linux-kernel - Re: [PATCH mm-unstable v1 2/5] kvm/x86: add kvm_arch_test_clear

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Message-ID: <CAOUHufYsiFx=AqnZ6gDCjEHq4cN6XVXF6fPRvGpaXJbbmvoCPQ@mail.gmail.com>
Date:   Thu, 16 Feb 2023 21:19:55 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        David Matlack <dmatlack@...gle.com>
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, Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH mm-unstable v1 2/5] kvm/x86: 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 that sets the accessed bit
> in TDP MMU page tables.
>
> 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/x86/include/asm/kvm_host.h | 27 ++++++++++++++++++++++
>  arch/x86/kvm/mmu/spte.h         | 12 ----------
>  arch/x86/kvm/mmu/tdp_mmu.c      | 41 +++++++++++++++++++++++++++++++++
>  3 files changed, 68 insertions(+), 12 deletions(-)

Adding Sean and David.

Can you please add other interested parties that I've missed?

Thanks.