[04/13] virtio: add start_ioeventfd and stop_ioeventfd to VirtioDeviceClass

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 97cdb11..a8d2bd8 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -153,8 +153,8 @@  void virtio_bus_set_vdev_config(VirtioBusState *bus, uint8_t *config)
  * assign: register/deregister ioeventfd with the kernel
  * set_handler: use the generic ioeventfd handler
  */
-static int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
-                                      int n, bool assign, bool set_handler)
+int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
+                               int n, bool assign, bool set_handler)
 {
     VirtIODevice *vdev = virtio_bus_get_device(bus);
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
@@ -185,61 +185,41 @@  static int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
     return r;
 }
 
-void virtio_bus_start_ioeventfd(VirtioBusState *bus)
+int virtio_bus_start_ioeventfd(VirtioBusState *bus)
 {
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
     DeviceState *proxy = DEVICE(BUS(bus)->parent);
-    VirtIODevice *vdev;
-    int n, r;
+    VirtIODevice *vdev = virtio_bus_get_device(bus);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+    int r;
 
     if (!k->ioeventfd_assign || k->ioeventfd_disabled(proxy)) {
-        return;
+        return -ENOSYS;
     }
     if (bus->ioeventfd_started || bus->ioeventfd_disabled) {
-        return;
+        return 0;
     }
-    vdev = virtio_bus_get_device(bus);
-    for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
-        if (!virtio_queue_get_num(vdev, n)) {
-            continue;
-        }
-        r = set_host_notifier_internal(proxy, bus, n, true, true);
-        if (r < 0) {
-            goto assign_error;
-        }
+    r = vdc->start_ioeventfd(vdev);
+    if (r < 0) {
+        error_report("%s: failed. Fallback to userspace (slower).", __func__);
+        return r;
     }
     bus->ioeventfd_started = true;
-    return;
-
-assign_error:
-    while (--n >= 0) {
-        if (!virtio_queue_get_num(vdev, n)) {
-            continue;
-        }
-
-        r = set_host_notifier_internal(proxy, bus, n, false, false);
-        assert(r >= 0);
-    }
-    error_report("%s: failed. Fallback to userspace (slower).", __func__);
+    return 0;
 }
 
 void virtio_bus_stop_ioeventfd(VirtioBusState *bus)
 {
-    DeviceState *proxy = DEVICE(BUS(bus)->parent);
     VirtIODevice *vdev;
-    int n, r;
+    VirtioDeviceClass *vdc;
 
     if (!bus->ioeventfd_started) {
         return;
     }
+
     vdev = virtio_bus_get_device(bus);
-    for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
-        if (!virtio_queue_get_num(vdev, n)) {
-            continue;
-        }
-        r = set_host_notifier_internal(proxy, bus, n, false, false);
-        assert(r >= 0);
-    }
+    vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+    vdc->stop_ioeventfd(vdev);
     bus->ioeventfd_started = false;
 }
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index d48d1a9..7740975 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2158,15 +2158,79 @@  static Property virtio_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
+{
+    VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    DeviceState *proxy = DEVICE(BUS(qbus)->parent);
+    int n, r, err;
+
+    for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+        r = set_host_notifier_internal(proxy, qbus, n, true, true);
+        if (r < 0) {
+            err = r;
+            goto assign_error;
+        }
+    }
+    return 0;
+
+assign_error:
+    while (--n >= 0) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+
+        r = set_host_notifier_internal(proxy, qbus, n, false, false);
+        assert(r >= 0);
+    }
+    return err;
+}
+
+int virtio_device_start_ioeventfd(VirtIODevice *vdev)
+{
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusState *vbus = VIRTIO_BUS(qbus);
+
+    return virtio_bus_start_ioeventfd(vbus);
+}
+
+static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
+{
+    VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    DeviceState *proxy = DEVICE(BUS(qbus)->parent);
+    int n, r;
+
+    for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
+        if (!virtio_queue_get_num(vdev, n)) {
+            continue;
+        }
+        r = set_host_notifier_internal(proxy, qbus, n, false, false);
+        assert(r >= 0);
+    }
+}
+
+void virtio_device_stop_ioeventfd(VirtIODevice *vdev)
+{
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusState *vbus = VIRTIO_BUS(qbus);
+
+    virtio_bus_stop_ioeventfd(vbus);
+}
+
 static void virtio_device_class_init(ObjectClass *klass, void *data)
 {
     /* Set the default value here. */
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = virtio_device_realize;
     dc->unrealize = virtio_device_unrealize;
     dc->bus_type = TYPE_VIRTIO_BUS;
     dc->props = virtio_properties;
+    vdc->start_ioeventfd = virtio_device_start_ioeventfd_impl;
+    vdc->stop_ioeventfd = virtio_device_stop_ioeventfd_impl;
 }
 
 static const TypeInfo virtio_device_info = {
diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index f74ef1e..aa326e1 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -132,10 +132,15 @@  static inline VirtIODevice *virtio_bus_get_device(VirtioBusState *bus)
 }
 
 /* Start the ioeventfd. */
-void virtio_bus_start_ioeventfd(VirtioBusState *bus);
+int virtio_bus_start_ioeventfd(VirtioBusState *bus);
 /* Stop the ioeventfd. */
 void virtio_bus_stop_ioeventfd(VirtioBusState *bus);
 /* Switch from/to the generic ioeventfd handler */
 int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign);
 
+/* This is temporary.  It is only needed because virtio_bus_set_host_notifier
+ * sets ioeventfd_disabled but we will shortly get rid of it.  */
+int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
+                               int n, bool assign, bool set_handler);
+
 #endif /* VIRTIO_BUS_H */
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index b913aac..0e70951 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -125,6 +125,8 @@  typedef struct VirtioDeviceClass {
      * must mask in frontend instead.
      */
     void (*guest_notifier_mask)(VirtIODevice *vdev, int n, bool mask);
+    int (*start_ioeventfd)(VirtIODevice *vdev);
+    void (*stop_ioeventfd)(VirtIODevice *vdev);
     void (*save)(VirtIODevice *vdev, QEMUFile *f);
     int (*load)(VirtIODevice *vdev, QEMUFile *f, int version_id);
 } VirtioDeviceClass;
@@ -265,6 +267,8 @@  uint16_t virtio_get_queue_index(VirtQueue *vq);
 EventNotifier *virtio_queue_get_guest_notifier(VirtQueue *vq);
 void virtio_queue_set_guest_notifier_fd_handler(VirtQueue *vq, bool assign,
                                                 bool with_irqfd);
+int virtio_device_start_ioeventfd(VirtIODevice *vdev);
+void virtio_device_stop_ioeventfd(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);