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SubjectRe: IOMMU+DMAR causing NMIs-s
On Thu, 14 Jul 2016 00:52:02 +0300 (EEST)
Meelis Roos <> wrote:

> > >> Thanks. So device 00:1e.0 is a PCI-bridge which has some 32-bit
> > >> PCI-devices behind it. One of these devices tries to read address
> > >> 0xb000, which is blocked by the IOMMU and causes the fault seen in the
> > >> screen-shot. The fault also causes a PCI-error which is then reported
> > >> through the NMI, causing your kernel panic.
> > >>
> > >> So the 32bit PCI devices behind the bridge are:
> > >>
> > >> 01:03.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] ES1000 (rev 02) (prog-if 00 [VGA controller])
> > >> 01:04.0 System peripheral: Compaq Computer Corporation Integrated Lights Out Controller (rev 03)
> > >> 01:04.2 System peripheral: Compaq Computer Corporation Integrated Lights Out Processor (rev 03)
> > >> 01:04.4 USB controller: Hewlett-Packard Company Integrated Lights-Out Standard Virtual USB Controller (prog-if 00 [UHCI])
> > >> 01:04.6 IPMI SMIC interface: Hewlett-Packard Company Integrated Lights-Out Standard KCS Interface (prog-if 01)
> > >>
> > >> Can you try to disable this 'Lights Out' processor? Maybe it is causing
> > >> the issues. On the other side, the radeon driver for the ATI card is
> > >> also know for causing faults from time to time. Can you capture the
> > >> kernel messages right before a crash too?
> > >
> > > IIRC, blacklisting the hpwdt module can defuse those NMIs and might
> > > help us see more of the actual DMAR faults. Blacklist in modprobe.d
> > > and rebuild initrd. Thanks,
> > >
> > > Alex
> > >
> > > PS - never assume BIOS release notes are actually complete
> >
> > I agree. I'd do the BIOS update and also make sure the iLO FW is current.
> OK, updates to the latest BIOS, CPU microcode revison is now 0x1b
> instead of 0x19. ILO2 fw is already the latest.
> The NMI-s still happen.
> Disabled hpwdt. Now most boots are fine, only one hung with radeon
> loading:
> Vusal patterns also remind me that all the previous hangs were before
> radeon mode change - once radeon changes the mode, it already works.

There might be multiple things going on here, I tend to associate the
NMIs with the DMAR faults on HP systems and I expect that disabling
hpwdt will remove that DMAR fault to NMI escalation, but it won't fix
the fact that DMAR faults are occurring. I'm not sure how any of that
is related to radeon though other than the fact that the radeon device
is behind the bridge that generated the DMAR fault and since we can't
tell which device behind the bridge generated that transaction, it's
possible that it was the radeon card (though we're all more likely to
throw stones at the iLO first).

With hpwdt disabled, can you reboot a few times and look for DMAR
faults in the dmesg to see if they're all consistent, ie. device 1e.0
doing a read from 0xb000? Is there any correlation to radeon hanging
and one of those DMAR faults appearing in the log (you can make use of
the iLO for a serial console so you can record more of the boot than
what can be captured on the VGA console). Also, this should be an
X58-based system, which reminds me of Joerg's recent commit
a4c34ff1c029 that's intended to fix a hang on such systems. That was
included starting in v4.7-rc4, so if this is a new issue, testing
before and after that commit might be relevant. Thanks,


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