linux-kernel - Re: WARNING: at drivers/iommu/dmar.c:484 warn_invalid

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Date:	Wed, 14 Aug 2013 11:36:12 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:INTEL IOMMU (VT-d)" <iommu@...ts.linux-foundation.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: WARNING: at drivers/iommu/dmar.c:484 warn_invalid_dmar with
 Intel Motherboard

On Tue, Jul 09, 2013 at 03:31:06PM -0700, Guenter Roeck 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 <linux@...ck-us.net> 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 doubt that we can do anything meaningful here. The BIOS is broken in a
way so that we can't use the IOMMU in Linux. We can patch away the
WARN_ON and make it a sumple FW_BUG message, but the noise a WARN_ON
makes maybe help getting this issue fixed.

But I may be convinced otherwise, if people think this WARN_ON is not
worth it.


	Joerg


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