drm/i915/guc: Track all sent actions to GuC

For easier debug of any unexpected error responses from GuC that
might be related to non-blocking fast requests, track action code (and
stack if under DEBUG_GUC config) for every H2G request.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230526235538.2230780-4-John.C.Harrison@Intel.com

drivers/gpu/drm/i915/Kconfig.debug

@@ -157,6 +157,7 @@ config DRM_I915_SW_FENCE_CHECK_DAG
 config DRM_I915_DEBUG_GUC
 	bool "Enable additional driver debugging for GuC"
 	depends on DRM_I915
+	select STACKDEPOT
 	default n
 	help
 	  Choose this option to turn on extra driver debugging that may affect

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c

@@ -376,6 +376,24 @@ void intel_guc_ct_disable(struct intel_guc_ct *ct)
 	}
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+static void ct_track_lost_and_found(struct intel_guc_ct *ct, u32 fence, u32 action)
+{
+	unsigned int lost = fence % ARRAY_SIZE(ct->requests.lost_and_found);
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
+	unsigned long entries[SZ_32];
+	unsigned int n;
+
+	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
+
+	/* May be called under spinlock, so avoid sleeping */
+	ct->requests.lost_and_found[lost].stack = stack_depot_save(entries, n, GFP_NOWAIT);
+#endif
+	ct->requests.lost_and_found[lost].fence = fence;
+	ct->requests.lost_and_found[lost].action = action;
+}
+#endif
+
 static u32 ct_get_next_fence(struct intel_guc_ct *ct)
 {
 	/* For now it's trivial */
@@ -447,6 +465,11 @@ static int ct_write(struct intel_guc_ct *ct,
 	}
 	GEM_BUG_ON(tail > size);
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+	ct_track_lost_and_found(ct, fence,
+				FIELD_GET(GUC_HXG_EVENT_MSG_0_ACTION, action[0]));
+#endif
+
 	/*
 	 * make sure H2G buffer update and LRC tail update (if this triggering a
 	 * submission) are visible before updating the descriptor tail
@@ -953,6 +976,43 @@ static int ct_read(struct intel_guc_ct *ct, struct ct_incoming_msg **msg)
 	return -EPIPE;
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+static bool ct_check_lost_and_found(struct intel_guc_ct *ct, u32 fence)
+{
+	unsigned int n;
+	char *buf = NULL;
+	bool found = false;
+
+	lockdep_assert_held(&ct->requests.lock);
+
+	for (n = 0; n < ARRAY_SIZE(ct->requests.lost_and_found); n++) {
+		if (ct->requests.lost_and_found[n].fence != fence)
+			continue;
+		found = true;
+
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
+		buf = kmalloc(SZ_4K, GFP_NOWAIT);
+		if (buf && stack_depot_snprint(ct->requests.lost_and_found[n].stack,
+					       buf, SZ_4K, 0)) {
+			CT_ERROR(ct, "Fence %u was used by action %#04x sent at\n%s",
+				 fence, ct->requests.lost_and_found[n].action, buf);
+			break;
+		}
+#endif
+		CT_ERROR(ct, "Fence %u was used by action %#04x\n",
+			 fence, ct->requests.lost_and_found[n].action);
+		break;
+	}
+	kfree(buf);
+	return found;
+}
+#else
+static bool ct_check_lost_and_found(struct intel_guc_ct *ct, u32 fence)
+{
+	return false;
+}
+#endif
+
 static int ct_handle_response(struct intel_guc_ct *ct, struct ct_incoming_msg *response)
 {
 	u32 len = FIELD_GET(GUC_CTB_MSG_0_NUM_DWORDS, response->msg[0]);
@@ -996,9 +1056,11 @@ static int ct_handle_response(struct intel_guc_ct *ct, struct ct_incoming_msg *r
 	if (!found) {
 		CT_ERROR(ct, "Unsolicited response message: len %u, data %#x (fence %u, last %u)\n",
 			 len, hxg[0], fence, ct->requests.last_fence);
+		if (!ct_check_lost_and_found(ct, fence)) {
 			list_for_each_entry(req, &ct->requests.pending, link)
 				CT_ERROR(ct, "request %u awaits response\n",
 					 req->fence);
+		}
 		err = -ENOKEY;
 	}
 	spin_unlock_irqrestore(&ct->requests.lock, flags);

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h

@@ -8,6 +8,7 @@
 
 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
+#include <linux/stackdepot.h>
 #include <linux/workqueue.h>
 #include <linux/ktime.h>
 #include <linux/wait.h>
@@ -81,6 +82,16 @@ struct intel_guc_ct {
 
 		struct list_head incoming; /* incoming requests */
 		struct work_struct worker; /* handler for incoming requests */
+
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+		struct {
+			u16 fence;
+			u16 action;
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC)
+			depot_stack_handle_t stack;
+#endif
+		} lost_and_found[SZ_16];
+#endif
 	} requests;
 
 	/** @stall_time: time of first time a CTB submission is stalled */