[Intel-gfx] [PATCH 08/46] drm/i915/guc: Take GT PM ref when deregistering context

Matthew Brost
2021-08-03T22:12:08Z

Taking a PM reference to prevent intel_gt_wait_for_idle from short
circuiting while a deregister context H2G is in flight.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
drivers/gpu/drm/i915/gt/intel_engine_pm.h | 5 +
drivers/gpu/drm/i915/gt/intel_gt_pm.h | 13 +++
drivers/gpu/drm/i915/gt/uc/intel_guc.h | 4 +
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 99 +++++++++++++++----
4 files changed, 102 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
index 70ea46d6cfb0..17a5028ea177 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..a17bf0d4592b 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
@@ -41,6 +41,19 @@ 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)
+#define with_intel_gt_pm_async(gt, tmp) \
+ for (tmp = 1, intel_gt_pm_get(gt); tmp; \
+ intel_gt_pm_put_async(gt), tmp = 0)
+#define with_intel_gt_pm_if_awake(gt, tmp) \
+ for (tmp = intel_gt_pm_get_if_awake(gt); tmp; \
+ intel_gt_pm_put(gt), tmp = 0)
+#define with_intel_gt_pm_if_awake_async(gt, tmp) \
+ for (tmp = intel_gt_pm_get_if_awake(gt); tmp; \
+ intel_gt_pm_put_async(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 c0a12ae95ba5..72fdfa1f6ccd 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -61,6 +61,10 @@ struct intel_guc {
struct list_head guc_id_list_no_ref;
struct list_head guc_id_list_unpinned;

+ spinlock_t destroy_lock; /* protects list / worker */
+ struct list_head destroyed_contexts;
+ struct work_struct destroy_worker;
+
bool submission_supported;
bool submission_selected;

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 bfda15bf9182..262fa77b56e2 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -914,6 +914,7 @@ 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);
}
@@ -1032,6 +1033,8 @@ static void guc_flush_submissions(struct intel_guc *guc)
gse_flush_submissions(guc->gse[i]);
}

+static void guc_flush_destroyed_contexts(struct intel_guc *guc);
+
void intel_guc_submission_reset_prepare(struct intel_guc *guc)
{
int i;
@@ -1050,6 +1053,7 @@ 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
@@ -1377,6 +1381,8 @@ static void retire_worker_func(struct work_struct *w)
static int guc_lrcd_reg_init(struct intel_guc *guc);
static void guc_lrcd_reg_fini(struct intel_guc *guc);

+static void destroy_worker_func(struct work_struct *w);
+
/*
* Set up the memory resources to be shared with the GuC (via the GGTT)
* at firmware loading time.
@@ -1399,6 +1405,10 @@ int intel_guc_submission_init(struct intel_guc *guc)
INIT_LIST_HEAD(&guc->guc_id_list_unpinned);
ida_init(&guc->guc_ids);

+ spin_lock_init(&guc->destroy_lock);
+ INIT_LIST_HEAD(&guc->destroyed_contexts);
+ INIT_WORK(&guc->destroy_worker, destroy_worker_func);
+
return 0;
}

@@ -1409,6 +1419,7 @@ void intel_guc_submission_fini(struct intel_guc *guc)
if (!guc_submission_initialized(guc))
return;

+ guc_flush_destroyed_contexts(guc);
guc_lrcd_reg_fini(guc);

for (i = 0; i < GUC_SUBMIT_ENGINE_MAX; ++i) {
@@ -2351,11 +2362,29 @@ 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));
GEM_BUG_ON(ce != __get_context(guc, ce->guc_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);
+ }
+ spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+ if (unlikely(disabled)) {
+ release_guc_id(guc, ce);
+ __guc_context_destroy(ce);
+ return;
+ }
+
clr_context_registered(ce);
deregister_context(ce, ce->guc_id, true);
}
@@ -2384,12 +2413,52 @@ 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;
+
+ spin_lock_irqsave(&guc->destroy_lock, flags);
+ list_for_each_entry_safe(ce, cn,
+ &guc->destroyed_contexts, guc_id_link) {
+ list_del_init(&ce->guc_id_link);
+ release_guc_id(guc, ce);
+ __guc_context_destroy(ce);
+ }
+ spin_unlock_irqrestore(&guc->destroy_lock, flags);
+}
+
+static void deregister_destroyed_contexts(struct intel_guc *guc)
+{
+ struct intel_context *ce, *cn;
+ unsigned long flags;
+
+ spin_lock_irqsave(&guc->destroy_lock, flags);
+ list_for_each_entry_safe(ce, cn,
+ &guc->destroyed_contexts, guc_id_link) {
+ list_del_init(&ce->guc_id_link);
+ spin_unlock_irqrestore(&guc->destroy_lock, flags);
+ guc_lrc_desc_unpin(ce);
+ spin_lock_irqsave(&guc->destroy_lock, flags);
+ }
+ spin_unlock_irqrestore(&guc->destroy_lock, flags);
+}
+
+static void destroy_worker_func(struct work_struct *w)
+{
+ struct intel_guc *guc =
+ container_of(w, struct intel_guc, destroy_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;

@@ -2429,12 +2498,12 @@ static void guc_context_destroy(struct kref *kref)
list_del_init(&ce->guc_id_link);
spin_unlock_irqrestore(&guc->contexts_lock, flags);

- /* Seal race with Reset */
- spin_lock_irqsave(&ce->guc_state.lock, flags);
+ /* Seal race with reset */
+ spin_lock_irqsave(&guc->destroy_lock, flags);
disabled = submission_disabled(guc);
if (likely(!disabled))
- set_context_destroyed(ce);
- spin_unlock_irqrestore(&ce->guc_state.lock, flags);
+ list_add_tail(&ce->guc_id_link, &guc->destroyed_contexts);
+ spin_unlock_irqrestore(&guc->destroy_lock, flags);
if (unlikely(disabled)) {
release_guc_id(guc, ce);
__guc_context_destroy(ce);
@@ -2442,20 +2511,11 @@ static void guc_context_destroy(struct kref *kref)
}

/*
- * 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->destroy_worker);
}

static int guc_context_alloc(struct intel_context *ce)
@@ -3472,6 +3532,7 @@ 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);
}
--
2.28.0