[vfio-users] Binding Nvidia to vfio prevents hardware acceleration on Skylake

[Philip Abernethy]

Ok so I got myself a hardware upgrade and wanted to give vfio another shot.

The hardware:
Mainboard: MSI Z170A Gaming M7
CPU: Intel Core i5 6600K
Graphics: Gigabyte Geforce GTX 960

Host OS is Arch Linux, currently with unpatched standard kernel. The Z170
chipset doesn't officially support VT-d and it's up to the hardware vendor
to offer it, which MSI does.
My problem is, as soon as I include the vfio modules in the MODULES array
in mkinitcpio.conf (equivalent to dracut's add_drivers+=) the Nvidia card
is bound to vfio-pci on boot. Even without me specifying it in a modprobe
conf or the kernel line.
But if the Nvidia is bound to vfio-pci trying to use hardware acceleration
on the IGD will freeze the IGD (effectively Xorg or gnome-shell). The OS
will work fine, so I can still log in remotely, but the screen is useless.

Stable Configs:
/etc/X11/xorg.conf.d/20-intel.conf:
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "DRI" "3"
Option "AccelMethod" "sna"
EndSection

/etc/modprobe.d/i915.conf:
options i915 enable_rc6=1 enable_fbc=1 lvds_downclock=1 semaphores=1

I have installed the necessary packages for VA-API and VDPAU support on
Intel graphics.

I tried i915.enable_execlists=0 because the Arch wiki
<https://wiki.archlinux.org/index.php/Intel_graphics#Kernel_crashing_w.2Fkernels_4.0.2B_on_Broadwell.2FCore-M_chips>
mentions
it, but without success. Also it seems that as soon as the system starts
freezing I have to roll back quite a lot of changes in order to get it
working again. It's not enough to undo the last change after it stopped
working.
Has anyone gotten a similar combination to work? Can I reset the IGD
somehow to 'thaw' it?

Thanks in advance.
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