From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031588AbXEAFfn (ORCPT ); Tue, 1 May 2007 01:35:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031593AbXEAFfn (ORCPT ); Tue, 1 May 2007 01:35:43 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:49887 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031588AbXEAFfl (ORCPT ); Tue, 1 May 2007 01:35:41 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: William Lee Irwin III Cc: Andi Kleen , Mark Lord , patches@x86-64.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] [30/30] x86_64: Add missing !X86_PAE dependincy to the 2G/2G split. References: <20070501557.815359000@suse.de> <20070501035829.1C93D13CAF@wotan.suse.de> <20070501043735.GR31925@holomorphy.com> Date: Mon, 30 Apr 2007 23:35:27 -0600 In-Reply-To: <20070501043735.GR31925@holomorphy.com> (William Lee Irwin, III's message of "Mon, 30 Apr 2007 21:37:35 -0700") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org William Lee Irwin III writes: > On Tue, May 01, 2007 at 05:58:29AM +0200, Andi Kleen wrote: >> From: ebiederm@xmission.com >> When in PAE mode we require that the user kernel divide to be >> on a 1G boundary. The 2G/2G split does not have that property >> so require !X86_PAE >> Signed-off-by: Eric W. Biederman >> --- >> arch/i386/Kconfig | 1 + >> 1 files changed, 1 insertions(+), 0 deletions(-) > > What on earth? > > config PAGE_OFFSET > hex > default 0xB0000000 if VMSPLIT_3G_OPT > default 0x78000000 if VMSPLIT_2G > default 0x40000000 if VMSPLIT_1G > default 0xC0000000 > > This appears to have been introduced by: > commit 975b3d3d5b983eb60706d35f0d24cd19f6badabf > Author: Mark Lord > Date: Wed Feb 1 03:06:11 2006 -0800 > [PATCH] VMSPLIT config options > > There's some sort of insanity going on here. Since when is 0x78000000 > a 2GB/2GB split? Mark, dare I ask what you were thinking? That should > be VMSPLIT_2G_OPT for 2GB laptops analogously to VMSPLIT_3G_OPT, if > nothing else, as it's certainly not 2GB/2GB. It makes a little more sense when you realize all of the options were originally !X86_PAE. So they were designed with highmem disabled. > These VMSPLIT config options vs. PAE are foul as they're now done in > any event. If they were done properly, they'd properly set up the pmd > within which the division point between user and kernelspace falls. They were designed to avoid highmem a totally different design point. > This patch, I suppose, stops people from shooting themselves in the > foot, but (IMHO) the VMSPLIT patches shouldn't have been merged > without handling the partial pmd case. 2MB/4MB resolution is enough > granularity for any reasonable purpose, so split ptes aren't worth the > effort, but this nonsense with PAE vs. VMSPLIT is just preposterous. > If you're going to play the VMSPLIT game at all, handle split pmd's. What I find telling is that I fixed this based on code review not based on bug reports. > I'll see what else is pending in the i386 pagetable arena and clear > this up if there aren't other objections (this is where Andi gets to > complain that things are too complex already and preemptively NAK to > save me the effort, if it's not seen to be desirable). Eric, your patch > is a reasonable stop-gap measure for the original deficiency. Frankly rather then putting much effort into this I suspect we should just delete these options entirely. We are long past the point where they matter. Eric