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The optimisation inherent in commit6a2c4232ec("drm/i915: Make the physical object coherent with GTT") relies on that once we allocated a cursor we would have coherent, zero overhead access to the scanout plane holding the cursor. That is we could then do the very frequent cursor updates X enjoys with no indirection or kernel involvement. However, that all hinges on the GGTT mmap of the cursor being pinned and not require refaulting on each access -- handling such a page fault likely requires the busy GGTT to be rearranged causing a stall. A very simple fix is then to handle the physical cursor exactly like other cursors and keep its vma pinned while active. References: https://bugs.freedesktop.org/show_bug.cgi?id=107600 References:6a2c4232ec("drm/i915: Make the physical object coherent with GTT") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180817082405.755-1-chris@chris-wilson.co.uk
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.