virtio_net.c

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/* A network driver using virtio.
 *
 * Copyright 2007 Rusty Russell <[email protected]> IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
//#define DEBUG
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/virtio.h>
#include <linux/virtio_net.h>
#include <linux/scatterlist.h>
#include <linux/if_vlan.h>
#include <linux/slab.h>

static int napi_weight = 128;
module_param(napi_weight, int, 0444);

static bool csum = true, gso = true;
module_param(csum, bool, 0444);
module_param(gso, bool, 0444);

/* FIXME: MTU in config. */
#define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
#define GOOD_COPY_LEN   128

#define VIRTNET_SEND_COMMAND_SG_MAX    2
#define VIRTNET_DRIVER_VERSION "1.0.0"

struct virtnet_stats {
    struct u64_stats_sync tx_syncp;
    struct u64_stats_sync rx_syncp;
    u64 tx_bytes;
    u64 tx_packets;

    u64 rx_bytes;
    u64 rx_packets;
};

struct virtnet_info {
    struct virtio_device *vdev;
    struct virtqueue *rvq, *svq, *cvq;
    struct net_device *dev;
    struct napi_struct napi;
    unsigned int status;

    /* Number of input buffers, and max we've ever had. */
    unsigned int num, max;

    /* I like... big packets and I cannot lie! */
    bool big_packets;

    /* Host will merge rx buffers for big packets (shake it! shake it!) */
    bool mergeable_rx_bufs;

    /* enable config space updates */
    bool config_enable;

    /* Active statistics */
    struct virtnet_stats __percpu *stats;

    /* Work struct for refilling if we run low on memory. */
    struct delayed_work refill;

    /* Work struct for config space updates */
    struct work_struct config_work;

    /* Lock for config space updates */
    struct mutex config_lock;

    /* Chain pages by the private ptr. */
    struct page *pages;

    /* fragments + linear part + virtio header */
    struct scatterlist rx_sg[MAX_SKB_FRAGS + 2];
    struct scatterlist tx_sg[MAX_SKB_FRAGS + 2];
};

struct skb_vnet_hdr {
    union {
        struct virtio_net_hdr hdr;
        struct virtio_net_hdr_mrg_rxbuf mhdr;
    };
    unsigned int num_sg;
};

struct padded_vnet_hdr {
    struct virtio_net_hdr hdr;
    /*
     * virtio_net_hdr should be in a separated sg buffer because of a
     * QEMU bug, and data sg buffer shares same page with this header sg.
     * This padding makes next sg 16 byte aligned after virtio_net_hdr.
     */
    char padding[6];
};

static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
{
    return (struct skb_vnet_hdr *)skb->cb;
}

/*
 * private is used to chain pages for big packets, put the whole
 * most recent used list in the beginning for reuse
 */
static void give_pages(struct virtnet_info *vi, struct page *page)
{
    struct page *end;

    /* Find end of list, sew whole thing into vi->pages. */
    for (end = page; end->private; end = (struct page *)end->private);
    end->private = (unsigned long)vi->pages;
    vi->pages = page;
}

static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
{
    struct page *p = vi->pages;

    if (p) {
        vi->pages = (struct page *)p->private;
        /* clear private here, it is used to chain pages */
        p->private = 0;
    } else
        p = alloc_page(gfp_mask);
    return p;
}

static void skb_xmit_done(struct virtqueue *svq)
{
    struct virtnet_info *vi = svq->vdev->priv;

    /* Suppress further interrupts. */
    virtqueue_disable_cb(svq);

    /* We were probably waiting for more output buffers. */
    netif_wake_queue(vi->dev);
}

static void set_skb_frag(struct sk_buff *skb, struct page *page,
             unsigned int offset, unsigned int *len)
{
    int size = min((unsigned)PAGE_SIZE - offset, *len);
    int i = skb_shinfo(skb)->nr_frags;

    __skb_fill_page_desc(skb, i, page, offset, size);

    skb->data_len += size;
    skb->len += size;
    skb->truesize += PAGE_SIZE;
    skb_shinfo(skb)->nr_frags++;
    *len -= size;
}

/* Called from bottom half context */
static struct sk_buff *page_to_skb(struct virtnet_info *vi,
                   struct page *page, unsigned int len)
{
    struct sk_buff *skb;
    struct skb_vnet_hdr *hdr;
    unsigned int copy, hdr_len, offset;
    char *p;

    p = page_address(page);

    /* copy small packet so we can reuse these pages for small data */
    skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN);
    if (unlikely(!skb))
        return NULL;

    hdr = skb_vnet_hdr(skb);

    if (vi->mergeable_rx_bufs) {
        hdr_len = sizeof hdr->mhdr;
        offset = hdr_len;
    } else {
        hdr_len = sizeof hdr->hdr;
        offset = sizeof(struct padded_vnet_hdr);
    }

    memcpy(hdr, p, hdr_len);

    len -= hdr_len;
    p += offset;

    copy = len;
    if (copy > skb_tailroom(skb))
        copy = skb_tailroom(skb);
    memcpy(skb_put(skb, copy), p, copy);

    len -= copy;
    offset += copy;

    /*
     * Verify that we can indeed put this data into a skb.
     * This is here to handle cases when the device erroneously
     * tries to receive more than is possible. This is usually
     * the case of a broken device.
     */
    if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
        if (net_ratelimit())
            pr_debug("%s: too much data\n", skb->dev->name);
        dev_kfree_skb(skb);
        return NULL;
    }

    while (len) {
        set_skb_frag(skb, page, offset, &len);
        page = (struct page *)page->private;
        offset = 0;
    }

    if (page)
        give_pages(vi, page);

    return skb;
}

static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
{
    struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
    struct page *page;
    int num_buf, i, len;

    num_buf = hdr->mhdr.num_buffers;
    while (--num_buf) {
        i = skb_shinfo(skb)->nr_frags;
        if (i >= MAX_SKB_FRAGS) {
            pr_debug("%s: packet too long\n", skb->dev->name);
            skb->dev->stats.rx_length_errors++;
            return -EINVAL;
        }
        page = virtqueue_get_buf(vi->rvq, &len);
        if (!page) {
            pr_debug("%s: rx error: %d buffers missing\n",
                 skb->dev->name, hdr->mhdr.num_buffers);
            skb->dev->stats.rx_length_errors++;
            return -EINVAL;
        }

        if (len > PAGE_SIZE)
            len = PAGE_SIZE;

        set_skb_frag(skb, page, 0, &len);

        --vi->num;
    }
    return 0;
}

static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
    struct sk_buff *skb;
    struct page *page;
    struct skb_vnet_hdr *hdr;

    if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
        pr_debug("%s: short packet %i\n", dev->name, len);
        dev->stats.rx_length_errors++;
        if (vi->mergeable_rx_bufs || vi->big_packets)
            give_pages(vi, buf);
        else
            dev_kfree_skb(buf);
        return;
    }

    if (!vi->mergeable_rx_bufs && !vi->big_packets) {
        skb = buf;
        len -= sizeof(struct virtio_net_hdr);
        skb_trim(skb, len);
    } else {
        page = buf;
        skb = page_to_skb(vi, page, len);
        if (unlikely(!skb)) {
            dev->stats.rx_dropped++;
            give_pages(vi, page);
            return;
        }
        if (vi->mergeable_rx_bufs)
            if (receive_mergeable(vi, skb)) {
                dev_kfree_skb(skb);
                return;
            }
    }

    hdr = skb_vnet_hdr(skb);

    u64_stats_update_begin(&stats->rx_syncp);
    stats->rx_bytes += skb->len;
    stats->rx_packets++;
    u64_stats_update_end(&stats->rx_syncp);

    if (hdr->hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
        pr_debug("Needs csum!\n");
        if (!skb_partial_csum_set(skb,
                      hdr->hdr.csum_start,
                      hdr->hdr.csum_offset))
            goto frame_err;
    } else if (hdr->hdr.flags & VIRTIO_NET_HDR_F_DATA_VALID) {
        skb->ip_summed = CHECKSUM_UNNECESSARY;
    }

    skb->protocol = eth_type_trans(skb, dev);
    pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
         ntohs(skb->protocol), skb->len, skb->pkt_type);

    if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
        pr_debug("GSO!\n");
        switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
        case VIRTIO_NET_HDR_GSO_TCPV4:
            skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
            break;
        case VIRTIO_NET_HDR_GSO_UDP:
            skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
            break;
        case VIRTIO_NET_HDR_GSO_TCPV6:
            skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
            break;
        default:
            if (net_ratelimit())
                printk(KERN_WARNING "%s: bad gso type %u.\n",
                       dev->name, hdr->hdr.gso_type);
            goto frame_err;
        }

        if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
            skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;

        skb_shinfo(skb)->gso_size = hdr->hdr.gso_size;
        if (skb_shinfo(skb)->gso_size == 0) {
            if (net_ratelimit())
                printk(KERN_WARNING "%s: zero gso size.\n",
                       dev->name);
            goto frame_err;
        }

        /* Header must be checked, and gso_segs computed. */
        skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
        skb_shinfo(skb)->gso_segs = 0;
    }

    netif_receive_skb(skb);
    return;

frame_err:
    dev->stats.rx_frame_errors++;
    dev_kfree_skb(skb);
}

static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
{
    struct sk_buff *skb;
    struct skb_vnet_hdr *hdr;
    int err;

    skb = __netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN, gfp);
    if (unlikely(!skb))
        return -ENOMEM;

    skb_put(skb, MAX_PACKET_LEN);

    hdr = skb_vnet_hdr(skb);
    sg_set_buf(vi->rx_sg, &hdr->hdr, sizeof hdr->hdr);

    skb_to_sgvec(skb, vi->rx_sg + 1, 0, skb->len);

    err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 2, skb, gfp);
    if (err < 0)
        dev_kfree_skb(skb);

    return err;
}

static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
{
    struct page *first, *list = NULL;
    char *p;
    int i, err, offset;

    /* page in vi->rx_sg[MAX_SKB_FRAGS + 1] is list tail */
    for (i = MAX_SKB_FRAGS + 1; i > 1; --i) {
        first = get_a_page(vi, gfp);
        if (!first) {
            if (list)
                give_pages(vi, list);
            return -ENOMEM;
        }
        sg_set_buf(&vi->rx_sg[i], page_address(first), PAGE_SIZE);

        /* chain new page in list head to match sg */
        first->private = (unsigned long)list;
        list = first;
    }

    first = get_a_page(vi, gfp);
    if (!first) {
        give_pages(vi, list);
        return -ENOMEM;
    }
    p = page_address(first);

    /* vi->rx_sg[0], vi->rx_sg[1] share the same page */
    /* a separated vi->rx_sg[0] for virtio_net_hdr only due to QEMU bug */
    sg_set_buf(&vi->rx_sg[0], p, sizeof(struct virtio_net_hdr));

    /* vi->rx_sg[1] for data packet, from offset */
    offset = sizeof(struct padded_vnet_hdr);
    sg_set_buf(&vi->rx_sg[1], p + offset, PAGE_SIZE - offset);

    /* chain first in list head */
    first->private = (unsigned long)list;
    err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, MAX_SKB_FRAGS + 2,
                first, gfp);
    if (err < 0)
        give_pages(vi, first);

    return err;
}

static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
{
    struct page *page;
    int err;

    page = get_a_page(vi, gfp);
    if (!page)
        return -ENOMEM;

    sg_init_one(vi->rx_sg, page_address(page), PAGE_SIZE);

    err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 1, page, gfp);
    if (err < 0)
        give_pages(vi, page);

    return err;
}

/*
 * Returns false if we couldn't fill entirely (OOM).
 *
 * Normally run in the receive path, but can also be run from ndo_open
 * before we're receiving packets, or from refill_work which is
 * careful to disable receiving (using napi_disable).
 */
static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
{
    int err;
    bool oom;

    do {
        if (vi->mergeable_rx_bufs)
            err = add_recvbuf_mergeable(vi, gfp);
        else if (vi->big_packets)
            err = add_recvbuf_big(vi, gfp);
        else
            err = add_recvbuf_small(vi, gfp);

        oom = err == -ENOMEM;
        if (err < 0)
            break;
        ++vi->num;
    } while (err > 0);
    if (unlikely(vi->num > vi->max))
        vi->max = vi->num;
    virtqueue_kick(vi->rvq);
    return !oom;
}

static void skb_recv_done(struct virtqueue *rvq)
{
    struct virtnet_info *vi = rvq->vdev->priv;
    /* Schedule NAPI, Suppress further interrupts if successful. */
    if (napi_schedule_prep(&vi->napi)) {
        virtqueue_disable_cb(rvq);
        __napi_schedule(&vi->napi);
    }
}

static void virtnet_napi_enable(struct virtnet_info *vi)
{
    napi_enable(&vi->napi);

    /* If all buffers were filled by other side before we napi_enabled, we
     * won't get another interrupt, so process any outstanding packets
     * now.  virtnet_poll wants re-enable the queue, so we disable here.
     * We synchronize against interrupts via NAPI_STATE_SCHED */
    if (napi_schedule_prep(&vi->napi)) {
        virtqueue_disable_cb(vi->rvq);
        local_bh_disable();
        __napi_schedule(&vi->napi);
        local_bh_enable();
    }
}

static void refill_work(struct work_struct *work)
{
    struct virtnet_info *vi;
    bool still_empty;

    vi = container_of(work, struct virtnet_info, refill.work);
    napi_disable(&vi->napi);
    still_empty = !try_fill_recv(vi, GFP_KERNEL);
    virtnet_napi_enable(vi);

    /* In theory, this can happen: if we don't get any buffers in
     * we will *never* try to fill again. */
    if (still_empty)
        schedule_delayed_work(&vi->refill, HZ/2);
}

static int virtnet_poll(struct napi_struct *napi, int budget)
{
    struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
    void *buf;
    unsigned int len, received = 0;

again:
    while (received < budget &&
           (buf = virtqueue_get_buf(vi->rvq, &len)) != NULL) {
        receive_buf(vi->dev, buf, len);
        --vi->num;
        received++;
    }

    if (vi->num < vi->max / 2) {
        if (!try_fill_recv(vi, GFP_ATOMIC))
            schedule_delayed_work(&vi->refill, 0);
    }

    /* Out of packets? */
    if (received < budget) {
        napi_complete(napi);
        if (unlikely(!virtqueue_enable_cb(vi->rvq)) &&
            napi_schedule_prep(napi)) {
            virtqueue_disable_cb(vi->rvq);
            __napi_schedule(napi);
            goto again;
        }
    }

    return received;
}

static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
{
    struct sk_buff *skb;
    unsigned int len, tot_sgs = 0;
    struct virtnet_stats *stats = this_cpu_ptr(vi->stats);

    while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) {
        pr_debug("Sent skb %p\n", skb);

        u64_stats_update_begin(&stats->tx_syncp);
        stats->tx_bytes += skb->len;
        stats->tx_packets++;
        u64_stats_update_end(&stats->tx_syncp);

        tot_sgs += skb_vnet_hdr(skb)->num_sg;
        dev_kfree_skb_any(skb);
    }
    return tot_sgs;
}

static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
{
    struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
    const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;

    pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);

    if (skb->ip_summed == CHECKSUM_PARTIAL) {
        hdr->hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
        hdr->hdr.csum_start = skb_checksum_start_offset(skb);
        hdr->hdr.csum_offset = skb->csum_offset;
    } else {
        hdr->hdr.flags = 0;
        hdr->hdr.csum_offset = hdr->hdr.csum_start = 0;
    }

    if (skb_is_gso(skb)) {
        hdr->hdr.hdr_len = skb_headlen(skb);
        hdr->hdr.gso_size = skb_shinfo(skb)->gso_size;
        if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
            hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
        else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
            hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
        else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
            hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_UDP;
        else
            BUG();
        if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
            hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_ECN;
    } else {
        hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
        hdr->hdr.gso_size = hdr->hdr.hdr_len = 0;
    }

    hdr->mhdr.num_buffers = 0;

    /* Encode metadata header at front. */
    if (vi->mergeable_rx_bufs)
        sg_set_buf(vi->tx_sg, &hdr->mhdr, sizeof hdr->mhdr);
    else
        sg_set_buf(vi->tx_sg, &hdr->hdr, sizeof hdr->hdr);

    hdr->num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
    return virtqueue_add_buf(vi->svq, vi->tx_sg, hdr->num_sg,
                 0, skb, GFP_ATOMIC);
}

static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
{
    struct virtnet_info *vi = netdev_priv(dev);
    int capacity;

    /* Free up any pending old buffers before queueing new ones. */
    free_old_xmit_skbs(vi);

    /* Try to transmit */
    capacity = xmit_skb(vi, skb);

    /* This can happen with OOM and indirect buffers. */
    if (unlikely(capacity < 0)) {
        if (likely(capacity == -ENOMEM)) {
            if (net_ratelimit())
                dev_warn(&dev->dev,
                     "TX queue failure: out of memory\n");
        } else {
            dev->stats.tx_fifo_errors++;
            if (net_ratelimit())
                dev_warn(&dev->dev,
                     "Unexpected TX queue failure: %d\n",
                     capacity);
        }
        dev->stats.tx_dropped++;
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }
    virtqueue_kick(vi->svq);

    /* Don't wait up for transmitted skbs to be freed. */
    skb_orphan(skb);
    nf_reset(skb);

    /* Apparently nice girls don't return TX_BUSY; stop the queue
     * before it gets out of hand.  Naturally, this wastes entries. */
    if (capacity < 2+MAX_SKB_FRAGS) {
        netif_stop_queue(dev);
        if (unlikely(!virtqueue_enable_cb_delayed(vi->svq))) {
            /* More just got used, free them then recheck. */
            capacity += free_old_xmit_skbs(vi);
            if (capacity >= 2+MAX_SKB_FRAGS) {
                netif_start_queue(dev);
                virtqueue_disable_cb(vi->svq);
            }
        }
    }

    return NETDEV_TX_OK;
}

static int virtnet_set_mac_address(struct net_device *dev, void *p)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct virtio_device *vdev = vi->vdev;
    int ret;

    ret = eth_mac_addr(dev, p);
    if (ret)
        return ret;

    if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
        vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
                          dev->dev_addr, dev->addr_len);

    return 0;
}

static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
                           struct rtnl_link_stats64 *tot)
{
    struct virtnet_info *vi = netdev_priv(dev);
    int cpu;
    unsigned int start;

    for_each_possible_cpu(cpu) {
        struct virtnet_stats *stats = per_cpu_ptr(vi->stats, cpu);
        u64 tpackets, tbytes, rpackets, rbytes;

        do {
            start = u64_stats_fetch_begin_bh(&stats->tx_syncp);
            tpackets = stats->tx_packets;
            tbytes   = stats->tx_bytes;
        } while (u64_stats_fetch_retry_bh(&stats->tx_syncp, start));

        do {
            start = u64_stats_fetch_begin_bh(&stats->rx_syncp);
            rpackets = stats->rx_packets;
            rbytes   = stats->rx_bytes;
        } while (u64_stats_fetch_retry_bh(&stats->rx_syncp, start));

        tot->rx_packets += rpackets;
        tot->tx_packets += tpackets;
        tot->rx_bytes   += rbytes;
        tot->tx_bytes   += tbytes;
    }

    tot->tx_dropped = dev->stats.tx_dropped;
    tot->tx_fifo_errors = dev->stats.tx_fifo_errors;
    tot->rx_dropped = dev->stats.rx_dropped;
    tot->rx_length_errors = dev->stats.rx_length_errors;
    tot->rx_frame_errors = dev->stats.rx_frame_errors;

    return tot;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void virtnet_netpoll(struct net_device *dev)
{
    struct virtnet_info *vi = netdev_priv(dev);

    napi_schedule(&vi->napi);
}
#endif

static int virtnet_open(struct net_device *dev)
{
    struct virtnet_info *vi = netdev_priv(dev);

    /* Make sure we have some buffers: if oom use wq. */
    if (!try_fill_recv(vi, GFP_KERNEL))
        schedule_delayed_work(&vi->refill, 0);

    virtnet_napi_enable(vi);
    return 0;
}

/*
 * Send command via the control virtqueue and check status.  Commands
 * supported by the hypervisor, as indicated by feature bits, should
 * never fail unless improperly formated.
 */
static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
                 struct scatterlist *data, int out, int in)
{
    struct scatterlist *s, sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
    struct virtio_net_ctrl_hdr ctrl;
    virtio_net_ctrl_ack status = ~0;
    unsigned int tmp;
    int i;

    /* Caller should know better */
    BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ||
        (out + in > VIRTNET_SEND_COMMAND_SG_MAX));

    out++; /* Add header */
    in++; /* Add return status */

    ctrl.class = class;
    ctrl.cmd = cmd;

    sg_init_table(sg, out + in);

    sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
    for_each_sg(data, s, out + in - 2, i)
        sg_set_buf(&sg[i + 1], sg_virt(s), s->length);
    sg_set_buf(&sg[out + in - 1], &status, sizeof(status));

    BUG_ON(virtqueue_add_buf(vi->cvq, sg, out, in, vi, GFP_ATOMIC) < 0);

    virtqueue_kick(vi->cvq);

    /*
     * Spin for a response, the kick causes an ioport write, trapping
     * into the hypervisor, so the request should be handled immediately.
     */
    while (!virtqueue_get_buf(vi->cvq, &tmp))
        cpu_relax();

    return status == VIRTIO_NET_OK;
}

static void virtnet_ack_link_announce(struct virtnet_info *vi)
{
    rtnl_lock();
    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_ANNOUNCE,
                  VIRTIO_NET_CTRL_ANNOUNCE_ACK, NULL,
                  0, 0))
        dev_warn(&vi->dev->dev, "Failed to ack link announce.\n");
    rtnl_unlock();
}

static int virtnet_close(struct net_device *dev)
{
    struct virtnet_info *vi = netdev_priv(dev);

    /* Make sure refill_work doesn't re-enable napi! */
    cancel_delayed_work_sync(&vi->refill);
    napi_disable(&vi->napi);

    return 0;
}

static void virtnet_set_rx_mode(struct net_device *dev)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct scatterlist sg[2];
    u8 promisc, allmulti;
    struct virtio_net_ctrl_mac *mac_data;
    struct netdev_hw_addr *ha;
    int uc_count;
    int mc_count;
    void *buf;
    int i;

    /* We can't dynamicaly set ndo_set_rx_mode, so return gracefully */
    if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
        return;

    promisc = ((dev->flags & IFF_PROMISC) != 0);
    allmulti = ((dev->flags & IFF_ALLMULTI) != 0);

    sg_init_one(sg, &promisc, sizeof(promisc));

    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
                  VIRTIO_NET_CTRL_RX_PROMISC,
                  sg, 1, 0))
        dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
             promisc ? "en" : "dis");

    sg_init_one(sg, &allmulti, sizeof(allmulti));

    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
                  VIRTIO_NET_CTRL_RX_ALLMULTI,
                  sg, 1, 0))
        dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
             allmulti ? "en" : "dis");

    uc_count = netdev_uc_count(dev);
    mc_count = netdev_mc_count(dev);
    /* MAC filter - use one buffer for both lists */
    buf = kzalloc(((uc_count + mc_count) * ETH_ALEN) +
              (2 * sizeof(mac_data->entries)), GFP_ATOMIC);
    mac_data = buf;
    if (!buf) {
        dev_warn(&dev->dev, "No memory for MAC address buffer\n");
        return;
    }

    sg_init_table(sg, 2);

    /* Store the unicast list and count in the front of the buffer */
    mac_data->entries = uc_count;
    i = 0;
    netdev_for_each_uc_addr(ha, dev)
        memcpy(&mac_data->macs[i++][0], ha->addr, ETH_ALEN);

    sg_set_buf(&sg[0], mac_data,
           sizeof(mac_data->entries) + (uc_count * ETH_ALEN));

    /* multicast list and count fill the end */
    mac_data = (void *)&mac_data->macs[uc_count][0];

    mac_data->entries = mc_count;
    i = 0;
    netdev_for_each_mc_addr(ha, dev)
        memcpy(&mac_data->macs[i++][0], ha->addr, ETH_ALEN);

    sg_set_buf(&sg[1], mac_data,
           sizeof(mac_data->entries) + (mc_count * ETH_ALEN));

    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
                  VIRTIO_NET_CTRL_MAC_TABLE_SET,
                  sg, 2, 0))
        dev_warn(&dev->dev, "Failed to set MAC fitler table.\n");

    kfree(buf);
}

static int virtnet_vlan_rx_add_vid(struct net_device *dev, u16 vid)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct scatterlist sg;

    sg_init_one(&sg, &vid, sizeof(vid));

    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
                  VIRTIO_NET_CTRL_VLAN_ADD, &sg, 1, 0))
        dev_warn(&dev->dev, "Failed to add VLAN ID %d.\n", vid);
    return 0;
}

static int virtnet_vlan_rx_kill_vid(struct net_device *dev, u16 vid)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct scatterlist sg;

    sg_init_one(&sg, &vid, sizeof(vid));

    if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
                  VIRTIO_NET_CTRL_VLAN_DEL, &sg, 1, 0))
        dev_warn(&dev->dev, "Failed to kill VLAN ID %d.\n", vid);
    return 0;
}

static void virtnet_get_ringparam(struct net_device *dev,
                struct ethtool_ringparam *ring)
{
    struct virtnet_info *vi = netdev_priv(dev);

    ring->rx_max_pending = virtqueue_get_vring_size(vi->rvq);
    ring->tx_max_pending = virtqueue_get_vring_size(vi->svq);
    ring->rx_pending = ring->rx_max_pending;
    ring->tx_pending = ring->tx_max_pending;

}


static void virtnet_get_drvinfo(struct net_device *dev,
                struct ethtool_drvinfo *info)
{
    struct virtnet_info *vi = netdev_priv(dev);
    struct virtio_device *vdev = vi->vdev;

    strlcpy(info->driver, KBUILD_MODNAME, sizeof(info->driver));
    strlcpy(info->version, VIRTNET_DRIVER_VERSION, sizeof(info->version));
    strlcpy(info->bus_info, virtio_bus_name(vdev), sizeof(info->bus_info));

}

static const struct ethtool_ops virtnet_ethtool_ops = {
    .get_drvinfo = virtnet_get_drvinfo,
    .get_link = ethtool_op_get_link,
    .get_ringparam = virtnet_get_ringparam,
};

#define MIN_MTU 68
#define MAX_MTU 65535

static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
{
    if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
        return -EINVAL;
    dev->mtu = new_mtu;
    return 0;
}

static const struct net_device_ops virtnet_netdev = {
    .ndo_open            = virtnet_open,
    .ndo_stop            = virtnet_close,
    .ndo_start_xmit      = start_xmit,
    .ndo_validate_addr   = eth_validate_addr,
    .ndo_set_mac_address = virtnet_set_mac_address,
    .ndo_set_rx_mode     = virtnet_set_rx_mode,
    .ndo_change_mtu      = virtnet_change_mtu,
    .ndo_get_stats64     = virtnet_stats,
    .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
    .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
#ifdef CONFIG_NET_POLL_CONTROLLER
    .ndo_poll_controller = virtnet_netpoll,
#endif
};

static void virtnet_config_changed_work(struct work_struct *work)
{
    struct virtnet_info *vi =
        container_of(work, struct virtnet_info, config_work);
    u16 v;

    mutex_lock(&vi->config_lock);
    if (!vi->config_enable)
        goto done;

    if (virtio_config_val(vi->vdev, VIRTIO_NET_F_STATUS,
                  offsetof(struct virtio_net_config, status),
                  &v) < 0)
        goto done;

    if (v & VIRTIO_NET_S_ANNOUNCE) {
        netdev_notify_peers(vi->dev);
        virtnet_ack_link_announce(vi);
    }

    /* Ignore unknown (future) status bits */
    v &= VIRTIO_NET_S_LINK_UP;

    if (vi->status == v)
        goto done;

    vi->status = v;

    if (vi->status & VIRTIO_NET_S_LINK_UP) {
        netif_carrier_on(vi->dev);
        netif_wake_queue(vi->dev);
    } else {
        netif_carrier_off(vi->dev);
        netif_stop_queue(vi->dev);
    }
done:
    mutex_unlock(&vi->config_lock);
}

static void virtnet_config_changed(struct virtio_device *vdev)
{
    struct virtnet_info *vi = vdev->priv;

    schedule_work(&vi->config_work);
}

static int init_vqs(struct virtnet_info *vi)
{
    struct virtqueue *vqs[3];
    vq_callback_t *callbacks[] = { skb_recv_done, skb_xmit_done, NULL};
    const char *names[] = { "input", "output", "control" };
    int nvqs, err;

    /* We expect two virtqueues, receive then send,
     * and optionally control. */
    nvqs = virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ? 3 : 2;

    err = vi->vdev->config->find_vqs(vi->vdev, nvqs, vqs, callbacks, names);
    if (err)
        return err;

    vi->rvq = vqs[0];
    vi->svq = vqs[1];

    if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
        vi->cvq = vqs[2];

        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
            vi->dev->features |= NETIF_F_HW_VLAN_FILTER;
    }
    return 0;
}

static int virtnet_probe(struct virtio_device *vdev)
{
    int err;
    struct net_device *dev;
    struct virtnet_info *vi;

    /* Allocate ourselves a network device with room for our info */
    dev = alloc_etherdev(sizeof(struct virtnet_info));
    if (!dev)
        return -ENOMEM;

    /* Set up network device as normal. */
    dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE;
    dev->netdev_ops = &virtnet_netdev;
    dev->features = NETIF_F_HIGHDMA;

    SET_ETHTOOL_OPS(dev, &virtnet_ethtool_ops);
    SET_NETDEV_DEV(dev, &vdev->dev);

    /* Do we support "hardware" checksums? */
    if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
        /* This opens up the world of extra features. */
        dev->hw_features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
        if (csum)
            dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
            dev->hw_features |= NETIF_F_TSO | NETIF_F_UFO
                | NETIF_F_TSO_ECN | NETIF_F_TSO6;
        }
        /* Individual feature bits: what can host handle? */
        if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO4))
            dev->hw_features |= NETIF_F_TSO;
        if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO6))
            dev->hw_features |= NETIF_F_TSO6;
        if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_ECN))
            dev->hw_features |= NETIF_F_TSO_ECN;
        if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_UFO))
            dev->hw_features |= NETIF_F_UFO;

        if (gso)
            dev->features |= dev->hw_features & (NETIF_F_ALL_TSO|NETIF_F_UFO);
        /* (!csum && gso) case will be fixed by register_netdev() */
    }

    /* Configuration may specify what MAC to use.  Otherwise random. */
    if (virtio_config_val_len(vdev, VIRTIO_NET_F_MAC,
                  offsetof(struct virtio_net_config, mac),
                  dev->dev_addr, dev->addr_len) < 0)
        eth_hw_addr_random(dev);

    /* Set up our device-specific information */
    vi = netdev_priv(dev);
    netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
    vi->dev = dev;
    vi->vdev = vdev;
    vdev->priv = vi;
    vi->pages = NULL;
    vi->stats = alloc_percpu(struct virtnet_stats);
    err = -ENOMEM;
    if (vi->stats == NULL)
        goto free;

    INIT_DELAYED_WORK(&vi->refill, refill_work);
    mutex_init(&vi->config_lock);
    vi->config_enable = true;
    INIT_WORK(&vi->config_work, virtnet_config_changed_work);
    sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
    sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));

    /* If we can receive ANY GSO packets, we must allocate large ones. */
    if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
        virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6) ||
        virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_ECN))
        vi->big_packets = true;

    if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
        vi->mergeable_rx_bufs = true;

    err = init_vqs(vi);
    if (err)
        goto free_stats;

    err = register_netdev(dev);
    if (err) {
        pr_debug("virtio_net: registering device failed\n");
        goto free_vqs;
    }

    /* Last of all, set up some receive buffers. */
    try_fill_recv(vi, GFP_KERNEL);

    /* If we didn't even get one input buffer, we're useless. */
    if (vi->num == 0) {
        err = -ENOMEM;
        goto unregister;
    }

    /* Assume link up if device can't report link status,
       otherwise get link status from config. */
    if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
        netif_carrier_off(dev);
        schedule_work(&vi->config_work);
    } else {
        vi->status = VIRTIO_NET_S_LINK_UP;
        netif_carrier_on(dev);
    }

    pr_debug("virtnet: registered device %s\n", dev->name);
    return 0;

unregister:
    unregister_netdev(dev);
free_vqs:
    vdev->config->del_vqs(vdev);
free_stats:
    free_percpu(vi->stats);
free:
    free_netdev(dev);
    return err;
}

static void free_unused_bufs(struct virtnet_info *vi)
{
    void *buf;
    while (1) {
        buf = virtqueue_detach_unused_buf(vi->svq);
        if (!buf)
            break;
        dev_kfree_skb(buf);
    }
    while (1) {
        buf = virtqueue_detach_unused_buf(vi->rvq);
        if (!buf)
            break;
        if (vi->mergeable_rx_bufs || vi->big_packets)
            give_pages(vi, buf);
        else
            dev_kfree_skb(buf);
        --vi->num;
    }
    BUG_ON(vi->num != 0);
}

static void remove_vq_common(struct virtnet_info *vi)
{
    vi->vdev->config->reset(vi->vdev);

    /* Free unused buffers in both send and recv, if any. */
    free_unused_bufs(vi);

    vi->vdev->config->del_vqs(vi->vdev);

    while (vi->pages)
        __free_pages(get_a_page(vi, GFP_KERNEL), 0);
}

static void __devexit virtnet_remove(struct virtio_device *vdev)
{
    struct virtnet_info *vi = vdev->priv;

    /* Prevent config work handler from accessing the device. */
    mutex_lock(&vi->config_lock);
    vi->config_enable = false;
    mutex_unlock(&vi->config_lock);

    unregister_netdev(vi->dev);

    remove_vq_common(vi);

    flush_work(&vi->config_work);

    free_percpu(vi->stats);
    free_netdev(vi->dev);
}

#ifdef CONFIG_PM
static int virtnet_freeze(struct virtio_device *vdev)
{
    struct virtnet_info *vi = vdev->priv;

    /* Prevent config work handler from accessing the device */
    mutex_lock(&vi->config_lock);
    vi->config_enable = false;
    mutex_unlock(&vi->config_lock);

    netif_device_detach(vi->dev);
    cancel_delayed_work_sync(&vi->refill);

    if (netif_running(vi->dev))
        napi_disable(&vi->napi);

    remove_vq_common(vi);

    flush_work(&vi->config_work);

    return 0;
}

static int virtnet_restore(struct virtio_device *vdev)
{
    struct virtnet_info *vi = vdev->priv;
    int err;

    err = init_vqs(vi);
    if (err)
        return err;

    if (netif_running(vi->dev))
        virtnet_napi_enable(vi);

    netif_device_attach(vi->dev);

    if (!try_fill_recv(vi, GFP_KERNEL))
        schedule_delayed_work(&vi->refill, 0);

    mutex_lock(&vi->config_lock);
    vi->config_enable = true;
    mutex_unlock(&vi->config_lock);

    return 0;
}
#endif

static struct virtio_device_id id_table[] = {
    { VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
    { 0 },
};

static unsigned int features[] = {
    VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM,
    VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC,
    VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
    VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
    VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
    VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
    VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
    VIRTIO_NET_F_GUEST_ANNOUNCE,
};

static struct virtio_driver virtio_net_driver = {
    .feature_table = features,
    .feature_table_size = ARRAY_SIZE(features),
    .driver.name =  KBUILD_MODNAME,
    .driver.owner = THIS_MODULE,
    .id_table = id_table,
    .probe =    virtnet_probe,
    .remove =   __devexit_p(virtnet_remove),
    .config_changed = virtnet_config_changed,
#ifdef CONFIG_PM
    .freeze =   virtnet_freeze,
    .restore =  virtnet_restore,
#endif
};

static int __init init(void)
{
    return register_virtio_driver(&virtio_net_driver);
}

static void __exit fini(void)
{
    unregister_virtio_driver(&virtio_net_driver);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio network driver");
MODULE_LICENSE("GPL");