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

[Geoffrey McRae]

On 2020-07-26 23:32, Geoffrey McRae wrote:
> 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,
> >
> > Alex
>
> Confirmed:
>
> https://github.com/torvalds/linux/commit/22540ca3d00d2990a4148a13b92209c3dc5422db

Sorry, I just noticed my error, it should be:
aa202f1f56960c60e7befaa0f49c72b8fa11b0a8

> > > 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
> > > know.
> > >
> > > Kind Regards,
> > > Geoffrey McRae
> > > HostFission
> > >
> > > https://hostfission.com