Re: [Xen-devel] vga passthrough with qemu-xen (or qemu upstream)

[Shakeel Butt <shakeel.butt@xxxxxxxxx>]

On Tue, Jan 21, 2014 at 4:55 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> Hello,
>
> On Mon, Jan 20, 2014 at 01:24:23PM +0000, Wu, Feng wrote:
>>
>>
>> > >>> >
>> > >>> > Hi all,
>> > >>> >
>> > >>> > Is it possible to do vga passthrough on xen-unstable with qemu-xen as
>> > >>> > device model? I tried but I am getting error 'gfx_passthru' invalid
>> > >>> > parameter for qemu-xen. I am able to do passthrough with qemu
>> > >>> > traditional i.e. qemu-dm.
>> > >>>
>> > >>> As far as I know, only qemu-traditional supports vga pass-through
>> > >>> right now.
>> > >>
>> > >> Right.
>> > >> It is not possible to assign your primary VGA card to a VM with
>> > >> qemu-xen. You should be able to assign your secondary VGA card though.
>> > >
>> > > Let me understand this correctly. If I have two VGA cards then I can
>> > > passthrough
>> > > secondary VGA card (in Dom0) to HVM as its primary VGA card. Is this
>> > > right and
>> > > if yes how can I do it?
>> >
>> > Passing any VGA card as a primary-in-domU has always been problematic.
>>
>> I think passing VGA card as a primary-in-domU works well in 
>> Qemu-traditional, right?
>>
>
> primary-in-domU requires vendor specific hacks in Xen qemu.
> qemu-traditional includes many patches for Intel IGD primary passthru support,
> but patches for AMD/ATI and Nvidia GPUs aren't merged to qemu-traditional.
>
> There unapplied patches for qemu-traditional (AMD/Nvidia) GPU passthru are in
> various source trees, mailinglist archives, and on some blogs around the 
> internet.
>
> Also for Intel IGD I think there's at least one outstanding patch/fix that
> hasn't been merged to qemu-traditional yet, see:
>
> http://lists.xenproject.org/archives/html/xen-devel/2013-02/msg00538.html
> http://lists.xen.org/archives/html/xen-devel/2013-07/msg01385.html
>
> The patch in question probably needs some work before it is suitable for 
> being applied to qemu-traditional.
>
Thanks for sharing. Just for the information, I was able to make
Nvidia K2000 work
in passthrough mode without any patch to qemu traditional.

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