Re: [kvm-unit-tests PATCH v2 11/14] x86/sev: Define and use X86_FEATURE_* flags for CPUID 0x8000001F

[Liam Merwick <liam.merwick@oracle.com>]

On 10/06/2025 20:54, Sean Christopherson wrote:
> Define proper X86_FEATURE_* flags for CPUID 0x8000001F, and use them
> instead of open coding equivalent checks in amd_sev_{,es_}enabled().
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Liam Merwick <liam.merwick@oracle.com>


> ---
>   lib/x86/amd_sev.c   | 32 +++++---------------------------
>   lib/x86/amd_sev.h   |  3 ---
>   lib/x86/processor.h |  9 +++++++++
>   3 files changed, 14 insertions(+), 30 deletions(-)
> 
> diff --git a/lib/x86/amd_sev.c b/lib/x86/amd_sev.c
> index 6c0a66ac..b7cefd0f 100644
> --- a/lib/x86/amd_sev.c
> +++ b/lib/x86/amd_sev.c
> @@ -17,31 +17,15 @@ static unsigned short amd_sev_c_bit_pos;
>   
>   bool amd_sev_enabled(void)
>   {
> -	struct cpuid cpuid_out;
>   	static bool sev_enabled;
>   	static bool initialized = false;
>   
>   	/* Check CPUID and MSR for SEV status and store it for future function calls. */
>   	if (!initialized) {
> -		sev_enabled = false;
>   		initialized = true;
>   
> -		/* Test if we can query SEV features */
> -		cpuid_out = cpuid(CPUID_FN_LARGEST_EXT_FUNC_NUM);
> -		if (cpuid_out.a < CPUID_FN_ENCRYPT_MEM_CAPAB) {
> -			return sev_enabled;
> -		}
> -
> -		/* Test if SEV is supported */
> -		cpuid_out = cpuid(CPUID_FN_ENCRYPT_MEM_CAPAB);
> -		if (!(cpuid_out.a & SEV_SUPPORT_MASK)) {
> -			return sev_enabled;
> -		}
> -
> -		/* Test if SEV is enabled */
> -		if (rdmsr(MSR_SEV_STATUS) & SEV_ENABLED_MASK) {
> -			sev_enabled = true;
> -		}
> +		sev_enabled = this_cpu_has(X86_FEATURE_SEV) &&
> +			      rdmsr(MSR_SEV_STATUS) & SEV_ENABLED_MASK;
>   	}
>   
>   	return sev_enabled;
> @@ -72,17 +56,11 @@ bool amd_sev_es_enabled(void)
>   	static bool initialized = false;
>   
>   	if (!initialized) {
> -		sev_es_enabled = false;
>   		initialized = true;
>   
> -		if (!amd_sev_enabled()) {
> -			return sev_es_enabled;
> -		}
> -
> -		/* Test if SEV-ES is enabled */
> -		if (rdmsr(MSR_SEV_STATUS) & SEV_ES_ENABLED_MASK) {
> -			sev_es_enabled = true;
> -		}
> +		sev_es_enabled = amd_sev_enabled() &&
> +				 this_cpu_has(X86_FEATURE_SEV_ES) &&
> +				 rdmsr(MSR_SEV_STATUS) & SEV_ES_ENABLED_MASK;
>   	}
>   
>   	return sev_es_enabled;
> diff --git a/lib/x86/amd_sev.h b/lib/x86/amd_sev.h
> index ca7216d4..defcda75 100644
> --- a/lib/x86/amd_sev.h
> +++ b/lib/x86/amd_sev.h
> @@ -21,12 +21,9 @@
>   
>   /*
>    * AMD Programmer's Manual Volume 3
> - *   - Section "Function 8000_0000h - Maximum Extended Function Number and Vendor String"
>    *   - Section "Function 8000_001Fh - Encrypted Memory Capabilities"
>    */
> -#define CPUID_FN_LARGEST_EXT_FUNC_NUM 0x80000000
>   #define CPUID_FN_ENCRYPT_MEM_CAPAB    0x8000001f
> -#define SEV_SUPPORT_MASK              0b10
>   
>   /*
>    * AMD Programmer's Manual Volume 2
> diff --git a/lib/x86/processor.h b/lib/x86/processor.h
> index e3b3df89..1adfd027 100644
> --- a/lib/x86/processor.h
> +++ b/lib/x86/processor.h
> @@ -320,6 +320,15 @@ struct x86_cpu_feature {
>   #define X86_FEATURE_PFTHRESHOLD		X86_CPU_FEATURE(0x8000000A, 0, EDX, 12)
>   #define X86_FEATURE_VGIF		X86_CPU_FEATURE(0x8000000A, 0, EDX, 16)
>   #define X86_FEATURE_VNMI		X86_CPU_FEATURE(0x8000000A, 0, EDX, 25)
> +#define X86_FEATURE_SME			X86_CPU_FEATURE(0x8000001F, 0, EAX,  0)
> +#define X86_FEATURE_SEV			X86_CPU_FEATURE(0x8000001F, 0, EAX,  1)
> +#define X86_FEATURE_VM_PAGE_FLUSH	X86_CPU_FEATURE(0x8000001F, 0, EAX,  2)
> +#define X86_FEATURE_SEV_ES		X86_CPU_FEATURE(0x8000001F, 0, EAX,  3)
> +#define X86_FEATURE_SEV_SNP		X86_CPU_FEATURE(0x8000001F, 0, EAX,  4)
> +#define X86_FEATURE_V_TSC_AUX		X86_CPU_FEATURE(0x8000001F, 0, EAX,  9)
> +#define X86_FEATURE_SME_COHERENT	X86_CPU_FEATURE(0x8000001F, 0, EAX, 10)
> +#define X86_FEATURE_DEBUG_SWAP		X86_CPU_FEATURE(0x8000001F, 0, EAX, 14)
> +#define X86_FEATURE_SVSM		X86_CPU_FEATURE(0x8000001F, 0, EAX, 28)
>   #define X86_FEATURE_AMD_PMU_V2		X86_CPU_FEATURE(0x80000022, 0, EAX, 0)
>   
>   /*