Re: OSv Vis-à-vis CMS
CMS started life independent of the original CP-67 hypervisor development, so it is not a good comparison. GCS, OTOH, was later developed to provide all the MVS facilities needed to support the port of VTAM into the VM suite of products. CMS maintained its ability to be IPLed on bare metal for long time, but GCS never had that ability (or need). CMS did have some MVS (and VSE) facilities including VSAM but nowhere near what was needed for VTAM, particularly multiple task support (process in POSIX-speak).
I have the beard, too (moustache isn't grey, though) and started working with VM around 1978. The VM community inside and outside IBM developed virtualization into a powerful paradigm despite much resistance inside IBM and that history is well-documented. A major pillar was the VM-specific hardware development throughout the process that provided crucial performance gains and also allowed the hypervisor to itself be IPLed in a virtual machine. To our minds, z/VM provides industrial-strength virtualization, as the number of busy Linux instances a mainframe could handle with great stability even over a decade ago testifies. In general we would like to see desktop computers get there, too, while hoping mainframe virtualization will always continue to lead the way.