Re: [PATCH v3 27/34] s390/irqflags: Do not instrument arch_local_irq_*() with KMSAN

[Alexander Potapenko]

On Thu, Dec 14, 2023 at 12:36 AM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>