From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: KVM: x86: use proper port value when checking io instruction
 permission (v2)
Date: Thu, 26 May 2011 10:02:31 +0300
Message-ID: <4DDDFB07.2050909@redhat.com>
References: <20110524171120.GA19906@amt.cnet> <20110524172706.GC22042@redhat.com> <20110525181820.GA14921@amt.cnet> <4DDDF3D6.3000505@redhat.com> <20110526065511.GA29458@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm <kvm@vger.kernel.org>,
	Joerg Roedel <joerg.roedel@amd.com>
To: Gleb Natapov <gleb@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:42988 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751339Ab1EZHCh (ORCPT <rfc822;kvm@vger.kernel.org>);
	Thu, 26 May 2011 03:02:37 -0400
In-Reply-To: <20110526065511.GA29458@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

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.