* Andy Lutomirski [off-list ref] wrote:

This garbage (as evidenced by my bug and my failed attempt to fix it)
only works if you never have a low-level page table that isn't linked
into a higher-level page table, and it mostly requires you to do
everything exactly the way it was originally done so all the horrible
inline helpers don't get confused.

And AFAICT all of this was done to manually unroll a loop, and I bet
it never sped anything up measurably even on 386 or PPro.

Whenever some vendor releases a 5 level page table CPU, can we
*please* clean this up first?  We should have a type that points to a
table, a different type that points to an entry (or maybe not have
pointers to entries at all), and the levels should be referred to by
*number*.  When you need to traverse all the way down, you write a
*loop* instead of four bloody helper functions, some of which are
incomprehensibly no-ops on some kernels.  And if this means that, on
Intel, we have a silly branch in the inner loop because the bottom
level entry format is special, who cares?
</rant>

I'd welcome (and help out!) any effort to clean it up gradually.

Thanks,

	Ingo