[PATCH 1/3] drm/xe/gt_stats: Detect and log overflow

[Francois Dugast]

Check if the atomic counter limit has been reached and if that is the
case, set the counter value to the new increment to prevent keeping
a garbage value, and notify it in the kernel log as below:

    [drm:xe_gt_stats_incr [xe]] GT0: stats vma_pagefault_bytes overflow, resetting

Signed-off-by: Francois Dugast <francois.dugast at intel.com>
---
 drivers/gpu/drm/xe/xe_gt_stats.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_gt_stats.c b/drivers/gpu/drm/xe/xe_gt_stats.c
index 2e9879ea4674..753c081b68a6 100644
--- a/drivers/gpu/drm/xe/xe_gt_stats.c
+++ b/drivers/gpu/drm/xe/xe_gt_stats.c
@@ -8,8 +8,15 @@
 #include <drm/drm_print.h>
 
 #include "xe_gt.h"
+#include "xe_gt_printk.h"
 #include "xe_gt_stats.h"
 
+static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
+	"tlb_inval_count",
+	"vma_pagefault_count",
+	"vma_pagefault_bytes",
+};
+
 /**
  * xe_gt_stats_incr - Increments the specified stats counter
  * @gt: GT structure
@@ -24,13 +31,12 @@ void xe_gt_stats_incr(struct xe_gt *gt, const enum xe_gt_stats_id id, int incr)
 		return;
 
 	atomic_add(incr, &gt->stats.counters[id]);
-}
 
-static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
-	"tlb_inval_count",
-	"vma_pagefault_count",
-	"vma_pagefault_bytes",
-};
+	if (atomic_read(&gt->stats.counters[id]) < 0) {
+		xe_gt_dbg(gt, "stats %s overflow, resetting\n", stat_description[id]);
+		atomic_set(&gt->stats.counters[id], incr);
+	}
+}
 
 /**
  * xe_gt_stats_print_info - Print the GT stats
-- 
2.43.0