[PATCH] drm/i915/ringbuffer: Flush writes before RING_TAIL update

[PATCH] drm/i915/ringbuffer: Flush writes before RING_TAIL update

[Chris Wilson]

Be paranoid and make sure we flush any and all writes out of the WCB
before performing the UC mmio to update the RING_TAIL. (An UC write
should itself be enough to do the flush, hence the paranoia here.) Quite
infrequently, we see problems where the GPU seems to overshoot the
RING_TAIL and so executes garbage hence the speculation.

References: https://bugs.freedesktop.org/show_bug.cgi?id=111598
References: https://bugs.freedesktop.org/show_bug.cgi?id=111417
References: https://bugs.freedesktop.org/show_bug.cgi?id=111034
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index bbda85dcaa42..73c3ffc80218 100644
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -930,6 +930,7 @@ static void cancel_requests(struct intel_engine_cs *engine)
 static void i9xx_submit_request(struct i915_request *request)
 {
 	i915_request_submit(request);
+	wmb(); /* paranoid flush writes out of the WCB before mmio */
 
 	ENGINE_WRITE(request->engine, RING_TAIL,
 		     intel_ring_set_tail(request->ring, request->tail));
-- 
2.23.0

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

✓ Fi.CI.BAT: success for drm/i915/ringbuffer: Flush writes before RING_TAIL update

[Patchwork]

== Series Details ==

Series: drm/i915/ringbuffer: Flush writes before RING_TAIL update
URL   : https://patchwork.freedesktop.org/series/66426/
State : success

== Summary ==

CI Bug Log - changes from CI_DRM_6854 -> Patchwork_14327
====================================================

Summary
-------

  **SUCCESS**

  No regressions found.

  External URL: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/

Possible new issues
-------------------

  Here are the unknown changes that may have been introduced in Patchwork_14327:

### IGT changes ###

#### Suppressed ####

  The following results come from untrusted machines, tests, or statuses.
  They do not affect the overall result.

  * igt@gem_sync@basic-each:
    - {fi-tgl-u}:         NOTRUN -> [INCOMPLETE][1]
   [1]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/fi-tgl-u/igt@gem_sync@basic-each.html

  
Known issues
------------

  Here are the changes found in Patchwork_14327 that come from known issues:

### IGT changes ###

#### Issues hit ####

  * igt@i915_selftest@live_gem_contexts:
    - fi-skl-iommu:       [PASS][2] -> [INCOMPLETE][3] ([fdo#111519])
   [2]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/fi-skl-iommu/igt@i915_selftest@live_gem_contexts.html
   [3]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/fi-skl-iommu/igt@i915_selftest@live_gem_contexts.html

  
#### Possible fixes ####

  * igt@gem_ctx_switch@legacy-render:
    - fi-icl-u2:          [INCOMPLETE][4] ([fdo#107713] / [fdo#111381]) -> [PASS][5]
   [4]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/fi-icl-u2/igt@gem_ctx_switch@legacy-render.html
   [5]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/fi-icl-u2/igt@gem_ctx_switch@legacy-render.html

  * igt@gem_exec_gttfill@basic:
    - {fi-tgl-u}:         [INCOMPLETE][6] ([fdo#111593]) -> [PASS][7]
   [6]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/fi-tgl-u/igt@gem_exec_gttfill@basic.html
   [7]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/fi-tgl-u/igt@gem_exec_gttfill@basic.html

  
  {name}: This element is suppressed. This means it is ignored when computing
          the status of the difference (SUCCESS, WARNING, or FAILURE).

  [fdo#107713]: https://bugs.freedesktop.org/show_bug.cgi?id=107713
  [fdo#111381]: https://bugs.freedesktop.org/show_bug.cgi?id=111381
  [fdo#111519]: https://bugs.freedesktop.org/show_bug.cgi?id=111519
  [fdo#111593]: https://bugs.freedesktop.org/show_bug.cgi?id=111593


Participating hosts (51 -> 47)
------------------------------

  Additional (3): fi-icl-dsi fi-cfl-guc fi-icl-u3 
  Missing    (7): fi-ilk-m540 fi-hsw-4200u fi-byt-squawks fi-bsw-cyan fi-icl-y fi-byt-clapper fi-bdw-samus 


Build changes
-------------

  * CI: CI-20190529 -> None
  * Linux: CI_DRM_6854 -> Patchwork_14327

  CI-20190529: 20190529
  CI_DRM_6854: 5a70800ed2837e2d35a331e2cfd43a55df58c4fc @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_5176: 0102dcf4e2e8b357b59173fe1ff78069148080c6 @ git://anongit.freedesktop.org/xorg/app/intel-gpu-tools
  Patchwork_14327: cda3b809297cb7c5b44e6c9abe22cc4b7516a98d @ git://anongit.freedesktop.org/gfx-ci/linux


== Linux commits ==

cda3b809297c drm/i915/ringbuffer: Flush writes before RING_TAIL update

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

✓ Fi.CI.IGT: success for drm/i915/ringbuffer: Flush writes before RING_TAIL update

[Patchwork]

== Series Details ==

Series: drm/i915/ringbuffer: Flush writes before RING_TAIL update
URL   : https://patchwork.freedesktop.org/series/66426/
State : success

== Summary ==

CI Bug Log - changes from CI_DRM_6854_full -> Patchwork_14327_full
====================================================

Summary
-------

  **SUCCESS**

  No regressions found.

  

Known issues
------------

  Here are the changes found in Patchwork_14327_full that come from known issues:

### IGT changes ###

#### Issues hit ####

  * igt@gem_exec_schedule@preempt-other-chain-bsd:
    - shard-iclb:         [PASS][1] -> [SKIP][2] ([fdo#111325]) +5 similar issues
   [1]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb6/igt@gem_exec_schedule@preempt-other-chain-bsd.html
   [2]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb2/igt@gem_exec_schedule@preempt-other-chain-bsd.html

  * igt@gem_exec_schedule@preempt-queue-bsd1:
    - shard-iclb:         [PASS][3] -> [SKIP][4] ([fdo#109276]) +19 similar issues
   [3]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb1/igt@gem_exec_schedule@preempt-queue-bsd1.html
   [4]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb6/igt@gem_exec_schedule@preempt-queue-bsd1.html

  * igt@kms_cursor_crc@pipe-c-cursor-suspend:
    - shard-apl:          [PASS][5] -> [DMESG-WARN][6] ([fdo#108566])
   [5]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-apl1/igt@kms_cursor_crc@pipe-c-cursor-suspend.html
   [6]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-apl2/igt@kms_cursor_crc@pipe-c-cursor-suspend.html

  * igt@kms_cursor_legacy@2x-long-cursor-vs-flip-atomic:
    - shard-hsw:          [PASS][7] -> [FAIL][8] ([fdo#105767])
   [7]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-hsw4/igt@kms_cursor_legacy@2x-long-cursor-vs-flip-atomic.html
   [8]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-hsw6/igt@kms_cursor_legacy@2x-long-cursor-vs-flip-atomic.html

  * igt@kms_cursor_legacy@pipe-a-single-move:
    - shard-apl:          [PASS][9] -> [INCOMPLETE][10] ([fdo#103927]) +1 similar issue
   [9]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-apl2/igt@kms_cursor_legacy@pipe-a-single-move.html
   [10]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-apl3/igt@kms_cursor_legacy@pipe-a-single-move.html

  * igt@kms_frontbuffer_tracking@fbc-rgb565-draw-pwrite:
    - shard-iclb:         [PASS][11] -> [FAIL][12] ([fdo#103167]) +2 similar issues
   [11]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb7/igt@kms_frontbuffer_tracking@fbc-rgb565-draw-pwrite.html
   [12]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb4/igt@kms_frontbuffer_tracking@fbc-rgb565-draw-pwrite.html

  * igt@kms_plane@pixel-format-pipe-b-planes:
    - shard-hsw:          [PASS][13] -> [INCOMPLETE][14] ([fdo#103540])
   [13]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-hsw7/igt@kms_plane@pixel-format-pipe-b-planes.html
   [14]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-hsw7/igt@kms_plane@pixel-format-pipe-b-planes.html

  * igt@kms_plane_alpha_blend@pipe-c-coverage-7efc:
    - shard-skl:          [PASS][15] -> [FAIL][16] ([fdo#108145] / [fdo#110403])
   [15]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl3/igt@kms_plane_alpha_blend@pipe-c-coverage-7efc.html
   [16]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl2/igt@kms_plane_alpha_blend@pipe-c-coverage-7efc.html

  * igt@kms_psr2_su@frontbuffer:
    - shard-iclb:         [PASS][17] -> [SKIP][18] ([fdo#109642] / [fdo#111068])
   [17]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb2/igt@kms_psr2_su@frontbuffer.html
   [18]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb4/igt@kms_psr2_su@frontbuffer.html

  * igt@kms_psr@psr2_sprite_plane_move:
    - shard-iclb:         [PASS][19] -> [SKIP][20] ([fdo#109441]) +3 similar issues
   [19]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb2/igt@kms_psr@psr2_sprite_plane_move.html
   [20]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb7/igt@kms_psr@psr2_sprite_plane_move.html

  * igt@kms_rotation_crc@primary-rotation-270:
    - shard-skl:          [PASS][21] -> [DMESG-WARN][22] ([fdo#106107])
   [21]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl8/igt@kms_rotation_crc@primary-rotation-270.html
   [22]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl10/igt@kms_rotation_crc@primary-rotation-270.html

  
#### Possible fixes ####

  * igt@gem_ctx_shared@exec-single-timeline-bsd:
    - shard-iclb:         [SKIP][23] ([fdo#110841]) -> [PASS][24]
   [23]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb2/igt@gem_ctx_shared@exec-single-timeline-bsd.html
   [24]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb3/igt@gem_ctx_shared@exec-single-timeline-bsd.html

  * igt@gem_exec_async@concurrent-writes-bsd:
    - shard-iclb:         [SKIP][25] ([fdo#111325]) -> [PASS][26] +4 similar issues
   [25]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb4/igt@gem_exec_async@concurrent-writes-bsd.html
   [26]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb7/igt@gem_exec_async@concurrent-writes-bsd.html

  * igt@gem_fence_thrash@bo-write-verify-threaded-x:
    - shard-apl:          [INCOMPLETE][27] ([fdo#103927]) -> [PASS][28]
   [27]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-apl4/igt@gem_fence_thrash@bo-write-verify-threaded-x.html
   [28]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-apl7/igt@gem_fence_thrash@bo-write-verify-threaded-x.html

  * igt@i915_suspend@sysfs-reader:
    - shard-apl:          [DMESG-WARN][29] ([fdo#108566]) -> [PASS][30] +7 similar issues
   [29]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-apl8/igt@i915_suspend@sysfs-reader.html
   [30]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-apl2/igt@i915_suspend@sysfs-reader.html

  * igt@kms_cursor_crc@pipe-b-cursor-128x128-offscreen:
    - shard-skl:          [FAIL][31] ([fdo#103232]) -> [PASS][32]
   [31]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl7/igt@kms_cursor_crc@pipe-b-cursor-128x128-offscreen.html
   [32]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl10/igt@kms_cursor_crc@pipe-b-cursor-128x128-offscreen.html

  * igt@kms_cursor_crc@pipe-c-cursor-256x85-offscreen:
    - shard-iclb:         [INCOMPLETE][33] ([fdo#107713]) -> [PASS][34]
   [33]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb7/igt@kms_cursor_crc@pipe-c-cursor-256x85-offscreen.html
   [34]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb6/igt@kms_cursor_crc@pipe-c-cursor-256x85-offscreen.html

  * igt@kms_flip@flip-vs-suspend-interruptible:
    - shard-snb:          [INCOMPLETE][35] ([fdo#105411]) -> [PASS][36]
   [35]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-snb1/igt@kms_flip@flip-vs-suspend-interruptible.html
   [36]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-snb7/igt@kms_flip@flip-vs-suspend-interruptible.html

  * igt@kms_frontbuffer_tracking@fbc-1p-offscren-pri-shrfb-draw-pwrite:
    - shard-iclb:         [FAIL][37] ([fdo#103167]) -> [PASS][38] +1 similar issue
   [37]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb2/igt@kms_frontbuffer_tracking@fbc-1p-offscren-pri-shrfb-draw-pwrite.html
   [38]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb1/igt@kms_frontbuffer_tracking@fbc-1p-offscren-pri-shrfb-draw-pwrite.html

  * igt@kms_frontbuffer_tracking@fbcpsr-1p-rte:
    - shard-iclb:         [FAIL][39] ([fdo#103167] / [fdo#110378]) -> [PASS][40]
   [39]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb2/igt@kms_frontbuffer_tracking@fbcpsr-1p-rte.html
   [40]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb7/igt@kms_frontbuffer_tracking@fbcpsr-1p-rte.html

  * igt@kms_pipe_crc_basic@suspend-read-crc-pipe-c:
    - shard-kbl:          [INCOMPLETE][41] ([fdo#103665]) -> [PASS][42]
   [41]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-kbl4/igt@kms_pipe_crc_basic@suspend-read-crc-pipe-c.html
   [42]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-kbl1/igt@kms_pipe_crc_basic@suspend-read-crc-pipe-c.html

  * igt@kms_plane_alpha_blend@pipe-b-constant-alpha-min:
    - shard-skl:          [FAIL][43] ([fdo#108145]) -> [PASS][44]
   [43]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl7/igt@kms_plane_alpha_blend@pipe-b-constant-alpha-min.html
   [44]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl10/igt@kms_plane_alpha_blend@pipe-b-constant-alpha-min.html

  * igt@kms_psr@psr2_cursor_mmap_cpu:
    - shard-iclb:         [SKIP][45] ([fdo#109441]) -> [PASS][46] +2 similar issues
   [45]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb5/igt@kms_psr@psr2_cursor_mmap_cpu.html
   [46]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb2/igt@kms_psr@psr2_cursor_mmap_cpu.html

  * igt@kms_rotation_crc@primary-y-tiled-reflect-x-90:
    - shard-iclb:         [INCOMPLETE][47] ([fdo#107713] / [fdo#110026] / [fdo#110040 ]) -> [PASS][48]
   [47]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb1/igt@kms_rotation_crc@primary-y-tiled-reflect-x-90.html
   [48]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb7/igt@kms_rotation_crc@primary-y-tiled-reflect-x-90.html

  * igt@kms_setmode@basic:
    - shard-skl:          [FAIL][49] ([fdo#99912]) -> [PASS][50]
   [49]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl9/igt@kms_setmode@basic.html
   [50]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl7/igt@kms_setmode@basic.html

  * igt@perf@polling:
    - shard-skl:          [FAIL][51] ([fdo#110728]) -> [PASS][52]
   [51]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-skl6/igt@perf@polling.html
   [52]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-skl4/igt@perf@polling.html

  * igt@prime_vgem@fence-wait-bsd2:
    - shard-iclb:         [SKIP][53] ([fdo#109276]) -> [PASS][54] +18 similar issues
   [53]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb7/igt@prime_vgem@fence-wait-bsd2.html
   [54]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb4/igt@prime_vgem@fence-wait-bsd2.html

  
#### Warnings ####

  * igt@gem_ctx_isolation@vcs1-nonpriv:
    - shard-iclb:         [FAIL][55] ([fdo#111329]) -> [SKIP][56] ([fdo#109276])
   [55]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb4/igt@gem_ctx_isolation@vcs1-nonpriv.html
   [56]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb5/igt@gem_ctx_isolation@vcs1-nonpriv.html

  * igt@gem_mocs_settings@mocs-reset-bsd2:
    - shard-iclb:         [SKIP][57] ([fdo#109276]) -> [FAIL][58] ([fdo#111330]) +1 similar issue
   [57]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6854/shard-iclb5/igt@gem_mocs_settings@mocs-reset-bsd2.html
   [58]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/shard-iclb2/igt@gem_mocs_settings@mocs-reset-bsd2.html

  
  [fdo#103167]: https://bugs.freedesktop.org/show_bug.cgi?id=103167
  [fdo#103232]: https://bugs.freedesktop.org/show_bug.cgi?id=103232
  [fdo#103540]: https://bugs.freedesktop.org/show_bug.cgi?id=103540
  [fdo#103665]: https://bugs.freedesktop.org/show_bug.cgi?id=103665
  [fdo#103927]: https://bugs.freedesktop.org/show_bug.cgi?id=103927
  [fdo#105411]: https://bugs.freedesktop.org/show_bug.cgi?id=105411
  [fdo#105767]: https://bugs.freedesktop.org/show_bug.cgi?id=105767
  [fdo#106107]: https://bugs.freedesktop.org/show_bug.cgi?id=106107
  [fdo#107713]: https://bugs.freedesktop.org/show_bug.cgi?id=107713
  [fdo#108145]: https://bugs.freedesktop.org/show_bug.cgi?id=108145
  [fdo#108566]: https://bugs.freedesktop.org/show_bug.cgi?id=108566
  [fdo#109276]: https://bugs.freedesktop.org/show_bug.cgi?id=109276
  [fdo#109441]: https://bugs.freedesktop.org/show_bug.cgi?id=109441
  [fdo#109642]: https://bugs.freedesktop.org/show_bug.cgi?id=109642
  [fdo#110026]: https://bugs.freedesktop.org/show_bug.cgi?id=110026
  [fdo#110040 ]: https://bugs.freedesktop.org/show_bug.cgi?id=110040 
  [fdo#110378]: https://bugs.freedesktop.org/show_bug.cgi?id=110378
  [fdo#110403]: https://bugs.freedesktop.org/show_bug.cgi?id=110403
  [fdo#110728]: https://bugs.freedesktop.org/show_bug.cgi?id=110728
  [fdo#110841]: https://bugs.freedesktop.org/show_bug.cgi?id=110841
  [fdo#111068]: https://bugs.freedesktop.org/show_bug.cgi?id=111068
  [fdo#111325]: https://bugs.freedesktop.org/show_bug.cgi?id=111325
  [fdo#111329]: https://bugs.freedesktop.org/show_bug.cgi?id=111329
  [fdo#111330]: https://bugs.freedesktop.org/show_bug.cgi?id=111330
  [fdo#99912]: https://bugs.freedesktop.org/show_bug.cgi?id=99912


Participating hosts (10 -> 10)
------------------------------

  No changes in participating hosts


Build changes
-------------

  * CI: CI-20190529 -> None
  * Linux: CI_DRM_6854 -> Patchwork_14327

  CI-20190529: 20190529
  CI_DRM_6854: 5a70800ed2837e2d35a331e2cfd43a55df58c4fc @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_5176: 0102dcf4e2e8b357b59173fe1ff78069148080c6 @ git://anongit.freedesktop.org/xorg/app/intel-gpu-tools
  Patchwork_14327: cda3b809297cb7c5b44e6c9abe22cc4b7516a98d @ git://anongit.freedesktop.org/gfx-ci/linux
  piglit_4509: fdc5a4ca11124ab8413c7988896eec4c97336694 @ git://anongit.freedesktop.org/piglit

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14327/
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Re: [PATCH] drm/i915/ringbuffer: Flush writes before RING_TAIL update

[Mika Kuoppala]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Be paranoid and make sure we flush any and all writes out of the WCB
> before performing the UC mmio to update the RING_TAIL. (An UC write
> should itself be enough to do the flush, hence the paranoia here.) Quite
> infrequently, we see problems where the GPU seems to overshoot the
> RING_TAIL and so executes garbage hence the speculation.
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=111598
> References: https://bugs.freedesktop.org/show_bug.cgi?id=111417
> References: https://bugs.freedesktop.org/show_bug.cgi?id=111034
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

It could be even that the cost is ameliorated with the uc write,
if the hw is clever enough. Regardless, we gain a datapoint
with marginal cost.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
> index bbda85dcaa42..73c3ffc80218 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
> @@ -930,6 +930,7 @@ static void cancel_requests(struct intel_engine_cs *engine)
>  static void i9xx_submit_request(struct i915_request *request)
>  {
>  	i915_request_submit(request);
> +	wmb(); /* paranoid flush writes out of the WCB before mmio */
>  
>  	ENGINE_WRITE(request->engine, RING_TAIL,
>  		     intel_ring_set_tail(request->ring, request->tail));
> -- 
> 2.23.0
>
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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