static bool vring_notify(VirtIODevice *vdev, VirtQueue *vq) { uint16_t old, new; bool v; /* We need to expose used array entries before checking used event. */ smp_mb(); /* Always notify when queue is empty (when feature acknowledge) */ if (virtio_has_feature(vdev, VIRTIO_F_NOTIFY_ON_EMPTY) && !vq->inuse && vring_avail_idx(vq) == vq->last_avail_idx) { return true; } if (!virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) { return !(vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT); } v = vq->signalled_used_valid; vq->signalled_used_valid = true; old = vq->signalled_used; new = vq->signalled_used = vring_used_idx(vq); return !v || vring_need_event(vring_get_used_event(vq), new, old); }
static bool vring_notify(VirtIODevice *vdev, VirtQueue *vq) { uint16_t old, new; bool v;   smp_mb();   if (virtio_has_feature(vdev, VIRTIO_F_NOTIFY_ON_EMPTY) && !vq->inuse && vring_avail_idx(vq) == vq->last_avail_idx) { return true; } if (!virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) { return !(vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT); } v = vq->signalled_used_valid; vq->signalled_used_valid = true; old = vq->signalled_used; new = vq->signalled_used = vring_used_idx(vq); return !v || vring_need_event(vring_get_used_event(vq), new, old); }