Re: [Xen-devel] 1 GPU multiple VMs

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 13 Feb 2012, Pasi KÃrkkÃinen wrote:
> On Mon, Feb 13, 2012 at 04:27:38PM +0200, Pasi KÃrkkÃinen wrote:
> > On Wed, Feb 08, 2012 at 08:22:33PM +0200, Pasi KÃrkkÃinen wrote:
> > > On Wed, Feb 08, 2012 at 08:18:47PM +0200, Pasi KÃrkkÃinen wrote:
> > > > On Wed, Feb 08, 2012 at 06:11:56PM +0000, Stefano Stabellini wrote:
> > > > > On Wed, 8 Feb 2012, Pasi KÃÆÃ?rkkÃÆÃ?inen wrote:
> > > > > > On Wed, Feb 08, 2012 at 05:20:31PM +0000, Stefano Stabellini wrote:
> > > > > > > On Fri, 3 Feb 2012, Jacobs Jordi wrote:
> > > > > > > > Hi,
> > > > > > > > 
> > > > > > > > I am wondering how GPU sharing could/should be implemented for 
> > > > > > > > the Xen Hypervisor.
> > > > > > > > 
> > > > > > > > I have come across several papers that explain many 
> > > > > > > > possibilities on GPU sharing for multiple VMs but I'm not sure 
> > > > > > > > wich
> > > > > > > > one would be the best solution for Xen.
> > > > > > > > 
> > > > > > > > API remoting (gallium3D) (ex. Xen3D project)
> > > > > > > > Mediated passthrough (Multiplexing the GPU while maintaining 
> > > > > > > > the different contexts.)
> > > > > > > > 
> > > > > > > > Can you guys give me your idea on the matter?
> > > > > > > > Please also mention any existing projects you know that are 
> > > > > > > > related to this problem.
> > > > > > > 
> > > > > > > My personal opinion is that the simplest thing to do is OpenGL
> > > > > > > remoting. Gallium remoting could also be OK but considering that 
> > > > > > > many
> > > > > > > cards don't have Gallium drivers we would probably end up doing 
> > > > > > > two
> > > > > > > conversions instead of one (DirectX->Gallium in the guest,
> > > > > > > Gallium->OpenGL in dom0).
> > > > > > > Mediated passthrough is very card specific so I am afraid you 
> > > > > > > would end
> > > > > > > up writing virtualization specific drivers for all the cards you 
> > > > > > > want to
> > > > > > > support. Not to mention that you might need to access some 
> > > > > > > videocard
> > > > > > > interfaces that on Nvidia are not discosed.
> > > > > > > 
> > > > > > > I believe that virtualbox already supports OpenGL remoting in a 
> > > > > > > decent
> > > > > > > way, so I would start from there, port what they have to Xen, and
> > > > > > > improve it.
> > > > > > > 
> > > > > > 
> > > > > > I wonder if SPICE already supports OpenGL stuff..
> > > > > > I think it's at least supposed to be able to support OpenGL.
> > > > > > 
> > > > > > (http://lists.freedesktop.org/archives/spice-devel/2011-November/006018.html)
> > > > >  
> > > > > Not yet, but I think that they are working on it. Still very early 
> > > > > days
> > > > > though.
> > > > > Also it would only work with HVM guests, while having a proper xen
> > > > > frontend/backend OpenGL remoting driver pair would work for both.
> > > > 
> > > > Yep.
> > > > 
> > > > There's also: http://sourceforge.net/projects/vmgl/
> > > > 
> > > > "OpenGL apps running inside a VM use VMGL to obtain graphics hardware 
> > > > acceleration. VMGL supports VMware, Xen PV and HVM, qemu, and KVM VMs; 
> > > > X11-based OS such as Linux, FreeBSD and OpenSolaris; and ATI, Nvidia 
> > > > and Intel GPUs. "
> > > > 
> > > 
> > > And Chromium might have something related aswell:
> > > http://chromium.sourceforge.net/doc/index.html
> > > 
> > 
> > And one more related interesting link:
> > 
> > "VMware's Virtual GPU Driver Is Running Fast":
> > http://www.phoronix.com/scan.php?page=article&item=vmware_vmwgfx_g3d&num=1
> > 
> > So the Gallium3D virtual GPU/OpenGL stuff with VMware VMs seems to work 
> > pretty nicely these days!
> > That might be worth a look.. and to get it running with Xen.
> > 
> > I think SPICE is going to use Gallium3D aswell.
> > 
> 
> I thought i'd already stop spamming but here's more relevant links:
> 
> "SPICE On KVM/QEMU Works Towards Gallium3D":
> http://www.phoronix.com/scan.php?page=news_item&px=MTA1NTQ
> 
> And even more interesting!:
> 
> "The Gallium3D Driver That Few Know About / Xen vGallium":
> http://www.phoronix.com/scan.php?page=news_item&px=ODE2NQ
 
That's right: Xen had a Gallium3D based virtual GPU implementation
before anyone else, however it never went out of the prototype phase. It
would be great if a well motivated developer could get the sources
(https://github.com/smowton/vgallium,
http://www.cl.cam.ac.uk/~cs448/git/trunk/doc/Build-instructions) and
continue the work!
Ideally we would have a PV frontend/backend drivers pair that would work
for both PV and HVM guests. On the guest side the work would need to be
upstreamed to Mesa/DRM, on the host side we would need support in
QEMU/Linux.

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