diff --git a/sys/net/iflib.h b/sys/net/iflib.h
--- a/sys/net/iflib.h
+++ b/sys/net/iflib.h
@@ -426,6 +426,11 @@
  * function.
  */
 #define IFLIB_FEATURE_QUEUE_SELECT_V2	1400073
+/*
+ * Driver can create subinterfaces with their own Tx/Rx queues
+ * that all share a single device (or commonly, port)
+ */
+#define IFLIB_FEATURE_SUB_INTERFACES	1400083
 
 /*
  * These enum values are used in iflib_needs_restart to indicate to iflib
@@ -484,11 +489,14 @@
 int iflib_device_register(device_t dev, void *softc, if_shared_ctx_t sctx, if_ctx_t *ctxp);
 int iflib_device_deregister(if_ctx_t);
 
-int iflib_irq_alloc(if_ctx_t, if_irq_t, int, driver_filter_t, void *filter_arg, driver_intr_t, void *arg, const char *name);
+int iflib_irq_alloc(if_ctx_t, if_irq_t, int, driver_filter_t, void *filter_arg,
+		    driver_intr_t, void *arg, const char *name);
 int iflib_irq_alloc_generic(if_ctx_t ctx, if_irq_t irq, int rid,
 			    iflib_intr_type_t type, driver_filter_t *filter,
 			    void *filter_arg, int qid, const char *name);
-void iflib_softirq_alloc_generic(if_ctx_t ctx, if_irq_t irq, iflib_intr_type_t type,  void *arg, int qid, const char *name);
+void iflib_softirq_alloc_generic(if_ctx_t ctx, if_irq_t irq,
+				 iflib_intr_type_t type,  void *arg, int qid,
+				 const char *name);
 
 void iflib_irq_free(if_ctx_t ctx, if_irq_t irq);
 
@@ -527,4 +535,11 @@
 if_pseudo_t iflib_clone_register(if_shared_ctx_t);
 void iflib_clone_deregister(if_pseudo_t);
 
+/*
+ * Sub-interface support
+ */
+int iflib_irq_alloc_generic_subctx(if_ctx_t ctx, if_ctx_t subctx, if_irq_t irq,
+				   int rid, iflib_intr_type_t type,
+				   driver_filter_t *filter, void *filter_arg,
+				   int qid, const char *name);
 #endif /*  __IFLIB_H_ */
diff --git a/sys/net/iflib.c b/sys/net/iflib.c
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -213,6 +213,7 @@
 #define isc_legacy_intr ifc_txrx.ift_legacy_intr
 #define isc_txq_select ifc_txrx.ift_txq_select
 #define isc_txq_select_v2 ifc_txrx.ift_txq_select_v2
+
 	eventhandler_tag ifc_vlan_attach_event;
 	eventhandler_tag ifc_vlan_detach_event;
 	struct ether_addr ifc_mac;
@@ -1477,8 +1478,8 @@
 				&dma->idi_tag);
 	if (err) {
 		device_printf(dev,
-		    "%s: bus_dma_tag_create failed: %d\n",
-		    __func__, err);
+		    "%s: bus_dma_tag_create failed: %d (size=%d, align=%d)\n",
+		    __func__, err, size, align);
 		goto fail_0;
 	}
 
@@ -1969,7 +1970,7 @@
 	lowaddr = DMA_WIDTH_TO_BUS_LOWADDR(scctx->isc_dma_width);
 
 	fl = rxq->ifr_fl;
-	for (int i = 0; i <  rxq->ifr_nfl; i++, fl++) {
+	for (int i = 0; i < rxq->ifr_nfl; i++, fl++) {
 		fl->ifl_size = scctx->isc_nrxd[rxq->ifr_fl_offset]; /* this isn't necessarily the same */
 		/* Set up DMA tag for RX buffers. */
 		err = bus_dma_tag_create(bus_get_dma_tag(dev), /* parent */
@@ -2491,7 +2492,6 @@
 static void
 iflib_init_locked(if_ctx_t ctx)
 {
-	if_softc_ctx_t sctx = &ctx->ifc_softc_ctx;
 	if_softc_ctx_t scctx = &ctx->ifc_softc_ctx;
 	if_t ifp = ctx->ifc_ifp;
 	iflib_fl_t fl;
@@ -2521,7 +2521,7 @@
 	if (if_getcapenable(ifp) & IFCAP_TSO6)
 		if_sethwassistbits(ifp, CSUM_IP6_TSO, 0);
 
-	for (i = 0, txq = ctx->ifc_txqs; i < sctx->isc_ntxqsets; i++, txq++) {
+	for (i = 0, txq = ctx->ifc_txqs; i < scctx->isc_ntxqsets; i++, txq++) {
 		CALLOUT_LOCK(txq);
 		callout_stop(&txq->ift_timer);
 #ifdef DEV_NETMAP
@@ -2543,7 +2543,7 @@
 #endif
 	IFDI_INIT(ctx);
 	MPASS(if_getdrvflags(ifp) == i);
-	for (i = 0, rxq = ctx->ifc_rxqs; i < sctx->isc_nrxqsets; i++, rxq++) {
+	for (i = 0, rxq = ctx->ifc_rxqs; i < scctx->isc_nrxqsets; i++, rxq++) {
 		if (iflib_netmap_rxq_init(ctx, rxq) > 0) {
 			/* This rxq is in netmap mode. Skip normal init. */
 			continue;
@@ -2561,7 +2561,7 @@
 	if_setdrvflagbits(ctx->ifc_ifp, IFF_DRV_RUNNING, IFF_DRV_OACTIVE);
 	IFDI_INTR_ENABLE(ctx);
 	txq = ctx->ifc_txqs;
-	for (i = 0; i < sctx->isc_ntxqsets; i++, txq++)
+	for (i = 0; i < scctx->isc_ntxqsets; i++, txq++)
 		callout_reset_on(&txq->ift_timer, iflib_timer_default, iflib_timer, txq,
 			txq->ift_timer.c_cpu);
 
@@ -6449,6 +6449,81 @@
 	return (0);
 }
 
+/*
+ * Allocate a hardware interrupt for subctx using the parent (ctx)'s hardware
+ * resources.
+ *
+ * Similar to iflib_irq_alloc_generic(), but for interrupt type IFLIB_INTR_RXTX
+ * only.
+ *
+ * XXX: Could be removed if subctx's dev has its intr resource allocation
+ * methods replaced with custom ones?
+ */
+int
+iflib_irq_alloc_generic_subctx(if_ctx_t ctx, if_ctx_t subctx, if_irq_t irq,
+			       int rid, iflib_intr_type_t type,
+			       driver_filter_t *filter, void *filter_arg,
+			       int qid, const char *name)
+{
+	device_t dev, subdev;
+	struct grouptask *gtask;
+	struct taskqgroup *tqg;
+	iflib_filter_info_t info;
+	gtask_fn_t *fn;
+	int tqrid, err;
+	driver_filter_t *intr_fast;
+	void *q;
+	
+	MPASS(ctx != NULL);
+	MPASS(subctx != NULL);
+
+	tqrid = rid;
+	dev = ctx->ifc_dev;
+	subdev = subctx->ifc_dev;
+
+	switch (type) {
+	case IFLIB_INTR_RXTX:
+		q = &subctx->ifc_rxqs[qid];
+		info = &subctx->ifc_rxqs[qid].ifr_filter_info;
+		gtask = &subctx->ifc_rxqs[qid].ifr_task;
+		tqg = qgroup_if_io_tqg;
+		fn = _task_fn_rx;
+		intr_fast = iflib_fast_intr_rxtx;
+		NET_GROUPTASK_INIT(gtask, 0, fn, q);
+		break;
+	default:
+		device_printf(dev, "%s: unknown net intr type for subctx %s (%d)\n",
+		    __func__, device_get_nameunit(subdev), type);
+		return (EINVAL);
+	}
+
+	info->ifi_filter = filter;
+	info->ifi_filter_arg = filter_arg;
+	info->ifi_task = gtask;
+	info->ifi_ctx = q;
+
+	NET_GROUPTASK_INIT(gtask, 0, fn, q);
+
+	/* Allocate interrupts from hardware using parent context */
+	err = _iflib_irq_alloc(ctx, irq, rid, intr_fast, NULL, info, name);
+	if (err != 0) {
+		device_printf(dev, "_iflib_irq_alloc failed for subctx %s: %d\n",
+		    device_get_nameunit(subdev), err);
+		return (err);
+	}
+
+	if (tqrid != -1) {
+		err = iflib_irq_set_affinity(ctx, irq, type, qid, gtask, tqg, q,
+		    name);
+		if (err)
+			return (err);
+	} else {
+		taskqgroup_attach(tqg, gtask, q, dev, irq->ii_res, name);
+	}
+
+	return (0);
+}
+
 int
 iflib_irq_alloc_generic(if_ctx_t ctx, if_irq_t irq, int rid,
 			iflib_intr_type_t type, driver_filter_t *filter,
@@ -6538,7 +6613,8 @@
 }
 
 void
-iflib_softirq_alloc_generic(if_ctx_t ctx, if_irq_t irq, iflib_intr_type_t type, void *arg, int qid, const char *name)
+iflib_softirq_alloc_generic(if_ctx_t ctx, if_irq_t irq, iflib_intr_type_t type,
+			    void *arg, int qid, const char *name)
 {
 	device_t dev;
 	struct grouptask *gtask;