Re: [Xen-users] Primary VGA Passthrough Status

[Gordan Bobic <gordan@xxxxxxxxxx>]

On Tue, 8 Oct 2013 00:04:33 -0700, David Erickson 
<halcyon1981@xxxxxxxxx> wrote:
> On Mon, Oct 7, 2013 at 11:29 PM, Gordan Bobic  wrote:
>
> On 10/07/2013 09:33 PM, David Erickson wrote:
>   Hi All-
>  Is it possible yet to pass through a ATI or Nvidia GPU as the 
> primary
>  VGA card to a Win 7/8 VM, and have it fully functional there (DXVA
> etc),
>
>  Why exactly do you need the card to be primary in domU? IME this
> doesn't gain you anything other than being able to see the BIOS 
> splash
> screen and boot animation on the external monitor (which in itself
> isn't worth the extra effort).
>
> Primarily it is for htpc functionality like Blu-ray playback software
> and Digital Cablecard based playback using devices like a HDHR
> Prime. I believe the code that tests for playready (or equivalent)
> compatibility always looks at the primary video card and finds it
> totally missing any of these features and refuses to play back
> properly. I need to verify that having a passed through card as the
> primary actually solves these issues, but I think it is a reasonable
> hunch (unless anyone else has already tried this and proved it 
> wrong).
I never used it so cannot comment on it. David Techer maintains a
patch set for Nvidia cards that include primary passthrough support.
The one in particular you will need is the one that gives the VBIOS
loading supprot in domU. Between that and a GTX480 modified to a
Quadro 6000 (VBIOS editing required) you _might_ just be able
to get it to work. I never tried primary passthrough since secondary
passthrough has always worked for all of my requirements.

>   without crashing the guest or the host during operation or when
>  resetting the guest?
>
>  It works fine with Nvidia Quadro cards (real or modified GeForce),
> provided your hardware works properly (e.g. no dodgy PCI bridges 
> (such
> as Nvidia NF200) bypassing the IOMMU). The latter is, it turns out,
> quite rare - an awful lot of hardware seems to have IOMMU support
> broken to some extent.
>
> Is there something special in the bios/firmware that is enabled when
> converting these to Quadros?
You have to modify the strap bits. This can be done with a BIOS edit
on cards up to GTX480, or with some soldering on a GTX680 (you will
need good eyes, steady hands, high quality soldering paste and some
pro grade soldering kit (hot air or oven - you might be able to
get away with a really tiny soldering tip, but bear in mind that
you will be looking at soldering both ends of a resistor that is 1mm
long, without shorting it out). If you want the easy option, go
for a GTX480 and BIOS mod it (or a GTX470 -> Quadro 5000 or a
GTS450 (make sure you get a 1GB GDDR5 one) -> Quadro 2000 I have
used all of the above extensively without any issues).

Gordan


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