[Qemu-devel] [PATCH v1 0/4] -object/object-add add 2nd stage initialization

[Qemu-devel] [PATCH v1 0/4] -object/object-add add 2nd stage initialization

[Igor Mammedov]

Adds UserCreatable interface that objects must inherit from
If they need to be created with help of -object/object-add
commands.

Interface also provides an optional complete() callback,
that is called after object properties are set. Which allows
 * replace custom backend APIs to initialize them with generic
   object_new(); set object properties; object.complete();
   sequence.
 * bail out/report error early (at backend creation time)
   instead of failing later when adding device that uses
   that backend.

Reference to RFC:
https://lists.gnu.org/archive/html/qemu-devel/2014-01/msg00877.html

Changes since RFC:
* rename object_realize interface to UserCreatable
* make UserCreatable interface mandatory for -object/object-add
* drop custom location patch

Git tree for testing:
https://github.com/imammedo/qemu/commits/extend-object-add-v1

Igor Mammedov (4):
  object_add: consolidate error handling
  vl.c: -object: don't ingnore duplicate 'id'
  add optional 2nd stage initialization to -object/object-add commands
  virtio_rng: replace custom backend API with UserCreatable.complete()
    callback

 backends/rng.c                  |   17 +++++++++-
 hw/virtio/virtio-rng.c          |   15 +++++----
 include/qom/object_interfaces.h |   62 +++++++++++++++++++++++++++++++++++++++
 include/sysemu/rng.h            |   11 -------
 qmp.c                           |   22 +++++++++++--
 qom/Makefile.objs               |    1 +
 qom/object_interfaces.c         |   32 ++++++++++++++++++++
 vl.c                            |   22 +++++++++++++-
 8 files changed, 158 insertions(+), 24 deletions(-)
 create mode 100644 include/qom/object_interfaces.h
 create mode 100644 qom/object_interfaces.c

[Qemu-devel] [PATCH v1 1/4] object_add: consolidate error handling

[Igor Mammedov]

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 qmp.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/qmp.c b/qmp.c
index 0f46171..a67e0c4 100644
--- a/qmp.c
+++ b/qmp.c
@@ -549,15 +549,17 @@ void object_add(const char *type, const char *id, const QDict *qdict,
         for (e = qdict_first(qdict); e; e = qdict_next(qdict, e)) {
             object_property_set(obj, v, e->key, &local_err);
             if (local_err) {
-                error_propagate(errp, local_err);
-                object_unref(obj);
-                return;
+                goto out;
             }
         }
     }
 
     object_property_add_child(container_get(object_get_root(), "/objects"),
-                              id, obj, errp);
+                              id, obj, &local_err);
+out:
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
     object_unref(obj);
 }
 
-- 
1.7.1

[Qemu-devel] [PATCH v1 2/4] vl.c: -object: don't ingnore duplicate 'id'

[Igor Mammedov]

object_property_add_child() may fail if 'id' matches
an already existing object. Which meansi an incorrect
command line.
So instead of silently ignoring error, report it and
terminate QEMU.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 vl.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/vl.c b/vl.c
index 7f4fe0d..cf3de56 100644
--- a/vl.c
+++ b/vl.c
@@ -2800,6 +2800,7 @@ static int object_create(QemuOpts *opts, void *opaque)
 {
     const char *type = qemu_opt_get(opts, "qom-type");
     const char *id = qemu_opts_id(opts);
+    Error *local_err = NULL;
     Object *obj;
 
     g_assert(type != NULL);
@@ -2816,8 +2817,14 @@ static int object_create(QemuOpts *opts, void *opaque)
     }
 
     object_property_add_child(container_get(object_get_root(), "/objects"),
-                              id, obj, NULL);
+                              id, obj, &local_err);
+
     object_unref(obj);
+    if (local_err) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+        return -1;
+    }
     return 0;
 }
 
-- 
1.7.1

[Qemu-devel] [PATCH v1 3/4] add optional 2nd stage initialization to -object/object-add commands

[Igor Mammedov]

Introduces USER_CREATABLE interface that must be implemented by
objects which are designed to created with -object CLI option or
object-add QMP command.

Interface provides an ability to do an optional second stage
initialization of the object created with -object/object-add
commands. By providing complete() callback, which is called
after the object properties were set.

It allows to:
 * prevents misusing of -object/object-add by filtering out
   objects that are not designed for it.
 * generalize second stage backend initialization instead of
   adding custom APIs to perform it
 * early error detection of backend initialization at -object/
   object-add time rather than through a proxy DEVICE object
   that tries to use backend.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
Next patch will convert virtio_rng to a completion callback.
The same interface will be useful for memory and iothread
backends.
---
 backends/rng.c                  |    5 +++
 include/qom/object_interfaces.h |   62 +++++++++++++++++++++++++++++++++++++++
 qmp.c                           |   12 +++++++
 qom/Makefile.objs               |    1 +
 qom/object_interfaces.c         |   32 ++++++++++++++++++++
 vl.c                            |   13 ++++++++
 6 files changed, 125 insertions(+), 0 deletions(-)
 create mode 100644 include/qom/object_interfaces.h
 create mode 100644 qom/object_interfaces.c

diff --git a/backends/rng.c b/backends/rng.c
index 85cb83f..7bab806 100644
--- a/backends/rng.c
+++ b/backends/rng.c
@@ -12,6 +12,7 @@
 
 #include "sysemu/rng.h"
 #include "qapi/qmp/qerror.h"
+#include "qom/object_interfaces.h"
 
 void rng_backend_request_entropy(RngBackend *s, size_t size,
                                  EntropyReceiveFunc *receive_entropy,
@@ -83,6 +84,10 @@ static const TypeInfo rng_backend_info = {
     .instance_init = rng_backend_init,
     .class_size = sizeof(RngBackendClass),
     .abstract = true,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
 };
 
 static void register_types(void)
diff --git a/include/qom/object_interfaces.h b/include/qom/object_interfaces.h
new file mode 100644
index 0000000..eaf933f
--- /dev/null
+++ b/include/qom/object_interfaces.h
@@ -0,0 +1,62 @@
+#ifndef OBJECT_INTERFACES_H
+#define OBJECT_INTERFACES_H
+
+#include "qom/object.h"
+
+#define TYPE_USER_CREATABLE "user-creatable"
+
+#define USER_CREATABLE_CLASS(klass) \
+     OBJECT_CLASS_CHECK(UserCreatableClass, (klass), \
+                        TYPE_USER_CREATABLE)
+#define USER_CREATABLE_GET_CLASS(obj) \
+     OBJECT_GET_CLASS(UserCreatableClass, (obj), \
+                      TYPE_USER_CREATABLE)
+#define USER_CREATABLE(obj) \
+     INTERFACE_CHECK(UserCreatable, (obj), \
+                     TYPE_USER_CREATABLE)
+
+
+typedef struct UserCreatable {
+    /* <private> */
+    Object Parent;
+} UserCreatable;
+
+/**
+ * UserCreatableClass:
+ * @parent_class: the base class
+ * @complete: callback to be called after @obj's properties are set.
+ *
+ * Interface is designed to work with -object/object-add/object_add
+ * commands.
+ * Interface in mandatory for objects that are designed to be user
+ * creatable (i.e. -object/object-add/object_add, will accept only
+ * objects that inherit this interface).
+ *
+ * iInterface also provides an optional ability to do the second
+ * stage * initialization of the object after its properties were
+ * set.
+ *
+ * For objects created without using -object/object-add/object_add,
+ * @user_creatable_complete() wrapper should be called manually if
+ * object's type implements USER_CREATABLE interface and needs
+ * complete() callback to be called.
+ */
+typedef struct UserCreatableClass {
+    /* <private> */
+    InterfaceClass parent_class;
+
+    /* <public> */
+    void (*complete)(UserCreatable *uc, Error **errp);
+} UserCreatableClass;
+
+/**
+ * user_creatable_complete:
+ * @obj: the object whose complete() method is called if defined
+ * @errp: if an error occurs, a pointer to an area to store the error
+ *
+ * Wrapper to call complete() method if one of types it's inherited
+ * from implements USER_CREATABLE interface, otherwise the call does
+ * nothing.
+ */
+void user_creatable_complete(Object *obj, Error **errp);
+#endif
diff --git a/qmp.c b/qmp.c
index a67e0c4..d0d98e7 100644
--- a/qmp.c
+++ b/qmp.c
@@ -27,6 +27,7 @@
 #include "qapi/qmp/qobject.h"
 #include "qapi/qmp-input-visitor.h"
 #include "hw/boards.h"
+#include "qom/object_interfaces.h"
 
 NameInfo *qmp_query_name(Error **errp)
 {
@@ -554,6 +555,17 @@ void object_add(const char *type, const char *id, const QDict *qdict,
         }
     }
 
+    if (!object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
+        error_setg(&local_err, "object '%s' isn't supported by object-add",
+                   id);
+        goto out;
+    }
+
+    user_creatable_complete(obj, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     object_property_add_child(container_get(object_get_root(), "/objects"),
                               id, obj, &local_err);
 out:
diff --git a/qom/Makefile.objs b/qom/Makefile.objs
index 6a93ac7..985003b 100644
--- a/qom/Makefile.objs
+++ b/qom/Makefile.objs
@@ -1,2 +1,3 @@
 common-obj-y = object.o container.o qom-qobject.o
 common-obj-y += cpu.o
+common-obj-y += object_interfaces.o
diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
new file mode 100644
index 0000000..6360818
--- /dev/null
+++ b/qom/object_interfaces.c
@@ -0,0 +1,32 @@
+#include "qom/object_interfaces.h"
+#include "qemu/module.h"
+
+void user_creatable_complete(Object *obj, Error **errp)
+{
+
+    UserCreatableClass *ucc;
+    UserCreatable *uc =
+        (UserCreatable *)object_dynamic_cast(obj, TYPE_USER_CREATABLE);
+
+    if (!uc) {
+        return;
+    }
+
+    ucc = USER_CREATABLE_GET_CLASS(uc);
+    if (ucc->complete) {
+        ucc->complete(uc, errp);
+    }
+}
+
+static void register_types(void)
+{
+    static const TypeInfo uc_interface_info = {
+        .name          = TYPE_USER_CREATABLE,
+        .parent        = TYPE_INTERFACE,
+        .class_size = sizeof(UserCreatableClass),
+    };
+
+    type_register_static(&uc_interface_info);
+}
+
+type_init(register_types)
diff --git a/vl.c b/vl.c
index cf3de56..9c2619f 100644
--- a/vl.c
+++ b/vl.c
@@ -170,6 +170,7 @@ int main(int argc, char **argv)
 
 #include "ui/qemu-spice.h"
 #include "qapi/string-input-visitor.h"
+#include "qom/object_interfaces.h"
 
 //#define DEBUG_NET
 //#define DEBUG_SLIRP
@@ -2816,9 +2817,21 @@ static int object_create(QemuOpts *opts, void *opaque)
         return -1;
     }
 
+    if (!object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
+        error_setg(&local_err, "object '%s' isn't supported by -object",
+                   id);
+        goto out;
+    }
+
+    user_creatable_complete(obj, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     object_property_add_child(container_get(object_get_root(), "/objects"),
                               id, obj, &local_err);
 
+out:
     object_unref(obj);
     if (local_err) {
         qerror_report_err(local_err);
-- 
1.7.1

[Qemu-devel] [PATCH v1 4/4] virtio_rng: replace custom backend API with UserCreatable.complete() callback

[Igor Mammedov]

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

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 backends/rng.c         |   12 ++++++++++--
 hw/virtio/virtio-rng.c |   15 +++++++++------
 include/sysemu/rng.h   |   11 -----------
 3 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/backends/rng.c b/backends/rng.c
index 7bab806..8b8d5a4 100644
--- a/backends/rng.c
+++ b/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 },
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 755fdee..a16e3bc 100644
--- a/hw/virtio/virtio-rng.c
+++ b/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);
diff --git a/include/sysemu/rng.h b/include/sysemu/rng.h
index 7637fac..0a27c9b 100644
--- a/include/sysemu/rng.h
+++ b/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
-- 
1.7.1

Re: [Qemu-devel] [PATCH v1 2/4] vl.c: -object: don't ingnore duplicate 'id'

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 637 bytes --]

On 01/16/2014 09:34 AM, Igor Mammedov wrote:

s/ingnore/ignore/ in subject

> object_property_add_child() may fail if 'id' matches
> an already existing object. Which meansi an incorrect

s/meansi/means/

> command line.
> So instead of silently ignoring error, report it and
> terminate QEMU.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>  vl.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)

Fix those, and you can add:
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
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Re: [Qemu-devel] [PATCH v1 0/4] -object/object-add add 2nd stage initialization

[Stefan Hajnoczi]

On Thu, Jan 16, 2014 at 05:34:35PM +0100, Igor Mammedov wrote:
> Adds UserCreatable interface that objects must inherit from
> If they need to be created with help of -object/object-add
> commands.
> 
> Interface also provides an optional complete() callback,
> that is called after object properties are set. Which allows
>  * replace custom backend APIs to initialize them with generic
>    object_new(); set object properties; object.complete();
>    sequence.
>  * bail out/report error early (at backend creation time)
>    instead of failing later when adding device that uses
>    that backend.
> 
> Reference to RFC:
> https://lists.gnu.org/archive/html/qemu-devel/2014-01/msg00877.html
> 
> Changes since RFC:
> * rename object_realize interface to UserCreatable
> * make UserCreatable interface mandatory for -object/object-add
> * drop custom location patch
> 
> Git tree for testing:
> https://github.com/imammedo/qemu/commits/extend-object-add-v1
> 
> Igor Mammedov (4):
>   object_add: consolidate error handling
>   vl.c: -object: don't ingnore duplicate 'id'
>   add optional 2nd stage initialization to -object/object-add commands
>   virtio_rng: replace custom backend API with UserCreatable.complete()
>     callback
> 
>  backends/rng.c                  |   17 +++++++++-
>  hw/virtio/virtio-rng.c          |   15 +++++----
>  include/qom/object_interfaces.h |   62 +++++++++++++++++++++++++++++++++++++++
>  include/sysemu/rng.h            |   11 -------
>  qmp.c                           |   22 +++++++++++--
>  qom/Makefile.objs               |    1 +
>  qom/object_interfaces.c         |   32 ++++++++++++++++++++
>  vl.c                            |   22 +++++++++++++-
>  8 files changed, 158 insertions(+), 24 deletions(-)
>  create mode 100644 include/qom/object_interfaces.h
>  create mode 100644 qom/object_interfaces.c

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Rebased my IOThread series onto this and tested successfully.

Re: [Qemu-devel] [PATCH v1 0/4] -object/object-add add 2nd stage initialization

[Luiz Capitulino]

On Thu, 16 Jan 2014 17:34:35 +0100
Igor Mammedov <imammedo@redhat.com> wrote:

> Adds UserCreatable interface that objects must inherit from
> If they need to be created with help of -object/object-add
> commands.
> 
> Interface also provides an optional complete() callback,
> that is called after object properties are set. Which allows
>  * replace custom backend APIs to initialize them with generic
>    object_new(); set object properties; object.complete();
>    sequence.
>  * bail out/report error early (at backend creation time)
>    instead of failing later when adding device that uses
>    that backend.

Applied to the qmp branch, thanks.

> 
> Reference to RFC:
> https://lists.gnu.org/archive/html/qemu-devel/2014-01/msg00877.html
> 
> Changes since RFC:
> * rename object_realize interface to UserCreatable
> * make UserCreatable interface mandatory for -object/object-add
> * drop custom location patch
> 
> Git tree for testing:
> https://github.com/imammedo/qemu/commits/extend-object-add-v1
> 
> Igor Mammedov (4):
>   object_add: consolidate error handling
>   vl.c: -object: don't ingnore duplicate 'id'
>   add optional 2nd stage initialization to -object/object-add commands
>   virtio_rng: replace custom backend API with UserCreatable.complete()
>     callback
> 
>  backends/rng.c                  |   17 +++++++++-
>  hw/virtio/virtio-rng.c          |   15 +++++----
>  include/qom/object_interfaces.h |   62 +++++++++++++++++++++++++++++++++++++++
>  include/sysemu/rng.h            |   11 -------
>  qmp.c                           |   22 +++++++++++--
>  qom/Makefile.objs               |    1 +
>  qom/object_interfaces.c         |   32 ++++++++++++++++++++
>  vl.c                            |   22 +++++++++++++-
>  8 files changed, 158 insertions(+), 24 deletions(-)
>  create mode 100644 include/qom/object_interfaces.h
>  create mode 100644 qom/object_interfaces.c
> 

Re: [Qemu-devel] [PATCH v1 4/4] virtio_rng: replace custom backend API with UserCreatable.complete() callback

[Amos Kong]

On Thu, Jan 16, 2014 at 05:34:39PM +0100, Igor Mammedov wrote:
> in addition fix default backend leak by releasing it if its
> initialization failed.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>

Hi Igor,

This patch introduced a regression.

x86_64-softmmu/qemu-system-x86_64 -monitor stdio -vnc :0 \
   -chardev socket,host=localhost,port=1024,id=chr0 \
   -object rng-egd,chardev=chr0,id=rng0
qemu-system-x86_64: -object rng-egd,chardev=chr0,id=rng0: Device 'chr0' not found

chardev 'chr0' isn't initialized when we try to open rng backend.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1128095

> ---
>  backends/rng.c         |   12 ++++++++++--
>  hw/virtio/virtio-rng.c |   15 +++++++++------
>  include/sysemu/rng.h   |   11 -----------
>  3 files changed, 19 insertions(+), 19 deletions(-)
> 
> diff --git a/backends/rng.c b/backends/rng.c
> index 7bab806..8b8d5a4 100644
> --- a/backends/rng.c
> +++ b/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 },
> diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
> index 755fdee..a16e3bc 100644
> --- a/hw/virtio/virtio-rng.c
> +++ b/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);
> diff --git a/include/sysemu/rng.h b/include/sysemu/rng.h
> index 7637fac..0a27c9b 100644
> --- a/include/sysemu/rng.h
> +++ b/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
> -- 
> 1.7.1
> 

-- 
			Amos.