1. A method for yielding a virtual processor within a logically partitioned data processing system, wherein the system supports a plurality of partitions, a first of which includes a plurality of virtual processors that share at least one CPU, the method comprising: requesting with a yielding virtual processor a yield of the CPU upon which the virtual processor is executing, including designating a target virtual processor from among the plurality of virtual processors; and switching-in the target virtual processor for execution by the CPU in response to the requested yield.