From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: KVM: x86: use proper port value when checking io instruction
 permission (v2)
Date: Thu, 26 May 2011 09:49:21 +0200
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References: <20110524171120.GA19906@amt.cnet> <20110524172706.GC22042@redhat.com> <20110525181820.GA14921@amt.cnet> <4DDDF3D6.3000505@redhat.com> <20110526065511.GA29458@redhat.com> <4DDDFB07.2050909@redhat.com> <4DDDFB78.9070307@redhat.com> <20110526070737.GB29458@redhat.com>
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Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
	kvm <kvm@vger.kernel.org>, Joerg Roedel <joerg.roedel@amd.com>
To: Gleb Natapov <gleb@redhat.com>
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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.

Paolo