GPU passthrough support for Stoney [Radeon R2/R3/R4/R5 Graphics]?

[Alex Deucher]

On Thu, May 16, 2019 at 4:07 PM Micah Morton <mortonm at chromium.org> wrote:
>
> On Wed, May 15, 2019 at 7:19 PM Alex Deucher <alexdeucher at gmail.com> wrote:
> >
> > On Wed, May 15, 2019 at 2:26 PM Micah Morton <mortonm at chromium.org> wrote:
> > >
> > > Hi folks,
> > >
> > > I'm interested in running a VM on a system with an integrated Stoney
> > > [Radeon R2/R3/R4/R5 Graphics] card and passing through the graphics
> > > card to the VM using the IOMMU. I'm wondering whether this is feasible
> > > and supposed to be doable with the right setup (as opposed to passing
> > > a discrete GPU to the VM, which I think is definitely doable?).
> > >
> > > So far, I can do all the qemu/kvm/vfio/iommu stuff to run the VM and
> > > pass the integrated GPU to it, but the drm driver in the VM fails
> > > during amdgpu_device_init(). Specifically, the logs show the SMU being
> > > unresponsive, which leads to a 'SMU firmware load failed' error
> > > message and kernel panic. I can share VM logs and the invocation of
> > > qemu and such if helpful, but first wanted to know at a high level if
> > > this should be feasible?
> > >
> > > P.S.: I'm not initializing the GPU in the host bios or host kernel at
> > > all, so I should be passing a fresh GPU to the VM. Also, I'm pretty
> > > sure I'm running the correct VGA bios for this GPU in the guest VM
> > > bios before guest boot.
> > >
> > > Any comments/suggestions would be appreciated!
> >
> > It should work in at least once as long as your vm is properly set up.
>
> Is there any reason running coreboot vs UEFI at host boot would make a
> difference? I was running a modified version of coreboot that avoids
> doing any GPU initialization in firmware -- so the first POST happens
> inside the guest.

The GPU on APUs shares a bunch of resources with the CPU.  There are a
bunch of blocks which are shared and need to be initialized on both
for everything to work properly.

>
> > Note that the driver needs access to the vbios image in the guest to
> > get device specific configuration details (clocks, display connector
> > configuration, etc.).
>
> Is there anything I need to do to ensure this besides passing '-device
> vfio-pci,...,romfile=/path/to/vgarom' to qemu?

You need the actual vbios rom image from your system.  The image is
board specific.

Alex