Re: [Xen-devel] [PATCH v3 1/3] x86/emulate: add support for {, v}movq xmm, xmm/m64

[Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>]

On Monday 01 August 2016 07:19:51 Jan Beulich wrote:
> >>> On 01.08.16 at 04:52, <mdontu@xxxxxxxxxxxxxxx> wrote:  
> > @@ -4412,6 +4412,7 @@ x86_emulate(
> >      case 0x7f: /* movq mm,mm/m64 */
> >                 /* {,v}movdq{a,u} xmm,xmm/m128 */
> >                 /* vmovdq{a,u} ymm,ymm/m256 */
> > +    case 0xd6: /* {,v}movq xmm,xmm/m64 */
> >      {
> >          uint8_t *buf = get_stub(stub);
> >          struct fpu_insn_ctxt fic = { .insn_bytes = 5 };
> > @@ -4429,9 +4430,9 @@ x86_emulate(
> >              case vex_66:
> >              case vex_f3:
> >                  host_and_vcpu_must_have(sse2);
> > -                buf[0] = 0x66; /* movdqa */
> > +                buf[0] = 0x66; /* SSE */  
> 
> The comment change here indicates a problem: So far it was indicating
> that despite the possible F3 prefix (movdqu) we encode a 66 one
> (movdqa). Opcode D6 prefixed with F3, however, is movq2dq, which
> you then either don't emulate correctly, or if it happens to be
> emulated correctly you should include in the comment accompanying
> the case label. And its AVX counterpart should then produce #UD.

I see. Thanks for the hint. I'll try to write a test case and see if it
"just works" or needs extra handling.

-- 
Mihai DONȚU

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