Archipelago » qemu

/*

 * A bus for connecting virtio serial and console ports

 *

 * Copyright (C) 2009, 2010 Red Hat, Inc.

 *

 * Author(s):

 *  Amit Shah <amit.shah@redhat.com>

 *

 * Some earlier parts are:

 *  Copyright IBM, Corp. 2008

 * authored by

 *  Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 */

#include "iov.h"

#include "monitor.h"

#include "qemu-queue.h"

#include "sysbus.h"

#include "trace.h"

#include "virtio-serial.h"

/* The virtio-serial bus on top of which the ports will ride as devices */

struct VirtIOSerialBus {

    BusState qbus;

    /* This is the parent device that provides the bus for ports. */

    VirtIOSerial *vser;

    /* The maximum number of ports that can ride on top of this bus */

    uint32_t max_nr_ports;

};

struct VirtIOSerial {

    VirtIODevice vdev;

    VirtQueue *c_ivq, *c_ovq;

    /* Arrays of ivqs and ovqs: one per port */

    VirtQueue **ivqs, **ovqs;

    VirtIOSerialBus bus;

    DeviceState *qdev;

    QTAILQ_HEAD(, VirtIOSerialPort) ports;

    /* bitmap for identifying active ports */

    uint32_t *ports_map;

    struct virtio_console_config config;

};

static VirtIOSerialPort *find_port_by_id(VirtIOSerial *vser, uint32_t id)

{

    VirtIOSerialPort *port;

    if (id == VIRTIO_CONSOLE_BAD_ID) {

        return NULL;

    }

    QTAILQ_FOREACH(port, &vser->ports, next) {

        if (port->id == id)

            return port;

    }

    return NULL;

}

static VirtIOSerialPort *find_port_by_vq(VirtIOSerial *vser, VirtQueue *vq)

{

    VirtIOSerialPort *port;

    QTAILQ_FOREACH(port, &vser->ports, next) {

        if (port->ivq == vq || port->ovq == vq)

            return port;

    }

    return NULL;

}

static bool use_multiport(VirtIOSerial *vser)

{

    return vser->vdev.guest_features & (1 << VIRTIO_CONSOLE_F_MULTIPORT);

}

static size_t write_to_port(VirtIOSerialPort *port,

                            const uint8_t *buf, size_t size)

{

    VirtQueueElement elem;

    VirtQueue *vq;

    size_t offset;

    vq = port->ivq;

    if (!virtio_queue_ready(vq)) {

        return 0;

    }

    offset = 0;

    while (offset < size) {

        size_t len;

        if (!virtqueue_pop(vq, &elem)) {

            break;

        }

        len = iov_from_buf(elem.in_sg, elem.in_num,

                           buf + offset, 0, size - offset);

        offset += len;

        virtqueue_push(vq, &elem, len);

    }

    virtio_notify(&port->vser->vdev, vq);

    return offset;

}

static void discard_vq_data(VirtQueue *vq, VirtIODevice *vdev)

{

    VirtQueueElement elem;

    if (!virtio_queue_ready(vq)) {

        return;

    }

    while (virtqueue_pop(vq, &elem)) {

        virtqueue_push(vq, &elem, 0);

    }

    virtio_notify(vdev, vq);

}

static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,

                                 VirtIODevice *vdev)

{

    VirtIOSerialPortInfo *info;

    assert(port);

    assert(virtio_queue_ready(vq));

    info = DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info);

    while (!port->throttled) {

        unsigned int i;

        /* Pop an elem only if we haven't left off a previous one mid-way */

        if (!port->elem.out_num) {

            if (!virtqueue_pop(vq, &port->elem)) {

                break;

            }

            port->iov_idx = 0;

            port->iov_offset = 0;

        }

        for (i = port->iov_idx; i < port->elem.out_num; i++) {

            size_t buf_size;

            ssize_t ret;

            buf_size = port->elem.out_sg[i].iov_len - port->iov_offset;

            ret = info->have_data(port,

                                  port->elem.out_sg[i].iov_base

                                  + port->iov_offset,

                                  buf_size);

            if (ret < 0 && ret != -EAGAIN) {

                /* We don't handle any other type of errors here */

                abort();

            }

            if (ret == -EAGAIN || (ret >= 0 && ret < buf_size)) {

                /*

                 * this is a temporary check until chardevs can signal to

                 * frontends that they are writable again. This prevents

                 * the console from going into throttled mode (forever)

                 * if virtio-console is connected to a pty without a

                 * listener. Otherwise the guest spins forever.

                 * We can revert this if

                 * 1: chardevs can notify frondends

                 * 2: the guest driver does not spin in these cases

                 */

                if (!info->is_console) {

                    virtio_serial_throttle_port(port, true);

                }

                port->iov_idx = i;

                if (ret > 0) {

                    port->iov_offset += ret;

                }

                break;

            }

            port->iov_offset = 0;

        }

        if (port->throttled) {

            break;

        }

        virtqueue_push(vq, &port->elem, 0);

        port->elem.out_num = 0;

    }

    virtio_notify(vdev, vq);

}

static void flush_queued_data(VirtIOSerialPort *port)

{

    assert(port);

    if (!virtio_queue_ready(port->ovq)) {

        return;

    }

    do_flush_queued_data(port, port->ovq, &port->vser->vdev);

}

static size_t send_control_msg(VirtIOSerialPort *port, void *buf, size_t len)

{

    VirtQueueElement elem;

    VirtQueue *vq;

    struct virtio_console_control *cpkt;

    vq = port->vser->c_ivq;

    if (!virtio_queue_ready(vq)) {

        return 0;

    }

    if (!virtqueue_pop(vq, &elem)) {

        return 0;

    }

    cpkt = (struct virtio_console_control *)buf;

    stl_p(&cpkt->id, port->id);

    memcpy(elem.in_sg[0].iov_base, buf, len);

    virtqueue_push(vq, &elem, len);

    virtio_notify(&port->vser->vdev, vq);

    return len;

}

static size_t send_control_event(VirtIOSerialPort *port, uint16_t event,

                                 uint16_t value)

{

    struct virtio_console_control cpkt;

    stw_p(&cpkt.event, event);

    stw_p(&cpkt.value, value);

    trace_virtio_serial_send_control_event(port->id, event, value);

    return send_control_msg(port, &cpkt, sizeof(cpkt));

}

/* Functions for use inside qemu to open and read from/write to ports */

int virtio_serial_open(VirtIOSerialPort *port)

{

    /* Don't allow opening an already-open port */

    if (port->host_connected) {

        return 0;

    }

    /* Send port open notification to the guest */

    port->host_connected = true;

    send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 1);

    return 0;

}

int virtio_serial_close(VirtIOSerialPort *port)

{

    port->host_connected = false;

    /*

     * If there's any data the guest sent which the app didn't

     * consume, reset the throttling flag and discard the data.

     */

    port->throttled = false;

    discard_vq_data(port->ovq, &port->vser->vdev);

    send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0);

    return 0;

}

/* Individual ports/apps call this function to write to the guest. */

ssize_t virtio_serial_write(VirtIOSerialPort *port, const uint8_t *buf,

                            size_t size)

{

    if (!port || !port->host_connected || !port->guest_connected) {

        return 0;

    }

    return write_to_port(port, buf, size);

}

/*

 * Readiness of the guest to accept data on a port.

 * Returns max. data the guest can receive

 */

size_t virtio_serial_guest_ready(VirtIOSerialPort *port)

{

    VirtQueue *vq = port->ivq;

    if (!virtio_queue_ready(vq) ||

        !(port->vser->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK) ||

        virtio_queue_empty(vq)) {

        return 0;

    }

    if (use_multiport(port->vser) && !port->guest_connected) {

        return 0;

    }

    if (virtqueue_avail_bytes(vq, 4096, 0)) {

        return 4096;

    }

    if (virtqueue_avail_bytes(vq, 1, 0)) {

        return 1;

    }

    return 0;

}

static void flush_queued_data_bh(void *opaque)

{

    VirtIOSerialPort *port = opaque;

    flush_queued_data(port);

}

void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle)

{

    if (!port) {

        return;

    }

    trace_virtio_serial_throttle_port(port->id, throttle);

    port->throttled = throttle;

    if (throttle) {

        return;

    }

    qemu_bh_schedule(port->bh);

}

/* Guest wants to notify us of some event */

static void handle_control_message(VirtIOSerial *vser, void *buf, size_t len)

{

    struct VirtIOSerialPort *port;

    struct VirtIOSerialPortInfo *info;

    struct virtio_console_control cpkt, *gcpkt;

    uint8_t *buffer;

    size_t buffer_len;

    gcpkt = buf;

    if (len < sizeof(cpkt)) {

        /* The guest sent an invalid control packet */

        return;

    }

    cpkt.event = lduw_p(&gcpkt->event);

    cpkt.value = lduw_p(&gcpkt->value);

    trace_virtio_serial_handle_control_message(cpkt.event, cpkt.value);

    if (cpkt.event == VIRTIO_CONSOLE_DEVICE_READY) {

        if (!cpkt.value) {

            error_report("virtio-serial-bus: Guest failure in adding device %s",

                         vser->bus.qbus.name);

            return;

        }

        /*

         * The device is up, we can now tell the device about all the

         * ports we have here.

         */

        QTAILQ_FOREACH(port, &vser->ports, next) {

            send_control_event(port, VIRTIO_CONSOLE_PORT_ADD, 1);

        }

        return;

    }

    port = find_port_by_id(vser, ldl_p(&gcpkt->id));

    if (!port) {

        error_report("virtio-serial-bus: Unexpected port id %u for device %s",

                     ldl_p(&gcpkt->id), vser->bus.qbus.name);

        return;

    }

    trace_virtio_serial_handle_control_message_port(port->id);

    info = DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info);

    switch(cpkt.event) {

    case VIRTIO_CONSOLE_PORT_READY:

        if (!cpkt.value) {

            error_report("virtio-serial-bus: Guest failure in adding port %u for device %s",

                         port->id, vser->bus.qbus.name);

            break;

        }

        /*

         * Now that we know the guest asked for the port name, we're

         * sure the guest has initialised whatever state is necessary

         * for this port. Now's a good time to let the guest know if

         * this port is a console port so that the guest can hook it

         * up to hvc.

         */

        if (info->is_console) {

            send_control_event(port, VIRTIO_CONSOLE_CONSOLE_PORT, 1);

        }

        if (port->name) {

            stw_p(&cpkt.event, VIRTIO_CONSOLE_PORT_NAME);

            stw_p(&cpkt.value, 1);

            buffer_len = sizeof(cpkt) + strlen(port->name) + 1;

            buffer = g_malloc(buffer_len);

            memcpy(buffer, &cpkt, sizeof(cpkt));

            memcpy(buffer + sizeof(cpkt), port->name, strlen(port->name));

            buffer[buffer_len - 1] = 0;

            send_control_msg(port, buffer, buffer_len);

            g_free(buffer);

        }

        if (port->host_connected) {

            send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 1);

        }

        /*

         * When the guest has asked us for this information it means

         * the guest is all setup and has its virtqueues

         * initialised. If some app is interested in knowing about

         * this event, let it know.

         */

        if (info->guest_ready) {

            info->guest_ready(port);

        }

        break;

    case VIRTIO_CONSOLE_PORT_OPEN:

        port->guest_connected = cpkt.value;

        if (cpkt.value && info->guest_open) {

            /* Send the guest opened notification if an app is interested */

            info->guest_open(port);

        }

        if (!cpkt.value && info->guest_close) {

            /* Send the guest closed notification if an app is interested */

            info->guest_close(port);

        }

        break;

    }

}

static void control_in(VirtIODevice *vdev, VirtQueue *vq)

{

}

static void control_out(VirtIODevice *vdev, VirtQueue *vq)

{

    VirtQueueElement elem;

    VirtIOSerial *vser;

    uint8_t *buf;

    size_t len;

    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    len = 0;

    buf = NULL;

    while (virtqueue_pop(vq, &elem)) {

        size_t cur_len, copied;

        cur_len = iov_size(elem.out_sg, elem.out_num);

        /*

         * Allocate a new buf only if we didn't have one previously or

         * if the size of the buf differs

         */

        if (cur_len > len) {

            g_free(buf);

            buf = g_malloc(cur_len);

            len = cur_len;

        }

        copied = iov_to_buf(elem.out_sg, elem.out_num, buf, 0, len);

        handle_control_message(vser, buf, copied);

        virtqueue_push(vq, &elem, 0);

    }

    g_free(buf);

    virtio_notify(vdev, vq);

}

/* Guest wrote something to some port. */

static void handle_output(VirtIODevice *vdev, VirtQueue *vq)

{

    VirtIOSerial *vser;

    VirtIOSerialPort *port;

    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    port = find_port_by_vq(vser, vq);

    if (!port || !port->host_connected) {

        discard_vq_data(vq, vdev);

        return;

    }

    if (!port->throttled) {

        do_flush_queued_data(port, vq, vdev);

        return;

    }

}

static void handle_input(VirtIODevice *vdev, VirtQueue *vq)

{

}

static uint32_t get_features(VirtIODevice *vdev, uint32_t features)

{

    VirtIOSerial *vser;

    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    if (vser->bus.max_nr_ports > 1) {

        features |= (1 << VIRTIO_CONSOLE_F_MULTIPORT);

    }

    return features;

}

/* Guest requested config info */

static void get_config(VirtIODevice *vdev, uint8_t *config_data)

{

    VirtIOSerial *vser;

    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    memcpy(config_data, &vser->config, sizeof(struct virtio_console_config));

}

static void set_config(VirtIODevice *vdev, const uint8_t *config_data)

{

    struct virtio_console_config config;

    memcpy(&config, config_data, sizeof(config));

}

static void virtio_serial_save(QEMUFile *f, void *opaque)

{

    VirtIOSerial *s = opaque;

    VirtIOSerialPort *port;

    uint32_t nr_active_ports;

    unsigned int i, max_nr_ports;

    /* The virtio device */

    virtio_save(&s->vdev, f);

    /* The config space */

    qemu_put_be16s(f, &s->config.cols);

    qemu_put_be16s(f, &s->config.rows);

    qemu_put_be32s(f, &s->config.max_nr_ports);

    /* The ports map */

    max_nr_ports = tswap32(s->config.max_nr_ports);

    for (i = 0; i < (max_nr_ports + 31) / 32; i++) {

        qemu_put_be32s(f, &s->ports_map[i]);

    }

    /* Ports */

    nr_active_ports = 0;

    QTAILQ_FOREACH(port, &s->ports, next) {

        nr_active_ports++;

    }

    qemu_put_be32s(f, &nr_active_ports);

    /*

     * Items in struct VirtIOSerialPort.

     */

    QTAILQ_FOREACH(port, &s->ports, next) {

        uint32_t elem_popped;

        qemu_put_be32s(f, &port->id);

        qemu_put_byte(f, port->guest_connected);

        qemu_put_byte(f, port->host_connected);

        elem_popped = 0;

        if (port->elem.out_num) {

            elem_popped = 1;

        }

        qemu_put_be32s(f, &elem_popped);

        if (elem_popped) {

            qemu_put_be32s(f, &port->iov_idx);

            qemu_put_be64s(f, &port->iov_offset);

            qemu_put_buffer(f, (unsigned char *)&port->elem,

                            sizeof(port->elem));

        }

    }

}

static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)

{

    VirtIOSerial *s = opaque;

    VirtIOSerialPort *port;

    uint32_t max_nr_ports, nr_active_ports, ports_map;

    unsigned int i;

    if (version_id > 3) {

        return -EINVAL;

    }

    /* The virtio device */

    virtio_load(&s->vdev, f);

    if (version_id < 2) {

        return 0;

    }

    /* The config space */

    qemu_get_be16s(f, &s->config.cols);

    qemu_get_be16s(f, &s->config.rows);

    qemu_get_be32s(f, &max_nr_ports);

    tswap32s(&max_nr_ports);

    if (max_nr_ports > tswap32(s->config.max_nr_ports)) {

        /* Source could have had more ports than us. Fail migration. */

        return -EINVAL;

    }

    for (i = 0; i < (max_nr_ports + 31) / 32; i++) {

        qemu_get_be32s(f, &ports_map);

        if (ports_map != s->ports_map[i]) {

            /*

             * Ports active on source and destination don't

             * match. Fail migration.

             */

            return -EINVAL;

        }

    }

    qemu_get_be32s(f, &nr_active_ports);

    /* Items in struct VirtIOSerialPort */

    for (i = 0; i < nr_active_ports; i++) {

        uint32_t id;

        bool host_connected;

        id = qemu_get_be32(f);

        port = find_port_by_id(s, id);

        if (!port) {

            return -EINVAL;

        }

        port->guest_connected = qemu_get_byte(f);

        host_connected = qemu_get_byte(f);

        if (host_connected != port->host_connected) {

            /*

             * We have to let the guest know of the host connection

             * status change

             */

            send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN,

                               port->host_connected);

        }

        if (version_id > 2) {

            uint32_t elem_popped;

            qemu_get_be32s(f, &elem_popped);

            if (elem_popped) {

                qemu_get_be32s(f, &port->iov_idx);

                qemu_get_be64s(f, &port->iov_offset);

                qemu_get_buffer(f, (unsigned char *)&port->elem,

                                sizeof(port->elem));

                virtqueue_map_sg(port->elem.in_sg, port->elem.in_addr,

                                 port->elem.in_num, 1);

                virtqueue_map_sg(port->elem.out_sg, port->elem.out_addr,

                                 port->elem.out_num, 1);

                /*

                 *  Port was throttled on source machine.  Let's

                 *  unthrottle it here so data starts flowing again.

                 */

                virtio_serial_throttle_port(port, false);

            }

        }

    }

    return 0;

}

static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);

static struct BusInfo virtser_bus_info = {

    .name      = "virtio-serial-bus",

    .size      = sizeof(VirtIOSerialBus),

    .print_dev = virtser_bus_dev_print,

    .props      = (Property[]) {

        DEFINE_PROP_UINT32("nr", VirtIOSerialPort, id, VIRTIO_CONSOLE_BAD_ID),

        DEFINE_PROP_STRING("name", VirtIOSerialPort, name),

        DEFINE_PROP_END_OF_LIST()

    }

};

static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)

{

    VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);

    monitor_printf(mon, "%*sport %d, guest %s, host %s, throttle %s\n",

                   indent, "", port->id,

                   port->guest_connected ? "on" : "off",

                   port->host_connected ? "on" : "off",

                   port->throttled ? "on" : "off");

}

/* This function is only used if a port id is not provided by the user */

static uint32_t find_free_port_id(VirtIOSerial *vser)

{

    unsigned int i, max_nr_ports;

    max_nr_ports = tswap32(vser->config.max_nr_ports);

    for (i = 0; i < (max_nr_ports + 31) / 32; i++) {

        uint32_t map, bit;

        map = vser->ports_map[i];

        bit = ffs(~map);

        if (bit) {

            return (bit - 1) + i * 32;

        }

    }

    return VIRTIO_CONSOLE_BAD_ID;

}

static void mark_port_added(VirtIOSerial *vser, uint32_t port_id)

{

    unsigned int i;

    i = port_id / 32;

    vser->ports_map[i] |= 1U << (port_id % 32);

}

static void add_port(VirtIOSerial *vser, uint32_t port_id)

{

    mark_port_added(vser, port_id);

    send_control_event(find_port_by_id(vser, port_id),

                       VIRTIO_CONSOLE_PORT_ADD, 1);

}

static void remove_port(VirtIOSerial *vser, uint32_t port_id)

{

    VirtIOSerialPort *port;

    unsigned int i;

    i = port_id / 32;

    vser->ports_map[i] &= ~(1U << (port_id % 32));

    port = find_port_by_id(vser, port_id);

    /* Flush out any unconsumed buffers first */

    discard_vq_data(port->ovq, &port->vser->vdev);

    send_control_event(port, VIRTIO_CONSOLE_PORT_REMOVE, 1);

}

static int virtser_port_qdev_init(DeviceState *qdev, DeviceInfo *base)

{

    VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);

    VirtIOSerialPortInfo *info = DO_UPCAST(VirtIOSerialPortInfo, qdev, base);

    VirtIOSerialBus *bus = DO_UPCAST(VirtIOSerialBus, qbus, qdev->parent_bus);

    int ret, max_nr_ports;

    bool plugging_port0;

    port->vser = bus->vser;

    port->bh = qemu_bh_new(flush_queued_data_bh, port);

    assert(info->have_data);

    /*

     * Is the first console port we're seeing? If so, put it up at

     * location 0. This is done for backward compatibility (old

     * kernel, new qemu).

     */

    plugging_port0 = info->is_console && !find_port_by_id(port->vser, 0);

    if (find_port_by_id(port->vser, port->id)) {

        error_report("virtio-serial-bus: A port already exists at id %u",

                     port->id);

        return -1;

    }

    if (port->id == VIRTIO_CONSOLE_BAD_ID) {

        if (plugging_port0) {

            port->id = 0;

        } else {

            port->id = find_free_port_id(port->vser);

            if (port->id == VIRTIO_CONSOLE_BAD_ID) {

                error_report("virtio-serial-bus: Maximum port limit for this device reached");

                return -1;

            }

        }

    }

    max_nr_ports = tswap32(port->vser->config.max_nr_ports);

    if (port->id >= max_nr_ports) {

        error_report("virtio-serial-bus: Out-of-range port id specified, max. allowed: %u",

                     max_nr_ports - 1);

        return -1;

    }

    ret = info->init(port);

    if (ret) {

        return ret;

    }

    if (!use_multiport(port->vser)) {

        /*

         * Allow writes to guest in this case; we have no way of

         * knowing if a guest port is connected.

         */

        port->guest_connected = true;

    }

    port->elem.out_num = 0;

    QTAILQ_INSERT_TAIL(&port->vser->ports, port, next);

    port->ivq = port->vser->ivqs[port->id];

    port->ovq = port->vser->ovqs[port->id];

    add_port(port->vser, port->id);

    /* Send an update to the guest about this new port added */

    virtio_notify_config(&port->vser->vdev);

    return ret;

}

static int virtser_port_qdev_exit(DeviceState *qdev)

{

    VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);

    VirtIOSerialPortInfo *info = DO_UPCAST(VirtIOSerialPortInfo, qdev,

                                           port->dev.info);

    VirtIOSerial *vser = port->vser;

    qemu_bh_delete(port->bh);

    remove_port(port->vser, port->id);

    QTAILQ_REMOVE(&vser->ports, port, next);

    if (info->exit) {

        info->exit(port);

    }

    return 0;

}

void virtio_serial_port_qdev_register(VirtIOSerialPortInfo *info)

{

    info->qdev.init = virtser_port_qdev_init;

    info->qdev.bus_info = &virtser_bus_info;

    info->qdev.exit = virtser_port_qdev_exit;

    info->qdev.unplug = qdev_simple_unplug_cb;

    qdev_register(&info->qdev);

}

VirtIODevice *virtio_serial_init(DeviceState *dev, virtio_serial_conf *conf)

{

    VirtIOSerial *vser;

    VirtIODevice *vdev;

    uint32_t i, max_supported_ports;

    if (!conf->max_virtserial_ports)

        return NULL;

    /* Each port takes 2 queues, and one pair is for the control queue */

    max_supported_ports = VIRTIO_PCI_QUEUE_MAX / 2 - 1;

    if (conf->max_virtserial_ports > max_supported_ports) {

        error_report("maximum ports supported: %u", max_supported_ports);

        return NULL;

    }

    vdev = virtio_common_init("virtio-serial", VIRTIO_ID_CONSOLE,

                              sizeof(struct virtio_console_config),

                              sizeof(VirtIOSerial));

    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    /* Spawn a new virtio-serial bus on which the ports will ride as devices */

    qbus_create_inplace(&vser->bus.qbus, &virtser_bus_info, dev, NULL);

    vser->bus.qbus.allow_hotplug = 1;

    vser->bus.vser = vser;

    QTAILQ_INIT(&vser->ports);

    vser->bus.max_nr_ports = conf->max_virtserial_ports;

    vser->ivqs = g_malloc(conf->max_virtserial_ports * sizeof(VirtQueue *));

    vser->ovqs = g_malloc(conf->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->config.max_nr_ports = tswap32(conf->max_virtserial_ports);

    vser->ports_map = g_malloc0(((conf->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->vdev.get_features = get_features;

    vser->vdev.get_config = get_config;

    vser->vdev.set_config = set_config;

    vser->qdev = dev;

    /*

     * 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);

    return vdev;

}

void virtio_serial_exit(VirtIODevice *vdev)

{

    VirtIOSerial *vser = DO_UPCAST(VirtIOSerial, vdev, vdev);

    unregister_savevm(vser->qdev, "virtio-console", vser);

    g_free(vser->ivqs);

    g_free(vser->ovqs);

    g_free(vser->ports_map);

    virtio_cleanup(vdev);

}