[Bug 96584] [regression] [i915] DMAR Errors Spamming Logs

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96584

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #19 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit 48f112fed3b07858f1b3a78548d23320fb96747b
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Fri Jun 24 14:07:14 2016 +0100

    drm/i915: Fill unused GGTT with scratch pages for VT-d

    One of the numerous VT-d workarounds we require is that the display
    hardware reads past the end of the buffer triggering VT-d faults. This
    is acknowledged in the code as being safe "since we fill the unused
    portions of the GGTT with the scratch page". Alas, that is no longer
    always true and so we trigger DMAR read faults.

    Skylake also requires another workaround to avoid mixing VT-d and
    unpopulated PTE, and so there we also need to ensure we fill unused
    entries with the scratch page.

    Reported-by: Mike Lothian <mike at fireburn.co.uk>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96584
    Fixes: f7770bfd9fd2 ("drm/i915: Skip clearing the GGTT on full-ppgtt
systems")
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: David Weinehall <david.weinehall at intel.com>
    Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
    Link:
http://patchwork.freedesktop.org/patch/msgid/1466773634-8106-1-git-send-email-chris@chris-wilson.co.uk
    Reviewed-by: David Weinehall <david.weinehall at intel.com>

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