Re: [PATCH 0/2] KVM: SVM: Set pCPU during IRTE update if vCPU is running

Sean Christopherson
2023-08-09T14:24:00Z

On Wed, Aug 09, 2023, Joao Martins wrote:
> On 09/08/2023 00:31, Sean Christopherson wrote:
> > Fix a bug where KVM doesn't set the pCPU affinity for running vCPUs when
> > updating IRTE routing. Not setting the pCPU means the IOMMU will signal
> > the wrong pCPU's doorbell until the vCPU goes through a put+load cycle.
> >
>
> Or also framed as an inefficiency that we depend on the GALog (for a running
> vCPU) for interrupt delivery until the put+load cycle happens. I don't think I
> ever reproduced the missed interrupt case in our stress testing.

Ah, I'll reword the changelog in patch 2 if this only delays the interrupt instead
of dropping it entirely.

> > I waffled for far too long between making this one patch or two. Moving
> > the lock doesn't make all that much sense as a standalone patch, but in the
> > end, I decided that isolating the locking change would be useful in the
> > unlikely event that it breaks something. If anyone feels strongly about
> > making this a single patch, I have no objection to squashing these together.
> >
> IMHO, as two patches looks better;
>
> For what is worth:
>
> Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
>
> I think Alejandro had reported his testing as successful here:
>
> https://lore.kernel.org/kvm/caefe41b-2736-3df9-b5cd-b81fc4c30ff0@oracle.com/
>
> OTOH, he didn't give the Tested-by explicitly

Yeah, I almost asked for a Tested-by, but figured it would be just as easy to
post the patches.