Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756225AbZJSNzP (ORCPT ); Mon, 19 Oct 2009 09:55:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756156AbZJSNzO (ORCPT ); Mon, 19 Oct 2009 09:55:14 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:34824 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756021AbZJSNzN (ORCPT ); Mon, 19 Oct 2009 09:55:13 -0400 Date: Mon, 19 Oct 2009 15:54:22 +0200 From: Ingo Molnar To: Suresh Siddha Cc: Jan Beulich , Thomas Schlichter , Jeremy Fitzhardinge , Robert Hancock , Henrique de Moraes Holschuh , "Pallipadi, Venkatesh" , Tejun Heo , "x86@kernel.org" , Yinghai Lu , Thomas Gleixner , Arjan van de Ven , "dri-devel@lists.sourceforge.net" , Ingo Molnar , "linux-kernel@vger.kernel.org" , "jbarnes@virtuousgeek.org" , Thomas Hellstrom , "H. Peter Anvin" Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not available Message-ID: <20091019135422.GA9921@elte.hu> References: <4AD449A702000078000197EE@vpn.id2.novell.com> <200910142114.12433.thomas.schlichter@web.de> <4AD6EFD7020000780001A067@vpn.id2.novell.com> <200910172148.36267.thomas.schlichter@web.de> <4ADC4A76020000780001AA49@vpn.id2.novell.com> <1255959874.2823.46.camel@sbs-t61> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1255959874.2823.46.camel@sbs-t61> User-Agent: Mutt/1.5.19 (2009-01-05) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1178 Lines: 30 * Suresh Siddha wrote: > On Mon, 2009-10-19 at 02:16 -0700, Jan Beulich wrote: > > Functionality-wise this looks fine to me > > If we are going to make ioremap() and set_memory_wc() add mtrr's in > non-pat case, then we need to delete the added mtrr(s) in the > corresponding iounmap() and set_memory_wb() aswell. > > hmm, this is becoming too complex. The way i915 and other graphics > drivers are using set_memory_wc(), it is def a bad idea to start > adding mtrr's behind the back for non-pat case. Touching MTRRs beyond working around basic bugs like non-cached RAM sounds like madness. The interactions with PAT are ... countless. > Can't we just force PAT option always and we probably don't care about > ioremap_wc() on processors were PAT doesn't get enabled because of > known errata. We can make PAT configurability dependent on EMBEDDED-y - mind sending a patch for that? Ingo -- 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/