linux-kernel - [PATCH 5.15 594/779] vfio/ccw: Do not change FSM state in subchannel event

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Date:   Mon, 15 Aug 2022 20:03:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Farman <farman@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 594/779] vfio/ccw: Do not change FSM state in subchannel event

From: Eric Farman <farman@...ux.ibm.com>

[ 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@...ux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
Link: https://lore.kernel.org/r/20220707135737.720765-4-farman@linux.ibm.com
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/s390/cio/vfio_ccw_drv.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 76099bcb765b..b9091e22ca57 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -287,19 +287,11 @@ 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);
 
-- 
2.35.1