Re: [PATCH v3 2/2] x86: KVM: Advertise AMD's speculation control features

Borislav Petkov
2025-04-11T09:44:23Z

On Wed, Dec 04, 2024 at 04:43:45PM +0300, Maksim Davydov wrote:
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 45f87a026bba..0a709d03ee5c 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -343,7 +343,10 @@
> #define X86_FEATURE_AMD_IBPB (13*32+12) /* Indirect Branch Prediction Barrier */
> #define X86_FEATURE_AMD_IBRS (13*32+14) /* Indirect Branch Restricted Speculation */
> #define X86_FEATURE_AMD_STIBP (13*32+15) /* Single Thread Indirect Branch Predictors */
> +#define X86_FEATURE_AMD_IBRS_ALWAYS_ON (13*32+16) /* Indirect Branch Restricted Speculation always-on preferred */
> #define X86_FEATURE_AMD_STIBP_ALWAYS_ON (13*32+17) /* Single Thread Indirect Branch Predictors always-on preferred */
> +#define X86_FEATURE_AMD_IBRS_PREFERRED (13*32+18) /* Indirect Branch Restricted Speculation is preferred over SW solution */
> +#define X86_FEATURE_AMD_IBRS_SAME_MODE (13*32+19) /* Indirect Branch Restricted Speculation provides Same Mode protection */

This is an AMD-specific leaf - you don't need to put "AMD_" in front of every
bit.

--
Regards/Gruss,
Boris.