Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964787AbVKMHnP (ORCPT ); Sun, 13 Nov 2005 02:43:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964850AbVKMHnO (ORCPT ); Sun, 13 Nov 2005 02:43:14 -0500 Received: from mx1.redhat.com ([66.187.233.31]:58012 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S964787AbVKMHnO (ORCPT ); Sun, 13 Nov 2005 02:43:14 -0500 Date: Sun, 13 Nov 2005 02:42:41 -0500 From: Dave Jones To: Linus Torvalds Cc: Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [PATCH 1/10] Cr4 is valid on some 486s Message-ID: <20051113074241.GA29796@redhat.com> Mail-Followup-To: Dave Jones , Linus Torvalds , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar References: <200511100032.jAA0WgUq027712@zach-dev.vmware.com> <20051111103605.GC27805@elf.ucw.cz> <4374F2D5.7010106@vmware.com> <4374FB89.6000304@vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1506 Lines: 41 On Fri, Nov 11, 2005 at 12:22:07PM -0800, Linus Torvalds wrote: > > > On Fri, 11 Nov 2005, Zachary Amsden wrote: > > > > Yes, this is fine, but is it worth writing the feature discovery code? I > > suppose it doesn't matter, as it gets jettisoned after init. I guess it is > > just preference. > > Well, you could do the feature discovery by trying to take a fault early > at boot-time. That's how we verify that write-protect works, and how we > check that math exceptions come in the right way.. > > > Could we consider doing the same with LOCK prefix for SMP kernels booted on > > UP? Evil grin. > > Not so evil - I think it's been discussed. Not with alternates (not worth > it), but it wouldn't be hard to do: just add a new section for "lock > address", and have each inline asm that does a lock prefix do basically > > 1: > lock ; xyzzy > > .section .lock.address > .long 1b > .previous > > and then just walk the ".lock.address" thing and turn all locks into 0x90 > (nop). Looks like the Ubuntu people already did this... http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-2.6.git;a=commitdiff;h=048985336e32efe665cddd348e92e4a4a5351415;hp=1cb630c2b5aaad7cedaa78aa135e6cecf5ab91ac Dave - 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/