linux-kernel - Re: [PATCH v2] kasan: fix mention for KASAN_HW

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Message-ID: <CA+fCnZfrUY+EZ8w6zDhfjOr=JSFS6bHO7JjVHx0pEykNXZQecg@mail.gmail.com>
Date:   Fri, 23 Jun 2023 14:40:28 +0200
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Chanho Min <chanho.min@....com>
Cc:     dvyukov@...gle.com, elver@...gle.com, glider@...gle.com,
        gunho.lee@....com, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        ryabinin.a.a@...il.com, vincenzo.frascino@....com
Subject: Re: [PATCH v2] kasan: fix mention for KASAN_HW_TAGS

On Fri, Jun 23, 2023 at 9:58 AM Chanho Min <chanho.min@....com> wrote:
>
> This patch fixes description of the KASAN_HW_TAGS's memory consumption.
> KASAN_HW_TAGS are dependent on the HW implementation and are not reserved
> from system memory like shadow memory.
>
> Suggested-by: Andrey Konovalov <andreyknvl@...il.com>
> Signed-off-by: Chanho Min <chanho.min@....com>
> ---
>  lib/Kconfig.kasan | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index fdca89c05745..f8f9e12510b7 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -124,7 +124,8 @@ config KASAN_HW_TAGS
>           Supported only on arm64 CPUs starting from ARMv8.5 and relies on
>           Memory Tagging Extension and Top Byte Ignore.
>
> -         Consumes about 1/32nd of available memory.
> +         Does not consume memory by itself but relies on the 1/32nd of
> +         available memory being reserved by the firmware when MTE is enabled.
>
>           May potentially introduce problems related to pointer casting and
>           comparison, as it embeds a tag into the top byte of each pointer.
> --
> 2.17.1
>

Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>

Thank you!