Wait wait wait...so it effectively memory maps all the things?
Mainframe environments are weird.
Mainframe environments are weird.
Or the OS/360 which uses virtualization for all OSs, like Hyper V does on Windows.
The first OS to boot from the hypervisor has master rights, but all OSs are virtualized.
No, the hypervisor was called VM. According to WP it most frequently ran CMS guests, which was a light weight single-app OS. But could also run OS/360 guests (which predated VM).