From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752652AbYCLFjT (ORCPT ); Wed, 12 Mar 2008 01:39:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751747AbYCLFjL (ORCPT ); Wed, 12 Mar 2008 01:39:11 -0400 Received: from neuf-infra-smtp-out-sp604007av.neufgp.fr ([84.96.92.120]:42733 "EHLO neuf-infra-smtp-out-sp604007av.neufgp.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751736AbYCLFjL (ORCPT ); Wed, 12 Mar 2008 01:39:11 -0400 Message-ID: <47D76C72.2080603@cosmosbay.com> Date: Wed, 12 Mar 2008 06:38:58 +0100 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.12 (Windows/20080213) MIME-Version: 1.0 To: Andi Kleen CC: andreas.herrmann3@amd.com, tglx@linutronix.de, mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [PATCH] [4/7] Don't use large pages to map the first 2/4MB of memory References: <20080312353.598285931@firstfloor.org> <20080312025330.AC1961B41D1@basil.firstfloor.org> In-Reply-To: <20080312025330.AC1961B41D1@basil.firstfloor.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen a écrit : > Intel recommends to not use large pages for the first 1MB > of the physical memory because there are fixed size MTRRs there > which cause splitups in the TLBs. > > On AMD doing so is also a good idea. > > The implementation is a little different between 32bit and 64bit. > On 32bit I just taught the initial page table set up about this > because it was very simple to do. This also has the advantage > that the risk of a prefetch ever seeing the page even > if it only exists for a short time is minimized. > > On 64bit that is not quite possible, so use set_memory_4k() a little > later (in check_bugs) instead. > > Signed-off-by: Andi Kleen > > --- > arch/x86/kernel/bugs_64.c | 12 ++++++++++++ > arch/x86/mm/init_32.c | 6 +++++- > 2 files changed, 17 insertions(+), 1 deletion(-) > Should we then change CONFIG_PHYSICAL_START from 0x100000 to 0x400000 ? Thank you