diff options
| -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 ================================================== |