Received-SPF: pass (google.com: domain of linux-kernel+bounces-9662-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Precedence: bulk
MIME-Version: 1.0
References: <20231213233605.661251-1-iii@linux.ibm.com> <20231213233605.661251-28-iii@linux.ibm.com>
In-Reply-To: <20231213233605.661251-28-iii@linux.ibm.com>
From: Alexander Potapenko <glider@google.com>
Date: Fri, 22 Dec 2023 12:27:50 +0100
Message-ID: <CAG_fn=VfYNpMynQtXiKemoDy3LjH5Hn8N-VpzH6AGVZ3jDHPUQ@mail.gmail.com>
Subject: Re: [PATCH v3 27/34] s390/irqflags: Do not instrument
 arch_local_irq_*() with KMSAN
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>, Heiko Carstens <hca@linux.ibm.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>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Thu, Dec 14, 2023 at 12:36=E2=80=AFAM Ilya Leoshkevich <iii@linux.ibm.co=
m> wrote:
>
> KMSAN generates the following false positives on s390x:
>
> [    6.063666] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
> [         ...]
> [    6.577050] Call Trace:
> [    6.619637]  [<000000000690d2de>] check_flags+0x1fe/0x210
> [    6.665411] ([<000000000690d2da>] check_flags+0x1fa/0x210)
> [    6.707478]  [<00000000006cec1a>] lock_acquire+0x2ca/0xce0
> [    6.749959]  [<00000000069820ea>] _raw_spin_lock_irqsave+0xea/0x190
> [    6.794912]  [<00000000041fc988>] __stack_depot_save+0x218/0x5b0
> [    6.838420]  [<000000000197affe>] __msan_poison_alloca+0xfe/0x1a0
> [    6.882985]  [<0000000007c5827c>] start_kernel+0x70c/0xd50
> [    6.927454]  [<0000000000100036>] startup_continue+0x36/0x40
>
> Between trace_hardirqs_on() and `stosm __mask, 3` lockdep thinks that
> interrupts are on, but on the CPU they are still off. KMSAN
> instrumentation takes spinlocks, giving lockdep a chance to see and
> complain about this discrepancy.
>
> KMSAN instrumentation is inserted in order to poison the __mask
> variable. Disable instrumentation in the respective functions. They are
> very small and it's easy to see that no important metadata updates are
> lost because of this.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>