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RE: [Xen-devel] VGA passthrough to HVM

To: "'enming.teo@xxxxxxxxxxxxxxx'" <enming.teo@xxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] VGA passthrough to HVM
From: Tim Moore <timothy.moore@xxxxxxxxxxx>
Date: Wed, 26 Aug 2009 22:08:41 +0100
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Thread-topic: [Xen-devel] VGA passthrough to HVM
Hi Teo,

We have all been eagerly awaiting the PCI Passthrough for VGA patches to be 
released by the Xen-Devel community .. but from the sounds of the guys at  
Intel - it's not ready for public testing and it will most probably generate 
more questions for them to answer. Ultimately this is a distraction and will 
only delay the release of this functionality.

The closest you will get at the moment is the patches which form part of the 
XCI build tree and support is limited to the Intel chipset and onboard Intel 
graphics controller. I believe Ian Jackson also has some success with ATI but 
NVidia cards are known not to work.

There are other examples available including the "Neo 1:1 patch" which is based 
on an older version of Xen (I think 3.2).

NOTE: This ONLY applies to HVM, VGA Passthrough using xen-unstable and Linux 
non-HVM DomU is working, I have success with many Nvidia cards using this 
setup. You can use this to prove your Xen in preparation for the HVM patches 
and to ensure that your VT-d and Dom0 are sound.

Peter J. van der Maas inspired us all with his announcement, but no one has 
ever been able to reproduce:

Myself and Beng Heng also got to the same point as yourself, with issues on 
vBar<>pBar mapping and VGA BIOS. In all cases, the VGA card is visible in 
Device Manager in the DomU but the driver does not load. On My 8800GTS, the VGA 
Card FAN spins down the same as when booting under native XP but still the 
driver does not load.

Here are some good links with relevant information.





This is where I admit defeat and hand over to the brilliance of the Xen 

My last state is captured here:

The most success I have evidence of is from Alex Bebbington here:

If you look closely, this feature is on the Offical Xen Roadmap for Xen 4.0 
captured here:

There is sufficient information for the XCI project to build and create a demo 
install for the enthusiast:


I was downloading and building XCI before the above information was available 
by reading the XCI build tree and patches. The code is quite well structured 
along with containing some additional information on the xenvm and xenops 

Hopefully this pulls together all the information that is available on Xen VGA 

Tim Moore

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