virtio: allow to unbreak virtqueue

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

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Vineeth Vijayan <vneethv@linux.ibm.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220527060120.20964-8-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 9d0bae4293be799c1dd25a0b7c877882c786984b..9c231e1fded7359a3719234849bd7a70b4c5cdb6 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2395,6 +2395,28 @@ 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 the write to
+ * vq->broken. This should only be used in some specific case e.g
+ * (probing and restoring). This function should only be called by the
+ * core, not directly by the driver.
+ */
+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 5464f398912a5fea9db9c68b630648a4e5709a46..d8fdf170637c9a11b317e7795fff7fe0b8c12ee8 100644 (file)
--- 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