[Bug 196409] kvm_amd nested pagetable gpu passthrough performance oddities

bugzilla-daemon
2017-10-09T10:19:59Z

badOne (andizhigh@gmx.de) changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |andizhigh@gmx.de

--- Comment #32 from badOne (andizhigh@gmx.de) ---
I also noticed heavy performance loss with my Ryzen 1700X and KVM. Disabling
npt completely is no option either, it justs slows down the CPU a ton (which
totally makes sense)

My specs are:
- Ryzen 1700X
- ASUS Prime x370 Pro
- GPU0: GTX 1050 (host)
- GPU1: GTX 1070 (guest)

I also experimented with CPU pinning, mounting a whole SSD instead of just
using a virtual disk, trying different drivers, settings, etc.

Nothing of the above seemed to change anything. With npt=1 some games are
running fine (e.g. League of Legends), some are running ok (e.g. Path of Exile)
and some are running extremely bad (e.g. Player Unknown's Battlegrounds, GTA 5,
CS:GO, etc.)

I looked into the code but I'm not able to dive into the project due to the
lack of time.

This is a major issue in my opinion and AMD + the guys from KVM should look
into this together. Intel got it running, too. In addition with Xen it's
working perfectly but I really don't like using Xen, I like KVM a lot more.

Please fix this issue. If help is needed just contact me, I will when time
allows it.