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From:   Mauro Carvalho Chehab <mchehab@kernel.org>
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Subject: [PATCH v2 0/3] Fix TLB invalidate issues with Broadwell
Date:   Wed, 29 Jun 2022 16:25:23 +0100
Message-Id: <cover.1656516220.git.mchehab@kernel.org>
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i915 selftest hangcheck is causing the i915 driver timeouts, as reported
by Intel CI bot:

http://gfx-ci.fi.intel.com/cibuglog-ng/issuefilterassoc/24297?query_key=42a999f48fa6ecce068bc8126c069be7c31153b4

When such test runs, the only output is:

	[   68.811639] i915: Performing live selftests with st_random_seed=0xe138eac7 st_timeout=500
	[   68.811792] i915: Running hangcheck
	[   68.811859] i915: Running intel_hangcheck_live_selftests/igt_hang_sanitycheck
	[   68.816910] i915 0000:00:02.0: [drm] Cannot find any crtc or sizes
	[   68.841597] i915: Running intel_hangcheck_live_selftests/igt_reset_nop
	[   69.346347] igt_reset_nop: 80 resets
	[   69.362695] i915: Running intel_hangcheck_live_selftests/igt_reset_nop_engine
	[   69.863559] igt_reset_nop_engine(rcs0): 709 resets
	[   70.364924] igt_reset_nop_engine(bcs0): 903 resets
	[   70.866005] igt_reset_nop_engine(vcs0): 659 resets
	[   71.367934] igt_reset_nop_engine(vcs1): 549 resets
	[   71.869259] igt_reset_nop_engine(vecs0): 553 resets
	[   71.882592] i915: Running intel_hangcheck_live_selftests/igt_reset_idle_engine
	[   72.383554] rcs0: Completed 16605 idle resets
	[   72.884599] bcs0: Completed 18641 idle resets
	[   73.385592] vcs0: Completed 17517 idle resets
	[   73.886658] vcs1: Completed 15474 idle resets
	[   74.387600] vecs0: Completed 17983 idle resets
	[   74.387667] i915: Running intel_hangcheck_live_selftests/igt_reset_active_engine
	[   74.889017] rcs0: Completed 747 active resets
	[   75.174240] intel_engine_reset(bcs0) failed, err:-110
	[   75.174301] bcs0: Completed 525 active resets

After that, the machine just silently hangs.

Bisecting the issue, the patch that introduced the regression is:

    7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Reverting it fix the issues, but introduce other problems, as TLB
won't be invalidated anymore. So, instead, let's fix the root cause.

It turns that the TLB flush logic ends conflicting with i915 reset,
which is called during selftest hangcheck. So, the TLB cache should
be serialized, but other TLB fix patches are required for this one
to work.

Tested on an Intel NUC5i7RYB with an i7-5557U Broadwell CPU.

v2:

- Reduced to bare minimum fixes, as this shoud be backported deeply
  into stable.

Chris Wilson (3):
  drm/i915/gt: Ignore TLB invalidations on idle engines
  drm/i915/gt: Serialize GRDOM access between multiple engine resets
  drm/i915/gt: Serialize TLB invalidates with GT resets

 drivers/gpu/drm/i915/gem/i915_gem_pages.c | 10 +++---
 drivers/gpu/drm/i915/gt/intel_gt.c        | 30 +++++++++++++-----
 drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  3 ++
 drivers/gpu/drm/i915/gt/intel_reset.c     | 37 +++++++++++++++++------
 4 files changed, 60 insertions(+), 20 deletions(-)

-- 
2.36.1