[vfio-users] vfio binding undone

[Zycorax Tokoroa]

I seem to have troubles in getting vfio to work under ubuntu.
I have two discrete graphic cards, a GTX 970 (to be passed trough) and a 
GTX 960 for the host. The GTX 960 is in the primary slot, and is the 
card trough which I see grub and the early linux boot.

I am currently using kubuntu 16.04 with the following kernel parameters:
intel_iommu=on rd.modules-load=vfio-pci 
vfio-pci.ids=10de:13c2:1043:8508,10de:0fbb:1043:8508,1b21:1142:1043:85fd

dmesg shows vfio gets loaded properly and binds the devices:
[    6.978733] VFIO - User Level meta-driver version: 0.3
[    6.982220] vfio_pci: add [10de:13c2[1043:8508]] class 0x000000/00000000
[    6.992873] vfio_pci: add [10de:0fbb[1043:8508]] class 0x000000/00000000
[    6.992900] vfio_pci: add [1b21:1142[1043:85fd]] class 0x000000/0000000

However once the system has loaded up the binding has been undone only 
for the graphic card. The audio device associated and the USB controller 
are still correctly bound to vfio-pci:
# lspci -knn -s 2:
02:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM204 
[GeForce GTX 970] [10de:13c2] (rev a1)
         Subsystem: ASUSTeK Computer Inc. GM204 [GeForce GTX 970] 
[1043:8508]
         Kernel driver in use: nouveau
         Kernel modules: nvidiafb, nouveau
02:00.1 Audio device [0403]: NVIDIA Corporation GM204 High Definition 
Audio Controller [10de:0fbb] (rev a1)
         Subsystem: ASUSTeK Computer Inc. GM204 High Definition Audio 
Controller [1043:8508]
         Kernel driver in use: vfio-pci
         Kernel modules: snd_hda_intel

I have tried using the driver_override mechanism as in Alex's blog but 
it fails with the same result.