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pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
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

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

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 }

[ISAPNP] Exclude IRQs for the autoconfiguration

[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).

[ISAPNP] Exclude memory regions for the
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] 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

[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.

Trigger kmsg_dump for cases other than kernel oops or
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
default: disabled

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).
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.

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).
[HW,MOUSE] Set desired mouse resolution, in dpi.
[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

[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.

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.

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 "b" for RCU-bh, "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.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_sched_qs= [KNL]
Set required age in jiffies for a
given grace period before RCU starts
soliciting quiescent-state help from

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.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().

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

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

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.cbflood_inter_holdoff= [KNL]
Set holdoff time (jiffies) between successive
callback-flood tests.

rcutorture.cbflood_intra_holdoff= [KNL]
Set holdoff time (jiffies) between successive
bursts of callbacks within a given callback-flood

rcutorture.cbflood_n_burst= [KNL]
Set the number of bursts making up a given
callback-flood test. Set this to zero to
disable callback-flood testing.

rcutorture.cbflood_n_per_burst= [KNL]
Set the number of callbacks to be registered
in a given burst of a callback-flood test.

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.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 (s) 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.