linux-kernel - Re: [PATCH mm v3 18/19] kasan, mm: allow cache merging with no metadata

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Date:   Mon, 23 Nov 2020 14:52:44 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....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>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH mm v3 18/19] kasan, mm: allow cache merging with no metadata

On Tue, Nov 17, 2020 at 2:25 PM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> On Fri, Nov 13, 2020 at 11:20 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
> >
> > The reason cache merging is disabled with KASAN is because KASAN puts its
> > metadata right after the allocated object. When the merged caches have
> > slightly different sizes, the metadata ends up in different places, which
> > KASAN doesn't support.
> >
> > It might be possible to adjust the metadata allocation algorithm and make
> > it friendly to the cache merging code. Instead this change takes a simpler
> > approach and allows merging caches when no metadata is present. Which is
> > the case for hardware tag-based KASAN with kasan.mode=prod.
> >
> > Co-developed-by: Vincenzo Frascino <Vincenzo.Frascino@....com>
> > Signed-off-by: Vincenzo Frascino <Vincenzo.Frascino@....com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > Link: https://linux-review.googlesource.com/id/Ia114847dfb2244f297d2cb82d592bf6a07455dba
>
> Somehow gerrit contains an old version... so I was going to
> independently propose what Marco already proposed as simplification...
> until I looked at the patch in the email :)

Ah, this is because I couldn't push next/mm-based changes into Gerrit
without manually adding tags to all of the yet-out-of-tree patches. So
the Gerrit doesn't have the last version of the patchset.

> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>

Thanks!