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

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Message-ID: <20170420121142.GI5077@suse.de>
Date:   Thu, 20 Apr 2017 14:11:42 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Daniel Drake <drake@...lessm.com>,
        Alexander Deucher <Alexander.Deucher@....com>,
        Samuel Sieb <samuel@...b.net>,
        David Woodhouse <dwmw2@...radead.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>
Subject: Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs

On Sat, Apr 08, 2017 at 09:41:07AM +0200, Lukas Wunner wrote:
> On Fri, Apr 07, 2017 at 04:32:18PM +0200, Joerg Roedel wrote:
> > From: Joerg Roedel <jroedel@...e.de>
> > 
> > ATS is broken on this hardware and causes IOMMU stalls and
> > system failure. Disable ATS on these devices to make them
> > usable again with IOMMU enabled.
> 
> AMD Stoney Ridge is an x86 CPU + GPU combo and this quirk pertains
> to the GPU, right?
> 
> In that case the quirk should go to arch/x86.  Paul Menzel (+cc)
> has just complained on linux-pci@ that final fixups are taking half
> a second, and I think that could be reduced if more efforts were
> spent to move arch-specific quirks out of the catch-all in
> drivers/pci/quirks.c.

The affected hardware here might be x86-only, but ATS is not. If a
broken ATS-capable plug-in card appears, we need this in generic code
anyway.

Also has anyone profiled why the fixups take so long (and on what
hardware)? Maybe the fixup-device matching can be improved instead of
cluttering arch-code with pci-fixups.


	Joerg