Index: sys/dev/uart/uart_bus.h
===================================================================
--- sys/dev/uart/uart_bus.h
+++ sys/dev/uart/uart_bus.h
@@ -92,6 +92,7 @@
 	int		sc_txbusy:1;	/* This UART is transmitting. */
 	int		sc_isquelch:1;	/* This UART has input squelched. */
 	int		sc_testintr:1;	/* This UART is under int. testing. */
+	int		sc_msi:1;	/* This UART is using MSI */
 
 	struct uart_devinfo *sc_sysdev;	/* System device (or NULL). */
 
Index: sys/dev/uart/uart_bus_pci.c
===================================================================
--- sys/dev/uart/uart_bus_pci.c
+++ sys/dev/uart/uart_bus_pci.c
@@ -45,12 +45,14 @@
 #define	DEFAULT_RCLK	1843200
 
 static int uart_pci_probe(device_t dev);
+static int uart_pci_attach(device_t dev);
+static int uart_pci_detach(device_t dev);
 
 static device_method_t uart_pci_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		uart_pci_probe),
-	DEVMETHOD(device_attach,	uart_bus_attach),
-	DEVMETHOD(device_detach,	uart_bus_detach),
+	DEVMETHOD(device_attach,	uart_pci_attach),
+	DEVMETHOD(device_detach,	uart_pci_detach),
 	DEVMETHOD(device_resume,	uart_bus_resume),
 	DEVMETHOD_END
 };
@@ -206,7 +208,52 @@
 	/* Set/override the device description. */
 	if (id->desc)
 		device_set_desc(dev, id->desc);
+	/* Enable MSI if this device has MSI vectors. */
+	if (pci_msi_count(dev) > 0)
+		sc->sc_msi = 1;
 	return (result);
 }
 
+static int
+uart_pci_attach(device_t dev)
+{
+	device_t parent;
+	struct uart_softc *sc;
+	int count;
+
+	parent = device_get_parent(dev);
+	sc = device_get_softc(dev);
+
+	if (sc->sc_msi) {
+		count = 1;
+		if (pci_alloc_msi(dev, &count) == 0) {
+			if (count == 1) {
+				sc->sc_irid = 1;
+				device_printf(dev, "Using %d MSI message\n",
+				    count);
+			} else {
+				pci_release_msi(dev);
+				sc->sc_msi = 0;
+			}
+		}
+	}
+
+	return (uart_bus_attach(dev));
+}
+
+static int
+uart_pci_detach(device_t dev)
+{
+	device_t parent;
+	struct uart_softc *sc;
+
+	parent = device_get_parent(dev);
+	sc = device_get_softc(dev);
+
+	if (sc->sc_msi && sc->sc_irid != 0)
+		pci_release_msi(dev);
+
+	return (uart_bus_detach(dev));
+}
+
 DRIVER_MODULE(uart, pci, uart_pci_driver, uart_devclass, NULL, NULL);
Index: sys/dev/uart/uart_core.c
===================================================================
--- sys/dev/uart/uart_core.c
+++ sys/dev/uart/uart_core.c
@@ -677,9 +677,11 @@
 	 * safest thing to do.
 	 */
 	if (filt != FILTER_SCHEDULE_THREAD && !uart_force_poll) {
-		sc->sc_irid = 0;
+		if (!sc->sc_msi)
+			sc->sc_irid = 0;
 		sc->sc_ires = bus_alloc_resource_any(dev, SYS_RES_IRQ,
-		    &sc->sc_irid, RF_ACTIVE | RF_SHAREABLE);
+		    &sc->sc_irid,
+		    RF_ACTIVE | (sc->sc_irid != 0 ? 0 : RF_SHAREABLE));
 	}
 	if (sc->sc_ires != NULL) {
 		error = bus_setup_intr(dev, sc->sc_ires, INTR_TYPE_TTY,