drm/i915/guc: Check sizing of guc_capture output

Add intel_guc_capture_output_min_size_est function to
provide a reasonable minimum size for error-capture
region before allocating the shared buffer.
Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321164527.2500062-10-alan.previn.teres.alexis@intel.com

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

@@ -663,6 +663,55 @@ intel_guc_capture_getnullheader(struct intel_guc *guc,
 	return 0;
 }
 
+#define GUC_CAPTURE_OVERBUFFER_MULTIPLIER 3
+
+int
+intel_guc_capture_output_min_size_est(struct intel_guc *guc)
+{
+	struct intel_gt *gt = guc_to_gt(guc);
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	int worst_min_size = 0, num_regs = 0;
+	size_t tmp = 0;
+
+	/*
+	 * If every single engine-instance suffered a failure in quick succession but
+	 * were all unrelated, then a burst of multiple error-capture events would dump
+	 * registers for every one engine instance, one at a time. In this case, GuC
+	 * would even dump the global-registers repeatedly.
+	 *
+	 * For each engine instance, there would be 1 x guc_state_capture_group_t output
+	 * followed by 3 x guc_state_capture_t lists. The latter is how the register
+	 * dumps are split across different register types (where the '3' are global vs class
+	 * vs instance). Finally, let's multiply the whole thing by 3x (just so we are
+	 * not limited to just 1 round of data in a worst case full register dump log)
+	 *
+	 * NOTE: intel_guc_log that allocates the log buffer would round this size up to
+	 * a power of two.
+	 */
+
+	for_each_engine(engine, gt, id) {
+		worst_min_size += sizeof(struct guc_state_capture_group_header_t) +
+				  (3 * sizeof(struct guc_state_capture_header_t));
+
+		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_GLOBAL, 0, &tmp))
+			num_regs += tmp;
+
+		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_ENGINE_CLASS,
+						   engine->class, &tmp)) {
+			num_regs += tmp;
+		}
+		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_ENGINE_INSTANCE,
+						   engine->class, &tmp)) {
+			num_regs += tmp;
+		}
+	}
+
+	worst_min_size += (num_regs * sizeof(struct guc_mmio_reg));
+
+	return (worst_min_size * GUC_CAPTURE_OVERBUFFER_MULTIPLIER);
+}
+
 static void
 guc_capture_free_ads_cache(struct intel_guc_state_capture *gc)
 {

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

@@ -11,6 +11,7 @@
 struct guc_gt_system_info;
 struct intel_guc;
 
+int intel_guc_capture_output_min_size_est(struct intel_guc *guc);
 int intel_guc_capture_getlist(struct intel_guc *guc, u32 owner, u32 type, u32 classid,
 			      void **outptr);
 int intel_guc_capture_getlistsize(struct intel_guc *guc, u32 owner, u32 type, u32 classid,

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

@@ -9,6 +9,7 @@
 #include "i915_drv.h"
 #include "i915_irq.h"
 #include "i915_memcpy.h"
+#include "intel_guc_capture.h"
 #include "intel_guc_log.h"
 
 static void guc_log_copy_debuglogs_for_relay(struct intel_guc_log *log);
@@ -465,6 +466,10 @@ int intel_guc_log_create(struct intel_guc_log *log)
 	 *  |         Capture logs          |
 	 *  +===============================+ + CAPTURE_SIZE
 	 */
+	if (intel_guc_capture_output_min_size_est(guc) > CAPTURE_BUFFER_SIZE)
+		DRM_WARN("GuC log buffer for state_capture maybe too small. %d < %d\n",
+			 CAPTURE_BUFFER_SIZE, intel_guc_capture_output_min_size_est(guc));
+
 	guc_log_size = PAGE_SIZE + CRASH_BUFFER_SIZE + DEBUG_BUFFER_SIZE +
 		       CAPTURE_BUFFER_SIZE;