On Tue, 4 Feb 2025 at 15:08, Philippe Mathieu-Daudé <phi...@linaro.org> wrote:
>
> Hi Paolo,
>
> On 3/2/25 12:41, 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 <pbonz...@redhat.com>
> > ---
> > qom/object.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/qom/object.c b/qom/object.c
> > index 157a45c5f8b..c03cd3c7339 100644
> > --- a/qom/object.c
> > +++ b/qom/object.c
> > @@ -423,13 +423,13 @@ 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);
> > + }
> > }
>
> I'm not opposed to this change as I had a similar issue there few weeks
> ago, but I feel we are changing one problem by another. IIRC some class
> post_init() handlers check the instance correctly did something. But I
> don't recall any example in particular. The documentation isn't clear
> about order (include/qom/object.h):
>
> * @instance_post_init: This function is called to finish
> * initialization of an object, after
> * all @instance_init functions were
> * called.
We have five users of instance_post_init in the tree, if I'm not
miscounting. So we should be able to audit them all for whether they
care about the order and/or are currently doing things in the wrong
order.
And yes, we should update the documentation if we're picking
a specific ordering :-)
thanks
-- PMM
