1. A method of determining whether a logical processor of an information processing system has access to an address space of the information processing system, comprising: a) issuing an instruction by a first processor, the instruction referencing a target logical processor and a target address space; b) in response to the instruction, checking first information to determine whether the target logical processor is running; and c) when it is determined that the target logical processor is not running, checking second information by a host program to determine whether the target logical processor has access to the target address space.