[Intel-gfx] [PATCH 08/51] drm/i915/guc: Defer context unpin until scheduling is disabled

Matthew Brost
2021-07-16T20:00:01Z

With GuC scheduling, it isn't safe to unpin a context while scheduling
is enabled for that context as the GuC may touch some of the pinned
state (e.g. LRC). To ensure scheduling isn't enabled when an unpin is
done, a call back is added to intel_context_unpin when pin count == 1
to disable scheduling for that context. When the response CTB is
received it is safe to do the final unpin.

Future patches may add a heuristic / delay to schedule the disable
call back to avoid thrashing on schedule enable / disable.

Cc: John Harrison <john.c.harrison@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
---
drivers/gpu/drm/i915/gt/intel_context.c | 4 +-
drivers/gpu/drm/i915/gt/intel_context.h | 27 +++-
drivers/gpu/drm/i915/gt/intel_context_types.h | 2 +
drivers/gpu/drm/i915/gt/uc/intel_guc.h | 2 +
drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 3 +
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 147 +++++++++++++++++-
6 files changed, 181 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index ad7197c5910f..3d5b4116617f 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -306,9 +306,9 @@ int __intel_context_do_pin(struct intel_context *ce)
return err;
}

-void intel_context_unpin(struct intel_context *ce)
+void __intel_context_do_unpin(struct intel_context *ce, int sub)
{
- if (!atomic_dec_and_test(&ce->pin_count))
+ if (!atomic_sub_and_test(sub, &ce->pin_count))
return;

CE_TRACE(ce, "unpin\n");
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index b10cbe8fee99..974ef85320c2 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -113,7 +113,32 @@ static inline void __intel_context_pin(struct intel_context *ce)
atomic_inc(&ce->pin_count);
}

-void intel_context_unpin(struct intel_context *ce);
+void __intel_context_do_unpin(struct intel_context *ce, int sub);
+
+static inline void intel_context_sched_disable_unpin(struct intel_context *ce)
+{
+ __intel_context_do_unpin(ce, 2);
+}
+
+static inline void intel_context_unpin(struct intel_context *ce)
+{
+ if (!ce->ops->sched_disable) {
+ __intel_context_do_unpin(ce, 1);
+ } else {
+ /*
+ * Move ownership of this pin to the scheduling disable which is
+ * an async operation. When that operation completes the above
+ * intel_context_sched_disable_unpin is called potentially
+ * unpinning the context.
+ */
+ while (!atomic_add_unless(&ce->pin_count, -1, 1)) {
+ if (atomic_cmpxchg(&ce->pin_count, 1, 2) == 1) {
+ ce->ops->sched_disable(ce);
+ break;
+ }
+ }
+ }
+}

void intel_context_enter_engine(struct intel_context *ce);
void intel_context_exit_engine(struct intel_context *ce);
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index e0e3a937f709..4a5518d295c2 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -43,6 +43,8 @@ struct intel_context_ops {
void (*enter)(struct intel_context *ce);
void (*exit)(struct intel_context *ce);

+ void (*sched_disable)(struct intel_context *ce);
+
void (*reset)(struct intel_context *ce);
void (*destroy)(struct kref *kref);
};
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
index 30773cd699f5..03b7222b04a2 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -241,6 +241,8 @@ int intel_guc_reset_engine(struct intel_guc *guc,

int intel_guc_deregister_done_process_msg(struct intel_guc *guc,
const u32 *msg, u32 len);
+int intel_guc_sched_done_process_msg(struct intel_guc *guc,
+ const u32 *msg, u32 len);

void intel_guc_load_status(struct intel_guc *guc, struct drm_printer *p);

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
index 28ff82c5be45..019b25ff1888 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
@@ -932,6 +932,9 @@ static int ct_process_request(struct intel_guc_ct *ct, struct ct_incoming_msg *r
ret = intel_guc_deregister_done_process_msg(guc, payload,
len);
break;
+ case INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_DONE:
+ ret = intel_guc_sched_done_process_msg(guc, payload, len);
+ break;
default:
ret = -EOPNOTSUPP;
break;
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 a438aecfe93f..5519c988a6ca 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -70,6 +70,7 @@
* possible for some of the bits to changing at the same time though.
*/
#define SCHED_STATE_NO_LOCK_ENABLED BIT(0)
+#define SCHED_STATE_NO_LOCK_PENDING_ENABLE BIT(1)
static inline bool context_enabled(struct intel_context *ce)
{
return (atomic_read(&ce->guc_sched_state_no_lock) &
@@ -87,6 +88,24 @@ static inline void clr_context_enabled(struct intel_context *ce)
&ce->guc_sched_state_no_lock);
}

+static inline bool context_pending_enable(struct intel_context *ce)
+{
+ return (atomic_read(&ce->guc_sched_state_no_lock) &
+ SCHED_STATE_NO_LOCK_PENDING_ENABLE);
+}
+
+static inline void set_context_pending_enable(struct intel_context *ce)
+{
+ atomic_or(SCHED_STATE_NO_LOCK_PENDING_ENABLE,
+ &ce->guc_sched_state_no_lock);
+}
+
+static inline void clr_context_pending_enable(struct intel_context *ce)
+{
+ atomic_and((u32)~SCHED_STATE_NO_LOCK_PENDING_ENABLE,
+ &ce->guc_sched_state_no_lock);
+}
+
/*
* Below is a set of functions which control the GuC scheduling state which
* require a lock, aside from the special case where the functions are called
@@ -95,6 +114,7 @@ static inline void clr_context_enabled(struct intel_context *ce)
*/
#define SCHED_STATE_WAIT_FOR_DEREGISTER_TO_REGISTER BIT(0)
#define SCHED_STATE_DESTROYED BIT(1)
+#define SCHED_STATE_PENDING_DISABLE BIT(2)
static inline void init_sched_state(struct intel_context *ce)
{
/* Only should be called from guc_lrc_desc_pin() */
@@ -139,6 +159,24 @@ set_context_destroyed(struct intel_context *ce)
ce->guc_state.sched_state |= SCHED_STATE_DESTROYED;
}

+static inline bool context_pending_disable(struct intel_context *ce)
+{
+ return (ce->guc_state.sched_state & SCHED_STATE_PENDING_DISABLE);
+}
+
+static inline void set_context_pending_disable(struct intel_context *ce)
+{
+ lockdep_assert_held(&ce->guc_state.lock);
+ ce->guc_state.sched_state |= SCHED_STATE_PENDING_DISABLE;
+}
+
+static inline void clr_context_pending_disable(struct intel_context *ce)
+{
+ lockdep_assert_held(&ce->guc_state.lock);
+ ce->guc_state.sched_state =
+ (ce->guc_state.sched_state & ~SCHED_STATE_PENDING_DISABLE);
+}
+
static inline bool context_guc_id_invalid(struct intel_context *ce)
{
return (ce->guc_id == GUC_INVALID_LRC_ID);
@@ -231,6 +269,8 @@ static int guc_add_request(struct intel_guc *guc, struct i915_request *rq)
action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET;
action[len++] = ce->guc_id;
action[len++] = GUC_CONTEXT_ENABLE;
+ set_context_pending_enable(ce);
+ intel_context_get(ce);
} else {
action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT;
action[len++] = ce->guc_id;
@@ -238,8 +278,12 @@ static int guc_add_request(struct intel_guc *guc, struct i915_request *rq)

err = intel_guc_send_nb(guc, action, len);

- if (!enabled && !err)
+ if (!enabled && !err) {
set_context_enabled(ce);
+ } else if (!enabled) {
+ clr_context_pending_enable(ce);
+ intel_context_put(ce);
+ }

return err;
}
@@ -833,6 +877,62 @@ static void guc_context_post_unpin(struct intel_context *ce)
lrc_post_unpin(ce);
}

+static void __guc_context_sched_disable(struct intel_guc *guc,
+ struct intel_context *ce,
+ u16 guc_id)
+{
+ u32 action[] = {
+ INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET,
+ guc_id, /* ce->guc_id not stable */
+ GUC_CONTEXT_DISABLE
+ };
+
+ GEM_BUG_ON(guc_id == GUC_INVALID_LRC_ID);
+
+ intel_context_get(ce);
+
+ intel_guc_send_busy_loop(guc, action, ARRAY_SIZE(action), true);
+}
+
+static u16 prep_context_pending_disable(struct intel_context *ce)
+{
+ lockdep_assert_held(&ce->guc_state.lock);
+
+ set_context_pending_disable(ce);
+ clr_context_enabled(ce);
+
+ return ce->guc_id;
+}
+
+static void guc_context_sched_disable(struct intel_context *ce)
+{
+ struct intel_guc *guc = ce_to_guc(ce);
+ struct intel_runtime_pm *runtime_pm = &ce->engine->gt->i915->runtime_pm;
+ unsigned long flags;
+ u16 guc_id;
+ intel_wakeref_t wakeref;
+
+ if (context_guc_id_invalid(ce) ||
+ !lrc_desc_registered(guc, ce->guc_id)) {
+ clr_context_enabled(ce);
+ goto unpin;
+ }
+
+ if (!context_enabled(ce))
+ goto unpin;
+
+ spin_lock_irqsave(&ce->guc_state.lock, flags);
+ guc_id = prep_context_pending_disable(ce);
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+
+ with_intel_runtime_pm(runtime_pm, wakeref)
+ __guc_context_sched_disable(guc, ce, guc_id);
+
+ return;
+unpin:
+ intel_context_sched_disable_unpin(ce);
+}
+
static inline void guc_lrc_desc_unpin(struct intel_context *ce)
{
struct intel_engine_cs *engine = ce->engine;
@@ -841,6 +941,7 @@ static inline void guc_lrc_desc_unpin(struct intel_context *ce)

GEM_BUG_ON(!lrc_desc_registered(guc, ce->guc_id));
GEM_BUG_ON(ce != __get_context(guc, ce->guc_id));
+ GEM_BUG_ON(context_enabled(ce));

spin_lock_irqsave(&ce->guc_state.lock, flags);
set_context_destroyed(ce);
@@ -922,6 +1023,8 @@ static const struct intel_context_ops guc_context_ops = {
.enter = intel_context_enter_engine,
.exit = intel_context_exit_engine,

+ .sched_disable = guc_context_sched_disable,
+
.reset = lrc_reset,
.destroy = guc_context_destroy,
};
@@ -1354,3 +1457,45 @@ int intel_guc_deregister_done_process_msg(struct intel_guc *guc,

return 0;
}
+
+int intel_guc_sched_done_process_msg(struct intel_guc *guc,
+ const u32 *msg,
+ u32 len)
+{
+ struct intel_context *ce;
+ unsigned long flags;
+ u32 desc_idx = msg[0];
+
+ if (unlikely(len < 2)) {
+ drm_dbg(&guc_to_gt(guc)->i915->drm, "Invalid length %u", len);
+ return -EPROTO;
+ }
+
+ ce = g2h_context_lookup(guc, desc_idx);
+ if (unlikely(!ce))
+ return -EPROTO;
+
+ if (unlikely(context_destroyed(ce) ||
+ (!context_pending_enable(ce) &&
+ !context_pending_disable(ce)))) {
+ drm_dbg(&guc_to_gt(guc)->i915->drm,
+ "Bad context sched_state 0x%x, 0x%x, desc_idx %u",
+ atomic_read(&ce->guc_sched_state_no_lock),
+ ce->guc_state.sched_state, desc_idx);
+ return -EPROTO;
+ }
+
+ if (context_pending_enable(ce)) {
+ clr_context_pending_enable(ce);
+ } else if (context_pending_disable(ce)) {
+ intel_context_sched_disable_unpin(ce);
+
+ spin_lock_irqsave(&ce->guc_state.lock, flags);
+ clr_context_pending_disable(ce);
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+ }
+
+ intel_context_put(ce);
+
+ return 0;
+}
--
2.28.0