linux-kernel - Re: [PATCH v9 28/44] arm64: mte: Reset the page tag in page->flags

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Date:   Thu, 12 Nov 2020 09:31:31 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 28/44] arm64: mte: Reset the page tag in page->flags

On Tue, Nov 10, 2020 at 11:10:25PM +0100, Andrey Konovalov wrote:
> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
> index 70a71f38b6a9..f0efa4847e2f 100644
> --- a/arch/arm64/mm/copypage.c
> +++ b/arch/arm64/mm/copypage.c
> @@ -23,6 +23,7 @@ void copy_highpage(struct page *to, struct page *from)
>  
>  	if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) {
>  		set_bit(PG_mte_tagged, &to->flags);
> +		page_kasan_tag_reset(to);
>  		mte_copy_page_tags(kto, kfrom);

Any reason why this doesn't have an smp_wmb() between resetting the tags
and copying them into kto?

-- 
Catalin