[PATCH v3 5/7] drm/xe: Guard against NULL GT in xe_pmu.c

[Jonathan Cavitt <jonathan.cavitt@intel.com>]

Static analysis reveals the following issue:
xe_device_lookup_gt is theoretically able to return NULL in some cases,
but several use cases don't check the return value before performing a
dereference, resulting in a NULL pointer dereference.

Use xe_device_get_gt in places where this is not already covered.
Additionally, only perform xe_force_wake_put in xe_pmu_event_destroy if
gt exists.

v2:
- Pass xe_gt to event_gt_forcewake (Michal)
  - Above necessitated passing xe_gt to event_supported (jcavitt)
- Only perform xe_force_wake_put in xe_pmu_event_destroy if gt exists.

v3:
- Use xe_device_get_gt

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
---
 drivers/gpu/drm/xe/xe_pmu.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_pmu.c b/drivers/gpu/drm/xe/xe_pmu.c
index 6c428f1e9e23..60b19d625229 100644
--- a/drivers/gpu/drm/xe/xe_pmu.c
+++ b/drivers/gpu/drm/xe/xe_pmu.c
@@ -140,7 +140,7 @@ static bool event_gt_forcewake(struct perf_event *event)
 	if (!is_engine_event(config) && !is_gt_frequency_event(event))
 		return true;
 
-	gt = xe_device_lookup_gt(xe, config_to_gt_id(config));
+	gt = xe_device_get_gt(xe, config_to_gt_id(config));
 
 	fw_ref = kzalloc(sizeof(*fw_ref), GFP_KERNEL);
 	if (!fw_ref)
@@ -219,7 +219,10 @@ static void xe_pmu_event_destroy(struct perf_event *event)
 
 	if (fw_ref) {
 		gt = xe_device_lookup_gt(xe, config_to_gt_id(event->attr.config));
-		xe_force_wake_put(gt_to_fw(gt), *fw_ref);
+
+		if (gt)
+			xe_force_wake_put(gt_to_fw(gt), *fw_ref);
+
 		kfree(fw_ref);
 		event->pmu_private = NULL;
 	}
-- 
2.43.0