[Qemu-devel] [PATCH 11/12] virtio: inline virtio_queue_set_host_notifier_fd_handler

[Paolo Bonzini <pbonzini@redhat.com>]

Of the three possible parameter combinations for
virtio_queue_set_host_notifier_fd_handler:

- assign=true/set_handler=true is only called from
  virtio_device_start_ioeventfd

- assign=false/set_handler=false is called from
  set_host_notifier_internal but it only does something when
  reached from virtio_device_stop_ioeventfd_impl; otherwise
  there is no EventNotifier set on qemu_get_aio_context().

- assign=true/set_handler=false is called from
  set_host_notifier_internal, but it is not doing anything:
  with the new start_ioeventfd and stop_ioeventfd methods,
  there is never an EventNotifier set on qemu_get_aio_context()
  at this point.  This is enforced by the assertion in
  virtio_bus_set_host_notifier.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/virtio/virtio-bus.c     | 19 +++++++++++--------
 hw/virtio/virtio.c         | 27 +++++++++------------------
 include/hw/virtio/virtio.h |  3 +--
 3 files changed, 21 insertions(+), 28 deletions(-)

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 289bf86..b8f0527 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -161,19 +161,22 @@ static int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
             error_report("%s: unable to init event notifier: %d", __func__, r);
             return r;
         }
-        virtio_queue_set_host_notifier_fd_handler(vq, true, false);
-        r = k->ioeventfd_assign(proxy, notifier, n, assign);
+        r = k->ioeventfd_assign(proxy, notifier, n, true);
         if (r < 0) {
             error_report("%s: unable to assign ioeventfd: %d", __func__, r);
-            virtio_queue_set_host_notifier_fd_handler(vq, false, false);
-            event_notifier_cleanup(notifier);
-            return r;
+            goto cleanup_event_notifier;
         }
+        return 0;
     } else {
-        k->ioeventfd_assign(proxy, notifier, n, assign);
-        virtio_queue_set_host_notifier_fd_handler(vq, false, false);
-        event_notifier_cleanup(notifier);
+        k->ioeventfd_assign(proxy, notifier, n, false);
     }
+
+cleanup_event_notifier:
+    /* Test and clear notifier before after disabling event,
+     * in case poll callback didn't have time to run.
+     */
+    virtio_queue_host_notifier_read(notifier);
+    event_notifier_cleanup(notifier);
     return r;
 }
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 8abcd3d..f11ab10 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1835,7 +1835,7 @@ void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
     }
 }
 
-static void virtio_queue_host_notifier_read(EventNotifier *n)
+void virtio_queue_host_notifier_read(EventNotifier *n)
 {
     VirtQueue *vq = container_of(n, VirtQueue, host_notifier);
     if (event_notifier_test_and_clear(n)) {
@@ -1843,22 +1843,6 @@ static void virtio_queue_host_notifier_read(EventNotifier *n)
     }
 }
 
-void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
-                                               bool set_handler)
-{
-    if (assign && set_handler) {
-        event_notifier_set_handler(&vq->host_notifier, true,
-                                   virtio_queue_host_notifier_read);
-    } else {
-        event_notifier_set_handler(&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_read(&vq->host_notifier);
-    }
-}
-
 EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq)
 {
     return &vq->host_notifier;
@@ -1922,6 +1906,7 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
     int n, r, err;
 
     for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
+        VirtQueue *vq = &vdev->vq[n];
         if (!virtio_queue_get_num(vdev, n)) {
             continue;
         }
@@ -1930,7 +1915,8 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
             err = r;
             goto assign_error;
         }
-        virtio_queue_set_host_notifier_fd_handler(&vdev->vq[n], true, true);
+        event_notifier_set_handler(&vq->host_notifier, true,
+                                   virtio_queue_host_notifier_read);
     }
 
     for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
@@ -1945,10 +1931,12 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
 
 assign_error:
     while (--n >= 0) {
+        VirtQueue *vq = &vdev->vq[n];
         if (!virtio_queue_get_num(vdev, n)) {
             continue;
         }
 
+        event_notifier_set_handler(&vq->host_notifier, true, NULL);
         r = virtio_bus_set_host_notifier(qbus, n, false);
         assert(r >= 0);
     }
@@ -1969,9 +1957,12 @@ static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
     int n, r;
 
     for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
+        VirtQueue *vq = &vdev->vq[n];
+
         if (!virtio_queue_get_num(vdev, n)) {
             continue;
         }
+        event_notifier_set_handler(&vq->host_notifier, true, NULL);
         r = virtio_bus_set_host_notifier(qbus, n, false);
         assert(r >= 0);
     }
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 1db4fbf..ac121b1 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -273,8 +273,7 @@ int virtio_device_start_ioeventfd(VirtIODevice *vdev);
 void virtio_device_stop_ioeventfd(VirtIODevice *vdev);
 bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev);
 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_host_notifier_read(EventNotifier *n);
 void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
                                                 void (*fn)(VirtIODevice *,
                                                            VirtQueue *));
-- 
2.7.4