vfio/ccw: Fix FSM state if mdev probe fails

The FSM is in STANDBY state when arriving in vfio_ccw_mdev_probe(),
and this routine converts it to IDLE as part of its processing.
The error exit sets it to IDLE (again) but clears the private->mdev
pointer.

The FSM should of course be managing the state itself, but the
correct thing for vfio_ccw_mdev_probe() to do would be to put
the state back the way it found it.

The corresponding check of private->mdev in vfio_ccw_sch_io_todo()
can be removed, since the distinction is unnecessary at this point.

Fixes: 3bf1311f ("vfio/ccw: Convert to use vfio_register_emulated_iommu_dev()")
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20220707135737.720765-3-farman@linux.ibm.comSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/s390/cio/vfio_ccw_drv.c

@@ -106,9 +106,10 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 	/*
 	 * Reset to IDLE only if processing of a channel program
 	 * has finished. Do not overwrite a possible processing
-	 * state if the final interrupt was for HSCH or CSCH.
+	 * state if the interrupt was unsolicited, or if the final
+	 * interrupt was for HSCH or CSCH.
 	 */
-	if (private->mdev && cp_is_finished)
+	if (cp_is_finished)
 		private->state = VFIO_CCW_STATE_IDLE;
 
 	if (private->io_trigger)

drivers/s390/cio/vfio_ccw_ops.c

@@ -146,7 +146,7 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
 	vfio_uninit_group_dev(&private->vdev);
 	atomic_inc(&private->avail);
 	private->mdev = NULL;
-	private->state = VFIO_CCW_STATE_IDLE;
+	private->state = VFIO_CCW_STATE_STANDBY;
 	return ret;
 }