diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index 8095cb0805..bfccf5e9a2 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1764,6 +1764,7 @@ static void hvf_wfi(CPUState *cpu)
     hvf_wait_for_ipi(cpu, &ts);
 }
 
+/* Must be called by the owning thread */
 static void hvf_sync_vtimer(CPUState *cpu)
 {
     ARMCPU *arm_cpu = ARM_CPU(cpu);