virtio-net: forbid XDP when VIRTIO_NET_F_GUEST_UFO is support

[mirror_ubuntu-bionic-kernel.git] / drivers / net / virtio_net.c

/* A network driver using virtio.
 *
 * Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> 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, see <http://www.gnu.org/licenses/>.
 */
//#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/bpf.h>
#include <linux/scatterlist.h>
#include <linux/if_vlan.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/average.h>
#include <net/busy_poll.h>

static int napi_weight = NAPI_POLL_WEIGHT;
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 GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
#define GOOD_COPY_LEN   128

/* RX packet size EWMA. The average packet size is used to determine the packet
 * buffer size when refilling RX rings. As the entire RX ring may be refilled
 * at once, the weight is chosen so that the EWMA will be insensitive to short-
 * term, transient changes in packet size.
 */
DECLARE_EWMA(pkt_len, 1, 64)

/* Minimum alignment for mergeable packet buffers. */
#define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, 256)

#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;
};

/* Internal representation of a send virtqueue */
struct send_queue {
        /* Virtqueue associated with this send _queue */
        struct virtqueue *vq;

        /* TX: fragments + linear part + virtio header */
        struct scatterlist sg[MAX_SKB_FRAGS + 2];

        /* Name of the send queue: output.$index */
        char name[40];
};

/* Internal representation of a receive virtqueue */
struct receive_queue {
        /* Virtqueue associated with this receive_queue */
        struct virtqueue *vq;

        struct napi_struct napi;

        struct bpf_prog __rcu *xdp_prog;

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

        /* Average packet length for mergeable receive buffers. */
        struct ewma_pkt_len mrg_avg_pkt_len;

        /* Page frag for packet buffer allocation. */
        struct page_frag alloc_frag;

        /* RX: fragments + linear part + virtio header */
        struct scatterlist sg[MAX_SKB_FRAGS + 2];

        /* Name of this receive queue: input.$index */
        char name[40];
};

struct virtnet_info {
        struct virtio_device *vdev;
        struct virtqueue *cvq;
        struct net_device *dev;
        struct send_queue *sq;
        struct receive_queue *rq;
        unsigned int status;

        /* Max # of queue pairs supported by the device */
        u16 max_queue_pairs;

        /* # of queue pairs currently used by the driver */
        u16 curr_queue_pairs;

        /* # of XDP queue pairs currently used by the driver */
        u16 xdp_queue_pairs;

        /* 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;

        /* Has control virtqueue */
        bool has_cvq;

        /* Host can handle any s/g split between our header and packet data */
        bool any_header_sg;

        /* Packet virtio header size */
        u8 hdr_len;

        /* 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;

        /* Does the affinity hint is set for virtqueues? */
        bool affinity_hint_set;

        /* CPU hotplug instances for online & dead */
        struct hlist_node node;
        struct hlist_node node_dead;

        /* Control VQ buffers: protected by the rtnl lock */
        struct virtio_net_ctrl_hdr ctrl_hdr;
        virtio_net_ctrl_ack ctrl_status;
        struct virtio_net_ctrl_mq ctrl_mq;
        u8 ctrl_promisc;
        u8 ctrl_allmulti;
        u16 ctrl_vid;

        /* Ethtool settings */
        u8 duplex;
        u32 speed;
};

struct padded_vnet_hdr {
        struct virtio_net_hdr_mrg_rxbuf hdr;
        /*
         * hdr is in a separate sg buffer, and data sg buffer shares same page
         * with this header sg. This padding makes next sg 16 byte aligned
         * after the header.
         */
        char padding[4];
};

/* Converting between virtqueue no. and kernel tx/rx queue no.
 * 0:rx0 1:tx0 2:rx1 3:tx1 ... 2N:rxN 2N+1:txN 2N+2:cvq
 */
static int vq2txq(struct virtqueue *vq)
{
        return (vq->index - 1) / 2;
}

static int txq2vq(int txq)
{
        return txq * 2 + 1;
}

static int vq2rxq(struct virtqueue *vq)
{
        return vq->index / 2;
}

static int rxq2vq(int rxq)
{
        return rxq * 2;
}

static inline struct virtio_net_hdr_mrg_rxbuf *skb_vnet_hdr(struct sk_buff *skb)
{
        return (struct virtio_net_hdr_mrg_rxbuf *)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 receive_queue *rq, struct page *page)
{
        struct page *end;

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

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

        if (p) {
                rq->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 *vq)
{
        struct virtnet_info *vi = vq->vdev->priv;

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

        /* We were probably waiting for more output buffers. */
        netif_wake_subqueue(vi->dev, vq2txq(vq));
}

static unsigned int mergeable_ctx_to_buf_truesize(unsigned long mrg_ctx)
{
        unsigned int truesize = mrg_ctx & (MERGEABLE_BUFFER_ALIGN - 1);
        return (truesize + 1) * MERGEABLE_BUFFER_ALIGN;
}

static void *mergeable_ctx_to_buf_address(unsigned long mrg_ctx)
{
        return (void *)(mrg_ctx & -MERGEABLE_BUFFER_ALIGN);

}

static unsigned long mergeable_buf_to_ctx(void *buf, unsigned int truesize)
{
        unsigned int size = truesize / MERGEABLE_BUFFER_ALIGN;
        return (unsigned long)buf | (size - 1);
}

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

        p = page_address(page) + offset;

        /* copy small packet so we can reuse these pages for small data */
        skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN);
        if (unlikely(!skb))
                return NULL;

        hdr = skb_vnet_hdr(skb);

        hdr_len = vi->hdr_len;
        if (vi->mergeable_rx_bufs)
                hdr_padded_len = sizeof *hdr;
        else
                hdr_padded_len = sizeof(struct padded_vnet_hdr);

        memcpy(hdr, p, hdr_len);

        len -= hdr_len;
        offset += hdr_padded_len;
        p += hdr_padded_len;

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

        len -= copy;
        offset += copy;

        if (vi->mergeable_rx_bufs) {
                if (len)
                        skb_add_rx_frag(skb, 0, page, offset, len, truesize);
                else
                        put_page(page);
                return skb;
        }

        /*
         * 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)) {
                net_dbg_ratelimited("%s: too much data\n", skb->dev->name);
                dev_kfree_skb(skb);
                return NULL;
        }
        BUG_ON(offset >= PAGE_SIZE);
        while (len) {
                unsigned int frag_size = min((unsigned)PAGE_SIZE - offset, len);
                skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset,
                                frag_size, truesize);
                len -= frag_size;
                page = (struct page *)page->private;
                offset = 0;
        }

        if (page)
                give_pages(rq, page);

        return skb;
}

static void virtnet_xdp_xmit(struct virtnet_info *vi,
                             struct receive_queue *rq,
                             struct send_queue *sq,
                             struct xdp_buff *xdp)
{
        struct page *page = virt_to_head_page(xdp->data);
        struct virtio_net_hdr_mrg_rxbuf *hdr;
        unsigned int num_sg, len;
        void *xdp_sent;
        int err;

        /* Free up any pending old buffers before queueing new ones. */
        while ((xdp_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) {
                struct page *sent_page = virt_to_head_page(xdp_sent);

                if (vi->mergeable_rx_bufs)
                        put_page(sent_page);
                else
                        give_pages(rq, sent_page);
        }

        /* Zero header and leave csum up to XDP layers */
        hdr = xdp->data;
        memset(hdr, 0, vi->hdr_len);

        num_sg = 1;
        sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data);
        err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg,
                                   xdp->data, GFP_ATOMIC);
        if (unlikely(err)) {
                if (vi->mergeable_rx_bufs)
                        put_page(page);
                else
                        give_pages(rq, page);
                return; // On error abort to avoid unnecessary kick
        } else if (!vi->mergeable_rx_bufs) {
                /* If not mergeable bufs must be big packets so cleanup pages */
                give_pages(rq, (struct page *)page->private);
                page->private = 0;
        }

        virtqueue_kick(sq->vq);
}

static u32 do_xdp_prog(struct virtnet_info *vi,
                       struct receive_queue *rq,
                       struct bpf_prog *xdp_prog,
                       struct page *page, int offset, int len)
{
        int hdr_padded_len;
        struct xdp_buff xdp;
        unsigned int qp;
        u32 act;
        u8 *buf;

        buf = page_address(page) + offset;

        if (vi->mergeable_rx_bufs)
                hdr_padded_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
        else
                hdr_padded_len = sizeof(struct padded_vnet_hdr);

        xdp.data = buf + hdr_padded_len;
        xdp.data_end = xdp.data + (len - vi->hdr_len);

        act = bpf_prog_run_xdp(xdp_prog, &xdp);
        switch (act) {
        case XDP_PASS:
                return XDP_PASS;
        case XDP_TX:
                qp = vi->curr_queue_pairs -
                        vi->xdp_queue_pairs +
                        smp_processor_id();
                xdp.data = buf + (vi->mergeable_rx_bufs ? 0 : 4);
                virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp);
                return XDP_TX;
        default:
                bpf_warn_invalid_xdp_action(act);
        case XDP_ABORTED:
        case XDP_DROP:
                return XDP_DROP;
        }
}

static struct sk_buff *receive_small(struct virtnet_info *vi, void *buf, unsigned int len)
{
        struct sk_buff * skb = buf;

        len -= vi->hdr_len;
        skb_trim(skb, len);

        return skb;
}

static struct sk_buff *receive_big(struct net_device *dev,
                                   struct virtnet_info *vi,
                                   struct receive_queue *rq,
                                   void *buf,
                                   unsigned int len)
{
        struct bpf_prog *xdp_prog;
        struct page *page = buf;
        struct sk_buff *skb;

        rcu_read_lock();
        xdp_prog = rcu_dereference(rq->xdp_prog);
        if (xdp_prog) {
                struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
                u32 act;

                if (unlikely(hdr->hdr.gso_type))
                        goto err_xdp;
                act = do_xdp_prog(vi, rq, xdp_prog, page, 0, len);
                switch (act) {
                case XDP_PASS:
                        break;
                case XDP_TX:
                        rcu_read_unlock();
                        goto xdp_xmit;
                case XDP_DROP:
                default:
                        goto err_xdp;
                }
        }
        rcu_read_unlock();

        skb = page_to_skb(vi, rq, page, 0, len, PAGE_SIZE);
        if (unlikely(!skb))
                goto err;

        return skb;

err_xdp:
        rcu_read_unlock();
err:
        dev->stats.rx_dropped++;
        give_pages(rq, page);
xdp_xmit:
        return NULL;
}

/* The conditions to enable XDP should preclude the underlying device from
 * sending packets across multiple buffers (num_buf > 1). However per spec
 * it does not appear to be illegal to do so but rather just against convention.
 * So in order to avoid making a system unresponsive the packets are pushed
 * into a page and the XDP program is run. This will be extremely slow and we
 * push a warning to the user to fix this as soon as possible. Fixing this may
 * require resolving the underlying hardware to determine why multiple buffers
 * are being received or simply loading the XDP program in the ingress stack
 * after the skb is built because there is no advantage to running it here
 * anymore.
 */
static struct page *xdp_linearize_page(struct receive_queue *rq,
                                       u16 *num_buf,
                                       struct page *p,
                                       int offset,
                                       unsigned int *len)
{
        struct page *page = alloc_page(GFP_ATOMIC);
        unsigned int page_off = 0;

        if (!page)
                return NULL;

        memcpy(page_address(page) + page_off, page_address(p) + offset, *len);
        page_off += *len;

        while (--*num_buf) {
                unsigned int buflen;
                unsigned long ctx;
                void *buf;
                int off;

                ctx = (unsigned long)virtqueue_get_buf(rq->vq, &buflen);
                if (unlikely(!ctx))
                        goto err_buf;

                buf = mergeable_ctx_to_buf_address(ctx);
                p = virt_to_head_page(buf);
                off = buf - page_address(p);

                /* guard against a misconfigured or uncooperative backend that
                 * is sending packet larger than the MTU.
                 */
                if ((page_off + buflen) > PAGE_SIZE) {
                        put_page(p);
                        goto err_buf;
                }

                memcpy(page_address(page) + page_off,
                       page_address(p) + off, buflen);
                page_off += buflen;
                put_page(p);
        }

        *len = page_off;
        return page;
err_buf:
        __free_pages(page, 0);
        return NULL;
}

static struct sk_buff *receive_mergeable(struct net_device *dev,
                                         struct virtnet_info *vi,
                                         struct receive_queue *rq,
                                         unsigned long ctx,
                                         unsigned int len)
{
        void *buf = mergeable_ctx_to_buf_address(ctx);
        struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
        u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
        struct page *page = virt_to_head_page(buf);
        int offset = buf - page_address(page);
        struct sk_buff *head_skb, *curr_skb;
        struct bpf_prog *xdp_prog;
        unsigned int truesize;

        head_skb = NULL;

        rcu_read_lock();
        xdp_prog = rcu_dereference(rq->xdp_prog);
        if (xdp_prog) {
                struct page *xdp_page;
                u32 act;

                /* This happens when rx buffer size is underestimated */
                if (unlikely(num_buf > 1)) {
                        /* linearize data for XDP */
                        xdp_page = xdp_linearize_page(rq, &num_buf,
                                                      page, offset, &len);
                        if (!xdp_page)
                                goto err_xdp;
                        offset = 0;
                } else {
                        xdp_page = page;
                }

                /* Transient failure which in theory could occur if
                 * in-flight packets from before XDP was enabled reach
                 * the receive path after XDP is loaded. In practice I
                 * was not able to create this condition.
                 */
                if (unlikely(hdr->hdr.gso_type))
                        goto err_xdp;

                act = do_xdp_prog(vi, rq, xdp_prog, xdp_page, offset, len);
                switch (act) {
                case XDP_PASS:
                        /* We can only create skb based on xdp_page. */
                        if (unlikely(xdp_page != page)) {
                                rcu_read_unlock();
                                put_page(page);
                                head_skb = page_to_skb(vi, rq, xdp_page,
                                                       0, len, PAGE_SIZE);
                                ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
                                return head_skb;
                        }
                        break;
                case XDP_TX:
                        ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
                        if (unlikely(xdp_page != page))
                                goto err_xdp;
                        rcu_read_unlock();
                        goto xdp_xmit;
                case XDP_DROP:
                default:
                        if (unlikely(xdp_page != page))
                                __free_pages(xdp_page, 0);
                        ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
                        goto err_xdp;
                }
        }
        rcu_read_unlock();

        truesize = max(len, mergeable_ctx_to_buf_truesize(ctx));
        head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
        curr_skb = head_skb;

        if (unlikely(!curr_skb))
                goto err_skb;
        while (--num_buf) {
                int num_skb_frags;

                ctx = (unsigned long)virtqueue_get_buf(rq->vq, &len);
                if (unlikely(!ctx)) {
                        pr_debug("%s: rx error: %d buffers out of %d missing\n",
                                 dev->name, num_buf,
                                 virtio16_to_cpu(vi->vdev,
                                                 hdr->num_buffers));
                        dev->stats.rx_length_errors++;
                        goto err_buf;
                }

                buf = mergeable_ctx_to_buf_address(ctx);
                page = virt_to_head_page(buf);

                num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
                if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
                        struct sk_buff *nskb = alloc_skb(0, GFP_ATOMIC);

                        if (unlikely(!nskb))
                                goto err_skb;
                        if (curr_skb == head_skb)
                                skb_shinfo(curr_skb)->frag_list = nskb;
                        else
                                curr_skb->next = nskb;
                        curr_skb = nskb;
                        head_skb->truesize += nskb->truesize;
                        num_skb_frags = 0;
                }
                truesize = max(len, mergeable_ctx_to_buf_truesize(ctx));
                if (curr_skb != head_skb) {
                        head_skb->data_len += len;
                        head_skb->len += len;
                        head_skb->truesize += truesize;
                }
                offset = buf - page_address(page);
                if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
                        put_page(page);
                        skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
                                             len, truesize);
                } else {
                        skb_add_rx_frag(curr_skb, num_skb_frags, page,
                                        offset, len, truesize);
                }
        }

        ewma_pkt_len_add(&rq->mrg_avg_pkt_len, head_skb->len);
        return head_skb;

err_xdp:
        rcu_read_unlock();
err_skb:
        put_page(page);
        while (--num_buf) {
                ctx = (unsigned long)virtqueue_get_buf(rq->vq, &len);
                if (unlikely(!ctx)) {
                        pr_debug("%s: rx error: %d buffers missing\n",
                                 dev->name, num_buf);
                        dev->stats.rx_length_errors++;
                        break;
                }
                page = virt_to_head_page(mergeable_ctx_to_buf_address(ctx));
                put_page(page);
        }
err_buf:
        dev->stats.rx_dropped++;
        dev_kfree_skb(head_skb);
xdp_xmit:
        return NULL;
}

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

        if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
                pr_debug("%s: short packet %i\n", dev->name, len);
                dev->stats.rx_length_errors++;
                if (vi->mergeable_rx_bufs) {
                        unsigned long ctx = (unsigned long)buf;
                        void *base = mergeable_ctx_to_buf_address(ctx);
                        put_page(virt_to_head_page(base));
                } else if (vi->big_packets) {
                        give_pages(rq, buf);
                } else {
                        dev_kfree_skb(buf);
                }
                return;
        }

        if (vi->mergeable_rx_bufs)
                skb = receive_mergeable(dev, vi, rq, (unsigned long)buf, len);
        else if (vi->big_packets)
                skb = receive_big(dev, vi, rq, buf, len);
        else
                skb = receive_small(vi, buf, len);

        if (unlikely(!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_DATA_VALID)
                skb->ip_summed = CHECKSUM_UNNECESSARY;

        if (virtio_net_hdr_to_skb(skb, &hdr->hdr,
                                  virtio_is_little_endian(vi->vdev))) {
                net_warn_ratelimited("%s: bad gso: type: %u, size: %u\n",
                                     dev->name, hdr->hdr.gso_type,
                                     hdr->hdr.gso_size);
                goto frame_err;
        }

        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);

        napi_gro_receive(&rq->napi, skb);
        return;

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

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

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

        skb_put(skb, GOOD_PACKET_LEN);

        hdr = skb_vnet_hdr(skb);
        sg_init_table(rq->sg, 2);
        sg_set_buf(rq->sg, hdr, vi->hdr_len);
        skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);

        err = virtqueue_add_inbuf(rq->vq, rq->sg, 2, skb, gfp);
        if (err < 0)
                dev_kfree_skb(skb);

        return err;
}

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

        sg_init_table(rq->sg, MAX_SKB_FRAGS + 2);

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

        /* rq->sg[0], rq->sg[1] share the same page */
        /* a separated rq->sg[0] for header - required in case !any_header_sg */
        sg_set_buf(&rq->sg[0], p, vi->hdr_len);

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

        /* chain first in list head */
        first->private = (unsigned long)list;
        err = virtqueue_add_inbuf(rq->vq, rq->sg, MAX_SKB_FRAGS + 2,
                                  first, gfp);
        if (err < 0)
                give_pages(rq, first);

        return err;
}

static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
{
        const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
        unsigned int len;

        len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len),
                        GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
        return ALIGN(len, MERGEABLE_BUFFER_ALIGN);
}

static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
{
        struct page_frag *alloc_frag = &rq->alloc_frag;
        char *buf;
        unsigned long ctx;
        int err;
        unsigned int len, hole;

        len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len);
        if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
                return -ENOMEM;

        buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
        ctx = mergeable_buf_to_ctx(buf, len);
        get_page(alloc_frag->page);
        alloc_frag->offset += len;
        hole = alloc_frag->size - alloc_frag->offset;
        if (hole < len) {
                /* To avoid internal fragmentation, if there is very likely not
                 * enough space for another buffer, add the remaining space to
                 * the current buffer. This extra space is not included in
                 * the truesize stored in ctx.
                 */
                len += hole;
                alloc_frag->offset += hole;
        }

        sg_init_one(rq->sg, buf, len);
        err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, (void *)ctx, gfp);
        if (err < 0)
                put_page(virt_to_head_page(buf));

        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, struct receive_queue *rq,
                          gfp_t gfp)
{
        int err;
        bool oom;

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

                oom = err == -ENOMEM;
                if (err)
                        break;
        } while (rq->vq->num_free);
        virtqueue_kick(rq->vq);
        return !oom;
}

static void skb_recv_done(struct virtqueue *rvq)
{
        struct virtnet_info *vi = rvq->vdev->priv;
        struct receive_queue *rq = &vi->rq[vq2rxq(rvq)];

        /* Schedule NAPI, Suppress further interrupts if successful. */
        if (napi_schedule_prep(&rq->napi)) {
                virtqueue_disable_cb(rvq);
                __napi_schedule(&rq->napi);
        }
}

static void virtnet_napi_enable(struct receive_queue *rq)
{
        napi_enable(&rq->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(&rq->napi)) {
                virtqueue_disable_cb(rq->vq);
                local_bh_disable();
                __napi_schedule(&rq->napi);
                local_bh_enable();
        }
}

static void refill_work(struct work_struct *work)
{
        struct virtnet_info *vi =
                container_of(work, struct virtnet_info, refill.work);
        bool still_empty;
        int i;

        for (i = 0; i < vi->curr_queue_pairs; i++) {
                struct receive_queue *rq = &vi->rq[i];

                napi_disable(&rq->napi);
                still_empty = !try_fill_recv(vi, rq, GFP_KERNEL);
                virtnet_napi_enable(rq);

                /* 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_receive(struct receive_queue *rq, int budget)
{
        struct virtnet_info *vi = rq->vq->vdev->priv;
        unsigned int len, received = 0;
        void *buf;

        while (received < budget &&
               (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
                receive_buf(vi, rq, buf, len);
                received++;
        }

        if (rq->vq->num_free > virtqueue_get_vring_size(rq->vq) / 2) {
                if (!try_fill_recv(vi, rq, GFP_ATOMIC))
                        schedule_delayed_work(&vi->refill, 0);
        }

        return received;
}

static int virtnet_poll(struct napi_struct *napi, int budget)
{
        struct receive_queue *rq =
                container_of(napi, struct receive_queue, napi);
        unsigned int r, received;

        received = virtnet_receive(rq, budget);

        /* Out of packets? */
        if (received < budget) {
                r = virtqueue_enable_cb_prepare(rq->vq);
                napi_complete_done(napi, received);
                if (unlikely(virtqueue_poll(rq->vq, r)) &&
                    napi_schedule_prep(napi)) {
                        virtqueue_disable_cb(rq->vq);
                        __napi_schedule(napi);
                }
        }

        return received;
}

#ifdef CONFIG_NET_RX_BUSY_POLL
/* must be called with local_bh_disable()d */
static int virtnet_busy_poll(struct napi_struct *napi)
{
        struct receive_queue *rq =
                container_of(napi, struct receive_queue, napi);
        struct virtnet_info *vi = rq->vq->vdev->priv;
        int r, received = 0, budget = 4;

        if (!(vi->status & VIRTIO_NET_S_LINK_UP))
                return LL_FLUSH_FAILED;

        if (!napi_schedule_prep(napi))
                return LL_FLUSH_BUSY;

        virtqueue_disable_cb(rq->vq);

again:
        received += virtnet_receive(rq, budget);

        r = virtqueue_enable_cb_prepare(rq->vq);
        clear_bit(NAPI_STATE_SCHED, &napi->state);
        if (unlikely(virtqueue_poll(rq->vq, r)) &&
            napi_schedule_prep(napi)) {
                virtqueue_disable_cb(rq->vq);
                if (received < budget) {
                        budget -= received;
                        goto again;
                } else {
                        __napi_schedule(napi);
                }
        }

        return received;
}
#endif  /* CONFIG_NET_RX_BUSY_POLL */

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

        for (i = 0; i < vi->max_queue_pairs; i++) {
                if (i < vi->curr_queue_pairs)
                        /* Make sure we have some buffers: if oom use wq. */
                        if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
                                schedule_delayed_work(&vi->refill, 0);
                virtnet_napi_enable(&vi->rq[i]);
        }

        return 0;
}

static void free_old_xmit_skbs(struct send_queue *sq)
{
        struct sk_buff *skb;
        unsigned int len;
        struct virtnet_info *vi = sq->vq->vdev->priv;
        struct virtnet_stats *stats = this_cpu_ptr(vi->stats);

        while ((skb = virtqueue_get_buf(sq->vq, &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);

                dev_kfree_skb_any(skb);
        }
}

static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
{
        struct virtio_net_hdr_mrg_rxbuf *hdr;
        const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
        struct virtnet_info *vi = sq->vq->vdev->priv;
        unsigned num_sg;
        unsigned hdr_len = vi->hdr_len;
        bool can_push;

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

        can_push = vi->any_header_sg &&
                !((unsigned long)skb->data & (__alignof__(*hdr) - 1)) &&
                !skb_header_cloned(skb) && skb_headroom(skb) >= hdr_len;
        /* Even if we can, don't push here yet as this would skew
         * csum_start offset below. */
        if (can_push)
                hdr = (struct virtio_net_hdr_mrg_rxbuf *)(skb->data - hdr_len);
        else
                hdr = skb_vnet_hdr(skb);

        if (virtio_net_hdr_from_skb(skb, &hdr->hdr,
                                    virtio_is_little_endian(vi->vdev)))
                BUG();

        if (vi->mergeable_rx_bufs)
                hdr->num_buffers = 0;

        sg_init_table(sq->sg, skb_shinfo(skb)->nr_frags + (can_push ? 1 : 2));
        if (can_push) {
                __skb_push(skb, hdr_len);
                num_sg = skb_to_sgvec(skb, sq->sg, 0, skb->len);
                /* Pull header back to avoid skew in tx bytes calculations. */
                __skb_pull(skb, hdr_len);
        } else {
                sg_set_buf(sq->sg, hdr, hdr_len);
                num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1;
        }
        return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, 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 qnum = skb_get_queue_mapping(skb);
        struct send_queue *sq = &vi->sq[qnum];
        int err;
        struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
        bool kick = !skb->xmit_more;

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

        /* timestamp packet in software */
        skb_tx_timestamp(skb);

        /* Try to transmit */
        err = xmit_skb(sq, skb);

        /* This should not happen! */
        if (unlikely(err)) {
                dev->stats.tx_fifo_errors++;
                if (net_ratelimit())
                        dev_warn(&dev->dev,
                                 "Unexpected TXQ (%d) queue failure: %d\n", qnum, err);
                dev->stats.tx_dropped++;
                dev_kfree_skb_any(skb);
                return NETDEV_TX_OK;
        }

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

        /* If running out of space, stop queue to avoid getting packets that we
         * are then unable to transmit.
         * An alternative would be to force queuing layer to requeue the skb by
         * returning NETDEV_TX_BUSY. However, NETDEV_TX_BUSY should not be
         * returned in a normal path of operation: it means that driver is not
         * maintaining the TX queue stop/start state properly, and causes
         * the stack to do a non-trivial amount of useless work.
         * Since most packets only take 1 or 2 ring slots, stopping the queue
         * early means 16 slots are typically wasted.
         */
        if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
                netif_stop_subqueue(dev, qnum);
                if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
                        /* More just got used, free them then recheck. */
                        free_old_xmit_skbs(sq);
                        if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) {
                                netif_start_subqueue(dev, qnum);
                                virtqueue_disable_cb(sq->vq);
                        }
                }
        }

        if (kick || netif_xmit_stopped(txq))
                virtqueue_kick(sq->vq);

        return NETDEV_TX_OK;
}

/*
 * Send command via the control virtqueue and check status.  Commands
 * supported by the hypervisor, as indicated by feature bits, should
 * never fail unless improperly formatted.
 */
static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
                                 struct scatterlist *out)
{
        struct scatterlist *sgs[4], hdr, stat;
        unsigned out_num = 0, tmp;

        /* Caller should know better */
        BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));

        vi->ctrl_status = ~0;
        vi->ctrl_hdr.class = class;
        vi->ctrl_hdr.cmd = cmd;
        /* Add header */
        sg_init_one(&hdr, &vi->ctrl_hdr, sizeof(vi->ctrl_hdr));
        sgs[out_num++] = &hdr;

        if (out)
                sgs[out_num++] = out;

        /* Add return status. */
        sg_init_one(&stat, &vi->ctrl_status, sizeof(vi->ctrl_status));
        sgs[out_num] = &stat;

        BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
        virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);

        if (unlikely(!virtqueue_kick(vi->cvq)))
                return vi->ctrl_status == VIRTIO_NET_OK;

        /* 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) &&
               !virtqueue_is_broken(vi->cvq))
                cpu_relax();

        return vi->ctrl_status == VIRTIO_NET_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;
        struct sockaddr *addr;
        struct scatterlist sg;

        addr = kmalloc(sizeof(*addr), GFP_KERNEL);
        if (!addr)
                return -ENOMEM;
        memcpy(addr, p, sizeof(*addr));

        ret = eth_prepare_mac_addr_change(dev, addr);
        if (ret)
                goto out;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
                sg_init_one(&sg, addr->sa_data, dev->addr_len);
                if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
                                          VIRTIO_NET_CTRL_MAC_ADDR_SET, &sg)) {
                        dev_warn(&vdev->dev,
                                 "Failed to set mac address by vq command.\n");
                        ret = -EINVAL;
                        goto out;
                }
        } else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
                   !virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
                unsigned int i;

                /* Naturally, this has an atomicity problem. */
                for (i = 0; i < dev->addr_len; i++)
                        virtio_cwrite8(vdev,
                                       offsetof(struct virtio_net_config, mac) +
                                       i, addr->sa_data[i]);
        }

        eth_commit_mac_addr_change(dev, p);
        ret = 0;

out:
        kfree(addr);
        return ret;
}

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_irq(&stats->tx_syncp);
                        tpackets = stats->tx_packets;
                        tbytes   = stats->tx_bytes;
                } while (u64_stats_fetch_retry_irq(&stats->tx_syncp, start));

                do {
                        start = u64_stats_fetch_begin_irq(&stats->rx_syncp);
                        rpackets = stats->rx_packets;
                        rbytes   = stats->rx_bytes;
                } while (u64_stats_fetch_retry_irq(&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);
        int i;

        for (i = 0; i < vi->curr_queue_pairs; i++)
                napi_schedule(&vi->rq[i].napi);
}
#endif

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))
                dev_warn(&vi->dev->dev, "Failed to ack link announce.\n");
        rtnl_unlock();
}

static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
{
        struct scatterlist sg;
        struct net_device *dev = vi->dev;

        if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
                return 0;

        vi->ctrl_mq.virtqueue_pairs = cpu_to_virtio16(vi->vdev, queue_pairs);
        sg_init_one(&sg, &vi->ctrl_mq, sizeof(vi->ctrl_mq));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MQ,
                                  VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &sg)) {
                dev_warn(&dev->dev, "Fail to set num of queue pairs to %d\n",
                         queue_pairs);
                return -EINVAL;
        } else {
                vi->curr_queue_pairs = queue_pairs;
                /* virtnet_open() will refill when device is going to up. */
                if (dev->flags & IFF_UP)
                        schedule_delayed_work(&vi->refill, 0);
        }

        return 0;
}

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

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

        for (i = 0; i < vi->max_queue_pairs; i++)
                napi_disable(&vi->rq[i].napi);

        return 0;
}

static void virtnet_set_rx_mode(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg[2];
        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 dynamically set ndo_set_rx_mode, so return gracefully */
        if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
                return;

        vi->ctrl_promisc = ((dev->flags & IFF_PROMISC) != 0);
        vi->ctrl_allmulti = ((dev->flags & IFF_ALLMULTI) != 0);

        sg_init_one(sg, &vi->ctrl_promisc, sizeof(vi->ctrl_promisc));

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

        sg_init_one(sg, &vi->ctrl_allmulti, sizeof(vi->ctrl_allmulti));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
                                  VIRTIO_NET_CTRL_RX_ALLMULTI, sg))
                dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
                         vi->ctrl_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)
                return;

        sg_init_table(sg, 2);

        /* Store the unicast list and count in the front of the buffer */
        mac_data->entries = cpu_to_virtio32(vi->vdev, 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 = cpu_to_virtio32(vi->vdev, 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))
                dev_warn(&dev->dev, "Failed to set MAC filter table.\n");

        kfree(buf);
}

static int virtnet_vlan_rx_add_vid(struct net_device *dev,
                                   __be16 proto, u16 vid)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg;

        vi->ctrl_vid = vid;
        sg_init_one(&sg, &vi->ctrl_vid, sizeof(vi->ctrl_vid));

        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
                                  VIRTIO_NET_CTRL_VLAN_ADD, &sg))
                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,
                                    __be16 proto, u16 vid)
{
        struct virtnet_info *vi = netdev_priv(dev);
        struct scatterlist sg;

        vi->ctrl_vid = vid;
        sg_init_one(&sg, &vi->ctrl_vid, sizeof(vi->ctrl_vid));

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

static void virtnet_clean_affinity(struct virtnet_info *vi, long hcpu)
{
        int i;

        if (vi->affinity_hint_set) {
                for (i = 0; i < vi->max_queue_pairs; i++) {
                        virtqueue_set_affinity(vi->rq[i].vq, -1);
                        virtqueue_set_affinity(vi->sq[i].vq, -1);
                }

                vi->affinity_hint_set = false;
        }
}

static void virtnet_set_affinity(struct virtnet_info *vi)
{
        int i;
        int cpu;

        /* In multiqueue mode, when the number of cpu is equal to the number of
         * queue pairs, we let the queue pairs to be private to one cpu by
         * setting the affinity hint to eliminate the contention.
         */
        if (vi->curr_queue_pairs == 1 ||
            vi->max_queue_pairs != num_online_cpus()) {
                virtnet_clean_affinity(vi, -1);
                return;
        }

        i = 0;
        for_each_online_cpu(cpu) {
                virtqueue_set_affinity(vi->rq[i].vq, cpu);
                virtqueue_set_affinity(vi->sq[i].vq, cpu);
                netif_set_xps_queue(vi->dev, cpumask_of(cpu), i);
                i++;
        }

        vi->affinity_hint_set = true;
}

static int virtnet_cpu_online(unsigned int cpu, struct hlist_node *node)
{
        struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
                                                   node);
        virtnet_set_affinity(vi);
        return 0;
}

static int virtnet_cpu_dead(unsigned int cpu, struct hlist_node *node)
{
        struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
                                                   node_dead);
        virtnet_set_affinity(vi);
        return 0;
}

static int virtnet_cpu_down_prep(unsigned int cpu, struct hlist_node *node)
{
        struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
                                                   node);

        virtnet_clean_affinity(vi, cpu);
        return 0;
}

static enum cpuhp_state virtionet_online;

static int virtnet_cpu_notif_add(struct virtnet_info *vi)
{
        int ret;

        ret = cpuhp_state_add_instance_nocalls(virtionet_online, &vi->node);
        if (ret)
                return ret;
        ret = cpuhp_state_add_instance_nocalls(CPUHP_VIRT_NET_DEAD,
                                               &vi->node_dead);
        if (!ret)
                return ret;
        cpuhp_state_remove_instance_nocalls(virtionet_online, &vi->node);
        return ret;
}

static void virtnet_cpu_notif_remove(struct virtnet_info *vi)
{
        cpuhp_state_remove_instance_nocalls(virtionet_online, &vi->node);
        cpuhp_state_remove_instance_nocalls(CPUHP_VIRT_NET_DEAD,
                                            &vi->node_dead);
}

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->rq[0].vq);
        ring->tx_max_pending = virtqueue_get_vring_size(vi->sq[0].vq);
        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));

}

/* TODO: Eliminate OOO packets during switching */
static int virtnet_set_channels(struct net_device *dev,
                                struct ethtool_channels *channels)
{
        struct virtnet_info *vi = netdev_priv(dev);
        u16 queue_pairs = channels->combined_count;
        int err;

        /* We don't support separate rx/tx channels.
         * We don't allow setting 'other' channels.
         */
        if (channels->rx_count || channels->tx_count || channels->other_count)
                return -EINVAL;

        if (queue_pairs > vi->max_queue_pairs || queue_pairs == 0)
                return -EINVAL;

        /* For now we don't support modifying channels while XDP is loaded
         * also when XDP is loaded all RX queues have XDP programs so we only
         * need to check a single RX queue.
         */
        if (vi->rq[0].xdp_prog)
                return -EINVAL;

        get_online_cpus();
        err = virtnet_set_queues(vi, queue_pairs);
        if (!err) {
                netif_set_real_num_tx_queues(dev, queue_pairs);
                netif_set_real_num_rx_queues(dev, queue_pairs);

                virtnet_set_affinity(vi);
        }
        put_online_cpus();

        return err;
}

static void virtnet_get_channels(struct net_device *dev,
                                 struct ethtool_channels *channels)
{
        struct virtnet_info *vi = netdev_priv(dev);

        channels->combined_count = vi->curr_queue_pairs;
        channels->max_combined = vi->max_queue_pairs;
        channels->max_other = 0;
        channels->rx_count = 0;
        channels->tx_count = 0;
        channels->other_count = 0;
}

/* Check if the user is trying to change anything besides speed/duplex */
static bool virtnet_validate_ethtool_cmd(const struct ethtool_cmd *cmd)
{
        struct ethtool_cmd diff1 = *cmd;
        struct ethtool_cmd diff2 = {};

        /* cmd is always set so we need to clear it, validate the port type
         * and also without autonegotiation we can ignore advertising
         */
        ethtool_cmd_speed_set(&diff1, 0);
        diff2.port = PORT_OTHER;
        diff1.advertising = 0;
        diff1.duplex = 0;
        diff1.cmd = 0;

        return !memcmp(&diff1, &diff2, sizeof(diff1));
}

static int virtnet_set_settings(struct net_device *dev, struct ethtool_cmd *cmd)
{
        struct virtnet_info *vi = netdev_priv(dev);
        u32 speed;

        speed = ethtool_cmd_speed(cmd);
        /* don't allow custom speed and duplex */
        if (!ethtool_validate_speed(speed) ||
            !ethtool_validate_duplex(cmd->duplex) ||
            !virtnet_validate_ethtool_cmd(cmd))
                return -EINVAL;
        vi->speed = speed;
        vi->duplex = cmd->duplex;

        return 0;
}

static int virtnet_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
{
        struct virtnet_info *vi = netdev_priv(dev);

        ethtool_cmd_speed_set(cmd, vi->speed);
        cmd->duplex = vi->duplex;
        cmd->port = PORT_OTHER;

        return 0;
}

static void virtnet_init_settings(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);

        vi->speed = SPEED_UNKNOWN;
        vi->duplex = DUPLEX_UNKNOWN;
}

static const struct ethtool_ops virtnet_ethtool_ops = {
        .get_drvinfo = virtnet_get_drvinfo,
        .get_link = ethtool_op_get_link,
        .get_ringparam = virtnet_get_ringparam,
        .set_channels = virtnet_set_channels,
        .get_channels = virtnet_get_channels,
        .get_ts_info = ethtool_op_get_ts_info,
        .get_settings = virtnet_get_settings,
        .set_settings = virtnet_set_settings,
};

static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog)
{
        unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr);
        struct virtnet_info *vi = netdev_priv(dev);
        struct bpf_prog *old_prog;
        u16 xdp_qp = 0, curr_qp;
        int i, err;

        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
            virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
            virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
            virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
                netdev_warn(dev, "can't set XDP while host is implementing LRO, disable LRO first\n");
                return -EOPNOTSUPP;
        }

        if (vi->mergeable_rx_bufs && !vi->any_header_sg) {
                netdev_warn(dev, "XDP expects header/data in single page, any_header_sg required\n");
                return -EINVAL;
        }

        if (dev->mtu > max_sz) {
                netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
                return -EINVAL;
        }

        curr_qp = vi->curr_queue_pairs - vi->xdp_queue_pairs;
        if (prog)
                xdp_qp = nr_cpu_ids;

        /* XDP requires extra queues for XDP_TX */
        if (curr_qp + xdp_qp > vi->max_queue_pairs) {
                netdev_warn(dev, "request %i queues but max is %i\n",
                            curr_qp + xdp_qp, vi->max_queue_pairs);
                return -ENOMEM;
        }

        err = virtnet_set_queues(vi, curr_qp + xdp_qp);
        if (err) {
                dev_warn(&dev->dev, "XDP Device queue allocation failure.\n");
                return err;
        }

        if (prog) {
                prog = bpf_prog_add(prog, vi->max_queue_pairs - 1);
                if (IS_ERR(prog)) {
                        virtnet_set_queues(vi, curr_qp);
                        return PTR_ERR(prog);
                }
        }

        vi->xdp_queue_pairs = xdp_qp;
        netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp);

        for (i = 0; i < vi->max_queue_pairs; i++) {
                old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
                rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
                if (old_prog)
                        bpf_prog_put(old_prog);
        }

        return 0;
}

static bool virtnet_xdp_query(struct net_device *dev)
{
        struct virtnet_info *vi = netdev_priv(dev);
        int i;

        for (i = 0; i < vi->max_queue_pairs; i++) {
                if (vi->rq[i].xdp_prog)
                        return true;
        }
        return false;
}

static int virtnet_xdp(struct net_device *dev, struct netdev_xdp *xdp)
{
        switch (xdp->command) {
        case XDP_SETUP_PROG:
                return virtnet_xdp_set(dev, xdp->prog);
        case XDP_QUERY_PROG:
                xdp->prog_attached = virtnet_xdp_query(dev);
                return 0;
        default:
                return -EINVAL;
        }
}

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_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
#ifdef CONFIG_NET_RX_BUSY_POLL
        .ndo_busy_poll          = virtnet_busy_poll,
#endif
        .ndo_xdp                = virtnet_xdp,
};

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

        if (virtio_cread_feature(vi->vdev, VIRTIO_NET_F_STATUS,
                                 struct virtio_net_config, status, &v) < 0)
                return;

        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)
                return;

        vi->status = v;

        if (vi->status & VIRTIO_NET_S_LINK_UP) {
                netif_carrier_on(vi->dev);
                netif_tx_wake_all_queues(vi->dev);
        } else {
                netif_carrier_off(vi->dev);
                netif_tx_stop_all_queues(vi->dev);
        }
}

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

        schedule_work(&vi->config_work);
}

static void virtnet_free_queues(struct virtnet_info *vi)
{
        int i;

        for (i = 0; i < vi->max_queue_pairs; i++) {
                napi_hash_del(&vi->rq[i].napi);
                netif_napi_del(&vi->rq[i].napi);
        }

        /* We called napi_hash_del() before netif_napi_del(),
         * we need to respect an RCU grace period before freeing vi->rq
         */
        synchronize_net();

        kfree(vi->rq);
        kfree(vi->sq);
}

static void free_receive_bufs(struct virtnet_info *vi)
{
        struct bpf_prog *old_prog;
        int i;

        rtnl_lock();
        for (i = 0; i < vi->max_queue_pairs; i++) {
                while (vi->rq[i].pages)
                        __free_pages(get_a_page(&vi->rq[i], GFP_KERNEL), 0);

                old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
                RCU_INIT_POINTER(vi->rq[i].xdp_prog, NULL);
                if (old_prog)
                        bpf_prog_put(old_prog);
        }
        rtnl_unlock();
}

static void free_receive_page_frags(struct virtnet_info *vi)
{
        int i;
        for (i = 0; i < vi->max_queue_pairs; i++)
                if (vi->rq[i].alloc_frag.page)
                        put_page(vi->rq[i].alloc_frag.page);
}

static bool is_xdp_queue(struct virtnet_info *vi, int q)
{
        if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
                return false;
        else if (q < vi->curr_queue_pairs)
                return true;
        else
                return false;
}

static void free_unused_bufs(struct virtnet_info *vi)
{
        void *buf;
        int i;

        for (i = 0; i < vi->max_queue_pairs; i++) {
                struct virtqueue *vq = vi->sq[i].vq;
                while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
                        if (!is_xdp_queue(vi, i))
                                dev_kfree_skb(buf);
                        else
                                put_page(virt_to_head_page(buf));
                }
        }

        for (i = 0; i < vi->max_queue_pairs; i++) {
                struct virtqueue *vq = vi->rq[i].vq;

                while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
                        if (vi->mergeable_rx_bufs) {
                                unsigned long ctx = (unsigned long)buf;
                                void *base = mergeable_ctx_to_buf_address(ctx);
                                put_page(virt_to_head_page(base));
                        } else if (vi->big_packets) {
                                give_pages(&vi->rq[i], buf);
                        } else {
                                dev_kfree_skb(buf);
                        }
                }
        }
}

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

        virtnet_clean_affinity(vi, -1);

        vdev->config->del_vqs(vdev);

        virtnet_free_queues(vi);
}

static int virtnet_find_vqs(struct virtnet_info *vi)
{
        vq_callback_t **callbacks;
        struct virtqueue **vqs;
        int ret = -ENOMEM;
        int i, total_vqs;
        const char **names;

        /* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by
         * possible N-1 RX/TX queue pairs used in multiqueue mode, followed by
         * possible control vq.
         */
        total_vqs = vi->max_queue_pairs * 2 +
                    virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ);

        /* Allocate space for find_vqs parameters */
        vqs = kzalloc(total_vqs * sizeof(*vqs), GFP_KERNEL);
        if (!vqs)
                goto err_vq;
        callbacks = kmalloc(total_vqs * sizeof(*callbacks), GFP_KERNEL);
        if (!callbacks)
                goto err_callback;
        names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
        if (!names)
                goto err_names;

        /* Parameters for control virtqueue, if any */
        if (vi->has_cvq) {
                callbacks[total_vqs - 1] = NULL;
                names[total_vqs - 1] = "control";
        }

        /* Allocate/initialize parameters for send/receive virtqueues */
        for (i = 0; i < vi->max_queue_pairs; i++) {
                callbacks[rxq2vq(i)] = skb_recv_done;
                callbacks[txq2vq(i)] = skb_xmit_done;
                sprintf(vi->rq[i].name, "input.%d", i);
                sprintf(vi->sq[i].name, "output.%d", i);
                names[rxq2vq(i)] = vi->rq[i].name;
                names[txq2vq(i)] = vi->sq[i].name;
        }

        ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
                                         names);
        if (ret)
                goto err_find;

        if (vi->has_cvq) {
                vi->cvq = vqs[total_vqs - 1];
                if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
                        vi->dev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
        }

        for (i = 0; i < vi->max_queue_pairs; i++) {
                vi->rq[i].vq = vqs[rxq2vq(i)];
                vi->sq[i].vq = vqs[txq2vq(i)];
        }

        kfree(names);
        kfree(callbacks);
        kfree(vqs);

        return 0;

err_find:
        kfree(names);
err_names:
        kfree(callbacks);
err_callback:
        kfree(vqs);
err_vq:
        return ret;
}

static int virtnet_alloc_queues(struct virtnet_info *vi)
{
        int i;

        vi->sq = kzalloc(sizeof(*vi->sq) * vi->max_queue_pairs, GFP_KERNEL);
        if (!vi->sq)
                goto err_sq;
        vi->rq = kzalloc(sizeof(*vi->rq) * vi->max_queue_pairs, GFP_KERNEL);
        if (!vi->rq)
                goto err_rq;

        INIT_DELAYED_WORK(&vi->refill, refill_work);
        for (i = 0; i < vi->max_queue_pairs; i++) {
                vi->rq[i].pages = NULL;
                netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll,
                               napi_weight);

                sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
                ewma_pkt_len_init(&vi->rq[i].mrg_avg_pkt_len);
                sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
        }

        return 0;

err_rq:
        kfree(vi->sq);
err_sq:
        return -ENOMEM;
}

static int init_vqs(struct virtnet_info *vi)
{
        int ret;

        /* Allocate send & receive queues */
        ret = virtnet_alloc_queues(vi);
        if (ret)
                goto err;

        ret = virtnet_find_vqs(vi);
        if (ret)
                goto err_free;

        get_online_cpus();
        virtnet_set_affinity(vi);
        put_online_cpus();

        return 0;

err_free:
        virtnet_free_queues(vi);
err:
        return ret;
}

#ifdef CONFIG_SYSFS
static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
                struct rx_queue_attribute *attribute, char *buf)
{
        struct virtnet_info *vi = netdev_priv(queue->dev);
        unsigned int queue_index = get_netdev_rx_queue_index(queue);
        struct ewma_pkt_len *avg;

        BUG_ON(queue_index >= vi->max_queue_pairs);
        avg = &vi->rq[queue_index].mrg_avg_pkt_len;
        return sprintf(buf, "%u\n", get_mergeable_buf_len(avg));
}

static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =
        __ATTR_RO(mergeable_rx_buffer_size);

static struct attribute *virtio_net_mrg_rx_attrs[] = {
        &mergeable_rx_buffer_size_attribute.attr,
        NULL
};

static const struct attribute_group virtio_net_mrg_rx_group = {
        .name = "virtio_net",
        .attrs = virtio_net_mrg_rx_attrs
};
#endif

static bool virtnet_fail_on_feature(struct virtio_device *vdev,
                                    unsigned int fbit,
                                    const char *fname, const char *dname)
{
        if (!virtio_has_feature(vdev, fbit))
                return false;

        dev_err(&vdev->dev, "device advertises feature %s but not %s",
                fname, dname);

        return true;
}

#define VIRTNET_FAIL_ON(vdev, fbit, dbit)                       \
        virtnet_fail_on_feature(vdev, fbit, #fbit, dbit)

static bool virtnet_validate_features(struct virtio_device *vdev)
{
        if (!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) &&
            (VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_RX,
                             "VIRTIO_NET_F_CTRL_VQ") ||
             VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_VLAN,
                             "VIRTIO_NET_F_CTRL_VQ") ||
             VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE,
                             "VIRTIO_NET_F_CTRL_VQ") ||
             VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_MQ, "VIRTIO_NET_F_CTRL_VQ") ||
             VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR,
                             "VIRTIO_NET_F_CTRL_VQ"))) {
                return false;
        }

        return true;
}

#define MIN_MTU ETH_MIN_MTU
#define MAX_MTU ETH_MAX_MTU

static int virtnet_probe(struct virtio_device *vdev)
{
        int i, err;
        struct net_device *dev;
        struct virtnet_info *vi;
        u16 max_queue_pairs;
        int mtu;

        if (!vdev->config->get) {
                dev_err(&vdev->dev, "%s failure: config access disabled\n",
                        __func__);
                return -EINVAL;
        }

        if (!virtnet_validate_features(vdev))
                return -EINVAL;

        /* Find if host supports multiqueue virtio_net device */
        err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
                                   struct virtio_net_config,
                                   max_virtqueue_pairs, &max_queue_pairs);

        /* We need at least 2 queue's */
        if (err || max_queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
            max_queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX ||
            !virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
                max_queue_pairs = 1;

        /* Allocate ourselves a network device with room for our info */
        dev = alloc_etherdev_mq(sizeof(struct virtnet_info), max_queue_pairs);
        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;

        dev->ethtool_ops = &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;
                if (csum)
                        dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;

                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;

                dev->features |= NETIF_F_GSO_ROBUST;

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

        dev->vlan_features = dev->features;

        /* MTU range: 68 - 65535 */
        dev->min_mtu = MIN_MTU;
        dev->max_mtu = MAX_MTU;

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

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

        for_each_possible_cpu(i) {
                struct virtnet_stats *virtnet_stats;
                virtnet_stats = per_cpu_ptr(vi->stats, i);
                u64_stats_init(&virtnet_stats->tx_syncp);
                u64_stats_init(&virtnet_stats->rx_syncp);
        }

        INIT_WORK(&vi->config_work, virtnet_config_changed_work);

        /* 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) ||
            virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_UFO))
                vi->big_packets = true;

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

        if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF) ||
            virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
                vi->hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
        else
                vi->hdr_len = sizeof(struct virtio_net_hdr);

        if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT) ||
            virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
                vi->any_header_sg = true;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
                vi->has_cvq = true;

        if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
                mtu = virtio_cread16(vdev,
                                     offsetof(struct virtio_net_config,
                                              mtu));
                if (mtu < dev->min_mtu) {
                        __virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
                } else {
                        dev->mtu = mtu;
                        dev->max_mtu = mtu;
                }
        }

        if (vi->any_header_sg)
                dev->needed_headroom = vi->hdr_len;

        /* Enable multiqueue by default */
        if (num_online_cpus() >= max_queue_pairs)
                vi->curr_queue_pairs = max_queue_pairs;
        else
                vi->curr_queue_pairs = num_online_cpus();
        vi->max_queue_pairs = max_queue_pairs;

        /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
        err = init_vqs(vi);
        if (err)
                goto free_stats;

#ifdef CONFIG_SYSFS
        if (vi->mergeable_rx_bufs)
                dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
#endif
        netif_set_real_num_tx_queues(dev, vi->curr_queue_pairs);
        netif_set_real_num_rx_queues(dev, vi->curr_queue_pairs);

        virtnet_init_settings(dev);

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

        virtio_device_ready(vdev);

        err = virtnet_cpu_notif_add(vi);
        if (err) {
                pr_debug("virtio_net: registering cpu notifier failed\n");
                goto free_unregister_netdev;
        }

        rtnl_lock();
        virtnet_set_queues(vi, vi->curr_queue_pairs);
        rtnl_unlock();

        /* 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 with %d RX and TX vq's\n",
                 dev->name, max_queue_pairs);

        return 0;

free_unregister_netdev:
        vi->vdev->config->reset(vdev);

        unregister_netdev(dev);
free_vqs:
        cancel_delayed_work_sync(&vi->refill);
        free_receive_page_frags(vi);
        virtnet_del_vqs(vi);
free_stats:
        free_percpu(vi->stats);
free:
        free_netdev(dev);
        return err;
}

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);

        free_receive_bufs(vi);

        free_receive_page_frags(vi);

        virtnet_del_vqs(vi);
}

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

        virtnet_cpu_notif_remove(vi);

        /* Make sure no work handler is accessing the device. */
        flush_work(&vi->config_work);

        unregister_netdev(vi->dev);

        remove_vq_common(vi);

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

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

        virtnet_cpu_notif_remove(vi);

        /* Make sure no work handler is accessing the device */
        flush_work(&vi->config_work);

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

        if (netif_running(vi->dev)) {
                for (i = 0; i < vi->max_queue_pairs; i++)
                        napi_disable(&vi->rq[i].napi);
        }

        remove_vq_common(vi);

        return 0;
}

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

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

        virtio_device_ready(vdev);

        if (netif_running(vi->dev)) {
                for (i = 0; i < vi->curr_queue_pairs; i++)
                        if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
                                schedule_delayed_work(&vi->refill, 0);

                for (i = 0; i < vi->max_queue_pairs; i++)
                        virtnet_napi_enable(&vi->rq[i]);
        }

        netif_device_attach(vi->dev);

        rtnl_lock();
        virtnet_set_queues(vi, vi->curr_queue_pairs);
        rtnl_unlock();

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

        return 0;
}
#endif

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

#define VIRTNET_FEATURES \
        VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM, \
        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, VIRTIO_NET_F_MQ, \
        VIRTIO_NET_F_CTRL_MAC_ADDR, \
        VIRTIO_NET_F_MTU

static unsigned int features[] = {
        VIRTNET_FEATURES,
};

static unsigned int features_legacy[] = {
        VIRTNET_FEATURES,
        VIRTIO_NET_F_GSO,
        VIRTIO_F_ANY_LAYOUT,
};

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

static __init int virtio_net_driver_init(void)
{
        int ret;

        ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "AP_VIRT_NET_ONLINE",
                                      virtnet_cpu_online,
                                      virtnet_cpu_down_prep);
        if (ret < 0)
                goto out;
        virtionet_online = ret;
        ret = cpuhp_setup_state_multi(CPUHP_VIRT_NET_DEAD, "VIRT_NET_DEAD",
                                      NULL, virtnet_cpu_dead);
        if (ret)
                goto err_dead;

        ret = register_virtio_driver(&virtio_net_driver);
        if (ret)
                goto err_virtio;
        return 0;
err_virtio:
        cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
err_dead:
        cpuhp_remove_multi_state(virtionet_online);
out:
        return ret;
}
module_init(virtio_net_driver_init);

static __exit void virtio_net_driver_exit(void)
{
        cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
        cpuhp_remove_multi_state(virtionet_online);
        unregister_virtio_driver(&virtio_net_driver);
}
module_exit(virtio_net_driver_exit);

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