Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756209AbZJSNpH (ORCPT ); Mon, 19 Oct 2009 09:45:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756161AbZJSNpG (ORCPT ); Mon, 19 Oct 2009 09:45:06 -0400 Received: from mga11.intel.com ([192.55.52.93]:42421 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755629AbZJSNpF (ORCPT ); Mon, 19 Oct 2009 09:45:05 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,585,1249282800"; d="scan'208";a="505038271" Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not available From: Suresh Siddha Reply-To: Suresh Siddha To: Jan Beulich Cc: 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" In-Reply-To: <4ADC4A76020000780001AA49@vpn.id2.novell.com> 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> Content-Type: text/plain Organization: Intel Corp Date: Mon, 19 Oct 2009 06:44:34 -0700 Message-Id: <1255959874.2823.46.camel@sbs-t61> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 972 Lines: 26 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. 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. or Perhaps just try to add mtrr only for the pci mmap case like the 4th patch in this series.. thanks, suresh -- 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/