int vring_more_used(struct vring_virtqueue *vq);
void vring_detach(struct vring_virtqueue *vq, unsigned int head);
int vring_get_buf(struct vring_virtqueue *vq, unsigned int *len);
void vring_add_buf(struct vring_virtqueue *vq, struct vring_list list[],
unsigned int out, unsigned int in,
int index, int num_added);
int vring_more_used(struct vring_virtqueue *vq);
void vring_detach(struct vring_virtqueue *vq, unsigned int head);
int vring_get_buf(struct vring_virtqueue *vq, unsigned int *len);
void vring_add_buf(struct vring_virtqueue *vq, struct vring_list list[],
unsigned int out, unsigned int in,
int index, int num_added);