This is a note to let you know that I've just added the patch titled vfio/ccw: Do not change FSM state in subchannel event to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: vfio-ccw-do-not-change-fsm-state-in-subchannel-event.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 6d4d2d089985449c4dc26efb89953ba0cb18f3bf Author: Eric Farman <farman@xxxxxxxxxxxxx> Date: Thu Jul 7 15:57:29 2022 +0200 vfio/ccw: Do not change FSM state in subchannel event [ Upstream commit cffcc109fd682075dee79bade3d60a07152a8fd1 ] The routine vfio_ccw_sch_event() is tasked with handling subchannel events, specifically machine checks, on behalf of vfio-ccw. It correctly calls cio_update_schib(), and if that fails (meaning the subchannel is gone) it makes an FSM event call to mark the subchannel Not Operational. If that worked, however, then it decides that if the FSM state was already Not Operational (implying the subchannel just came back), then it should simply change the FSM to partially- or fully-open. Remove this trickery, since a subchannel returning will require more probing than simply "oh all is well again" to ensure it works correctly. Fixes: bbe37e4cb8970 ("vfio: ccw: introduce a finite state machine") Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx> Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220707135737.720765-4-farman@xxxxxxxxxxxxx Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index fd590d1cffc1..d42e5a307437 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -247,19 +247,11 @@ static int vfio_ccw_sch_event(struct subchannel *sch, int process) if (work_pending(&sch->todo_work)) goto out_unlock; - if (cio_update_schib(sch)) { - vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER); - rc = 0; - goto out_unlock; - } - - private = dev_get_drvdata(&sch->dev); - if (private->state == VFIO_CCW_STATE_NOT_OPER) { - private->state = private->mdev ? VFIO_CCW_STATE_IDLE : - VFIO_CCW_STATE_STANDBY; - } rc = 0; + if (cio_update_schib(sch)) + vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER); + out_unlock: spin_unlock_irqrestore(sch->lock, flags);