vfio/ccw: Move FSM open/close to MDEV open/close

Part of the confusion that has existed is the FSM lifecycle of
subchannels between the common CSS driver and the vfio-ccw driver.
During configuration, the FSM state goes from NOT_OPER to STANDBY
to IDLE, but then back to NOT_OPER. For example:

	vfio_ccw_sch_probe:		VFIO_CCW_STATE_NOT_OPER
	vfio_ccw_sch_probe:		VFIO_CCW_STATE_STANDBY
	vfio_ccw_mdev_probe:		VFIO_CCW_STATE_IDLE
	vfio_ccw_mdev_remove:		VFIO_CCW_STATE_NOT_OPER
	vfio_ccw_sch_remove:		VFIO_CCW_STATE_NOT_OPER
	vfio_ccw_sch_shutdown:		VFIO_CCW_STATE_NOT_OPER

Rearrange the open/close events to align with the mdev open/close,
to better manage the memory and state of the devices as time
progresses. Specifically, make mdev_open() perform the FSM open,
and mdev_close() perform the FSM close instead of reset (which is
both close and open).

This makes the NOT_OPER state a dead-end path, indicating the
device is probably not recoverable without fully probing and
re-configuring the device.

This has the nice side-effect of removing a number of special-cases
where the FSM state is managed outside of the FSM itself (such as
the aforementioned mdev_close() routine).

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
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/20220707135737.720765-12-farman@linux.ibm.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 11 insertions, 15 deletions

diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 4673b7ddfe20..bc2176421dc5 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -24,17 +24,12 @@ static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
 	/*
 	 * If the FSM state is seen as Not Operational after closing
 	 * and re-opening the mdev, return an error.
-	 *
-	 * Otherwise, change the FSM from STANDBY to IDLE which is
-	 * normally done by vfio_ccw_mdev_probe() in current lifecycle.
 	 */
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
 	if (private->state == VFIO_CCW_STATE_NOT_OPER)
 		return -EINVAL;
 
-	private->state = VFIO_CCW_STATE_IDLE;
-
 	return 0;
 }
 
@@ -121,8 +116,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
 	vfio_init_group_dev(&private->vdev, &mdev->dev,
 			    &vfio_ccw_dev_ops);
 
-	private->state = VFIO_CCW_STATE_IDLE;
-
 	VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: create\n",
 			   private->sch->schid.cssid,
 			   private->sch->schid.ssid,
@@ -137,7 +130,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
 err_atomic:
 	vfio_uninit_group_dev(&private->vdev);
 	atomic_inc(&private->avail);
-	private->state = VFIO_CCW_STATE_STANDBY;
 	return ret;
 }
 
@@ -165,6 +157,10 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 	unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
 	int ret;
 
+	/* Device cannot simply be opened again from this state */
+	if (private->state == VFIO_CCW_STATE_NOT_OPER)
+		return -EINVAL;
+
 	private->nb.notifier_call = vfio_ccw_mdev_notifier;
 
 	ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY,
@@ -184,6 +180,12 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 	if (ret)
 		goto out_unregister;
 
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
+	if (private->state == VFIO_CCW_STATE_NOT_OPER) {
+		ret = -EINVAL;
+		goto out_unregister;
+	}
+
 	return ret;
 
 out_unregister:
@@ -197,13 +199,7 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
 	struct vfio_ccw_private *private =
 		container_of(vdev, struct vfio_ccw_private, vdev);
 
-	if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
-	    (private->state != VFIO_CCW_STATE_STANDBY)) {
-		if (!vfio_ccw_mdev_reset(private))
-			private->state = VFIO_CCW_STATE_STANDBY;
-		/* The state will be NOT_OPER on error. */
-	}
-
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
 	vfio_ccw_unregister_dev_regions(private);
 	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
 }