VHOST_ADDR_USED
VHOST_ADDR_USED);
sizeof(*ptr), VHOST_ADDR_USED); \
vhost_get_user(vq, x, ptr, VHOST_ADDR_USED)
int access = (type == VHOST_ADDR_USED) ?
vhost_get_used_size(vq, num), VHOST_ADDR_USED);