This is a note to let you know that I've just added the patch titled
drm: Restore double clflush on the last partial cacheline
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-restore-double-clflush-on-the-last-partial-cacheline.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 396f5d62d1a5fd99421855a08ffdef8edb43c76e Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Thu, 7 Jul 2016 09:41:12 +0100
Subject: drm: Restore double clflush on the last partial cacheline
From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
commit 396f5d62d1a5fd99421855a08ffdef8edb43c76e upstream.
This effectively reverts
commit afcd950cafea6e27b739fe7772cbbeed37d05b8b
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Akash Goel <akash.goel@xxxxxxxxx>
Cc: Imre Deak <imre.deak@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Jason Ekstrand <jason.ekstrand@xxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/1467880930-23082-6-git-send-email-chris@xxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
}
Patches currently in stable-queue which might be from chris@xxxxxxxxxxxxxxxxxx are
queue-4.4/drm-restore-double-clflush-on-the-last-partial-cacheline.patch
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