linux-kernel - Re: [PATCH mm-unstable v2 02/10] mm/kvm: use mmu_notifier_ops->test_clear

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Message-ID: <ZHed6OuO/ALNfvaX@ziepe.ca>
Date:   Wed, 31 May 2023 16:20:08 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Alistair Popple <apopple@...dia.com>,
        Anup Patel <anup@...infault.org>,
        Ben Gardon <bgardon@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Gaosheng Cui <cuigaosheng1@...wei.com>,
        Gavin Shan <gshan@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Jonathan Corbet <corbet@....net>,
        Marc Zyngier <maz@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Larabel <michael@...haellarabel.com>,
        Mike Rapoport <rppt@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Paul Mackerras <paulus@...abs.org>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thomas Huth <thuth@...hat.com>, Will Deacon <will@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>, kvmarm@...ts.linux.dev,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-trace-kernel@...r.kernel.org, x86@...nel.org,
        linux-mm@...gle.com
Subject: Re: [PATCH mm-unstable v2 02/10] mm/kvm: use
 mmu_notifier_ops->test_clear_young()

On Fri, May 26, 2023 at 05:44:27PM -0600, Yu Zhao wrote:
> Replace test_young() and clear_young() with test_clear_young().
> 
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> ---
>  include/linux/mmu_notifier.h | 29 ++-----------------
>  include/trace/events/kvm.h   | 15 ----------
>  mm/mmu_notifier.c            | 42 ----------------------------
>  virt/kvm/kvm_main.c          | 54 ------------------------------------
>  4 files changed, 2 insertions(+), 138 deletions(-)
> 
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index dfdbb370682d..c8f35fc08703 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -104,26 +104,6 @@ struct mmu_notifier_ops {
>  				 unsigned long start,
>  				 unsigned long end);
>  
> -	/*
> -	 * clear_young is a lightweight version of clear_flush_young. Like the
> -	 * latter, it is supposed to test-and-clear the young/accessed bitflag
> -	 * in the secondary pte, but it may omit flushing the secondary tlb.
> -	 */
> -	int (*clear_young)(struct mmu_notifier *subscription,
> -			   struct mm_struct *mm,
> -			   unsigned long start,
> -			   unsigned long end);
> -
> -	/*
> -	 * test_young is called to check the young/accessed bitflag in
> -	 * the secondary pte. This is used to know if the page is
> -	 * frequently used without actually clearing the flag or tearing
> -	 * down the secondary mapping on the page.
> -	 */
> -	int (*test_young)(struct mmu_notifier *subscription,
> -			  struct mm_struct *mm,
> -			  unsigned long address);
> -
>  	int (*test_clear_young)(struct mmu_notifier *mn, struct mm_struct *mm,
>  				unsigned long start, unsigned long end,
>  				bool clear, unsigned long *bitmap);

Oh, you split the patch. This MMU notifier stuff seems OK for both
patches then, and KVM is the only user:

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason