Re: CP == Hypervisor
re: My VM sysprog friends joked that running MVS under VM was the only proper way to run MVS.
What do you mean that your friends joked? Nowadays it is the only way.
Bare metal z mainframes don't run operating systems anymore.
For many years now, the only way on a z mainframe to run an operating system, such as z/OS, (a successor to MVS,) is to run it in a "logical partition" under the PR/SM hypervisor, which is a successor to a stripped down version of VM.