Hi, On Sun, Aug 26, 2012 at 10:51:29AM -0500, Anthony Liguori wrote: > Right now, you need to pair up object_new with object_delete. This is > impractical when using reference counting because we would like to ensure that > object_unref() also frees memory when needed. > > The first few patches fix this problem by introducing a release callback so > that objects that need special release behavior (i.e. g_free) can do that. > > Since link and child properties all hold references, in order to actually free > an object, we need to break those links. User created devices end up as > children of a container. But child properties cannot be removed which means > there's no obvious way to remove the reference and ultimately free the object. > > We introduce the concept of "nullable child" properties to solve this. This > is > a child property that can be broken by writing NULL to the child link. Today > we set all /peripheral* children to be nullable so that they can be deleted by > management tools. > > In terms of modeling hotplug, we represent unplug by removing the object from > the parent bus. We need to register a notifier for when this happens so that > we can also remove the parent's child property to ultimately release the > object. > > Putting it all together, we have: > > 1) qmp_device_del will issue a callback to a device. The default callback > will > do a forced eject (which means writing NULL to the parent_bus link). > > 2) PCI hotplug is a bit more sophisticated in that it waits for the guest to > do the ejection. > > 3) qmp_device_del will register an eject notifier such that the device gets > completely removed. > > There's a slightly change in behavior here. A device is not automatically > destroyed based on a guest initiated eject. A management tool must explicitly > break the parent's link to the child in order for the device to disappear > completely. device_del behaves exactly as it does today though.
is there a plan to respin this series, or has it been dropped? Afaict it hasn't landed upstream. I am reworking an acpi memory hotplug RFC patchset, and noticed this patchset changes guest-initiated eject semantics. Currently a successfull guest-initiated eject in my mem-hotplug patchset destroys the qdev device. But the semantics of this patchset would require a new behaviour. thanks, - Vasilis
