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

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Date:   Wed, 9 Aug 2023 11:30:03 +0100
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Alejandro Jimenez <alejandro.j.jimenez@...cle.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        "dengqiao . joey" <dengqiao.joey@...edance.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 0/2] KVM: SVM: Set pCPU during IRTE update if vCPU is
 running

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@...cle.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