Re: [Qemu-devel] [PATCH v8 7/8] i386: Enable TOPOEXT feature on AMD EPYC CPU

[Eduardo Habkost]

On Thu, May 10, 2018 at 03:41:47PM -0500, Babu Moger wrote:
> Enable TOPOEXT feature on EPYC CPU. This is required to support
> hyperthreading on VM guests. Also extend xlevel to 0x8000001E.
> 
> Signed-off-by: Babu Moger <address@hidden>
> Tested-by: Geoffrey McRae <address@hidden>
> Reviewed-by: Eduardo Habkost <address@hidden>
> ---
>  target/i386/cpu.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 5cfc7bb0e1..575f2416a1 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -2382,7 +2382,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>          .features[FEAT_8000_0001_ECX] =
>              CPUID_EXT3_OSVW | CPUID_EXT3_3DNOWPREFETCH |
>              CPUID_EXT3_MISALIGNSSE | CPUID_EXT3_SSE4A | CPUID_EXT3_ABM |
> -            CPUID_EXT3_CR8LEG | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM,
> +            CPUID_EXT3_CR8LEG | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM |
> +            CPUID_EXT3_TOPOEXT,
>          .features[FEAT_7_0_EBX] =
>              CPUID_7_0_EBX_FSGSBASE | CPUID_7_0_EBX_BMI1 | CPUID_7_0_EBX_AVX2 
> |
>              CPUID_7_0_EBX_SMEP | CPUID_7_0_EBX_BMI2 | CPUID_7_0_EBX_RDSEED |
> @@ -2427,7 +2428,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
>          .features[FEAT_8000_0001_ECX] =
>              CPUID_EXT3_OSVW | CPUID_EXT3_3DNOWPREFETCH |
>              CPUID_EXT3_MISALIGNSSE | CPUID_EXT3_SSE4A | CPUID_EXT3_ABM |
> -            CPUID_EXT3_CR8LEG | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM,
> +            CPUID_EXT3_CR8LEG | CPUID_EXT3_SVM | CPUID_EXT3_LAHF_LM |
> +            CPUID_EXT3_TOPOEXT,

I forgot about one thing: you'll need to add EPYC.topoext=off and
EPYC-IBPB.topoext=off to PC_COMPAT_2_12.

>          .features[FEAT_8000_0008_EBX] =
>              CPUID_8000_0008_EBX_IBPB,
>          .features[FEAT_7_0_EBX] =
> @@ -4540,6 +4542,11 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error 
> **errp)
>              x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000000A);
>          }
>  
> +        /* TOPOEXT feature requires 0x8000001E */
> +        if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) {
> +            x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001E);
> +        }
> +
>          /* SEV requires CPUID[0x8000001F] */
>          if (sev_enabled()) {
>              x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001F);
> -- 
> 2.17.0
> 
> 

-- 
Eduardo