From 396f5d62d1a5fd99421855a08ffdef8edb43c76e Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 7 Jul 2016 09:41:12 +0100 Subject: [PATCH] drm: Restore double clflush on the last partial cacheline This effectively reverts commit afcd950cafea6e27b739fe7772cbbeed37d05b8b Author: Chris Wilson 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 Cc: dri-devel@lists.freedesktop.org Cc: Akash Goel Cc: Imre Deak Cc: Daniel Vetter Cc: Jason Ekstrand Cc: stable@vger.kernel.org Reviewed-by: Mika Kuoppala Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1467880930-23082-6-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/drm_cache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c index 059f7c39c582..a7916e5f8864 100644 --- a/drivers/gpu/drm/drm_cache.c +++ b/drivers/gpu/drm/drm_cache.c @@ -136,6 +136,7 @@ drm_clflush_virt_range(void *addr, unsigned long length) mb(); for (; addr < end; addr += size) clflushopt(addr); + clflushopt(end - 1); /* force serialisation */ mb(); return; } -- 2.20.1