass_disable=off [X86,PPC]
|
|
ssbd=force-off [ARM64]
|
|
l1tf=off [X86]
|
|
mds=off [X86]
|
|
|
|
auto (default)
|
|
Mitigate all CPU vulnerabilities, but leave SMT
|
|
enabled, even if it's vulnerable. This is for
|
|
users who don't want to be surprised by SMT
|
|
getting disabled across kernel upgrades, or who
|
|
have other ways of avoiding SMT-based attacks.
|
|
Equivalent to: (default behavior)
|
|
|
|
auto,nosmt
|
|
Mitigate all CPU vulnerabilities, disabling SMT
|
|
if needed. This is for users who always want to
|
|
be fully mitigated, even if it means losing SMT.
|
|
Equivalent to: l1tf=flush,nosmt [X86]
|
|
mds=full,nosmt [X86]
|
|
|
|
mminit_loglevel=
|
|
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
|
|
parameter allows control of the logging verbosity for
|
|
the additional memory initialisation checks. A value
|
|
of 0 disables mminit logging and a level of 4 will
|
|
log everything. Information is printed at KERN_DEBUG
|
|
so loglevel=8 may also need to be specified.
|
|
|
|
module.sig_enforce
|
|
[KNL] When CONFIG_MODULE_SIG is set, this means that
|
|
modules without (valid) signatures will fail to load.
|
|
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
|
|
a tap and be reported as a left button click (for
|
|
touchpads working in absolute mode only).
|
|
Format: <msecs>
|
|
mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
|
|
reporting absolute coordinates, such as tablets
|
|
mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
|
|
reporting absolute coordinates, such as tablets
|
|
|
|
movablecore= [KNL,X86,IA-64,PPC]
|
|
Format: nn[KMGTPE] | nn%
|
|
This parameter is the complement to kernelcore=, it
|
|
specifies the amount of memory used for migratable
|
|
allocations. If both kernelcore and movablecore is
|
|
specified, then kernelcore will be at *least* the
|
|
specified value but may be more. If movablecore on its
|
|
own is specified, the administrator must be careful
|
|
that the amount of memory usable for all allocations
|
|
is not too small.
|
|
|
|
movable_node [KNL] Boot-time switch to make hotplugable memory
|
|
NUMA nodes to be movable. This means that the memory
|
|
of such nodes will be usable only for movable
|
|
allocations which rules out almost all kernel
|
|
allocations. Use with caution!
|
|
|
|
MTD_Partition= [MTD]
|
|
Format: <name>,<region-number>,<size>,<offset>
|
|
|
|
MTD_Region= [MTD] Format:
|
|
<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.
|
|
|
|
mtdset= [ARM]
|
|
ARM/S3C2412 JIVE boot control
|
|
|
|
See arch/arm/mach-s3c2412/mach-jive.c
|
|
|
|
mtouchusb.raw_coordinates=
|
|
[HW] Make the MicroTouch USB driver use raw coordinates
|
|
('y', default) or cooked coordinates ('n')
|
|
|
|
mtrr_chunk_size=nn[KMG] [X86]
|
|
used for mtrr cleanup. It is largest continuous chunk
|
|
that could hold holes aka. UC entries.
|
|
|
|
mtrr_gran_size=nn[KMG] [X86]
|
|
Used for mtrr cleanup. It is granularity of mtrr block.
|
|
Default is 1.
|
|
Large value could prevent small alignment from
|
|
using up MTRRs.
|
|
|
|
mtrr_spare_reg_nr=n [X86]
|
|
Format: <integer>
|
|
Range: 0,7 : spare reg number
|
|
Default : 1
|
|
Used for mtrr cleanup. It is spare mtrr entries number.
|
|
Set to 2 or more if your graphical card needs more.
|
|
|
|
n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
|
|
|
|
netdev= [NET] Network devices parameters
|
|
Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
|
|
Note that mem_start is often overloaded to mean
|
|
something different and driver-specific.
|
|
This usage is only documented in each driver source
|
|
file if at all.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.enable_ino64=
|
|
[NFS] enable 64-bit inode numbers.
|
|
If zero, the NFS client will fake up a 32-bit inode
|
|
number for the readdir() and stat() syscalls instead
|
|
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.
|
|
This limits the number of simultaneous RPC requests
|
|
that the client can send to the NFSv4.1 server.
|
|
Note that there is little point in setting this
|
|
value higher than the max_tcp_slot_table_limit.
|
|
|
|
nfs.nfs4_disable_idmapping=
|
|
[NFSv4] When set to the default of '1', this option
|
|
ensures that both the RPC level authentication
|
|
scheme and the NFS level operations agree to use
|
|
numeric uids/gids if the mount is using the
|
|
'sec=sys' security flavour. In effect it is
|
|
disabling idmapping, which can make migration from
|
|
legacy NFSv2/v3 systems to NFSv4 easier.
|
|
Servers that do not support this mode of operation
|
|
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 =
|
|
[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
|
|
no guarantees that the file will remain unchanged
|
|
after the locks are lost.
|
|
If you want to enable the kernel legacy behaviour of
|
|
attempting to recover these locks, then set this
|
|
parameter to '1'.
|
|
The default parameter value of '0' causes the kernel
|
|
not to attempt recovery of lost locks.
|
|
|
|
nfs4.layoutstats_timer =
|
|
[NFSv4.2] Change the rate at which the kernel sends
|
|
layoutstats to the pNFS metadata server.
|
|
|
|
Setting this to value to 0 causes the kernel to use
|
|
whatever value is the default set by the layout
|
|
driver. A non-zero value sets the minimum interval
|
|
in seconds between layoutstats transmissions.
|
|
|
|
nfsd.nfs4_disable_idmapping=
|
|
[NFSv4] When set to the default of '1', the NFSv4
|
|
server will return only numeric uids and gids to
|
|
clients using auth_sys, and will accept numeric uids
|
|
and gids from such clients. This is intended to ease
|
|
migration from NFSv2/v3.
|
|
|
|
nmi_debug= [KNL,SH] Specify one or more actions to take
|
|
when a NMI is triggered.
|
|
Format: [state][,regs][,debounce][,die]
|
|
|
|
nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
|
|
Format: [panic,][nopanic,][num]
|
|
Valid num: 0 or 1
|
|
0 - turn hardlockup detector in nmi_watchdog off
|
|
1 - turn hardlockup detector in nmi_watchdog on
|
|
When panic is specified, panic when an NMI watchdog
|
|
timeout occurs (or 'nopanic' to override the opposite
|
|
default). To disable both hard and soft lockup detectors,
|
|
please see 'nowatchdog'.
|
|
This is useful when you use a panic=... timeout and
|
|
need the box quickly up again.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
|
|
caches in the slab allocator. Saves per-node memory,
|
|
but will impact performance.
|
|
|
|
noalign [KNL,ARM]
|
|
|
|
noaltinstr [S390] Disables alternative instructions patching
|
|
(CPU alternatives feature).
|
|
|
|
noapic [SMP,APIC] Tells the kernel to not make use of any
|
|
IOAPICs that may be present in the system.
|
|
|
|
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
|
|
|
|
nodelayacct [KNL] Disable per-task delay accounting
|
|
|
|
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
|
|
|
|
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.
|
|
|
|
noexec32 [X86-64]
|
|
This affects only 32-bit executables.
|
|
noexec32=on: enable non-executable mappings (default)
|
|
read doesn't imply executable mappings
|
|
noexec32=off: disable non-executable mappings
|
|
read implies executable mappings
|
|
|
|
nofpu [MIPS,SH] Disable hardware FPU at boot time.
|
|
|
|
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] 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
|
|
interrupt wake-up latency, which may improve performance
|
|
in certain environments such as networked servers or
|
|
real-time systems.
|
|
|
|
nohibernate [HIBERNATION] Disable hibernation and resume.
|
|
|
|
nohz= [KNL] Boottime enable/disable dynamic ticks
|
|
Valid arguments: on, off
|
|
Default: on
|
|
|
|
nohz_full= [KNL,BOOT,SMP,ISOL]
|
|
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
|
|
the range to maintain the timekeeping. Any CPUs
|
|
in this list will have their RCU callbacks offloaded,
|
|
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.
|
|
|
|
noinitrd [RAM] Tells the kernel not to load any configured
|
|
initial RAM disk.
|
|
|
|
nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
|
|
remapping.
|
|
[Deprecated - use intremap=off]
|
|
|
|
nointroute [IA-64]
|
|
|
|
noinvpcid [X86] Disable the INVPCID cpu feature.
|
|
|
|
nojitter [IA-64] Disables jitter checking for ITC timers.
|
|
|
|
no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
|
|
|
|
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] Disable paravirtualized steal time accounting.
|
|
steal time is computed, but won't influence scheduler
|
|
behaviour
|
|
|
|
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
|
|
|
|
nomfgpt [X86-32] Disable Multi-Function General Purpose
|
|
Timer usage (for AMD Geode machines).
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
no-scroll [VGA] Disables scrollback.
|
|
This is required for the Braillex ib80-piezo Braille
|
|
reader made by F.H. Papenmeier (Germany).
|
|
|
|
nosbagart [IA-64]
|
|
|
|
nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
|
|
|
|
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
|
|
and disable the IO APIC. legacy for "maxcpus=0".
|
|
|
|
nosoftlockup [KNL] Disable the soft-lockup detector.
|
|
|
|
nosync [HW,M68K] Disables sync negotiation for all devices.
|
|
|
|
nowatchdog [KNL] Disable both lockup detectors, i.e.
|
|
soft-lockup and NMI watchdog (hard-lockup).
|
|
|
|
nowb [ARM]
|
|
|
|
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.
|
|
|
|
nps_mtm_hs_ctr= [KNL,ARC]
|
|
This parameter sets the maximum duration, in
|
|
cycles, each HW thread of the CTOP can run
|
|
without interruptions, before HW switches it.
|
|
The actual maximum duration is 16 times this
|
|
parameter's value.
|
|
Format: integer between 1 and 255
|
|
Default: 255
|
|
|
|
nptcg= [IA-64] Override max number of concurrent global TLB
|
|
purges which is reported from either PAL_VM_SUMMARY or
|
|
SAL PALO.
|
|
|
|
nr_cpus= [SMP] Maximum number of processors that an SMP kernel
|
|
could support. nr_cpus=n : n >= 1 limits the kernel to
|
|
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.
|
|
|
|
numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
|
|
Allowed values are enable and disable
|
|
|
|
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
|
|
'node', 'default' can be specified
|
|
This can be set from sysctl after boot.
|
|
See Documentation/sysctl/vm.txt for details.
|
|
|
|
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
|
|
See Documentation/debugging-via-ohci1394.txt for more
|
|
info.
|
|
|
|
olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
|
|
Rather than timing out after 20 ms if an EC
|
|
command is not properly ACKed, override the length
|
|
of the timeout. We have interrupts disabled while
|
|
waiting for the ACK, so if this is set too high
|
|
interrupts *may* be lost!
|
|
|
|
omap_mux= [OMAP] Override bootloader pin multiplexing.
|
|
Format: <mux_mode0.mode_name=value>...
|
|
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
|
|
|
|
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)
|
|
|
|
oops=panic Always panic on oopses. Default is to just kill the
|
|
process, but there is a small probability of
|
|
deadlocking the machine.
|
|
This will also cause panics on machine check exceptions.
|
|
Useful together with panic=30 to trigger a reboot.
|
|
|
|
page_alloc.shuffle=
|
|
[KNL] Boolean flag to control whether the page allocator
|
|
should randomize its free lists. The randomization may
|
|
be automatically enabled if the kernel detects it is
|
|
running on a platform with a direct-mapped memory-side
|
|
cache, and this parameter can be used to
|
|
override/disable that behavior. The state of the flag
|
|
can be read from sysfs at:
|
|
/sys/module/page_alloc/parameters/shuffle.
|
|
|
|
page_owner= [KNL] Boot-time page_owner enabling option.
|
|
Storage of the information about who allocated
|
|
each page is disabled in default. With this switch,
|
|
we can turn it on.
|
|
on: enable the feature
|
|
|
|
page_poison= [KNL] Boot-time parameter changing the state of
|
|
poisoning on the buddy allocator, available with
|
|
CONFIG_PAGE_POISONING=y.
|
|
off: turn off poisoning (default)
|
|
on: turn on poisoning
|
|
|
|
panic= [KNL] Kernel behaviour on panic: delay <timeout>
|
|
timeout > 0: seconds before rebooting
|
|
timeout = 0: wait forever
|
|
timeout < 0: reboot immediately
|
|
Format: <timeout>
|
|
|
|
panic_print= Bitmask for printing system info when panic happens.
|
|
User can chose combination of the following bits:
|
|
bit 0: print all tasks info
|
|
bit 1: print system memory info
|
|
bit 2: print timer info
|
|
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.
|
|
|
|
parkbd.port= [HW] Parallel port number the keyboard adapter is
|
|
connected to, default is 0.
|
|
Format: <parport#>
|
|
parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
|
|
0 for XT, 1 for AT (default is AT).
|
|
Format: <mode>
|
|
|
|
parport= [HW,PPT] Specify parallel ports. 0 disables.
|
|
Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
|
|
Use 'auto' to force the driver to use any
|
|
IRQ/DMA settings detected (the default is to
|
|
ignore detected IRQ/DMA settings because of
|
|
possible conflicts). You can specify the base
|
|
address, IRQ, and DMA settings; IRQ and DMA
|
|
should be numbers, or 'auto' (for using detected
|
|
settings on that particular port), or 'nofifo'
|
|
(to avoid using a FIFO even if it is detected).
|
|
Parallel ports are assigned in the order they
|
|
are specified on the command line, starting
|
|
with parport0.
|
|
|
|
parport_init_mode= [HW,PPT]
|
|
Configure VIA parallel port to operate in
|
|
a specific mode. This is necessary on Pegasos
|
|
computer where firmware has no options for setting
|
|
up parallel port mode and sets it to spp.
|
|
Currently this function knows 686a and 8231 chips.
|
|
Format: [spp|ps2|epp|ecp|ecpepp]
|
|
|
|
pause_on_oops=
|
|
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/blockdev/paride.txt.
|
|
|
|
pci=option[,option...] [PCI] various PCI subsystem options.
|
|
|
|
Some options herein operate on a specific device
|
|
or a set of devices (<pci_dev>). These are
|
|
specified in one of the following formats:
|
|
|
|
[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
|
|
pci:<vendor>:<device>[:<subvendor>:<subdevice>]
|
|
|
|
Note: the first format specifies a PCI
|
|
bus/device/function address which may change
|
|
if new hardware is inserted, if motherboard
|
|
firmware changes, or due to changes caused
|
|
by other kernel parameters. If the
|
|
domain is left unspecified, it is
|
|
taken to be zero. Optionally, a path
|
|
to a device through multiple device/function
|
|
addresses can be specified after the base
|
|
address (this is more robust against
|
|
renumbering issues). The second format
|
|
selects devices using IDs from the
|
|
configuration space which may match multiple
|
|
devices in the system.
|
|
|
|
earlydump dump PCI config space before the kernel
|
|
changes anything
|
|
off [X86] don't probe for the PCI bus
|
|
bios [X86-32] force use of PCI BIOS, don't access
|
|
the hardware directly. Use this if your machine
|
|
has a non-standard PCI host bridge.
|
|
nobios [X86-32] disallow use of PCI BIOS, only direct
|
|
hardware access methods are allowed. Use this
|
|
if you experience crashes upon bootup and you
|
|
suspect they are caused by the BIOS.
|
|
conf1 [X86] Force use of PCI Configuration Access
|
|
Mechanism 1 (config address in IO port 0xCF8,
|
|
data in IO port 0xCFC, both 32-bit).
|
|
conf2 [X86] Force use of PCI Configuration Access
|
|
Mechanism 2 (IO port 0xCF8 is an 8-bit port for
|
|
the function, IO port 0xCFA, also 8-bit, sets
|
|
bus number. The config space is then accessed
|
|
through ports 0xC000-0xCFFF).
|
|
See http://wiki.osdev.org/PCI for more info
|
|
on the configuration access mechanisms.
|
|
noaer [PCIE] If the PCIEAER kernel config parameter is
|
|
enabled, this kernel boot option can be used to
|
|
disable the use of PCIE advanced error reporting.
|
|
nodomains [PCI] Disable support for multiple PCI
|
|
root domains (aka PCI segments, in ACPI-speak).
|
|
nommconf [X86] Disable use of MMCONFIG for PCI
|
|
Configuration
|
|
check_enable_amd_mmconf [X86] check for and enable
|
|
properly configured MMIO access to PCI
|
|
config space on AMD family 10h CPU
|
|
nomsi [MSI] If the PCI_MSI kernel config parameter is
|
|
enabled, this kernel boot option can be used to
|
|
disable the use of MSI interrupts system-wide.
|
|
noioapicquirk [APIC] Disable all boot interrupt quirks.
|
|
Safety option to keep boot IRQs enabled. This
|
|
should never be necessary.
|
|
ioapicreroute [APIC] Enable rerouting of boot IRQs to the
|
|
primary IO-APIC for bridges that cannot disable
|
|
boot IRQs. This fixes a source of spurious IRQs
|
|
when the system masks IRQs.
|
|
noioapicreroute [APIC] Disable workaround that uses the
|
|
boot IRQ equivalent of an IRQ that connects to
|
|
a chipset where boot IRQs cannot be disabled.
|
|
The opposite of ioapicreroute.
|
|
biosirq [X86-32] Use PCI BIOS calls to get the interrupt
|
|
routing table. These calls are known to be buggy
|
|
on several machines and they hang the machine
|
|
when used, but on other computers it's the only
|
|
way to get the interrupt routing table. Try
|
|
this option if the kernel is unable to allocate
|
|
IRQs or discover secondary PCI buses on your
|
|
motherboard.
|
|
rom [X86] Assign address space to expansion ROMs.
|
|
Use with caution as certain devices share
|
|
address decoders between ROMs and other
|
|
resources.
|
|
norom [X86] Do not assign address space to
|
|
expansion ROMs that do not already have
|
|
BIOS assigned address ranges.
|
|
nobar [X86] Do not assign address space to the
|
|
BARs that weren't assigned by the BIOS.
|
|
irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
|
|
assigned automatically to PCI devices. You can
|
|
make the kernel exclude IRQs of your ISA cards
|
|
this way.
|
|
pirqaddr=0xAAAAA [X86] Specify the physical address
|
|
of the PIRQ table (normally generated
|
|
by the BIOS) if it is outside the
|
|
F0000h-100000h range.
|
|
lastbus=N [X86] Scan all buses thru bus #N. Can be
|
|
useful if the kernel is unable to find your
|
|
secondary buses and you want to tell it
|
|
explicitly which ones they are.
|
|
assign-busses [X86] Always assign all PCI bus
|
|
numbers ourselves, overriding
|
|
whatever the firmware may have done.
|
|
usepirqmask [X86] Honor the possible IRQ mask stored
|
|
in the BIOS $PIR table. This is needed on
|
|
some systems with broken BIOSes, notably
|
|
some HP Pavilion N5400 and Omnibook XE3
|
|
notebooks. This will have no effect if ACPI
|
|
IRQ routing is enabled.
|
|
noacpi [X86] Do not use ACPI for IRQ routing
|
|
or for PCI scanning.
|
|
use_crs [X86] Use PCI host bridge window information
|
|
from ACPI. On BIOSes from 2008 or later, this
|
|
is enabled by default. If you need to use this,
|
|
please report a bug.
|
|
nocrs [X86] Ignore PCI host bridge windows from ACPI.
|
|
If you need to use this, please report a bug.
|
|
routeirq Do IRQ routing for all PCI devices.
|
|
This is normally done in pci_enable_device(),
|
|
so this option is a temporary workaround
|
|
for broken drivers that don't call it.
|
|
skip_isa_align [X86] do not align io start addr, so can
|
|
handle more pci cards
|
|
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
|
|
is read. But various workarounds are disabled
|
|
and some IOMMU drivers will not work.
|
|
bfsort Sort PCI devices into breadth-first order.
|
|
This sorting is done to get a device
|
|
order compatible with older (<= 2.4) kernels.
|
|
nobfsort Don't sort PCI devices into breadth-first order.
|
|
pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
|
|
tuning and use the BIOS-configured MPS defaults.
|
|
pcie_bus_safe Set every device's MPS to the largest value
|
|
supported by all devices below the root complex.
|
|
pcie_bus_perf Set device MPS to the largest allowable MPS
|
|
based on its parent bus. Also set MRRS (Max
|
|
Read Request Size) to the largest supported
|
|
value (no larger than the MPS that the device
|
|
or bus can support) for best performance.
|
|
pcie_bus_peer2peer Set every device's MPS to 128B, which
|
|
every device is guaranteed to support. This
|
|
configuration allows peer-to-peer DMA between
|
|
any pair of devices, possibly at the cost of
|
|
reduced performance. This also guarantees
|
|
that hot-added devices will work.
|
|
cbiosize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for the CardBus bridge's IO window.
|
|
The default value is 256 bytes.
|
|
cbmemsize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for the CardBus bridge's memory
|
|
window. The default value is 64 megabytes.
|
|
resource_alignment=
|
|
Format:
|
|
[<order of align>@]<pci_dev>[; ...]
|
|
Specifies alignment and device to reassign
|
|
aligned memory resources. How to
|
|
specify the device is described above.
|
|
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
|
|
the default.
|
|
off: Turn ECRC off
|
|
on: Turn ECRC on.
|
|
hpiosize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for hotplug bridge's IO window.
|
|
Default size is 256 bytes.
|
|
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
|
|
devices.
|
|
off: Turn realloc off
|
|
on: Turn realloc on
|
|
realloc same as realloc=on
|
|
noari do not use PCIe ARI.
|
|
noats [PCIE, Intel-IOMMU, AMD-IOMMU]
|
|
do not use PCIe ATS (and IOMMU device IOTLB).
|
|
pcie_scan_all Scan all possible PCIe devices. Otherwise we
|
|
only look for one device below a PCIe downstream
|
|
port.
|
|
big_root_window Try to add a big 64bit memory window to the PCIe
|
|
root complex on AMD CPUs. Some GFX hardware
|
|
can resize a BAR to allow access to all VRAM.
|
|
Adding the window is slightly risky (it may
|
|
conflict with unreported devices), so this
|
|
taints the kernel.
|
|
disable_acs_redir=<pci_dev>[; ...]
|
|
Specify one or more PCI devices (in the format
|
|
specified above) separated by semicolons.
|
|
Each device specified will have the PCI ACS
|
|
redirect capabilities forced off which will
|
|
allow P2P traffic between devices through
|
|
bridges without forcing it upstream. Note:
|
|
this removes isolation between devices and
|
|
may put more devices in an IOMMU group.
|
|
force_floating [S390] Force usage of floating interrupts.
|
|
nomio [S390] Do not use MIO instructions.
|
|
|
|
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
|
|
Management.
|
|
off Disable ASPM.
|
|
force Enable ASPM even on devices that claim not to support it.
|
|
WARNING: Forcing ASPM on may cause system lockups.
|
|
|
|
pcie_ports= [PCIE] PCIe port services handling:
|
|
native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
|
|
even if the platform doesn't give the OS permission to
|
|
use them. This may cause conflicts if the platform
|
|
also tries to use these services.
|
|
compat Disable native PCIe services (PME, AER, DPC, PCIe
|
|
hotplug).
|
|
|
|
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).
|
|
|
|
pcmv= [HW,PCMCIA] BadgePAD 4
|
|
|
|
pd_ignore_unused
|
|
[PM]
|
|
Keep all power-domains already enabled by bootloader on,
|
|
even if no driver has claimed them. This is useful
|
|
for debug and development, but should not be
|
|
needed on a platform with proper driver support.
|
|
|
|
pd. [PARIDE]
|
|
See Documentation/blockdev/paride.txt.
|
|
|
|
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
|
|
boot time.
|
|
Format: { 0 | 1 }
|
|
See arch/parisc/kernel/pdc_chassis.c
|
|
|
|
percpu_alloc= Select which percpu first chunk allocator to use.
|
|
Currently supported values are "embed" and "page".
|
|
Archs may support subset or none of the selections.
|
|
See comments in mm/percpu.c for details on each
|
|
allocator. This parameter is primarily for debugging
|
|
and performance comparison.
|
|
|
|
pf. [PARIDE]
|
|
See Documentation/blockdev/paride.txt.
|
|
|
|
pg. [PARIDE]
|
|
See Documentation/blockdev/paride.txt.
|
|
|
|
pirq= [SMP,APIC] Manual mp-table setup
|
|
See Documentation/x86/i386/IO-APIC.txt.
|
|
|
|
plip= [PPT,NET] Parallel port network link
|
|
Format: { parport<nr> | timid | 0 }
|
|
See also Documentation/admin-guide/parport.rst.
|
|
|
|
pmtmr= [X86] Manual setup of pmtmr I/O Port.
|
|
Override pmtimer IOPort with a hex value.
|
|
e.g. pmtmr=0x508
|
|
|
|
pnp.debug=1 [PNP]
|
|
Enable PNP debug messages (depends on the
|
|
CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
|
|
via /sys/module/pnp/parameters/debug. We always show
|
|
current resource usage; turning this on also shows
|
|
possible settings and some assignment information.
|
|
|
|
pnpacpi= [ACPI]
|
|
{ off }
|
|
|
|
pnpbios= [ISAPNP]
|
|
{ on | off | curr | res | no-curr | no-res }
|
|
|
|
pnp_reserve_irq=
|
|
[ISAPNP] Exclude IRQs for the autoconfiguration
|
|
|
|
pnp_reserve_dma=
|
|
[ISAPNP] Exclude DMAs for the autoconfiguration
|
|
|
|
pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
|
|
Ranges are in pairs (I/O port base and size).
|
|
|
|
pnp_reserve_mem=
|
|
[ISAPNP] Exclude memory regions for the
|
|
autoconfiguration.
|
|
Ranges are in pairs (memory base and size).
|
|
|
|
ports= [IP_VS_FTP] IPVS ftp helper module
|
|
Default is 21.
|
|
Up to 8 (IP_VS_APP_MAX_PORTS) ports
|
|
may be specified.
|
|
Format: <port>,<port>....
|
|
|
|
powersave=off [PPC] This option disables power saving features.
|
|
It specifically disables cpuidle and sets the
|
|
platform machine description specific power_save
|
|
function to NULL. On Idle the CPU just reduces
|
|
execution priority.
|
|
|
|
ppc_strict_facility_enable
|
|
[PPC] This option catches any kernel floating point,
|
|
Altivec, VSX and SPE outside of regions specifically
|
|
allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
|
|
There is some performance impact when enabling this.
|
|
|
|
ppc_tm= [PPC]
|
|
Format: {"off"}
|
|
Disable Hardware Transactional Memory
|
|
|
|
print-fatal-signals=
|
|
[KNL] debug: print fatal signals
|
|
|
|
If enabled, warn about various signal handling
|
|
related application anomalies: too many signals,
|
|
too many POSIX.1 timers, fatal signals causing a
|
|
coredump - etc.
|
|
|
|
If you hit the warning due to signal overflow,
|
|
you might want to try "ulimit -i unlimited".
|
|
|
|
default: off.
|
|
|
|
printk.always_kmsg_dump=
|
|
Trigger kmsg_dump for cases other than kernel oops or
|
|
panics
|
|
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)
|
|
|
|
processor.max_cstate= [HW,ACPI]
|
|
Limit processor to maximum C-state
|
|
max_cstate=9 overrides any DMI blacklist limit.
|
|
|
|
processor.nocst [HW,ACPI]
|
|
Ignore the _CST method to determine C-states,
|
|
instead using the legacy FADT method
|
|
|
|
profile= [KNL] Enable kernel profiling via /proc/profile
|
|
Format: [<profiletype>,]<number>
|
|
Param: <profiletype>: "schedule", "sleep", or "kvm"
|
|
[defaults to kernel profiling]
|
|
Param: "schedule" - profile schedule points.
|
|
Param: "sleep" - profile D-state sleeping (millisecs).
|
|
Requires CONFIG_SCHEDSTATS
|
|
Param: "kvm" - profile VM exits.
|
|
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/blockdev/ramdisk.txt.
|
|
|
|
psi= [KNL] Enable or disable pressure stall information
|
|
tracking.
|
|
Format: <bool>
|
|
|
|
psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
|
|
probe for; one of (bare|imps|exps|lifebook|any).
|
|
psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
|
|
per second.
|
|
psmouse.resetafter= [HW,MOUSE]
|
|
Try to reset the device after so many bad packets
|
|
(0 = never).
|
|
psmouse.resolution=
|
|
[HW,MOUSE] Set desired mouse resolution, in dpi.
|
|
psmouse.smartscroll=
|
|
[HW,MOUSE] Controls Logitech smartscroll autorepeat.
|
|
0 = disabled, 1 = enabled (default).
|
|
|
|
pstore.backend= Specify the name of the pstore backend to use
|
|
|
|
pt. [PARIDE]
|
|
See Documentation/blockdev/paride.txt.
|
|
|
|
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.
|
|
|
|
on - unconditionally enable
|
|
off - unconditionally disable
|
|
auto - kernel detects whether your CPU model is
|
|
vulnerable to issues that PTI mitigates
|
|
|
|
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.
|
|
|
|
quiet [KNL] Disable most log messages
|
|
|
|
r128= [HW,DRM]
|
|
|
|
raid= [HW,RAID]
|
|
See Documentation/admin-guide/md.rst.
|
|
|
|
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
|
|
See Documentation/blockdev/ramdisk.txt.
|
|
|
|
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.
|
|
|
|
ras=option[,option,...] [KNL] RAS-specific options
|
|
|
|
cec_disable [X86]
|
|
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_nocb_poll [KNL]
|
|
Rather than requiring that offloaded CPUs
|
|
(specified by rcu_nocbs= above) explicitly
|
|
awaken the corresponding "rcuoN" kthreads,
|
|
make these kthreads poll for callbacks.
|
|
This improves the real-time response for the
|
|
offloaded CPUs by relieving them of the need to
|
|
wake up the corresponding kthread, but degrades
|
|
energy efficiency by requiring that the kthreads
|
|
periodically wake up to do the polling.
|
|
|
|
rcutree.blimit= [KNL]
|
|
Set maximum number of finished RCU callbacks to
|
|
process in one batch.
|
|
|
|
rcutree.dump_tree= [KNL]
|
|
Dump the structure of the rcu_node combining tree
|
|
out at early boot. This is used for diagnostic
|
|
purposes, to verify correct tree setup.
|
|
|
|
rcutree.gp_cleanup_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period cleanup.
|
|
|
|
rcutree.gp_init_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period initialization.
|
|
|
|
rcutree.gp_preinit_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period pre-initialization, that is,
|
|
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.
|
|
Units are jiffies, minimum value is zero,
|
|
and maximum value is HZ.
|
|
|
|
rcutree.jiffies_till_next_fqs= [KNL]
|
|
Set delay between subsequent attempts to force
|
|
quiescent states. Units are jiffies, minimum
|
|
value is one, and maximum value is HZ.
|
|
|
|
rcutree.jiffies_till_sched_qs= [KNL]
|
|
Set required age in jiffies for a
|
|
given grace period before RCU starts
|
|
soliciting quiescent-state help from
|
|
rcu_note_context_switch() and cond_resched().
|
|
If not specified, the kernel will calculate
|
|
a value based on the most recent settings
|
|
of rcutree.jiffies_till_first_fqs
|
|
and rcutree.jiffies_till_next_fqs.
|
|
This calculated value may be viewed in
|
|
rcutree.jiffies_to_sched_qs. Any attempt to set
|
|
rcutree.jiffies_to_sched_qs will be cheerfully
|
|
overwritten.
|
|
|
|
rcutree.kthread_prio= [KNL,BOOT]
|
|
Set the SCHED_FIFO priority of the RCU per-CPU
|
|
kthreads (rcuc/N). This value is also used for
|
|
the priority of the RCU boost threads (rcub/N)
|
|
and for the RCU grace-period kthreads (rcu_bh,
|
|
rcu_preempt, and rcu_sched). If RCU_BOOST is
|
|
set, valid values are 1-99 and the default is 1
|
|
(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_leader_stride= [KNL]
|
|
Set the number of NOCB kthread groups, which
|
|
defaults to the square root of the number of
|
|
CPUs. Larger numbers reduces the wakeup overhead
|
|
on the per-CPU grace-period kthreads, but increases
|
|
that same overhead on each group's leader.
|
|
|
|
rcutree.qhimark= [KNL]
|
|
Set threshold of queued RCU callbacks beyond which
|
|
batch limiting is disabled.
|
|
|
|
rcutree.qlowmark= [KNL]
|
|
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.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_kick_kthreads= [KNL]
|
|
Cause the grace-period kthread to get an extra
|
|
wake_up() if it sleeps three times longer than
|
|
it should at force-quiescent-state time.
|
|
This wake_up() will be accompanied by a
|
|
WARN_ONCE() splat and an ftrace_dump().
|
|
|
|
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]
|
|
Measure performance of asynchronous
|
|
grace-period primitives such as call_rcu().
|
|
|
|
rcuperf.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]
|
|
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_type= [KNL]
|
|
Specify the RCU implementation to test.
|
|
|
|
rcuperf.shutdown= [KNL]
|
|
Shut the system down after performance tests
|
|
complete. This is useful for hands-off automated
|
|
testing.
|
|
|
|
rcuperf.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
rcuperf.writer_holdoff= [KNL]
|
|
Write-side holdoff between grace periods,
|
|
in microseconds. The default of zero says
|
|
no holdoff.
|
|
|
|
rcutorture.fqs_duration= [KNL]
|
|
Set duration of force_quiescent_state bursts
|
|
in microseconds.
|
|
|
|
rcutorture.fqs_holdoff= [KNL]
|
|
Set holdoff time within force_quiescent_state bursts
|
|
in microseconds.
|
|
|
|
rcutorture.fqs_stutter= [KNL]
|
|
Set wait time between force_quiescent_state bursts
|
|
in seconds.
|
|
|
|
rcutorture.fwd_progress= [KNL]
|
|
Enable RCU grace-period forward-progress testing
|
|
for the types of RCU supporting this notion.
|
|
|
|
rcutorture.fwd_progress_div= [KNL]
|
|
Specify the fraction of a CPU-stall-warning
|
|
period to do tight-loop forward-progress testing.
|
|
|
|
rcutorture.fwd_progress_holdoff= [KNL]
|
|
Number of seconds to wait between successive
|
|
forward-progress tests.
|
|
|
|
rcutorture.fwd_progress_need_resched= [KNL]
|
|
Enclose cond_resched() calls within checks for
|
|
need_resched() during tight-loop forward-progress
|
|
testing.
|
|
|
|
rcutorture.gp_cond= [KNL]
|
|
Use conditional/asynchronous update-side
|
|
primitives, if available.
|
|
|
|
rcutorture.gp_exp= [KNL]
|
|
Use expedited update-side primitives, if available.
|
|
|
|
rcutorture.gp_normal= [KNL]
|
|
Use normal (non-expedited) asynchronous
|
|
update-side primitives, if available.
|
|
|
|
rcutorture.gp_sync= [KNL]
|
|
Use normal (non-expedited) synchronous
|
|
update-side primitives, if available. If all
|
|
of rcutorture.gp_cond=, rcutorture.gp_exp=,
|
|
rcutorture.gp_normal=, and rcutorture.gp_sync=
|
|
are zero, rcutorture acts as if is interpreted
|
|
they are all non-zero.
|
|
|
|
rcutorture.n_barrier_cbs= [KNL]
|
|
Set callbacks/threads for rcu_barrier() testing.
|
|
|
|
rcutorture.nfakewriters= [KNL]
|
|
Set number of concurrent RCU writers. These just
|
|
stress RCU, they don't participate in the actual
|
|
test, hence the "fake".
|
|
|
|
rcutorture.nreaders= [KNL]
|
|
Set number of RCU readers. The value -1 selects
|
|
N-1, where N is the number of CPUs. A value
|
|
"n" less than -1 selects N-n-2, where N is again
|
|
the number of CPUs. For example, -2 selects N
|
|
(the number of CPUs), -3 selects N+1, and so on.
|
|
|
|
rcutorture.object_debug= [KNL]
|
|
Enable debug-object double-call_rcu() testing.
|
|
|
|
rcutorture.onoff_holdoff= [KNL]
|
|
Set time (s) after boot for CPU-hotplug testing.
|
|
|
|
rcutorture.onoff_interval= [KNL]
|
|
Set time (jiffies) between CPU-hotplug operations,
|
|
or zero to disable CPU-hotplug testing.
|
|
|
|
rcutorture.shuffle_interval= [KNL]
|
|
Set task-shuffle interval (s). Shuffling tasks
|
|
allows some CPUs to go into dyntick-idle mode
|
|
during the rcutorture test.
|
|
|
|
rcutorture.shutdown_secs= [KNL]
|
|
Set time (s) after boot system shutdown. This
|
|
is useful for hands-off automated testing.
|
|
|
|
rcutorture.stall_cpu= [KNL]
|
|
Duration of CPU stall (s) to test RCU CPU stall
|
|
warnings, zero to disable.
|
|
|
|
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.stat_interval= [KNL]
|
|
Time (s) between statistics printk()s.
|
|
|
|
rcutorture.stutter= [KNL]
|
|
Time (s) to stutter testing, for example, specifying
|
|
five seconds causes the test to run for five seconds,
|
|
wait for five seconds, and so on. This tests RCU's
|
|
ability to transition abruptly to and from idle.
|
|
|
|
rcutorture.test_boost= [KNL]
|
|
Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
|
|
"Maybe" means test if the RCU implementation
|
|
under test support RCU priority boosting.
|
|
|
|
rcutorture.test_boost_duration= [KNL]
|
|
Duration (s) of each individual boost test.
|
|
|
|
rcutorture.test_boost_interval= [KNL]
|
|
Interval (s) between each boost test.
|
|
|
|
rcutorture.test_no_idle_hz= [KNL]
|
|
Test RCU's dyntick-idle handling. See also the
|
|
rcutorture.shuffle_interval parameter.
|
|
|
|
rcutorture.torture_type= [KNL]
|
|
Specify the RCU implementation to test.
|
|
|
|
rcutorture.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
rcupdate.rcu_cpu_stall_suppress= [KNL]
|
|
Suppress RCU CPU stall warning messages.
|
|
|
|
rcupdate.rcu_cpu_stall_timeout= [KNL]
|
|
Set timeout for RCU CPU stall warning messages.
|
|
|
|
rcupdate.rcu_expedited= [KNL]
|
|
Use expedited grace-period primitives, for
|
|
example, synchronize_rcu_expedited() instead
|
|
of synchronize_rcu(). This reduces latency,
|
|
but can increase CPU utilization, degrade
|
|
real-time latency, and degrade energy efficiency.
|
|
No effect on CONFIG_TINY_RCU kernels.
|
|
|
|
rcupdate.rcu_normal= [KNL]
|
|
Use only normal grace-period primitives,
|
|
for example, synchronize_rcu() instead of
|
|
synchronize_rcu_expedited(). This improves
|
|
real-time latency, CPU utilization, and
|
|
energy efficiency, but can expose users to
|
|
increased grace-period latency. This parameter
|
|
overrides rcupdate.rcu_expedited. No effect on
|
|
CONFIG_TINY_RCU kernels.
|
|
|
|
rcupdate.rcu_normal_after_boot= [KNL]
|
|
Once boot has completed (that is, after
|
|
rcu_end_inkernel_boot() has been invoked), use
|
|
only normal grace-period primitives. No effect
|
|
on CONFIG_TINY_RCU kernels.
|
|
|
|
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.
|
|
|
|
rcupdate.rcu_self_test= [KNL]
|
|
Run the RCU early boot self tests
|
|
|
|
rdinit= [KNL]
|
|
Format: <full_path>
|
|
Run specified binary instead of /init from the ramdisk,
|
|
used for early userspace startup. See initrd.
|
|
|
|
rdt= [HW,X86,RDT]
|
|
Turn on/off individual RDT features. List is:
|
|
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
|
|
mba.
|
|
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]] \
|
|
[[,]s[mp]#### \
|
|
[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
|
|
[[,]f[orce]
|
|
Where reboot_mode is one of warm (soft) or cold (hard) or gpio
|
|
(prefix with 'panic_' to set mode for panic
|
|
reboot only),
|
|
reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
|
|
reboot_force is either force or not specified,
|
|
reboot_cpu is s[mp]#### with #### being the processor
|
|
to be used for rebooting.
|
|
|
|
relax_domain_level=
|
|
[KNL, SMP] Set scheduler's default relax_domain_level.
|
|
See Documentation/cgroup-v1/cpusets.txt.
|
|
|
|
reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
|
|
Format: <base1>,<size1>[,<base2>,<size2>,...]
|
|
Reserve I/O ports or memory so the kernel won't use
|
|
them. If <base> is less than 0x10000, the region
|
|
is assumed to be I/O ports; otherwise it is memory.
|
|
|
|
reservetop= [X86-32]
|
|
Format: nn[KMG]
|
|
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.
|
|
|
|
resume= [SWSUSP]
|
|
Specify the partition device for software suspend
|
|
Format:
|
|
{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
|
|
|
|
resume_offset= [SWSUSP]
|
|
Specify the offset from the beginning of the partition
|
|
given by "resume=" at which the swap header is located,
|
|
in <PAGE_SIZE> units (needed only for swap files).
|
|
See Documentation/power/swsusp-and-swap-files.txt
|
|
|
|
resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
|
|
read the resume files
|
|
|
|
resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
|
|
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
|
|
|
|
rfkill.default_state=
|
|
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
|
|
etc. communication is blocked by default.
|
|
1 Unblocked.
|
|
|
|
rfkill.master_switch_mode=
|
|
0 The "airplane mode" button does nothing.
|
|
1 The "airplane mode" button toggles between everything
|
|
blocked and the previous configuration.
|
|
2 The "airplane mode" button toggles between everything
|
|
blocked and everything unblocked.
|
|
|
|
rhash_entries= [KNL,NET]
|
|
Set number of hash buckets for route cache
|
|
|
|
ring3mwait=disable
|
|
[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
|
|
CPUs.
|
|
|
|
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.
|
|
|
|
rockchip.usb_uart
|
|
Enable the uart passthrough on the designated usb port
|
|
on Rockchip SoCs. When active, the signals of the
|
|
debug-uart get routed to the D+ and D- pins of the usb
|
|
port and the regular usb controller gets disabled.
|
|
|
|
root= [KNL] Root filesystem
|
|
See name_to_dev_t comment in init/do_mounts.c.
|
|
|
|
rootdelay= [KNL] Delay (in seconds) to pause before attempting to
|
|
mount the root filesystem
|
|
|
|
rootflags= [KNL] Set root filesystem mount option string
|
|
|
|
rootfstype= [KNL] Set root filesystem type
|
|
|
|
rootwait [KNL] Wait (indefinitely) for root device to show up.
|
|
Useful for devices that are detected asynchronously
|
|
(e.g. USB and MMC devices).
|
|
|
|
rproc_mem=nn[KMG][@address]
|
|
[KNL,ARM,CMA] Remoteproc physical memory block.
|
|
Memory area to be used by remote processor image,
|
|
managed by CMA.
|
|
|
|
rw [KNL] Mount root device read-write on boot
|
|
|
|
S [KNL] Run init in single mode
|
|
|
|
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.
|
|
|
|
sa1100ir [NET]
|
|
See drivers/net/irda/sa1100_ir.c.
|
|
|
|
sbni= [NET] Granch SBNI12 leased line adapter
|
|
|
|
sched_debug [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.
|
|
|
|
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.
|
|
Format: { "0" | "1" }
|
|
0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
|
|
1 -- enable.
|
|
Note: increases power consumption, thus should only be
|
|
enabled if running jitter sensitive (HPC/RT) workloads.
|
|
|
|
security= [SECURITY] Choose a legacy "major" security module to
|
|
enable at boot. This has been deprecated by the
|
|
"lsm=" parameter.
|
|
|
|
selinux= [SELINUX] Disable or enable SELinux at boot time.
|
|
Format: { "0" | "1" }
|
|
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.
|
|
|
|
serialnumber [BUGS=X86-32]
|
|
|
|
shapers= [NET]
|
|
Maximal number of shapers.
|
|
|
|
simeth= [IA-64]
|
|
simscsi=
|
|
|
|
slram= [HW,MTD]
|
|
|
|
slab_nomerge [MM]
|
|
Disable merging of slabs with similar size. May be
|
|
necessary if there is some reason to distinguish
|
|
allocs to different slabs, especially in hardened
|
|
environments where the risk of heap overflows and
|
|
layout control by attackers can usually be
|
|
frustrated by disabling merging. This will reduce
|
|
most of the exposure of a heap attack to a single
|
|
cache (risks via metadata attacks are mostly
|
|
unchanged). Debug options disable merging on their
|
|
own.
|
|
For more information see Documentation/vm/slub.rst.
|
|
|
|
slab_max_order= [MM, SLAB]
|
|
Determines the maximum allowed order for slabs.
|
|
A high setting may cause OOMs due to memory
|
|
fragmentation. Defaults to 1 for systems with
|
|
more than 32MB of RAM, 0 otherwise.
|
|
|
|
slub_debug[=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.
|
|
|
|
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.
|
|
|
|
slub_min_objects= [MM, SLUB]
|
|
The minimum number of objects per slab. SLUB will
|
|
increase the slab order up to slub_max_order to
|
|
generate a sufficiently large slab able to contain
|
|
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.
|
|
|
|
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.
|
|
|
|
slub_nomerge [MM, SLUB]
|
|
Same with slab_nomerge. This is supported for legacy.
|
|
See slab_nomerge for more information.
|
|
|
|
smart2= [HW]
|
|
Format: <io1>[,<io2>[,...,<io8>]]
|
|
|
|
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
|
|
smsc-ircc2.ircc_fir= [HW] FIR base I/O port
|
|
smsc-ircc2.ircc_irq= [HW] IRQ line
|
|
smsc-ircc2.ircc_dma= [HW] DMA channel
|
|
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
|
|
0: Toshiba Satellite 1800 (GP data pin select)
|
|
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>
|
|
|
|
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.
|
|
|
|
softlockup_all_cpu_backtrace=
|
|
[KNL] Should the soft-lockup detector generate
|
|
backtraces on all cpus.
|
|
Format: <integer>
|
|
|
|
sonypi.*= [HW] Sony Programmable I/O Control Device driver
|
|
See Documentation/laptops/sonypi.txt
|
|
|
|
spectre_v2= [X86] Control mitigation of Spectre variant 2
|
|
(indirect branch speculation) vulnerability.
|
|
The default operation protects the kernel from
|
|
user space attacks.
|
|
|
|
on - unconditionally enable, implies
|
|
spectre_v2_user=on
|
|
off - unconditionally disable, implies
|
|
spectre_v2_user=off
|
|
auto - kernel detects whether your CPU model is
|
|
vulnerable
|
|
|
|
Selecting 'on' will, and 'auto' may, choose a
|
|
mitigation method at run time according to the
|
|
CPU, the available microcode, the setting of the
|
|
CONFIG_RETPOLINE configuration option, and the
|
|
compiler with which the kernel was built.
|
|
|
|
Selecting 'on' will also enable the mitigation
|
|
against user space to user space task attacks.
|
|
|
|
Selecting 'off' will disable both the kernel and
|
|
the user space protections.
|
|
|
|
Specific mitigations can also be selected manually:
|
|
|
|
retpoline - replace indirect branches
|
|
retpoline,generic - google's original retpoline
|
|
retpoline,amd - AMD-specific minimal thunk
|
|
|
|
Not specifying this option is equivalent to
|
|
spectre_v2=auto.
|
|
|
|
spectre_v2_user=
|
|
[X86] Control mitigation of Spectre variant 2
|
|
(indirect branch speculation) vulnerability between
|
|
user space tasks
|
|
|
|
on - Unconditionally enable mitigations. Is
|
|
enforced by spectre_v2=on
|
|
|
|
off - Unconditionally disable mitigations. Is
|
|
enforced by spectre_v2=off
|
|
|
|
prctl - Indirect branch speculation is enabled,
|
|
but mitigation can be enabled via prctl
|
|
per thread. The mitigation control state
|
|
is inherited on fork.
|
|
|
|
prctl,ibpb
|
|
- Like "prctl" above, but only STIBP is
|
|
controlled per thread. IBPB is issued
|
|
always when switching between different user
|
|
space processes.
|
|
|
|
seccomp
|
|
- Same as "prctl" above, but all seccomp
|
|
threads will enable the mitigation unless
|
|
they explicitly opt out.
|
|
|
|
seccomp,ibpb
|
|
- Like "seccomp" above, but only STIBP is
|
|
controlled per thread. IBPB is issued
|
|
always when switching between different
|
|
user space processes.
|
|
|
|
auto - Kernel selects the mitigation depending on
|
|
the available CPU features and vulnerability.
|
|
|
|
Default mitigation:
|
|
If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
|
|
|
|
Not specifying this option is equivalent to
|
|
spectre_v2_user=auto.
|
|
|
|
spec_store_bypass_disable=
|
|
[HW] Control Speculative Store Bypass (SSB) Disable mitigation
|
|
(Speculative Store Bypass vulnerability)
|
|
|
|
Certain CPUs are vulnerable to an exploit against a
|
|
a common industry wide performance optimization known
|
|
as "Speculative Store Bypass" in which recent stores
|
|
to the same memory location may not be observed by
|
|
later loads during speculative execution. The idea
|
|
is that such stores are unlikely and that they can
|
|
be detected prior to instruction retirement at the
|
|
end of a particular speculation execution window.
|
|
|
|
In vulnerable processors, the speculatively forwarded
|
|
store can be used in a cache side channel attack, for
|
|
example to read memory to which the attacker does not
|
|
directly have access (e.g. inside sandboxed code).
|
|
|
|
This parameter controls whether the Speculative Store
|
|
Bypass optimization is used.
|
|
|
|
On x86 the options are:
|
|
|
|
on - Unconditionally disable Speculative Store Bypass
|
|
off - Unconditionally enable Speculative Store Bypass
|
|
auto - Kernel detects whether the CPU model contains an
|
|
implementation of Speculative Store Bypass and
|
|
picks the most appropriate mitigation. If the
|
|
CPU is not vulnerable, "off" is selected. If the
|
|
CPU is vulnerable the default mitigation is
|
|
architecture and Kconfig dependent. See below.
|
|
prctl - Control Speculative Store Bypass per thread
|
|
via prctl. Speculative Store Bypass is enabled
|
|
for a process by default. The state of the control
|
|
is inherited on fork.
|
|
seccomp - Same as "prctl" above, but all seccomp threads
|
|
will disable SSB unless they explicitly opt out.
|
|
|
|
Default mitigations:
|
|
X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
|
|
|
|
On powerpc the options are:
|
|
|
|
on,auto - On Power8 and Power9 insert a store-forwarding
|
|
barrier on kernel entry and exit. On Power7
|
|
perform a software flush on kernel entry and
|
|
exit.
|
|
off - No action.
|
|
|
|
Not specifying this option is equivalent to
|
|
spec_store_bypass_disable=auto.
|
|
|
|
spia_io_base= [HW,MTD]
|
|
spia_fio_base=
|
|
spia_pedr=
|
|
spia_peddr=
|
|
|
|
srcutree.counter_wrap_check [KNL]
|
|
Specifies how frequently to check for
|
|
grace-period sequence counter wrap for the
|
|
srcu_data structure's ->srcu_gp_seq_needed field.
|
|
The greater the number of bits set in this kernel
|
|
parameter, the less frequently counter wrap will
|
|
be checked for. Note that the bottom two bits
|
|
are ignored.
|
|
|
|
srcutree.exp_holdoff [KNL]
|
|
Specifies how many nanoseconds must elapse
|
|
since the end of the last SRCU grace period for
|
|
a given srcu_struct until the next normal SRCU
|
|
grace period will be considered for automatic
|
|
expediting. Set to zero to disable automatic
|
|
expediting.
|
|
|
|
ssbd= [ARM64,HW]
|
|
Speculative Store Bypass Disable control
|
|
|
|
On CPUs that are vulnerable to the Speculative
|
|
Store Bypass vulnerability and offer a
|
|
firmware based mitigation, this parameter
|
|
indicates how the mitigation should be used:
|
|
|
|
force-on: Unconditionally enable mitigation for
|
|
for both kernel and userspace
|
|
force-off: Unconditionally disable mitigation for
|
|
for both kernel and userspace
|
|
kernel: Always enable mitigation in the
|
|
kernel, and offer a prctl interface
|
|
to allow userspace to register its
|
|
interest in being mitigated too.
|
|
|
|
stack_guard_gap= [MM]
|
|
override the default stack gap protection. The value
|
|
is in page units and it defines how many pages prior
|
|
to (for stacks growing down) resp. after (for stacks
|
|
growing up) the main stack are reserved for no other
|
|
mapping. Default value is 256 pages.
|
|
|
|
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
|
|
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
|
|
and the stacktrace above is not needed.
|
|
|
|
sti= [PARISC,HW]
|
|
Format: <num>
|
|
Set the STI (builtin display/keyboard on the HP-PARISC
|
|
machines) console (graphic card) which should be used
|
|
as the initial boot-console.
|
|
See also comment in drivers/video/console/sticore.c.
|
|
|
|
sti_font= [HW]
|
|
See comment in drivers/video/console/sticore.c.
|
|
|
|
stifb= [HW]
|
|
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
|
|
|
|
sunrpc.min_resvport=
|
|
sunrpc.max_resvport=
|
|
[NFS,SUNRPC]
|
|
SunRPC servers often require that client requests
|
|
originate from a privileged port (i.e. a port in the
|
|
range 0 < portnr < 1024).
|
|
An administrator who wishes to reserve some of these
|
|
ports for other uses may adjust the range that the
|
|
kernel's sunrpc client considers to be privileged
|
|
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
|
|
service thread pools. Depending on how many NICs
|
|
you have and where their interrupts are bound, this
|
|
option will affect which CPUs will do NFS serving.
|
|
Note: this parameter cannot be changed while the
|
|
NFS server is running.
|
|
|
|
auto the server chooses an appropriate mode
|
|
automatically using heuristics
|
|
global a single global pool contains all CPUs
|
|
percpu one pool for each CPU
|
|
pernode one pool for each NUMA node (equivalent
|
|
to global on non-NUMA machines)
|
|
|
|
sunrpc.tcp_slot_table_entries=
|
|
sunrpc.udp_slot_table_entries=
|
|
[NFS,SUNRPC]
|
|
Sets the upper limit on the number of simultaneous
|
|
RPC calls that can be sent from the client to a
|
|
server. Increasing these values may allow you to
|
|
improve throughput, but will also increase the
|
|
amount of memory reserved for use by the client.
|
|
|
|
suspend.pm_test_delay=
|
|
[SUSPEND]
|
|
Sets the number of seconds to remain in a suspend test
|
|
mode before resuming the system (see
|
|
/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
|
|
is set. Default value is 5.
|
|
|
|
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/cgroup-v1/memory.txt)
|
|
|
|
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
|
|
Format: { <int> | force | noforce }
|
|
<int> -- Number of I/O TLB slabs
|
|
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.
|
|
|
|
sysrq_always_enabled
|
|
[KNL]
|
|
Ignore sysrq setting - this boot parameter will
|
|
neutralize any effect of /proc/sys/kernel/sysrq.
|
|
Useful for debugging.
|
|
|
|
tcpmhash_entries= [KNL,NET]
|
|
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
|
|
"tcp_no_metrics_save" section for more details.
|
|
|
|
tdfx= [HW,DRM]
|
|
|
|
test_suspend= [SUSPEND][,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
|
|
the optional capability to repeat N number of times.
|
|
The system is woken from this state using a
|
|
wakeup-capable RTC alarm.
|
|
|
|
thash_entries= [KNL,NET]
|
|
Set number of hash buckets for TCP connection
|
|
|
|
thermal.act= [HW,ACPI]
|
|
-1: disable all active trip points in all thermal zones
|
|
<degrees C>: override all lowest active trip points
|
|
|
|
thermal.crt= [HW,ACPI]
|
|
-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
|
|
|
|
thermal.psv= [HW,ACPI]
|
|
-1: disable all passive trip points
|
|
<degrees C>: override all passive trip points to this
|
|
value
|
|
|
|
thermal.tzp= [HW,ACPI]
|
|
Specify global default ACPI thermal zone polling rate
|
|
<deci-seconds>: poll all this frequency
|
|
0: no polling (default)
|
|
|
|
threadirqs [KNL]
|
|
Force threading of all interrupt handlers except those
|
|
marked explicitly IRQF_NO_THREAD.
|
|
|
|
tmem [KNL,XEN]
|
|
Enable the Transcendent memory driver if built-in.
|
|
|
|
tmem.cleancache=0|1 [KNL, XEN]
|
|
Default is on (1). Disable the usage of the cleancache
|
|
API to send anonymous pages to the hypervisor.
|
|
|
|
tmem.frontswap=0|1 [KNL, XEN]
|
|
Default is on (1). Disable the usage of the frontswap
|
|
API to send swap pages to the hypervisor. If disabled
|
|
the selfballooning and selfshrinking are force disabled.
|
|
|
|
tmem.selfballooning=0|1 [KNL, XEN]
|
|
Default is on (1). Disable the driving of swap pages
|
|
to the hypervisor.
|
|
|
|
tmem.selfshrinking=0|1 [KNL, XEN]
|
|
Default is on (1). Partial swapoff that immediately
|
|
transfers pages from Xen hypervisor back to the
|
|
kernel based on different criteria.
|
|
|
|
topology= [S390]
|
|
Format: {off | on}
|
|
Specify if the kernel should make use of the cpu
|
|
topology information if the hardware supports this.
|
|
The scheduler will make use of this information and
|
|
e.g. base its process migration decisions on it.
|
|
Default is on.
|
|
|
|
topology_updates= [KNL, PPC, NUMA]
|
|
Format: {off}
|
|
Specify if the kernel should ignore (off)
|
|
topology updates sent by the hypervisor to this
|
|
LPAR.
|
|
|
|
tp720= [HW,PS2]
|
|
|
|
tpm_suspend_pcr=[HW,TPM]
|
|
Format: integer pcr id
|
|
Specify that at suspend time, the tpm driver
|
|
should extend the specified pcr with zeros,
|
|
as a workaround for some chips which fail to
|
|
flush the last written pcr on TPM_SaveState.
|
|
This will guarantee that all the other pcrs
|
|
are saved.
|
|
|
|
trace_buf_size=nn[KMG]
|
|
[FTRACE] will set tracing buffer size on each cpu.
|
|
|
|
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
|
|
also Documentation/trace/events.rst
|
|
|
|
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
|
|
|
|
For example, to enable stacktrace option (to dump the
|
|
stack trace of each event), add to the command line:
|
|
|
|
trace_options=stacktrace
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
** CAUTION **
|
|
|
|
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/
|
|
|
|
This option is useful, as it disables the trace before
|
|
the WARNING dump is called, which prevents the trace to
|
|
be filled with content caused by the warning output.
|
|
|
|
This option can also be set at run time via the sysctl
|
|
option: kernel/traceoff_on_warning
|
|
|
|
transparent_hugepage=
|
|
[KNL]
|
|
Format: [always|madvise|never]
|
|
Can be used to control the default behavior of the system
|
|
with respect to transparent hugepages.
|
|
See Documentation/admin-guide/mm/transhuge.rst
|
|
for more details.
|
|
|
|
tsc= Disable clocksource stability checks for TSC.
|
|
Format: <string>
|
|
[x86] reliable: mark tsc clocksource as reliable, this
|
|
disables clocksource verification at runtime, as well
|
|
as the stability checks done at bootup. Used to enable
|
|
high-resolution timer mode on older hardware, and in
|
|
virtualized environment.
|
|
[x86] noirqtime: Do not use TSC to do irq accounting.
|
|
Used to run time disable IRQ_TIME_ACCOUNTING on any
|
|
platforms where RDTSC is slow and this accounting
|
|
can add overhead.
|
|
[x86] unstable: mark the TSC clocksource as unstable, this
|
|
marks the TSC unconditionally unstable at bootup and
|
|
avoids any further wobbles once the TSC watchdog notices.
|
|
[x86] nowatchdog: disable clocksource watchdog. Used
|
|
in situations with strict latency requirements (where
|
|
interruptions from clocksource watchdog are not
|
|
acceptable).
|
|
|
|
turbografx.map[2|3]= [HW,JOY]
|
|
TurboGraFX parallel port interface
|
|
Format:
|
|
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
|
|
See also Documentation/input/devices/joystick-parport.rst
|
|
|
|
udbg-immortal [PPC] When debugging early kernel crashes that
|
|
happen after console_init() and before a proper
|
|
console driver takes over, this boot options might
|
|
help "seeing" what's going on.
|
|
|
|
uhash_entries= [KNL,NET]
|
|
Set number of hash buckets for UDP/UDP-Lite connections
|
|
|
|
uhci-hcd.ignore_oc=
|
|
[USB] Ignore overcurrent events (default N).
|
|
Some badly-designed motherboards generate lots of
|
|
bogus events, for ports that aren't wired to
|
|
anything. Set this parameter to avoid log spamming.
|
|
Note that genuine overcurrent events won't be
|
|
reported either.
|
|
|
|
unknown_nmi_panic
|
|
[X86] Cause panic on unknown NMI.
|
|
|
|
usbcore.authorized_default=
|
|
[USB] Default USB device authorization:
|
|
(default -1 = authorized except for wireless USB,
|
|
0 = not authorized, 1 = authorized, 2 = authorized
|
|
if device connected to internal port)
|
|
|
|
usbcore.autosuspend=
|
|
[USB] The autosuspend time delay (in seconds) used
|
|
for newly-detected USB devices (default 2). This
|
|
is the time required before an idle device will be
|
|
autosuspended. Devices for which the delay is set
|
|
to a negative value won't be autosuspended at all.
|
|
|
|
usbcore.usbfs_snoop=
|
|
[USB] Set to log all usbfs traffic (default 0 = off).
|
|
|
|
usbcore.usbfs_snoop_max=
|
|
[USB] Maximum number of bytes to snoop in each URB
|
|
(default = 65536).
|
|
|
|
usbcore.blinkenlights=
|
|
[USB] Set to cycle leds on hubs (default 0 = off).
|
|
|
|
usbcore.old_scheme_first=
|
|
[USB] Start with the old device initialization
|
|
scheme, applies only to low and full-speed devices
|
|
(default 0 = off).
|
|
|
|
usbcore.usbfs_memory_mb=
|
|
[USB] Memory limit (in MB) for buffers allocated by
|
|
usbfs (default = 16, 0 = max = 2047).
|
|
|
|
usbcore.use_both_schemes=
|
|
[USB] Try the other device initialization scheme
|
|
if the first one fails (default 1 = enabled).
|
|
|
|
usbcore.initial_descriptor_timeout=
|
|
[USB] Specifies timeout for the initial 64-byte
|
|
USB_REQ_GET_DESCRIPTOR request in milliseconds
|
|
(default 5000 = 5.0 seconds).
|
|
|
|
usbcore.nousb [USB] Disable the USB subsystem
|
|
|
|
usbcore.quirks=
|
|
[USB] A list of quirk entries to augment the built-in
|
|
usb core quirk list. List entries are separated by
|
|
commas. Each entry has the form
|
|
VendorID:ProductID:Flags. The IDs are 4-digit hex
|
|
numbers and Flags is a set of letters. Each letter
|
|
will change the built-in quirk; setting it if it is
|
|
clear and clearing it if it is set. The letters have
|
|
the following meanings:
|
|
a = USB_QUIRK_STRING_FETCH_255 (string
|
|
descriptors must not be fetched using
|
|
a 255-byte read);
|
|
b = USB_QUIRK_RESET_RESUME (device can't resume
|
|
correctly so reset it instead);
|
|
c = USB_QUIRK_NO_SET_INTF (device can't handle
|
|
Set-Interface requests);
|
|
d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
|
|
handle its Configuration or Interface
|
|
strings);
|
|
e = USB_QUIRK_RESET (device can't be reset
|
|
(e.g morph devices), don't use reset);
|
|
f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
|
|
more interface descriptions than the
|
|
bNumInterfaces count, and can't handle
|
|
talking to these interfaces);
|
|
g = USB_QUIRK_DELAY_INIT (device needs a pause
|
|
during initialization, after we read
|
|
the device descriptor);
|
|
h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
|
|
high speed and super speed interrupt
|
|
endpoints, the USB 2.0 and USB 3.0 spec
|
|
require the interval in microframes (1
|
|
microframe = 125 microseconds) to be
|
|
calculated as interval = 2 ^
|
|
(bInterval-1).
|
|
Devices with this quirk report their
|
|
bInterval as the result of this
|
|
calculation instead of the exponent
|
|
variable used in the calculation);
|
|
i = USB_QUIRK_DEVICE_QUALIFIER (device can't
|
|
handle device_qualifier descriptor
|
|
requests);
|
|
j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
|
|
generates spurious wakeup, ignore
|
|
remote wakeup capability);
|
|
k = USB_QUIRK_NO_LPM (device can't handle Link
|
|
Power Management);
|
|
l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
|
|
(Device reports its bInterval as linear
|
|
frames instead of the USB 2.0
|
|
calculation);
|
|
m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
|
|
to be disconnected before suspend to
|
|
prevent spurious wakeup);
|
|
n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
|
|
pause after every control message);
|
|
o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
|
|
delay after resetting its port);
|
|
Example: quirks=0781:5580:bk,0a5c:5834:gij
|
|
|
|
usbhid.mousepoll=
|
|
[USBHID] The interval which mice are to be polled at.
|
|
|
|
usbhid.jspoll=
|
|
[USBHID] The interval which joysticks are to be polled at.
|
|
|
|
usbhid.kbpoll=
|
|
[USBHID] The interval which keyboards are to be polled at.
|
|
|
|
usb-storage.delay_use=
|
|
[UMS] The delay in seconds before a new device is
|
|
scanned for Logical Units (default 1).
|
|
|
|
usb-storage.quirks=
|
|
[UMS] A list of quirks entries to supplement or
|
|
override the built-in unusual_devs list. List
|
|
entries are separated by commas. Each entry has
|
|
the form VID:PID:Flags where VID and PID are Vendor
|
|
and Product ID values (4-digit hex numbers) and
|
|
Flags is a set of characters, each corresponding
|
|
to a common usb-storage quirk flag as follows:
|
|
a = SANE_SENSE (collect more than 18 bytes
|
|
of sense data);
|
|
b = BAD_SENSE (don't collect more than 18
|
|
bytes of sense data);
|
|
c = FIX_CAPACITY (decrease the reported
|
|
device capacity by one sector);
|
|
d = NO_READ_DISC_INFO (don't use
|
|
READ_DISC_INFO command);
|
|
e = NO_READ_CAPACITY_16 (don't use
|
|
READ_CAPACITY_16 command);
|
|
f = NO_REPORT_OPCODES (don't use report opcodes
|
|
command, uas only);
|
|
g = MAX_SECTORS_240 (don't transfer more than
|
|
240 sectors at a time, uas only);
|
|
h = CAPACITY_HEURISTICS (decrease the
|
|
reported device capacity by one
|
|
sector if the number is odd);
|
|
i = IGNORE_DEVICE (don't bind to this
|
|
device);
|
|
j = NO_REPORT_LUNS (don't use report luns
|
|
command, uas only);
|
|
l = NOT_LOCKABLE (don't try to lock and
|
|
unlock ejectable media);
|
|
m = MAX_SECTORS_64 (don't transfer more
|
|
than 64 sectors = 32 KB at a time);
|
|
n = INITIAL_READ10 (force a retry of the
|
|
initial READ(10) command);
|
|
o = CAPACITY_OK (accept the capacity
|
|
reported by the device);
|
|
p = WRITE_CACHE (the device cache is ON
|
|
by default);
|
|
r = IGNORE_RESIDUE (the device reports
|
|
bogus residue values);
|
|
s = SINGLE_LUN (the device has only one
|
|
Logical Unit);
|
|
t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
|
|
commands, uas only);
|
|
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]
|
|
Format: <int>
|
|
See arch/arm/Kconfig.debug help text.
|
|
1 - undefined instruction events
|
|
2 - system calls
|
|
4 - invalid data aborts
|
|
8 - SIGSEGV faults
|
|
16 - SIGBUS faults
|
|
Example: user_debug=31
|
|
|
|
userpte=
|
|
[X86] Flags controlling user PTE allocations.
|
|
|
|
nohigh = do not allocate PTE pages in
|
|
HIGHMEM regardless of setting
|
|
of CONFIG_HIGHPTE.
|
|
|
|
vdso= [X86,SH]
|
|
On X86_32, this is an alias for vdso32=. Otherwise:
|
|
|
|
vdso=1: enable VDSO (the default)
|
|
vdso=0: disable VDSO mapping
|
|
|
|
vdso32= [X86] Control the 32-bit vDSO
|
|
vdso32=1: enable 32-bit VDSO
|
|
vdso32=0 or vdso32=2: disable 32-bit VDSO
|
|
|
|
See the help text for CONFIG_COMPAT_VDSO for more
|
|
details. If CONFIG_COMPAT_VDSO is set, the default is
|
|
vdso32=0; otherwise, the default is vdso32=1.
|
|
|
|
For compatibility with older kernels, vdso32=2 is an
|
|
alias for vdso32=0.
|
|
|
|
Try vdso32=0 if you encounter an error that says:
|
|
dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
|
|
|
|
vector= [IA-64,SMP]
|
|
vector=percpu: enable percpu vector domain
|
|
|
|
video= [FB] Frame buffer configuration
|
|
See Documentation/fb/modedb.txt.
|
|
|
|
video.brightness_switch_enabled= [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
|
|
will only send out the event without touching backlight
|
|
brightness level.
|
|
default: 1
|
|
|
|
virtio_mmio.device=
|
|
[VMMIO] Memory mapped virtio (platform) device.
|
|
|
|
<size>@<baseaddr>:<irq>[:<id>]
|
|
where:
|
|
<size> := size (can use standard suffixes
|
|
like K, M and G)
|
|
<baseaddr> := physical base address
|
|
<irq> := interrupt number (as passed to
|
|
request_irq())
|
|
<id> := (optional) platform device id
|
|
example:
|
|
virtio_mmio.device=1K@0x100b0000:48:7
|
|
|
|
Can be used multiple times for multiple devices.
|
|
|
|
vga= [BOOT,X86-32] Select a particular video mode
|
|
See Documentation/x86/boot.txt and
|
|
Documentation/svga.txt.
|
|
Use vga=ask for menu.
|
|
This is actually a boot loader parameter; the value is
|
|
passed to the kernel using a special protocol.
|
|
|
|
vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
|
|
May slow down system boot speed, especially when
|
|
enabled on systems with a large amount of memory.
|
|
All options are enabled by default, and this
|
|
interface is meant to allow for selectively
|
|
enabling or disabling specific virtual memory
|
|
debugging features.
|
|
|
|
Available options are:
|
|
P Enable page structure init time poisoning
|
|
- Disable all of the above options
|
|
|
|
vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
|
|
size of <nn>. This can be used to increase the
|
|
minimum size (128MB on x86). It can also be used to
|
|
decrease the size and leave more room for directly
|
|
mapped kernel RAM.
|
|
|
|
vmcp_cma=nn[MG] [KNL,S390]
|
|
Sets the memory size reserved for contiguous memory
|
|
allocations for the vmcp device driver.
|
|
|
|
vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
|
|
Format: <command>
|
|
|
|
vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
|
|
Format: <command>
|
|
|
|
vmpoff= [KNL,S390] Perform z/VM CP command after power off.
|
|
Format: <command>
|
|
|
|
vsyscall= [X86-64]
|
|
Controls the behavior of vsyscalls (i.e. calls to
|
|
fixed addresses of 0xffffffffff600x00 from legacy
|
|
code). Most statically-linked binaries and older
|
|
versions of glibc use these calls. Because these
|
|
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.
|
|
|
|
xonly Vsyscalls turn into traps and are
|
|
emulated reasonably safely. The vsyscall
|
|
page is not readable.
|
|
|
|
none Vsyscalls don't work at all. This makes
|
|
them quite hard to use for exploits but
|
|
might break your system.
|
|
|
|
vt.color= [VT] Default text color.
|
|
Format: 0xYX, X = foreground, Y = background.
|
|
Default: 0x07 = light gray on black.
|
|
|
|
vt.cur_default= [VT] Default cursor shape.
|
|
Format: 0xCCBBAA, where AA, BB, and CC are the same as
|
|
the parameters of the <Esc>[?A;B;Cc escape sequence;
|
|
see VGA-softcursor.txt. Default: 2 = underline.
|
|
|
|
vt.default_blu= [VT]
|
|
Format: <blue0>,<blue1>,<blue2>,...,<blue15>
|
|
Change the default blue palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_grn= [VT]
|
|
Format: <green0>,<green1>,<green2>,...,<green15>
|
|
Change the default green palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_red= [VT]
|
|
Format: <red0>,<red1>,<red2>,...,<red15>
|
|
Change the default red palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_utf8=
|
|
[VT]
|
|
Format=<0|1>
|
|
Set system-wide default UTF-8 mode for all tty's.
|
|
Default is 1, i.e. UTF-8 mode is enabled for all
|
|
newly opened terminals.
|
|
|
|
vt.global_cursor_default=
|
|
[VT]
|
|
Format=<-1|0|1>
|
|
Set system-wide default for whether a cursor
|
|
is shown on new VTs. Default is -1,
|
|
i.e. cursors will be created by default unless
|
|
overridden by individual drivers. 0 will hide
|
|
cursors, 1 will display them.
|
|
|
|
vt.italic= [VT] Default color for italic text; 0-15.
|
|
Default: 2 = green.
|
|
|
|
vt.underline= [VT] Default color for underlined text; 0-15.
|
|
Default: 3 = cyan.
|
|
|
|
watchdog timers [HW,WDT] For information on watchdog timers,
|
|
see Documentation/watchdog/watchdog-parameters.txt
|
|
or other driver-specific files in the
|
|
Documentation/watchdog/ directory.
|
|
|
|
watchdog_thresh=
|
|
[KNL]
|
|
Set the hard lockup detector stall duration
|
|
threshold in seconds. The soft lockup detector
|
|
threshold is set to twice the value. A value of 0
|
|
disables both lockup detectors. Default is 10
|
|
seconds.
|
|
|
|
workqueue.watchdog_thresh=
|
|
If CONFIG_WQ_WATCHDOG is configured, workqueue can
|
|
warn stall conditions and dump internal state to
|
|
help debugging. 0 disables workqueue stall
|
|
detection; otherwise, it's the stall threshold
|
|
duration in seconds. The default value is 30 and
|
|
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.power_efficient
|
|
Per-cpu workqueues are generally preferred because
|
|
they show better performance thanks to cache
|
|
locality; unfortunately, per-cpu workqueues tend to
|
|
be more power hungry than unbound workqueues.
|
|
|
|
Enabling this makes the per-cpu workqueues which
|
|
were observed to contribute significantly to power
|
|
consumption unbound, leading to measurably lower
|
|
power usage at the cost of small performance
|
|
overhead.
|
|
|
|
The default value of this parameter is determined by
|
|
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
|
|
|
|
workqueue.debug_force_rr_cpu
|
|
Workqueue used to implicitly guarantee that work
|
|
items queued without explicit CPU specified are put
|
|
on the local CPU. This guarantee is no longer true
|
|
and while local CPU is still preferred work items
|
|
may be put on foreign CPUs. This debug option
|
|
forces round-robin CPU selection to flush out
|
|
usages which depend on the now broken guarantee.
|
|
When enabled, memory and cache locality will be
|
|
impacted.
|
|
|
|
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
|
|
crash analysis tools and Xen tools for doing domain
|
|
save/restore/migration must be enabled to handle larger
|
|
domains.
|
|
|
|
xen_emul_unplug= [HW,X86,XEN]
|
|
Unplug Xen emulated devices
|
|
Format: [unplug0,][unplug1]
|
|
ide-disks -- unplug primary master IDE devices
|
|
aux-ide-disks -- unplug non-primary-master IDE devices
|
|
nics -- unplug network devices
|
|
all -- unplug all emulated devices (NICs and IDE disks)
|
|
unnecessary -- unplugging emulated devices is
|
|
unnecessary even if the host did not respond to
|
|
the unplug protocol
|
|
never -- do not unplug even if version check succeeds
|
|
|
|
xen_nopvspin [X86,XEN]
|
|
Disables the ticketlock slowpath using Xen PV
|
|
optimizations.
|
|
|
|
xen_nopv [X86]
|
|
Disables the PV optimizations forcing the HVM guest to
|
|
run as generic HVM guest with no PV drivers.
|
|
|
|
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
|
|
with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
|
|
Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
|
|
|
|
xen_timer_slop= [X86-64,XEN]
|
|
Set the timer slop (in nanoseconds) for the virtual Xen
|
|
timers (default is 100000). This adjusts the minimum
|
|
delta of virtualized Xen timers, where lower values
|
|
improve timer resolution at the expense of processing
|
|
more timer interrupts.
|
|
|
|
xirc2ps_cs= [NET,PCMCIA]
|
|
Format:
|
|
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
|
|
|
|
xhci-hcd.quirks [USB,KNL]
|
|
A hex value specifying bitmask with supplemental xhci
|
|
host controller quirks. Meaning of each bit can be
|
|
consulted in header drivers/usb/host/xhci.h.
|