[PATCH vhost v5 10/10] virtio_ring: virtqueue_set_dma_premapped support disable

[Xuan Zhuo]

Now, the API virtqueue_set_dma_premapped just support to
enable premapped mode.

If we allow enabling the premapped dynamically, we should
make this API to support disable the premapped mode.

Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 39 +++++++++++++++++++++++++++---------
 include/linux/virtio.h       |  2 +-
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 86a60c720a62..6ddabf280218 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2792,6 +2792,7 @@ EXPORT_SYMBOL_GPL(virtqueue_resize);
 /**
  * virtqueue_set_dma_premapped - set the vring premapped mode
  * @_vq: the struct virtqueue we're talking about.
+ * @premapped: enable/disable the premapped mode.
  *
  * Enable the premapped mode of the vq.
  *
@@ -2808,11 +2809,15 @@ EXPORT_SYMBOL_GPL(virtqueue_resize);
  *
  * Returns zero or a negative error.
  * 0: success.
- * -EINVAL: vring does not use the dma api, so we can not enable premapped 
mode.
+ * -EINVAL:
+ *     vring does not use the dma api, so we can not enable premapped mode.
+ *     Or some descs are used, this is not called immediately after creating
+ *     the vq, or after vq reset.
  */
-int virtqueue_set_dma_premapped(struct virtqueue *_vq)
+int virtqueue_set_dma_premapped(struct virtqueue *_vq, bool premapped)
 {
        struct vring_virtqueue *vq = to_vvq(_vq);
+       int err = 0;
        u32 num;
 
        START_USE(vq);
@@ -2824,24 +2829,40 @@ int virtqueue_set_dma_premapped(struct virtqueue *_vq)
                return -EINVAL;
        }
 
+       if (vq->vq.premapped == premapped) {
+               END_USE(vq);
+               return 0;
+       }
+
        if (!vq->use_dma_api) {
                END_USE(vq);
                return -EINVAL;
        }
 
-       vq->vq.premapped = true;
+       if (premapped) {
+               vq->vq.premapped = true;
+
+               if (vq->packed_ring) {
+                       kfree(vq->packed.desc_dma);
+                       vq->packed.desc_dma = NULL;
+               } else {
+                       kfree(vq->split.desc_dma);
+                       vq->split.desc_dma = NULL;
+               }
 
-       if (vq->packed_ring) {
-               kfree(vq->packed.desc_dma);
-               vq->packed.desc_dma = NULL;
        } else {
-               kfree(vq->split.desc_dma);
-               vq->split.desc_dma = NULL;
+               if (vq->packed_ring)
+                       err = vring_alloc_dma_split(&vq->split, false);
+               else
+                       err = vring_alloc_dma_packed(&vq->packed, false);
+
+               if (!err)
+                       vq->vq.premapped = false;
        }
 
        END_USE(vq);
 
-       return 0;
+       return err;
 }
 EXPORT_SYMBOL_GPL(virtqueue_set_dma_premapped);
 
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 407277d5a16b..4b338590abf4 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -82,7 +82,7 @@ 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 premapped);
 
 bool virtqueue_poll(struct virtqueue *vq, unsigned);
 
-- 
2.32.0.3.g01195cf9f