viona_vring_part_t
viona_vring_part_t vr_desc;
viona_vring_part_t vr_avail;
viona_vring_part_t vr_used;
const viona_vring_part_t *vrp = &ring->vr_used;
viona_ring_layout(viona_vring_t *ring, viona_vring_part_t *vrp,
viona_ring_map_part(viona_vring_t *ring, viona_vring_part_t *vrp,
viona_ring_mark_dirty_part(viona_vring_t *ring, viona_vring_part_t *vrp)
viona_ring_unmap_part(viona_vring_t *ring, viona_vring_part_t *vrp)
viona_ring_addr(const viona_vring_part_t *vrp, uint_t off)