Re: [Xen-devel] [PATCH v3 01/34] x86emul: support AVX512 opmask insns

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.10.18 at 20:32, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 18/09/18 12:53, Jan Beulich wrote:
>> @@ -1187,6 +1188,11 @@ static int _get_fpu(
>>              return X86EMUL_UNHANDLEABLE;
>>          break;
>>  
>> +    case X86EMUL_FPU_opmask:
>> +        if ( !(xcr0 & X86_XCR0_SSE) || !(xcr0 & X86_XCR0_OPMASK) )
>> +            return X86EMUL_UNHANDLEABLE;
>> +        break;
> 
> I see this follows the pattern from X86EMUL_FPU_ymm, but by the SSE
> check?  It is not relevant at this point - if xcr0.opmask is set, the
> opmask instructions should be usable.

I would agree with you from a functional POV, but please see the
last row of the table named "OS XSAVE Enabling Requirements of
Instruction Categories" in SDM Vol 2.

Jan



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