Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755243Ab3GIXni (ORCPT ); Tue, 9 Jul 2013 19:43:38 -0400 Received: from mail-pa0-f41.google.com ([209.85.220.41]:32791 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754110Ab3GIXne (ORCPT ); Tue, 9 Jul 2013 19:43:34 -0400 Date: Tue, 9 Jul 2013 16:43:31 -0700 From: Guenter Roeck To: Chris Wright Cc: Bjorn Helgaas , David Woodhouse , "linux-kernel@vger.kernel.org" , "open list:INTEL IOMMU (VT-d)" Subject: Re: WARNING: at drivers/iommu/dmar.c:484 warn_invalid_dmar with Intel Motherboard Message-ID: <20130709234331.GA10833@roeck-us.net> References: <20130709202406.GA11867@roeck-us.net> <20130709223106.GA16429@roeck-us.net> <20130709232252.GB2676@sequoia2.sous-sol.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130709232252.GB2676@sequoia2.sous-sol.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 36 On Tue, Jul 09, 2013 at 04:22:52PM -0700, Chris Wright wrote: > * Guenter Roeck (linux@roeck-us.net) wrote: > > On Tue, Jul 09, 2013 at 03:05:39PM -0600, Bjorn Helgaas wrote: > > > [+cc Joerg, David, iommu list] > > > > > > On Tue, Jul 9, 2013 at 2:24 PM, Guenter Roeck wrote: > > > > I started seeing this problem after updating the BIOS trying fix another issue, > > > > though I may have missed it earlier. > > > > > > > > I understand this is a BIOS bug. Would be great if someone can pass this on > > > > to Intel BIOS engineers. > > > > > > Maybe. It'd be nice if Linux handled it better, though. > > > > > If anyone has an idea how to do that, I'll be happy to write a patch. > > I'm not sure there's much you can do. The BIOS is saying there's a DMAR > unit, and then saying the registers are at addr 0x0. The kernel is > simply warning you about the invalid DMAR table entry. > > One thing I've seen is the BIOS zeroing the base register address when > VT-d is disabled in BIOS. So, Guenter, a "fix" may be simply enabling > VT-d in the BIOS. > Ah, yes, I think I may have that disabled. I'll check it tonight. Does that really warrant a traceback, or would a warning message be more appropriate (possibly telling the user to enable VT-d) ? Thanks, Guenter -- 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/