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    SubjectRE: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS
    Date
    > -----Original Message-----
    > From: 'Joerg Roedel' [mailto:jroedel@suse.de]
    > Sent: Tuesday, March 28, 2017 6:26 PM
    > To: Deucher, Alexander
    > Cc: 'Joerg Roedel'; Bjorn Helgaas; linux-pci@vger.kernel.org; linux-
    > kernel@vger.kernel.org; Daniel Drake; Nath, Arindam
    > Subject: Re: [PATCH] PCI: Blacklist AMD Stoney GPU devices for ATS
    >
    > On Tue, Mar 28, 2017 at 09:13:23PM +0000, Deucher, Alexander wrote:
    > > 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?
    >
    > No, that can't cause a problem. An io/tlb flush for the device is just a
    > message that the device should invalidate its own tlb. The device can't
    > know and doesn't need to know whether the page-tables it used to fill
    > the tlb really changed.
    >
    > As it looks, the problem we are seeing here is that we are sending a
    > large amount of these requests to the GPU device, and wait for its
    > completion every time. This shouldn't be a problem for ATS devices, but
    > the GPU here seems to fail at some point and doesn't answer to the
    > invalidation request anymore, causing the completion-wait loop timeouts.
    >
    > Arindam's patch makes the high flush-frequency less likely, but it can
    > still happen, depending on how the GPU is used. So its the best to
    > keep ATS disabled on the device as it doesn't work correctly and we risk
    > running in the same problem again when we leave it enabled and just make
    > the trigger less likely.

    Thanks for clarifying. The patch is:
    Acked-by: Alex Deucher <alexander.deucher@amd.com>

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