[Qemu-devel] [PATCH 03/12] virtio: add start_ioeventfd and stop_ioeventfd to VirtioDeviceClass

[Paolo Bonzini <pbonzini@redhat.com>]

Allow customization of the start and stop of ioeventfd.  This will
allow direct start of dataplane without passing through the default
ioeventfd handlers, which in turn allows using the dataplane logic
instead of virtio_add_queue_aio.  It will also enable some code
simplification, because the sole entry point to ioeventfd setup
will be virtio_bus_set_host_notifier.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/virtio/virtio-bus.c         | 55 +++++++++++-------------------------
 hw/virtio/virtio.c             | 64 ++++++++++++++++++++++++++++++++++++++++++
 include/hw/virtio/virtio-bus.h |  7 ++++-
 include/hw/virtio/virtio.h     |  4 +++
 4 files changed, 90 insertions(+), 40 deletions(-)

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 64daf34..94e202d 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -152,8 +152,8 @@ 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);
@@ -183,61 +183,38 @@ 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;
+    VirtIODevice *vdev = virtio_bus_get_device(bus);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
 
     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->stop_ioeventfd(vdev);
     bus->ioeventfd_started = false;
 }
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 15ee3a7..2919113 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1946,15 +1946,79 @@ 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 7031add..01b11c5 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -135,10 +135,15 @@ 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 d2490c1..f283217 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -124,6 +124,8 @@ 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;
@@ -270,6 +272,8 @@ 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);
-- 
2.7.4