From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753095Ab0CQIsn (ORCPT ); Wed, 17 Mar 2010 04:48:43 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:46001 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751981Ab0CQIsk (ORCPT ); Wed, 17 Mar 2010 04:48:40 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Message-ID: <4BA0973A.5070701@jp.fujitsu.com> Date: Wed, 17 Mar 2010 17:47:54 +0900 From: Kenji Kaneshige User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: Bjorn Helgaas CC: Jesse Barnes , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Yanko Kaneti , Linus Torvalds , Thomas Renninger , maciej.rutecki@gmail.com Subject: Re: [PATCH v1 2/3] x86/PCI: trim _CRS windows when they conflict with previous reservations References: <20100311235954.4355.23100.stgit@bob.kio> <20100312000114.4355.58189.stgit@bob.kio> <4BA04BB9.2090501@jp.fujitsu.com> <1268799725.13147.29.camel@dc7800.home> In-Reply-To: <1268799725.13147.29.camel@dc7800.home> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Bjorn Helgaas wrote: > On Wed, 2010-03-17 at 12:25 +0900, Kenji Kaneshige wrote: >> Bjorn Helgaas wrote: >>> Yanko's GA-MA78GM-S2H (BIOS F11) reports a host bridge window that overlaps >>> system memory: >>> >>> PCI window: [mem 0xcff00000-0x10ed0ffff] >>> System RAM: [mem 0x100000000-0x22fffffff] >>> >>> We can be pretty confident that the System RAM region is correct (if it >>> were wrong, we'd crash as soon as we tried to use any memory in that area), >>> so this patch tries to correct the PCI window by trimming it so it doesn't >>> conflict with any previous reservations. >> Though I might misunderstand something, it looks Yanko's machine specific >> workaround. I'm wondering if trimming _CRS is a generic workaround for >> broken _CRS machine. >> >> How about doing this when GA-MA78GM-S2H (BIOS F11) (and known machines >> that have the same problem) is detected? Or how about switching nocrs >> mode if the problem (resource conflict) is detected? > > It's certainly a possibility to do this only for specific machines, but > I'd like to avoid tripping over issues one-by-one. > > I think there are three ways to address BIOS _CRS defects: > > 1) Ship an OEM-specific host bridge driver > 2) Put a platform- or BIOS-specific quirk into Windows "into Linux"? > 3) Change the BIOS > > The first two sound like such a hassle to me that I doubt they would be > practical. I agree. For 1), we need OEM-specific driver, not chipset specific driver. For 2), I thought it depends on how many machines with broken _CRS are there, and I didn't think there are so many, but... > > But it's clear that there are systems like this with what appear to be > _CRS defects. It's quite possible that it's not really a defect, and we > just don't understand how to parse _CRS correctly yet. Or, Windows > might have a few heuristics to clean up obvious errors. Indeed, it might be true. Now I realize I need to change my opinion about 2). > > For example, I think Windows aligns host bridge windows, as documented > here: http://bugzilla.kernel.org/show_bug.cgi?id=14337 > > I think Windows also knows to ignore the Consumer/Producer bit in > Address Space Descriptors, and assume that all resources on bridges are > Producers. > > Hmm, what we really need is a way to run Windows in a virtualized > environment where we could manipulate the _CRS method and see what > Windows does with it... > > Anyway, I'd like to make Linux behave as much like Windows as possible > in this area so we can take advantage of all the testing that's done > with Windows. Okey, thank you very much for explanation. I understood the background of your change. Thanks, Kenji Kaneshige