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RE: [Xen-devel] [PATCH][RFC] Support more Capability Structures andDevic

To: "Dong, Eddie" <eddie.dong@xxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH][RFC] Support more Capability Structures andDevice Specific
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Thu, 3 Jul 2008 10:50:34 +0100
Cc: Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
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Dong, Eddie writes ("RE: [Xen-devel] [PATCH][RFC] Support more Capability 
Structures andDevice Specific"):
> Alan Cox wrote:
> > In the general case there are also some really nasty
> > dirty attacks you can't stop with an IOMMU one of which
> > is to reflash the BIOS of the graphics card to which you
> > were given unrestricted access so that you compromise the
> > entire system next boot. These attacks appear well
> > understood except by IOMMU marketing people ;) 
> 
> Same with above, this is already protected by IOMMU, peer to peer DMA is
> not supported right now.

You have evidently completely misunderstood Alan's point.

I was going to explain it again but I'm not sure I know how to say it
more clearly.  Alan's scenario doesn't involve any peer to peer DMA.

Ian.

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