linux-kernel - Re: PTE access rules & abstraction

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Message-Id: <1222294620.5968.4.camel@localhost>
Date:	Thu, 25 Sep 2008 00:17:00 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: PTE access rules & abstraction

On Wed, 2008-09-24 at 19:45 +0100, Hugh Dickins wrote:
> > I know s390 has different issues & constraints. Martin told me during
> > Plumbers that mprotect was probably also broken for him.
> 
> Then I hope he will probably send Linus the fix.
> 
> Though what we already have falls somewhat short of perfection,
> I've much more enthusiasm for fixing its bugs, than for any fancy
> redesign introducing its own bugs.  Others have more stamina!

As far as I can tell the current code should work. It is not pretty
though, in particular the nasty pairing of flush_tlb_mm() with
ptep_set_wrprotect() and flush_tlb_range() with change_protection() is
fragile. For me the question is if we can find a sensible set of basic
primitives that work for all architectures in a performant way. This is
really hard..

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.


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