[vfio-users] Latest Windows 10 “feature” update breaks IGD passthrough

[John Koelndorfer]

Hi Manuel,

I don't have your exact setup, but I ran into something sort of similar
when I was working through my GPU passthrough setup.

In my configuration I have an Nvidia GPU (GTX 970) that I wanted to be able
to use in both virtual Windows and Linux. Early on when I was trying to get
the swapping to work correctly I noticed that I would get graphical
corruption in the VM similar to what you describe: colorful vertical
"stripes" on the screen. The stripes wouldn't appear in the very early
stages in the VM boot process, so you could for example enter OVMF setup or
the EFI console and things would be fine. They appeared instead once
Windows started booting. I tested an Arch Linux ISO in the virtual machine
and had similar results after I got past the boot menu.

What fixed it for me was binding my Nvidia GPU to vfio-pci right away at
boot instead of letting the nvidia driver grab the card. To do that, I set
MODULES="vfio vfio_iommu_type1 vfio_pci vfio_virqfd" in
/etc/mkinitcpio.conf (running an Arch system), set config for vfio-pci to
grab my Nvidia card in /etc/modprobe.d, and ran `mkinitcpio -p linux`. The
Arch wiki has more info on that.

I'm no expert on this stuff. I can only guess that the nvidia GPU driver
was doing some sort of boot-time initialization that was hosing things up.
Now that vfio-pci grabs the card at boot, I'm able to boot a Windows VM or
X server on the Nvidia card (and swap between the two without rebooting).

Does your IGD get claimed by vfio-pci right away at boot?

On Sun, Sep 3, 2017 at 12:36 PM, Manuel Ullmann <ullman.alias at posteo.de>
wrote:

> For the record,
>
> well I still don‘t know, why I had no output during the two feature
> updates (1607, 1703), but after they ran through in
> just 8 hours with a qxl config, the stripes just appeared once with vga
> passthrough and have never been seen again…
>
> Thanks,
> Manuel
>
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