[Qemu-devel] [PATCH 8/9] virtio: merge virtio_queue_aio_set_host_notifier_handler with virtio_queue_set_aio

[Paolo Bonzini <pbonzini@redhat.com>]

Eliminating the reentrancy is actually a nice thing that we can do
with the API that Michael proposed, so let's make it first class.
This also hides the complex assign/set_handler conventions from
callers of virtio_queue_aio_set_host_notifier_handler, and fixes
a possible race that could happen when passing assign=false to
virtio_queue_aio_set_host_notifier_handler.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/block/dataplane/virtio-blk.c |  7 +++----
 hw/scsi/virtio-scsi-dataplane.c | 12 ++++--------
 hw/virtio/virtio.c              | 19 ++++---------------
 include/hw/virtio/virtio.h      |  6 ++----
 4 files changed, 13 insertions(+), 31 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 4a137df..7e50d01 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -236,8 +236,8 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
 
     /* Get this show started by hooking up our callbacks */
     aio_context_acquire(s->ctx);
-    virtio_set_queue_aio(s->vq, virtio_blk_data_plane_handle_output);
-    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, true);
+    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx,
+					       virtio_blk_data_plane_handle_output);
     aio_context_release(s->ctx);
     return;
 
@@ -272,8 +272,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
     aio_context_acquire(s->ctx);
 
     /* Stop notifications for new requests from guest */
-    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, false);
-    virtio_set_queue_aio(s->vq, NULL);
+    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, NULL);
 
     /* Drain and switch bs back to the QEMU main loop */
     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index 0fa5bb5..8694577 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -82,8 +82,7 @@ static int virtio_scsi_vring_init(VirtIOSCSI *s, VirtQueue *vq, int n,
         return rc;
     }
 
-    virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, true, true);
-    virtio_set_queue_aio(vq, fn);
+    virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, fn);
     return 0;
 }
 
@@ -100,13 +99,10 @@ static void virtio_scsi_clear_aio(VirtIOSCSI *s)
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
     int i;
 
-    virtio_queue_aio_set_host_notifier_handler(vs->ctrl_vq, s->ctx, true, false);
-    virtio_set_queue_aio(vs->ctrl_vq, NULL);
-    virtio_queue_aio_set_host_notifier_handler(vs->event_vq, s->ctx, true, false);
-    virtio_set_queue_aio(vs->event_vq, NULL);
+    virtio_queue_aio_set_host_notifier_handler(vs->ctrl_vq, s->ctx, NULL);
+    virtio_queue_aio_set_host_notifier_handler(vs->event_vq, s->ctx, NULL);
     for (i = 0; i < vs->conf.num_queues; i++) {
-        virtio_queue_aio_set_host_notifier_handler(vs->cmd_vqs[i], s->ctx, true, false);
-        virtio_set_queue_aio(vs->cmd_vqs[i], NULL);
+        virtio_queue_aio_set_host_notifier_handler(vs->cmd_vqs[i], s->ctx, NULL);
     }
 }
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 39a9f47..b16d2d8 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1157,14 +1157,6 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
     return &vdev->vq[i];
 }
 
-void virtio_set_queue_aio(VirtQueue *vq,
-                          void (*handle_output)(VirtIODevice *, VirtQueue *))
-{
-    assert(vq->handle_output);
-
-    vq->handle_aio_output = handle_output;
-}
-
 void virtio_del_queue(VirtIODevice *vdev, int n)
 {
     if (n < 0 || n >= VIRTIO_QUEUE_MAX) {
@@ -1807,19 +1799,16 @@ static void virtio_queue_host_notifier_aio_read(EventNotifier *n)
 }
 
 void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
-                                                bool assign, bool set_handler)
+                                                void (*handle_output)(VirtIODevice *,
+							   VirtQueue *))
 {
-    if (assign && set_handler) {
+    vq->handle_aio_output = handle_output;
+    if (handle_output) {
         aio_set_event_notifier(ctx, &vq->host_notifier, true,
                                virtio_queue_host_notifier_aio_read);
     } else {
         aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL);
     }
-    if (!assign) {
-        /* Test and clear notifier before after disabling event,
-         * in case poll callback didn't have time to run. */
-        virtio_queue_host_notifier_aio_read(&vq->host_notifier);
-    }
 }
 
 static void virtio_queue_host_notifier_read(EventNotifier *n)
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index fa3f93b..6a37065 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -142,9 +142,6 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
                             void (*handle_output)(VirtIODevice *,
                                                   VirtQueue *));
 
-void virtio_set_queue_aio(VirtQueue *vq,
-                          void (*handle_output)(VirtIODevice *, VirtQueue *));
-
 void virtio_del_queue(VirtIODevice *vdev, int n);
 
 void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_num);
@@ -254,7 +251,8 @@ EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
 void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
                                                bool set_handler);
 void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
-                                                bool assign, bool set_handler);
+                                                void (*fn)(VirtIODevice *,
+                                                           VirtQueue *));
 void virtio_irq(VirtQueue *vq);
 VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector);
 VirtQueue *virtio_vector_next_queue(VirtQueue *vq);
-- 
1.8.3.1