From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755941AbYJEAqs (ORCPT ); Sat, 4 Oct 2008 20:46:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754053AbYJEAqi (ORCPT ); Sat, 4 Oct 2008 20:46:38 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54581 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755839AbYJEAqi (ORCPT ); Sat, 4 Oct 2008 20:46:38 -0400 Message-ID: <48E80E60.8080106@zytor.com> Date: Sat, 04 Oct 2008 17:46:24 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Yinghai Lu CC: Ingo Molnar , Thomas Gleixner , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] x86: mtrr_cleanup: first 1M should be coverred in var mtrrs References: <1223157033-30217-1-git-send-email-yhlu.kernel@gmail.com> <1223157033-30217-2-git-send-email-yhlu.kernel@gmail.com> In-Reply-To: <1223157033-30217-2-git-send-email-yhlu.kernel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Yinghai Lu wrote: > + /* > + * [0, 1M) should always be coverred by var mtrr with WB > + * and fixed mtrrs should take effective before var mtrr for it > + */ > + nr_range = add_range_with_merge(range, nr_range, 0, > + (1ULL<<(20 - PAGE_SHIFT)) - 1); > + /* sort the ranges */ > + sort(range, nr_range, sizeof(struct res_range), cmp_range, NULL); > + The first 1 MB is a total don't care for the variable MTRRs -- they don't have to be covered *or* uncovered, since the entire first 1 MB is addressed by fixed MTRRs. In practice, it is *likely* that you're going to want to merge it with a WB MTRR, but with various vendors doing all kinds of strange things on EFI-damaged platforms, it may not always be that way. -hpa