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

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Date:   Tue, 28 Mar 2017 21:13:23 +0000
From:   "Deucher, Alexander" <Alexander.Deucher@....com>
To:     'Joerg Roedel' <jroedel@...e.de>
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

> -----Original Message-----
> From: 'Joerg Roedel' [mailto:jroedel@...e.de]
> Sent: Tuesday, March 28, 2017 4:56 PM
> To: Deucher, Alexander
> Cc: 'Joerg Roedel'; Bjorn Helgaas; linux-pci@...r.kernel.org; linux-
> kernel@...r.kernel.org; Daniel Drake; Nath, Arindam
> Subject: Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS
> 
> On Tue, Mar 28, 2017 at 08:37:01PM +0000, Deucher, Alexander wrote:
> > The question is, could the problem stem from flushing an entity that
> > didn't request it, or should that not matter?  I guess it shouldn't
> > matter otherwise we'd see this on other platforms like Carrizo as
> > well.
> 
> What do you mean by "didn't request it"? The IOMMU driver only sends
> io/tlb invalidations to devices it enabled ATS on.

If I understand Arindam's patch correctly, it only flushes TLB entries for domains in the flush queue whereas the previous behavior was to flush all domains.  If there was no TLB flush in the queue for that domain, could flushing it cause a problem?  Sorry, I'm not too familiar with the IOMMU code or ATS.

Alex