causing system reset or hang due to sending
INIT from AP to BSP.
+++ disable_counter_freezing [HW]
+++ 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.
earlyprintk=serial[,0x...[,baudrate]]
earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#]
- -- earlyprintk=pciserial,bus:device.function[,baudrate]
+ ++ earlyprintk=pciserial[,force],bus:device.function[,baudrate]
earlyprintk=xdbc[xhciController#]
earlyprintk is useful when the kernel crashes before
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
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
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 IOMMU translation 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
ltpc= [NET]
Format: <io>,<irq>,<dma>
+++ lsm.debug [SECURITY] Enable LSM initialization debugging output.
+++
machvec= [IA-64] Force the use of a particular machine-vector
(machvec) in a generic kernel.
Example: machvec=hpzx1_swiotlb
seconds. Use this parameter to check at some
other rate. 0 disables periodic checking.
--- memtest= [KNL,X86,ARM] Enable memtest
+++ memtest= [KNL,X86,ARM,PPC] Enable memtest
Format: <integer>
default : 0 <disable>
Specifies the number of memtest passes to be
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]
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.
+++ 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
Set required age in jiffies for a
given grace period before RCU starts
soliciting quiescent-state help from
--- rcu_note_context_switch().
+++ rcu_note_context_switch(). 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.jiffies_till_first_fqs= [KNL]
Set delay from grace-period initialization to
rcupdate.rcu_self_test= [KNL]
Run the RCU early boot self tests
--- rcupdate.rcu_self_test_bh= [KNL]
--- Run the RCU bh early boot self tests
---
--- rcupdate.rcu_self_test_sched= [KNL]
--- Run the RCU sched early boot self tests
---
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,
usbcore.old_scheme_first=
[USB] Start with the old device initialization
--- scheme (default 0 = off).
+++ 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
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
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.
++
xirc2ps_cs= [NET,PCMCIA]
Format:
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]