Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs

From	Joerg Roedel <jroedel@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs
Date	2017-07-11 14:00 +0200
Message-ID	<u21ZE-1NQ-13@gated-at.bofh.it> (permalink)
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Hi Bjorn,

On Mon, Jul 10, 2017 at 11:53:58AM -0500, Bjorn Helgaas wrote:
> I'm still confused.  Per Samuel
> (6dd9dbac-9b65-bc7c-bb08-413a05d09fc8@sieb.net):
> 
> Samuel> The other patch seems to fix this issue without disabling ATS.
> Samuel> Isn't that better?
> 
> and Alex
> (BN6PR12MB1652DF4130FC792B71DD9974F7C00@BN6PR12MB1652.namprd12.prod.outlook.com):
> 
> Alex> I talked to our validation team and ATS was validated on Stoney,
> Alex> so this patch is just working around something else.  The other
> Alex> patch fixes it and is a valid optimization ...
> 
> I'm confused about what this "other patch" is and whether we want that
> one, this one, or both.

The other patches floating around lowered the ATS flush-rate from the
AMD IOMMU driver, which makes the issue disappear as well. But the issue
only disappeared, it is not solved and could probably still be
reproduced with a GPU usage pattern that increases the ATS flush-rate.

So blacklisting the device for ATS is still the safest thing we could do
here.

Regards,

	Joerg

Thread

Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs Bjorn Helgaas <helgaas@kernel.org> - 2017-07-10 19:00 +0200
  Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs Joerg Roedel <jroedel@suse.de> - 2017-07-11 14:00 +0200
    RE: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs "Deucher, Alexander" <Alexander.Deucher@amd.com> - 2017-07-11 21:10 +0200

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