static void handle_notify(EventNotifier *e) { VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane, host_notifier); VirtQueueElement *elem; VirtIOBlockReq *req; int ret; MultiReqBuffer mrb = { .num_writes = 0, }; event_notifier_test_and_clear(&s->host_notifier); bdrv_io_plug(s->blk->conf.bs); for (;;) { /* Disable guest->host notifies to avoid unnecessary vmexits */ vring_disable_notification(s->vdev, &s->vring); for (;;) { ret = vring_pop(s->vdev, &s->vring, &elem); if (ret < 0) { assert(elem == NULL); break; /* no more requests */ } trace_virtio_blk_data_plane_process_request(s, elem->out_num, elem->in_num, elem->index); req = g_slice_new(VirtIOBlockReq); req->dev = VIRTIO_BLK(s->vdev); req->elem = elem; virtio_blk_handle_request(req, &mrb); } virtio_submit_multiwrite(s->blk->conf.bs, &mrb); if (likely(ret == -EAGAIN)) { /* vring emptied */ /* Re-enable guest->host notifies and stop processing the vring. * But if the guest has snuck in more descriptors, keep processing. */ if (vring_enable_notification(s->vdev, &s->vring)) { break; } } else { /* fatal error */ break; } } bdrv_io_unplug(s->blk->conf.bs); }