From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753547AbZBEU55 (ORCPT ); Thu, 5 Feb 2009 15:57:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752181AbZBEU5s (ORCPT ); Thu, 5 Feb 2009 15:57:48 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:40672 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751984AbZBEU5r (ORCPT ); Thu, 5 Feb 2009 15:57:47 -0500 Date: Thu, 5 Feb 2009 21:57:35 +0100 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: Hugh Dickins , William Lee Irwin III , Linux Kernel Mailing List , Linux Memory Management List Subject: Re: pud_bad vs pud_bad Message-ID: <20090205205735.GA21500@elte.hu> References: <498B2EBC.60700@goop.org> <20090205184355.GF5661@elte.hu> <498B35F9.601@goop.org> <20090205191017.GF20470@elte.hu> <498B4F1F.5070306@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <498B4F1F.5070306@goop.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > Hugh Dickins wrote: >> However... I forget how the folding works out. The pgd in the 32-bit >> PAE case used to have just the pfn and the present bit set in that >> little array of four entries: if pud_bad() ends up getting applied >> to that, I guess it will blow up. >> > > Ah, that's a good point. > >> If so, my preferred answer would actually be to make those 4 entries >> look more like real ptes; but you may think I'm being a bit silly. > > Hardware doesn't allow it. It will explode (well, trap) if you set > anything other than P in the top level. Yeah. I was the first Linux hacker in history to put a x86 CPU into PAE mode under Linux 10+ years ago, and i can attest to the 'explodes way too easily' aspect quite emphatically ;-) Took me 3-4 days to bootstrap it. > By the by, what are the chances we'll be able to deprecate non-PAE 32-bit? For the next 10 years: pretty much zero. Ingo