Re: [Xen-devel] [PATCH v4 02/20] x86emul: support most remaining AVX2 insns

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.03.18 at 14:39, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 28/02/18 12:58, Jan Beulich wrote:
> 
> You're missing a SoB on this version of the patch, but assuming that
> gets fixed, Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Thanks and - oops, I had dropped description and revision info as well:

I.e. those not being equivalents of SSEn ones, but with the exception
of the various gather operations.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v4: Split off AVX2 extensions to vbroadcasts{s,d}. Drop comment
    referring to no longer existing simd_scalar_dq.

>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -7306,6 +7325,11 @@ x86_emulate(
>>          op_bytes = 8 << vex.l;
>>          goto simd_0f_ymm;
>>  
>> +    case X86EMUL_OPC_VEX_66(0x0f38, 0x16): /* vpermps ymm/m256,ymm,ymm */
>> +    case X86EMUL_OPC_VEX_66(0x0f38, 0x36): /* vpermd ymm/m256,ymm,ymm */
> 
> It seems especially odd that these don't cope with vex.l or vex.w.  I
> can only guess that it down to a limitation in the vector pipeline which
> wasn't resolved until AVX-512 was introduced.

Yeah, there are a few more such anomalies, also in AVX512 iirc.

Jan


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