Re: [PATCH RFC 09/22] i386: add reserved FEAT_HYPERV_ECX CPUID leaf

[Eduardo Habkost]

On Fri, Sep 04, 2020 at 04:54:18PM +0200, Vitaly Kuznetsov wrote:
> As a preparation to expanding Hyper-V CPU features early, add
> reserved FEAT_HYPERV_ECX CPUID leaf.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  target/i386/cpu.c | 5 +++++
>  target/i386/cpu.h | 1 +
>  target/i386/kvm.c | 2 ++
>  3 files changed, 8 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index ef3c672cf415..70588571ccb1 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -974,6 +974,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] 
> = {
>          },
>          .cpuid = { .eax = 0x40000003, .reg = R_EBX, },
>      },
> +    [FEAT_HYPERV_ECX] = {
> +        .type = CPUID_FEATURE_WORD,
> +        /* reserved */

What does "reserved" mean here?

> +        .cpuid = { .eax = 0x40000003, .reg = R_ECX, },
> +    },
>      [FEAT_HYPERV_EDX] = {
>          .type = CPUID_FEATURE_WORD,
>          .feat_names = {
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 095d0bf75493..39e0e89aa41f 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -521,6 +521,7 @@ typedef enum FeatureWord {
>      FEAT_KVM_HINTS,     /* CPUID[4000_0001].EDX */
>      FEAT_HYPERV_EAX,    /* CPUID[4000_0003].EAX */
>      FEAT_HYPERV_EBX,    /* CPUID[4000_0003].EBX */
> +    FEAT_HYPERV_ECX,    /* CPUID[4000_0003].ECX */
>      FEAT_HYPERV_EDX,    /* CPUID[4000_0003].EDX */
>      FEAT_HV_RECOMM_EAX, /* CPUID[4000_0004].EAX */
>      FEAT_HV_NESTED_EAX, /* CPUID[4000_000A].EAX */
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 96ac719adca1..259be2d514dd 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1251,6 +1251,7 @@ static int hyperv_handle_properties(CPUState *cs,
>          if (c) {
>              env->features[FEAT_HYPERV_EAX] = c->eax;
>              env->features[FEAT_HYPERV_EBX] = c->ebx;
> +            env->features[FEAT_HYPERV_ECX] = c->ecx;
>              env->features[FEAT_HYPERV_EDX] = c->edx;
>          }
>  
> @@ -1350,6 +1351,7 @@ static int hyperv_handle_properties(CPUState *cs,
>      c->function = HV_CPUID_FEATURES;
>      c->eax = env->features[FEAT_HYPERV_EAX];
>      c->ebx = env->features[FEAT_HYPERV_EBX];
> +    c->ecx = env->features[FEAT_HYPERV_ECX];
>      c->edx = env->features[FEAT_HYPERV_EDX];
>  
>      c = &cpuid_ent[cpuid_i++];
> -- 
> 2.25.4
> 

-- 
Eduardo