Re: [PATCH v3 11/11] vfio/ccw: Move FSM open/close to MDEV open/close

Matthew Rosato <mjrosato@xxxxxxxxxxxxx> · Tue, 5 Jul 2022 16:17:04 -0400

On 6/30/22 4:36 PM, Eric Farman wrote:
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@xxxxxxxxxx>
Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>

---
  drivers/s390/cio/vfio_ccw_drv.c | 11 +++--------
  drivers/s390/cio/vfio_ccw_fsm.c | 32 +++++++++++++++++++++++---------
  drivers/s390/cio/vfio_ccw_ops.c | 26 +++++++++++---------------
  3 files changed, 37 insertions(+), 32 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index f98c9915e73d..4804101ccb0f 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -138,7 +138,7 @@ static struct vfio_ccw_private *vfio_ccw_alloc_private(struct subchannel *sch)
  
  	private->sch = sch;
  	mutex_init(&private->io_mutex);
-	private->state = VFIO_CCW_STATE_NOT_OPER;
+	private->state = VFIO_CCW_STATE_STANDBY;
  	INIT_LIST_HEAD(&private->crw);
  	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
  	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
@@ -222,21 +222,15 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
  
  	dev_set_drvdata(&sch->dev, private);
  
-	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_OPEN);
-	if (private->state == VFIO_CCW_STATE_NOT_OPER)
-		goto out_free;
-
  	ret = mdev_register_device(&sch->dev, &vfio_ccw_mdev_driver);
  	if (ret)
-		goto out_disable;
+		goto out_free;
  
  	VFIO_CCW_MSG_EVENT(4, "bound to subchannel %x.%x.%04x\n",
  			   sch->schid.cssid, sch->schid.ssid,
  			   sch->schid.sch_no);
  	return 0;
  
-out_disable:
-	cio_disable_subchannel(sch);
  out_free:
  	dev_set_drvdata(&sch->dev, NULL);
  	vfio_ccw_free_private(private);
@@ -264,6 +258,7 @@ static void vfio_ccw_sch_shutdown(struct subchannel *sch)
  	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
  
  	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
  }
  
  /**
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index 89eb3feffa41..472e77f1bb6e 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -175,6 +175,7 @@ static void fsm_notoper(struct vfio_ccw_private *private,
  	 */
  	css_sched_sch_todo(sch, SCH_TODO_UNREG);
  	private->state = VFIO_CCW_STATE_NOT_OPER;
+	cp_free(&private->cp);
  }
  
  /*
@@ -379,9 +380,16 @@ static void fsm_open(struct vfio_ccw_private *private,
  	spin_lock_irq(sch->lock);
  	sch->isc = VFIO_CCW_ISC;
  	ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch);
-	if (!ret)
-		private->state = VFIO_CCW_STATE_STANDBY;
+	if (ret)
+		goto err_unlock;
+
+	private->state = VFIO_CCW_STATE_IDLE;
  	spin_unlock_irq(sch->lock);
+	return;
+
+err_unlock:
+	spin_unlock_irq(sch->lock);
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
  }
  
  static void fsm_close(struct vfio_ccw_private *private,
@@ -393,16 +401,22 @@ static void fsm_close(struct vfio_ccw_private *private,
  	spin_lock_irq(sch->lock);
  
  	if (!sch->schib.pmcw.ena)
-		goto out_unlock;
+		goto err_unlock;
  
  	ret = cio_disable_subchannel(sch);
  	if (ret == -EBUSY)
  		vfio_ccw_sch_quiesce(sch);
+	if (ret)
+		goto err_unlock;
  
-out_unlock:
-	private->state = VFIO_CCW_STATE_NOT_OPER;
+	private->state = VFIO_CCW_STATE_STANDBY;
  	spin_unlock_irq(sch->lock);
  	cp_free(&private->cp);
+	return;
+
+err_unlock:
+	spin_unlock_irq(sch->lock);
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
  }
  
  /*
@@ -414,16 +428,16 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
  		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_error,
  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
-		[VFIO_CCW_EVENT_OPEN]		= fsm_open,
+		[VFIO_CCW_EVENT_OPEN]		= fsm_nop,
  		[VFIO_CCW_EVENT_CLOSE]		= fsm_nop,
  	},
  	[VFIO_CCW_STATE_STANDBY] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
  		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_error,
-		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
-		[VFIO_CCW_EVENT_OPEN]		= fsm_notoper,
-		[VFIO_CCW_EVENT_CLOSE]		= fsm_close,
+		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
+		[VFIO_CCW_EVENT_OPEN]		= fsm_open,
+		[VFIO_CCW_EVENT_CLOSE]		= fsm_notoper,
  	},
  	[VFIO_CCW_STATE_IDLE] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
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);
  }







