hmm, yes. You do get this and mysterious SEGV if you hit the but so does
other bugs too so this is probably due to missing invalidation.

I suspect that something like below will fix the problem and
is the "correct" fix(untested, not even compiled):

Ok but do we also still have to worry about the "unpopulated" TLB
entries and invalidate them somehow when populating ?

Cheers,
Ben.