diff -r 616b57c32406 sys/dev/cxgbe/t4_main.c
--- a/sys/dev/cxgbe/t4_main.c	Tue May 02 09:34:55 2017 -0700
+++ b/sys/dev/cxgbe/t4_main.c	Fri May 05 18:01:09 2017 -0700
@@ -520,6 +520,7 @@ static int sysctl_holdoff_tmr_idx(SYSCTL
 static int sysctl_holdoff_pktc_idx(SYSCTL_HANDLER_ARGS);
 static int sysctl_qsize_rxq(SYSCTL_HANDLER_ARGS);
 static int sysctl_qsize_txq(SYSCTL_HANDLER_ARGS);
+static int sysctl_blink_led(SYSCTL_HANDLER_ARGS);
 static int sysctl_pause_settings(SYSCTL_HANDLER_ARGS);
 static int sysctl_fec(SYSCTL_HANDLER_ARGS);
 static int sysctl_autoneg(SYSCTL_HANDLER_ARGS);
@@ -5390,6 +5391,10 @@ vi_sysctls(struct vi_info *vi)
 	SYSCTL_ADD_PROC(ctx, children, OID_AUTO, "qsize_txq",
 	    CTLTYPE_INT | CTLFLAG_RW, vi, 0, sysctl_qsize_txq, "I",
 	    "tx queue size");
+
+	SYSCTL_ADD_PROC(ctx, children, OID_AUTO, "blink_led",
+	    CTLTYPE_INT | CTLFLAG_RW, vi, 0, sysctl_blink_led, "I",
+	    "Blink the LED for this VI");
 }
 
 static void
@@ -5843,6 +5848,32 @@ sysctl_qsize_txq(SYSCTL_HANDLER_ARGS)
 }
 
 static int
+sysctl_blink_led(SYSCTL_HANDLER_ARGS)
+{
+	struct vi_info *vi = arg1;
+	struct adapter *sc = vi->pi->adapter;
+	int n, rc;
+
+	n = 0;
+	rc = sysctl_handle_int(oidp, &n, 0, req);
+	if (rc != 0 || req->newptr == NULL)
+		return (rc);
+
+	if (n < 0)
+		return (EINVAL);
+
+	rc = begin_synchronized_op(sc, vi, HOLD_LOCK | SLEEP_OK | INTR_OK,
+	    "t4led");
+	if (rc)
+		return (rc);
+
+	t4_identify_port(sc, sc->mbox, vi->viid, n);
+
+	end_synchronized_op(sc, LOCK_HELD);
+	return (rc);
+}
+
+static int
 sysctl_pause_settings(SYSCTL_HANDLER_ARGS)
 {
 	struct port_info *pi = arg1;