Re: [PATCH] s390: Revert "s390/irq/idle: Remove psw bits early"

Vasily Gorbik
2026-03-06T11:29:01Z

On Fri, Mar 06, 2026 at 12:19:19PM +0100, Heiko Carstens wrote:
> This reverts commit d8b5cf9c63143fae54a734c41e3bb55cf3f365c7.
>
> Mikhail Zaslonko reported that linux-next doesn't boot anymore [2]. Reason
> for this is recent change [2] was supposed to slightly optimize the irq
> entry/exit path by removing some psw bits early in case of an idle exit.
>
> This however is incorrect since irqentry_exit() requires the correct old
> psw state at irq entry. Otherwise the embedded regs_irqs_disabled() will
> not provide the correct result.
>
> With linux-next and HRTIMER_REARM_DEFERRED this leads to the observed boot
> problems, however the commit is broken in any case.
>
> Revert the commit which introduced this.
>
> Thanks to Peter Zijlstra for pointing out that this is a bug in the s390
> entry code.
>
> Fixes: d8b5cf9c6314 ("s390/irq/idle: Remove psw bits early") [1]
> Reported-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
> Reported-by: Peter Zijlstra <peterz@infradead.org>
> Closes: https://lore.kernel.org/r/af549a19-db99-4b16-8511-bf315177a13e@linux.ibm.com/ [2]
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
> arch/s390/kernel/irq.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)

Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Applied, thank you!