It seems the use model is to enable older environment-swapping software to run on newer hardware without opening a security hole via new state. Only if the software is aware of the state will it enable that state via *stateen.

For custom state, you can always make custom *stateen-like CSRs to enable it. You're going to need custom software to swap that state anyway.

True.  I was thinking of unifying the two purposes when I asked the question.

      Bill