Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751476AbVK3R3z (ORCPT ); Wed, 30 Nov 2005 12:29:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751478AbVK3R3z (ORCPT ); Wed, 30 Nov 2005 12:29:55 -0500 Received: from ns.suse.de ([195.135.220.2]:46009 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1751476AbVK3R3y (ORCPT ); Wed, 30 Nov 2005 12:29:54 -0500 To: Daniel J Blueman Cc: linux-kernel@vger.kernel.org, jgarzik@pobox.com Subject: Re: PAT status? References: <6278d2220511300404i27878f02mf5d8c948256d36e8@mail.gmail.com> From: Andi Kleen Date: 30 Nov 2005 14:58:20 -0700 In-Reply-To: <6278d2220511300404i27878f02mf5d8c948256d36e8@mail.gmail.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 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: 979 Lines: 19 Daniel J Blueman writes: > IIRC, the kernel (c. 2.6.14) still does nothing to setup the > processors' PAT registers to enable write combining in one of the > slots - the defaults the BIOS establishes do not cover this. Once this > is done, drivers would readily be able to set page flags for a > particular PAT slot, and MTRRs can (almost) be safely ignored. As usual when something hasn't been done yet it's not that easy... Problem is that they would very likely create very subtle problems by creating conflicting mappings with the different cache attributes, which leads to cache corruption and other nasty issues. That is why more infrastructure is needed in the kernel to do this properly. -Andi - 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/