drm/i915/perf: fix ctx_id read with GuC & ICL

One thing we didn't really understand about the OA report is that the
ContextID field (dword 2) is copy of the context descriptor (dword 1).

On Gen8->10 and without using GuC we didn't notice the issue because
we only checked the 21bits of the ContextID field in the OA reports
which matches exactly the hw_id stored into the context descriptor.

When using GuC submission we have an issue of a non matching hw_id
because GuC uses bit 20 of the hw_id to signal proxy submission. This
change introduces a mask to compare only the relevant bits.

On ICL the context descriptor format has changed and we failed to
address this. On top of using a mask we also need to shift the bits
properly.

v2: Reuse lrc_desc rather than recomputing part of it (Chris/Michel)

v3: Always pin the context we're filtering with (Chris)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 1de401c08fa805 ("drm/i915/perf: enable perf support on ICL")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104252
BSpec: 1237
Testcase: igt/perf/gen8-unprivileged-single-ctx-counters
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180602112946.30803-3-lionel.g.landwerlin@intel.com
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org

drivers/gpu/drm/i915/i915_drv.h

@@ -1951,6 +1951,7 @@ struct drm_i915_private {
 
 			struct intel_context *pinned_ctx;
 			u32 specific_ctx_id;
+			u32 specific_ctx_id_mask;
 
 			struct hrtimer poll_check_timer;
 			wait_queue_head_t poll_wq;

drivers/gpu/drm/i915/i915_perf.c

@@ -737,12 +737,7 @@ static int gen8_append_oa_reports(struct i915_perf_stream *stream,
 			continue;
 		}
 
-		/*
-		 * XXX: Just keep the lower 21 bits for now since I'm not
-		 * entirely sure if the HW touches any of the higher bits in
-		 * this field
-		 */
-		ctx_id = report32[2] & 0x1fffff;
+		ctx_id = report32[2] & dev_priv->perf.oa.specific_ctx_id_mask;
 
 		/*
 		 * Squash whatever is in the CTX_ID field if it's marked as
@@ -1203,6 +1198,33 @@ static int i915_oa_read(struct i915_perf_stream *stream,
 	return dev_priv->perf.oa.ops.read(stream, buf, count, offset);
 }
 
+static struct intel_context *oa_pin_context(struct drm_i915_private *i915,
+					    struct i915_gem_context *ctx)
+{
+	struct intel_engine_cs *engine = i915->engine[RCS];
+	struct intel_context *ce;
+	int ret;
+
+	ret = i915_mutex_lock_interruptible(&i915->drm);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/*
+	 * As the ID is the gtt offset of the context's vma we
+	 * pin the vma to ensure the ID remains fixed.
+	 *
+	 * NB: implied RCS engine...
+	 */
+	ce = intel_context_pin(ctx, engine);
+	mutex_unlock(&i915->drm.struct_mutex);
+	if (IS_ERR(ce))
+		return ce;
+
+	i915->perf.oa.pinned_ctx = ce;
+
+	return ce;
+}
+
 /**
  * oa_get_render_ctx_id - determine and hold ctx hw id
  * @stream: An i915-perf stream opened for OA metrics
@@ -1215,40 +1237,76 @@ static int i915_oa_read(struct i915_perf_stream *stream,
  */
 static int oa_get_render_ctx_id(struct i915_perf_stream *stream)
 {
-	struct drm_i915_private *dev_priv = stream->dev_priv;
-
-	if (HAS_LOGICAL_RING_CONTEXTS(dev_priv)) {
-		dev_priv->perf.oa.specific_ctx_id = stream->ctx->hw_id;
-	} else {
-		struct intel_engine_cs *engine = dev_priv->engine[RCS];
-		struct intel_context *ce;
-		int ret;
+	struct drm_i915_private *i915 = stream->dev_priv;
+	struct intel_context *ce;
 
-		ret = i915_mutex_lock_interruptible(&dev_priv->drm);
-		if (ret)
-			return ret;
+	ce = oa_pin_context(i915, stream->ctx);
+	if (IS_ERR(ce))
+		return PTR_ERR(ce);
 
+	switch (INTEL_GEN(i915)) {
+	case 7: {
 		/*
-		 * As the ID is the gtt offset of the context's vma we
-		 * pin the vma to ensure the ID remains fixed.
-		 *
-		 * NB: implied RCS engine...
+		 * On Haswell we don't do any post processing of the reports
+		 * and don't need to use the mask.
 		 */
-		ce = intel_context_pin(stream->ctx, engine);
-		mutex_unlock(&dev_priv->drm.struct_mutex);
-		if (IS_ERR(ce))
-			return PTR_ERR(ce);
+		i915->perf.oa.specific_ctx_id = i915_ggtt_offset(ce->state);
+		i915->perf.oa.specific_ctx_id_mask = 0;
+		break;
+	}
 
-		dev_priv->perf.oa.pinned_ctx = ce;
+	case 8:
+	case 9:
+	case 10:
+		if (USES_GUC_SUBMISSION(i915)) {
+			/*
+			 * When using GuC, the context descriptor we write in
+			 * i915 is read by GuC and rewritten before it's
+			 * actually written into the hardware. The LRCA is
+			 * what is put into the context id field of the
+			 * context descriptor by GuC. Because it's aligned to
+			 * a page, the lower 12bits are always at 0 and
+			 * dropped by GuC. They won't be part of the context
+			 * ID in the OA reports, so squash those lower bits.
+			 */
+			i915->perf.oa.specific_ctx_id =
+				lower_32_bits(ce->lrc_desc) >> 12;
 
-		/*
-		 * Explicitly track the ID (instead of calling
-		 * i915_ggtt_offset() on the fly) considering the difference
-		 * with gen8+ and execlists
-		 */
-		dev_priv->perf.oa.specific_ctx_id = i915_ggtt_offset(ce->state);
+			/*
+			 * GuC uses the top bit to signal proxy submission, so
+			 * ignore that bit.
+			 */
+			i915->perf.oa.specific_ctx_id_mask =
+				(1U << (GEN8_CTX_ID_WIDTH - 1)) - 1;
+		} else {
+			i915->perf.oa.specific_ctx_id = stream->ctx->hw_id;
+			i915->perf.oa.specific_ctx_id_mask =
+				(1U << GEN8_CTX_ID_WIDTH) - 1;
+		}
+		break;
+
+	case 11: {
+		struct intel_engine_cs *engine = i915->engine[RCS];
+
+		i915->perf.oa.specific_ctx_id =
+			stream->ctx->hw_id << (GEN11_SW_CTX_ID_SHIFT - 32) |
+			engine->instance << (GEN11_ENGINE_INSTANCE_SHIFT - 32) |
+			engine->class << (GEN11_ENGINE_INSTANCE_SHIFT - 32);
+		i915->perf.oa.specific_ctx_id_mask =
+			((1U << GEN11_SW_CTX_ID_WIDTH) - 1) << (GEN11_SW_CTX_ID_SHIFT - 32) |
+			((1U << GEN11_ENGINE_INSTANCE_WIDTH) - 1) << (GEN11_ENGINE_INSTANCE_SHIFT - 32) |
+			((1 << GEN11_ENGINE_CLASS_WIDTH) - 1) << (GEN11_ENGINE_CLASS_SHIFT - 32);
+		break;
+	}
+
+	default:
+		MISSING_CASE(INTEL_GEN(i915));
 	}
 
+	DRM_DEBUG_DRIVER("filtering on ctx_id=0x%x ctx_id_mask=0x%x\n",
+			 i915->perf.oa.specific_ctx_id,
+			 i915->perf.oa.specific_ctx_id_mask);
+
 	return 0;
 }
 
@@ -1265,6 +1323,7 @@ static void oa_put_render_ctx_id(struct i915_perf_stream *stream)
 	struct intel_context *ce;
 
 	dev_priv->perf.oa.specific_ctx_id = INVALID_CTX_ID;
+	dev_priv->perf.oa.specific_ctx_id_mask = 0;
 
 	ce = fetch_and_zero(&dev_priv->perf.oa.pinned_ctx);
 	if (ce) {

drivers/gpu/drm/i915/intel_lrc.c

@@ -233,6 +233,11 @@ intel_lr_context_descriptor_update(struct i915_gem_context *ctx,
 								/* bits 12-31 */
 	GEM_BUG_ON(desc & GENMASK_ULL(63, 32));
 
+	/*
+	 * The following 32bits are copied into the OA reports (dword 2).
+	 * Consider updating oa_get_render_ctx_id in i915_perf.c when changing
+	 * anything below.
+	 */
 	if (INTEL_GEN(ctx->i915) >= 11) {
 		GEM_BUG_ON(ctx->hw_id >= BIT(GEN11_SW_CTX_ID_WIDTH));
 		desc |= (u64)ctx->hw_id << GEN11_SW_CTX_ID_SHIFT;