map_one_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
		struct buf_vector *buf_vec, uint16_t *vec_idx,
		uint64_t desc_iova, uint64_t desc_len, uint8_t perm)
{
	uint16_t vec_id = *vec_idx;

	while (desc_len) {
		uint64_t desc_addr;
		uint64_t desc_chunck_len = desc_len;

		if (unlikely(vec_id >= BUF_VECTOR_MAX))
			return -1;

		desc_addr = vhost_iova_to_vva(dev, vq,
				desc_iova,
				&desc_chunck_len,
				perm);
		if (unlikely(!desc_addr))
			return -1;

		rte_prefetch0((void *)(uintptr_t)desc_addr);

		buf_vec[vec_id].buf_iova = desc_iova;
		buf_vec[vec_id].buf_addr = desc_addr;
		buf_vec[vec_id].buf_len  = desc_chunck_len;

		desc_len -= desc_chunck_len;
		desc_iova += desc_chunck_len;
		vec_id++;
	}
	*vec_idx = vec_id;

	return 0;
}