static void virtio_serial_device_realize(DeviceState *dev, Error **errp)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtIOSerial *vser = VIRTIO_SERIAL(dev);
    uint32_t i, max_supported_ports;

    if (!vser->serial.max_virtserial_ports) {
        error_setg(errp, "Maximum number of serial ports not specified");
        return;
    }

    /* Each port takes 2 queues, and one pair is for the control queue */
    max_supported_ports = VIRTIO_QUEUE_MAX / 2 - 1;

    if (vser->serial.max_virtserial_ports > max_supported_ports) {
        error_setg(errp, "maximum ports supported: %u", max_supported_ports);
        return;
    }

    /* We don't support emergency write, skip it for now. */
    /* TODO: cleaner fix, depending on host features. */
    virtio_init(vdev, "virtio-serial", VIRTIO_ID_CONSOLE,
                offsetof(struct virtio_console_config, emerg_wr));

    /* Spawn a new virtio-serial bus on which the ports will ride as devices */
    qbus_create_inplace(&vser->bus, sizeof(vser->bus), TYPE_VIRTIO_SERIAL_BUS,
                        dev, vdev->bus_name);
    qbus_set_hotplug_handler(BUS(&vser->bus), DEVICE(vser), errp);
    vser->bus.vser = vser;
    QTAILQ_INIT(&vser->ports);

    vser->bus.max_nr_ports = vser->serial.max_virtserial_ports;
    vser->ivqs = g_malloc(vser->serial.max_virtserial_ports
                          * sizeof(VirtQueue *));
    vser->ovqs = g_malloc(vser->serial.max_virtserial_ports
                          * sizeof(VirtQueue *));

    /* Add a queue for host to guest transfers for port 0 (backward compat) */
    vser->ivqs[0] = virtio_add_queue(vdev, 128, handle_input);
    /* Add a queue for guest to host transfers for port 0 (backward compat) */
    vser->ovqs[0] = virtio_add_queue(vdev, 128, handle_output);

    /* TODO: host to guest notifications can get dropped
     * if the queue fills up. Implement queueing in host,
     * this might also make it possible to reduce the control
     * queue size: as guest preposts buffers there,
     * this will save 4Kbyte of guest memory per entry. */

    /* control queue: host to guest */
    vser->c_ivq = virtio_add_queue(vdev, 32, control_in);
    /* control queue: guest to host */
    vser->c_ovq = virtio_add_queue(vdev, 32, control_out);

    for (i = 1; i < vser->bus.max_nr_ports; i++) {
        /* Add a per-port queue for host to guest transfers */
        vser->ivqs[i] = virtio_add_queue(vdev, 128, handle_input);
        /* Add a per-per queue for guest to host transfers */
        vser->ovqs[i] = virtio_add_queue(vdev, 128, handle_output);
    }

    vser->ports_map = g_malloc0(((vser->serial.max_virtserial_ports + 31) / 32)
        * sizeof(vser->ports_map[0]));
    /*
     * Reserve location 0 for a console port for backward compat
     * (old kernel, new qemu)
     */
    mark_port_added(vser, 0);

    vser->post_load = NULL;

    /*
     * Register for the savevm section with the virtio-console name
     * to preserve backward compat
     */
    register_savevm(dev, "virtio-console", -1, 3, virtio_serial_save,
                    virtio_serial_load, vser);

    QLIST_INSERT_HEAD(&vserdevices.devices, vser, next);
}