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

Joao Martins
2023-08-09T10:30:51Z

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.

> 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