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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_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_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:

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).

[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
the default is off.

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] Trap guest accesses to GICv3 group-0
system registers

[KVM,ARM] Trap guest accesses to GICv3 group-1
system registers

[KVM,ARM] Trap guest accesses to GICv3 common
system registers

[KVM,ARM] Allow use of GICv4 for direct injection of

kvm-intel.ept= [KVM,Intel] Disable extended page tables
(virtualized MMU) support on capable Intel chips.
Default is 1 (enabled)

[KVM,Intel] Enable emulation of invalid guest states
Default is 0 (disabled)

[KVM,Intel] Disable FlexPriority feature (TPR shadow).
Default is 1 (enabled)

[KVM,Intel] Enable VMX nesting (nVMX).
Default is 0 (disabled)

[KVM,Intel] Disable unrestricted guest feature
(virtualized real and unpaged mode) on capable
Intel chips. Default is 1 (enabled)

kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
feature (tagged TLBs) on capable Intel chips.
Default is 1 (enabled)

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

* [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

ltpc= [NET]
Format: <io>,<irq>,<dma>

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.

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

[KNL,SH] Allow user to override the default size for
per-device physically contiguous DMA buffers.

[KNL] Set the initial state for the memory hotplug
onlining policy. If not specified, the default value is
set according to the
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.

[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.

[KNL,ACPI] Mark specific memory as ACPI data.
Region of memory to be marked is from ss to ss+nn.

[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
Some bootloaders may need an escape character before '$',
like Grub2, otherwise '$' and the following number
will be eaten.

[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.

[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] 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.