Re: [PATCH v1 3/3] KVM: arm64: Using rcu_read_lock() for kvm_pgtable_stage2_mkyoung()

[Chun-Tse Shao]

On Fri, Jun 9, 2023 at 12:44 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
>
> On Thu, 08 Jun 2023 23:05:41 +0100,
> Chun-Tse Shao <ctshao@xxxxxxxxxx> wrote:
> >
> > Access bit is RCU safe and can be set without taking kvm->mmu_lock().
>
> Please explain why. What happens when the page tables are *not* RCU
> controlled, such as in the pKVM case?
>
> > Replacing existing kvm->mmu_lock() with rcu_read_lock() for better
> > performance.
>
> Please define "better performance", quote workloads, figures, HW setup
> and point to a reproducer. Please add a cover letter to your patch
> series explaining the context this happens in.

Thanks for the suggestion, we are currently working on the performance
test in parallel and will update after gathering more data.

>
> Also, I'm getting increasingly annoyed by the lack of coordination
> between seamingly overlapping patch series (this, Yu's, Anish's and
> Vipin's), all from a single company.
>
> Surely you can talk to each other and devise a coordinated approach?

Sure, I will start internal meeting as needed.

>
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.

Thanks,
CT