qemu/hw/virtio-net.c

762 lines
21 KiB
C

/*
* Virtio Network Device
*
* Copyright IBM, Corp. 2007
*
* Authors:
* Anthony Liguori <aliguori@us.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 "virtio.h"
#include "net.h"
#include "qemu-timer.h"
#include "virtio-net.h"
#define VIRTIO_NET_VM_VERSION 10
#define MAC_TABLE_ENTRIES 64
#define MAX_VLAN (1 << 12) /* Per 802.1Q definition */
typedef struct VirtIONet
{
VirtIODevice vdev;
uint8_t mac[ETH_ALEN];
uint16_t status;
VirtQueue *rx_vq;
VirtQueue *tx_vq;
VirtQueue *ctrl_vq;
VLANClientState *vc;
QEMUTimer *tx_timer;
int tx_timer_active;
struct {
VirtQueueElement elem;
ssize_t len;
} async_tx;
int mergeable_rx_bufs;
uint8_t promisc;
uint8_t allmulti;
uint8_t alluni;
uint8_t nomulti;
uint8_t nouni;
uint8_t nobcast;
struct {
int in_use;
int first_multi;
uint8_t multi_overflow;
uint8_t uni_overflow;
uint8_t *macs;
} mac_table;
uint32_t *vlans;
} VirtIONet;
/* TODO
* - we could suppress RX interrupt if we were so inclined.
*/
static VirtIONet *to_virtio_net(VirtIODevice *vdev)
{
return (VirtIONet *)vdev;
}
static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config)
{
VirtIONet *n = to_virtio_net(vdev);
struct virtio_net_config netcfg;
netcfg.status = n->status;
memcpy(netcfg.mac, n->mac, ETH_ALEN);
memcpy(config, &netcfg, sizeof(netcfg));
}
static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config)
{
VirtIONet *n = to_virtio_net(vdev);
struct virtio_net_config netcfg;
memcpy(&netcfg, config, sizeof(netcfg));
if (memcmp(netcfg.mac, n->mac, ETH_ALEN)) {
memcpy(n->mac, netcfg.mac, ETH_ALEN);
qemu_format_nic_info_str(n->vc, n->mac);
}
}
static void virtio_net_set_link_status(VLANClientState *vc)
{
VirtIONet *n = vc->opaque;
uint16_t old_status = n->status;
if (vc->link_down)
n->status &= ~VIRTIO_NET_S_LINK_UP;
else
n->status |= VIRTIO_NET_S_LINK_UP;
if (n->status != old_status)
virtio_notify_config(&n->vdev);
}
static void virtio_net_reset(VirtIODevice *vdev)
{
VirtIONet *n = to_virtio_net(vdev);
/* Reset back to compatibility mode */
n->promisc = 1;
n->allmulti = 0;
n->alluni = 0;
n->nomulti = 0;
n->nouni = 0;
n->nobcast = 0;
/* Flush any MAC and VLAN filter table state */
n->mac_table.in_use = 0;
n->mac_table.first_multi = 0;
n->mac_table.multi_overflow = 0;
n->mac_table.uni_overflow = 0;
memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
memset(n->vlans, 0, MAX_VLAN >> 3);
}
static uint32_t virtio_net_get_features(VirtIODevice *vdev)
{
uint32_t features = (1 << VIRTIO_NET_F_MAC) |
(1 << VIRTIO_NET_F_MRG_RXBUF) |
(1 << VIRTIO_NET_F_STATUS) |
(1 << VIRTIO_NET_F_CTRL_VQ) |
(1 << VIRTIO_NET_F_CTRL_RX) |
(1 << VIRTIO_NET_F_CTRL_VLAN) |
(1 << VIRTIO_NET_F_CTRL_RX_EXTRA);
return features;
}
static uint32_t virtio_net_bad_features(VirtIODevice *vdev)
{
uint32_t features = 0;
/* Linux kernel 2.6.25. It understood MAC (as everyone must),
* but also these: */
features |= (1 << VIRTIO_NET_F_MAC);
features |= (1 << VIRTIO_NET_F_GUEST_CSUM);
features |= (1 << VIRTIO_NET_F_GUEST_TSO4);
features |= (1 << VIRTIO_NET_F_GUEST_TSO6);
features |= (1 << VIRTIO_NET_F_GUEST_ECN);
return features & virtio_net_get_features(vdev);
}
static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
{
VirtIONet *n = to_virtio_net(vdev);
n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
}
static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
VirtQueueElement *elem)
{
uint8_t on;
if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(on)) {
fprintf(stderr, "virtio-net ctrl invalid rx mode command\n");
exit(1);
}
on = ldub_p(elem->out_sg[1].iov_base);
if (cmd == VIRTIO_NET_CTRL_RX_MODE_PROMISC)
n->promisc = on;
else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLMULTI)
n->allmulti = on;
else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLUNI)
n->alluni = on;
else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOMULTI)
n->nomulti = on;
else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOUNI)
n->nouni = on;
else if (cmd == VIRTIO_NET_CTRL_RX_MODE_NOBCAST)
n->nobcast = on;
else
return VIRTIO_NET_ERR;
return VIRTIO_NET_OK;
}
static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
VirtQueueElement *elem)
{
struct virtio_net_ctrl_mac mac_data;
if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET || elem->out_num != 3 ||
elem->out_sg[1].iov_len < sizeof(mac_data) ||
elem->out_sg[2].iov_len < sizeof(mac_data))
return VIRTIO_NET_ERR;
n->mac_table.in_use = 0;
n->mac_table.first_multi = 0;
n->mac_table.uni_overflow = 0;
n->mac_table.multi_overflow = 0;
memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
mac_data.entries = ldl_le_p(elem->out_sg[1].iov_base);
if (sizeof(mac_data.entries) +
(mac_data.entries * ETH_ALEN) > elem->out_sg[1].iov_len)
return VIRTIO_NET_ERR;
if (mac_data.entries <= MAC_TABLE_ENTRIES) {
memcpy(n->mac_table.macs, elem->out_sg[1].iov_base + sizeof(mac_data),
mac_data.entries * ETH_ALEN);
n->mac_table.in_use += mac_data.entries;
} else {
n->mac_table.uni_overflow = 1;
}
n->mac_table.first_multi = n->mac_table.in_use;
mac_data.entries = ldl_le_p(elem->out_sg[2].iov_base);
if (sizeof(mac_data.entries) +
(mac_data.entries * ETH_ALEN) > elem->out_sg[2].iov_len)
return VIRTIO_NET_ERR;
if (mac_data.entries) {
if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
memcpy(n->mac_table.macs + (n->mac_table.in_use * ETH_ALEN),
elem->out_sg[2].iov_base + sizeof(mac_data),
mac_data.entries * ETH_ALEN);
n->mac_table.in_use += mac_data.entries;
} else {
n->mac_table.multi_overflow = 1;
}
}
return VIRTIO_NET_OK;
}
static int virtio_net_handle_vlan_table(VirtIONet *n, uint8_t cmd,
VirtQueueElement *elem)
{
uint16_t vid;
if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(vid)) {
fprintf(stderr, "virtio-net ctrl invalid vlan command\n");
return VIRTIO_NET_ERR;
}
vid = lduw_le_p(elem->out_sg[1].iov_base);
if (vid >= MAX_VLAN)
return VIRTIO_NET_ERR;
if (cmd == VIRTIO_NET_CTRL_VLAN_ADD)
n->vlans[vid >> 5] |= (1U << (vid & 0x1f));
else if (cmd == VIRTIO_NET_CTRL_VLAN_DEL)
n->vlans[vid >> 5] &= ~(1U << (vid & 0x1f));
else
return VIRTIO_NET_ERR;
return VIRTIO_NET_OK;
}
static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIONet *n = to_virtio_net(vdev);
struct virtio_net_ctrl_hdr ctrl;
virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
VirtQueueElement elem;
while (virtqueue_pop(vq, &elem)) {
if ((elem.in_num < 1) || (elem.out_num < 1)) {
fprintf(stderr, "virtio-net ctrl missing headers\n");
exit(1);
}
if (elem.out_sg[0].iov_len < sizeof(ctrl) ||
elem.in_sg[elem.in_num - 1].iov_len < sizeof(status)) {
fprintf(stderr, "virtio-net ctrl header not in correct element\n");
exit(1);
}
ctrl.class = ldub_p(elem.out_sg[0].iov_base);
ctrl.cmd = ldub_p(elem.out_sg[0].iov_base + sizeof(ctrl.class));
if (ctrl.class == VIRTIO_NET_CTRL_RX_MODE)
status = virtio_net_handle_rx_mode(n, ctrl.cmd, &elem);
else if (ctrl.class == VIRTIO_NET_CTRL_MAC)
status = virtio_net_handle_mac(n, ctrl.cmd, &elem);
else if (ctrl.class == VIRTIO_NET_CTRL_VLAN)
status = virtio_net_handle_vlan_table(n, ctrl.cmd, &elem);
stb_p(elem.in_sg[elem.in_num - 1].iov_base, status);
virtqueue_push(vq, &elem, sizeof(status));
virtio_notify(vdev, vq);
}
}
/* RX */
static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIONet *n = to_virtio_net(vdev);
qemu_flush_queued_packets(n->vc);
/* We now have RX buffers, signal to the IO thread to break out of the
* select to re-poll the tap file descriptor */
qemu_notify_event();
}
static int do_virtio_net_can_receive(VirtIONet *n, int bufsize)
{
if (!virtio_queue_ready(n->rx_vq) ||
!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
return 0;
if (virtio_queue_empty(n->rx_vq) ||
(n->mergeable_rx_bufs &&
!virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) {
virtio_queue_set_notification(n->rx_vq, 1);
return 0;
}
virtio_queue_set_notification(n->rx_vq, 0);
return 1;
}
static int virtio_net_can_receive(VLANClientState *vc)
{
VirtIONet *n = vc->opaque;
return do_virtio_net_can_receive(n, VIRTIO_NET_MAX_BUFSIZE);
}
static int iov_fill(struct iovec *iov, int iovcnt, const void *buf, int count)
{
int offset, i;
offset = i = 0;
while (offset < count && i < iovcnt) {
int len = MIN(iov[i].iov_len, count - offset);
memcpy(iov[i].iov_base, buf + offset, len);
offset += len;
i++;
}
return offset;
}
static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt,
const void *buf, size_t size, size_t hdr_len)
{
struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base;
int offset = 0;
hdr->flags = 0;
hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
/* We only ever receive a struct virtio_net_hdr from the tapfd,
* but we may be passing along a larger header to the guest.
*/
iov[0].iov_base += hdr_len;
iov[0].iov_len -= hdr_len;
return offset;
}
static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
{
static const uint8_t bcast[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
static const uint8_t vlan[] = {0x81, 0x00};
uint8_t *ptr = (uint8_t *)buf;
int i;
if (n->promisc)
return 1;
if (!memcmp(&ptr[12], vlan, sizeof(vlan))) {
int vid = be16_to_cpup((uint16_t *)(ptr + 14)) & 0xfff;
if (!(n->vlans[vid >> 5] & (1U << (vid & 0x1f))))
return 0;
}
if (ptr[0] & 1) { // multicast
if (!memcmp(ptr, bcast, sizeof(bcast))) {
return !n->nobcast;
} else if (n->nomulti) {
return 0;
} else if (n->allmulti || n->mac_table.multi_overflow) {
return 1;
}
for (i = n->mac_table.first_multi; i < n->mac_table.in_use; i++) {
if (!memcmp(ptr, &n->mac_table.macs[i * ETH_ALEN], ETH_ALEN)) {
return 1;
}
}
} else { // unicast
if (n->nouni) {
return 0;
} else if (n->alluni || n->mac_table.uni_overflow) {
return 1;
} else if (!memcmp(ptr, n->mac, ETH_ALEN)) {
return 1;
}
for (i = 0; i < n->mac_table.first_multi; i++) {
if (!memcmp(ptr, &n->mac_table.macs[i * ETH_ALEN], ETH_ALEN)) {
return 1;
}
}
}
return 0;
}
static ssize_t virtio_net_receive(VLANClientState *vc, const uint8_t *buf, size_t size)
{
VirtIONet *n = vc->opaque;
struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL;
size_t hdr_len, offset, i;
if (!do_virtio_net_can_receive(n, size))
return 0;
if (!receive_filter(n, buf, size))
return size;
/* hdr_len refers to the header we supply to the guest */
hdr_len = n->mergeable_rx_bufs ?
sizeof(struct virtio_net_hdr_mrg_rxbuf) : sizeof(struct virtio_net_hdr);
offset = i = 0;
while (offset < size) {
VirtQueueElement elem;
int len, total;
struct iovec sg[VIRTQUEUE_MAX_SIZE];
len = total = 0;
if ((i != 0 && !n->mergeable_rx_bufs) ||
virtqueue_pop(n->rx_vq, &elem) == 0) {
if (i == 0)
return -1;
fprintf(stderr, "virtio-net truncating packet\n");
exit(1);
}
if (elem.in_num < 1) {
fprintf(stderr, "virtio-net receive queue contains no in buffers\n");
exit(1);
}
if (!n->mergeable_rx_bufs && elem.in_sg[0].iov_len != hdr_len) {
fprintf(stderr, "virtio-net header not in first element\n");
exit(1);
}
memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num);
if (i == 0) {
if (n->mergeable_rx_bufs)
mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base;
offset += receive_header(n, sg, elem.in_num,
buf + offset, size - offset, hdr_len);
total += hdr_len;
}
/* copy in packet. ugh */
len = iov_fill(sg, elem.in_num,
buf + offset, size - offset);
total += len;
/* signal other side */
virtqueue_fill(n->rx_vq, &elem, total, i++);
offset += len;
}
if (mhdr)
mhdr->num_buffers = i;
virtqueue_flush(n->rx_vq, i);
virtio_notify(&n->vdev, n->rx_vq);
return size;
}
static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq);
static void virtio_net_tx_complete(VLANClientState *vc, ssize_t len)
{
VirtIONet *n = vc->opaque;
virtqueue_push(n->tx_vq, &n->async_tx.elem, n->async_tx.len);
virtio_notify(&n->vdev, n->tx_vq);
n->async_tx.elem.out_num = n->async_tx.len = 0;
virtio_queue_set_notification(n->tx_vq, 1);
virtio_net_flush_tx(n, n->tx_vq);
}
/* TX */
static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq)
{
VirtQueueElement elem;
int has_vnet_hdr = 0;
if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
return;
if (n->async_tx.elem.out_num) {
virtio_queue_set_notification(n->tx_vq, 0);
return;
}
while (virtqueue_pop(vq, &elem)) {
ssize_t ret, len = 0;
unsigned int out_num = elem.out_num;
struct iovec *out_sg = &elem.out_sg[0];
unsigned hdr_len;
/* hdr_len refers to the header received from the guest */
hdr_len = n->mergeable_rx_bufs ?
sizeof(struct virtio_net_hdr_mrg_rxbuf) :
sizeof(struct virtio_net_hdr);
if (out_num < 1 || out_sg->iov_len != hdr_len) {
fprintf(stderr, "virtio-net header not in first element\n");
exit(1);
}
/* ignore the header if GSO is not supported */
if (!has_vnet_hdr) {
out_num--;
out_sg++;
len += hdr_len;
} else if (n->mergeable_rx_bufs) {
/* tapfd expects a struct virtio_net_hdr */
hdr_len -= sizeof(struct virtio_net_hdr);
out_sg->iov_len -= hdr_len;
len += hdr_len;
}
ret = qemu_sendv_packet_async(n->vc, out_sg, out_num,
virtio_net_tx_complete);
if (ret == 0) {
virtio_queue_set_notification(n->tx_vq, 0);
n->async_tx.elem = elem;
n->async_tx.len = len;
return;
}
len += ret;
virtqueue_push(vq, &elem, len);
virtio_notify(&n->vdev, vq);
}
}
static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIONet *n = to_virtio_net(vdev);
if (n->tx_timer_active) {
virtio_queue_set_notification(vq, 1);
qemu_del_timer(n->tx_timer);
n->tx_timer_active = 0;
virtio_net_flush_tx(n, vq);
} else {
qemu_mod_timer(n->tx_timer,
qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
n->tx_timer_active = 1;
virtio_queue_set_notification(vq, 0);
}
}
static void virtio_net_tx_timer(void *opaque)
{
VirtIONet *n = opaque;
n->tx_timer_active = 0;
/* Just in case the driver is not ready on more */
if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
return;
virtio_queue_set_notification(n->tx_vq, 1);
virtio_net_flush_tx(n, n->tx_vq);
}
static void virtio_net_save(QEMUFile *f, void *opaque)
{
VirtIONet *n = opaque;
virtio_save(&n->vdev, f);
qemu_put_buffer(f, n->mac, ETH_ALEN);
qemu_put_be32(f, n->tx_timer_active);
qemu_put_be32(f, n->mergeable_rx_bufs);
qemu_put_be16(f, n->status);
qemu_put_byte(f, n->promisc);
qemu_put_byte(f, n->allmulti);
qemu_put_be32(f, n->mac_table.in_use);
qemu_put_buffer(f, n->mac_table.macs, n->mac_table.in_use * ETH_ALEN);
qemu_put_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);
qemu_put_be32(f, 0); /* vnet-hdr placeholder */
qemu_put_byte(f, n->mac_table.multi_overflow);
qemu_put_byte(f, n->mac_table.uni_overflow);
qemu_put_byte(f, n->alluni);
qemu_put_byte(f, n->nomulti);
qemu_put_byte(f, n->nouni);
qemu_put_byte(f, n->nobcast);
}
static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
{
VirtIONet *n = opaque;
int i;
if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
return -EINVAL;
virtio_load(&n->vdev, f);
qemu_get_buffer(f, n->mac, ETH_ALEN);
n->tx_timer_active = qemu_get_be32(f);
n->mergeable_rx_bufs = qemu_get_be32(f);
if (version_id >= 3)
n->status = qemu_get_be16(f);
if (version_id >= 4) {
if (version_id < 8) {
n->promisc = qemu_get_be32(f);
n->allmulti = qemu_get_be32(f);
} else {
n->promisc = qemu_get_byte(f);
n->allmulti = qemu_get_byte(f);
}
}
if (version_id >= 5) {
n->mac_table.in_use = qemu_get_be32(f);
/* MAC_TABLE_ENTRIES may be different from the saved image */
if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) {
qemu_get_buffer(f, n->mac_table.macs,
n->mac_table.in_use * ETH_ALEN);
} else if (n->mac_table.in_use) {
qemu_fseek(f, n->mac_table.in_use * ETH_ALEN, SEEK_CUR);
n->mac_table.multi_overflow = n->mac_table.uni_overflow = 1;
n->mac_table.in_use = 0;
}
}
if (version_id >= 6)
qemu_get_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);
if (version_id >= 7 && qemu_get_be32(f)) {
fprintf(stderr,
"virtio-net: saved image requires vnet header support\n");
exit(1);
}
if (version_id >= 9) {
n->mac_table.multi_overflow = qemu_get_byte(f);
n->mac_table.uni_overflow = qemu_get_byte(f);
}
if (version_id >= 10) {
n->alluni = qemu_get_byte(f);
n->nomulti = qemu_get_byte(f);
n->nouni = qemu_get_byte(f);
n->nobcast = qemu_get_byte(f);
}
/* Find the first multicast entry in the saved MAC filter */
for (i = 0; i < n->mac_table.in_use; i++) {
if (n->mac_table.macs[i * ETH_ALEN] & 1) {
break;
}
}
n->mac_table.first_multi = i;
if (n->tx_timer_active) {
qemu_mod_timer(n->tx_timer,
qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
}
return 0;
}
static void virtio_net_cleanup(VLANClientState *vc)
{
VirtIONet *n = vc->opaque;
qemu_purge_queued_packets(vc);
unregister_savevm("virtio-net", n);
qemu_free(n->mac_table.macs);
qemu_free(n->vlans);
qemu_del_timer(n->tx_timer);
qemu_free_timer(n->tx_timer);
virtio_cleanup(&n->vdev);
}
VirtIODevice *virtio_net_init(DeviceState *dev)
{
VirtIONet *n;
static int virtio_net_id;
n = (VirtIONet *)virtio_common_init("virtio-net", VIRTIO_ID_NET,
sizeof(struct virtio_net_config),
sizeof(VirtIONet));
n->vdev.get_config = virtio_net_get_config;
n->vdev.set_config = virtio_net_set_config;
n->vdev.get_features = virtio_net_get_features;
n->vdev.set_features = virtio_net_set_features;
n->vdev.bad_features = virtio_net_bad_features;
n->vdev.reset = virtio_net_reset;
n->rx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_rx);
n->tx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_tx);
n->ctrl_vq = virtio_add_queue(&n->vdev, 64, virtio_net_handle_ctrl);
qdev_get_macaddr(dev, n->mac);
n->status = VIRTIO_NET_S_LINK_UP;
n->vc = qdev_get_vlan_client(dev,
virtio_net_can_receive,
virtio_net_receive, NULL,
virtio_net_cleanup, n);
n->vc->link_status_changed = virtio_net_set_link_status;
qemu_format_nic_info_str(n->vc, n->mac);
n->tx_timer = qemu_new_timer(vm_clock, virtio_net_tx_timer, n);
n->tx_timer_active = 0;
n->mergeable_rx_bufs = 0;
n->promisc = 1; /* for compatibility */
n->mac_table.macs = qemu_mallocz(MAC_TABLE_ENTRIES * ETH_ALEN);
n->vlans = qemu_mallocz(MAX_VLAN >> 3);
if (dev->nd->nvectors == NIC_NVECTORS_UNSPECIFIED)
n->vdev.nvectors = 3;
else
n->vdev.nvectors = dev->nd->nvectors;
register_savevm("virtio-net", virtio_net_id++, VIRTIO_NET_VM_VERSION,
virtio_net_save, virtio_net_load, n);
return &n->vdev;
}