From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753764AbYIFPuJ (ORCPT ); Sat, 6 Sep 2008 11:50:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752133AbYIFPt5 (ORCPT ); Sat, 6 Sep 2008 11:49:57 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:47575 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752118AbYIFPt4 (ORCPT ); Sat, 6 Sep 2008 11:49:56 -0400 Date: Sat, 6 Sep 2008 17:49:35 +0200 From: Ingo Molnar To: David Woodhouse Cc: linux-kernel@vger.kernel.org, andi@firstfloor.org, arjan@infradead.org, torvalds@linux-foundation.org, sfr@canb.auug.org.au, Jesse Barnes Subject: Re: [PATCH] Blacklist DMAR on Intel G31/G33 chipsets Message-ID: <20080906154935.GD1774@elte.hu> References: <1220439231.2985.103.camel@pmac.infradead.org> <1220518477.2985.163.camel@pmac.infradead.org> <20080905183459.GC14258@elte.hu> <1220640430.2985.389.camel@pmac.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1220640430.2985.389.camel@pmac.infradead.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * David Woodhouse wrote: > On Fri, 2008-09-05 at 20:34 +0200, Ingo Molnar wrote: > > * David Woodhouse wrote: > > > > > Some BIOSes (the Intel DG33BU, for example) wrongly claim to have DMAR > > > when they don't. Avoid the resulting crashes when it doesn't work as > > > expected. > > > > > > Signed-off-by: David Woodhouse > > > --- > > > > > > This time, I build-tested it with CONFIG_DMAR actually enabled. Sorry. > > > I'd still be grateful if someone could test it on a DG33BU with the > > > old BIOS though, since I've killed mine. I tested the DMI version, but > > > not this one. > > > > ok - fixing this makes sense. I have two worries about this patch. > > > > Firstly, the quirk is keyed off an ACPI capability which is quite bad if > > someone boots with ACPI off. (which is still quite possible) The DMAR is > > PCI enumerated so there's nothing inherently ACPI about this. A DMI > > quirk (which will work even if ACPI is disabled) looks more robust. > > No, the intel-iommu code is isn't PCI-enumerated -- it all depends on > that ACPI table, unfortunately. [...] ah, you are right ... and i thought i could trust grep -i acpi drivers/pci/intel-iommu.c coming up empty ;-) Jesse's call obviously, but the DMI thing local to intel-iommu.c still looks better to me in all regards. I'm no fan of DMI in general - it just doesnt scale - but here a crappy BIOS gets punished with a DMI quirk and that's OK. Ingo