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RE: [Xen-devel] Can I expose a pci device to HVM domU?

To: Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Can I expose a pci device to HVM domU?
From: Daniel Stodden <stodden@xxxxxxxxxx>
Date: Tue, 19 Feb 2008 23:01:32 +0100
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On Tue, 2008-02-19 at 16:51 -0500, Caitlin Bestler wrote:
> > > >
> > > > PS:- NIC Is does not have Intel's VT-d.
> > > >
> > >
> > > If the Guest is HVM, how would it know how to give usable
> > > DMA addresses to the NIC? (Whether it should be trusted to
> > > in the absence of an Address Translation Service is the next
> > > question, but first is whether it could even do it at all).
> > >
> > > A PV Guest, by contrast, would know the distinction between
> > > GPAs and SPAs (not that it makes it any more trustworthy).
> > 
> > VT-d / IO-MMUs fixes that.
> > 
> If you interpret the problem as being that the NIC is not
> itself aware of VT-d (or other IOMMU), but that there is an
> IOMMU active, then that would be true.
> My interpretation of "does not have VT-d" is that there is
> no IOMMU active in the target platform at all.

It was meant as a rather general reply (I thought yours was as well). I
simply overlooked the no-VTd statement above. Sorry, you're certainly


Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
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