Re: [PATCH v5 6/8] virtio_vdpa: setup correct vq size with callbacks get_vq_num_{max,min}

For the devices which implement the get_vq_num_min callback, the driver
should not negotiate with virtqueue size with the backend vdpa device if
the value returned by get_vq_num_min equals to the value returned by
get_vq_num_max.
This is useful for vdpa devices based on legacy virtio specfication.

Signed-off-by: Wu Zongyong <redacted>
---
  drivers/virtio/virtio_vdpa.c | 21 ++++++++++++++++-----
  1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
index 72eaef2caeb1..e42ace29daa1 100644
--- a/drivers/virtio/virtio_vdpa.c
+++ b/drivers/virtio/virtio_vdpa.c

@@ -145,7 +145,8 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
  	/* Assume split virtqueue, switch to packed if necessary */
  	struct vdpa_vq_state state = {0};
  	unsigned long flags;
-	u32 align, num;
+	u32 align, max_num, min_num = 0;
+	bool may_reduce_num = true;
  	int err;
  
  	if (!name)

@@ -163,22 +164,32 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
  	if (!info)
  		return ERR_PTR(-ENOMEM);
  
-	num = ops->get_vq_num_max(vdpa);
-	if (num == 0) {
+	max_num = ops->get_vq_num_max(vdpa);
+	if (max_num == 0) {
  		err = -ENOENT;
  		goto error_new_virtqueue;
  	}
  
+	if (ops->get_vq_num_min)
+		min_num = ops->get_vq_num_min(vdpa);
+
+	may_reduce_num = (max_num == min_num) ? false : true;
+
  	/* Create the vring */
  	align = ops->get_vq_align(vdpa);
-	vq = vring_create_virtqueue(index, num, align, vdev,
-				    true, true, ctx,
+	vq = vring_create_virtqueue(index, max_num, align, vdev,
+				    true, may_reduce_num, ctx,
  				    virtio_vdpa_notify, callback, name);
  	if (!vq) {
  		err = -ENOMEM;
  		goto error_new_virtqueue;
  	}
  
+	if (virtqueue_get_vring_size(vq) < min_num) {
+		err = -EINVAL;
+		goto err_vq;
+	}