[PATCH v4 0/2] Fix TLB invalidate issues with Broadwell

[PATCH v4 0/2] Fix TLB invalidate issues with Broadwell

[Mauro Carvalho Chehab]

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 together with i915 reset.

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

v4:
- No functional changes. All changes are at the patch descriptions:
  - collected acked-by/reviewed-by;
  - use the same e-mail on Author and SoB on patch 1.

v3:
- Removed the logic that would check if the engine is awake before doing
  TLB flush invalidation as backporting PM logic up to Kernel 4.x could be
  too painful. After getting this one merged, I'll submit a separate patch
  with the PM awake logic.

v2:

- Reduced to bare minimum fixes, as this shoud be backported deeply
  into stable.
Chris Wilson (2):
  drm/i915/gt: Serialize GRDOM access between multiple engine resets
  drm/i915/gt: Serialize TLB invalidates with GT resets

 drivers/gpu/drm/i915/gt/intel_gt.c    | 15 ++++++++++-
 drivers/gpu/drm/i915/gt/intel_reset.c | 37 ++++++++++++++++++++-------
 2 files changed, 42 insertions(+), 10 deletions(-)

-- 
2.36.1

[PATCH v4 1/2] drm/i915/gt: Serialize GRDOM access between multiple engine resets

[Mauro Carvalho Chehab]

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

Don't allow two engines to be reset in parallel, as they would both
try to select a reset bit (and send requests to common registers)
and wait on that register, at the same time. Serialize control of
the reset requests/acks using the uncore->lock, which will also ensure
that no other GT state changes at the same time as the actual reset.

Cc: stable@vger.kernel.org # v4.4 and upper
Reported-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

See [PATCH v4 0/2] at: https://lore.kernel.org/all/cover.1657522157.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gt/intel_reset.c | 37 ++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index a5338c3fde7a..c68d36fb5bbd 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -300,9 +300,9 @@ static int gen6_hw_domain_reset(struct intel_gt *gt, u32 hw_domain_mask)
 	return err;
 }
 
-static int gen6_reset_engines(struct intel_gt *gt,
-			      intel_engine_mask_t engine_mask,
-			      unsigned int retry)
+static int __gen6_reset_engines(struct intel_gt *gt,
+				intel_engine_mask_t engine_mask,
+				unsigned int retry)
 {
 	struct intel_engine_cs *engine;
 	u32 hw_mask;
@@ -321,6 +321,20 @@ static int gen6_reset_engines(struct intel_gt *gt,
 	return gen6_hw_domain_reset(gt, hw_mask);
 }
 
+static int gen6_reset_engines(struct intel_gt *gt,
+			      intel_engine_mask_t engine_mask,
+			      unsigned int retry)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&gt->uncore->lock, flags);
+	ret = __gen6_reset_engines(gt, engine_mask, retry);
+	spin_unlock_irqrestore(&gt->uncore->lock, flags);
+
+	return ret;
+}
+
 static struct intel_engine_cs *find_sfc_paired_vecs_engine(struct intel_engine_cs *engine)
 {
 	int vecs_id;
@@ -487,9 +501,9 @@ static void gen11_unlock_sfc(struct intel_engine_cs *engine)
 	rmw_clear_fw(uncore, sfc_lock.lock_reg, sfc_lock.lock_bit);
 }
 
-static int gen11_reset_engines(struct intel_gt *gt,
-			       intel_engine_mask_t engine_mask,
-			       unsigned int retry)
+static int __gen11_reset_engines(struct intel_gt *gt,
+				 intel_engine_mask_t engine_mask,
+				 unsigned int retry)
 {
 	struct intel_engine_cs *engine;
 	intel_engine_mask_t tmp;
@@ -583,8 +597,11 @@ static int gen8_reset_engines(struct intel_gt *gt,
 	struct intel_engine_cs *engine;
 	const bool reset_non_ready = retry >= 1;
 	intel_engine_mask_t tmp;
+	unsigned long flags;
 	int ret;
 
+	spin_lock_irqsave(&gt->uncore->lock, flags);
+
 	for_each_engine_masked(engine, gt, engine_mask, tmp) {
 		ret = gen8_engine_reset_prepare(engine);
 		if (ret && !reset_non_ready)
@@ -612,17 +629,19 @@ static int gen8_reset_engines(struct intel_gt *gt,
 	 * This is best effort, so ignore any error from the initial reset.
 	 */
 	if (IS_DG2(gt->i915) && engine_mask == ALL_ENGINES)
-		gen11_reset_engines(gt, gt->info.engine_mask, 0);
+		__gen11_reset_engines(gt, gt->info.engine_mask, 0);
 
 	if (GRAPHICS_VER(gt->i915) >= 11)
-		ret = gen11_reset_engines(gt, engine_mask, retry);
+		ret = __gen11_reset_engines(gt, engine_mask, retry);
 	else
-		ret = gen6_reset_engines(gt, engine_mask, retry);
+		ret = __gen6_reset_engines(gt, engine_mask, retry);
 
 skip_reset:
 	for_each_engine_masked(engine, gt, engine_mask, tmp)
 		gen8_engine_reset_cancel(engine);
 
+	spin_unlock_irqrestore(&gt->uncore->lock, flags);
+
 	return ret;
 }
 
-- 
2.36.1

[PATCH v4 2/2] drm/i915/gt: Serialize TLB invalidates with GT resets

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson@intel.com>

Avoid trying to invalidate the TLB in the middle of performing an
engine reset, as this may result in the reset timing out. Currently,
the TLB invalidate is only serialised by its own mutex, forgoing the
uncore lock, but we can take the uncore->lock as well to serialise
the mmio access, thereby serialising with the GDRST.

Tested on a NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 with
i915 selftest/hangcheck.

Cc: stable@vger.kernel.org  # v4.4 and upper
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Reported-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Tested-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
---

See [PATCH v4 0/2] at: https://lore.kernel.org/all/cover.1657522157.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gt/intel_gt.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 8da3314bb6bf..68c2b0d8f187 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -952,6 +952,20 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	mutex_lock(&gt->tlb_invalidate_lock);
 	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
 
+	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
+
+	for_each_engine(engine, gt, id) {
+		struct reg_and_bit rb;
+
+		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
+		if (!i915_mmio_reg_offset(rb.reg))
+			continue;
+
+		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
+	}
+
+	spin_unlock_irq(&uncore->lock);
+
 	for_each_engine(engine, gt, id) {
 		/*
 		 * HW architecture suggest typical invalidation time at 40us,
@@ -966,7 +980,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 		if (!i915_mmio_reg_offset(rb.reg))
 			continue;
 
-		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
 		if (__intel_wait_for_register_fw(uncore,
 						 rb.reg, rb.bit, 0,
 						 timeout_us, timeout_ms,
-- 
2.36.1