From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: KVM: x86: use proper port value when checking io instruction
 permission (v2)
Date: Thu, 26 May 2011 11:26:39 +0300
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Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
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To: Paolo Bonzini <pbonzini@redhat.com>
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On Thu, May 26, 2011 at 09:49:21AM +0200, Paolo Bonzini wrote:
> On 05/26/2011 09:07 AM, Gleb Natapov wrote:
> >> Still, op_bytes is irrelevant for
> >> SrcDX, the 16-bit version is always used.
> >
> >If SrcDX/DstDX will be used only for decoding in/out instruction
> >then yes. Otherwise it is nice to have more general decoder.
> 
> Not counting instructions that read/write many registers
> (rdmsr/wrmsr, mul/imul/div/idiv, rdtsc, etc.), I think the only
> other instruction with an implicit DstDX is cwd/cdq/cqo.  Since
> cwd/cdq/cqo needs c->dst.bytes = c->src.bytes (not op_bytes) I think
> DstDX is not really reusable beyond port instructions.
> 
Why would c->dst.bytes != c->src.bytes for cwd/cdq/cqo if we'll set
c->dst.bytes to op_bytes during decode?

--
			Gleb.