linux-kernel - Re: IOMMU+DMAR causing NMIs-s

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Message-ID: <20160714083106.GQ12639@8bytes.org>
Date:	Thu, 14 Jul 2016 10:31:06 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	Meelis Roos <mroos@...ux.ee>,
	Linda Knippers <linda.knippers@....com>,
	David Woodhouse <dwmw2@...radead.org>,
	iommu@...ts.linux-foundation.org,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: IOMMU+DMAR causing NMIs-s

On Wed, Jul 13, 2016 at 05:04:08PM -0600, Alex Williamson wrote:
> 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,

That commit fixed a hang while the IOMMU is being initialized. This hang
is different, as the IOMMU already runs. So I doubt that it fixes this
problem, but it is worth a test, of course.


	Joerg