linux-kernel - next-20130709 DMAR issues

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Date:	Wed, 10 Jul 2013 13:01:42 -0400
From:	Valdis Kletnieks <Valdis.Kletnieks@...edu>
To:	David Woodhouse <dwmw2@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: next-20130709 DMAR issues

Dell Latitude E6530.

Seeing a new error message crop up in next-0709 that wasn't there with 0703.
Particularly odd, last person to touch dmar.c was on 05/20/2013, so no smoking
guns there...

egrep -i 'dmar|linux ver' /var/log/messages  gives me:

Jul  9 21:47:15 turing-police kernel: [    0.000000] Linux version 3.10.0-next-20130703 (valdis@...ing-police.cc.vt.edu) (gcc version 4.8.1 20130612 (Red Hat 4.8.1-2) (GCC) ) #99 SMP PREEMPT Wed Jul 3 17:40:09 EDT 2013
Jul  9 21:47:15 turing-police kernel: [    0.000000] ACPI: DMAR 00000000cb7fd298 00080 (v01 INTEL      SNB  00000001 INTL 00000001)
Jul  9 21:47:15 turing-police kernel: [    0.021530] dmar: Host address width 36
Jul  9 21:47:15 turing-police kernel: [    0.021536] dmar: DRHD base: 0x000000fed90000 flags: 0x1
Jul  9 21:47:15 turing-police kernel: [    0.021569] dmar: IOMMU 0: reg_base_addr fed90000 ver 1:0 cap c9008020660262 ecap f0105a
Jul  9 21:47:15 turing-police kernel: [    0.021576] dmar: RMRR base: 0x000000ce761000 end: 0x000000ce780fff
Jul  9 21:47:15 turing-police kernel: [    1.023235] DMAR: No ATSR found

That's what it usually says.  But now I have:

Jul 10 12:20:19 turing-police kernel: [    0.000000] Linux version 3.10.0-next-20130709 (valdis@...ing-police.cc.vt.edu) (gcc version 4.8.1 20130612 (Red Hat 4.8.1-2) (GCC) ) #100 SMP PREEMPT Tue Jul 9 16:01:59 EDT 2013
Jul 10 12:20:19 turing-police kernel: [    0.000000] ACPI: DMAR 00000000cb7fd298 00080 (v01 INTEL      SNB  00000001 INTL 00000001)
Jul 10 12:20:19 turing-police kernel: [    0.021453] dmar: Host address width 36
Jul 10 12:20:19 turing-police kernel: [    0.021456] dmar: DRHD base: 0x000000fed90000 flags: 0x1
Jul 10 12:20:19 turing-police kernel: [    0.021485] dmar: IOMMU 0: reg_base_addr fed90000 ver 1:0 cap c9008020660262 ecap f0105a
Jul 10 12:20:19 turing-police kernel: [    0.021487] dmar: RMRR base: 0x000000ce761000 end: 0x000000ce780fff
Jul 10 12:20:19 turing-police kernel: [    0.021575] dmar: DRHD: handling fault status reg 2
Jul 10 12:20:19 turing-police kernel: [    0.021583] dmar: DMAR:[DMA Read] Request device [00:1f.2] fault addr ce71d000
Jul 10 12:20:19 turing-police kernel: [    0.021583] DMAR:[fault reason 06] PTE Read access is not set
Jul 10 12:20:19 turing-police kernel: [    1.034643] DMAR: No ATSR found

Now I have 3 extra messages talking about handling a fault status.  lspci says 00:1f.2 is:

00:1f.2 SATA controller: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04)

I found similar in a thread here: http://lkml.indiana.edu/hypermail/linux/kernel/1212.1/02319.html
which ended with Don Dutile saying:

"DMAR table does not have an entry for this device to this region.
Once the driver reconfigs/resets the device to stop polling bios-boot
cmd rings and use (new) OS (dma-mapped) rings, there's a period of time
during this transition that the hw is babbling away to an area that is no
longer mapped."

But I'm not convinced this is the same issue - why did it change between 0703 and 0709,
when I haven't updated the firmware. No relevant .config changes between the two, either.

If this doesn't ring any bells, I'l go do the bisect thing...

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