[Intel-gfx] [PATCH 02/25] drm/i915/guc: Take GT PM ref when deregistering context

Matthew Brost
2021-10-14T17:44:53Z

Taking a PM reference to prevent intel_gt_wait_for_idle from short
circuiting while a deregister context H2G is in flight. To do this must
issue the deregister H2G from a worker as context can be destroyed from
an atomic context and taking GT PM ref blows up. Previously we took a
runtime PM from this atomic context which worked but will stop working
once runtime pm autosuspend in enabled.

So this patch is two fold, stop intel_gt_wait_for_idle from short
circuting and fix runtime pm autosuspend.

v2:
(John Harrison)
- Split structure changes out in different patch
(Tvrtko)
- Don't drop lock in deregister_destroyed_contexts
v3:
(John Harrison)
- Flush destroyed contexts before destroying context reg pool

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 | 2 +
drivers/gpu/drm/i915/gt/intel_context_types.h | 7 +
drivers/gpu/drm/i915/gt/intel_engine_pm.h | 5 +
drivers/gpu/drm/i915/gt/intel_gt_pm.h | 4 +
drivers/gpu/drm/i915/gt/uc/intel_guc.h | 11 ++
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 146 +++++++++++-------
6 files changed, 121 insertions(+), 54 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 35babd02ddfe..d008ef8623ce 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -400,6 +400,8 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
ce->guc_id.id = GUC_INVALID_LRC_ID;
INIT_LIST_HEAD(&ce->guc_id.link);

+ INIT_LIST_HEAD(&ce->destroyed_link);
+
/*
* Initialize fence to be complete as this is expected to be complete
* unless there is a pending schedule disable outstanding.
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index e7e3984aab78..4613d027cbc3 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -213,6 +213,13 @@ struct intel_context {
struct list_head link;
} guc_id;

+ /**
+ * @destroyed_link: link in guc->submission_state.destroyed_contexts, in
+ * list when context is pending to be destroyed (deregistered with the
+ * GuC), protected by guc->submission_state.lock
+ */
+ struct list_head destroyed_link;
+
#ifdef CONFIG_DRM_I915_SELFTEST
/**
* @drop_schedule_enable: Force drop of schedule enable G2H for selftest
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
index 8520c595f5e1..6fdeae668e6e 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
@@ -16,6 +16,11 @@ intel_engine_pm_is_awake(const struct intel_engine_cs *engine)
return intel_wakeref_is_active(&engine->wakeref);
}

+static inline void __intel_engine_pm_get(struct intel_engine_cs *engine)
+{
+ __intel_wakeref_get(&engine->wakeref);
+}
+
static inline void intel_engine_pm_get(struct intel_engine_cs *engine)
{
intel_wakeref_get(&engine->wakeref);
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
index d0588d8aaa44..05de6c1af25b 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
@@ -41,6 +41,10 @@ static inline void intel_gt_pm_put_async(struct intel_gt *gt)
intel_wakeref_put_async(&gt->wakeref);
}

+#define with_intel_gt_pm(gt, tmp) \
+ for (tmp = 1, intel_gt_pm_get(gt); tmp; \
+ intel_gt_pm_put(gt), tmp = 0)
+
static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
{
return intel_wakeref_wait_for_idle(&gt->wakeref);
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
index 82e248c2290c..74f071a0b6d5 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -90,6 +90,17 @@ struct intel_guc {
* refs
*/
struct list_head guc_id_list;
+ /**
+ * @destroyed_contexts: list of contexts waiting to be destroyed
+ * (deregistered with the GuC)
+ */
+ struct list_head destroyed_contexts;
+ /**
+ * @destroyed_worker: worker to deregister contexts, need as we
+ * need to take a GT PM reference and can't from destroy
+ * function as it might be in an atomic context (no sleeping)
+ */
+ struct work_struct destroyed_worker;
} submission_state;

/**
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 48bdcdb823b3..5c53428032b5 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -90,8 +90,8 @@
* used for all of GuC submission but that could change in the future.
*
* guc->submission_state.lock
- * Protects guc_id allocation for the given GuC, i.e. only one context can be
- * doing guc_id allocation operations at a time for each GuC in the system.
+ * Global lock for GuC submission state. Protects guc_ids and destroyed contexts
+ * list.
*
* ce->guc_state.lock
* Protects everything under ce->guc_state. Ensures that a context is in the
@@ -719,6 +719,7 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
if (deregister)
guc_signal_context_fence(ce);
if (destroyed) {
+ intel_gt_pm_put_async(guc_to_gt(guc));
release_guc_id(guc, ce);
__guc_context_destroy(ce);
}
@@ -797,6 +798,8 @@ static void guc_flush_submissions(struct intel_guc *guc)
spin_unlock_irqrestore(&sched_engine->lock, flags);
}

+static void guc_flush_destroyed_contexts(struct intel_guc *guc);
+
void intel_guc_submission_reset_prepare(struct intel_guc *guc)
{
int i;
@@ -815,6 +818,7 @@ void intel_guc_submission_reset_prepare(struct intel_guc *guc)
spin_unlock_irq(&guc_to_gt(guc)->irq_lock);

guc_flush_submissions(guc);
+ guc_flush_destroyed_contexts(guc);

/*
* Handle any outstanding G2Hs before reset. Call IRQ handler directly
@@ -1126,6 +1130,8 @@ void intel_guc_submission_reset_finish(struct intel_guc *guc)
intel_gt_unpark_heartbeats(guc_to_gt(guc));
}

+static void destroyed_worker_func(struct work_struct *w);
+
/*
* Set up the memory resources to be shared with the GuC (via the GGTT)
* at firmware loading time.
@@ -1151,6 +1157,9 @@ int intel_guc_submission_init(struct intel_guc *guc)
spin_lock_init(&guc->submission_state.lock);
INIT_LIST_HEAD(&guc->submission_state.guc_id_list);
ida_init(&guc->submission_state.guc_ids);
+ INIT_LIST_HEAD(&guc->submission_state.destroyed_contexts);
+ INIT_WORK(&guc->submission_state.destroyed_worker,
+ destroyed_worker_func);

return 0;
}
@@ -1160,6 +1169,7 @@ void intel_guc_submission_fini(struct intel_guc *guc)
if (!guc->lrc_desc_pool)
return;

+ guc_flush_destroyed_contexts(guc);
guc_lrc_desc_pool_destroy(guc);
i915_sched_engine_put(guc->sched_engine);
}
@@ -1859,11 +1869,30 @@ static void guc_context_sched_disable(struct intel_context *ce)
static inline void guc_lrc_desc_unpin(struct intel_context *ce)
{
struct intel_guc *guc = ce_to_guc(ce);
+ struct intel_gt *gt = guc_to_gt(guc);
+ unsigned long flags;
+ bool disabled;

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

+ /* Seal race with Reset */
+ spin_lock_irqsave(&ce->guc_state.lock, flags);
+ disabled = submission_disabled(guc);
+ if (likely(!disabled)) {
+ __intel_gt_pm_get(gt);
+ set_context_destroyed(ce);
+ clr_context_registered(ce);
+ }
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+ if (unlikely(disabled)) {
+ release_guc_id(guc, ce);
+ __guc_context_destroy(ce);
+ return;
+ }
+
deregister_context(ce, ce->guc_id.id);
}

@@ -1891,78 +1920,86 @@ static void __guc_context_destroy(struct intel_context *ce)
}
}

+static void guc_flush_destroyed_contexts(struct intel_guc *guc)
+{
+ struct intel_context *ce, *cn;
+ unsigned long flags;
+
+ GEM_BUG_ON(!submission_disabled(guc) &&
+ guc_submission_initialized(guc));
+
+ spin_lock_irqsave(&guc->submission_state.lock, flags);
+ list_for_each_entry_safe(ce, cn,
+ &guc->submission_state.destroyed_contexts,
+ destroyed_link) {
+ list_del_init(&ce->destroyed_link);
+ __release_guc_id(guc, ce);
+ __guc_context_destroy(ce);
+ }
+ spin_unlock_irqrestore(&guc->submission_state.lock, flags);
+}
+
+static void deregister_destroyed_contexts(struct intel_guc *guc)
+{
+ struct intel_context *ce, *cn;
+ unsigned long flags;
+
+ spin_lock_irqsave(&guc->submission_state.lock, flags);
+ list_for_each_entry_safe(ce, cn,
+ &guc->submission_state.destroyed_contexts,
+ destroyed_link) {
+ list_del_init(&ce->destroyed_link);
+ guc_lrc_desc_unpin(ce);
+ }
+ spin_unlock_irqrestore(&guc->submission_state.lock, flags);
+}
+
+static void destroyed_worker_func(struct work_struct *w)
+{
+ struct intel_guc *guc = container_of(w, struct intel_guc,
+ submission_state.destroyed_worker);
+ struct intel_gt *gt = guc_to_gt(guc);
+ int tmp;
+
+ with_intel_gt_pm(gt, tmp)
+ deregister_destroyed_contexts(guc);
+}
+
static void guc_context_destroy(struct kref *kref)
{
struct intel_context *ce = container_of(kref, typeof(*ce), ref);
- struct intel_runtime_pm *runtime_pm = ce->engine->uncore->rpm;
struct intel_guc *guc = ce_to_guc(ce);
- intel_wakeref_t wakeref;
unsigned long flags;
- bool disabled;
+ bool destroy;

/*
* If the guc_id is invalid this context has been stolen and we can free
* it immediately. Also can be freed immediately if the context is not
* registered with the GuC or the GuC is in the middle of a reset.
*/
- if (context_guc_id_invalid(ce)) {
- __guc_context_destroy(ce);
- return;
- } else if (submission_disabled(guc) ||
- !lrc_desc_registered(guc, ce->guc_id.id)) {
- release_guc_id(guc, ce);
- __guc_context_destroy(ce);
- return;
- }
-
- /*
- * We have to acquire the context spinlock and check guc_id again, if it
- * is valid it hasn't been stolen and needs to be deregistered. We
- * delete this context from the list of unpinned guc_id available to
- * steal to seal a race with guc_lrc_desc_pin(). When the G2H CTB
- * returns indicating this context has been deregistered the guc_id is
- * returned to the pool of available guc_id.
- */
spin_lock_irqsave(&guc->submission_state.lock, flags);
- if (context_guc_id_invalid(ce)) {
- spin_unlock_irqrestore(&guc->submission_state.lock, flags);
- __guc_context_destroy(ce);
- return;
+ destroy = submission_disabled(guc) || context_guc_id_invalid(ce) ||
+ !lrc_desc_registered(guc, ce->guc_id.id);
+ if (likely(!destroy)) {
+ if (!list_empty(&ce->guc_id.link))
+ list_del_init(&ce->guc_id.link);
+ list_add_tail(&ce->destroyed_link,
+ &guc->submission_state.destroyed_contexts);
+ } else {
+ __release_guc_id(guc, ce);
}
-
- if (!list_empty(&ce->guc_id.link))
- list_del_init(&ce->guc_id.link);
spin_unlock_irqrestore(&guc->submission_state.lock, flags);
-
- /* Seal race with Reset */
- spin_lock_irqsave(&ce->guc_state.lock, flags);
- disabled = submission_disabled(guc);
- if (likely(!disabled)) {
- set_context_destroyed(ce);
- clr_context_registered(ce);
- }
- spin_unlock_irqrestore(&ce->guc_state.lock, flags);
- if (unlikely(disabled)) {
- release_guc_id(guc, ce);
+ if (unlikely(destroy)) {
__guc_context_destroy(ce);
return;
}

/*
- * We defer GuC context deregistration until the context is destroyed
- * in order to save on CTBs. With this optimization ideally we only need
- * 1 CTB to register the context during the first pin and 1 CTB to
- * deregister the context when the context is destroyed. Without this
- * optimization, a CTB would be needed every pin & unpin.
- *
- * XXX: Need to acqiure the runtime wakeref as this can be triggered
- * from context_free_worker when runtime wakeref is not held.
- * guc_lrc_desc_unpin requires the runtime as a GuC register is written
- * in H2G CTB to deregister the context. A future patch may defer this
- * H2G CTB if the runtime wakeref is zero.
+ * We use a worker to issue the H2G to deregister the context as we can
+ * take the GT PM for the first time which isn't allowed from an atomic
+ * context.
*/
- with_intel_runtime_pm(runtime_pm, wakeref)
- guc_lrc_desc_unpin(ce);
+ queue_work(system_unbound_wq, &guc->submission_state.destroyed_worker);
}

static int guc_context_alloc(struct intel_context *ce)
@@ -2798,6 +2835,7 @@ int intel_guc_deregister_done_process_msg(struct intel_guc *guc,
intel_context_put(ce);
} else if (context_destroyed(ce)) {
/* Context has been destroyed */
+ intel_gt_pm_put_async(guc_to_gt(guc));
release_guc_id(guc, ce);
__guc_context_destroy(ce);
}
--
2.32.0