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

[Joerg Roedel <joro@8bytes.org>]

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