Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763780Ab3DDROz (ORCPT ); Thu, 4 Apr 2013 13:14:55 -0400 Received: from mail-oa0-f44.google.com ([209.85.219.44]:33798 "EHLO mail-oa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763760Ab3DDROw (ORCPT ); Thu, 4 Apr 2013 13:14:52 -0400 MIME-Version: 1.0 In-Reply-To: <20130404153905.GB3403@neilslaptop.think-freely.org> References: <1362158276-4901-1-git-send-email-nhorman@tuxdriver.com> <1362423859-18516-1-git-send-email-nhorman@tuxdriver.com> <1365085649.28127.66.camel@i7.infradead.org> <20130404145012.GA3403@neilslaptop.think-freely.org> <20130404153905.GB3403@neilslaptop.think-freely.org> From: Bjorn Helgaas Date: Thu, 4 Apr 2013 11:14:30 -0600 Message-ID: Subject: Re: [PATCH v2] irq: add quirk for broken interrupt remapping on 55XX chipsets To: Neil Horman Cc: David Woodhouse , Prarit Bhargava , Don Zickus , Jiang Liu , Asit Mallick , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , iommu@lists.linux-foundation.org, Yinghai Lu Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3065 Lines: 65 On Thu, Apr 4, 2013 at 9:39 AM, Neil Horman wrote: > On Thu, Apr 04, 2013 at 08:57:06AM -0600, Bjorn Helgaas wrote: >> On Thu, Apr 4, 2013 at 8:50 AM, Neil Horman wrote: >> > On Thu, Apr 04, 2013 at 03:27:29PM +0100, David Woodhouse wrote: >> >> On Wed, 2013-04-03 at 17:53 -0600, Bjorn Helgaas wrote: >> >> > ); >> >> > > + >> >> > > + if ((revision == 0x13) && irq_remapping_enabled) { >> >> > > + pr_warn(HW_ERR "This system BIOS has enabled interrupt remapping\n" >> >> > > + "on a chipset that contains an errata making that\n" >> >> > > + "feature unstable. Please reboot with nointremap\n" >> >> > > + "added to the kernel command line and contact\n" >> >> > > + "your BIOS vendor for an update"); >> >> >> >> This should be WARN_TAINT(TAINT_FIRMWARE_WORKAROUND). And 'an erratum'. >> >> >> > Ok, copy that. I'll repost shortly >> >> When you do, please include URLs for any problem reports or bugzillas you have. >> > Well, those are going to be vendor specific, so I'm not sure we can really do > that, at least not in any meaningful way. Sorry, I don't understand your point. It's useful to know who reported it (e.g., for future testers) and what happened and what bugzillas it solved. Of course it applies only to machines with this chipset and certain BIOS revisions. >> I assume Windows "just works" in this situation? > No more or less than linux does in this case. The Intel provided errata > indicates that the only acceptable workaround is to disable remapping in the > BIOS, so I would presume that if a windows system has a BIOS that doesn't > implement this fix, its just as exposed as we are. It sounds like the effect of this bug is that on Linux, devices may not work at all because of lost interrupts. Either Windows must never enable remapping (so it never sees the bug), or it must be designed in a way that tolerates the problem. I can't believe these machines shipped with Windows certification if devices didn't work correctly. Either way, I don't understand why we can't make the quirk just fix this. Booting with "nointremap" only sets disable_irq_remap, which is only used by irq_remapping_supported(). Early quirks are run before irq_remapping_supported () is ever called, so an early quirk ought to be just as effective as the command line option. Here's the relevant call tree I see: start_kernel setup_arch parse_early_param early_quirks rest_init ... The x86 setup_arch() does call generic_apic_probe(), but as far as I can tell, none of the APIC .probe() methods reference disable_irq_remap, so that doesn't look like a problem. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/