[fedora-virt] Fatal PCIe error 928 on KVM GPU Passthrough

[Mario Ceresa]

Thanks Alex, for your kind and detailed response: please keep up with the
good work!

I'm interested in learning more about this and I have access to Quadro 4000
and 5000 cards, so please tell me if I can help with testing. I do not mind
compiling from sources or doing some debug, but I have almost zero
practical knowledge on GPU cards so I'll need some pointers :)

Best,

Mario


On 20 June 2013 23:19, Alex Williamson <alex.williamson at redhat.com> wrote:

> On Thu, 2013-06-20 at 09:30 +0200, Mario Ceresa wrote:
> > Dear all,
> > does anybody know if it is currently possible to do GPU passthrough in
> kvm?
> > I have access to a dual Quadro 4000 setup and I would like to pass the
> > second one to kvm for use in a VM.
> >
> > I read a lot on internet and it seems feasible [1, 2, 3] and there is
> even
> > a reported success case [5].
> >
> > However when I start the VM the host reboots with PCIe error 928:
> > Completion timeout.
> >
> > My current setup is:
> >
> > * Fedora 18 with 3.9.4-200 x86_64
> > * dmesg | grep -e DMAR -e IOMMU shows that they are both enabled
> > * nvidia driver installed from rpmfusion
> > * I use vfio assignment as per [4]
>
> GPUs are not well supported yet and you're probably not going to get
> very far unless you're willing to compile a kernel and qemu and use qemu
> from the commandline instead of through libvirt.  Some people have luck
> assigning a GPU as a secondary graphics device to the emulated video,
> others do not.  Sometimes I suspect this has more to do with addresses
> assigned to the physical device possibly matching the virtual device...
> so it really is luck.
>
> I've posted branches of qemu and kernel that seem to work well for
> several people (this is what was pointed to in the Arch Linux thread you
> footnoted).  That code attempts to use the assigned GPU as the primary
> graphics head for the guest.  I have one Quadro card on hand and it
> never works as well as the GeForce cards, YMMV.  Graphics cards have all
> sorts of interesting backdoors to get to PCI config space and I suspect
> the Quadro cards are not as well supported by the Nouveau project, which
> we've used for reverse engineered documentation of some of these quirks.
>
> There's still some work to do before that code can be posted upstream,
> in particular I've seen cases where a PCI bus won't come back from reset
> without resetting the host system.  We need to make it more stable
> before pushing to get it upstream.  Thanks,
>
> Alex
>
>
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