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authorLinus Torvalds <torvalds@linux-foundation.org>2022-05-23 18:01:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-05-23 18:01:31 -0700
commitc5a3d3c01e90e74166f95eec9db6fcc3ba72a9d6 (patch)
tree3f938013952aaf28beab3e6228a4c4e5aa90badf /Documentation
parent3a755ebcc2557e22b895b8976257f682c653db1d (diff)
parent2147c438fde135d6c145a96e373d9348e7076f7f (diff)
Merge tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 CPU feature updates from Borislav Petkov: - Remove a bunch of chicken bit options to turn off CPU features which are not really needed anymore - Misc fixes and cleanups * tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/speculation: Add missing prototype for unpriv_ebpf_notify() x86/pm: Fix false positive kmemleak report in msr_build_context() x86/speculation/srbds: Do not try to turn mitigation off when not supported x86/cpu: Remove "noclflush" x86/cpu: Remove "noexec" x86/cpu: Remove "nosmep" x86/cpu: Remove CONFIG_X86_SMAP and "nosmap" x86/cpu: Remove "nosep" x86/cpu: Allow feature bit names from /proc/cpuinfo in clearcpuid=
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt24
-rw-r--r--Documentation/x86/cpuinfo.rst5
-rw-r--r--Documentation/x86/x86_64/boot-options.rst9
3 files changed, 12 insertions, 26 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0c648a867dfa..1169a4acfeb1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -631,12 +631,17 @@
Defaults to zero when built as a module and to
10 seconds when built into the kernel.
- clearcpuid=BITNUM[,BITNUM...] [X86]
+ clearcpuid=X[,X...] [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
+ numbers X. Note the Linux-specific bits are not necessarily
+ stable over kernel options, but the vendor-specific
ones should be.
+ X can also be a string as appearing in the flags: line
+ in /proc/cpuinfo which does not have the above
+ instability issue. However, not all features have names
+ in /proc/cpuinfo.
+ Note that using this option will taint your kernel.
Also note that user programs calling CPUID directly
or using the feature without checking anything
will still see it. This just prevents it from
@@ -3478,8 +3483,6 @@
nocache [ARM]
- noclflush [BUGS=X86] Don't use the CLFLUSH instruction
-
delayacct [KNL] Enable per-task delay accounting
nodsp [SH] Disable hardware DSP at boot time.
@@ -3490,16 +3493,11 @@
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]
+ nosmap [PPC]
Disable SMAP (Supervisor Mode Access Prevention)
even if it is supported by processor.
- nosmep [X86,PPC64s]
+ nosmep [PPC64s]
Disable SMEP (Supervisor Mode Execution Prevention)
even if it is supported by processor.
@@ -3699,8 +3697,6 @@
nosbagart [IA-64]
- nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
-
nosgx [X86-64,SGX] Disables Intel SGX kernel support.
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
diff --git a/Documentation/x86/cpuinfo.rst b/Documentation/x86/cpuinfo.rst
index 5d54c39a063f..08246e8ac835 100644
--- a/Documentation/x86/cpuinfo.rst
+++ b/Documentation/x86/cpuinfo.rst
@@ -140,9 +140,8 @@ from #define X86_FEATURE_UMIP (16*32 + 2).
In addition, there exists a variety of custom command-line parameters that
disable specific features. The list of parameters includes, but is not limited
-to, nofsgsbase, nosmap, and nosmep. 5-level paging can also be disabled using
-"no5lvl". SMAP and SMEP are disabled with the aforementioned parameters,
-respectively.
+to, nofsgsbase, nosgx, noxsave, etc. 5-level paging can also be disabled using
+"no5lvl".
e: The feature was known to be non-functional.
----------------------------------------------
diff --git a/Documentation/x86/x86_64/boot-options.rst b/Documentation/x86/x86_64/boot-options.rst
index 4efb1fa039ef..03ec9cf01181 100644
--- a/Documentation/x86/x86_64/boot-options.rst
+++ b/Documentation/x86/x86_64/boot-options.rst
@@ -157,15 +157,6 @@ Rebooting
newer BIOS, or newer board) using this option will ignore the built-in
quirk table, and use the generic default reboot actions.
-Non Executable Mappings
-=======================
-
- noexec=on|off
- on
- Enable(default)
- off
- Disable
-
NUMA
====