vfio/ccw: Do not change FSM state in subchannel event

stable inclusion
from stable-v5.10.137
commit b16d653bc7bbd3dbbdaeda4e032e01ed9d8b252c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b16d653bc7bbd3dbbdaeda4e032e01ed9d8b252c

--------------------------------

[ Upstream commit cffcc109 ]

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: bbe37e4c ("vfio: ccw: introduce a finite state machine")
Signed-off-by: NEric Farman <farman@linux.ibm.com>
Reviewed-by: NMatthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20220707135737.720765-4-farman@linux.ibm.comSigned-off-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

drivers/s390/cio/vfio_ccw_drv.c

@@ -288,19 +288,11 @@ 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);