Patent ID: 7739434

Claim:
In a logically partitioned host computer system comprising host processors (host CPUs), a method for a configuration change of a topology of a plurality of guest processors (guest CPUs) of a guest configuration, the method comprising: a guest processor of the guest configuration fetching a perform topology function instruction defined for a computer architecture, the perform topology function instruction comprising a register field and an opcode field specifying a function to be performed; executing function to be performed of the perform topology function instruction comprising: obtaining from a function code field of a register specified by the register field, a function code field value, the function code field value consisting of any one of a horizontal polarization specifier, a vertical polarization specifier or a check of a topology change specifier; requesting a specified polarization change of the configuration of the topology of the guest processors of the guest configuration; responsive to the requested specified polarization change being accepted, initiating a change of the topology of the guest processors of the guest configuration according to the specified polarity change comprising a)-d): a) responsive to the specified polarization change specifying the horizontal polarization, initiating horizontal polarization of the guest processors of the computer configuration, thereby producing a resultant updated topology; and b) responsive to the specified polarization change specifying the vertical polarization, initiating vertical polarization of the guest processors of the computer configuration, thereby producing a resultant updated topology; c) setting a condition code to a first condition code value, the first condition code value indicating a topology-change initiated; and d) setting a result code value in a result field of the register; and responsive to the requested specified polarization change not being accepted, setting the condition code to a second condition code value, the second condition code value indicating a topology-change is rejected.