Re: KVM: x86: use proper port value when checking io instruction permission (v2)

[Gleb Natapov <gleb@redhat.com>]

On Thu, May 26, 2011 at 11:00:24AM +0200, Paolo Bonzini wrote:
> On 05/26/2011 10:26 AM, Gleb Natapov wrote:
> >Why would c->dst.bytes != c->src.bytes for cwd/cdq/cqo if we'll set
> >c->dst.bytes to op_bytes during decode?
> 
> Duh, you're right, cwd/cdq/cqo uses SrcAcc which has
> 
>                 c->src.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
> 
> so in practice c->src.bytes = c->op_bytes.
> 
> I still find it confusing that DstDX would use c->op_bytes without
> honoring ByteOp unlike pretty much everything else; but yes, there
> is a possible use of DstDX outside in/out.
> 
We can make it honor ByteOp. There will be no instruction that will
specify DstDX | ByteOp though.

--
			Gleb.