hw/virtio-serial-bus.c

   1 /*
   2  * A bus for connecting virtio serial and console ports
   3  *
   4  * Copyright (C) 2009 Red Hat, Inc.
   5  *
   6  * Author(s):
   7  *  Amit Shah <amit.shah@redhat.com>
   8  *
   9  * Some earlier parts are:
  10  *  Copyright IBM, Corp. 2008
  11  * authored by
  12  *  Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
  13  *
  14  * This work is licensed under the terms of the GNU GPL, version 2.  See
  15  * the COPYING file in the top-level directory.
  16  */
  17
  18 #include "monitor.h"
  19 #include "qemu-queue.h"
  20 #include "sysbus.h"
  21 #include "virtio-serial.h"
  22
  23 /* The virtio-serial bus on top of which the ports will ride as devices */
  24 struct VirtIOSerialBus {
  25     BusState qbus;
  26
  27     /* This is the parent device that provides the bus for ports. */
  28     VirtIOSerial *vser;
  29
  30     /* The maximum number of ports that can ride on top of this bus */
  31     uint32_t max_nr_ports;
  32 };
  33
  34 struct VirtIOSerial {
  35     VirtIODevice vdev;
  36
  37     VirtQueue *c_ivq, *c_ovq;
  38     /* Arrays of ivqs and ovqs: one per port */
  39     VirtQueue **ivqs, **ovqs;
  40
  41     VirtIOSerialBus *bus;
  42
  43     QTAILQ_HEAD(, VirtIOSerialPort) ports;
  44
  45     /* bitmap for identifying active ports */
  46     uint32_t *ports_map;
  47
  48     struct virtio_console_config config;
  49 };
  50
  51 static VirtIOSerialPort *find_port_by_id(VirtIOSerial *vser, uint32_t id)
  52 {
  53     VirtIOSerialPort *port;
  54
  55     if (id == VIRTIO_CONSOLE_BAD_ID) {
  56         return NULL;
  57     }
  58
  59     QTAILQ_FOREACH(port, &vser->ports, next) {
  60         if (port->id == id)
  61             return port;
  62     }
  63     return NULL;
  64 }
  65
  66 static VirtIOSerialPort *find_port_by_vq(VirtIOSerial *vser, VirtQueue *vq)
  67 {
  68     VirtIOSerialPort *port;
  69
  70     QTAILQ_FOREACH(port, &vser->ports, next) {
  71         if (port->ivq == vq || port->ovq == vq)
  72             return port;
  73     }
  74     return NULL;
  75 }
  76
  77 static bool use_multiport(VirtIOSerial *vser)
  78 {
  79     return vser->vdev.guest_features & (1 << VIRTIO_CONSOLE_F_MULTIPORT);
  80 }
  81
  82 static size_t write_to_port(VirtIOSerialPort *port,
  83                             const uint8_t *buf, size_t size)
  84 {
  85     VirtQueueElement elem;
  86     VirtQueue *vq;
  87     size_t offset = 0;
  88     size_t len = 0;
  89
  90     vq = port->ivq;
  91     if (!virtio_queue_ready(vq)) {
  92         return 0;
  93     }
  94
  95     while (offset < size) {
  96         int i;
  97
  98         if (!virtqueue_pop(vq, &elem)) {
  99             break;
 100         }
 101
 102         for (i = 0; offset < size && i < elem.in_num; i++) {
 103             len = MIN(elem.in_sg[i].iov_len, size - offset);
 104
 105             memcpy(elem.in_sg[i].iov_base, buf + offset, len);
 106             offset += len;
 107         }
 108         virtqueue_push(vq, &elem, len);
 109     }
 110
 111     virtio_notify(&port->vser->vdev, vq);
 112     return offset;
 113 }
 114
 115 static size_t send_control_msg(VirtIOSerialPort *port, void *buf, size_t len)
 116 {
 117     VirtQueueElement elem;
 118     VirtQueue *vq;
 119     struct virtio_console_control *cpkt;
 120
 121     vq = port->vser->c_ivq;
 122     if (!virtio_queue_ready(vq)) {
 123         return 0;
 124     }
 125     if (!virtqueue_pop(vq, &elem)) {
 126         return 0;
 127     }
 128
 129     cpkt = (struct virtio_console_control *)buf;
 130     stl_p(&cpkt->id, port->id);
 131     memcpy(elem.in_sg[0].iov_base, buf, len);
 132
 133     virtqueue_push(vq, &elem, len);
 134     virtio_notify(&port->vser->vdev, vq);
 135     return len;
 136 }
 137
 138 static size_t send_control_event(VirtIOSerialPort *port, uint16_t event,
 139                                  uint16_t value)
 140 {
 141     struct virtio_console_control cpkt;
 142
 143     stw_p(&cpkt.event, event);
 144     stw_p(&cpkt.value, value);
 145
 146     return send_control_msg(port, &cpkt, sizeof(cpkt));
 147 }
 148
 149 /* Functions for use inside qemu to open and read from/write to ports */
 150 int virtio_serial_open(VirtIOSerialPort *port)
 151 {
 152     /* Don't allow opening an already-open port */
 153     if (port->host_connected) {
 154         return 0;
 155     }
 156     /* Send port open notification to the guest */
 157     port->host_connected = true;
 158     send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
 159
 160     return 0;
 161 }
 162
 163 int virtio_serial_close(VirtIOSerialPort *port)
 164 {
 165     port->host_connected = false;
 166     send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
 167
 168     return 0;
 169 }
 170
 171 /* Individual ports/apps call this function to write to the guest. */
 172 ssize_t virtio_serial_write(VirtIOSerialPort *port, const uint8_t *buf,
 173                             size_t size)
 174 {
 175     if (!port || !port->host_connected || !port->guest_connected) {
 176         return 0;
 177     }
 178     return write_to_port(port, buf, size);
 179 }
 180
 181 /*
 182  * Readiness of the guest to accept data on a port.
 183  * Returns max. data the guest can receive
 184  */
 185 size_t virtio_serial_guest_ready(VirtIOSerialPort *port)
 186 {
 187     VirtQueue *vq = port->ivq;
 188
 189     if (!virtio_queue_ready(vq) ||
 190         !(port->vser->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK) ||
 191         virtio_queue_empty(vq)) {
 192         return 0;
 193     }
 194     if (use_multiport(port->vser) && !port->guest_connected) {
 195         return 0;
 196     }
 197
 198     if (virtqueue_avail_bytes(vq, 4096, 0)) {
 199         return 4096;
 200     }
 201     if (virtqueue_avail_bytes(vq, 1, 0)) {
 202         return 1;
 203     }
 204     return 0;
 205 }
 206
 207 /* Guest wants to notify us of some event */
 208 static void handle_control_message(VirtIOSerial *vser, void *buf)
 209 {
 210     struct VirtIOSerialPort *port;
 211     struct virtio_console_control cpkt, *gcpkt;
 212     uint8_t *buffer;
 213     size_t buffer_len;
 214
 215     gcpkt = buf;
 216
 217     cpkt.event = lduw_p(&gcpkt->event);
 218     cpkt.value = lduw_p(&gcpkt->value);
 219
 220     port = find_port_by_id(vser, ldl_p(&gcpkt->id));
 221     if (!port && cpkt.event != VIRTIO_CONSOLE_DEVICE_READY)
 222         return;
 223
 224     switch(cpkt.event) {
 225     case VIRTIO_CONSOLE_DEVICE_READY:
 226         /*
 227          * The device is up, we can now tell the device about all the
 228          * ports we have here.
 229          */
 230         QTAILQ_FOREACH(port, &vser->ports, next) {
 231             send_control_event(port, VIRTIO_CONSOLE_PORT_ADD, 1);
 232         }
 233         break;
 234
 235     case VIRTIO_CONSOLE_PORT_READY:
 236         /*
 237          * Now that we know the guest asked for the port name, we're
 238          * sure the guest has initialised whatever state is necessary
 239          * for this port. Now's a good time to let the guest know if
 240          * this port is a console port so that the guest can hook it
 241          * up to hvc.
 242          */
 243         if (port->is_console) {
 244             send_control_event(port, VIRTIO_CONSOLE_CONSOLE_PORT, 1);
 245         }
 246
 247         if (port->name) {
 248             stw_p(&cpkt.event, VIRTIO_CONSOLE_PORT_NAME);
 249             stw_p(&cpkt.value, 1);
 250
 251             buffer_len = sizeof(cpkt) + strlen(port->name) + 1;
 252             buffer = qemu_malloc(buffer_len);
 253
 254             memcpy(buffer, &cpkt, sizeof(cpkt));
 255             memcpy(buffer + sizeof(cpkt), port->name, strlen(port->name));
 256             buffer[buffer_len - 1] = 0;
 257
 258             send_control_msg(port, buffer, buffer_len);
 259             qemu_free(buffer);
 260         }
 261
 262         if (port->host_connected) {
 263             send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
 264         }
 265
 266         /*
 267          * When the guest has asked us for this information it means
 268          * the guest is all setup and has its virtqueues
 269          * initialised. If some app is interested in knowing about
 270          * this event, let it know.
 271          */
 272         if (port->info->guest_ready) {
 273             port->info->guest_ready(port);
 274         }
 275         break;
 276
 277     case VIRTIO_CONSOLE_PORT_OPEN:
 278         port->guest_connected = cpkt.value;
 279         if (cpkt.value && port->info->guest_open) {
 280             /* Send the guest opened notification if an app is interested */
 281             port->info->guest_open(port);
 282         }
 283
 284         if (!cpkt.value && port->info->guest_close) {
 285             /* Send the guest closed notification if an app is interested */
 286             port->info->guest_close(port);
 287         }
 288         break;
 289     }
 290 }
 291
 292 static void control_in(VirtIODevice *vdev, VirtQueue *vq)
 293 {
 294 }
 295
 296 static void control_out(VirtIODevice *vdev, VirtQueue *vq)
 297 {
 298     VirtQueueElement elem;
 299     VirtIOSerial *vser;
 300
 301     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
 302
 303     while (virtqueue_pop(vq, &elem)) {
 304         handle_control_message(vser, elem.out_sg[0].iov_base);
 305         virtqueue_push(vq, &elem, elem.out_sg[0].iov_len);
 306     }
 307     virtio_notify(vdev, vq);
 308 }
 309
 310 /* Guest wrote something to some port. */
 311 static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
 312 {
 313     VirtIOSerial *vser;
 314     VirtQueueElement elem;
 315
 316     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
 317
 318     while (virtqueue_pop(vq, &elem)) {
 319         VirtIOSerialPort *port;
 320         size_t ret;
 321
 322         port = find_port_by_vq(vser, vq);
 323         if (!port) {
 324             ret = 0;
 325             goto next_buf;
 326         }
 327
 328         /*
 329          * A port may not have any handler registered for consuming the
 330          * data that the guest sends or it may not have a chardev associated
 331          * with it. Just ignore the data in that case.
 332          */
 333         if (!port->info->have_data) {
 334             ret = 0;
 335             goto next_buf;
 336         }
 337
 338         /* The guest always sends only one sg */
 339         ret = port->info->have_data(port, elem.out_sg[0].iov_base,
 340                                     elem.out_sg[0].iov_len);
 341
 342     next_buf:
 343         virtqueue_push(vq, &elem, ret);
 344     }
 345     virtio_notify(vdev, vq);
 346 }
 347
 348 static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
 349 {
 350 }
 351
 352 static uint32_t get_features(VirtIODevice *vdev, uint32_t features)
 353 {
 354     VirtIOSerial *vser;
 355
 356     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
 357
 358     if (vser->bus->max_nr_ports > 1) {
 359         features |= (1 << VIRTIO_CONSOLE_F_MULTIPORT);
 360     }
 361     return features;
 362 }
 363
 364 /* Guest requested config info */
 365 static void get_config(VirtIODevice *vdev, uint8_t *config_data)
 366 {
 367     VirtIOSerial *vser;
 368
 369     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
 370     memcpy(config_data, &vser->config, sizeof(struct virtio_console_config));
 371 }
 372
 373 static void set_config(VirtIODevice *vdev, const uint8_t *config_data)
 374 {
 375     struct virtio_console_config config;
 376
 377     memcpy(&config, config_data, sizeof(config));
 378 }
 379
 380 static void virtio_serial_save(QEMUFile *f, void *opaque)
 381 {
 382     VirtIOSerial *s = opaque;
 383     VirtIOSerialPort *port;
 384     uint32_t nr_active_ports;
 385     unsigned int i;
 386
 387     /* The virtio device */
 388     virtio_save(&s->vdev, f);
 389
 390     /* The config space */
 391     qemu_put_be16s(f, &s->config.cols);
 392     qemu_put_be16s(f, &s->config.rows);
 393
 394     qemu_put_be32s(f, &s->config.max_nr_ports);
 395
 396     /* The ports map */
 397
 398     for (i = 0; i < (s->config.max_nr_ports + 31) / 32; i++) {
 399         qemu_put_be32s(f, &s->ports_map[i]);
 400     }
 401
 402     /* Ports */
 403
 404     nr_active_ports = 0;
 405     QTAILQ_FOREACH(port, &s->ports, next) {
 406         nr_active_ports++;
 407     }
 408
 409     qemu_put_be32s(f, &nr_active_ports);
 410
 411     /*
 412      * Items in struct VirtIOSerialPort.
 413      */
 414     QTAILQ_FOREACH(port, &s->ports, next) {
 415         qemu_put_be32s(f, &port->id);
 416         qemu_put_byte(f, port->guest_connected);
 417         qemu_put_byte(f, port->host_connected);
 418     }
 419 }
 420
 421 static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)
 422 {
 423     VirtIOSerial *s = opaque;
 424     VirtIOSerialPort *port;
 425     size_t ports_map_size;
 426     uint32_t max_nr_ports, nr_active_ports, *ports_map;
 427     unsigned int i;
 428
 429     if (version_id > 2) {
 430         return -EINVAL;
 431     }
 432
 433     /* The virtio device */
 434     virtio_load(&s->vdev, f);
 435
 436     if (version_id < 2) {
 437         return 0;
 438     }
 439
 440     /* The config space */
 441     qemu_get_be16s(f, &s->config.cols);
 442     qemu_get_be16s(f, &s->config.rows);
 443
 444     qemu_get_be32s(f, &max_nr_ports);
 445     if (max_nr_ports > s->config.max_nr_ports) {
 446         /* Source could have had more ports than us. Fail migration. */
 447         return -EINVAL;
 448     }
 449
 450     ports_map_size = sizeof(uint32_t) * (max_nr_ports + 31) / 32;
 451     ports_map = qemu_malloc(ports_map_size);
 452
 453     for (i = 0; i < (max_nr_ports + 31) / 32; i++) {
 454         qemu_get_be32s(f, &ports_map[i]);
 455
 456         if (ports_map[i] != s->ports_map[i]) {
 457             /*
 458              * Ports active on source and destination don't
 459              * match. Fail migration.
 460              */
 461             qemu_free(ports_map);
 462             return -EINVAL;
 463         }
 464     }
 465     qemu_free(ports_map);
 466
 467     qemu_get_be32s(f, &nr_active_ports);
 468
 469     /* Items in struct VirtIOSerialPort */
 470     for (i = 0; i < nr_active_ports; i++) {
 471         uint32_t id;
 472         bool host_connected;
 473
 474         id = qemu_get_be32(f);
 475         port = find_port_by_id(s, id);
 476
 477         port->guest_connected = qemu_get_byte(f);
 478         host_connected = qemu_get_byte(f);
 479         if (host_connected != port->host_connected) {
 480             /*
 481              * We have to let the guest know of the host connection
 482              * status change
 483              */
 484             send_control_event(port, VIRTIO_CONSOLE_PORT_OPEN,
 485                                port->host_connected);
 486         }
 487     }
 488     return 0;
 489 }
 490
 491 static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
 492
 493 static struct BusInfo virtser_bus_info = {
 494     .name      = "virtio-serial-bus",
 495     .size      = sizeof(VirtIOSerialBus),
 496     .print_dev = virtser_bus_dev_print,
 497 };
 498
 499 static VirtIOSerialBus *virtser_bus_new(DeviceState *dev)
 500 {
 501     VirtIOSerialBus *bus;
 502
 503     bus = FROM_QBUS(VirtIOSerialBus, qbus_create(&virtser_bus_info, dev, NULL));
 504     bus->qbus.allow_hotplug = 1;
 505
 506     return bus;
 507 }
 508
 509 static void virtser_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent)
 510 {
 511     VirtIOSerialDevice *dev = DO_UPCAST(VirtIOSerialDevice, qdev, qdev);
 512     VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, &dev->qdev);
 513
 514     monitor_printf(mon, "%*s dev-prop-int: id: %u\n",
 515                    indent, "", port->id);
 516     monitor_printf(mon, "%*s dev-prop-int: guest_connected: %d\n",
 517                    indent, "", port->guest_connected);
 518     monitor_printf(mon, "%*s dev-prop-int: host_connected: %d\n",
 519                    indent, "", port->host_connected);
 520 }
 521
 522 /* This function is only used if a port id is not provided by the user */
 523 static uint32_t find_free_port_id(VirtIOSerial *vser)
 524 {
 525     unsigned int i;
 526
 527     for (i = 0; i < (vser->config.max_nr_ports + 31) / 32; i++) {
 528         uint32_t map, bit;
 529
 530         map = vser->ports_map[i];
 531         bit = ffs(~map);
 532         if (bit) {
 533             return (bit - 1) + i * 32;
 534         }
 535     }
 536     return VIRTIO_CONSOLE_BAD_ID;
 537 }
 538
 539 static void mark_port_added(VirtIOSerial *vser, uint32_t port_id)
 540 {
 541     unsigned int i;
 542
 543     i = port_id / 32;
 544     vser->ports_map[i] |= 1U << (port_id % 32);
 545 }
 546
 547 static void add_port(VirtIOSerial *vser, uint32_t port_id)
 548 {
 549     mark_port_added(vser, port_id);
 550
 551     send_control_event(find_port_by_id(vser, port_id),
 552                        VIRTIO_CONSOLE_PORT_ADD, 1);
 553 }
 554
 555 static void remove_port(VirtIOSerial *vser, uint32_t port_id)
 556 {
 557     unsigned int i;
 558
 559     i = port_id / 32;
 560     vser->ports_map[i] &= ~(1U << (port_id % 32));
 561
 562     send_control_event(find_port_by_id(vser, port_id),
 563                        VIRTIO_CONSOLE_PORT_REMOVE, 1);
 564 }
 565
 566 static int virtser_port_qdev_init(DeviceState *qdev, DeviceInfo *base)
 567 {
 568     VirtIOSerialDevice *dev = DO_UPCAST(VirtIOSerialDevice, qdev, qdev);
 569     VirtIOSerialPortInfo *info = DO_UPCAST(VirtIOSerialPortInfo, qdev, base);
 570     VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, &dev->qdev);
 571     VirtIOSerialBus *bus = DO_UPCAST(VirtIOSerialBus, qbus, qdev->parent_bus);
 572     int ret;
 573     bool plugging_port0;
 574
 575     port->vser = bus->vser;
 576
 577     /*
 578      * Is the first console port we're seeing? If so, put it up at
 579      * location 0. This is done for backward compatibility (old
 580      * kernel, new qemu).
 581      */
 582     plugging_port0 = port->is_console && !find_port_by_id(port->vser, 0);
 583
 584     if (find_port_by_id(port->vser, port->id)) {
 585         error_report("virtio-serial-bus: A port already exists at id %u\n",
 586                      port->id);
 587         return -1;
 588     }
 589
 590     if (port->id == VIRTIO_CONSOLE_BAD_ID) {
 591         if (plugging_port0) {
 592             port->id = 0;
 593         } else {
 594             port->id = find_free_port_id(port->vser);
 595             if (port->id == VIRTIO_CONSOLE_BAD_ID) {
 596                 error_report("virtio-serial-bus: Maximum port limit for this device reached\n");
 597                 return -1;
 598             }
 599         }
 600     }
 601
 602     if (port->id >= port->vser->config.max_nr_ports) {
 603         error_report("virtio-serial-bus: Out-of-range port id specified, max. allowed: %u\n",
 604                      port->vser->config.max_nr_ports - 1);
 605         return -1;
 606     }
 607
 608     dev->info = info;
 609     ret = info->init(dev);
 610     if (ret) {
 611         return ret;
 612     }
 613
 614     if (!use_multiport(port->vser)) {
 615         /*
 616          * Allow writes to guest in this case; we have no way of
 617          * knowing if a guest port is connected.
 618          */
 619         port->guest_connected = true;
 620     }
 621
 622     QTAILQ_INSERT_TAIL(&port->vser->ports, port, next);
 623     port->ivq = port->vser->ivqs[port->id];
 624     port->ovq = port->vser->ovqs[port->id];
 625
 626     add_port(port->vser, port->id);
 627
 628     /* Send an update to the guest about this new port added */
 629     virtio_notify_config(&port->vser->vdev);
 630
 631     return ret;
 632 }
 633
 634 static int virtser_port_qdev_exit(DeviceState *qdev)
 635 {
 636     VirtIOSerialDevice *dev = DO_UPCAST(VirtIOSerialDevice, qdev, qdev);
 637     VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, &dev->qdev);
 638     VirtIOSerial *vser = port->vser;
 639
 640     remove_port(port->vser, port->id);
 641
 642     QTAILQ_REMOVE(&vser->ports, port, next);
 643
 644     if (port->info->exit)
 645         port->info->exit(dev);
 646
 647     return 0;
 648 }
 649
 650 void virtio_serial_port_qdev_register(VirtIOSerialPortInfo *info)
 651 {
 652     info->qdev.init = virtser_port_qdev_init;
 653     info->qdev.bus_info = &virtser_bus_info;
 654     info->qdev.exit = virtser_port_qdev_exit;
 655     info->qdev.unplug = qdev_simple_unplug_cb;
 656     qdev_register(&info->qdev);
 657 }
 658
 659 VirtIODevice *virtio_serial_init(DeviceState *dev, uint32_t max_nr_ports)
 660 {
 661     VirtIOSerial *vser;
 662     VirtIODevice *vdev;
 663     uint32_t i;
 664
 665     if (!max_nr_ports)
 666         return NULL;
 667
 668     vdev = virtio_common_init("virtio-serial", VIRTIO_ID_CONSOLE,
 669                               sizeof(struct virtio_console_config),
 670                               sizeof(VirtIOSerial));
 671
 672     vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
 673
 674     /* Spawn a new virtio-serial bus on which the ports will ride as devices */
 675     vser->bus = virtser_bus_new(dev);
 676     vser->bus->vser = vser;
 677     QTAILQ_INIT(&vser->ports);
 678
 679     vser->bus->max_nr_ports = max_nr_ports;
 680     vser->ivqs = qemu_malloc(max_nr_ports * sizeof(VirtQueue *));
 681     vser->ovqs = qemu_malloc(max_nr_ports * sizeof(VirtQueue *));
 682
 683     /* Add a queue for host to guest transfers for port 0 (backward compat) */
 684     vser->ivqs[0] = virtio_add_queue(vdev, 128, handle_input);
 685     /* Add a queue for guest to host transfers for port 0 (backward compat) */
 686     vser->ovqs[0] = virtio_add_queue(vdev, 128, handle_output);
 687
 688     /* control queue: host to guest */
 689     vser->c_ivq = virtio_add_queue(vdev, 16, control_in);
 690     /* control queue: guest to host */
 691     vser->c_ovq = virtio_add_queue(vdev, 16, control_out);
 692
 693     for (i = 1; i < vser->bus->max_nr_ports; i++) {
 694         /* Add a per-port queue for host to guest transfers */
 695         vser->ivqs[i] = virtio_add_queue(vdev, 128, handle_input);
 696         /* Add a per-per queue for guest to host transfers */
 697         vser->ovqs[i] = virtio_add_queue(vdev, 128, handle_output);
 698     }
 699
 700     vser->config.max_nr_ports = max_nr_ports;
 701     vser->ports_map = qemu_mallocz((max_nr_ports + 31) / 32);
 702     /*
 703      * Reserve location 0 for a console port for backward compat
 704      * (old kernel, new qemu)
 705      */
 706     mark_port_added(vser, 0);
 707
 708     vser->vdev.get_features = get_features;
 709     vser->vdev.get_config = get_config;
 710     vser->vdev.set_config = set_config;
 711
 712     /*
 713      * Register for the savevm section with the virtio-console name
 714      * to preserve backward compat
 715      */
 716     register_savevm("virtio-console", -1, 2, virtio_serial_save,
 717                     virtio_serial_load, vser);
 718
 719     return vdev;
 720 }