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References: <20231115203401.2495875-1-iii@linux.ibm.com> <20231115203401.2495875-20-iii@linux.ibm.com>
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From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 16 Nov 2023 11:33:43 +0100
Message-ID: <CAG_fn=VMKwcsBL4KuRYG-dojpZg0WFqJgZc67ks5Rg-HEnd2bQ@mail.gmail.com>
Subject: Re: [PATCH 19/32] kmsan: Accept ranges starting with 0 on s390
To:     Ilya Leoshkevich <iii@linux.ibm.com>
Cc:     Alexander Gordeev <agordeev@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-s390@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>
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On Wed, Nov 15, 2023 at 9:34=E2=80=AFPM Ilya Leoshkevich <iii@linux.ibm.com=
> wrote:
>
> On s390 the virtual address 0 is valid (current CPU's lowcore is mapped
> there), therefore KMSAN should not complain about it.
>
> Disable the respective check on s390. There doesn't seem to be a
> Kconfig option to describe this situation, so explicitly check for
> s390.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
(see the nit below)

> ---
>  mm/kmsan/init.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/kmsan/init.c b/mm/kmsan/init.c
> index ffedf4dbc49d..14f4a432fddd 100644
> --- a/mm/kmsan/init.c
> +++ b/mm/kmsan/init.c
> @@ -33,7 +33,9 @@ static void __init kmsan_record_future_shadow_range(voi=
d *start, void *end)
>         bool merged =3D false;
>
>         KMSAN_WARN_ON(future_index =3D=3D NUM_FUTURE_RANGES);
> -       KMSAN_WARN_ON((nstart >=3D nend) || !nstart || !nend);
> +       KMSAN_WARN_ON((nstart >=3D nend) ||
> +                     (!IS_ENABLED(CONFIG_S390) && !nstart) ||
Please add a comment explaining this bit.

> +                     !nend);
>         nstart =3D ALIGN_DOWN(nstart, PAGE_SIZE);
>         nend =3D ALIGN(nend, PAGE_SIZE);
>
> --
> 2.41.0
>