Re: [Qemu-devel] [PATCH] target-i386: Report known CPUID[EAX=0xD, ECX=0]:EAX bits as migratable

[Eduardo Habkost]

(CCing Richard, sorry I forgot to CC you)

Ping? Any objection to this fix?

On Wed, Sep 28, 2016 at 01:33:15PM -0300, Eduardo Habkost wrote:
> A regression was introduced by commit 96193c22a "target-i386:
> Move xsave component mask to features array": all
> CPUID[EAX=0xD,ECX=0]:EAX bits were being reported as unmigratable
> because they don't have feature names defined. This broke
> "-cpu host" because it enables only migratable features by
> default.
> 
> This adds a new field to FeatureWordInfo: migratable_flags, which
> will make those features be reported as migratable even if they
> don't have a property name defined.
> 
> Reported-by: Wanpeng Li <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---
>  target-i386/cpu.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 333309b..0807e92 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -258,6 +258,7 @@ typedef struct FeatureWordInfo {
>      int cpuid_reg;        /* output register (R_* constant) */
>      uint32_t tcg_features; /* Feature flags supported by TCG */
>      uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */
> +    uint32_t migratable_flags; /* Feature flags known to be migratable */
>  } FeatureWordInfo;
>  
>  static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> @@ -494,6 +495,10 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] 
> = {
>          .cpuid_needs_ecx = true, .cpuid_ecx = 0,
>          .cpuid_reg = R_EAX,
>          .tcg_features = ~0U,
> +        .migratable_flags = XSTATE_FP_MASK | XSTATE_SSE_MASK |
> +            XSTATE_YMM_MASK | XSTATE_BNDREGS_MASK | XSTATE_BNDCSR_MASK |
> +            XSTATE_OPMASK_MASK | XSTATE_ZMM_Hi256_MASK | 
> XSTATE_Hi16_ZMM_MASK |
> +            XSTATE_PKRU_MASK,
>      },
>      [FEAT_XSAVE_COMP_HI] = {
>          .cpuid_eax = 0xD,
> @@ -600,15 +605,13 @@ static uint32_t 
> x86_cpu_get_migratable_flags(FeatureWord w)
>  
>      for (i = 0; i < 32; i++) {
>          uint32_t f = 1U << i;
> -        /* If the feature name is unknown, it is not supported by QEMU yet */
> -        if (!wi->feat_names[i]) {
> -            continue;
> -        }
> -        /* Skip features known to QEMU, but explicitly marked as 
> unmigratable */
> -        if (wi->unmigratable_flags & f) {
> -            continue;
> +
> +        /* If the feature name is known, it is implicitly considered 
> migratable,
> +         * unless it is explicitly set in unmigratable_flags */
> +        if ((wi->migratable_flags & f) ||
> +            (wi->feat_names[i] && !(wi->unmigratable_flags & f))) {
> +            r |= f;
>          }
> -        r |= f;
>      }
>      return r;
>  }
> -- 
> 2.7.4
> 
> 

-- 
Eduardo