Re: all class init functions for all types in QEMU are called in select_machine(). Expected?

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/12/21 10:31 AM, Claudio Fontana wrote:
> Hello Paolo and all,
> 
> while debugging a class init ordering issue, I noticed that
> 
> _all_ class init functions for all types registered in the QEMU QOM are called in select_machine().
> Expected?
> 
> In particular it happens here:
> 
> static MachineClass *select_machine(void)
> {
>     GSList *machines = object_class_get_list(TYPE_MACHINE, false);
> 
> 
> object_class_get_list() ->
>   object_class_foreach() ->
>     g_hash_table_foreach() ->
>       object_class_foreach_tramp ->
>         type_initialize(type);
> 
> 
> Is this really desired? It looks suspect to me.
> 
> (gdb) bt
> #0  0x0000555555db613f in arm_v7m_class_init (oc=0x555556dca320, data=0x555556a926e0 <arm_tcg_cpus+288>)
>     at ../target/arm/tcg/tcg-cpu-models.c:849
> #1  0x0000555555f1deba in type_initialize (ti=0x555556d5b2f0) at ../qom/object.c:364
> #2  0x0000555555f1f62a in object_class_foreach_tramp (key=0x555556d5b470, value=0x555556d5b2f0, opaque=0x7fffffffda20)
>     at ../qom/object.c:1069
> #3  0x00007ffff6562000 in g_hash_table_foreach () at /usr/lib64/libglib-2.0.so.0
> #4  0x0000555555f1f709 in object_class_foreach (fn=
>     0x555555f1f866 <object_class_get_list_tramp>, implements_type=0x555556381b09 "machine", include_abstract=false, opaque=0x7fffffffda70)
>     at ../qom/object.c:1091
> #5  0x0000555555f1f8e4 in object_class_get_list (implements_type=0x555556381b09 "machine", include_abstract=false) at ../qom/object.c:1148
> #6  0x0000555555debe94 in select_machine () at ../softmmu/vl.c:1607
> 
> 
> If not here, where should be the right place, for example, for CPU class inits to be called?
> 
> At the very least I would put a comment there around the beginning of select_machine() saying:
> 
> /* all types, all classes in QOM are initialized here, as a result of the object_class_get_list call */
> 
> Wdyt?

Are you trying to register types conditionally?