[vfio-users] KVM + QEMU + GPU passthrough (Windows7 Guest)

[Francisco Menendez]

I'm having a bit of an odd issue and would greatly appreciate it if
someone has any clue as of what might be happening.

The system:
* Intel CPU with VTx and VTd enabled in BIOS
* NVidia GTX 980 - isolated (vfio), to be used by the guest
* Intel graphics for the host (Arch Linux x64)

What I've done:

* Added "iommu_intel=on" to the kernel boot command line
* Blacklisted the nouveau driver
* Added the vfio-pci driver and assigned the necessary ids (GPU +
attached HDMI sound)
* Confirmed IOMMU groups ( /sys/kernel/iommu_groups/ -type l output is OK)
* Confirmed vfio-pci capture with dmesg

What happens:

After booting windows, I get the GPU displaying the "Starting Windows"
splash screen, with animation and everything. Thus far, I think the
GPU passthrough is successful. However, after that, the screen gets
stuck there while the system keeps booting. I even hear the windows
chime as it starts, but the screen is still showing "Starting Windows"

If I use emulated VGA, the NVidia card shows "Code 12", but I hear
this is expected if the emulated VGA is turned on.

The above is also reproducible with the windows installer ( The GPU
output displays: "Windows is loading files" -> "Starting windows" ->
no more screen updates )

QEMU commandline:

--------------
qemu-system-x86_64 \
  -name windows7 \
  -cpu host,kvm=off \
  -smp 8,sockets=1,cores=4,threads=2 \
  -enable-kvm \
  -machine type=pc,accel=kvm,iommu=on \
  -m 16G -mem-prealloc -balloon none \
  -rtc clock=host,base=utc \
  -soundhw hda \
  -device ioh3420,bus=pci.0,addr=1c.0,multifunction=on,port=1,chassis=1,id=root.1
\
  -device vfio-pci,host=01:00.0,bus=root.1,addr=00.0,multifunction=on,x-vga=on \
  -device vfio-pci,host=01:00.1,bus=root.1,addr=00.1 \
  -drive if=pflash,format=raw,readonly,file=/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd
\
  -drive if=pflash,format=raw,file=/usr/share/edk2.git/ovmf-x64/OVMF_VARS-pure-efi.fd
\
  -drive file=win7.img,if=ide,format=raw,media=disk \
  -monitor stdio \
  -device piix3-usb-uhci -device usb-tablet \
  -vga none -serial null -parallel null -nodefaults -nodefconfig
----------------

Let me know if you need any other information about the setup.
Thank you in advance!