diff options
| author | Cao Jin <[email protected]> | 2019-08-28 14:11:00 +0800 |
|---|---|---|
| committer | Borislav Petkov <[email protected]> | 2019-08-28 08:38:39 +0200 |
| commit | cbb1133b563a63901cf778220eb17e3ff1425aed (patch) | |
| tree | bdda67667c1c74c2af1530a581a49f77b98f3769 | |
| parent | 248d327ed7b6d3ebda2ac7b38482a306108bcd3e (diff) | |
x86/cpufeature: Explain the macro duplication
Explain the intent behind the duplication of the
BUILD_BUG_ON_ZERO(NCAPINTS != n)
check in *_MASK_CHECK and its immediate use in the *MASK_BIT_SET macros
too.
[ bp: Massage. ]
Suggested-by: Borislav Petkov <[email protected]>
Signed-off-by: Cao Jin <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
| -rw-r--r-- | arch/x86/include/asm/cpufeature.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 58acda503817..59bf91c57aa8 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -61,6 +61,13 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define CHECK_BIT_IN_MASK_WORD(maskname, word, bit) \ (((bit)>>5)==(word) && (1UL<<((bit)&31) & maskname##word )) +/* + * {REQUIRED,DISABLED}_MASK_CHECK below may seem duplicated with the + * following BUILD_BUG_ON_ZERO() check but when NCAPINTS gets changed, all + * header macros which use NCAPINTS need to be changed. The duplicated macro + * use causes the compiler to issue errors for all headers so that all usage + * sites can be corrected. + */ #define REQUIRED_MASK_BIT_SET(feature_bit) \ ( CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 0, feature_bit) || \ CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 1, feature_bit) || \ |