linux-kernel - Re: [PATCH mm-unstable v1 4/5] kvm/powerpc: add kvm_arch_test_clear

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Message-ID: <CAOUHufbjbaBtNQX-uSOUQEDoH9nAE0nC7L+ssoPF3WHpQuiwuw@mail.gmail.com>
Date:   Thu, 16 Feb 2023 21:24:09 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Jonathan Corbet <corbet@....net>,
        Michael Larabel <michael@...haellarabel.com>,
        kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-mm@...gle.com, Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH mm-unstable v1 4/5] kvm/powerpc: add kvm_arch_test_clear_young()

On Thu, Feb 16, 2023 at 9:12 PM Yu Zhao <yuzhao@...gle.com> wrote:
>
> This patch adds kvm_arch_test_clear_young() for the vast majority of
> VMs that are not nested and run on hardware with Radix MMU enabled.
>
> It relies on two techniques, RCU and cmpxchg, to safely test and clear
> the accessed bit without taking the MMU lock. The former protects KVM
> page tables from being freed while the latter clears the accessed bit
> atomically against both the hardware and other software page table
> walkers.
>
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> ---
>  arch/powerpc/include/asm/kvm_host.h    | 18 ++++++
>  arch/powerpc/include/asm/kvm_ppc.h     | 14 +----
>  arch/powerpc/kvm/book3s.c              |  7 +++
>  arch/powerpc/kvm/book3s.h              |  2 +
>  arch/powerpc/kvm/book3s_64_mmu_radix.c | 78 +++++++++++++++++++++++++-
>  arch/powerpc/kvm/book3s_hv.c           | 10 ++--
>  6 files changed, 110 insertions(+), 19 deletions(-)

Adding Michael, Nicholas and Christophe.

I'm not sure who I should add for this patch. Can you please add any
interested parties that I've missed?

Thank you.