linux-kernel - Re: IOMMU+DMAR causing NMIs-s (was: 4.7-rc6: NMI in intel

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Message-ID: <20160713090332.GK12639@8bytes.org>
Date:	Wed, 13 Jul 2016 11:03:32 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Meelis Roos <mroos@...ux.ee>
Cc:	iommu@...ts.linux-foundation.org,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: IOMMU+DMAR causing NMIs-s (was: 4.7-rc6: NMI in intel_idle on HP
 Proliant G6)

On Wed, Jul 13, 2016 at 11:31:02AM +0300, Meelis Roos wrote:
> > > Bisecting kernel configs shows that it's DMAR+IOMMU. When it is 
> > > activated, there is high probability of NMI-s in random places.
> > 
> > Hmm, strange. But nothing could really surprise when you have an HP
> > BIOS.
> 
> BIOS P64 01/22/2015. There seems to be a newer 2015.08.16 BIOS out but 
> the release notes only describe updated CPU microcode for security 
> reasons.

It is probably something HP is selling as a "feature" and not a BIOS
bug.

> > Can you probably use the faulty config and bisect this down to a
> > specific commit? In v4.7-rc1 some changes to the iova-allocation code
> > got merged, but I have no idea how those could cause NMIs.
> 
> Will try but I do not know a working base yet - this was broken in both 
> 4.6 and 4.7-rc.

Oh, in that case it is not related to the recent iova changes. Does the
box have any hardware error log which you can access and send to us
(right after some NMIs happened)?


Thanks,

	Joerg