| From 396f5d62d1a5fd99421855a08ffdef8edb43c76e Mon Sep 17 00:00:00 2001 |
| From: Chris Wilson <chris@chris-wilson.co.uk> |
| Date: Thu, 7 Jul 2016 09:41:12 +0100 |
| Subject: drm: Restore double clflush on the last partial cacheline |
| |
| From: Chris Wilson <chris@chris-wilson.co.uk> |
| |
| commit 396f5d62d1a5fd99421855a08ffdef8edb43c76e upstream. |
| |
| This effectively reverts |
| |
| commit afcd950cafea6e27b739fe7772cbbeed37d05b8b |
| Author: Chris Wilson <chris@chris-wilson.co.uk> |
| Date: Wed Jun 10 15:58:01 2015 +0100 |
| |
| drm: Avoid the double clflush on the last cache line in drm_clflush_virt_range() |
| |
| as we have observed issues with serialisation of the clflush operations |
| on Baytrail+ Atoms with partial updates. Applying the double flush on the |
| last cacheline forces that clflush to be ordered with respect to the |
| previous clflush, and the mfence then protects against prefetches crossing |
| the clflush boundary. |
| |
| The same issue can be demonstrated in userspace with igt/gem_exec_flush. |
| |
| Fixes: afcd950cafea6 (drm: Avoid the double clflush on the last cache...) |
| Testcase: igt/gem_concurrent_blit |
| Testcase: igt/gem_partial_pread_pwrite |
| Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92845 |
| Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> |
| Cc: dri-devel@lists.freedesktop.org |
| Cc: Akash Goel <akash.goel@intel.com> |
| Cc: Imre Deak <imre.deak@intel.com> |
| Cc: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Cc: Jason Ekstrand <jason.ekstrand@intel.com> |
| Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Link: http://patchwork.freedesktop.org/patch/msgid/1467880930-23082-6-git-send-email-chris@chris-wilson.co.uk |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/gpu/drm/drm_cache.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/drivers/gpu/drm/drm_cache.c |
| +++ b/drivers/gpu/drm/drm_cache.c |
| @@ -136,6 +136,7 @@ drm_clflush_virt_range(void *addr, unsig |
| mb(); |
| for (; addr < end; addr += size) |
| clflushopt(addr); |
| + clflushopt(end - 1); /* force serialisation */ |
| mb(); |
| return; |
| } |
