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

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 01/20/2014 09:15 PM, Shakeel Butt wrote:
> On Mon, Jan 20, 2014 at 7:29 AM, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
> > On 2014-01-20 15:19, Shakeel Butt wrote:
> > > On Mon, Jan 20, 2014 at 5:31 AM, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
> > > > On 2014-01-20 13:24, Wu, Feng wrote:
> > > > > > -----Original Message-----
> > > > > > From: xen-devel-bounces@xxxxxxxxxxxxx
> > > > > > [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Gordan Bobic
> > > > > > Sent: Monday, January 20, 2014 8:50 PM
> > > > > > To: xen-devel@xxxxxxxxxxxxx
> > > > > > Subject: Re: [Xen-devel] vga passthrough with qemu-xen (or qemu
> > > > > > upstream)
> > > > > >
> > > > > > On 2014-01-20 12:31, Shakeel Butt wrote:
> > > > > > > On Mon, Jan 20, 2014 at 4:09 AM, Stefano Stabellini
> > > > > > > <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > > > > > > > On Mon, 20 Jan 2014, Wu, Feng wrote:
> > > > > > > > > > -----Original Message-----
> > > > > > > > > > From: xen-devel-bounces@xxxxxxxxxxxxx
> > > > > > > > > > [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Shakeel
> > > > > > > > > > Butt
> > > > > > > > > > Sent: Monday, January 20, 2014 1:48 PM
> > > > > > > > > > To: xen-devel@xxxxxxxxxxxxx
> > > > > > > > > > Subject: [Xen-devel] vga passthrough with qemu-xen (or qemu
> > > > > > > > > > upstream)
> > > > > > > > > >
> > > > > > > > > > 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?
> > > >
> > > >
> > > > I never managed to get it working - it certainly isn't just a matter of
> > > > enabling the option. There is at least the matter of also side-loading
> > > > the VGA BIOS, and IIRC that was limited to 64KB in size, which rules
> > > > out all ATI and Nvidia GPUs of the past 2-3 generations.
> > > >
> > > > Having said that - I never found a particularly good use-case for
> > > > primary passthrough. Once the GPU driver loads it works just the
> > > > same for all intents and purposes.
> > > I have successfully managed to passthrough VGA card as primary to DomU
> > > with qemu traditional. I am trying to do the same with upstream qemu
> > > because
> > >   I need some new features of the upstream qemu which are not available
> > > in qemu traditional.
> > >
> > > With qemu upstream I can passthrough as secondary VGA card to DomU
> > > and able to see it in device manager in DomU (Windows 7) but Windows
> > > couldn't use it and display some error that another card is being used as
> > > display. I want Windows to use the passthroughed vga card  as its display.
> >
> > Disable the other (emulated) card in device manager and reboot
> > the domU. That should fix it.
> This is not working for me. I am disabling the device and even uninstalling the
> driver but on reboot Windows 7 install the driver for the emulated vga and
> make it primary vga.
Don't uninstall the driver, just disable the device. If you uninstall 
it, it will get re-detected. If you disable it, it should show up with a 
red cross next to it, and your secondary GPU will start working the way 
you want it to.


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