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

[Wanpeng Li]

2016-09-30 2:40 GMT+08:00 Eduardo Habkost <address@hidden>:
> (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>

Reviewed-by: Wanpeng Li <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