[PATCH v2 6/7] s390/vfio_ccw: implement a channel program lock

[Eric Farman <farman@linux.ibm.com>]

The channel_program struct is manipulated without a serialization
mechanism to ensure consistent behavior. Take a broad stroke of
putting the entire structure behind a spin lock, which can be
acquired with or without the mutex guarding the I/O regions that
feed into the population of the channel program.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
 drivers/s390/cio/vfio_ccw_cp.c      | 13 ++++++++++++-
 drivers/s390/cio/vfio_ccw_cp.h      |  1 +
 drivers/s390/cio/vfio_ccw_drv.c     |  6 +++++-
 drivers/s390/cio/vfio_ccw_ops.c     |  8 +++++++-
 drivers/s390/cio/vfio_ccw_private.h |  2 ++
 5 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index c6f0264fb5d3..7bfb3a952817 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -790,7 +790,7 @@ int cp_init(struct channel_program *cp, union orb *orb)
  * @cp, which must have been returned by a previous call to cp_init().
  * Otherwise, undefined behavior occurs.
  */
-void cp_free(struct channel_program *cp)
+void cp_free_locked(struct channel_program *cp)
 {
 	struct vfio_device *vdev =
 		&container_of(cp, struct vfio_ccw_private, cp)->vdev;
@@ -810,6 +810,17 @@ void cp_free(struct channel_program *cp)
 	}
 }
 
+void cp_free(struct channel_program *cp)
+{
+	struct vfio_ccw_private *private =
+		container_of(cp, struct vfio_ccw_private, cp);
+	unsigned long flags;
+
+	spin_lock_irqsave(&private->cp_lock, flags);
+	cp_free_locked(cp);
+	spin_unlock_irqrestore(&private->cp_lock, flags);
+}
+
 /**
  * cp_prefetch() - translate a guest physical address channel program to
  *                 a real-device runnable channel program.
diff --git a/drivers/s390/cio/vfio_ccw_cp.h b/drivers/s390/cio/vfio_ccw_cp.h
index d547dbc969cc..edfb47a292ca 100644
--- a/drivers/s390/cio/vfio_ccw_cp.h
+++ b/drivers/s390/cio/vfio_ccw_cp.h
@@ -48,6 +48,7 @@ struct channel_program {
 };
 
 int cp_init(struct channel_program *cp, union orb *orb);
+void cp_free_locked(struct channel_program *cp);
 void cp_free(struct channel_program *cp);
 int cp_prefetch(struct channel_program *cp);
 union orb *cp_get_orb(struct channel_program *cp, struct subchannel *sch);
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 1a095085bc72..bfb68de6e52c 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -83,6 +83,7 @@ void vfio_ccw_sch_io_todo(struct work_struct *work)
 {
 	struct vfio_ccw_private *private;
 	struct irb *irb;
+	unsigned long flags;
 	bool is_final;
 	bool cp_is_finished = false;
 
@@ -91,13 +92,16 @@ void vfio_ccw_sch_io_todo(struct work_struct *work)
 
 	is_final = !(scsw_actl(&irb->scsw) &
 		     (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT));
+	spin_lock_irqsave(&private->cp_lock, flags);
 	if (scsw_is_solicited(&irb->scsw)) {
 		cp_update_scsw(&private->cp, &irb->scsw);
 		if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) {
-			cp_free(&private->cp);
+			cp_free_locked(&private->cp);
 			cp_is_finished = true;
 		}
 	}
+	spin_unlock_irqrestore(&private->cp_lock, flags);
+
 	mutex_lock(&private->io_mutex);
 	memcpy(private->io_region->irb_area, irb, sizeof(*irb));
 	mutex_unlock(&private->io_mutex);
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index e695cd985369..d2475b3158cf 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -36,10 +36,15 @@ static void vfio_ccw_dma_unmap(struct vfio_device *vdev, u64 iova, u64 length)
 {
 	struct vfio_ccw_private *private =
 		container_of(vdev, struct vfio_ccw_private, vdev);
+	unsigned long flags;
 
 	/* Drivers MUST unpin pages in response to an invalidation. */
-	if (!cp_iova_pinned(&private->cp, iova, length))
+	spin_lock_irqsave(&private->cp_lock, flags);
+	if (!cp_iova_pinned(&private->cp, iova, length)) {
+		spin_unlock_irqrestore(&private->cp_lock, flags);
 		return;
+	}
+	spin_unlock_irqrestore(&private->cp_lock, flags);
 
 	vfio_ccw_mdev_reset(private);
 }
@@ -54,6 +59,7 @@ static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev)
 	INIT_LIST_HEAD(&private->crw);
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
 	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
+	spin_lock_init(&private->cp_lock);
 
 	private->cp.guest_cp = kzalloc_objs(struct ccw1, CCWCHAIN_LEN_MAX);
 	if (!private->cp.guest_cp)
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 0501d4bbcdbd..061b594fde36 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -115,7 +115,9 @@ struct vfio_ccw_private {
 	struct ccw_crw_region	*crw_region;
 	int num_regions;
 
+	spinlock_t		cp_lock;
 	struct channel_program	cp;
+
 	struct irb		irb;
 	union scsw		scsw;
 	struct list_head	crw;
-- 
2.53.0