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

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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.

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