1. A method of administering registered virtual addresses in a hybrid computing environment, the hybrid computing environment comprising a host computer having a host computer architecture, an accelerator having an accelerator architecture, the accelerator architecture optimized, with respect to the host computer architecture, for speed of execution of a particular class of computing functions, the host computer and the accelerator adapted to one another for data communications by a system level message passing module, the method comprising: maintaining, by an operating system, a watch list of ranges of currently registered virtual addresses; upon a change in physical to virtual address mappings of a particular range of virtual addresses falling within the ranges of the currently registered virtual addresses included in the watch list, notifying the system level message passing module by the operating system of the change; and updating, by the system level message passing module, a cache of ranges of currently registered virtual addresses to reflect the change in physical to virtual address mappings.