[PATCH v2] qom: reverse order of instance_post_init calls

[PATCH v2] qom: reverse order of instance_post_init calls

[Paolo Bonzini]

Currently, the instance_post_init calls are performed from the leaf
class and all the way up to Object.  This is incorrect because the
leaf class cannot observe property values applied by the superclasses;
for example, a compat property will be set on a device *after*
the class's post_init callback has run.

In particular this makes it impossible for implementations of
accel_cpu_instance_init() to operate based on the actual values of
the properties, though it seems that cxl_dsp_instance_post_init and
rp_instance_post_init might have similar issues.

Follow instead the same order as instance_init, starting with Object
and running the child class's instance_post_init after the parent.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qom/object.h | 3 ++-
 qom/object.c         | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/qom/object.h b/include/qom/object.h
index 9192265db76..c87a392259d 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -445,7 +445,8 @@ struct Object
  *   class will have already been initialized so the type is only responsible
  *   for initializing its own members.
  * @instance_post_init: This function is called to finish initialization of
- *   an object, after all @instance_init functions were called.
+ *   an object, after all @instance_init functions were called, as well as
+ *   @instance_post_init functions for the parent classes.
  * @instance_finalize: This function is called during object destruction.  This
  *   is called before the parent @instance_finalize function has been called.
  *   An object should only free the members that are unique to its type in this
diff --git a/qom/object.c b/qom/object.c
index ec447f14a78..9b03da22cce 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -431,13 +431,13 @@ static void object_init_with_type(Object *obj, TypeImpl *ti)
 
 static void object_post_init_with_type(Object *obj, TypeImpl *ti)
 {
-    if (ti->instance_post_init) {
-        ti->instance_post_init(obj);
-    }
-
     if (type_has_parent(ti)) {
         object_post_init_with_type(obj, type_get_parent(ti));
     }
+
+    if (ti->instance_post_init) {
+        ti->instance_post_init(obj);
+    }
 }
 
 bool object_apply_global_props(Object *obj, const GPtrArray *props,
-- 
2.48.1

Re: [PATCH v2] qom: reverse order of instance_post_init calls

[Philippe Mathieu-Daudé]

On 6/2/25 10:58, Paolo Bonzini wrote:
> Currently, the instance_post_init calls are performed from the leaf
> class and all the way up to Object.  This is incorrect because the
> leaf class cannot observe property values applied by the superclasses;
> for example, a compat property will be set on a device *after*
> the class's post_init callback has run.
> 
> In particular this makes it impossible for implementations of
> accel_cpu_instance_init() to operate based on the actual values of
> the properties, though it seems that cxl_dsp_instance_post_init and
> rp_instance_post_init might have similar issues.
> 
> Follow instead the same order as instance_init, starting with Object
> and running the child class's instance_post_init after the parent.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   include/qom/object.h | 3 ++-
>   qom/object.c         | 8 ++++----
>   2 files changed, 6 insertions(+), 5 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>