Kernel Parameters
~~~~~~~~~~~~~~~~~
-The following is a consolidated list of the kernel parameters as implemented
-(mostly) by the __setup() macro and sorted into English Dictionary order
-(defined as ignoring all punctuation and sorting digits before letters in a
-case insensitive manner), and with descriptions where known.
-
-Module parameters for loadable modules are specified only as the
-parameter name with optional '=' and value as appropriate, such as:
-
- modprobe usbcore blinkenlights=1
-
-Module parameters for modules that are built into the kernel image
-are specified on the kernel command line with the module name plus
-'.' plus parameter name, with '=' and value if appropriate, such as:
-
- usbcore.blinkenlights=1
+The following is a consolidated list of the kernel parameters as
+implemented by the __setup(), core_param() and module_param() macros
+and sorted into English Dictionary order (defined as ignoring all
+punctuation and sorting digits before letters in a case insensitive
+manner), and with descriptions where known.
+
+The kernel parses parameters from the kernel command line up to "--";
+if it doesn't recognize a parameter and it doesn't contain a '.', the
+parameter gets passed to init: parameters with '=' go into init's
+environment, others are passed as command line arguments to init.
+Everything after "--" is passed as an argument to init.
+
+Module parameters can be specified in two ways: via the kernel command
+line with a module name prefix, or via modprobe, e.g.:
+
+ (kernel command line) usbcore.blinkenlights=1
+ (modprobe command line) modprobe usbcore blinkenlights=1
+
+Parameters for modules which are built into the kernel need to be
+specified on the kernel command line. modprobe looks through the
+kernel command line (/proc/cmdline) and collects module parameters
+when it loads a module, so the kernel command line can be used for
+loadable modules too.
Hyphens (dashes) and underscores are equivalent in parameter names, so
log_buf_len=1M print-fatal-signals=1
can also be entered as
log-buf-len=1M print_fatal_signals=1
+Double-quotes can be used to protect spaces in values, e.g.:
+ param="spaces in here"
This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
unusable. The "log_buf_len" parameter may be useful
if you need to capture more output.
+ acpi_force_table_verification [HW,ACPI]
+ Enable table checksum verification during early stage.
+ By default, this is disabled due to x86 early mapping
+ size limitation.
+
acpi_irq_balance [HW,ACPI]
ACPI will balance active IRQs
default in APIC mode
This feature is enabled by default.
This option allows to turn off the feature.
- acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
+ acpi_no_static_ssdt [HW,ACPI]
+ Disable installation of static SSDTs at early boot time
+ By default, SSDTs contained in the RSDT/XSDT will be
+ installed automatically and they will appear under
+ /sys/firmware/acpi/tables.
+ This option turns off this feature.
+ Note that specifying this option does not affect
+ dynamic table installation which will install SSDT
+ tables to /sys/firmware/acpi/tables/dynamic.
acpica_no_return_repair [HW, ACPI]
Disable AML predefined validation mechanism
possible to determine what the correct size should be.
This option provides an override for these situations.
+ 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/CommonIO for details.
Also note the kernel might malfunction if you disable
some critical bits.
- cma=nn[MG] [ARM,KNL]
- Sets the size of kernel global memory area for contiguous
+ 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. For more information, see
include/linux/dma-contiguous.h
which are not unmapped.
earlycon= [KNL] Output early console device and options.
+
uart[8250],io,<addr>[,options]
uart[8250],mmio,<addr>[,options]
uart[8250],mmio32,<addr>[,options]
(mmio) or 32-bit (mmio32).
The options are the same as for ttyS, above.
- earlyprintk= [X86,SH,BLACKFIN,ARM]
+ pl011,<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.
+
+ smh Use ARM semihosting calls for early console.
+
+ earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
earlyprintk=vga
earlyprintk=efi
earlyprintk=xen
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.
+
gamecon.map[2|3]=
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
support via parallel port (up to 5 devices per port)
Formats: { "ima" | "ima-ng" }
Default: "ima-ng"
+ 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
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
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
ip= [IP_PNP]
See Documentation/filesystems/nfs/nfsroot.txt.
- ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
- See comment before ip2_setup() in
- drivers/char/ip2/ip2base.c.
-
irqfixup [HW]
When an interrupt is not handled search all handlers
for it. Intended to get systems with badly broken
js= [HW,JOY] Analog joystick
See Documentation/input/joystick.txt.
+ kaslr/nokaslr [X86]
+ Enable/disable kernel and module base offset ASLR
+ (Address Space Layout Randomization) if built into
+ the kernel. When CONFIG_HIBERNATION is selected,
+ kASLR is disabled by default. When kASLR is enabled,
+ hibernation will be disabled.
+
keepinitrd [HW,ARM]
kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
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. The default
- size is set in the kernel config file.
+ 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
noapic [SMP,APIC] Tells the kernel to not make use of any
IOAPICs that may be present in the system.
- nokaslr [X86]
- Disable kernel and module base offset ASLR (Address
- Space Layout Randomization) if built into the kernel.
-
noautogroup Disable scheduler automatic task group creation.
nobats [PPC] Do not use BATs for mapping kernel lowmem
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.
+
eagerfpu= [X86]
on enable eager fpu restore
off disable eager fpu restore
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
timeout < 0: reboot immediately
Format: <timeout>
+ 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#>
leaf rcu_node structure. Useful for very large
systems.
+ 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().
+
rcutree.jiffies_till_first_fqs= [KNL]
Set delay from grace-period initialization to
first attempt to force quiescent states.
quiescent states. Units are jiffies, minimum
value is one, and maximum value is HZ.
+ 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.
[KNL, SMP] Set scheduler's default relax_domain_level.
See Documentation/cgroups/cpusets.txt.
+ relative_sleep_states=
+ [SUSPEND] Use sleep state labeling where the deepest
+ state available other than hibernation is always "mem".
+ Format: { "0" | "1" }
+ 0 -- Traditional sleep state labels.
+ 1 -- Relative sleep state labels.
+
reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
reservetop= [X86-32]
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.
retain_initrd [RAM] Keep initrd memory after extraction
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.
[KNL] Should the soft-lockup detector generate panics.
Format: <integer>
+ 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
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.
+
xirc2ps_cs= [NET,PCMCIA]
Format:
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/init.h>
+#include <linux/kprobes.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/io.h>
#include <asm/processor.h>
#include <asm/debugreg.h>
#include <asm/sections.h>
+#include <asm/vsyscall.h>
#include <linux/topology.h>
#include <linux/cpumask.h>
#include <asm/pgtable.h>
{
setup_clear_cpu_cap(X86_FEATURE_XSAVE);
setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
+ setup_clear_cpu_cap(X86_FEATURE_XSAVES);
setup_clear_cpu_cap(X86_FEATURE_AVX);
setup_clear_cpu_cap(X86_FEATURE_AVX2);
return 1;
}
__setup("noxsaveopt", x86_xsaveopt_setup);
+ static int __init x86_xsaves_setup(char *s)
+ {
+ setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+ return 1;
+ }
+ __setup("noxsaves", x86_xsaves_setup);
+
#ifdef CONFIG_X86_32
static int cachesize_override = -1;
static int disable_x86_serial_nr = 1;
u16 __read_mostly tlb_lld_4m[NR_INFO];
u16 __read_mostly tlb_lld_1g[NR_INFO];
-/*
- * tlb_flushall_shift shows the balance point in replacing cr3 write
- * with multiple 'invlpg'. It will do this replacement when
- * flush_tlb_lines <= active_lines/2^tlb_flushall_shift.
- * If tlb_flushall_shift is -1, means the replacement will be disabled.
- */
-s8 __read_mostly tlb_flushall_shift = -1;
-
void cpu_detect_tlb(struct cpuinfo_x86 *c)
{
if (this_cpu->c_detect_tlb)
this_cpu->c_detect_tlb(c);
printk(KERN_INFO "Last level iTLB entries: 4KB %d, 2MB %d, 4MB %d\n"
- "Last level dTLB entries: 4KB %d, 2MB %d, 4MB %d, 1GB %d\n"
- "tlb_flushall_shift: %d\n",
+ "Last level dTLB entries: 4KB %d, 2MB %d, 4MB %d, 1GB %d\n",
tlb_lli_4k[ENTRIES], tlb_lli_2m[ENTRIES],
tlb_lli_4m[ENTRIES], tlb_lld_4k[ENTRIES],
tlb_lld_2m[ENTRIES], tlb_lld_4m[ENTRIES],
- tlb_lld_1g[ENTRIES], tlb_flushall_shift);
+ tlb_lld_1g[ENTRIES]);
}
void detect_ht(struct cpuinfo_x86 *c)
else
vgetcpu_mode = VGETCPU_LSL;
}
+
+/* May not be __init: called during resume */
+static void syscall32_cpu_init(void)
+{
+ /* Load these always in case some future AMD CPU supports
+ SYSENTER from compat mode too. */
+ wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
+ wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
+ wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
+
+ wrmsrl(MSR_CSTAR, ia32_cstar_target);
+}
+#endif
+
+#ifdef CONFIG_X86_32
+void enable_sep_cpu(void)
+{
+ int cpu = get_cpu();
+ struct tss_struct *tss = &per_cpu(init_tss, cpu);
+
+ if (!boot_cpu_has(X86_FEATURE_SEP)) {
+ put_cpu();
+ return;
+ }
+
+ tss->x86_tss.ss1 = __KERNEL_CS;
+ tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
+ wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+ wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
+ wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
+ put_cpu();
+}
#endif
void __init identify_boot_cpu(void)
(addr <= __get_cpu_var(debug_stack_addr) &&
addr > (__get_cpu_var(debug_stack_addr) - DEBUG_STKSZ));
}
+NOKPROBE_SYMBOL(is_debug_stack);
DEFINE_PER_CPU(u32, debug_idt_ctr);
this_cpu_inc(debug_idt_ctr);
load_current_idt();
}
+NOKPROBE_SYMBOL(debug_stack_set_zero);
void debug_stack_reset(void)
{
if (this_cpu_dec_return(debug_idt_ctr) == 0)
load_current_idt();
}
+NOKPROBE_SYMBOL(debug_stack_reset);
#else /* CONFIG_X86_64 */
git.samba.org / sfrench / cifs-2.6.git / commitdiff