I recently upgraded my system and hit a VFIO windows 10 stuttering issue. The stuttering was so bad that windows games were unplayable at 24 fps on a Nvidia RTX 2080. Numa CPU pining did not help fix the issue no matter what I tried. The following are the bios issues I came across when trying to fix this issue. I now have a windows 10 VM running PUBG above 110 fps.
TLDR: Just because your VFIO VM boots does not mean the motherboard bios works. Also remember to enable MSI in the windows 10 registry.
I hope this post helps someone who thinks the motherboard bios is working with IOMMU.
ROG ZENITH EXTREME ALPHA
CPU: AMD Ryzen Threadripper 2920X 12- (24)
GPU: AMD ATI Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X
GPU: NVIDIA GeForce RTX 2080
Manjaro Linux x86_64
Linux MonsterLNX 5.4.13-AMD #1 SMP PREEMPT Mon Jan 20 02:06:42 PST 2020 x86_64 GNU/Linux ACS Patch
ROG-ZENITH-EXTREME-ALPHA-ASUS-0207.CAP: NOT USED
ROG-ZENITH-EXTREME-ALPHA-ASUS-0405.CAP: VM boots and no stuttering
ROG-ZENITH-EXTREME-ALPHA-ASUS-1901.CAP: VM boots but heavy stuttering
ROG-ZENITH-EXTREME-ALPHA-ASUS-2001.CAP: VM boots with Black Screen