Re: [Xen-devel] [PATCH v3 08/25] x86emul: add tables for XOP 08 and 09 extension spaces

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.02.18 at 12:43, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 07/12/17 14:04, Jan Beulich wrote:
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -458,6 +458,20 @@ static const opcode_desc_t xop_table[] =
>>      DstReg|SrcImm|ModRM,
>>  };
>>  
>> +static const struct {
>> +    uint8_t simd_size:5;
>> +    uint8_t two_op:1;
>> +    uint8_t four_op:1;
>> +} ext8f08_table[256] = {
>> +};
>> +
>> +static const struct {
>> +    uint8_t simd_size:5;
>> +    uint8_t two_op:1;
>> +} ext8f09_table[256] = {
>> +    [0x01 ... 0x02] = { .two_op = 1 },
>> +};
>> +
> 
> What about 8f0a ?  We've got emulation for bextr already, and might want
> to consider #GRP4 seeing as we expose LWP to guests.

I'd prefer to convert that to a table at the time we need it.

>> @@ -2726,7 +2740,7 @@ x86_decode(
>>              }
>>              break;
>>  
>> -        case vex_0f38:
>> +        case ext_0f38:
>>              d = ext0f38_table[b].to_mem ? DstMem | SrcReg
>>                                          : DstReg | SrcMem;
>>              if ( ext0f38_table[b].two_op )
>> @@ -2736,7 +2750,14 @@ x86_decode(
>>              state->simd_size = ext0f38_table[b].simd_size;
>>              break;
>>  
>> -        case vex_0f3a:
>> +        case ext_8f09:
>> +            if ( ext8f09_table[b].two_op )
>> +                d |= TwoOp;
>> +            state->simd_size = ext8f09_table[b].simd_size;
>> +            break;
>> +
>> +        case ext_0f3a:
>> +        case ext_8f08:
>>              /*
>>               * Cannot update d here yet, as the immediate operand still
>>               * needs fetching.
>> @@ -2928,6 +2949,15 @@ x86_decode(
>>          break;
>>  
>>      case ext_8f08:
>> +        d = DstReg | SrcMem;
>> +        if ( ext8f08_table[b].two_op )
>> +            d |= TwoOp;
>> +        else if ( ext8f08_table[b].four_op && !mode_64bit() )
>> +            imm1 &= 0x7f;
>> +        state->desc = d;
>> +        state->simd_size = ext8f08_table[b].simd_size;
>> +        break;
> 
> I presume that these don't actually impact our currently implemented XOP
> instructions?

No - as the description says, the patch converts the existing ones,
it doesn't break them (and the test harness continuing to work
confirms this).

Jan


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