Re: [PATCH] KVM: emulator: implement AAD instruction

[Gleb Natapov <gleb@redhat.com>]

On Fri, Dec 14, 2012 at 11:44:22AM +0100, Paolo Bonzini wrote:
> Il 10/12/2012 10:42, Gleb Natapov ha scritto:
> > Windows2000 uses it during boot. This fixes
> > https://bugzilla.kernel.org/show_bug.cgi?id=50921
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index 39171cb..92c7292 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -2852,6 +2852,27 @@ static int em_das(struct x86_emulate_ctxt *ctxt)
> >  	return X86EMUL_CONTINUE;
> >  }
> >  
> > +static int em_aad(struct x86_emulate_ctxt *ctxt)
> > +{
> > +	u8 al = ctxt->dst.val & 0xff;
> > +	u8 ah = (ctxt->dst.val >> 8) & 0xff;
> > +
> > +	al = (al + (ah * ctxt->src.val)) & 0xff;
> > +
> > +	ctxt->dst.val = (ctxt->dst.val & 0xffff0000) | al;
> > +
> > +	ctxt->eflags &= ~(X86_EFLAGS_PF | X86_EFLAGS_SF | X86_EFLAGS_ZF);
> > +
> > +	if (!al)
> > +		ctxt->eflags |= X86_EFLAGS_ZF;
> > +	if (!(al & 1))
> > +		ctxt->eflags |= X86_EFLAGS_PF;
> 
> This is wrong, it should check the parity of al (even=1, odd=0).
> 
Oops, yes it should check number of bits set, not value itself.

> Perhaps you can use the trick of em_das:
> 
>         /* Set PF, ZF, SF */
>         ctxt->src.type = OP_IMM;
>         ctxt->src.val = 0;
>         ctxt->src.bytes = 1;
>         emulate_2op_SrcV(ctxt, "or");
Will do.

> 
> Paolo
> 
> > +	if (al & 0x80)
> > +		ctxt->eflags |= X86_EFLAGS_SF;
> > +
> > +	return X86EMUL_CONTINUE;
> > +}
> > +
> >  static int em_call(struct x86_emulate_ctxt *ctxt)
> >  {
> >  	long rel = ctxt->src.val;
> > @@ -3801,7 +3822,7 @@ static const struct opcode opcode_table[256] = {
> >  	D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret),
> >  	/* 0xD0 - 0xD7 */
> >  	D2bv(DstMem | SrcOne | ModRM), D2bv(DstMem | ModRM),
> > -	N, N, N, N,
> > +	N, I(DstAcc | SrcImmByte | No64, em_aad), N, N,
> >  	/* 0xD8 - 0xDF */
> >  	N, N, N, N, N, N, N, N,
> >  	/* 0xE0 - 0xE7 */
> > --
> > 			Gleb.
> > --
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> > 

--
			Gleb.