1. In a logically partitioned host computer system comprising host processors (host CPUs), a method for discovering topology of one or more guest processors (guest CPUs) of a guest configuration, the method comprising: a guest processor of the guest configuration fetching a STORE SYSTEM INFORMATION instruction for execution, the STORE SYSTEM INFORMATION instruction defined for a computer architecture; executing the STORE SYSTEM INFORMATION, wherein the STORE SYSTEM INFORMATION instruction comprises an opcode field and a base register field, the base register field for identifying' a location in memory of a configuration topology table, the execution comprising: based on a topology information request of the STORE SYSTEM INFORMATION instruction, obtaining topology information of the computer configuration wherein the topology information comprising nesting information of processors of the configuration; and storing the topology information in the configuration topology table.