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* [for-CI 1/3] drm: Restore double clflush on the last partial cacheline
@ 2016-05-06 14:40 Chris Wilson
  2016-05-06 14:40 ` [for-CI 2/3] drm/i915/execlists: Refactor common engine setup Chris Wilson
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Chris Wilson @ 2016-05-06 14:40 UTC (permalink / raw)
  To: intel-gfx

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>
Cc: stable@vger.kernel.org
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
---
 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 6743ff7dccfa..7f4a6c550319 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;
 	}
-- 
2.8.1

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^ permalink raw reply related	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2016-05-09 12:50 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-05-06 14:40 [for-CI 1/3] drm: Restore double clflush on the last partial cacheline Chris Wilson
2016-05-06 14:40 ` [for-CI 2/3] drm/i915/execlists: Refactor common engine setup Chris Wilson
2016-05-06 14:40 ` [for-CI 3/3] drm/i915: Store a i915 backpointer from engine, and use it Chris Wilson
2016-05-09 12:23 ` ✗ Fi.CI.BAT: warning for series starting with [for-CI,1/3] drm: Restore double clflush on the last partial cacheline Patchwork
2016-05-09 12:50   ` Chris Wilson

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