virtio-serial: Use MSI vectors for port virtqueues

This commit enables the use of MSI interrupts for virtqueue
notifications for ports. We use nr_ports + 1 (for control channel) msi
entries for the ports, as only the in_vq operations need an interrupt on
the guest.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/virtio-pci.c

@@ -499,10 +499,13 @@ static int virtio_serial_init_pci(PCIDevice *pci_dev)
     if (!vdev) {
         return -1;
     }
+    vdev->nvectors = proxy->nvectors ? proxy->nvectors
+                                     : proxy->max_virtserial_ports + 1;
     virtio_init_pci(proxy, vdev,
                     PCI_VENDOR_ID_REDHAT_QUMRANET,
                     PCI_DEVICE_ID_VIRTIO_CONSOLE,
                     proxy->class_code, 0x00);
+    proxy->nvectors = vdev->nvectors;
     return 0;
 }
 
@@ -581,6 +584,7 @@ static PCIDeviceInfo virtio_info[] = {
         .init      = virtio_serial_init_pci,
         .exit      = virtio_exit_pci,
         .qdev.props = (Property[]) {
+            DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 0),
             DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, 0),
             DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
             DEFINE_PROP_UINT32("max_ports", VirtIOPCIProxy, max_virtserial_ports,