/*
 * Network-device interface management.
 *
 * Copyright (c) 2004-2005, Keir Fraser
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "common.h"

#include <linux/kthread.h>
#include <linux/sched/task.h>
#include <linux/ethtool.h>
#include <linux/rtnetlink.h>
#include <linux/if_vlan.h>
#include <linux/vmalloc.h>

#include <xen/events.h>
#include <asm/xen/hypercall.h>
#include <xen/balloon.h>

/* Number of bytes allowed on the internal guest Rx queue. */
#define XENVIF_RX_QUEUE_BYTES (XEN_NETIF_RX_RING_SIZE/2 * PAGE_SIZE)

/* This function is used to set SKBFL_ZEROCOPY_ENABLE as well as
 * increasing the inflight counter. We need to increase the inflight
 * counter because core driver calls into xenvif_zerocopy_callback
 * which calls xenvif_skb_zerocopy_complete.
 */
void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
                                 struct sk_buff *skb)
{
        skb_shinfo(skb)->flags |= SKBFL_ZEROCOPY_ENABLE;
        atomic_inc(&queue->inflight_packets);
}

void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
{
        atomic_dec(&queue->inflight_packets);

        /* Wake the dealloc thread _after_ decrementing inflight_packets so
         * that if kthread_stop() has already been called, the dealloc thread
         * does not wait forever with nothing to wake it.
         */
        wake_up(&queue->dealloc_wq);
}

static int xenvif_schedulable(struct xenvif *vif)
{
        return netif_running(vif->dev) &&
                test_bit(VIF_STATUS_CONNECTED, &vif->status) &&
                !vif->disabled;
}

static bool xenvif_handle_tx_interrupt(struct xenvif_queue *queue)
{
        bool rc;

        rc = RING_HAS_UNCONSUMED_REQUESTS(&queue->tx);
        if (rc)
                napi_schedule(&queue->napi);
        return rc;
}

static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
{
        struct xenvif_queue *queue = dev_id;
        int old;

        old = atomic_fetch_or(NETBK_TX_EOI, &queue->eoi_pending);
        WARN(old & NETBK_TX_EOI, "Interrupt while EOI pending\n");

        if (!xenvif_handle_tx_interrupt(queue)) {
                atomic_andnot(NETBK_TX_EOI, &queue->eoi_pending);
                xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
        }

        return IRQ_HANDLED;
}

static int xenvif_poll(struct napi_struct *napi, int budget)
{
        struct xenvif_queue *queue =
                container_of(napi, struct xenvif_queue, napi);
        int work_done;

        /* This vif is rogue, we pretend we've there is nothing to do
         * for this vif to deschedule it from NAPI. But this interface
         * will be turned off in thread context later.
         */
        if (unlikely(queue->vif->disabled)) {
                napi_complete(napi);
                return 0;
        }

        work_done = xenvif_tx_action(queue, budget);

        if (work_done < budget) {
                napi_complete_done(napi, work_done);
                /* If the queue is rate-limited, it shall be
                 * rescheduled in the timer callback.
                 */
                if (likely(!queue->rate_limited))
                        xenvif_napi_schedule_or_enable_events(queue);
        }

        return work_done;
}

static bool xenvif_handle_rx_interrupt(struct xenvif_queue *queue)
{
        bool rc;

        rc = xenvif_have_rx_work(queue, false);
        if (rc)
                xenvif_kick_thread(queue);
        return rc;
}

static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
{
        struct xenvif_queue *queue = dev_id;
        int old;

        old = atomic_fetch_or(NETBK_RX_EOI, &queue->eoi_pending);
        WARN(old & NETBK_RX_EOI, "Interrupt while EOI pending\n");

        if (!xenvif_handle_rx_interrupt(queue)) {
                atomic_andnot(NETBK_RX_EOI, &queue->eoi_pending);
                xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
        }

        return IRQ_HANDLED;
}

irqreturn_t xenvif_interrupt(int irq, void *dev_id)
{
        struct xenvif_queue *queue = dev_id;
        int old;
        bool has_rx, has_tx;

        old = atomic_fetch_or(NETBK_COMMON_EOI, &queue->eoi_pending);
        WARN(old, "Interrupt while EOI pending\n");

        has_tx = xenvif_handle_tx_interrupt(queue);
        has_rx = xenvif_handle_rx_interrupt(queue);

        if (!has_rx && !has_tx) {
                atomic_andnot(NETBK_COMMON_EOI, &queue->eoi_pending);
                xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
        }

        return IRQ_HANDLED;
}

static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb,
                               struct net_device *sb_dev)
{
        struct xenvif *vif = netdev_priv(dev);
        unsigned int size = vif->hash.size;
        unsigned int num_queues;

        /* If queues are not set up internally - always return 0
         * as the packet going to be dropped anyway */
        num_queues = READ_ONCE(vif->num_queues);
        if (num_queues < 1)
                return 0;

        if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
                return netdev_pick_tx(dev, skb, NULL) %
                       dev->real_num_tx_queues;

        xenvif_set_skb_hash(vif, skb);

        if (size == 0)
                return skb_get_hash_raw(skb) % dev->real_num_tx_queues;

        return vif->hash.mapping[vif->hash.mapping_sel]
                                [skb_get_hash_raw(skb) % size];
}

static netdev_tx_t
xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct xenvif *vif = netdev_priv(dev);
        struct xenvif_queue *queue = NULL;
        unsigned int num_queues;
        u16 index;
        struct xenvif_rx_cb *cb;

        BUG_ON(skb->dev != dev);

        /* Drop the packet if queues are not set up.
         * This handler should be called inside an RCU read section
         * so we don't need to enter it here explicitly.
         */
        num_queues = READ_ONCE(vif->num_queues);
        if (num_queues < 1)
                goto drop;

        /* Obtain the queue to be used to transmit this packet */
        index = skb_get_queue_mapping(skb);
        if (index >= num_queues) {
                pr_warn_ratelimited("Invalid queue %hu for packet on interface %s\n",
                                    index, vif->dev->name);
                index %= num_queues;
        }
        queue = &vif->queues[index];

        /* Drop the packet if queue is not ready */
        if (queue->task == NULL ||
            queue->dealloc_task == NULL ||
            !xenvif_schedulable(vif))
                goto drop;

        if (vif->multicast_control && skb->pkt_type == PACKET_MULTICAST) {
                struct ethhdr *eth = (struct ethhdr *)skb->data;

                if (!xenvif_mcast_match(vif, eth->h_dest))
                        goto drop;
        }

        cb = XENVIF_RX_CB(skb);
        cb->expires = jiffies + vif->drain_timeout;

        /* If there is no hash algorithm configured then make sure there
         * is no hash information in the socket buffer otherwise it
         * would be incorrectly forwarded to the frontend.
         */
        if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
                skb_clear_hash(skb);

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

        if (!xenvif_rx_queue_tail(queue, skb))
                goto drop;

        xenvif_kick_thread(queue);

        return NETDEV_TX_OK;

 drop:
        vif->dev->stats.tx_dropped++;
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
}

static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
{
        struct xenvif *vif = netdev_priv(dev);
        struct xenvif_queue *queue = NULL;
        unsigned int num_queues;
        u64 rx_bytes = 0;
        u64 rx_packets = 0;
        u64 tx_bytes = 0;
        u64 tx_packets = 0;
        unsigned int index;

        rcu_read_lock();
        num_queues = READ_ONCE(vif->num_queues);

        /* Aggregate tx and rx stats from each queue */
        for (index = 0; index < num_queues; ++index) {
                queue = &vif->queues[index];
                rx_bytes += queue->stats.rx_bytes;
                rx_packets += queue->stats.rx_packets;
                tx_bytes += queue->stats.tx_bytes;
                tx_packets += queue->stats.tx_packets;
        }

        rcu_read_unlock();

        vif->dev->stats.rx_bytes = rx_bytes;
        vif->dev->stats.rx_packets = rx_packets;
        vif->dev->stats.tx_bytes = tx_bytes;
        vif->dev->stats.tx_packets = tx_packets;

        return &vif->dev->stats;
}

static void xenvif_up(struct xenvif *vif)
{
        struct xenvif_queue *queue = NULL;
        unsigned int num_queues = vif->num_queues;
        unsigned int queue_index;

        for (queue_index = 0; queue_index < num_queues; ++queue_index) {
                queue = &vif->queues[queue_index];
                napi_enable(&queue->napi);
                enable_irq(queue->tx_irq);
                if (queue->tx_irq != queue->rx_irq)
                        enable_irq(queue->rx_irq);
                xenvif_napi_schedule_or_enable_events(queue);
        }
}

static void xenvif_down(struct xenvif *vif)
{
        struct xenvif_queue *queue = NULL;
        unsigned int num_queues = vif->num_queues;
        unsigned int queue_index;

        for (queue_index = 0; queue_index < num_queues; ++queue_index) {
                queue = &vif->queues[queue_index];
                disable_irq(queue->tx_irq);
                if (queue->tx_irq != queue->rx_irq)
                        disable_irq(queue->rx_irq);
                napi_disable(&queue->napi);
                timer_delete_sync(&queue->credit_timeout);
        }
}

static int xenvif_open(struct net_device *dev)
{
        struct xenvif *vif = netdev_priv(dev);
        if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
                xenvif_up(vif);
        netif_tx_start_all_queues(dev);
        return 0;
}

static int xenvif_close(struct net_device *dev)
{
        struct xenvif *vif = netdev_priv(dev);
        if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
                xenvif_down(vif);
        netif_tx_stop_all_queues(dev);
        return 0;
}

static int xenvif_change_mtu(struct net_device *dev, int mtu)
{
        struct xenvif *vif = netdev_priv(dev);
        int max = vif->can_sg ? ETH_MAX_MTU - VLAN_ETH_HLEN : ETH_DATA_LEN;

        if (mtu > max)
                return -EINVAL;
        WRITE_ONCE(dev->mtu, mtu);
        return 0;
}

static netdev_features_t xenvif_fix_features(struct net_device *dev,
        netdev_features_t features)
{
        struct xenvif *vif = netdev_priv(dev);

        if (!vif->can_sg)
                features &= ~NETIF_F_SG;
        if (~(vif->gso_mask) & GSO_BIT(TCPV4))
                features &= ~NETIF_F_TSO;
        if (~(vif->gso_mask) & GSO_BIT(TCPV6))
                features &= ~NETIF_F_TSO6;
        if (!vif->ip_csum)
                features &= ~NETIF_F_IP_CSUM;
        if (!vif->ipv6_csum)
                features &= ~NETIF_F_IPV6_CSUM;

        return features;
}

static const struct xenvif_stat {
        char name[ETH_GSTRING_LEN];
        u16 offset;
} xenvif_stats[] = {
        {
                "rx_gso_checksum_fixup",
                offsetof(struct xenvif_stats, rx_gso_checksum_fixup)
        },
        /* If (sent != success + fail), there are probably packets never
         * freed up properly!
         */
        {
                "tx_zerocopy_sent",
                offsetof(struct xenvif_stats, tx_zerocopy_sent),
        },
        {
                "tx_zerocopy_success",
                offsetof(struct xenvif_stats, tx_zerocopy_success),
        },
        {
                "tx_zerocopy_fail",
                offsetof(struct xenvif_stats, tx_zerocopy_fail)
        },
        /* Number of packets exceeding MAX_SKB_FRAG slots. You should use
         * a guest with the same MAX_SKB_FRAG
         */
        {
                "tx_frag_overflow",
                offsetof(struct xenvif_stats, tx_frag_overflow)
        },
};

static int xenvif_get_sset_count(struct net_device *dev, int string_set)
{
        switch (string_set) {
        case ETH_SS_STATS:
                return ARRAY_SIZE(xenvif_stats);
        default:
                return -EINVAL;
        }
}

static void xenvif_get_ethtool_stats(struct net_device *dev,
                                     struct ethtool_stats *stats, u64 * data)
{
        struct xenvif *vif = netdev_priv(dev);
        unsigned int num_queues;
        int i;
        unsigned int queue_index;

        rcu_read_lock();
        num_queues = READ_ONCE(vif->num_queues);

        for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++) {
                unsigned long accum = 0;
                for (queue_index = 0; queue_index < num_queues; ++queue_index) {
                        void *vif_stats = &vif->queues[queue_index].stats;
                        accum += *(unsigned long *)(vif_stats + xenvif_stats[i].offset);
                }
                data[i] = accum;
        }

        rcu_read_unlock();
}

static void xenvif_get_strings(struct net_device *dev, u32 stringset, u8 * data)
{
        int i;

        switch (stringset) {
        case ETH_SS_STATS:
                for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++)
                        memcpy(data + i * ETH_GSTRING_LEN,
                               xenvif_stats[i].name, ETH_GSTRING_LEN);
                break;
        }
}

static const struct ethtool_ops xenvif_ethtool_ops = {
        .get_link       = ethtool_op_get_link,
        .get_ts_info    = ethtool_op_get_ts_info,
        .get_sset_count = xenvif_get_sset_count,
        .get_ethtool_stats = xenvif_get_ethtool_stats,
        .get_strings = xenvif_get_strings,
};

static const struct net_device_ops xenvif_netdev_ops = {
        .ndo_select_queue = xenvif_select_queue,
        .ndo_start_xmit = xenvif_start_xmit,
        .ndo_get_stats  = xenvif_get_stats,
        .ndo_open       = xenvif_open,
        .ndo_stop       = xenvif_close,
        .ndo_change_mtu = xenvif_change_mtu,
        .ndo_fix_features = xenvif_fix_features,
        .ndo_set_mac_address = eth_mac_addr,
        .ndo_validate_addr   = eth_validate_addr,
};

struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
                            unsigned int handle)
{
        static const u8 dummy_addr[ETH_ALEN] = {
                0xfe, 0xff, 0xff, 0xff, 0xff, 0xff,
        };
        int err;
        struct net_device *dev;
        struct xenvif *vif;
        char name[IFNAMSIZ] = {};

        snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
        /* Allocate a netdev with the max. supported number of queues.
         * When the guest selects the desired number, it will be updated
         * via netif_set_real_num_*_queues().
         */
        dev = alloc_netdev_mq(sizeof(struct xenvif), name, NET_NAME_UNKNOWN,
                              ether_setup, xenvif_max_queues);
        if (dev == NULL) {
                pr_warn("Could not allocate netdev for %s\n", name);
                return ERR_PTR(-ENOMEM);
        }

        SET_NETDEV_DEV(dev, parent);

        vif = netdev_priv(dev);

        vif->domid  = domid;
        vif->handle = handle;
        vif->can_sg = 1;
        vif->ip_csum = 1;
        vif->dev = dev;
        vif->disabled = false;
        vif->drain_timeout = msecs_to_jiffies(rx_drain_timeout_msecs);
        vif->stall_timeout = msecs_to_jiffies(rx_stall_timeout_msecs);

        /* Start out with no queues. */
        vif->queues = NULL;
        vif->num_queues = 0;

        vif->xdp_headroom = 0;

        spin_lock_init(&vif->lock);
        INIT_LIST_HEAD(&vif->fe_mcast_addr);

        dev->netdev_ops = &xenvif_netdev_ops;
        dev->hw_features = NETIF_F_SG |
                NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
                NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_FRAGLIST;
        dev->features = dev->hw_features | NETIF_F_RXCSUM;
        dev->ethtool_ops = &xenvif_ethtool_ops;

        dev->min_mtu = ETH_MIN_MTU;
        dev->max_mtu = ETH_MAX_MTU - VLAN_ETH_HLEN;

        /*
         * Initialise a dummy MAC address. We choose the numerically
         * largest non-broadcast address to prevent the address getting
         * stolen by an Ethernet bridge for STP purposes.
         * (FE:FF:FF:FF:FF:FF)
         */
        eth_hw_addr_set(dev, dummy_addr);

        netif_carrier_off(dev);

        err = register_netdev(dev);
        if (err) {
                netdev_warn(dev, "Could not register device: err=%d\n", err);
                free_netdev(dev);
                return ERR_PTR(err);
        }

        netdev_dbg(dev, "Successfully created xenvif\n");

        __module_get(THIS_MODULE);

        return vif;
}

int xenvif_init_queue(struct xenvif_queue *queue)
{
        int err, i;

        queue->credit_bytes = queue->remaining_credit = ~0UL;
        queue->credit_usec  = 0UL;
        timer_setup(&queue->credit_timeout, xenvif_tx_credit_callback, 0);
        queue->credit_window_start = get_jiffies_64();

        queue->rx_queue_max = XENVIF_RX_QUEUE_BYTES;

        skb_queue_head_init(&queue->rx_queue);
        skb_queue_head_init(&queue->tx_queue);

        queue->pending_cons = 0;
        queue->pending_prod = MAX_PENDING_REQS;
        for (i = 0; i < MAX_PENDING_REQS; ++i)
                queue->pending_ring[i] = i;

        spin_lock_init(&queue->callback_lock);
        spin_lock_init(&queue->response_lock);

        /* If ballooning is disabled, this will consume real memory, so you
         * better enable it. The long term solution would be to use just a
         * bunch of valid page descriptors, without dependency on ballooning
         */
        err = gnttab_alloc_pages(MAX_PENDING_REQS,
                                 queue->mmap_pages);
        if (err) {
                netdev_err(queue->vif->dev, "Could not reserve mmap_pages\n");
                return -ENOMEM;
        }

        for (i = 0; i < MAX_PENDING_REQS; i++) {
                queue->pending_tx_info[i].callback_struct = (struct ubuf_info_msgzc)
                        { { .ops = &xenvif_ubuf_ops },
                          { { .ctx = NULL,
                              .desc = i } } };
                queue->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
        }

        return 0;
}

void xenvif_carrier_on(struct xenvif *vif)
{
        rtnl_lock();
        if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
                dev_set_mtu(vif->dev, ETH_DATA_LEN);
        netdev_update_features(vif->dev);
        set_bit(VIF_STATUS_CONNECTED, &vif->status);
        if (netif_running(vif->dev))
                xenvif_up(vif);
        rtnl_unlock();
}

int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref,
                        unsigned int evtchn)
{
        struct net_device *dev = vif->dev;
        struct xenbus_device *xendev = xenvif_to_xenbus_device(vif);
        void *addr;
        struct xen_netif_ctrl_sring *shared;
        RING_IDX rsp_prod, req_prod;
        int err;

        err = xenbus_map_ring_valloc(xendev, &ring_ref, 1, &addr);
        if (err)
                goto err;

        shared = (struct xen_netif_ctrl_sring *)addr;
        rsp_prod = READ_ONCE(shared->rsp_prod);
        req_prod = READ_ONCE(shared->req_prod);

        BACK_RING_ATTACH(&vif->ctrl, shared, rsp_prod, XEN_PAGE_SIZE);

        err = -EIO;
        if (req_prod - rsp_prod > RING_SIZE(&vif->ctrl))
                goto err_unmap;

        err = bind_interdomain_evtchn_to_irq_lateeoi(xendev, evtchn);
        if (err < 0)
                goto err_unmap;

        vif->ctrl_irq = err;

        xenvif_init_hash(vif);

        err = request_threaded_irq(vif->ctrl_irq, NULL, xenvif_ctrl_irq_fn,
                                   IRQF_ONESHOT, "xen-netback-ctrl", vif);
        if (err) {
                pr_warn("Could not setup irq handler for %s\n", dev->name);
                goto err_deinit;
        }

        return 0;

err_deinit:
        xenvif_deinit_hash(vif);
        unbind_from_irqhandler(vif->ctrl_irq, vif);
        vif->ctrl_irq = 0;

err_unmap:
        xenbus_unmap_ring_vfree(xendev, vif->ctrl.sring);
        vif->ctrl.sring = NULL;

err:
        return err;
}

static void xenvif_disconnect_queue(struct xenvif_queue *queue)
{
        if (queue->task) {
                kthread_stop_put(queue->task);
                queue->task = NULL;
        }

        if (queue->dealloc_task) {
                kthread_stop(queue->dealloc_task);
                queue->dealloc_task = NULL;
        }

        if (queue->napi.poll) {
                netif_napi_del(&queue->napi);
                queue->napi.poll = NULL;
        }

        if (queue->tx_irq) {
                unbind_from_irqhandler(queue->tx_irq, queue);
                if (queue->tx_irq == queue->rx_irq)
                        queue->rx_irq = 0;
                queue->tx_irq = 0;
        }

        if (queue->rx_irq) {
                unbind_from_irqhandler(queue->rx_irq, queue);
                queue->rx_irq = 0;
        }

        xenvif_unmap_frontend_data_rings(queue);
}

int xenvif_connect_data(struct xenvif_queue *queue,
                        unsigned long tx_ring_ref,
                        unsigned long rx_ring_ref,
                        unsigned int tx_evtchn,
                        unsigned int rx_evtchn)
{
        struct xenbus_device *dev = xenvif_to_xenbus_device(queue->vif);
        struct task_struct *task;
        int err;

        BUG_ON(queue->tx_irq);
        BUG_ON(queue->task);
        BUG_ON(queue->dealloc_task);

        err = xenvif_map_frontend_data_rings(queue, tx_ring_ref,
                                             rx_ring_ref);
        if (err < 0)
                goto err;

        init_waitqueue_head(&queue->wq);
        init_waitqueue_head(&queue->dealloc_wq);
        atomic_set(&queue->inflight_packets, 0);

        netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll);

        queue->stalled = true;

        task = kthread_run(xenvif_kthread_guest_rx, queue,
                           "%s-guest-rx", queue->name);
        if (IS_ERR(task))
                goto kthread_err;
        queue->task = task;
        /*
         * Take a reference to the task in order to prevent it from being freed
         * if the thread function returns before kthread_stop is called.
         */
        get_task_struct(task);

        task = kthread_run(xenvif_dealloc_kthread, queue,
                           "%s-dealloc", queue->name);
        if (IS_ERR(task))
                goto kthread_err;
        queue->dealloc_task = task;

        if (tx_evtchn == rx_evtchn) {
                /* feature-split-event-channels == 0 */
                err = bind_interdomain_evtchn_to_irqhandler_lateeoi(
                        dev, tx_evtchn, xenvif_interrupt, 0,
                        queue->name, queue);
                if (err < 0)
                        goto err;
                queue->tx_irq = queue->rx_irq = err;
                disable_irq(queue->tx_irq);
        } else {
                /* feature-split-event-channels == 1 */
                snprintf(queue->tx_irq_name, sizeof(queue->tx_irq_name),
                         "%s-tx", queue->name);
                err = bind_interdomain_evtchn_to_irqhandler_lateeoi(
                        dev, tx_evtchn, xenvif_tx_interrupt, 0,
                        queue->tx_irq_name, queue);
                if (err < 0)
                        goto err;
                queue->tx_irq = err;
                disable_irq(queue->tx_irq);

                snprintf(queue->rx_irq_name, sizeof(queue->rx_irq_name),
                         "%s-rx", queue->name);
                err = bind_interdomain_evtchn_to_irqhandler_lateeoi(
                        dev, rx_evtchn, xenvif_rx_interrupt, 0,
                        queue->rx_irq_name, queue);
                if (err < 0)
                        goto err;
                queue->rx_irq = err;
                disable_irq(queue->rx_irq);
        }

        return 0;

kthread_err:
        pr_warn("Could not allocate kthread for %s\n", queue->name);
        err = PTR_ERR(task);
err:
        xenvif_disconnect_queue(queue);
        return err;
}

void xenvif_carrier_off(struct xenvif *vif)
{
        struct net_device *dev = vif->dev;

        rtnl_lock();
        if (test_and_clear_bit(VIF_STATUS_CONNECTED, &vif->status)) {
                netif_carrier_off(dev); /* discard queued packets */
                if (netif_running(dev))
                        xenvif_down(vif);
        }
        rtnl_unlock();
}

void xenvif_disconnect_data(struct xenvif *vif)
{
        struct xenvif_queue *queue = NULL;
        unsigned int num_queues = vif->num_queues;
        unsigned int queue_index;

        xenvif_carrier_off(vif);

        for (queue_index = 0; queue_index < num_queues; ++queue_index) {
                queue = &vif->queues[queue_index];

                xenvif_disconnect_queue(queue);
        }

        xenvif_mcast_addr_list_free(vif);
}

void xenvif_disconnect_ctrl(struct xenvif *vif)
{
        if (vif->ctrl_irq) {
                xenvif_deinit_hash(vif);
                unbind_from_irqhandler(vif->ctrl_irq, vif);
                vif->ctrl_irq = 0;
        }

        if (vif->ctrl.sring) {
                xenbus_unmap_ring_vfree(xenvif_to_xenbus_device(vif),
                                        vif->ctrl.sring);
                vif->ctrl.sring = NULL;
        }
}

/* Reverse the relevant parts of xenvif_init_queue().
 * Used for queue teardown from xenvif_free(), and on the
 * error handling paths in xenbus.c:connect().
 */
void xenvif_deinit_queue(struct xenvif_queue *queue)
{
        gnttab_free_pages(MAX_PENDING_REQS, queue->mmap_pages);
}

void xenvif_free(struct xenvif *vif)
{
        struct xenvif_queue *queues = vif->queues;
        unsigned int num_queues = vif->num_queues;
        unsigned int queue_index;

        unregister_netdev(vif->dev);
        free_netdev(vif->dev);

        for (queue_index = 0; queue_index < num_queues; ++queue_index)
                xenvif_deinit_queue(&queues[queue_index]);
        vfree(queues);

        module_put(THIS_MODULE);
}