[vfio-users] VM doesn't boot if I use GPU passthrough

[Ruben Felgenhauer]

Hi, Alex!

Thanks for your reply!
My GPU indeed has a seperate audio device located at 01:00.1.

However, just adding -device vfio-pci,host=01:00.1 doesn't seem to do 
the trick.
Of course the corresponding device is already blacklisted and bound to vfio.

The Debian Wiki entry about VGA passthrough 
(https://wiki.debian.org/VGAPassthrough) mentions QEMU arguments like 
"-device 
vfio-pci,host=01:00.0,bus=root.1,addr=00.0,multifunction=on,x-vga=on,romfile=... 
-device vfio-pci,host=01:00.1,bus=pcie.0" which seems to address GPUs 
with audio devices, but if I try to do something similar, the buses 
'root' and 'pcie' couldn't be found. Maybe I missed something very 
important?

On the same article, it says that the "HDMI soundcard [...] needs to be 
unbound from its driver":
# echo '0000:01:00.1' | sudo tee 
/sys/bus/pci/devices/0000:01:00.1/driver/unbind
I figured the vfio-bind script from the Arch Linux Forum thread 
(https://bbs.archlinux.org/viewtopic.php?id=162768) would do exactly 
this thing, so I didn't explicitly do so for the audio device. Is that okay?

Best regards,
Ruben

Am 18.01.2016 um 08:31 schrieb Alexander Petrenz:
> Hi Ruben,
>
> I guess your 750ti also has some audio device. You should pass through 
> this too. It should be something like 01:00.1. There are many command 
> line examples you can find about that.
> Also I´m not quite sure, if you should remove the x-vga=on.
>
> Regards
> Alex
>
> On Sun, Jan 17, 2016 at 11:12 PM, Ruben Felgenhauer 
> <4felgenh at informatik.uni-hamburg.de 
> <mailto:4felgenh at informatik.uni-hamburg.de>> wrote:
>
>     Hi,
>
>     I am trying to pass my nVidia GTX 750ti to my QEMU guest.
>
>     Problem is: After the QEMU monitor pops up, nothing happens. The
>     GPU's output is dead, and the vm won't be accessible via SSH
>     anymore, so it's very likely that the VM isn't booting up at all.
>     Also, there are no error messages from QEMU on the console
>     whatsoever which makes debugging it especially hard.
>
>     This is how I start the vm with normal vga emulation:
>     qemu-system-x86_64 -hda vm.ovl -boot c -enable-kvm -m 1024 -cpu
>     host,kvm=off -smp cores=4,threads=2 -redir tcp:5022::22
>     Everything runs fine in this case. To do the passthrough, I add this:
>     -device vfio-pci,host=01:00.0,multifunction=on,x-vga=on -vga none
>     This brings said problems with it. I also tried out multiple
>     different combinations of -device's arguments or even adding a
>     romfile for the GPU, but none of these steps changed anything at all.
>
>     Obviously, I am using a BIOS installation and I'm well-aware with
>     this bug: https://bugzilla.kernel.org/show_bug.cgi?id=107561, but
>     neither using less RAM (as you can see I am using 1GB now) nor
>     switching to an older Kernel changed anything about the problem. I
>     have tried Kernel 4.1.0 and 4.3.0.
>
>     Host is Debian testing with QEMU 2.5.0.
>     I tried both Debian and Windows 7 as a guest, but both are showing
>     exactly the same behaviour.
>     Mainboard is an ASUS Z87-PLUS. The 750ti is produced by ASUS aswell.
>
>     Any idea how I could get passthrough running?
>
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