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RE: [Xen-devel] VP problematic for backend drivers on IA64?

To: "Muli Ben-Yehuda" <mulix@xxxxxxxxx>, "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>
Subject: RE: [Xen-devel] VP problematic for backend drivers on IA64?
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Tue, 24 Jan 2006 23:42:51 -0000
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, okrieg@xxxxxxxxxx
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Thread-topic: [Xen-devel] VP problematic for backend drivers on IA64?
 
> I understand that during the IA64 session at the summit there 
> was some discussion on VP being problematic for the current 
> backend drivers (or the other way around), and IOMMUs were 
> suggested as a possible solution. Could you please elaborate 
> on what's the problem?

It's simply that the actual DMA operations need to use machine
addresses. Ideally, you'd use an iommu to translate/partition, but in
the absence of an iommu simply enabling a privileged domain to read its
p2m table and translate the pfn to an mfn is sufficient. 

Ian

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