Re: [PATCH v2 2/5] x86/cpufeatures: Add Intel feature bits for Speculation Control

Dave Hansen
2018-01-23T18:43:07Z

On 01/23/2018 08:52 AM, David Woodhouse wrote:
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 7b25cf3..0a51070 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -320,6 +320,9 @@
> /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */
> #define X86_FEATURE_AVX512_4VNNIW (18*32+ 2) /* AVX-512 Neural Network Instructions */
> #define X86_FEATURE_AVX512_4FMAPS (18*32+ 3) /* AVX-512 Multiply Accumulation Single precision */
> +#define X86_FEATURE_SPEC_CTRL (18*32+26) /* Speculation Control (IBRS + IBPB) */
> +#define X86_FEATURE_STIBP (18*32+27) /* Single Thread Indirect Branch Predictors */
> +#define X86_FEATURE_ARCH_CAPABILITIES (18*32+29) /* IA32_ARCH_CAPABILITIES MSR (Intel) */

Should we be adding flags (STIBP) for which we currently have no user in
the kernel?