Re: [PATCH v3 1/2] x86/cpufeatures: Add macros for Intel's new fast rep string features

H. Peter Anvin
2022-09-02T04:40:15Z

On 9/1/22 14:18, Jim Mattson wrote:
> KVM_GET_SUPPORTED_CPUID should reflect these host CPUID bits. The bits
> are already cached in word 12. Give the bits X86_FEATURE names, so
> that they can be easily referenced. Hide these bits from
> /proc/cpuinfo, since the host kernel makes no use of them at present.
>
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
> arch/x86/include/asm/cpufeatures.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index ef4775c6db01..454f0faa8e90 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -308,6 +308,9 @@
> /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
> #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
> #define X86_FEATURE_AVX512_BF16 (12*32+ 5) /* AVX512 BFLOAT16 instructions */
> +#define X86_FEATURE_FZRM (12*32+10) /* "" Fast zero-length REP MOVSB */
> +#define X86_FEATURE_FSRS (12*32+11) /* "" Fast short REP STOSB */
> +#define X86_FEATURE_FSRC (12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
>
> /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
> #define X86_FEATURE_CLZERO (13*32+ 0) /* CLZERO instruction */

Any reason why these bits are hidden from /proc/cpuinfo?

-hpa