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[vfio-users] [help] Pci passthrough - I've probably done something really obvious wrong



Hi Vfio-users,

I'm trying to passthrough a single GPU (originally I was trying to passthrough two, but I have removed the other from the system to reduce the chance it could be causing a problem) to a standard Windows 8 VM.  Unfortunately upon starting the VM I get no output to either of my displays and the qemu output is spammed with dma errors such as below:

dma: command 78 not supported
dma: command 78 not supported
dma: command 80 not supported
dma: command 80 not supported
dma: command c8 not supported
dma: command c8 not supported
dma: command 80 not supported
dma: command 80 not supported
dma: command c8 not supported
dma: command c8 not supported
dma: command f8 not supported
dma: command c not supported
dma: command 84 not supported
...snip...

Let me run through some of the other specifics of my system.  I'm currently assigning the GPU to pci-stub using the grub commandline:
[root UnforseenCircumstances ~]# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-linux-vfio root=UUID=8aa1247d-5b3c-4282-b666-d4000ff5a517 rw quiet splash resume=UUID=17129c2f-d322-4662-8bf5-d1ca010968e6 i915.enable_hd_vgaarb=1 intel_iommu=on pci-stub.ids=10de:1200,10de:0e0c

I am also attempting to use an Intel iGPU has the host's display, for that reason I'm trying to use the vga arbitration patch.  Strangely however, I still seem to have hardware accelleration on my iGPU - Shouldn't that be impossible due to the nature of the patch?
After booting I use the following command to rebind the gpu to vfio-pci:
[root UnforseenCircumstances ~]# cat bindcmd.txt
sudo /usr/bin/vfio-bind 0000:01:00.0 0000:01:00.1

I cannot use OVMF as my GPU is a Geforce 560 Ti, it has not UEFI ROM support so SeaBios is my only option.
[root UnforseenCircumstances ~]# lspci -nnk | grep NVIDIA
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF114 [GeForce GTX 560 Ti] [10de:1200] (rev a1)
01:00.1 Audio device [0403]: NVIDIA Corporation GF114 HDMI Audio Controller [10de:0e0c] (rev a1)

And finally, as my GPU ROM won't play ball with me I'm using a downloaded ROM from TechpowerUp (For the same model!)
[root UnforseenCircumstances ~]# cat startvm.sh
#!/bin/bash

qemu-system-x86_64 \
-enable-kvm -m 1024 -cpu host,kvm=off \
-smp 4,sockets=1,cores=4,threads=1 \
-device vfio-pci,host=01:00.0,x-vga=on,rombar=0,romfile=/root/gpurom.rom \
-device vfio-pci,host=01:00.1 \
-vga none \
-device virtio-scsi-pci,id=scsi \
-drive file=/home/mwolffsohn/kvm/win8.iso,id=isocd,format=raw,if=none -device scsi-cd,drive=isocd \
-drive file=/root/win.img,id=disk,format=qcow2,if=none,cache=writeback -device scsi-hd,drive=disk \
-drive file=/home/mwolffsohn/kvm/virtio-win.iso,id=virtiocd,if=none,format=raw -device ide-cd,bus=ide.1,drive=virtiocd

Hopefully I'm doing something really obvious wrong because this has been confusing me for ages!
Many thanks in advance,

-Matthew Wolffsohn

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