The differentiator is typically not privileged vs non-privileged. It's interceptable vs non-interceptable. That's the "normal" state of affairs for z/VM.
But many instructions (such as those in the miscellaneous instruction execution facilities that have come into play over the course of many machine generations) are not interceptable. For such instructions, z/VM sees nothing about them. But the virtual architecture level must control whether those instructions are made available or get an operation exception. It does seem like there must be some overhead with accommodating that. Anyway, back to "dial down", according to Tony T you define a relocation domain. If that domain needs to consist of actual machines, then I guess you can't do what is desired. If you could define a domain to include a machine that does not actually exist (but for which you could identify what machine it was supposed to be) that would work, because of course you would never truly relocate there. I suppose it might not let you do that... What you really want is to be able to define the virtual architecture level that a guest is to use. Peter Relson z/OS Core Technology Design
