Re: PTE access rules & abstraction

[David Miller <davem@davemloft.net>]

From: Nick Piggin <npiggin@suse.de>
Date: Tue, 23 Sep 2008 05:10:37 +0200

> Part of the problem with the pte API (as well as the cache flush and
> tlb flush APIs) is that it often involves the core mm code telling
> the arch how it thinks ptes,tlbs,caches should be managed, rather than
> I think the better approach would be telling the arch what it wants to
> do.
> 
> We are getting better slowly I think (eg. you note that set_pte_at is
> no longer used as a generic "do anything"), but I won't dispute that
> this whole area could use an overhaul; a document for all the rules,
> a single person or point of responsibility for those rules...

I agree.

To a certain extent this is what BSD does in it's pmap layer, except
that they don't have the page table datastructure abstraction like
Linus does in the generic code, and which I think was a smart design
decision on our side.

All of the pmap modules in BSD are pretty big and duplicate a lot of
code that arch's don't have to be mindful about under Linux.