The default backend is only used within virtio_rng_device_realize().
Replace VirtIORNGConf member default_backend by a local variable.
Adjust its type to reduce conversions.

While there, pass &error_abort instead of NULL when failure would be a
programming error.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 hw/virtio/virtio-rng.c         | 20 +++++++++-----------
 include/hw/virtio/virtio-rng.h |  2 --
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 30493a2586..73ffb476e0 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -16,6 +16,7 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-rng.h"
 #include "sysemu/rng.h"
+#include "sysemu/rng-random.h"
 #include "qom/object_interfaces.h"
 #include "trace.h"
 
@@ -189,27 +190,24 @@ 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));
+        Object *default_backend = object_new(TYPE_RNG_RANDOM);
 
-        user_creatable_complete(USER_CREATABLE(vrng->conf.default_backend),
+        user_creatable_complete(USER_CREATABLE(default_backend),
                                 &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
-            object_unref(OBJECT(vrng->conf.default_backend));
+            object_unref(default_backend);
             return;
         }
 
-        object_property_add_child(OBJECT(dev),
-                                  "default-backend",
-                                  OBJECT(vrng->conf.default_backend),
-                                  NULL);
+        object_property_add_child(OBJECT(dev), "default-backend",
+                                  default_backend, &error_abort);
 
         /* The child property took a reference, we can safely drop ours now */
-        object_unref(OBJECT(vrng->conf.default_backend));
+        object_unref(default_backend);
 
-        object_property_set_link(OBJECT(dev),
-                                 OBJECT(vrng->conf.default_backend),
-                                 "rng", NULL);
+        object_property_set_link(OBJECT(dev), default_backend,
+                                 "rng", &error_abort);
     }
 
     vrng->rng = vrng->conf.rng;
diff --git a/include/hw/virtio/virtio-rng.h b/include/hw/virtio/virtio-rng.h
index 922dce7cac..28ff752c40 100644
--- a/include/hw/virtio/virtio-rng.h
+++ b/include/hw/virtio/virtio-rng.h
@@ -13,7 +13,6 @@
 #define QEMU_VIRTIO_RNG_H
 
 #include "sysemu/rng.h"
-#include "sysemu/rng-random.h"
 #include "standard-headers/linux/virtio_rng.h"
 
 #define TYPE_VIRTIO_RNG "virtio-rng-device"
@@ -26,7 +25,6 @@ struct VirtIORNGConf {
     RngBackend *rng;
     uint64_t max_bytes;
     uint32_t period_ms;
-    RngRandom *default_backend;
 };
 
 typedef struct VirtIORNG {
-- 
2.17.2