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Re: [Xen-users] VGA passthrough with Xen 4.3 and xl toolstack - performance degradation resolved?



On 03/12/2014 08:24 PM, H. Sieger wrote:
About restart of domU after Windows upgrade - hey, that's the famous
Windows experience. Joke aside, after Windows updates (and reboots) I
also often get a "stuck" Windows domU, or Windows just quits and I have
to restart again.  This seems to be normal for Windows.

I'm pretty sure that's not normal.

However, I can
start and close down and restart my Windows 7 domU as often as I like
(when not updating Windows) without any performance or stability issues.
But then I have a Nvidia card. Again, I'm referring to secondary
passthrough.

Indeed, it works just fine with an Nvidia card.

As for primary passthrough, I have never succeeded with it, though my
hardware (the Nvidia Quadro 2000) looks like a good candidate for it. Or
am I wrong?

IIRC primary passthrough requires side-loading the VBIOS into domU and POST-ing it. Last time I checked there was a limitation on the VBIOS size of 64KB which rules out all the Kepler (6xx and later) and Maxwell based GPUs.

But considering this doesn't gain you anything other than being able to see the startup splash screen up to the point the driver loads on your external monitor, I don't think there is a great sense of urgency toward adding that enhancement. With ATI it has the added benefit that the VBIOS unbreaks the GPU state, but overall, implementing a bus reset seems like a much more generic and useful feature for the time being.

Is the primary passthrough patch you refer to applicable to all graphics
cards, or just to AMD? (sorry for my ignorance)

I think the patch in question is ATI only.

Gordan

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