Re: QEMU device refcounting when device creates a container MR

["Philippe Mathieu-Daudé" <philippe.mathieu.daude@gmail.com>]

Cc'ing David / Peter

On 9/3/22 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.
> 
> As a specific example, the usb-chipidea device does this in its
> init method, so if you run the arm device-introspect-test under
> leak-sanitizer it complains about a memory leak that happens
> when the device is put through the "init-introspect-deref" cycle.
> 
> -- PMM
>