From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751370Ab1JTWKw (ORCPT ); Thu, 20 Oct 2011 18:10:52 -0400 Received: from am1ehsobe001.messaging.microsoft.com ([213.199.154.204]:16974 "EHLO AM1EHSOBE001.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750992Ab1JTWKv (ORCPT ); Thu, 20 Oct 2011 18:10:51 -0400 X-SpamScore: -20 X-BigFish: VPS-20(zzbb2dK9371K936eK103dK1432N98dKzz1202hzz8275bhz32i668h839h93fh61h) X-Spam-TCS-SCL: 0:0 X-Forefront-Antispam-Report: CIP:163.181.249.108;KIP:(null);UIP:(null);IPVD:NLI;H:ausb3twp01.amd.com;RD:none;EFVD:NLI X-FB-SS: 0, X-WSS-ID: 0LTDXLT-01-4OV-02 X-M-MSG: Message-ID: <1319148647.13035.4.camel@jshin-Toonie> Subject: Re: [PATCH 1/1] x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping. From: Jacob Shin To: "H. Peter Anvin" CC: Andi Kleen , Thomas Gleixner , Ingo Molnar , Yinghai Lu , "Herrmann3, Andreas" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" Date: Thu, 20 Oct 2011 17:10:47 -0500 In-Reply-To: <4EA092DD.8020203@zytor.com> References: <1319145326-13902-1-git-send-email-jacob.shin@amd.com> <4EA092DD.8020203@zytor.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.0- Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-OriginatorOrg: amd.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-10-20 at 16:30 -0500, H. Peter Anvin wrote: > On 10/20/2011 02:28 PM, Andi Kleen wrote: > > Jacob Shin writes: > > > >> On systems with very large memory (1 TB in our case), BIOS may report a > >> reserved region or a hole in the E820 map, even above the 4 GB range. Exclude > >> these from the direct mapping. > > > > This doesn't make much sense. Holes above 4GB are completely legal. > > > > If you need to workaround a specific broken BIOS you would need a quirk > > only matching that system, with a suitable "BIOS is broken" message. > > > > The problem is that apparently right now we map those unconditionally > into the 1:1 map and mark them cacheable in PAT, which we *don't* for > the < 4 GiB map. > > This thus makes the behavior match < 4 GiB, which is the correct > behavior; this should be made clear in the patch description. Will something like: "On systems with very large memory (1 TB in our case), BIOS may report a reserved region or a hole in the E820 map, even above the 4 GB range. Avoid mapping them unconditionally into kernel 1:1 direct mapping as cacheable memory, as we also already do for the MMIO hole under 4 GB." Work? Otherwise, does the patch look acceptable? Thanks! -Jacob Shin Advanced Micro Devices, Inc. > > -hpa >