Re: [PATCH v6 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;
+       }