On Wed, 9 Mar 2022 at 16:21, Paolo Bonzini <pbonz...@redhat.com> wrote: > > On 3/9/22 11:33, Peter Maydell wrote: > > Hi; does anybody know how device reference counting is supposed > > to work when the device creates a "container" MemoryRegion which > > it then puts some of its own subregions in to? > > > > As far as I can see when you do memory_region_add_subregion it > > increases the refcount on the owner of the subregion. So if a > > device creates a container MR in its own init or realize method > > and adds sub-MRs that it owns to that container, this increases > > the refcount on the device permanently, and so the device won't > > ever be deinited. > > The unparent method is supposed to break reference cycles. > > In the case of QOM, unparent calls unrealize, so unrealize should remove > the subregions it created.
It seems asymmetric for unrealize to undo something that was done in instance_init, though. I would expect unrealize to undo the effects of realize, and instance_finalize to undo the effects of instance_init. -- PMM
