linux-kernel - Re: [PATCH v9 1/4] arm64: mte: implement CONFIG_ARM64_MTE

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Message-ID: <CAG_fn=X60dDWKAC6Yswr3RCW15Jpd8BOtRCYP-ijCDZZDzo14A@mail.gmail.com>
Date:   Thu, 14 Dec 2023 10:27:12 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>, pcc@...gle.com,
        andreyknvl@...il.com, andriy.shevchenko@...ux.intel.com,
        aleksander.lobakin@...el.com, linux@...musvillemoes.dk,
        yury.norov@...il.com, alexandru.elisei@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        eugenis@...gle.com, syednwaris@...il.com, william.gray@...aro.org
Subject: Re: [PATCH v9 1/4] arm64: mte: implement CONFIG_ARM64_MTE_COMP

On Wed, Dec 13, 2023 at 1:16 PM Will Deacon <will@...nel.org> wrote:
>
> On Tue, Dec 12, 2023 at 05:16:15PM +0000, Catalin Marinas wrote:
> > On Mon, Nov 13, 2023 at 11:52:30AM +0100, Alexander Potapenko wrote:
> > > The config implements the algorithm compressing memory tags for ARM MTE
> > > during swapping.
> > >
> > > The algorithm is based on RLE and specifically targets buffers of tags
> > > corresponding to a single page. In many cases a buffer can be compressed
> > > into 63 bits, making it possible to store it without additional memory
> > > allocation.
> > >
> > > Suggested-by: Evgenii Stepanov <eugenis@...gle.com>
> > > Signed-off-by: Alexander Potapenko <glider@...gle.com>
> >
> > Acked-by: Catalin Marinas <catalin.marinas@....com>
> >
> > > +void mte_tags_to_ranges(u8 *tags, u8 *out_tags, unsigned short *out_sizes,
> > > +                   size_t *out_len)
> > > +{
> > [...]
> > > +}
> > > +EXPORT_SYMBOL_NS(mte_tags_to_ranges, MTECOMP);
> >
> > I may have asked before, what the reason for EXPORT_SYMBOL_NS? Is it for
> > the kunit tests? Otherwise we don't expect those to be accessed from
> > modules.
>
> It looks like it. The Kconfig option for the test is tristate and it calls
> this symbol directly.
>
> Will

What Will said.