linux-kernel - Re: [PATCH v10-mte 4/7] arm64: mte: implement CONFIG_ARM64_MTE

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Message-ID: <CAG_fn=WcrNqV4burBRPZZwoBLwgia7kerZ8g2vV5spzWF=houQ@mail.gmail.com>
Date: Fri, 15 Dec 2023 16:19:27 +0100
From: Alexander Potapenko <glider@...gle.com>
To: Yury Norov <yury.norov@...il.com>
Cc: catalin.marinas@....com, will@...nel.org, pcc@...gle.com, 
	andreyknvl@...il.com, andriy.shevchenko@...ux.intel.com, 
	aleksander.lobakin@...el.com, linux@...musvillemoes.dk, 
	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 v10-mte 4/7] arm64: mte: implement CONFIG_ARM64_MTE_COMP

>
> That looks weird... You're casting address of a 'data' to a bitmap
> instead of 'data'. At the 1st glance it makes little sense because
> 'data' is passed as parameter. Moreover, in mte_is_compressed()
> you pass 'data', not '&data'. Can you please comment on your
> intention?

Although `data` is a void*, it actually contains 64 bits of compressed
data, so we pass &data to mte_bitmap_read() to read its contents.
Perhaps I'd better make `data` an unsigned long to avoid confusion.

>
> > +     max_ranges = MTE_MAX_RANGES;
> > +     /* Skip the leading bit indicating the inline case. */
> > +     mte_bitmap_read(bitmap, &bit_pos, 1);
> > +     largest_idx =
> > +             mte_bitmap_read(bitmap, &bit_pos, MTE_BITS_PER_LARGEST_IDX);
>
> Nit: really no need to split the line - we're OK with 100-chars per
> line now.

That's true, but I am relying on clang-format here (maybe we should
extend the limit in .clang-format?)