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

[Avi Kivity <avi@redhat.com>]

On 05/26/2011 09:55 AM, Gleb Natapov wrote:
> >  >
> >  >+	case SrcDX:
> >  >+		c->src.type = OP_REG;
> >  >+		c->src.bytes = c->op_bytes;
> >
> >  Needs to be 2.  Otherwise we'll see extra bits from edx, or lose
> >  bits from dx if it's a 1-byte instruction.
> >
> But those extra bits will be dropped by check_perm_in() anyway.

It isn't nice to depend on it.

btw, Marcelo, the patch should also make use of the decode during execution:

     case 0xef: /* out dx,(e/r)ax */
         c->dst.val = c->regs[VCPU_REGS_RDX];

^^ can drop


     do_io_out:
         ops->pio_out_emulated(ctxt, c->src.bytes, c->dst.val,
&c->src.val, 1);
         c->dst.type = OP_NONE;    /* Disable writeback. */
         break;

> Can
> c->op_bytes ever be 1?

in %dx, %al

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.