Re: [PATCH 43/51] drm/i915/guc: Support request cancellation

On 7/16/2021 1:17 PM, Matthew Brost wrote:

This adds GuC backend support for i915_request_cancel(), which in turn makes CONFIG_DRM_I915_REQUEST_TIMEOUT work.

This needs a bit of explanation on why we're using fences for this instead of other simpler options.

Signed-off-by: Matthew Brost matthew.brost@intel.com Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com

---

drivers/gpu/drm/i915/gt/intel_context.c | 9 + drivers/gpu/drm/i915/gt/intel_context.h | 7 + drivers/gpu/drm/i915/gt/intel_context_types.h | 7 + .../drm/i915/gt/intel_execlists_submission.c | 18 ++ .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 169 ++++++++++++++++++ drivers/gpu/drm/i915/i915_request.c | 14 +- 6 files changed, 211 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c index dd078a80c3a3..b1e3d00fb1f2 100644 --- a/drivers/gpu/drm/i915/gt/intel_context.c +++ b/drivers/gpu/drm/i915/gt/intel_context.c @@ -366,6 +366,12 @@ static int __intel_context_active(struct i915_active *active) return 0; }

+static int sw_fence_dummy_notify(struct i915_sw_fence *sf,

• 		 enum i915_sw_fence_notify state)
  

+{

• return NOTIFY_DONE;

+}

• void intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine) {

@@ -399,6 +405,9 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine) ce->guc_id = GUC_INVALID_LRC_ID; INIT_LIST_HEAD(&ce->guc_id_link);

• i915_sw_fence_init(&ce->guc_blocked, sw_fence_dummy_notify);
• i915_sw_fence_commit(&ce->guc_blocked);

We need a comment somewhere to explain how we use this blocked fence, I.e. that fence starts signaled to indicate unblocked and we re-init it to unsignaled status when we need to mark something as blocked.

• i915_active_init(&ce->active, __intel_context_active, __intel_context_retire, 0); }

diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h index 814d9277096a..876bdb08303c 100644 --- a/drivers/gpu/drm/i915/gt/intel_context.h +++ b/drivers/gpu/drm/i915/gt/intel_context.h @@ -70,6 +70,13 @@ intel_context_is_pinned(struct intel_context *ce) return atomic_read(&ce->pin_count); }

+static inline void intel_context_cancel_request(struct intel_context *ce,

• 				struct i915_request *rq)
  

+{

• GEM_BUG_ON(!ce->ops->cancel_request);
• return ce->ops->cancel_request(ce, rq);

+}

• /**
  • intel_context_unlock_pinned - Releases the earlier locking of 'pinned' status
  • @ce - the context

diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h index 57c19ee3e313..005a64f2afa7 100644 --- a/drivers/gpu/drm/i915/gt/intel_context_types.h +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h @@ -13,6 +13,7 @@ #include <linux/types.h>

#include "i915_active_types.h" +#include "i915_sw_fence.h" #include "i915_utils.h" #include "intel_engine_types.h" #include "intel_sseu.h" @@ -42,6 +43,9 @@ struct intel_context_ops { void (*unpin)(struct intel_context *ce); void (*post_unpin)(struct intel_context *ce);

• void (*cancel_request)(struct intel_context *ce,

• 	       struct i915_request *rq);
  

I don't see an implementation for this for the ringbuffer backend.

• void (*enter)(struct intel_context *ce); void (*exit)(struct intel_context *ce);

@@ -184,6 +188,9 @@ struct intel_context { * GuC ID link - in list when unpinned but guc_id still valid in GuC */ struct list_head guc_id_link;

• /* GuC context blocked fence */

• struct i915_sw_fence guc_blocked; };

  #endif /* __INTEL_CONTEXT_TYPES__ */

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c index f9b5f54a5abe..8f6dc0fb49a6 100644 --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c @@ -114,6 +114,7 @@ #include "gen8_engine_cs.h" #include "intel_breadcrumbs.h" #include "intel_context.h" +#include "intel_engine_heartbeat.h" #include "intel_engine_pm.h" #include "intel_engine_stats.h" #include "intel_execlists_submission.h" @@ -2536,11 +2537,26 @@ static int execlists_context_alloc(struct intel_context *ce) return lrc_alloc(ce, ce->engine); }

+static void execlists_context_cancel_request(struct intel_context *ce,

• 			     struct i915_request *rq)
  

+{

• struct intel_engine_cs *engine = NULL;
• i915_request_active_engine(rq, &engine);
• if (engine && intel_engine_pulse(engine))

• intel_gt_handle_error(engine->gt, engine->mask, 0,
  

• 		      "request cancellation by %s",
  

• 		      current->comm);
  

+}

• static const struct intel_context_ops execlists_context_ops = { .flags = COPS_HAS_INFLIGHT,

  .alloc = execlists_context_alloc,

• .cancel_request = execlists_context_cancel_request,

• .pre_pin = execlists_context_pre_pin, .pin = execlists_context_pin, .unpin = lrc_unpin,

@@ -3558,6 +3574,8 @@ static const struct intel_context_ops virtual_context_ops = {

.alloc = virtual_context_alloc,

• .cancel_request = execlists_context_cancel_request,
• .pre_pin = virtual_context_pre_pin, .pin = virtual_context_pin, .unpin = lrc_unpin,

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 149990196e3a..1c30d04733ff 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -81,6 +81,11 @@ guc_create_virtual(struct intel_engine_cs **siblings, unsigned int count); */ #define SCHED_STATE_NO_LOCK_ENABLED BIT(0) #define SCHED_STATE_NO_LOCK_PENDING_ENABLE BIT(1) +#define SCHED_STATE_NO_LOCK_BLOCKED_SHIFT 2 +#define SCHED_STATE_NO_LOCK_BLOCKED \

• BIT(SCHED_STATE_NO_LOCK_BLOCKED_SHIFT)

+#define SCHED_STATE_NO_LOCK_BLOCKED_MASK \

• (0xffff << SCHED_STATE_NO_LOCK_BLOCKED_SHIFT) static inline bool context_enabled(struct intel_context *ce) { return (atomic_read(&ce->guc_sched_state_no_lock) &

@@ -116,6 +121,27 @@ static inline void clr_context_pending_enable(struct intel_context *ce) &ce->guc_sched_state_no_lock); }

+static inline u32 context_blocked(struct intel_context *ce) +{

• return (atomic_read(&ce->guc_sched_state_no_lock) &

• SCHED_STATE_NO_LOCK_BLOCKED_MASK) >>
  

• SCHED_STATE_NO_LOCK_BLOCKED_SHIFT;
  

+}

+static inline void incr_context_blocked(struct intel_context *ce) +{

• lockdep_assert_held(&ce->engine->sched_engine->lock);

It's a bit weird requiring a lock for a variable that is purposely called no_lock, but I do get it is not the GuC lock. Can you explain which race you're trying to guard against?

• atomic_add(SCHED_STATE_NO_LOCK_BLOCKED,

•    &ce->guc_sched_state_no_lock);
  

Do we need an overflow check, or are we guaranteed that the count will stay within a certain range?

+}

+static inline void decr_context_blocked(struct intel_context *ce) +{

• lockdep_assert_held(&ce->engine->sched_engine->lock);

GEM_BUG_ON(!context_blocked(ce)) ?

• atomic_sub(SCHED_STATE_NO_LOCK_BLOCKED,

•    &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

@@ -403,6 +429,10 @@ static int guc_add_request(struct intel_guc *guc, struct i915_request *rq) if (unlikely(err)) goto out; }

• if (unlikely(context_blocked(ce)))

• goto out;
  

You're not setting any error state here for this aborted request. Will the request be automatically re-submitted on unblock? could use a comment if that's the case.

• enabled = context_enabled(ce);

  if (!enabled) {

@@ -531,6 +561,7 @@ static void __guc_context_destroy(struct intel_context *ce); static void release_guc_id(struct intel_guc *guc, struct intel_context *ce); static void guc_signal_context_fence(struct intel_context *ce); static void guc_cancel_context_requests(struct intel_context *ce); +static void guc_blocked_fence_complete(struct intel_context *ce);

static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc) { @@ -578,6 +609,10 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc) } intel_context_sched_disable_unpin(ce); atomic_dec(&guc->outstanding_submission_g2h);

• 	spin_lock_irqsave(&ce->guc_state.lock, flags);
  

• 	guc_blocked_fence_complete(ce);
  

• 	spin_unlock_irqrestore(&ce->guc_state.lock, flags);
  

• intel_context_put(ce);
  

  } }

@@ -1339,6 +1374,21 @@ static void guc_context_post_unpin(struct intel_context *ce) lrc_post_unpin(ce); }

+static void __guc_context_sched_enable(struct intel_guc *guc,

Why void? this can fail

• 		       struct intel_context *ce)
  

+{

• u32 action[] = {

• INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET,
  

• ce->guc_id,
  

• GUC_CONTEXT_ENABLE
  

• };
• trace_intel_context_sched_enable(ce);
• guc_submission_send_busy_loop(guc, action, ARRAY_SIZE(action),

• 		      G2H_LEN_DW_SCHED_CONTEXT_MODE_SET, true);
  

+}

• static void __guc_context_sched_disable(struct intel_guc *guc, struct intel_context *ce, u16 guc_id)

@@ -1357,17 +1407,131 @@ static void __guc_context_sched_disable(struct intel_guc *guc, G2H_LEN_DW_SCHED_CONTEXT_MODE_SET, true); }

+static void guc_blocked_fence_complete(struct intel_context *ce) +{

• lockdep_assert_held(&ce->guc_state.lock);
• if (!i915_sw_fence_done(&ce->guc_blocked))

• i915_sw_fence_complete(&ce->guc_blocked);
  

+}

+static void guc_blocked_fence_reinit(struct intel_context *ce) +{

• lockdep_assert_held(&ce->guc_state.lock);
• GEM_BUG_ON(!i915_sw_fence_done(&ce->guc_blocked));
• i915_sw_fence_fini(&ce->guc_blocked);
• i915_sw_fence_reinit(&ce->guc_blocked);
• i915_sw_fence_await(&ce->guc_blocked);
• i915_sw_fence_commit(&ce->guc_blocked);

+}

• 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);

• guc_blocked_fence_reinit(ce); intel_context_get(ce);

  return ce->guc_id; }

+static struct i915_sw_fence *guc_context_block(struct intel_context *ce) +{

• struct intel_guc *guc = ce_to_guc(ce);
• struct i915_sched_engine *sched_engine = ce->engine->sched_engine;
• unsigned long flags;
• struct intel_runtime_pm *runtime_pm = &ce->engine->gt->i915->runtime_pm;

engine->uncore->rpm

• intel_wakeref_t wakeref;
• u16 guc_id;
• bool enabled;
• spin_lock_irqsave(&sched_engine->lock, flags);
• incr_context_blocked(ce);
• spin_unlock_irqrestore(&sched_engine->lock, flags);
• spin_lock_irqsave(&ce->guc_state.lock, flags);
• enabled = context_enabled(ce);
• if (unlikely(!enabled || submission_disabled(guc))) {

• if (enabled)
  

• 	clr_context_enabled(ce);
  

• spin_unlock_irqrestore(&ce->guc_state.lock, flags);
  

• return &ce->guc_blocked;
  

• }
• /*

• * We add +2 here as the schedule disable complete CTB handler calls
  

• * intel_context_sched_disable_unpin (-2 to pin_count).
  

• */
  

• atomic_add(2, &ce->pin_count);
• 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 &ce->guc_blocked;

+}

+static void guc_context_unblock(struct intel_context *ce) +{

• struct intel_guc *guc = ce_to_guc(ce);
• struct i915_sched_engine *sched_engine = ce->engine->sched_engine;
• unsigned long flags;
• struct intel_runtime_pm *runtime_pm = &ce->engine->gt->i915->runtime_pm;

engine->uncore->rpm

• intel_wakeref_t wakeref;
• GEM_BUG_ON(context_enabled(ce));
• if (unlikely(context_blocked(ce) > 1)) {

• spin_lock_irqsave(&sched_engine->lock, flags);
  

• if (likely(context_blocked(ce) > 1))
  

• 	goto decrement;
  

• spin_unlock_irqrestore(&sched_engine->lock, flags);
  

• }
• spin_lock_irqsave(&ce->guc_state.lock, flags);
• if (unlikely(submission_disabled(guc) ||

•      !intel_context_is_pinned(ce) ||
  

•      context_pending_disable(ce) ||
  

•      context_blocked(ce) > 1)) {
  

you've already checked context_blocked > 1 twice above. If you can't trust the value to remain stable, maybe keep the spinlock locked for more of the flow?

• spin_unlock_irqrestore(&ce->guc_state.lock, flags);
  

• goto out;
  

• }
• set_context_pending_enable(ce);
• set_context_enabled(ce);

Shouldn't we set this to enabled only after the H2G has succeeded?

Daniele

• intel_context_get(ce);
• spin_unlock_irqrestore(&ce->guc_state.lock, flags);
• with_intel_runtime_pm(runtime_pm, wakeref)

• __guc_context_sched_enable(guc, ce);
  

+out:

• spin_lock_irqsave(&sched_engine->lock, flags);

+decrement:

• decr_context_blocked(ce);
• spin_unlock_irqrestore(&sched_engine->lock, flags);

+}

+static void guc_context_cancel_request(struct intel_context *ce,

• 		       struct i915_request *rq)
  

+{

• if (i915_sw_fence_signaled(&rq->submit)) {

• struct i915_sw_fence *fence = guc_context_block(ce);
  

• i915_sw_fence_wait(fence);
  

• if (!i915_request_completed(rq)) {
  

• 	__i915_request_skip(rq);
  

• 	guc_reset_state(ce, intel_ring_wrap(ce->ring, rq->head),
  

• 			true);
  

• }
  

• guc_context_unblock(ce);
  

• }

+}

• static void __guc_context_set_preemption_timeout(struct intel_guc *guc, u16 guc_id, u32 preemption_timeout)

@@ -1626,6 +1790,8 @@ static const struct intel_context_ops guc_context_ops = {

.ban = guc_context_ban,

• .cancel_request = guc_context_cancel_request,
• .enter = intel_context_enter_engine, .exit = intel_context_exit_engine,

@@ -1821,6 +1987,8 @@ static const struct intel_context_ops virtual_guc_context_ops = {

.ban = guc_context_ban,

• .cancel_request = guc_context_cancel_request,
• .enter = guc_virtual_context_enter, .exit = guc_virtual_context_exit,

@@ -2290,6 +2458,7 @@ int intel_guc_sched_done_process_msg(struct intel_guc *guc, clr_context_banned(ce); clr_context_pending_disable(ce); __guc_signal_context_fence(ce);

• guc_blocked_fence_complete(ce);
  

  spin_unlock_irqrestore(&ce->guc_state.lock, flags);

  if (banned) {

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index eb109f93ebcb..f3552642b8a1 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -708,18 +708,6 @@ void i915_request_unsubmit(struct i915_request *request) spin_unlock_irqrestore(&engine->sched_engine->lock, flags); }

-static void __cancel_request(struct i915_request *rq) -{

• struct intel_engine_cs *engine = NULL;
• i915_request_active_engine(rq, &engine);
• if (engine && intel_engine_pulse(engine))

• intel_gt_handle_error(engine->gt, engine->mask, 0,
  

• 		      "request cancellation by %s",
  

• 		      current->comm);
  

-}

• void i915_request_cancel(struct i915_request *rq, int error) { if (!i915_request_set_error_once(rq, error))

@@ -727,7 +715,7 @@ void i915_request_cancel(struct i915_request *rq, int error)

set_bit(I915_FENCE_FLAG_SENTINEL, &rq->fence.flags);

• __cancel_request(rq);

• intel_context_cancel_request(rq->context, rq); }

  static int __i915_sw_fence_call