1. A computer implemented method for a configuration change of a topology of a plurality of guest processors (CPUs) of a guest configuration in a logically partitioned computer system, the method comprising: fetching, by a processor of the guest configuration, a perform topology function instruction defined for a computer architecture; executing the perform topology function instruction, wherein the perform topology function instruction comprises an opcode field and a register field for requesting a polarization change, the execution comprising: any one of initiating a change of the polarization of the processors of the guest configuration according to the requested polarization change or rejecting the polarization change request; and responsive to the initiating the change of the polarization of the processors of the guest configuration, setting a condition code to a value indicating a polarization change is initiated, and responsive to the rejecting the polarization change request, setting the condition code to a second value indicating said change request is rejected.