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

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Date:   Thu, 04 May 2017 12:21:37 +0200
From:   David Woodhouse <dwmw2@...radead.org>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        'Joerg Roedel' <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     "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>,
        Samuel Sieb <samuel@...b.net>, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs

On Fri, 2017-04-07 at 16:46 +0000, Deucher, Alexander wrote:
> > 
> > -----Original Message-----
> > From: Joerg Roedel [mailto:joro@...tes.org]
> > Sent: Friday, April 07, 2017 10:32 AM
> > To: Bjorn Helgaas
> > Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; Daniel Drake;
> > Deucher, Alexander; Samuel Sieb; David Woodhouse; Joerg Roedel
> > Subject: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs
> > 
> > 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.
> > 
> > Note that the commit in the Fixes-tag is not buggy, it
> > just uncovers the problem in the hardware by increasing
> > the ATS-flush rate.
> > 
> > Fixes: b1516a14657a ('iommu/amd: Implement flush queue')
> > Signed-off-by: Joerg Roedel <jroedel@...e.de>
> Acked-by: Alex Deucher <alexander.deucher@....com>

Alex, are you able to confirm that it is *only* the device with PCI ID
0x98e4 which has this problem, or (more likely) come up with an
exhaustive list? Thanks.

We'll want the same blacklist in Xen too, won't we?

> > 
> > ---
> >  drivers/pci/quirks.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 6736836..7cbe316 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4634,3 +4634,22 @@ static void quirk_no_aersid(struct pci_dev *pdev)
> >  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2031,
> > quirk_no_aersid);
> >  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2032,
> > quirk_no_aersid);
> >  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2033,
> > quirk_no_aersid);
> > +
> > +#ifdef CONFIG_PCI_ATS
> > +/*
> > + * Some devices have a broken ATS implementation causing IOMMU stalls.
> > + * Don't use ATS for those devices.
> > + */
> > +static void quirk_disable_ats(struct pci_dev *pdev)
> > +{
> > +	/*
> > +	 * Set pdev->ats_cap = 0 to make pci_enable_ats() bail out
> > +	 * early.
> > +	 */
> > +	dev_info(&pdev->dev, "QUIRK: Disabling ATS");
> > +	pdev->ats_cap = 0;
> > +}
> > +
> > +/* AMD Stoney platform GPU */
> > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x98e4, quirk_disable_ats);
> > +#endif /* CONFIG_PCI_ATS */
> > --
> > 1.9.1
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