hv_ring_buffer
BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
ring_info->ring_buffer = (struct hv_ring_buffer *)
sizeof(struct hv_ring_buffer);
((payload_sz) >= 8 * sizeof(struct hv_ring_buffer) ? \
0 : sizeof(struct hv_ring_buffer))
struct hv_ring_buffer *ring_buffer;