[PATCH v2 03/10] vfio: ccw: new SCH_EVENT event

[Pierre Morel]

The Sub channel event callback may be called with interrupt
or thread context.
Let's thread the FSM action using workqueues.

The update of the SCHIB is now done inside an FSM action.
using the VFIO_CCW_EVENT_SCHIB_CHANGED event to guaranty
coherency with other FSM events.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
---
 drivers/s390/cio/vfio_ccw_drv.c     | 33 ++++++++++++---------------------
 drivers/s390/cio/vfio_ccw_fsm.c     | 23 +++++++++++++++++++++++
 drivers/s390/cio/vfio_ccw_private.h |  3 +++
 3 files changed, 38 insertions(+), 21 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 57ae1ab..6b7112e 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -77,6 +77,14 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 		private->state = VFIO_CCW_STATE_IDLE;
 }
 
+static void vfio_ccw_sch_event_todo(struct work_struct *work)
+{
+	struct vfio_ccw_private *private;
+
+	private = container_of(work, struct vfio_ccw_private, event_work);
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_SCHIB_CHANGED);
+}
+
 /*
  * Css driver callbacks
  */
@@ -124,6 +132,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 		goto out_disable;
 
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
+	INIT_WORK(&private->event_work, vfio_ccw_sch_event_todo);
 	atomic_set(&private->avail, 1);
 	private->state = VFIO_CCW_STATE_STANDBY;
 
@@ -170,28 +179,10 @@ static void vfio_ccw_sch_shutdown(struct subchannel *sch)
 static int vfio_ccw_sch_event(struct subchannel *sch, int process)
 {
 	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
-	unsigned long flags;
-
-	spin_lock_irqsave(sch->lock, flags);
-	if (!device_is_registered(&sch->dev))
-		goto out_unlock;
 
-	if (work_pending(&sch->todo_work))
-		goto out_unlock;
-
-	if (cio_update_schib(sch)) {
-		vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
-		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;
-	}
-
-out_unlock:
-	spin_unlock_irqrestore(sch->lock, flags);
+	if (work_pending(&private->event_work))
+		return -EAGAIN;
+	queue_work(vfio_ccw_work_q, &private->event_work);
 
 	return 0;
 }
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index 756effb..2bc4be66 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -190,6 +190,24 @@ static int fsm_irq(struct vfio_ccw_private *private,
 }
 
 /*
+ * Got a sub-channel event .
+ */
+static int fsm_sch_event(struct vfio_ccw_private *private,
+			 enum vfio_ccw_event event)
+{
+	unsigned long flags;
+	int ret = private->state;
+	struct subchannel *sch = private->sch;
+
+	spin_lock_irqsave(sch->lock, flags);
+	if (cio_update_schib(sch))
+		ret = VFIO_CCW_STATE_NOT_OPER;
+	spin_unlock_irqrestore(sch->lock, flags);
+
+	return ret;
+}
+
+/*
  * Device statemachine
  */
 fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
@@ -197,25 +215,30 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
 		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_nop,
 		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
 		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
+		[VFIO_CCW_EVENT_SCHIB_CHANGED]	= fsm_nop,
 	},
 	[VFIO_CCW_STATE_STANDBY] = {
 		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
 		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
 		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
+		[VFIO_CCW_EVENT_SCHIB_CHANGED]	= fsm_sch_event,
 	},
 	[VFIO_CCW_STATE_IDLE] = {
 		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
 		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_request,
 		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
+		[VFIO_CCW_EVENT_SCHIB_CHANGED]	= fsm_sch_event,
 	},
 	[VFIO_CCW_STATE_BOXED] = {
 		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
 		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,
 		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
+		[VFIO_CCW_EVENT_SCHIB_CHANGED]	= fsm_sch_event,
 	},
 	[VFIO_CCW_STATE_BUSY] = {
 		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
 		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,
 		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
+		[VFIO_CCW_EVENT_SCHIB_CHANGED]	= fsm_sch_event,
 	},
 };
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index f526b18..a2be0c9 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -33,6 +33,7 @@
  * @scsw: scsw info
  * @io_trigger: eventfd ctx for signaling userspace I/O results
  * @io_work: work for deferral process of I/O handling
+ * @event_work: work for deferral process of sub-channel event
  */
 struct vfio_ccw_private {
 	struct subchannel	*sch;
@@ -49,6 +50,7 @@ struct vfio_ccw_private {
 
 	struct eventfd_ctx	*io_trigger;
 	struct work_struct	io_work;
+	struct work_struct	event_work;
 } __aligned(8);
 
 extern int vfio_ccw_mdev_reg(struct subchannel *sch);
@@ -76,6 +78,7 @@ enum vfio_ccw_event {
 	VFIO_CCW_EVENT_NOT_OPER,
 	VFIO_CCW_EVENT_IO_REQ,
 	VFIO_CCW_EVENT_INTERRUPT,
+	VFIO_CCW_EVENT_SCHIB_CHANGED,
 	/* last element! */
 	NR_VFIO_CCW_EVENTS
 };
-- 
2.7.4