Re: [Qemu-devel] [PATCH v7 05/26] target/i386: add memory encryption feature cpuid support

[Paolo Bonzini]

On 07/02/2018 17:06, Brijesh Singh wrote:
> AMD EPYC processors support memory encryption feature. The feature
> is reported through CPUID 8000_001F[EAX].
> 
> Fn8000_001F [EAX]:
>  Bit 0   Secure Memory Encryption (SME) supported
>  Bit 1   Secure Encrypted Virtualization (SEV) supported
>  Bit 2   Page flush MSR supported
>  Bit 3   Ecrypted State (SEV-ES) support
> 
> when memory encryption feature is reported, CPUID 8000_001F[EBX] should
> provide additional information regarding the feature (such as which page
> table bit is used to mark pages as encrypted etc). The information in EBX
> and ECX may vary from one family to another hence we use the host cpuid
> to populate the EBX information.
> 
> The details for memory encryption CPUID is available in AMD APM
> (https://support.amd.com/TechDocs/24594.pdf) Section E.4.17
> 
> Cc: Paolo Bonzini <address@hidden>
> Cc: Richard Henderson <address@hidden>
> Cc: Eduardo Habkost <address@hidden>
> Signed-off-by: Brijesh Singh <address@hidden>
> ---
>  target/i386/cpu.c | 36 ++++++++++++++++++++++++++++++++++++
>  target/i386/cpu.h |  6 ++++++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index a49d2221adc9..4147eb6e18a9 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -234,6 +234,7 @@ static void x86_cpu_vendor_words2str(char *dst, uint32_t 
> vendor1,
>  #define TCG_EXT4_FEATURES 0
>  #define TCG_SVM_FEATURES 0
>  #define TCG_KVM_FEATURES 0
> +#define TCG_MEM_ENCRYPT_FEATURES 0
>  #define TCG_7_0_EBX_FEATURES (CPUID_7_0_EBX_SMEP | CPUID_7_0_EBX_SMAP | \
>            CPUID_7_0_EBX_BMI1 | CPUID_7_0_EBX_BMI2 | CPUID_7_0_EBX_ADX | \
>            CPUID_7_0_EBX_PCOMMIT | CPUID_7_0_EBX_CLFLUSHOPT |            \
> @@ -545,6 +546,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] 
> = {
>          .cpuid_reg = R_EDX,
>          .tcg_features = ~0U,
>      },
> +    [FEAT_MEM_ENCRYPT] = {
> +        .feat_names = {
> +            "sme", "sev", "page-flush-msr", "sev-es",

Why would sme ever be on in a guest?  That is, would a guest care about
whether SME is on in the host?

Paolo

> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +            NULL, NULL, NULL, NULL,
> +        },
> +        .cpuid_eax = 0x8000001F, .cpuid_reg = R_EAX,
> +        .tcg_features = TCG_MEM_ENCRYPT_FEATURES,
> +    }
>  };
>  
>  typedef struct X86RegisterInfo32 {
> @@ -1965,6 +1980,9 @@ static X86CPUDefinition builtin_x86_defs[] = {
>              CPUID_XSAVE_XGETBV1,
>          .features[FEAT_6_EAX] =
>              CPUID_6_EAX_ARAT,
> +        /* Missing: SEV_ES */
> +        .features[FEAT_MEM_ENCRYPT] =
> +            CPUID_8000_001F_EAX_SME | CPUID_8000_001F_EAX_SEV,
>          .xlevel = 0x8000000A,
>          .model_id = "AMD EPYC Processor",
>      },
> @@ -3589,6 +3607,19 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>              *edx = 0;
>          }
>          break;
> +    case 0x8000001F:
> +        if (env->features[FEAT_MEM_ENCRYPT] & CPUID_8000_001F_EAX_SEV) {
> +            *eax = env->features[FEAT_MEM_ENCRYPT];
> +            host_cpuid(0x8000001F, 0, NULL, ebx, NULL, NULL);
> +            *ecx = 0;
> +            *edx = 0;
> +        } else {
> +            *eax = 0;
> +            *ebx = 0;
> +            *ecx = 0;
> +            *edx = 0;
> +        }
> +        break;
>      case 0xC0000000:
>          *eax = env->cpuid_xlevel2;
>          *ebx = 0;
> @@ -4036,10 +4067,15 @@ static void x86_cpu_expand_features(X86CPU *cpu, 
> Error **errp)
>          x86_cpu_adjust_feat_level(cpu, FEAT_C000_0001_EDX);
>          x86_cpu_adjust_feat_level(cpu, FEAT_SVM);
>          x86_cpu_adjust_feat_level(cpu, FEAT_XSAVE);
> +        x86_cpu_adjust_feat_level(cpu, FEAT_MEM_ENCRYPT);
>          /* SVM requires CPUID[0x8000000A] */
>          if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_SVM) {
>              x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000000A);
>          }
> +        /* SEV requires CPUID[0x8000001F] */
> +        if ((env->features[FEAT_MEM_ENCRYPT] & CPUID_8000_001F_EAX_SEV)) {
> +            x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001F);
> +        }
>      }
>  
>      /* Set cpuid_*level* based on cpuid_min_*level, if not explicitly set */
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index f91e37d25dea..f7a0ab20fdd1 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -483,6 +483,7 @@ typedef enum FeatureWord {
>      FEAT_6_EAX,         /* CPUID[6].EAX */
>      FEAT_XSAVE_COMP_LO, /* CPUID[EAX=0xd,ECX=0].EAX */
>      FEAT_XSAVE_COMP_HI, /* CPUID[EAX=0xd,ECX=0].EDX */
> +    FEAT_MEM_ENCRYPT,   /* CPUID[8000_001F].EAX */
>      FEATURE_WORDS,
>  } FeatureWord;
>  
> @@ -679,6 +680,11 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  
>  #define CPUID_6_EAX_ARAT       (1U << 2)
>  
> +#define CPUID_8000_001F_EAX_SME             (1U << 0) /* SME */
> +#define CPUID_8000_001F_EAX_SEV             (1U << 1) /* SEV */
> +#define CPUID_8000_001F_EAX_PAGE_FLUSH_MSR  (1U << 2) /* Page flush MSR */
> +#define CPUID_8000_001F_EAX_SEV_ES          (1U << 3) /* SEV-ES */
> +
>  /* CPUID[0x80000007].EDX flags: */
>  #define CPUID_APM_INVTSC       (1U << 8)
>  
>