<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [BSW/BXT-P] igt /gem_pwrite / small-gtt* subcases are failing" href="https://bugs.freedesktop.org/show_bug.cgi?id=96563#c10">Comment # 10</a> on <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [BSW/BXT-P] igt /gem_pwrite / small-gtt* subcases are failing" href="https://bugs.freedesktop.org/show_bug.cgi?id=96563">bug 96563</a> from <a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> Chris Wilson</a> <pre>Also requires: commit e22d8e3c69a9f432b40baaaf3f894a128fdc2222 Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> Date: Wed Apr 12 12:01:11 2017 +0100 drm/i915: Treat WC a separate cache domain When discussing a new WC mmap, we based the interface upon the assumption that GTT was fully coherent. How naive! Commits 3b5724d702ef ("drm/i915: Wait for writes through the GTT to land before reading back") and ed4596ea992d ("drm/i915/guc: WA to address the Ringbuffer coherency issue") demonstrate that writes through the GTT are indeed delayed and may be overtaken by direct WC access. To be safe, if userspace is mixing WC mmaps with other potential GTT access (pwrite, GTT mmaps) it should use set_domain(WC). Bugzilla: <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [BSW/BXT-P] igt /gem_pwrite / small-gtt* subcases are failing" href="show_bug.cgi?id=96563">https://bugs.freedesktop.org/show_bug.cgi?id=96563</a> Testcase: igt/gem_pwrite/small-gtt* Testcase: igt/drv_selftest/coherency Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> Reviewed-by: Joonas Lahtinen <<a href="mailto:joonas.lahtinen@linux.intel.com">joonas.lahtinen@linux.intel.com</a>> Link: <a href="http://patchwork.freedesktop.org/patch/msgid/20170412110111.26626-2-chris@chris-wilson.co.uk">http://patchwork.freedesktop.org/patch/msgid/20170412110111.26626-2-chris@chris-wilson.co.uk</a></pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>