Peter Maydell <peter.mayd...@linaro.org> writes: > On Fri, 17 Jan 2025 at 06:19, Akihiko Odaki <akihiko.od...@daynix.com> wrote: >> Let me explain my and Peter Xu's solutions by listing object references. >> It will abstract the details away and allow applying the analogy of >> other reference counting systems like Objective-C. >> <snip> >> "Weak" references >> ----------------- >> >> Next, I'll impose the restriction that prevents circular references. To >> avoid circular references, we'll stop counting references for one >> direction. In other words, we'll make some references "weak". Weak >> references are prone to be dangling (in Objective-C or other platforms, >> such references will be usually replaced with nil-like values). > > I'm not sure this is really how we think about the lifetimes > of these objects, though. In particular, we definitely don't > ever expect, for instance, the link from a memory region to > its owner to be dangling. > > I think what we actually have is: > * the thing which really has a reference count is the > device object > * this device owns various things (irqs, child objects, > memory regions, etc) > * we expect that when we destroy the device that all these > other things it owns also should be destroyed > * some parts of the system have free-floating memory regions > which don't have an owner > * parts of the code have to deal with both the "MR belonging > to a device" and the "MR not belonging to a device" case
The virtio-gpu blobs are a special MR which we handle clumsily at the moment as they are backed by separate thread (virglrenderer) and we need to jump through hoops (c.f. virtio_gpu_virgl_hostmem_region_free) to make sure it is done with the memory before we can free the container. <snip> -- Alex Bennée Virtualisation Tech Lead @ Linaro
