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Tue, 20 Jun 2023 09:33:01 -0700 (PDT) MIME-Version: 1.0 References: <20230619101224.22978-1-chanho.min@lge.com> In-Reply-To: From: Andrey Konovalov Date: Tue, 20 Jun 2023 18:32:50 +0200 Message-ID: Subject: Re: [PATCH] kasan: fix mention for KASAN_HW_TAGS To: Marco Elver , Chanho Min Cc: Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Vincenzo Frascino , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, gunho.lee@lge.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 02DA720007 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 1m5nqj4bwca1aco37fcafuxnhnej6e8z X-HE-Tag: 1687278781-532327 X-HE-Meta: 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 19wFdtT5 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 19, 2023 at 1:36=E2=80=AFPM Marco Elver wrot= e: > > On Mon, 19 Jun 2023 at 12:15, Dmitry Vyukov wrote: > > On Mon, 19 Jun 2023 at 12:12, Chanho Min wrote: > > > > > > This patch removes description of the KASAN_HW_TAGS's memory consumpt= ion. > > > KASAN_HW_TAGS does not set 1/32nd shadow memory. > > > > The hardware still allocates/uses shadow in MTE. > > Though, it may be 1/16-th, not sure. 1/32 is correct: 4 bits for every 16 bytes. > I think the point is that it depends on the hardware implementation of > MTE. There are a range of possibilities, but enabling KASAN_HW_TAGS > doesn't consume any extra memory for tags itself if the hardware has > to enable MTE and provision tag space via firmware to begin with. Yeah, saying that HW_TAGS consumes memory is wrong. But it might reasonable to spell out what happens with memory in the config options description. Something like: "Does not consume memory by itself but relies on the 1/32nd of available memory being reserved by the firmware when MTE is enabled."