[vfio-users] Ryzen 1600 pci passthrough degraded performance

[Alex Williamson]

On Tue, 16 May 2017 21:33:18 +0200
Stefan Maksimovic <lebijogurt at gmail.com> wrote:

> My setup:
> Ryzen 1600
> Asus B350 Prime Plus
> r5 230 (linux host)
> gtx 1060 (for passthrough)
> 
> The passthrough process itself went without much trouble.
> I've been able to boot the VM, the 1060 was properly detected, went on to
> install the drivers.
> Next, I fired up Dota 2 to take it for a spin and noticed it only gave
> around 20 fps.
> The 1060 should't have troubles running this game. Haven't run any other
> games.

Other users have noted performance issues related to npt on AMD
platforms, not just Ryzen.  Generally disabling npt does not cause
functional issues and restores some graphics performance, but reduces
overall VM performance.  Intel does not have similar problems with
their equivalent technology (ept).  The root cause of the AMD issue is
unknown, KVM traces have provided no areas for investigation.  Thanks,

Alex