Using the example above, if a CPU core is overheating, can you down clock that core using and instruction run on another core? I don't actually know that much about how the hardware actually works at that level, so I am genuinely asking.
IIRC clock control doesn't need to be done in SMM, especially PROCHOT which is a hardwired thermal shutdown. That said, power management is one of the things SMM was originally designed for, so it may be used for some of that.