RE: [Xen-devel] [PATCH][RFC] Support more Capability StructuresandDevice Specific

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Ian Jackson wrote:
> 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.
> 
Ok, if it means guest direct MMIO to flash bios, then yes. But it is not
related with our discussion, i.e. no matter we pass through CFGS
registers or not, it may happen.

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