diff options
| author | Naveen N Rao (AMD) <naveen@kernel.org> | 2025-04-09 13:13:41 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-04-09 13:56:52 +0200 |
| commit | af76f7d57ee9a3be7b3840595ce3e2bdedd594a7 (patch) | |
| tree | 75b2eb3273a2ffeb7601221c6c28e639d3039754 /Documentation | |
| parent | 83f6665a49c3d44ad0c08f837d352dd290f5d10b (diff) | |
Documentation/x86: Update the naming of CPU features for /proc/cpuinfo
Commit:
78ce84b9e0a5 ("x86/cpufeatures: Flip the /proc/cpuinfo appearance logic")
changed how CPU feature names should be specified. Update document to
reflect the same.
Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250409111341.GDZ_ZWZS4LckBcirLE@fat_crate.local
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/arch/x86/cpuinfo.rst | 28 |
1 files changed, 12 insertions, 16 deletions
diff --git a/Documentation/arch/x86/cpuinfo.rst b/Documentation/arch/x86/cpuinfo.rst index 6ef426a52cdc..7114f34ba3e6 100644 --- a/Documentation/arch/x86/cpuinfo.rst +++ b/Documentation/arch/x86/cpuinfo.rst @@ -130,14 +130,18 @@ x86_cap/bug_flags[] arrays in kernel/cpu/capflags.c. The names in the resulting x86_cap/bug_flags[] are used to populate /proc/cpuinfo. The naming of flags in the x86_cap/bug_flags[] are as follows: -a: The name of the flag is from the string in X86_FEATURE_<name> by default. ----------------------------------------------------------------------------- -By default, the flag <name> in /proc/cpuinfo is extracted from the respective -X86_FEATURE_<name> in cpufeatures.h. For example, the flag "avx2" is from -X86_FEATURE_AVX2. - -b: The naming can be overridden. --------------------------------- +a: Flags do not appear by default in /proc/cpuinfo +-------------------------------------------------- + +Feature flags are omitted by default from /proc/cpuinfo as it does not make +sense for the feature to be exposed to userspace in most cases. For example, +X86_FEATURE_ALWAYS is defined in cpufeatures.h but that flag is an internal +kernel feature used in the alternative runtime patching functionality. So the +flag does not appear in /proc/cpuinfo. + +b: Specify a flag name if absolutely needed +------------------------------------------- + If the comment on the line for the #define X86_FEATURE_* starts with a double-quote character (""), the string inside the double-quote characters will be the name of the flags. For example, the flag "sse4_1" comes from @@ -148,14 +152,6 @@ needed. For instance, /proc/cpuinfo is a userspace interface and must remain constant. If, for some reason, the naming of X86_FEATURE_<name> changes, one shall override the new naming with the name already used in /proc/cpuinfo. -c: The naming override can be "", which means it will not appear in /proc/cpuinfo. ----------------------------------------------------------------------------------- -The feature shall be omitted from /proc/cpuinfo if it does not make sense for -the feature to be exposed to userspace. For example, X86_FEATURE_ALWAYS is -defined in cpufeatures.h but that flag is an internal kernel feature used -in the alternative runtime patching functionality. So, its name is overridden -with "". Its flag will not appear in /proc/cpuinfo. - Flags are missing when one or more of these happen ================================================== |