spapr: Use spapr_drc_reset_all() at machine reset

Documentation of object_child_foreach_recursive() clearly stipulates
that "it is forbidden to add or remove children from @obj from the @fn
callback". But this is exactly what we do during machine reset. The call
to spapr_drc_reset() can finalize the hot-unplug sequence of a PHB or a
PCI bridge, both of which will then in turn destroy their PCI DRCs. This
could potentially invalidate the iterator used by do_object_child_foreach().
It is pure luck that this haven't caused any issues so far.

Use spapr_drc_reset_all() since it can cope with DRC removal.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20201218103400.689660-5-groug@kaod.org>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -1566,19 +1566,6 @@ void spapr_setup_hpt(SpaprMachineState *spapr)
     }
 }
 
-static int spapr_reset_drcs(Object *child, void *opaque)
-{
-    SpaprDrc *drc =
-        (SpaprDrc *) object_dynamic_cast(child,
-                                                 TYPE_SPAPR_DR_CONNECTOR);
-
-    if (drc) {
-        spapr_drc_reset(drc);
-    }
-
-    return 0;
-}
-
 static void spapr_machine_reset(MachineState *machine)
 {
     SpaprMachineState *spapr = SPAPR_MACHINE(machine);
@@ -1633,7 +1620,7 @@ static void spapr_machine_reset(MachineState *machine)
      * will crash QEMU if the DIMM holding the vring goes away). To avoid such
      * situations, we reset DRCs after all devices have been reset.
      */
-    object_child_foreach_recursive(object_get_root(), spapr_reset_drcs, NULL);
+    spapr_drc_reset_all(spapr);
 
     spapr_clear_pending_events(spapr);