Re: Poor windows VFIO performance, GPU stalls (bisected)

From: Geoffrey McRae
Date: Sun Jul 26 2020 - 09:34:49 EST

On 2020-07-26 23:30, Alex Williamson wrote:
On Sun, 26 Jul 2020 17:49:07 +1000
Geoffrey McRae <geoff@xxxxxxxxxxxxxxx> wrote:

Hi All,

The commit 22540ca3d00d2990a4148a13b92209c3dc5422db causes a Windows KVM
guest running under QEMU with a VFIO passthrough GPU to randomly stall
when using the GPU leading to the guest assuming that the driver has
hung. Reverting this commit resolves the problem.

Please double check this commit ID, I can't find it in mainline or
linux-next. Thanks,



The host system is configured with the following kernel arguments which
may be related:
isolcpus=0-5,24-29,6-11,30-35 rcu_nocbs=0-5,24-29,6-11,30-35

The system is an AMD Threadripper 2970WX on a Gigabyte x399 AORUS Gaming
7 board.
It has two GPUs each being passed through to two separate KVM guests,
one is an AMD Radeon 7 in a Linux guest, the other is a GeForce 1080Ti
in a Windows guest.
The cores used for these two guests are isolated from the host for
performance reasons.

Any insight as to why this is occurring would be appreciated. If you
need any more information or would like to test patches please let me

Kind Regards,
Geoffrey McRae