[PATCH vhost 01/22] virtio_ring: virtqueue_set_dma_premapped support disable

[Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>]

virtqueue_set_dma_premapped() adds a new parameter to disable the
virtqueue premapped mode.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c     |  2 +-
 drivers/virtio/virtio_ring.c | 11 ++++++++---
 include/linux/virtio.h       |  2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fe7f314d65c9..6b5f47ebf9b2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -737,7 +737,7 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
 		return;
 
 	for (i = 0; i < vi->max_queue_pairs; i++) {
-		if (virtqueue_set_dma_premapped(vi->rq[i].vq))
+		if (virtqueue_set_dma_premapped(vi->rq[i].vq, true))
 			continue;
 
 		vi->rq[i].do_dma = true;
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 51d8f3299c10..b3ded56722f4 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2784,7 +2784,7 @@ EXPORT_SYMBOL_GPL(virtqueue_resize);
  * 0: success.
  * -EINVAL: vring does not use the dma api, so we can not enable premapped mode.
  */
-int virtqueue_set_dma_premapped(struct virtqueue *_vq)
+int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool mode)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	u32 num;
@@ -2803,8 +2803,13 @@ int virtqueue_set_dma_premapped(struct virtqueue *_vq)
 		return -EINVAL;
 	}
 
-	vq->premapped = true;
-	vq->do_unmap = false;
+	if (mode) {
+		vq->premapped = true;
+		vq->do_unmap = false;
+	} else {
+		vq->premapped = false;
+		vq->do_unmap = vq->use_dma_api;
+	}
 
 	END_USE(vq);
 
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 4cc614a38376..1cf7b004348b 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -81,7 +81,7 @@ bool virtqueue_enable_cb(struct virtqueue *vq);
 
 unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq);
 
-int virtqueue_set_dma_premapped(struct virtqueue *_vq);
+int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool mode);
 
 bool virtqueue_poll(struct virtqueue *vq, unsigned);
 
-- 
2.32.0.3.g01195cf9f