drm/xe/uapi: restrict system wide accounting

Since this is considered an info leak (system wide accounting), rather
hide behind perfmon_capable().

v2:
  - Without perfmon_capable() it likely makes more sense to report as zero,
    instead of reporting as used == total size. This should give similar
    behaviour as i915 which rather tracks free instead of used.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Filip Hazubski <filip.hazubski@intel.com>
Cc: Carl Zhang <carl.zhang@intel.com>
Cc: Effie Yu <effie.yu@intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_query.c

@@ -128,7 +128,8 @@ static int query_memory_usage(struct xe_device *xe,
 	usage->regions[0].min_page_size = PAGE_SIZE;
 	usage->regions[0].max_page_size = PAGE_SIZE;
 	usage->regions[0].total_size = man->size << PAGE_SHIFT;
-	usage->regions[0].used = ttm_resource_manager_usage(man);
+	if (perfmon_capable())
+		usage->regions[0].used = ttm_resource_manager_usage(man);
 	usage->num_regions = 1;
 
 	for (i = XE_PL_VRAM0; i <= XE_PL_VRAM1; ++i) {
@@ -145,8 +146,13 @@ static int query_memory_usage(struct xe_device *xe,
 				SZ_1G;
 			usage->regions[usage->num_regions].total_size =
 				man->size;
-			usage->regions[usage->num_regions++].used =
-				ttm_resource_manager_usage(man);
+
+			if (perfmon_capable()) {
+				usage->regions[usage->num_regions].used =
+					ttm_resource_manager_usage(man);
+			}
+
+			usage->num_regions++;
 		}
 	}