[PATCH v5 0/4] Improve anti-pre-emption w/a for compute workloads

[PATCH v5 0/4] Improve anti-pre-emption w/a for compute workloads

[John.C.Harrison]

From: John Harrison <John.C.Harrison@Intel.com>

Compute workloads are inherently not pre-emptible on current hardware.
Thus the pre-emption timeout was disabled as a workaround to prevent
unwanted resets. Instead, the hang detection was left to the heartbeat
and its (longer) timeout. This is undesirable with GuC submission as
the heartbeat is a full GT reset rather than a per engine reset and so
is much more destructive. Instead, just bump the pre-emption timeout
to a big value. Also, update the heartbeat to allow such a long
pre-emption delay in the final heartbeat period.

v2: Add clamping helpers.
v3: Remove long timeout algorithm and replace with hard coded value
(review feedback from Tvrtko). Also, fix execlist selftest failure and
fix bug in compute enabling patch related to pre-emption timeouts.
v4: Add multiple BUG_ONs to re-check already range checked values (Tvrtko)
v5: Add FIXMEs and drm_notices about setting non-default heartbeat
periods (Tvrtko)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>


John Harrison (4):
  drm/i915/guc: Limit scheduling properties to avoid overflow
  drm/i915: Fix compute pre-emption w/a to apply to compute engines
  drm/i915: Make the heartbeat play nice with long pre-emption timeouts
  drm/i915: Improve long running compute w/a for GuC submission

 drivers/gpu/drm/i915/Kconfig.profile          |  26 ++++-
 drivers/gpu/drm/i915/gt/intel_engine.h        |   6 ++
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 102 +++++++++++++++---
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  |  39 +++++++
 drivers/gpu/drm/i915/gt/sysfs_engines.c       |  25 +++--
 drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   |  21 ++++
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c |   8 ++
 7 files changed, 199 insertions(+), 28 deletions(-)

-- 
2.37.3

[PATCH v5 1/4] drm/i915/guc: Limit scheduling properties to avoid overflow

[John.C.Harrison]

From: John Harrison <John.C.Harrison@Intel.com>

GuC converts the pre-emption timeout and timeslice quantum values into
clock ticks internally. That significantly reduces the point of 32bit
overflow. On current platforms, worst case scenario is approximately
110 seconds. Rather than allowing the user to set higher values and
then get confused by early timeouts, add limits when setting these
values.

v2: Add helper functions for clamping (review feedback from Tvrtko).
v3: Add a bunch of BUG_ON range checks in addition to the checks
already in the clamping functions (Tvrtko)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> (v1)
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine.h        |  6 ++
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 69 +++++++++++++++++++
 drivers/gpu/drm/i915/gt/sysfs_engines.c       | 25 ++++---
 drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   | 21 ++++++
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  8 +++
 5 files changed, 119 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 04e435bce79bd..cbc8b857d5f7a 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -348,4 +348,10 @@ intel_engine_get_hung_context(struct intel_engine_cs *engine)
 	return engine->hung_ce;
 }
 
+u64 intel_clamp_heartbeat_interval_ms(struct intel_engine_cs *engine, u64 value);
+u64 intel_clamp_max_busywait_duration_ns(struct intel_engine_cs *engine, u64 value);
+u64 intel_clamp_preempt_timeout_ms(struct intel_engine_cs *engine, u64 value);
+u64 intel_clamp_stop_timeout_ms(struct intel_engine_cs *engine, u64 value);
+u64 intel_clamp_timeslice_duration_ms(struct intel_engine_cs *engine, u64 value);
+
 #endif /* _INTEL_RINGBUFFER_H_ */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 2ddcad497fa30..8f16955f0821e 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -512,6 +512,26 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
 		engine->flags |= I915_ENGINE_HAS_EU_PRIORITY;
 	}
 
+	/* Cap properties according to any system limits */
+#define CLAMP_PROP(field) \
+	do { \
+		u64 clamp = intel_clamp_##field(engine, engine->props.field); \
+		if (clamp != engine->props.field) { \
+			drm_notice(&engine->i915->drm, \
+				   "Warning, clamping %s to %lld to prevent overflow\n", \
+				   #field, clamp); \
+			engine->props.field = clamp; \
+		} \
+	} while (0)
+
+	CLAMP_PROP(heartbeat_interval_ms);
+	CLAMP_PROP(max_busywait_duration_ns);
+	CLAMP_PROP(preempt_timeout_ms);
+	CLAMP_PROP(stop_timeout_ms);
+	CLAMP_PROP(timeslice_duration_ms);
+
+#undef CLAMP_PROP
+
 	engine->defaults = engine->props; /* never to change again */
 
 	engine->context_size = intel_engine_context_size(gt, engine->class);
@@ -534,6 +554,55 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
 	return 0;
 }
 
+u64 intel_clamp_heartbeat_interval_ms(struct intel_engine_cs *engine, u64 value)
+{
+	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
+
+	return value;
+}
+
+u64 intel_clamp_max_busywait_duration_ns(struct intel_engine_cs *engine, u64 value)
+{
+	value = min(value, jiffies_to_nsecs(2));
+
+	return value;
+}
+
+u64 intel_clamp_preempt_timeout_ms(struct intel_engine_cs *engine, u64 value)
+{
+	/*
+	 * NB: The GuC API only supports 32bit values. However, the limit is further
+	 * reduced due to internal calculations which would otherwise overflow.
+	 */
+	if (intel_guc_submission_is_wanted(&engine->gt->uc.guc))
+		value = min_t(u64, value, guc_policy_max_preempt_timeout_ms());
+
+	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
+
+	return value;
+}
+
+u64 intel_clamp_stop_timeout_ms(struct intel_engine_cs *engine, u64 value)
+{
+	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
+
+	return value;
+}
+
+u64 intel_clamp_timeslice_duration_ms(struct intel_engine_cs *engine, u64 value)
+{
+	/*
+	 * NB: The GuC API only supports 32bit values. However, the limit is further
+	 * reduced due to internal calculations which would otherwise overflow.
+	 */
+	if (intel_guc_submission_is_wanted(&engine->gt->uc.guc))
+		value = min_t(u64, value, guc_policy_max_exec_quantum_ms());
+
+	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
+
+	return value;
+}
+
 static void __setup_engine_capabilities(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *i915 = engine->i915;
diff --git a/drivers/gpu/drm/i915/gt/sysfs_engines.c b/drivers/gpu/drm/i915/gt/sysfs_engines.c
index 9670310562029..f2d9858d827c2 100644
--- a/drivers/gpu/drm/i915/gt/sysfs_engines.c
+++ b/drivers/gpu/drm/i915/gt/sysfs_engines.c
@@ -144,7 +144,7 @@ max_spin_store(struct kobject *kobj, struct kobj_attribute *attr,
 	       const char *buf, size_t count)
 {
 	struct intel_engine_cs *engine = kobj_to_engine(kobj);
-	unsigned long long duration;
+	unsigned long long duration, clamped;
 	int err;
 
 	/*
@@ -168,7 +168,8 @@ max_spin_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (err)
 		return err;
 
-	if (duration > jiffies_to_nsecs(2))
+	clamped = intel_clamp_max_busywait_duration_ns(engine, duration);
+	if (duration != clamped)
 		return -EINVAL;
 
 	WRITE_ONCE(engine->props.max_busywait_duration_ns, duration);
@@ -203,7 +204,7 @@ timeslice_store(struct kobject *kobj, struct kobj_attribute *attr,
 		const char *buf, size_t count)
 {
 	struct intel_engine_cs *engine = kobj_to_engine(kobj);
-	unsigned long long duration;
+	unsigned long long duration, clamped;
 	int err;
 
 	/*
@@ -218,7 +219,8 @@ timeslice_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (err)
 		return err;
 
-	if (duration > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
+	clamped = intel_clamp_timeslice_duration_ms(engine, duration);
+	if (duration != clamped)
 		return -EINVAL;
 
 	WRITE_ONCE(engine->props.timeslice_duration_ms, duration);
@@ -256,7 +258,7 @@ stop_store(struct kobject *kobj, struct kobj_attribute *attr,
 	   const char *buf, size_t count)
 {
 	struct intel_engine_cs *engine = kobj_to_engine(kobj);
-	unsigned long long duration;
+	unsigned long long duration, clamped;
 	int err;
 
 	/*
@@ -272,7 +274,8 @@ stop_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (err)
 		return err;
 
-	if (duration > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
+	clamped = intel_clamp_stop_timeout_ms(engine, duration);
+	if (duration != clamped)
 		return -EINVAL;
 
 	WRITE_ONCE(engine->props.stop_timeout_ms, duration);
@@ -306,7 +309,7 @@ preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
 		      const char *buf, size_t count)
 {
 	struct intel_engine_cs *engine = kobj_to_engine(kobj);
-	unsigned long long timeout;
+	unsigned long long timeout, clamped;
 	int err;
 
 	/*
@@ -322,7 +325,8 @@ preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (err)
 		return err;
 
-	if (timeout > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
+	clamped = intel_clamp_preempt_timeout_ms(engine, timeout);
+	if (timeout != clamped)
 		return -EINVAL;
 
 	WRITE_ONCE(engine->props.preempt_timeout_ms, timeout);
@@ -362,7 +366,7 @@ heartbeat_store(struct kobject *kobj, struct kobj_attribute *attr,
 		const char *buf, size_t count)
 {
 	struct intel_engine_cs *engine = kobj_to_engine(kobj);
-	unsigned long long delay;
+	unsigned long long delay, clamped;
 	int err;
 
 	/*
@@ -379,7 +383,8 @@ heartbeat_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (err)
 		return err;
 
-	if (delay >= jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
+	clamped = intel_clamp_heartbeat_interval_ms(engine, delay);
+	if (delay != clamped)
 		return -EINVAL;
 
 	err = intel_engine_set_heartbeat(engine, delay);
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
index e7a7fb450f442..968ebd79dce70 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
@@ -327,6 +327,27 @@ struct guc_update_scheduling_policy {
 
 #define GLOBAL_POLICY_DEFAULT_DPC_PROMOTE_TIME_US 500000
 
+/*
+ * GuC converts the timeout to clock ticks internally. Different platforms have
+ * different GuC clocks. Thus, the maximum value before overflow is platform
+ * dependent. Current worst case scenario is about 110s. So, the spec says to
+ * limit to 100s to be safe.
+ */
+#define GUC_POLICY_MAX_EXEC_QUANTUM_US		(100 * 1000 * 1000UL)
+#define GUC_POLICY_MAX_PREEMPT_TIMEOUT_US	(100 * 1000 * 1000UL)
+
+static inline u32 guc_policy_max_exec_quantum_ms(void)
+{
+	BUILD_BUG_ON(GUC_POLICY_MAX_EXEC_QUANTUM_US >= UINT_MAX);
+	return GUC_POLICY_MAX_EXEC_QUANTUM_US / 1000;
+}
+
+static inline u32 guc_policy_max_preempt_timeout_ms(void)
+{
+	BUILD_BUG_ON(GUC_POLICY_MAX_PREEMPT_TIMEOUT_US >= UINT_MAX);
+	return GUC_POLICY_MAX_PREEMPT_TIMEOUT_US / 1000;
+}
+
 struct guc_policies {
 	u32 submission_queue_depth[GUC_MAX_ENGINE_CLASSES];
 	/* In micro seconds. How much time to allow before DPC processing is
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 693b07a977893..c433d35ae41ae 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -2430,6 +2430,10 @@ static int guc_context_policy_init_v70(struct intel_context *ce, bool loop)
 	int ret;
 
 	/* NB: For both of these, zero means disabled. */
+	GEM_BUG_ON(overflows_type(engine->props.timeslice_duration_ms * 1000,
+				  execution_quantum));
+	GEM_BUG_ON(overflows_type(engine->props.preempt_timeout_ms * 1000,
+				  preemption_timeout));
 	execution_quantum = engine->props.timeslice_duration_ms * 1000;
 	preemption_timeout = engine->props.preempt_timeout_ms * 1000;
 
@@ -2463,6 +2467,10 @@ static void guc_context_policy_init_v69(struct intel_engine_cs *engine,
 		desc->policy_flags |= CONTEXT_POLICY_FLAG_PREEMPT_TO_IDLE_V69;
 
 	/* NB: For both of these, zero means disabled. */
+	GEM_BUG_ON(overflows_type(engine->props.timeslice_duration_ms * 1000,
+				  desc->execution_quantum));
+	GEM_BUG_ON(overflows_type(engine->props.preempt_timeout_ms * 1000,
+				  desc->preemption_timeout));
 	desc->execution_quantum = engine->props.timeslice_duration_ms * 1000;
 	desc->preemption_timeout = engine->props.preempt_timeout_ms * 1000;
 }
-- 
2.37.3

[PATCH v5 2/4] drm/i915: Fix compute pre-emption w/a to apply to compute engines

[John.C.Harrison]

From: John Harrison <John.C.Harrison@Intel.com>

An earlier patch added support for compute engines. However, it missed
enabling the anti-pre-emption w/a for the new engine class. So move
the 'compute capable' flag earlier and use it for the pre-emption w/a
test.

Fixes: c674c5b9342e ("drm/i915/xehp: CCS should use RCS setup functions")
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Aravind Iddamsetty <aravind.iddamsetty@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: "Michał Winiarski" <michal.winiarski@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 24 +++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 8f16955f0821e..fcbccd8d244e9 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -486,6 +486,17 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
 	engine->logical_mask = BIT(logical_instance);
 	__sprint_engine_name(engine);
 
+	if ((engine->class == COMPUTE_CLASS && !RCS_MASK(engine->gt) &&
+	     __ffs(CCS_MASK(engine->gt)) == engine->instance) ||
+	     engine->class == RENDER_CLASS)
+		engine->flags |= I915_ENGINE_FIRST_RENDER_COMPUTE;
+
+	/* features common between engines sharing EUs */
+	if (engine->class == RENDER_CLASS || engine->class == COMPUTE_CLASS) {
+		engine->flags |= I915_ENGINE_HAS_RCS_REG_STATE;
+		engine->flags |= I915_ENGINE_HAS_EU_PRIORITY;
+	}
+
 	engine->props.heartbeat_interval_ms =
 		CONFIG_DRM_I915_HEARTBEAT_INTERVAL;
 	engine->props.max_busywait_duration_ns =
@@ -498,20 +509,9 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
 		CONFIG_DRM_I915_TIMESLICE_DURATION;
 
 	/* Override to uninterruptible for OpenCL workloads. */
-	if (GRAPHICS_VER(i915) == 12 && engine->class == RENDER_CLASS)
+	if (GRAPHICS_VER(i915) == 12 && (engine->flags & I915_ENGINE_HAS_RCS_REG_STATE))
 		engine->props.preempt_timeout_ms = 0;
 
-	if ((engine->class == COMPUTE_CLASS && !RCS_MASK(engine->gt) &&
-	     __ffs(CCS_MASK(engine->gt)) == engine->instance) ||
-	     engine->class == RENDER_CLASS)
-		engine->flags |= I915_ENGINE_FIRST_RENDER_COMPUTE;
-
-	/* features common between engines sharing EUs */
-	if (engine->class == RENDER_CLASS || engine->class == COMPUTE_CLASS) {
-		engine->flags |= I915_ENGINE_HAS_RCS_REG_STATE;
-		engine->flags |= I915_ENGINE_HAS_EU_PRIORITY;
-	}
-
 	/* Cap properties according to any system limits */
 #define CLAMP_PROP(field) \
 	do { \
-- 
2.37.3

[PATCH v5 3/4] drm/i915: Make the heartbeat play nice with long pre-emption timeouts

[John.C.Harrison]

From: John Harrison <John.C.Harrison@Intel.com>

Compute workloads are inherently not pre-emptible for long periods on
current hardware. As a workaround for this, the pre-emption timeout
for compute capable engines was disabled. This is undesirable with GuC
submission as it prevents per engine reset of hung contexts. Hence the
next patch will re-enable the timeout but bumped up by an order of
magnitude.

However, the heartbeat might not respect that. Depending upon current
activity, a pre-emption to the heartbeat pulse might not even be
attempted until the last heartbeat period. Which means that only one
period is granted for the pre-emption to occur. With the aforesaid
bump, the pre-emption timeout could be significantly larger than this
heartbeat period.

So adjust the heartbeat code to take the pre-emption timeout into
account. When it reaches the final (high priority) period, it now
ensures the delay before hitting reset is bigger than the pre-emption
timeout.

v2: Fix for selftests which adjust the heartbeat period manually.
v3: Add FIXME comment about selftests. Add extra FIXME comment and
drm_notices when setting heartbeat to a non-default value (review
feedback from Tvrtko)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
---
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index a3698f611f457..9a527e1f5be65 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -22,9 +22,37 @@
 
 static bool next_heartbeat(struct intel_engine_cs *engine)
 {
+	struct i915_request *rq;
 	long delay;
 
 	delay = READ_ONCE(engine->props.heartbeat_interval_ms);
+
+	rq = engine->heartbeat.systole;
+
+	/*
+	 * FIXME: The final period extension is disabled if the period has been
+	 * modified from the default. This is to prevent issues with certain
+	 * selftests which override the value and expect specific behaviour.
+	 * Once the selftests have been updated to either cope with variable
+	 * heartbeat periods (or to override the pre-emption timeout as well,
+	 * or just to add a selftest specific override of the extension), the
+	 * generic override can be removed.
+	 */
+	if (rq && rq->sched.attr.priority >= I915_PRIORITY_BARRIER &&
+	    delay == engine->defaults.heartbeat_interval_ms) {
+		long longer;
+
+		/*
+		 * The final try is at the highest priority possible. Up until now
+		 * a pre-emption might not even have been attempted. So make sure
+		 * this last attempt allows enough time for a pre-emption to occur.
+		 */
+		longer = READ_ONCE(engine->props.preempt_timeout_ms) * 2;
+		longer = intel_clamp_heartbeat_interval_ms(engine, longer);
+		if (longer > delay)
+			delay = longer;
+	}
+
 	if (!delay)
 		return false;
 
@@ -288,6 +316,17 @@ int intel_engine_set_heartbeat(struct intel_engine_cs *engine,
 	if (!delay && !intel_engine_has_preempt_reset(engine))
 		return -ENODEV;
 
+	/* FIXME: Remove together with equally marked hack in next_heartbeat. */
+	if (delay != engine->defaults.heartbeat_interval_ms &&
+	    delay < 2 * engine->props.preempt_timeout_ms) {
+		if (intel_engine_uses_guc(engine))
+			drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may downgrade individual engine resets to full GPU resets!\n",
+				   engine->name);
+		else
+			drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may cause engine resets to target innocent contexts!\n",
+				   engine->name);
+	}
+
 	intel_engine_pm_get(engine);
 
 	err = mutex_lock_interruptible(&ce->timeline->mutex);
-- 
2.37.3

[PATCH v5 4/4] drm/i915: Improve long running compute w/a for GuC submission

[John.C.Harrison]

From: John Harrison <John.C.Harrison@Intel.com>

A workaround was added to the driver to allow compute workloads to run
'forever' by disabling pre-emption on the RCS engine for Gen12.
It is not totally unbound as the heartbeat will kick in eventually
and cause a reset of the hung engine.

However, this does not work well in GuC submission mode. In GuC mode,
the pre-emption timeout is how GuC detects hung contexts and triggers
a per engine reset. Thus, disabling the timeout means also losing all
per engine reset ability. A full GT reset will still occur when the
heartbeat finally expires, but that is a much more destructive and
undesirable mechanism.

The purpose of the workaround is actually to give compute tasks longer
to reach a pre-emption point after a pre-emption request has been
issued. This is necessary because Gen12 does not support mid-thread
pre-emption and compute tasks can have long running threads.

So, rather than disabling the timeout completely, just set it to a
'long' value.

v2: Review feedback from Tvrtko - must hard code the 'long' value
instead of determining it algorithmically. So make it an extra CONFIG
definition. Also, remove the execlist centric comment from the
existing pre-emption timeout CONFIG option given that it applies to
more than just execlists.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> (v1)
Acked-by: Michal Mrozek <michal.mrozek@intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/Kconfig.profile      | 26 +++++++++++++++++++----
 drivers/gpu/drm/i915/gt/intel_engine_cs.c |  9 ++++++--
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
index 39328567c2007..7cc38d25ee5c8 100644
--- a/drivers/gpu/drm/i915/Kconfig.profile
+++ b/drivers/gpu/drm/i915/Kconfig.profile
@@ -57,10 +57,28 @@ config DRM_I915_PREEMPT_TIMEOUT
 	default 640 # milliseconds
 	help
 	  How long to wait (in milliseconds) for a preemption event to occur
-	  when submitting a new context via execlists. If the current context
-	  does not hit an arbitration point and yield to HW before the timer
-	  expires, the HW will be reset to allow the more important context
-	  to execute.
+	  when submitting a new context. If the current context does not hit
+	  an arbitration point and yield to HW before the timer expires, the
+	  HW will be reset to allow the more important context to execute.
+
+	  This is adjustable via
+	  /sys/class/drm/card?/engine/*/preempt_timeout_ms
+
+	  May be 0 to disable the timeout.
+
+	  The compiled in default may get overridden at driver probe time on
+	  certain platforms and certain engines which will be reflected in the
+	  sysfs control.
+
+config DRM_I915_PREEMPT_TIMEOUT_COMPUTE
+	int "Preempt timeout for compute engines (ms, jiffy granularity)"
+	default 7500 # milliseconds
+	help
+	  How long to wait (in milliseconds) for a preemption event to occur
+	  when submitting a new context to a compute capable engine. If the
+	  current context does not hit an arbitration point and yield to HW
+	  before the timer expires, the HW will be reset to allow the more
+	  important context to execute.
 
 	  This is adjustable via
 	  /sys/class/drm/card?/engine/*/preempt_timeout_ms
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index fcbccd8d244e9..c1257723d1949 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -508,9 +508,14 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
 	engine->props.timeslice_duration_ms =
 		CONFIG_DRM_I915_TIMESLICE_DURATION;
 
-	/* Override to uninterruptible for OpenCL workloads. */
+	/*
+	 * Mid-thread pre-emption is not available in Gen12. Unfortunately,
+	 * some compute workloads run quite long threads. That means they get
+	 * reset due to not pre-empting in a timely manner. So, bump the
+	 * pre-emption timeout value to be much higher for compute engines.
+	 */
 	if (GRAPHICS_VER(i915) == 12 && (engine->flags & I915_ENGINE_HAS_RCS_REG_STATE))
-		engine->props.preempt_timeout_ms = 0;
+		engine->props.preempt_timeout_ms = CONFIG_DRM_I915_PREEMPT_TIMEOUT_COMPUTE;
 
 	/* Cap properties according to any system limits */
 #define CLAMP_PROP(field) \
-- 
2.37.3

Re: [Intel-gfx] [PATCH v5 3/4] drm/i915: Make the heartbeat play nice with long pre-emption timeouts

[Tvrtko Ursulin]

On 06/10/2022 22:38, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> Compute workloads are inherently not pre-emptible for long periods on
> current hardware. As a workaround for this, the pre-emption timeout
> for compute capable engines was disabled. This is undesirable with GuC
> submission as it prevents per engine reset of hung contexts. Hence the
> next patch will re-enable the timeout but bumped up by an order of
> magnitude.
> 
> However, the heartbeat might not respect that. Depending upon current
> activity, a pre-emption to the heartbeat pulse might not even be
> attempted until the last heartbeat period. Which means that only one
> period is granted for the pre-emption to occur. With the aforesaid
> bump, the pre-emption timeout could be significantly larger than this
> heartbeat period.
> 
> So adjust the heartbeat code to take the pre-emption timeout into
> account. When it reaches the final (high priority) period, it now
> ensures the delay before hitting reset is bigger than the pre-emption
> timeout.
> 
> v2: Fix for selftests which adjust the heartbeat period manually.
> v3: Add FIXME comment about selftests. Add extra FIXME comment and
> drm_notices when setting heartbeat to a non-default value (review
> feedback from Tvrtko)
> 
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> ---
>   .../gpu/drm/i915/gt/intel_engine_heartbeat.c  | 39 +++++++++++++++++++
>   1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
> index a3698f611f457..9a527e1f5be65 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
> @@ -22,9 +22,37 @@
>   
>   static bool next_heartbeat(struct intel_engine_cs *engine)
>   {
> +	struct i915_request *rq;
>   	long delay;
>   
>   	delay = READ_ONCE(engine->props.heartbeat_interval_ms);
> +
> +	rq = engine->heartbeat.systole;
> +
> +	/*
> +	 * FIXME: The final period extension is disabled if the period has been
> +	 * modified from the default. This is to prevent issues with certain
> +	 * selftests which override the value and expect specific behaviour.
> +	 * Once the selftests have been updated to either cope with variable
> +	 * heartbeat periods (or to override the pre-emption timeout as well,
> +	 * or just to add a selftest specific override of the extension), the
> +	 * generic override can be removed.
> +	 */
> +	if (rq && rq->sched.attr.priority >= I915_PRIORITY_BARRIER &&
> +	    delay == engine->defaults.heartbeat_interval_ms) {
> +		long longer;
> +
> +		/*
> +		 * The final try is at the highest priority possible. Up until now
> +		 * a pre-emption might not even have been attempted. So make sure
> +		 * this last attempt allows enough time for a pre-emption to occur.
> +		 */
> +		longer = READ_ONCE(engine->props.preempt_timeout_ms) * 2;
> +		longer = intel_clamp_heartbeat_interval_ms(engine, longer);
> +		if (longer > delay)
> +			delay = longer;
> +	}
> +
>   	if (!delay)
>   		return false;
>   
> @@ -288,6 +316,17 @@ int intel_engine_set_heartbeat(struct intel_engine_cs *engine,
>   	if (!delay && !intel_engine_has_preempt_reset(engine))
>   		return -ENODEV;
>   
> +	/* FIXME: Remove together with equally marked hack in next_heartbeat. */
> +	if (delay != engine->defaults.heartbeat_interval_ms &&
> +	    delay < 2 * engine->props.preempt_timeout_ms) {
> +		if (intel_engine_uses_guc(engine))
> +			drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may downgrade individual engine resets to full GPU resets!\n",
> +				   engine->name);
> +		else
> +			drm_notice(&engine->i915->drm, "%s heartbeat interval adjusted to a non-default value which may cause engine resets to target innocent contexts!\n",
> +				   engine->name);
> +	}
> +
>   	intel_engine_pm_get(engine);
>   
>   	err = mutex_lock_interruptible(&ce->timeline->mutex);

LGTM - hope it is agreeable to you too.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

Re: [PATCH v5 1/4] drm/i915/guc: Limit scheduling properties to avoid overflow

[Ceraolo Spurio, Daniele]

On 10/6/2022 2:38 PM, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
>
> GuC converts the pre-emption timeout and timeslice quantum values into
> clock ticks internally. That significantly reduces the point of 32bit
> overflow. On current platforms, worst case scenario is approximately
> 110 seconds. Rather than allowing the user to set higher values and
> then get confused by early timeouts, add limits when setting these
> values.
>
> v2: Add helper functions for clamping (review feedback from Tvrtko).
> v3: Add a bunch of BUG_ON range checks in addition to the checks
> already in the clamping functions (Tvrtko)
>
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> (v1)

r-b stands

Daniele

> Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/gt/intel_engine.h        |  6 ++
>   drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 69 +++++++++++++++++++
>   drivers/gpu/drm/i915/gt/sysfs_engines.c       | 25 ++++---
>   drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   | 21 ++++++
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  8 +++
>   5 files changed, 119 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
> index 04e435bce79bd..cbc8b857d5f7a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine.h
> @@ -348,4 +348,10 @@ intel_engine_get_hung_context(struct intel_engine_cs *engine)
>   	return engine->hung_ce;
>   }
>   
> +u64 intel_clamp_heartbeat_interval_ms(struct intel_engine_cs *engine, u64 value);
> +u64 intel_clamp_max_busywait_duration_ns(struct intel_engine_cs *engine, u64 value);
> +u64 intel_clamp_preempt_timeout_ms(struct intel_engine_cs *engine, u64 value);
> +u64 intel_clamp_stop_timeout_ms(struct intel_engine_cs *engine, u64 value);
> +u64 intel_clamp_timeslice_duration_ms(struct intel_engine_cs *engine, u64 value);
> +
>   #endif /* _INTEL_RINGBUFFER_H_ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 2ddcad497fa30..8f16955f0821e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -512,6 +512,26 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
>   		engine->flags |= I915_ENGINE_HAS_EU_PRIORITY;
>   	}
>   
> +	/* Cap properties according to any system limits */
> +#define CLAMP_PROP(field) \
> +	do { \
> +		u64 clamp = intel_clamp_##field(engine, engine->props.field); \
> +		if (clamp != engine->props.field) { \
> +			drm_notice(&engine->i915->drm, \
> +				   "Warning, clamping %s to %lld to prevent overflow\n", \
> +				   #field, clamp); \
> +			engine->props.field = clamp; \
> +		} \
> +	} while (0)
> +
> +	CLAMP_PROP(heartbeat_interval_ms);
> +	CLAMP_PROP(max_busywait_duration_ns);
> +	CLAMP_PROP(preempt_timeout_ms);
> +	CLAMP_PROP(stop_timeout_ms);
> +	CLAMP_PROP(timeslice_duration_ms);
> +
> +#undef CLAMP_PROP
> +
>   	engine->defaults = engine->props; /* never to change again */
>   
>   	engine->context_size = intel_engine_context_size(gt, engine->class);
> @@ -534,6 +554,55 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
>   	return 0;
>   }
>   
> +u64 intel_clamp_heartbeat_interval_ms(struct intel_engine_cs *engine, u64 value)
> +{
> +	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
> +
> +	return value;
> +}
> +
> +u64 intel_clamp_max_busywait_duration_ns(struct intel_engine_cs *engine, u64 value)
> +{
> +	value = min(value, jiffies_to_nsecs(2));
> +
> +	return value;
> +}
> +
> +u64 intel_clamp_preempt_timeout_ms(struct intel_engine_cs *engine, u64 value)
> +{
> +	/*
> +	 * NB: The GuC API only supports 32bit values. However, the limit is further
> +	 * reduced due to internal calculations which would otherwise overflow.
> +	 */
> +	if (intel_guc_submission_is_wanted(&engine->gt->uc.guc))
> +		value = min_t(u64, value, guc_policy_max_preempt_timeout_ms());
> +
> +	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
> +
> +	return value;
> +}
> +
> +u64 intel_clamp_stop_timeout_ms(struct intel_engine_cs *engine, u64 value)
> +{
> +	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
> +
> +	return value;
> +}
> +
> +u64 intel_clamp_timeslice_duration_ms(struct intel_engine_cs *engine, u64 value)
> +{
> +	/*
> +	 * NB: The GuC API only supports 32bit values. However, the limit is further
> +	 * reduced due to internal calculations which would otherwise overflow.
> +	 */
> +	if (intel_guc_submission_is_wanted(&engine->gt->uc.guc))
> +		value = min_t(u64, value, guc_policy_max_exec_quantum_ms());
> +
> +	value = min_t(u64, value, jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT));
> +
> +	return value;
> +}
> +
>   static void __setup_engine_capabilities(struct intel_engine_cs *engine)
>   {
>   	struct drm_i915_private *i915 = engine->i915;
> diff --git a/drivers/gpu/drm/i915/gt/sysfs_engines.c b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> index 9670310562029..f2d9858d827c2 100644
> --- a/drivers/gpu/drm/i915/gt/sysfs_engines.c
> +++ b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> @@ -144,7 +144,7 @@ max_spin_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	       const char *buf, size_t count)
>   {
>   	struct intel_engine_cs *engine = kobj_to_engine(kobj);
> -	unsigned long long duration;
> +	unsigned long long duration, clamped;
>   	int err;
>   
>   	/*
> @@ -168,7 +168,8 @@ max_spin_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	if (err)
>   		return err;
>   
> -	if (duration > jiffies_to_nsecs(2))
> +	clamped = intel_clamp_max_busywait_duration_ns(engine, duration);
> +	if (duration != clamped)
>   		return -EINVAL;
>   
>   	WRITE_ONCE(engine->props.max_busywait_duration_ns, duration);
> @@ -203,7 +204,7 @@ timeslice_store(struct kobject *kobj, struct kobj_attribute *attr,
>   		const char *buf, size_t count)
>   {
>   	struct intel_engine_cs *engine = kobj_to_engine(kobj);
> -	unsigned long long duration;
> +	unsigned long long duration, clamped;
>   	int err;
>   
>   	/*
> @@ -218,7 +219,8 @@ timeslice_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	if (err)
>   		return err;
>   
> -	if (duration > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
> +	clamped = intel_clamp_timeslice_duration_ms(engine, duration);
> +	if (duration != clamped)
>   		return -EINVAL;
>   
>   	WRITE_ONCE(engine->props.timeslice_duration_ms, duration);
> @@ -256,7 +258,7 @@ stop_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	   const char *buf, size_t count)
>   {
>   	struct intel_engine_cs *engine = kobj_to_engine(kobj);
> -	unsigned long long duration;
> +	unsigned long long duration, clamped;
>   	int err;
>   
>   	/*
> @@ -272,7 +274,8 @@ stop_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	if (err)
>   		return err;
>   
> -	if (duration > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
> +	clamped = intel_clamp_stop_timeout_ms(engine, duration);
> +	if (duration != clamped)
>   		return -EINVAL;
>   
>   	WRITE_ONCE(engine->props.stop_timeout_ms, duration);
> @@ -306,7 +309,7 @@ preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
>   		      const char *buf, size_t count)
>   {
>   	struct intel_engine_cs *engine = kobj_to_engine(kobj);
> -	unsigned long long timeout;
> +	unsigned long long timeout, clamped;
>   	int err;
>   
>   	/*
> @@ -322,7 +325,8 @@ preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	if (err)
>   		return err;
>   
> -	if (timeout > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
> +	clamped = intel_clamp_preempt_timeout_ms(engine, timeout);
> +	if (timeout != clamped)
>   		return -EINVAL;
>   
>   	WRITE_ONCE(engine->props.preempt_timeout_ms, timeout);
> @@ -362,7 +366,7 @@ heartbeat_store(struct kobject *kobj, struct kobj_attribute *attr,
>   		const char *buf, size_t count)
>   {
>   	struct intel_engine_cs *engine = kobj_to_engine(kobj);
> -	unsigned long long delay;
> +	unsigned long long delay, clamped;
>   	int err;
>   
>   	/*
> @@ -379,7 +383,8 @@ heartbeat_store(struct kobject *kobj, struct kobj_attribute *attr,
>   	if (err)
>   		return err;
>   
> -	if (delay >= jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
> +	clamped = intel_clamp_heartbeat_interval_ms(engine, delay);
> +	if (delay != clamped)
>   		return -EINVAL;
>   
>   	err = intel_engine_set_heartbeat(engine, delay);
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> index e7a7fb450f442..968ebd79dce70 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> @@ -327,6 +327,27 @@ struct guc_update_scheduling_policy {
>   
>   #define GLOBAL_POLICY_DEFAULT_DPC_PROMOTE_TIME_US 500000
>   
> +/*
> + * GuC converts the timeout to clock ticks internally. Different platforms have
> + * different GuC clocks. Thus, the maximum value before overflow is platform
> + * dependent. Current worst case scenario is about 110s. So, the spec says to
> + * limit to 100s to be safe.
> + */
> +#define GUC_POLICY_MAX_EXEC_QUANTUM_US		(100 * 1000 * 1000UL)
> +#define GUC_POLICY_MAX_PREEMPT_TIMEOUT_US	(100 * 1000 * 1000UL)
> +
> +static inline u32 guc_policy_max_exec_quantum_ms(void)
> +{
> +	BUILD_BUG_ON(GUC_POLICY_MAX_EXEC_QUANTUM_US >= UINT_MAX);
> +	return GUC_POLICY_MAX_EXEC_QUANTUM_US / 1000;
> +}
> +
> +static inline u32 guc_policy_max_preempt_timeout_ms(void)
> +{
> +	BUILD_BUG_ON(GUC_POLICY_MAX_PREEMPT_TIMEOUT_US >= UINT_MAX);
> +	return GUC_POLICY_MAX_PREEMPT_TIMEOUT_US / 1000;
> +}
> +
>   struct guc_policies {
>   	u32 submission_queue_depth[GUC_MAX_ENGINE_CLASSES];
>   	/* In micro seconds. How much time to allow before DPC processing is
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 693b07a977893..c433d35ae41ae 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -2430,6 +2430,10 @@ static int guc_context_policy_init_v70(struct intel_context *ce, bool loop)
>   	int ret;
>   
>   	/* NB: For both of these, zero means disabled. */
> +	GEM_BUG_ON(overflows_type(engine->props.timeslice_duration_ms * 1000,
> +				  execution_quantum));
> +	GEM_BUG_ON(overflows_type(engine->props.preempt_timeout_ms * 1000,
> +				  preemption_timeout));
>   	execution_quantum = engine->props.timeslice_duration_ms * 1000;
>   	preemption_timeout = engine->props.preempt_timeout_ms * 1000;
>   
> @@ -2463,6 +2467,10 @@ static void guc_context_policy_init_v69(struct intel_engine_cs *engine,
>   		desc->policy_flags |= CONTEXT_POLICY_FLAG_PREEMPT_TO_IDLE_V69;
>   
>   	/* NB: For both of these, zero means disabled. */
> +	GEM_BUG_ON(overflows_type(engine->props.timeslice_duration_ms * 1000,
> +				  desc->execution_quantum));
> +	GEM_BUG_ON(overflows_type(engine->props.preempt_timeout_ms * 1000,
> +				  desc->preemption_timeout));
>   	desc->execution_quantum = engine->props.timeslice_duration_ms * 1000;
>   	desc->preemption_timeout = engine->props.preempt_timeout_ms * 1000;
>   }

Re: [PATCH v5 4/4] drm/i915: Improve long running compute w/a for GuC submission

[Ceraolo Spurio, Daniele]

On 10/6/2022 2:38 PM, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
>
> A workaround was added to the driver to allow compute workloads to run
> 'forever' by disabling pre-emption on the RCS engine for Gen12.
> It is not totally unbound as the heartbeat will kick in eventually
> and cause a reset of the hung engine.
>
> However, this does not work well in GuC submission mode. In GuC mode,
> the pre-emption timeout is how GuC detects hung contexts and triggers
> a per engine reset. Thus, disabling the timeout means also losing all
> per engine reset ability. A full GT reset will still occur when the
> heartbeat finally expires, but that is a much more destructive and
> undesirable mechanism.
>
> The purpose of the workaround is actually to give compute tasks longer
> to reach a pre-emption point after a pre-emption request has been
> issued. This is necessary because Gen12 does not support mid-thread
> pre-emption and compute tasks can have long running threads.
>
> So, rather than disabling the timeout completely, just set it to a
> 'long' value.
>
> v2: Review feedback from Tvrtko - must hard code the 'long' value
> instead of determining it algorithmically. So make it an extra CONFIG
> definition. Also, remove the execlist centric comment from the
> existing pre-emption timeout CONFIG option given that it applies to
> more than just execlists.
>
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> (v1)

r-b stands.

Daniele

> Acked-by: Michal Mrozek <michal.mrozek@intel.com>
> Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/Kconfig.profile      | 26 +++++++++++++++++++----
>   drivers/gpu/drm/i915/gt/intel_engine_cs.c |  9 ++++++--
>   2 files changed, 29 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
> index 39328567c2007..7cc38d25ee5c8 100644
> --- a/drivers/gpu/drm/i915/Kconfig.profile
> +++ b/drivers/gpu/drm/i915/Kconfig.profile
> @@ -57,10 +57,28 @@ config DRM_I915_PREEMPT_TIMEOUT
>   	default 640 # milliseconds
>   	help
>   	  How long to wait (in milliseconds) for a preemption event to occur
> -	  when submitting a new context via execlists. If the current context
> -	  does not hit an arbitration point and yield to HW before the timer
> -	  expires, the HW will be reset to allow the more important context
> -	  to execute.
> +	  when submitting a new context. If the current context does not hit
> +	  an arbitration point and yield to HW before the timer expires, the
> +	  HW will be reset to allow the more important context to execute.
> +
> +	  This is adjustable via
> +	  /sys/class/drm/card?/engine/*/preempt_timeout_ms
> +
> +	  May be 0 to disable the timeout.
> +
> +	  The compiled in default may get overridden at driver probe time on
> +	  certain platforms and certain engines which will be reflected in the
> +	  sysfs control.
> +
> +config DRM_I915_PREEMPT_TIMEOUT_COMPUTE
> +	int "Preempt timeout for compute engines (ms, jiffy granularity)"
> +	default 7500 # milliseconds
> +	help
> +	  How long to wait (in milliseconds) for a preemption event to occur
> +	  when submitting a new context to a compute capable engine. If the
> +	  current context does not hit an arbitration point and yield to HW
> +	  before the timer expires, the HW will be reset to allow the more
> +	  important context to execute.
>   
>   	  This is adjustable via
>   	  /sys/class/drm/card?/engine/*/preempt_timeout_ms
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index fcbccd8d244e9..c1257723d1949 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -508,9 +508,14 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
>   	engine->props.timeslice_duration_ms =
>   		CONFIG_DRM_I915_TIMESLICE_DURATION;
>   
> -	/* Override to uninterruptible for OpenCL workloads. */
> +	/*
> +	 * Mid-thread pre-emption is not available in Gen12. Unfortunately,
> +	 * some compute workloads run quite long threads. That means they get
> +	 * reset due to not pre-empting in a timely manner. So, bump the
> +	 * pre-emption timeout value to be much higher for compute engines.
> +	 */
>   	if (GRAPHICS_VER(i915) == 12 && (engine->flags & I915_ENGINE_HAS_RCS_REG_STATE))
> -		engine->props.preempt_timeout_ms = 0;
> +		engine->props.preempt_timeout_ms = CONFIG_DRM_I915_PREEMPT_TIMEOUT_COMPUTE;
>   
>   	/* Cap properties according to any system limits */
>   #define CLAMP_PROP(field) \