Re: [Xen-devel] [PATCH v3 10/25] x86emul: support 3DNow! insns

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.02.18 at 14:02, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 07/12/17 14:05, Jan Beulich wrote:
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -355,6 +355,36 @@ static const struct {
>>      [0xff] = { ModRM }
>>  };
>>  
>> +static const uint16_t _3dnow_table[16] = {
> 
> Comment explaining how these mappings work?  It looks like nibble
> splits, but I still can't work out how to crossreference with the opcode
> tables.

Will do. Array index is high opcode nibble, bit index is low opcode
nibble.

>> +    [0x0] = (1 << 0xd) /* pi2fd */,
>> +    [0x1] = (1 << 0xd) /* pf2id */,
>> +    [0x9] = (1 << 0x0) /* pfcmpge */ |
>> +            (1 << 0x4) /* pfmin */ |
>> +            (1 << 0x6) /* pfrcp */ |
>> +            (1 << 0x7) /* pfrsqrt */ |
>> +            (1 << 0xa) /* pfsub */ |
>> +            (1 << 0xe) /* pfadd */,
>> +    [0xa] = (1 << 0x0) /* pfcmpge */ |
>> +            (1 << 0x4) /* pfmax */ |
>> +            (1 << 0x6) /* pfrcpit1 */ |
>> +            (1 << 0x7) /* pfrsqit1 */ |
>> +            (1 << 0xa) /* pfsubr */ |
>> +            (1 << 0xe) /* pfacc */,
>> +    [0xb] = (1 << 0x0) /* pfcmpeq */ |
>> +            (1 << 0x4) /* pfmul */ |
>> +            (1 << 0x6) /* pfrcpit2 */ |
>> +            (1 << 0x7) /* pmulhrw */ |
>> +            (1 << 0xf) /* pavgusb */,
>> +};
>> +
>> +static const uint16_t _3dnow_ext_table[16] = {
>> +    [0x1] = (1 << 0xd) /* pi2fw */,
>> +    [0x1] = (1 << 0xc) /* pf2iw */,
> 
> You presumably want an | in here instead?

No, the first of the two lines is wrong and needs to be

    [0x0] = (1 << 0xc) /* pi2fw */,

(wrong post-copy-and-paste editing).

>> @@ -5505,6 +5537,26 @@ x86_emulate(
>>      case X86EMUL_OPC(0x0f, 0x19) ... X86EMUL_OPC(0x0f, 0x1f): /* nop */
>>          break;
> 
> 0f 0d prefetches?  They are 3DNow instructions, but available on later
> processors.

And it is for that latter reason (I assume) that we have these
already.

Jan


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