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Re: [Xen-devel] HVM PCI passthrough NON VT-d

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] HVM PCI passthrough NON VT-d
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Wed, 28 Nov 2007 01:14:48 +0000
Cc: Ashish Bijlani <ashish.bijlani@xxxxxxxxx>
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> folks, is PCI passthrough available on non vt-d machines for hvm
> guests?

PCI passthrough without any hardware support is being worked on by Neocleus, I 
believe.  I'm not aware of it being checked into xen-unstable yet but you 
should be able to see the patches online in the mailing list archives.

This won't give the safety guarantees that vt-d would give you - you have to 
trust the guest.

I don't know whether their implementation has any other restrictions or 
caveats.

> am i right in thinking that the PCI passthrough feature on non 
> vt-d machines will make a hvm guest directly access a physical device
> and recv corresponding external interrupts from xen as events? thanks.

Yes, but I think it wouldn't see them as Xen events, they would be emulated to 
look like real device interrupts (because the guest is not Xen aware).

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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