diff --git a/target/arm/gtimer.h b/target/arm/gtimer.h
index 0e89b8e58d..d49c63cbf8 100644
--- a/target/arm/gtimer.h
+++ b/target/arm/gtimer.h
@@ -10,11 +10,11 @@
 #define TARGET_ARM_GTIMER_H
 
 enum {
-    GTIMER_PHYS     = 0,
-    GTIMER_VIRT     = 1,
-    GTIMER_HYP      = 2,
-    GTIMER_SEC      = 3,
-    GTIMER_HYPVIRT  = 4,
+    GTIMER_PHYS     = 0, /* CNTP_* ; EL1 physical timer */
+    GTIMER_VIRT     = 1, /* CNTV_* ; EL1 virtual timer */
+    GTIMER_HYP      = 2, /* CNTHP_* ; EL2 physical timer */
+    GTIMER_SEC      = 3, /* CNTPS_* ; EL3 physical timer */
+    GTIMER_HYPVIRT  = 4, /* CNTHV_* ; EL2 virtual timer ; only if FEAT_VHE */
     GTIMER_S_EL2_PHYS = 5, /* CNTHPS_* ; only if FEAT_SEL2 */
     GTIMER_S_EL2_VIRT = 6, /* CNTHVS_* ; only if FEAT_SEL2 */
 #define NUM_GTIMERS   7