Index: head/sys/dev/hyperv/vmbus/vmbus.c
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus.c
+++ head/sys/dev/hyperv/vmbus/vmbus.c
@@ -77,6 +77,8 @@
 static uint32_t			vmbus_get_version_method(device_t, device_t);
 static int			vmbus_probe_guid_method(device_t, device_t,
 				    const struct hyperv_guid *);
+static uint32_t			vmbus_get_vcpu_id_method(device_t bus,
+				    device_t dev, int cpu);
 
 static int			vmbus_init(struct vmbus_softc *);
 static int			vmbus_connect(struct vmbus_softc *, uint32_t);
@@ -135,6 +137,7 @@
 	/* Vmbus interface */
 	DEVMETHOD(vmbus_get_version,		vmbus_get_version_method),
 	DEVMETHOD(vmbus_probe_guid,		vmbus_probe_guid_method),
+	DEVMETHOD(vmbus_get_vcpu_id,		vmbus_get_vcpu_id_method),
 
 	DEVMETHOD_END
 };
@@ -991,6 +994,14 @@
 	return ENXIO;
 }
 
+static uint32_t
+vmbus_get_vcpu_id_method(device_t bus, device_t dev, int cpu)
+{
+	const struct vmbus_softc *sc = device_get_softc(bus);
+
+	return (VMBUS_PCPU_GET(sc, vcpuid, cpu));
+}
+
 static int
 vmbus_probe(device_t dev)
 {
Index: head/sys/dev/hyperv/vmbus/vmbus_if.m
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_if.m
+++ head/sys/dev/hyperv/vmbus/vmbus_if.m
@@ -45,3 +45,9 @@
 	device_t dev;
 	const struct hyperv_guid *guid;
 };
+
+METHOD uint32_t get_vcpu_id {
+	device_t bus;
+	device_t dev;
+	int cpu;
+};