Re: [PATCH v2 1/2] KVM: x86: Insert "AMD" in KVM_X86_FEATURE_PSFD

[Sean Christopherson <seanjc@google.com>]

On Tue, Aug 30, 2022, Jim Mattson wrote:
> Intel and AMD have separate CPUID bits for each SPEC_CTRL bit. In the
> case of every bit other than PFSD, the Intel CPUID bit has no vendor
> name qualifier, but the AMD CPUID bit does. For consistency, rename
> KVM_X86_FEATURE_PSFD to KVM_X86_FEATURE_AMD_PSFD.
> 
> No functional change intended.
> 
> Signed-off-by: Jim Mattson <jmattson@google.com>
> Cc: Babu Moger <Babu.Moger@amd.com>
> ---
>  v1 -> v2: Dropped patch 2/3.
> 
>  arch/x86/kvm/cpuid.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 75dcf7a72605..07be45c5bb93 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -62,7 +62,7 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
>   * This one is tied to SSB in the user API, and not
>   * visible in /proc/cpuinfo.
>   */
> -#define KVM_X86_FEATURE_PSFD		(13*32+28) /* Predictive Store Forwarding Disable */
> +#define KVM_X86_FEATURE_AMD_PSFD	(13*32+28) /* Predictive Store Forwarding Disable */

This is asinine.  If KVM is forced to carry the feature bit then IMO we have every
right to the "real" name.  If we can't convince others that this belongs in
cpufeatures.h, then I vote to rename this to X86_FEATURE_AMD_PSFD so that we don't
have to special case this thing.

>  #define F feature_bit
>  #define SF(name) (boot_cpu_has(X86_FEATURE_##name) ? F(name) : 0)
> @@ -673,7 +673,7 @@ void kvm_set_cpu_caps(void)
>  		F(CLZERO) | F(XSAVEERPTR) |
>  		F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) |
>  		F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON) |
> -		__feature_bit(KVM_X86_FEATURE_PSFD)
> +		__feature_bit(KVM_X86_FEATURE_AMD_PSFD)
>  	);
>  
>  	/*
> -- 
> 2.37.2.672.g94769d06f0-goog
>