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

[Gordan Bobic <gordan@xxxxxxxxxx>]

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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