linux-kernel - Re: [ 102/127] iommu/amd: Workaround for ERBT1312

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Message-ID: <20130628182946.GU11309@8bytes.org>
Date:	Fri, 28 Jun 2013 20:29:46 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	Andreas Hartmann <andihartmann@...19freenet.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [ 102/127] iommu/amd: Workaround for ERBT1312

Hi Alex,

On Fri, Jun 28, 2013 at 11:49:04AM -0600, Alex Williamson wrote:
> That's interesting, I PXE boot my system from one NIC then use a
> different NIC for the iSCSI root.  The PXE boot NIC now screams like
> this, _until_ I attach it to vfio, then it quiets down.

Can you please send an example line of the reported fault? The addresses
it faults on would be interesting.

> > Any idea?
> 
> Not really without some digging.  I wonder if it's a new event each time
> or if something is just not clearing a previous event.  ISTR that a boot
> used to often, but not always, generate a couple faults between the
> IOMMU being enabled and the NIC driver being loaded.  All the faults I
> see are to the same address, so my guess is that it's getting replayed.

Well, I think it is a problem uncovered by the patch that re-enables the
event-log interrupt after it happened once. We need to find a strategy
to cope with those problems.

To my mind as a quick-fix comes rate-limiting for the printks. Or we use
the suppress-pf bit in the DTE to suppress all page-faults after the
first one.


	Joerg


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