The STSI instruction should tell you. >From Principles of Operation, SA22-7832-05, page 10-114: Function Code Information Requested -------- ------------------------------------------------- 0 Current-configuration-level number 1 Information about level 1 (the basic machine) 2 Information about level 2 (a logical partition) 3 Information about level 3 (a virtual machine)...
So for a function code of zero: More from Principles of Operation: When the function code is 0, an unsigned binary integer identifying the current configuration level (1 for basic machine, 2 for logical partition, or 3 for virtual machine) is placed in bit positions 32-35 of general register 0, the condition code is set to 0, and no further action is performed.
