linux-kernel - Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS

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Date:   Tue, 28 Mar 2017 22:28:44 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>
Cc:     'Joerg Roedel' <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Daniel Drake <drake@...lessm.com>,
        "Nath, Arindam" <Arindam.Nath@....com>
Subject: Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS

On Tue, Mar 28, 2017 at 08:18:26PM +0000, Deucher, Alexander wrote:
> > -----Original Message-----
> > From: Joerg Roedel [mailto:joro@...tes.org]
> > Sent: Tuesday, March 28, 2017 8:17 AM
> > To: Bjorn Helgaas
> > Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; Joerg Roedel;
> > Daniel Drake; Deucher, Alexander
> > Subject: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS
> > 
> > From: Joerg Roedel <jroedel@...e.de>
> > 
> > ATS is broken on these devices. Under invalidation load, the
> > GPU does not reply to invalidations anymore, causing
> > Completion-wait loop timeouts on the AMD IOMMU driver side.
> > Fix it by not enabling ATS on these devices.
> > 
> > Note that below mentioned commit is not broken, it just
> > triggers the issue because it might cause invalidation
> > storms on devices.
> > 
> > Fixes: b1516a14657a ('iommu/amd: Implement flush queue')
> > Reported-by: Daniel Drake <drake@...lessm.com>
> > Cc: Daniel Drake <drake@...lessm.com>
> > Cc: Alexander Deucher <Alexander.Deucher@....com>
> > Signed-off-by: Joerg Roedel <jroedel@...e.de>
> 
> Did you see Arindam's patch from yesterday[1]?  Not sure which is the proper fix, maybe both?

Arindam's patch makes sense on its own, but not as a fix for this issue.
It lowers the invalidation load on the GPU, but there are still ways to
trigger a high invalidation rate on the device. So it might hide the
issue, but not fix it.

We need to disable ATS on the device if it doesn't work reliably.



	Joerg