Index: sys/dev/hyperv/hvsock/hv_sock.c
===================================================================
--- sys/dev/hyperv/hvsock/hv_sock.c
+++ sys/dev/hyperv/hvsock/hv_sock.c
@@ -74,6 +74,8 @@
 
 MALLOC_DEFINE(M_HVSOCK, "hyperv_socket", "hyperv socket control structures");
 
+static int hvs_dom_probe(void);
+
 /* The MTU is 16KB per host side's design */
 #define HVSOCK_MTU_SIZE		(1024 * 16)
 #define HVSOCK_SEND_BUF_SZ	(PAGE_SIZE - sizeof(struct vmpipe_proto_header))
@@ -124,6 +126,7 @@
 static struct domain		hv_socket_domain = {
 	.dom_family =		AF_HYPERV,
 	.dom_name =		"hyperv",
+	.dom_probe =		hvs_dom_probe,
 	.dom_protosw =		hv_socket_protosw,
 	.dom_protoswNPROTOSW =	&hv_socket_protosw[nitems(hv_socket_protosw)]
 };
@@ -322,6 +325,16 @@
 	sx_xunlock(&hvs_trans_socks_sx);
 }
 
+static int
+hvs_dom_probe(void)
+{
+
+	/* Don't even give us a chance to attach on non-HyperV. */
+	if (vm_guest != VM_GUEST_HV)
+		return (ENXIO);
+	return (0);
+}
+
 void
 hvs_trans_init(void)
 {
@@ -329,9 +342,6 @@
 	if (!IS_DEFAULT_VNET(curvnet))
 		return;
 
-	if (vm_guest != VM_GUEST_HV)
-		return;
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_init called\n", __func__);
 
@@ -354,9 +364,6 @@
 {
 	struct hvs_pcb *pcb = so2hvspcb(so);
 
-	if (vm_guest != VM_GUEST_HV)
-		return (ESOCKTNOSUPPORT);
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_attach called\n", __func__);
 
@@ -383,9 +390,6 @@
 {
 	struct hvs_pcb *pcb;
 
-	if (vm_guest != VM_GUEST_HV)
-		return;
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_detach called\n", __func__);
 
@@ -595,9 +599,6 @@
 {
 	struct hvs_pcb *pcb;
 
-	if (vm_guest != VM_GUEST_HV)
-		return (ESOCKTNOSUPPORT);
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_disconnect called\n", __func__);
 
@@ -925,9 +926,6 @@
 {
 	struct hvs_pcb *pcb;
 
-	if (vm_guest != VM_GUEST_HV)
-		return;
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_close called\n", __func__);
 
@@ -969,9 +967,6 @@
 {
 	struct hvs_pcb *pcb = so2hvspcb(so);
 
-	if (vm_guest != VM_GUEST_HV)
-		return;
-
 	HVSOCK_DBG(HVSOCK_DBG_VERBOSE,
 	    "%s: HyperV Socket hvs_trans_abort called\n", __func__);
 
Index: sys/kern/uipc_domain.c
===================================================================
--- sys/kern/uipc_domain.c
+++ sys/kern/uipc_domain.c
@@ -173,6 +173,8 @@
 	struct domain *dp = arg;
 	struct protosw *pr;
 
+	if ((dp->dom_flags & DOMF_SUPPORTED) == 0)
+		return;
 	if (dp->dom_init)
 		(*dp->dom_init)();
 	for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
@@ -200,6 +202,8 @@
 {
 	struct domain *dp = arg;
 
+	if ((dp->dom_flags & DOMF_SUPPORTED) == 0)
+		return;
 	if (dp->dom_destroy)
 		(*dp->dom_destroy)();
 }
@@ -216,6 +220,9 @@
 	struct domain *dp;
 
 	dp = (struct domain *)data;
+	if (dp->dom_probe != NULL && (*dp->dom_probe)() != 0)
+		return;
+	dp->dom_flags |= DOMF_SUPPORTED;
 	mtx_lock(&dom_mtx);
 	dp->dom_next = domains;
 	domains = dp;
Index: sys/sys/domain.h
===================================================================
--- sys/sys/domain.h
+++ sys/sys/domain.h
@@ -49,8 +49,10 @@
 struct domain {
 	int	dom_family;		/* AF_xxx */
 	char	*dom_name;
+	int	dom_flags;
 	void	(*dom_init)		/* initialize domain data structures */
 		(void);
+	int	(*dom_probe)(void);	/* check for support (optional) */
 	void	(*dom_destroy)		/* cleanup structures / state */
 		(void);
 	int	(*dom_externalize)	/* externalize access rights */
@@ -69,6 +71,9 @@
 					/* af-dependent data on ifnet */
 };
 
+/* dom_flags */
+#define	DOMF_SUPPORTED	0x0001	/* System supports this domain. */
+
 #ifdef _KERNEL
 extern int	domain_init_status;
 extern struct	domain *domains;