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

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Date:	Thu, 11 Jul 2013 13:59:02 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:INTEL IOMMU (VT-d)" <iommu@...ts.linux-foundation.org>
Subject: Re: WARNING: at drivers/iommu/dmar.c:484 warn_invalid_dmar with
 Intel Motherboard

On Thu, Jul 11, 2013 at 12:00:54PM -0700, Chris Wright wrote:
> * Guenter Roeck (linux@...ck-us.net) wrote:
> > On Tue, Jul 09, 2013 at 04:22:52PM -0700, Chris Wright wrote:
> > > 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.
> 
> Did you find out if BIOS change fixed this?
> 
No, it didn't. Enabling or disabling virtualization in the BIOS did not make
a difference. It looks like there is a bad DMAR table entry (with address 0)
in the ACPI data. In case you are interested how it looks like:

DMAR @ 0xcb3f3f90
  0000: 44 4d 41 52 90 00 00 00 01 d5 49 4e 54 45 4c 20  DMAR......INTEL
  0010: 44 48 38 37 52 4c 20 20 40 01 00 00 49 4e 54 4c  DH87RL  @...INTL
  0020: 01 00 00 00 26 00 00 00 00 00 00 00 00 00 00 00  ....&...........
  0030: 00 00 10 00 01 00 00 00 00 00 00 00 00 00 00 00  ................
  0040: 01 00 30 00 00 00 00 00 00 b0 eb cb 00 00 00 00  ..0.............
  0050: ff 9f ec cb 00 00 00 00 01 08 00 00 00 00 1d 00  ................
  0060: 01 08 00 00 00 00 1a 00 01 08 00 00 00 00 14 00  ................
  0070: 01 00 20 00 00 00 00 00 00 00 00 d7 00 00 00 00  .. .............
  0080: ff ff 1f df 00 00 00 00 01 08 00 00 00 00 02 00  ................

Turns out the i7-4770K doesn't support VT-d, so my current understanding
is that there should be no DMAR table in the first place.

Guenter
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