XenBus machines have almost no hotplug support
In virt
arm machine, the hotplug handler does pre-plug checks and initializes devices on the ->plug
callback (in total it handles ->pre_plug,->plug,->unplug_request,->unplug
), while the generic xen bus hotplug handler does almost nothing at all (it only handles ->unplug_request). This is a problem for devices which contain validation logic for the pre-plug and plug phases, e.g. the NVDIMM device. An nvdimm device can be instantiated in a Xen Arm machine with invalid settings.