Re: [Qemu-devel] [PATCH 3/7] i386: Add spec-ctrl CPUID bit

[Gonglei (Arei)]

> -----Original Message-----
> From: Qemu-devel
> [mailto:address@hidden On
> Behalf Of Eduardo Habkost
> Sent: Tuesday, January 09, 2018 11:45 PM
> To: address@hidden
> Cc: Paolo Bonzini
> Subject: [Qemu-devel] [PATCH 3/7] i386: Add spec-ctrl CPUID bit
> 
> Add the feature name and a CPUID_7_0_EDX_SPEC_CTRL macro.
> 
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
>  target/i386/cpu.h | 1 +
>  target/i386/cpu.c | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 07f47997d6..de387c1311 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -667,6 +667,7 @@ typedef uint32_t
> FeatureWordArray[FEATURE_WORDS];
> 
>  #define CPUID_7_0_EDX_AVX512_4VNNIW (1U << 2) /* AVX512 Neural
> Network Instructions */
>  #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply
> Accumulation Single Precision */
> +#define CPUID_7_0_EDX_SPEC_CTRL     (1U << 26) /* Speculation Control
> */
> 
>  #define CPUID_XSAVE_XSAVEOPT   (1U << 0)
>  #define CPUID_XSAVE_XSAVEC     (1U << 1)
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 9f4f949899..1be1642eb2 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -459,7 +459,7 @@ static FeatureWordInfo
> feature_word_info[FEATURE_WORDS] = {
>              NULL, NULL, NULL, NULL,
>              NULL, NULL, NULL, NULL,
>              NULL, NULL, NULL, NULL,
> -            NULL, NULL, NULL, NULL,
> +            NULL, NULL, "spec-ctrl", NULL,
>              NULL, NULL, NULL, NULL,
>          },
>          .cpuid_eax = 7,
> --
> 2.14.3
> 
Don't we need to pass-through cupid_7_edx to guest when configuring '-cpu host'?
Otherwise how guests use IBPB/IBRS/STIPB capabilities?

Thanks,
-Gonglei