Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750853AbVKMTIY (ORCPT ); Sun, 13 Nov 2005 14:08:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750860AbVKMTIY (ORCPT ); Sun, 13 Nov 2005 14:08:24 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:38836 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1750846AbVKMTIX (ORCPT ); Sun, 13 Nov 2005 14:08:23 -0500 To: Andi Kleen Cc: Alan Cox , Dave Jones , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , Ingo Molnar , torvalds@osdl.org Subject: Re: [PATCH 1/10] Cr4 is valid on some 486s References: <200511100032.jAA0WgUq027712@zach-dev.vmware.com> <1131902775.25311.16.camel@localhost.localdomain> <200511132000.45836.ak@suse.de> From: ebiederm@xmission.com (Eric W. Biederman) Date: Sun, 13 Nov 2005 12:07:16 -0700 In-Reply-To: <200511132000.45836.ak@suse.de> (Andi Kleen's message of "Sun, 13 Nov 2005 20:00:44 +0100") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) 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 Content-Length: 1054 Lines: 31 Andi Kleen writes: > On Sunday 13 November 2005 18:26, Alan Cox wrote: > >> I'd hope the vendors are not doing that by default because we have >> kernel code that uses lock against not other processors but other bus >> masters. The ECC code is one example. > > It's a bad hack anyways. Better would be probably to use a uncached WC write. > I would rather use that. For read modify write? The point is to make the cache line dirty so that the memory controller will write the data back. The interesting sequence is: lock; addl $0, %(reg) I'm not actually sure the lock is even necessary. Mostly this is for brain-dead chipsets, chipsets you can't trust, or at least chipsets that won't do a background scrub for you. I don't think it is possible to do an uncached read modify write? Eric - 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/