virtio_rng: replace custom backend API with UserCreatable.complete() callback

in addition fix default backend leak by releasing it if its
initialization failed.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

backends/rng.c

@@ -41,9 +41,9 @@ static bool rng_backend_prop_get_opened(Object *obj, Error **errp)
     return s->opened;
 }
 
-void rng_backend_open(RngBackend *s, Error **errp)
+static void rng_backend_complete(UserCreatable *uc, Error **errp)
 {
-    object_property_set_bool(OBJECT(s), true, "opened", errp);
+    object_property_set_bool(OBJECT(uc), true, "opened", errp);
 }
 
 static void rng_backend_prop_set_opened(Object *obj, bool value, Error **errp)
@@ -77,12 +77,20 @@ static void rng_backend_init(Object *obj)
                              NULL);
 }
 
+static void rng_backend_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+    ucc->complete = rng_backend_complete;
+}
+
 static const TypeInfo rng_backend_info = {
     .name = TYPE_RNG_BACKEND,
     .parent = TYPE_OBJECT,
     .instance_size = sizeof(RngBackend),
     .instance_init = rng_backend_init,
     .class_size = sizeof(RngBackendClass),
+    .class_init = rng_backend_class_init,
     .abstract = true,
     .interfaces = (InterfaceInfo[]) {
         { TYPE_USER_CREATABLE },

hw/virtio/virtio-rng.c

@@ -15,6 +15,7 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-rng.h"
 #include "sysemu/rng.h"
+#include "qom/object_interfaces.h"
 
 static bool is_guest_ready(VirtIORNG *vrng)
 {
@@ -148,6 +149,14 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
     if (vrng->conf.rng == NULL) {
         vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
 
+        user_creatable_complete(OBJECT(vrng->conf.default_backend),
+                                &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            object_unref(OBJECT(vrng->conf.default_backend));
+            return;
+        }
+
         object_property_add_child(OBJECT(dev),
                                   "default-backend",
                                   OBJECT(vrng->conf.default_backend),
@@ -166,12 +175,6 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
         return;
     }
 
-    rng_backend_open(vrng->rng, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        return;
-    }
-
     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
 
     assert(vrng->conf.max_bytes <= INT64_MAX);

include/sysemu/rng.h

@@ -79,15 +79,4 @@ void rng_backend_request_entropy(RngBackend *s, size_t size,
  * to stop tracking any request.
  */
 void rng_backend_cancel_requests(RngBackend *s);
-
-/**
- * rng_backend_open:
- * @s: the backend to open
- * @errp: a pointer to return the #Error object if an error occurs.
- *
- * This function will open the backend if it is not already open.  Calling this
- * function on an already opened backend will not result in an error.
- */
-void rng_backend_open(RngBackend *s, Error **errp);
-
 #endif