Has anyone ever used the internal MMU/PID systems of the ESP32?

[hjalfi]

I've been looking at doing a Fuzix port to the ESP32, and have been investigating using the MMU. It seems to be oddly restrictive, and the PID system which goes with it is rather peculiar --- limitations such as not being able to access the compiler helper routines in the ROM while the MMU is active will cause problems.

Has anyone used either of these in real life? I can't find any references online, and am looking for actual working code. In particular, while the PID system is documented, it'd be nice to have some actual use cases.