[PATCH V4 7/9] virtio: allow to unbreak virtqueue

[Jason Wang]

This patch allows the new introduced __virtio_break_device() to
unbreak the virtqueue.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Halil Pasic <pasic@xxxxxxxxxxxxx>
Cc: Cornelia Huck <cohuck@xxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 21 +++++++++++++++++++++
 include/linux/virtio.h       |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cfb028ca238e..5b7df7c455f0 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2397,6 +2397,27 @@ void virtio_break_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(virtio_break_device);
 
+/*
+ * This should allow the device to be used by the driver. You may
+ * need to grab appropriate locks to flush. This should only be used
+ * in some specific case e.g (probing and restoring). Driver should
+ * not call this directly.
+ */
+void __virtio_unbreak_device(struct virtio_device *dev)
+{
+	struct virtqueue *_vq;
+
+	spin_lock(&dev->vqs_list_lock);
+	list_for_each_entry(_vq, &dev->vqs, list) {
+		struct vring_virtqueue *vq = to_vvq(_vq);
+
+		/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
+		WRITE_ONCE(vq->broken, false);
+	}
+	spin_unlock(&dev->vqs_list_lock);
+}
+EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
+
 dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 5464f398912a..d8fdf170637c 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -131,6 +131,7 @@ void unregister_virtio_device(struct virtio_device *dev);
 bool is_virtio_device(struct device *dev);
 
 void virtio_break_device(struct virtio_device *dev);
+void __virtio_unbreak_device(struct virtio_device *dev);
 
 void virtio_config_changed(struct virtio_device *dev);
 #ifdef CONFIG_PM_SLEEP
-- 
2.25.1