Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753762AbXHHPwd (ORCPT ); Wed, 8 Aug 2007 11:52:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752819AbXHHPwZ (ORCPT ); Wed, 8 Aug 2007 11:52:25 -0400 Received: from nz-out-0506.google.com ([64.233.162.232]:15862 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844AbXHHPwY convert rfc822-to-8bit (ORCPT ); Wed, 8 Aug 2007 11:52:24 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=OABvZn0/pgY7fYticdniOiUpiAYHg3zss39k3v0ttplQDqTrHuXBhQonVB0HlEuJT90InuJh5xwQuoQyUkl7xcZkx7TVcjkvAixqI1ynDcAFlC9Xb5lQLMtd9iWWy1O8/sbOmv1AoQYrdLRu/klu4wjLZGNCY4i8i7O8J2E6qiE= Message-ID: Date: Wed, 8 Aug 2007 11:52:23 -0400 From: "=?ISO-8859-1?Q?C=E9dric_Augonnet?=" To: "Andi Kleen" Subject: Re: PAT support for i386 and x86_64 Cc: "Loic Prylli" , "Linux Kernel Mailing List" , "Andrew Morton" , brice@myri.com, cedric.augonnet@ens-lyon.org In-Reply-To: <20070808101441.GA12861@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline References: <20070807083004.GB30085@one.firstfloor.org> <46B97E39.3020905@myri.com> <20070808101441.GA12861@one.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1670 Lines: 44 [Apologize for the double-post, messed up with my mailer... ] 2007/8/8, Andi Kleen : > > I don't see why we have to worry about cache corruption in the case at > > hand. Write-combining is needed to map io (typically pci-mem regions) > > which are never mapped cachable anywhere, including in the linear map. > > If we WC them using PAT then there would be a UC<->WC conflict with > the direct mapping and possibly others. That's already undefined > and not allowed. > > After some very bad experiences in the past I'm not going to take > chances on this. > > We really need to keep all possible mappings synchronized. > > -Andi > > Hi, First thanks for your reactions. Andi, what i don't understand is, if we only put a minimal patch, like only modifying the register, perhaps we may avoid having all vendors doing their own recipe, possibly all messing the one the other. As you said , changing this register is absolutely not the actual issue with PAT, but don't you think such a first step is needed to avoid conflicts since people _do_ already set that register from their driver. I agree there is work for a comprehensive support of PAT, especially when dealing with ioremap, but even though we only handle a smallish portion of the problem yet, perhaps it's time to at least modify that register ? Of course there is no problem for that being dependant on a CONFIG_PAT. Kind regards, C?dric - 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/