Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763794AbYASD3U (ORCPT ); Fri, 18 Jan 2008 22:29:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759879AbYASD3L (ORCPT ); Fri, 18 Jan 2008 22:29:11 -0500 Received: from mx1.redhat.com ([66.187.233.31]:39379 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756454AbYASD3K (ORCPT ); Fri, 18 Jan 2008 22:29:10 -0500 Date: Fri, 18 Jan 2008 22:28:49 -0500 From: Dave Jones To: Ingo Molnar Cc: Yinghai Lu , venkatesh.pallipadi@intel.com, LKML Subject: Re: [PATCH] X86: fix typo PAT to X86_PAT Message-ID: <20080119032849.GA16757@redhat.com> Mail-Followup-To: Dave Jones , Ingo Molnar , Yinghai Lu , venkatesh.pallipadi@intel.com, LKML References: <20080118123140.GI11044@elte.hu> <20080118182437.GA10167@redhat.com> <20080118210210.GB10717@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080118210210.GB10717@elte.hu> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1662 Lines: 37 On Fri, Jan 18, 2008 at 10:02:10PM +0100, Ingo Molnar wrote: > > * Dave Jones wrote: > > > > you mean modifies MTRRs? Which code is that? (besides the > > > /proc/mtrr userspace API) > > > > This exclusion is going to be a real pain in the ass for distro > > kernels. It's impossible for example to build a kernel that will now > > support the MTRR-alike registers on the AMD K6/early Cyrix etc and > > also support PAT. > > > > Additionally, given people tend to update their kernels a lot more > > often than they update to a whole new version of X, it means until > > userspace has caught up, we can't ship a kernel with PAT supported, or > > else X gets a lot slower due to the missing mtrr support. > > there's no exclusion enforced right now, and if a CPU is PAT-incapable > (or if the kernel is booted nopat) then the MTRR bits should be usable. > But if we boot with PAT enabled, and Xorg gets /proc/mtrr wrong, we'll > see nasty crashes. If it gets them right, it should all still work just > fine. Is this ok? Then, in a year or two, distros can disable write > support to /proc/mtrr. Hm? A crazy idea just occured to me.. We could make /proc/mtrr an interface to set PAT on a range of memory. This would make it transparently work without any changes in X or anything else that sets them in userspace. Dave -- http://www.codemonkey.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/