[Intel-gfx] [RFC 1/6] drm/i915/pmu: Fix enable count array size and bounds checking

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Enable count array is supposed to have one counter for each possible
engine sampler. As such array sizing and bounds checking is not
correct when more engine samplers are added.

At the same time tidy the assert for readability and robustness.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Fixes: b46a33e271ed ("drm/i915/pmu: Expose a PMU interface for perf queries")
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_pmu.c         | 13 +++++++++----
 drivers/gpu/drm/i915/intel_ringbuffer.h |  2 +-
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 065a28c713c4..cbfca4a255ab 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -476,7 +476,8 @@ static void i915_pmu_enable(struct perf_event *event)
 	 * Update the bitmask of enabled events and increment
 	 * the event reference counter.
 	 */
-	GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
+	BUILD_BUG_ON(ARRAY_SIZE(i915->pmu.enable_count) != I915_PMU_MASK_BITS);
+	GEM_BUG_ON(bit >= ARRAY_SIZE(i915->pmu.enable_count));
 	GEM_BUG_ON(i915->pmu.enable_count[bit] == ~0);
 	i915->pmu.enable |= BIT_ULL(bit);
 	i915->pmu.enable_count[bit]++;
@@ -500,7 +501,10 @@ static void i915_pmu_enable(struct perf_event *event)
 		GEM_BUG_ON(!engine);
 		engine->pmu.enable |= BIT(sample);
 
-		GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
+		BUILD_BUG_ON(ARRAY_SIZE(engine->pmu.enable_count) !=
+			     (1 << I915_PMU_SAMPLE_BITS));
+		GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.enable_count));
+		GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.sample));
 		GEM_BUG_ON(engine->pmu.enable_count[sample] == ~0);
 		if (engine->pmu.enable_count[sample]++ == 0) {
 			/*
@@ -554,7 +558,8 @@ static void i915_pmu_disable(struct perf_event *event)
 						  engine_event_class(event),
 						  engine_event_instance(event));
 		GEM_BUG_ON(!engine);
-		GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
+		GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.enable_count));
+		GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.sample));
 		GEM_BUG_ON(engine->pmu.enable_count[sample] == 0);
 		/*
 		 * Decrement the reference count and clear the enabled
@@ -582,7 +587,7 @@ static void i915_pmu_disable(struct perf_event *event)
 		}
 	}
 
-	GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
+	GEM_BUG_ON(bit >= ARRAY_SIZE(i915->pmu.enable_count));
 	GEM_BUG_ON(i915->pmu.enable_count[bit] == 0);
 	/*
 	 * Decrement the reference count and clear the enabled
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index c5ff203e42d6..27a0c47db51e 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -358,7 +358,7 @@ struct intel_engine_cs {
 		 *
 		 * Index number corresponds to the bit number from @enable.
 		 */
-		unsigned int enable_count[I915_PMU_SAMPLE_BITS];
+		unsigned int enable_count[1 << I915_PMU_SAMPLE_BITS];
 		/**
 		 * @sample: Counter values for sampling events.
 		 *
-- 
2.14.1