Index: sys/dev/hyperv/vmbus/vmbus.c
===================================================================
--- sys/dev/hyperv/vmbus/vmbus.c
+++ sys/dev/hyperv/vmbus/vmbus.c
@@ -137,6 +137,7 @@
 static int			vmbus_doattach(struct vmbus_softc *);
 static void			vmbus_event_proc_dummy(struct vmbus_softc *,
 				    int);
+static bus_dma_tag_t	vmbus_get_dma_tag(device_t parent, device_t child);
 static struct vmbus_softc	*vmbus_sc;
 
 SYSCTL_NODE(_hw, OID_AUTO, vmbus, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
@@ -196,6 +197,7 @@
 	DEVMETHOD(vmbus_probe_guid,		vmbus_probe_guid_method),
 	DEVMETHOD(vmbus_get_vcpu_id,		vmbus_get_vcpu_id_method),
 	DEVMETHOD(vmbus_get_event_taskq,	vmbus_get_eventtq_method),
+	DEVMETHOD(bus_get_dma_tag,		vmbus_get_dma_tag),
 
 	DEVMETHOD_END
 };
@@ -219,6 +221,16 @@
 	return vmbus_sc;
 }
 
+static bus_dma_tag_t
+vmbus_get_dma_tag(device_t dev, device_t child)
+{
+#if defined(__aarch64__)
+	struct vmbus_softc *sc = vmbus_get_softc();
+	return (sc->dmat);
+#else
+	return(bus_get_dma_tag(dev));
+#endif
+}
 void
 vmbus_msghc_reset(struct vmbus_msghc *mh, size_t dsize)
 {
@@ -1382,6 +1394,8 @@
 	struct sysctl_oid_list *child;
 	struct sysctl_ctx_list *ctx;
 	int ret;
+	device_t dev;
+	ACPI_HANDLE handle;
 
 	if (sc->vmbus_flags & VMBUS_FLAG_ATTACHED)
 		return (0);
@@ -1420,6 +1434,27 @@
 	if (ret != 0)
 		goto cleanup;
 
+	/* Coherency attribute */
+	dev =  devclass_get_device(devclass_find("vmbus_res"), 0);
+	handle = acpi_get_handle(dev);
+	if (ACPI_FAILURE(acpi_GetInteger(handle, "_CCA", &sc->coherent)))
+		sc->coherent = 0;
+
+	if (bootverbose)
+	device_printf(sc->vmbus_dev, "Bus is%s cache-coherent\n",
+		sc->coherent ? "" : " not");
+	bus_dma_tag_create(NULL,			/* parent */
+		1, 0,					/* alignment, bounds */
+		BUS_SPACE_MAXADDR,			/* lowaddr */
+		BUS_SPACE_MAXADDR,			/* highaddr */
+		NULL, NULL,				/* filter, filterarg */
+		BUS_SPACE_MAXSIZE,			/* maxsize */
+		BUS_SPACE_UNRESTRICTED,			/* nsegments */
+		BUS_SPACE_MAXSIZE,			/* maxsegsize */
+		sc->coherent ? BUS_DMA_COHERENT : 0, 	/* flags */
+		NULL, NULL,				/* lockfunc, lockarg */
+		&sc->dmat);
+
 	/*
 	 * Setup interrupt.
 	 */
Index: sys/dev/hyperv/vmbus/vmbus_var.h
===================================================================
--- sys/dev/hyperv/vmbus/vmbus_var.h
+++ sys/dev/hyperv/vmbus/vmbus_var.h
@@ -129,6 +129,8 @@
 	void *icookie;
 	int vector;
 #endif
+	bus_dma_tag_t   dmat;
+	int     coherent;
 };
 
 #define VMBUS_FLAG_ATTACHED	0x0001	/* vmbus was attached */