diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index f0a0e5d1a7..fdf8df09d4 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -689,6 +689,7 @@ int hvf_arch_put_registers(CPUState *cpu)
     return 0;
 }
 
+/* Must be called by the owning thread */
 static void flush_cpu_state(CPUState *cpu)
 {
     if (cpu->vcpu_dirty) {