OSCL-LXR linux-6.0.1/​drivers/​net/​xen-netfront.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /*
  * Virtual network driver for conversing with remote driver backends.
  *
  * Copyright (c) 2002-2005, K A Fraser
  * Copyright (c) 2005, XenSource Ltd
  *
  * 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.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/skbuff.h>
 #include <linux/ethtool.h>
 #include <linux/if_ether.h>
 #include <net/tcp.h>
 #include <linux/udp.h>
 #include <linux/moduleparam.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <net/ip.h>
 #include <linux/bpf.h>
 #include <net/page_pool.h>
 #include <linux/bpf_trace.h>
 
 #include <xen/xen.h>
 #include <xen/xenbus.h>
 #include <xen/events.h>
 #include <xen/page.h>
 #include <xen/platform_pci.h>
 #include <xen/grant_table.h>
 
 #include <xen/interface/io/netif.h>
 #include <xen/interface/memory.h>
 #include <xen/interface/grant_table.h>
 
 /* Module parameters */
 #define MAX_QUEUES_DEFAULT 8
 static unsigned int xennet_max_queues;
 module_param_named(max_queues, xennet_max_queues, uint, 0644);
 MODULE_PARM_DESC(max_queues,
          "Maximum number of queues per virtual interface");
 
 static bool __read_mostly xennet_trusted = true;
 module_param_named(trusted, xennet_trusted, bool, 0644);
 MODULE_PARM_DESC(trusted, "Is the backend trusted");
 
 #define XENNET_TIMEOUT  (5 * HZ)
 
 static const struct ethtool_ops xennet_ethtool_ops;
 
 struct netfront_cb {
     int pull_to;
 };
 
 #define NETFRONT_SKB_CB(skb)    ((struct netfront_cb *)((skb)->cb))
 
 #define RX_COPY_THRESHOLD 256
 
 #define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, XEN_PAGE_SIZE)
 #define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, XEN_PAGE_SIZE)
 
 /* Minimum number of Rx slots (includes slot for GSO metadata). */
 #define NET_RX_SLOTS_MIN (XEN_NETIF_NR_SLOTS_MIN + 1)
 
 /* Queue name is interface name with "-qNNN" appended */
 #define QUEUE_NAME_SIZE (IFNAMSIZ + 6)
 
 /* IRQ name is queue name with "-tx" or "-rx" appended */
 #define IRQ_NAME_SIZE (QUEUE_NAME_SIZE + 3)
 
 static DECLARE_WAIT_QUEUE_HEAD(module_wq);
 
 struct netfront_stats {
     u64         packets;
     u64         bytes;
     struct u64_stats_sync   syncp;
 };
 
 struct netfront_info;
 
 struct netfront_queue {
     unsigned int id; /* Queue ID, 0-based */
     char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
     struct netfront_info *info;
 
     struct bpf_prog __rcu *xdp_prog;
 
     struct napi_struct napi;
 
     /* Split event channels support, tx_* == rx_* when using
      * single event channel.
      */
     unsigned int tx_evtchn, rx_evtchn;
     unsigned int tx_irq, rx_irq;
     /* Only used when split event channels support is enabled */
     char tx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-tx */
     char rx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-rx */
 
     spinlock_t   tx_lock;
     struct xen_netif_tx_front_ring tx;
     int tx_ring_ref;
 
     /*
      * {tx,rx}_skbs store outstanding skbuffs. Free tx_skb entries
      * are linked from tx_skb_freelist through tx_link.
      */
     struct sk_buff *tx_skbs[NET_TX_RING_SIZE];
     unsigned short tx_link[NET_TX_RING_SIZE];
 #define TX_LINK_NONE 0xffff
 #define TX_PENDING   0xfffe
     grant_ref_t gref_tx_head;
     grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];
     struct page *grant_tx_page[NET_TX_RING_SIZE];
     unsigned tx_skb_freelist;
     unsigned int tx_pend_queue;
 
     spinlock_t   rx_lock ____cacheline_aligned_in_smp;
     struct xen_netif_rx_front_ring rx;
     int rx_ring_ref;
 
     struct timer_list rx_refill_timer;
 
     struct sk_buff *rx_skbs[NET_RX_RING_SIZE];
     grant_ref_t gref_rx_head;
     grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];
 
     unsigned int rx_rsp_unconsumed;
     spinlock_t rx_cons_lock;
 
     struct page_pool *page_pool;
     struct xdp_rxq_info xdp_rxq;
 };
 
 struct netfront_info {
     struct list_head list;
     struct net_device *netdev;
 
     struct xenbus_device *xbdev;
 
     /* Multi-queue support */
     struct netfront_queue *queues;
 
     /* Statistics */
     struct netfront_stats __percpu *rx_stats;
     struct netfront_stats __percpu *tx_stats;
 
     /* XDP state */
     bool netback_has_xdp_headroom;
     bool netfront_xdp_enabled;
 
     /* Is device behaving sane? */
     bool broken;
 
     /* Should skbs be bounced into a zeroed buffer? */
     bool bounce;
 
     atomic_t rx_gso_checksum_fixup;
 };
 
 struct netfront_rx_info {
     struct xen_netif_rx_response rx;
     struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
 };
 
 /*
  * Access macros for acquiring freeing slots in tx_skbs[].
  */
 
 static void add_id_to_list(unsigned *head, unsigned short *list,
                unsigned short id)
 {
     list[id] = *head;
     *head = id;
 }
 
 static unsigned short get_id_from_list(unsigned *head, unsigned short *list)
 {
     unsigned int id = *head;
 
     if (id != TX_LINK_NONE) {
         *head = list[id];
         list[id] = TX_LINK_NONE;
     }
     return id;
 }
 
 static int xennet_rxidx(RING_IDX idx)
 {
     return idx & (NET_RX_RING_SIZE - 1);
 }
 
 static struct sk_buff *xennet_get_rx_skb(struct netfront_queue *queue,
                      RING_IDX ri)
 {
     int i = xennet_rxidx(ri);
     struct sk_buff *skb = queue->rx_skbs[i];
     queue->rx_skbs[i] = NULL;
     return skb;
 }
 
 static grant_ref_t xennet_get_rx_ref(struct netfront_queue *queue,
                         RING_IDX ri)
 {
     int i = xennet_rxidx(ri);
     grant_ref_t ref = queue->grant_rx_ref[i];
     queue->grant_rx_ref[i] = INVALID_GRANT_REF;
     return ref;
 }
 
 #ifdef CONFIG_SYSFS
 static const struct attribute_group xennet_dev_group;
 #endif
 
 static bool xennet_can_sg(struct net_device *dev)
 {
     return dev->features & NETIF_F_SG;
 }
 
 
 static void rx_refill_timeout(struct timer_list *t)
 {
     struct netfront_queue *queue = from_timer(queue, t, rx_refill_timer);
     napi_schedule(&queue->napi);
 }
 
 static int netfront_tx_slot_available(struct netfront_queue *queue)
 {
     return (queue->tx.req_prod_pvt - queue->tx.rsp_cons) <
         (NET_TX_RING_SIZE - XEN_NETIF_NR_SLOTS_MIN - 1);
 }
 
 static void xennet_maybe_wake_tx(struct netfront_queue *queue)
 {
     struct net_device *dev = queue->info->netdev;
     struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, queue->id);
 
     if (unlikely(netif_tx_queue_stopped(dev_queue)) &&
         netfront_tx_slot_available(queue) &&
         likely(netif_running(dev)))
         netif_tx_wake_queue(netdev_get_tx_queue(dev, queue->id));
 }
 
 
 static struct sk_buff *xennet_alloc_one_rx_buffer(struct netfront_queue *queue)
 {
     struct sk_buff *skb;
     struct page *page;
 
     skb = __netdev_alloc_skb(queue->info->netdev,
                  RX_COPY_THRESHOLD + NET_IP_ALIGN,
                  GFP_ATOMIC | __GFP_NOWARN);
     if (unlikely(!skb))
         return NULL;
 
     page = page_pool_alloc_pages(queue->page_pool,
                      GFP_ATOMIC | __GFP_NOWARN | __GFP_ZERO);
     if (unlikely(!page)) {
         kfree_skb(skb);
         return NULL;
     }
     skb_add_rx_frag(skb, 0, page, 0, 0, PAGE_SIZE);
 
     /* Align ip header to a 16 bytes boundary */
     skb_reserve(skb, NET_IP_ALIGN);
     skb->dev = queue->info->netdev;
 
     return skb;
 }
 
 
 static void xennet_alloc_rx_buffers(struct netfront_queue *queue)
 {
     RING_IDX req_prod = queue->rx.req_prod_pvt;
     int notify;
     int err = 0;
 
     if (unlikely(!netif_carrier_ok(queue->info->netdev)))
         return;
 
     for (req_prod = queue->rx.req_prod_pvt;
          req_prod - queue->rx.rsp_cons < NET_RX_RING_SIZE;
          req_prod++) {
         struct sk_buff *skb;
         unsigned short id;
         grant_ref_t ref;
         struct page *page;
         struct xen_netif_rx_request *req;
 
         skb = xennet_alloc_one_rx_buffer(queue);
         if (!skb) {
             err = -ENOMEM;
             break;
         }
 
         id = xennet_rxidx(req_prod);
 
         BUG_ON(queue->rx_skbs[id]);
         queue->rx_skbs[id] = skb;
 
         ref = gnttab_claim_grant_reference(&queue->gref_rx_head);
         WARN_ON_ONCE(IS_ERR_VALUE((unsigned long)(int)ref));
         queue->grant_rx_ref[id] = ref;
 
         page = skb_frag_page(&skb_shinfo(skb)->frags[0]);
 
         req = RING_GET_REQUEST(&queue->rx, req_prod);
         gnttab_page_grant_foreign_access_ref_one(ref,
                              queue->info->xbdev->otherend_id,
                              page,
                              0);
         req->id = id;
         req->gref = ref;
     }
 
     queue->rx.req_prod_pvt = req_prod;
 
     /* Try again later if there are not enough requests or skb allocation
      * failed.
      * Enough requests is quantified as the sum of newly created slots and
      * the unconsumed slots at the backend.
      */
     if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN ||
         unlikely(err)) {
         mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10));
         return;
     }
 
     RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->rx, notify);
     if (notify)
         notify_remote_via_irq(queue->rx_irq);
 }
 
 static int xennet_open(struct net_device *dev)
 {
     struct netfront_info *np = netdev_priv(dev);
     unsigned int num_queues = dev->real_num_tx_queues;
     unsigned int i = 0;
     struct netfront_queue *queue = NULL;
 
     if (!np->queues || np->broken)
         return -ENODEV;
 
     for (i = 0; i < num_queues; ++i) {
         queue = &np->queues[i];
         napi_enable(&queue->napi);
 
         spin_lock_bh(&queue->rx_lock);
         if (netif_carrier_ok(dev)) {
             xennet_alloc_rx_buffers(queue);
             queue->rx.sring->rsp_event = queue->rx.rsp_cons + 1;
             if (RING_HAS_UNCONSUMED_RESPONSES(&queue->rx))
                 napi_schedule(&queue->napi);
         }
         spin_unlock_bh(&queue->rx_lock);
     }
 
     netif_tx_start_all_queues(dev);
 
     return 0;
 }
 
 static bool xennet_tx_buf_gc(struct netfront_queue *queue)
 {
     RING_IDX cons, prod;
     unsigned short id;
     struct sk_buff *skb;
     bool more_to_do;
     bool work_done = false;
     const struct device *dev = &queue->info->netdev->dev;
 
     BUG_ON(!netif_carrier_ok(queue->info->netdev));
 
     do {
         prod = queue->tx.sring->rsp_prod;
         if (RING_RESPONSE_PROD_OVERFLOW(&queue->tx, prod)) {
             dev_alert(dev, "Illegal number of responses %u\n",
                   prod - queue->tx.rsp_cons);
             goto err;
         }
         rmb(); /* Ensure we see responses up to 'rp'. */
 
         for (cons = queue->tx.rsp_cons; cons != prod; cons++) {
             struct xen_netif_tx_response txrsp;
 
             work_done = true;
 
             RING_COPY_RESPONSE(&queue->tx, cons, &txrsp);
             if (txrsp.status == XEN_NETIF_RSP_NULL)
                 continue;
 
             id = txrsp.id;
             if (id >= RING_SIZE(&queue->tx)) {
                 dev_alert(dev,
                       "Response has incorrect id (%u)\n",
                       id);
                 goto err;
             }
             if (queue->tx_link[id] != TX_PENDING) {
                 dev_alert(dev,
                       "Response for inactive request\n");
                 goto err;
             }
 
             queue->tx_link[id] = TX_LINK_NONE;
             skb = queue->tx_skbs[id];
             queue->tx_skbs[id] = NULL;
             if (unlikely(!gnttab_end_foreign_access_ref(
                 queue->grant_tx_ref[id]))) {
                 dev_alert(dev,
                       "Grant still in use by backend domain\n");
                 goto err;
             }
             gnttab_release_grant_reference(
                 &queue->gref_tx_head, queue->grant_tx_ref[id]);
             queue->grant_tx_ref[id] = INVALID_GRANT_REF;
             queue->grant_tx_page[id] = NULL;
             add_id_to_list(&queue->tx_skb_freelist, queue->tx_link, id);
             dev_kfree_skb_irq(skb);
         }
 
         queue->tx.rsp_cons = prod;
 
         RING_FINAL_CHECK_FOR_RESPONSES(&queue->tx, more_to_do);
     } while (more_to_do);
 
     xennet_maybe_wake_tx(queue);
 
     return work_done;
 
  err:
     queue->info->broken = true;
     dev_alert(dev, "Disabled for further use\n");
 
     return work_done;
 }
 
 struct xennet_gnttab_make_txreq {
     struct netfront_queue *queue;
     struct sk_buff *skb;
     struct page *page;
     struct xen_netif_tx_request *tx;      /* Last request on ring page */
     struct xen_netif_tx_request tx_local; /* Last request local copy*/
     unsigned int size;
 };
 
 static void xennet_tx_setup_grant(unsigned long gfn, unsigned int offset,
                   unsigned int len, void *data)
 {
     struct xennet_gnttab_make_txreq *info = data;
     unsigned int id;
     struct xen_netif_tx_request *tx;
     grant_ref_t ref;
     /* convenient aliases */
     struct page *page = info->page;
     struct netfront_queue *queue = info->queue;
     struct sk_buff *skb = info->skb;
 
     id = get_id_from_list(&queue->tx_skb_freelist, queue->tx_link);
     tx = RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
     ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
     WARN_ON_ONCE(IS_ERR_VALUE((unsigned long)(int)ref));
 
     gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
                     gfn, GNTMAP_readonly);
 
     queue->tx_skbs[id] = skb;
     queue->grant_tx_page[id] = page;
     queue->grant_tx_ref[id] = ref;
 
     info->tx_local.id = id;
     info->tx_local.gref = ref;
     info->tx_local.offset = offset;
     info->tx_local.size = len;
     info->tx_local.flags = 0;
 
     *tx = info->tx_local;
 
     /*
      * Put the request in the pending queue, it will be set to be pending
      * when the producer index is about to be raised.
      */
     add_id_to_list(&queue->tx_pend_queue, queue->tx_link, id);
 
     info->tx = tx;
     info->size += info->tx_local.size;
 }
 
 static struct xen_netif_tx_request *xennet_make_first_txreq(
     struct xennet_gnttab_make_txreq *info,
     unsigned int offset, unsigned int len)
 {
     info->size = 0;
 
     gnttab_for_one_grant(info->page, offset, len, xennet_tx_setup_grant, info);
 
     return info->tx;
 }
 
 static void xennet_make_one_txreq(unsigned long gfn, unsigned int offset,
                   unsigned int len, void *data)
 {
     struct xennet_gnttab_make_txreq *info = data;
 
     info->tx->flags |= XEN_NETTXF_more_data;
     skb_get(info->skb);
     xennet_tx_setup_grant(gfn, offset, len, data);
 }
 
 static void xennet_make_txreqs(
     struct xennet_gnttab_make_txreq *info,
     struct page *page,
     unsigned int offset, unsigned int len)
 {
     /* Skip unused frames from start of page */
     page += offset >> PAGE_SHIFT;
     offset &= ~PAGE_MASK;
 
     while (len) {
         info->page = page;
         info->size = 0;
 
         gnttab_foreach_grant_in_range(page, offset, len,
                           xennet_make_one_txreq,
                           info);
 
         page++;
         offset = 0;
         len -= info->size;
     }
 }
 
 /*
  * Count how many ring slots are required to send this skb. Each frag
  * might be a compound page.
  */
 static int xennet_count_skb_slots(struct sk_buff *skb)
 {
     int i, frags = skb_shinfo(skb)->nr_frags;
     int slots;
 
     slots = gnttab_count_grant(offset_in_page(skb->data),
                    skb_headlen(skb));
 
     for (i = 0; i < frags; i++) {
         skb_frag_t *frag = skb_shinfo(skb)->frags + i;
         unsigned long size = skb_frag_size(frag);
         unsigned long offset = skb_frag_off(frag);
 
         /* Skip unused frames from start of page */
         offset &= ~PAGE_MASK;
 
         slots += gnttab_count_grant(offset, size);
     }
 
     return slots;
 }
 
 static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
                    struct net_device *sb_dev)
 {
     unsigned int num_queues = dev->real_num_tx_queues;
     u32 hash;
     u16 queue_idx;
 
     /* First, check if there is only one queue */
     if (num_queues == 1) {
         queue_idx = 0;
     } else {
         hash = skb_get_hash(skb);
         queue_idx = hash % num_queues;
     }
 
     return queue_idx;
 }
 
 static void xennet_mark_tx_pending(struct netfront_queue *queue)
 {
     unsigned int i;
 
     while ((i = get_id_from_list(&queue->tx_pend_queue, queue->tx_link)) !=
            TX_LINK_NONE)
         queue->tx_link[i] = TX_PENDING;
 }
 
 static int xennet_xdp_xmit_one(struct net_device *dev,
                    struct netfront_queue *queue,
                    struct xdp_frame *xdpf)
 {
     struct netfront_info *np = netdev_priv(dev);
     struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);
     struct xennet_gnttab_make_txreq info = {
         .queue = queue,
         .skb = NULL,
         .page = virt_to_page(xdpf->data),
     };
     int notify;
 
     xennet_make_first_txreq(&info,
                 offset_in_page(xdpf->data),
                 xdpf->len);
 
     xennet_mark_tx_pending(queue);
 
     RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
     if (notify)
         notify_remote_via_irq(queue->tx_irq);
 
     u64_stats_update_begin(&tx_stats->syncp);
     tx_stats->bytes += xdpf->len;
     tx_stats->packets++;
     u64_stats_update_end(&tx_stats->syncp);
 
     xennet_tx_buf_gc(queue);
 
     return 0;
 }
 
 static int xennet_xdp_xmit(struct net_device *dev, int n,
                struct xdp_frame **frames, u32 flags)
 {
     unsigned int num_queues = dev->real_num_tx_queues;
     struct netfront_info *np = netdev_priv(dev);
     struct netfront_queue *queue = NULL;
     unsigned long irq_flags;
     int nxmit = 0;
     int i;
 
     if (unlikely(np->broken))
         return -ENODEV;
     if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
         return -EINVAL;
 
     queue = &np->queues[smp_processor_id() % num_queues];
 
     spin_lock_irqsave(&queue->tx_lock, irq_flags);
     for (i = 0; i < n; i++) {
         struct xdp_frame *xdpf = frames[i];
 
         if (!xdpf)
             continue;
         if (xennet_xdp_xmit_one(dev, queue, xdpf))
             break;
         nxmit++;
     }
     spin_unlock_irqrestore(&queue->tx_lock, irq_flags);
 
     return nxmit;
 }
 
 struct sk_buff *bounce_skb(const struct sk_buff *skb)
 {
     unsigned int headerlen = skb_headroom(skb);
     /* Align size to allocate full pages and avoid contiguous data leaks */
     unsigned int size = ALIGN(skb_end_offset(skb) + skb->data_len,
                   XEN_PAGE_SIZE);
     struct sk_buff *n = alloc_skb(size, GFP_ATOMIC | __GFP_ZERO);
 
     if (!n)
         return NULL;
 
     if (!IS_ALIGNED((uintptr_t)n->head, XEN_PAGE_SIZE)) {
         WARN_ONCE(1, "misaligned skb allocated\n");
         kfree_skb(n);
         return NULL;
     }
 
     /* Set the data pointer */
     skb_reserve(n, headerlen);
     /* Set the tail pointer and length */
     skb_put(n, skb->len);
 
     BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len));
 
     skb_copy_header(n, skb);
     return n;
 }
 
 #define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)
 
 static netdev_tx_t xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
     struct netfront_info *np = netdev_priv(dev);
     struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);
     struct xen_netif_tx_request *first_tx;
     unsigned int i;
     int notify;
     int slots;
     struct page *page;
     unsigned int offset;
     unsigned int len;
     unsigned long flags;
     struct netfront_queue *queue = NULL;
     struct xennet_gnttab_make_txreq info = { };
     unsigned int num_queues = dev->real_num_tx_queues;
     u16 queue_index;
     struct sk_buff *nskb;
 
     /* Drop the packet if no queues are set up */
     if (num_queues < 1)
         goto drop;
     if (unlikely(np->broken))
         goto drop;
     /* Determine which queue to transmit this SKB on */
     queue_index = skb_get_queue_mapping(skb);
     queue = &np->queues[queue_index];
 
     /* If skb->len is too big for wire format, drop skb and alert
      * user about misconfiguration.
      */
     if (unlikely(skb->len > XEN_NETIF_MAX_TX_SIZE)) {
         net_alert_ratelimited(
             "xennet: skb->len = %u, too big for wire format\n",
             skb->len);
         goto drop;
     }
 
     slots = xennet_count_skb_slots(skb);
     if (unlikely(slots > MAX_XEN_SKB_FRAGS + 1)) {
         net_dbg_ratelimited("xennet: skb rides the rocket: %d slots, %d bytes\n",
                     slots, skb->len);
         if (skb_linearize(skb))
             goto drop;
     }
 
     page = virt_to_page(skb->data);
     offset = offset_in_page(skb->data);
 
     /* The first req should be at least ETH_HLEN size or the packet will be
      * dropped by netback.
      *
      * If the backend is not trusted bounce all data to zeroed pages to
      * avoid exposing contiguous data on the granted page not belonging to
      * the skb.
      */
     if (np->bounce || unlikely(PAGE_SIZE - offset < ETH_HLEN)) {
         nskb = bounce_skb(skb);
         if (!nskb)
             goto drop;
         dev_consume_skb_any(skb);
         skb = nskb;
         page = virt_to_page(skb->data);
         offset = offset_in_page(skb->data);
     }
 
     len = skb_headlen(skb);
 
     spin_lock_irqsave(&queue->tx_lock, flags);
 
     if (unlikely(!netif_carrier_ok(dev) ||
              (slots > 1 && !xennet_can_sg(dev)) ||
              netif_needs_gso(skb, netif_skb_features(skb)))) {
         spin_unlock_irqrestore(&queue->tx_lock, flags);
         goto drop;
     }
 
     /* First request for the linear area. */
     info.queue = queue;
     info.skb = skb;
     info.page = page;
     first_tx = xennet_make_first_txreq(&info, offset, len);
     offset += info.tx_local.size;
     if (offset == PAGE_SIZE) {
         page++;
         offset = 0;
     }
     len -= info.tx_local.size;
 
     if (skb->ip_summed == CHECKSUM_PARTIAL)
         /* local packet? */
         first_tx->flags |= XEN_NETTXF_csum_blank |
                    XEN_NETTXF_data_validated;
     else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
         /* remote but checksummed. */
         first_tx->flags |= XEN_NETTXF_data_validated;
 
     /* Optional extra info after the first request. */
     if (skb_shinfo(skb)->gso_size) {
         struct xen_netif_extra_info *gso;
 
         gso = (struct xen_netif_extra_info *)
             RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
 
         first_tx->flags |= XEN_NETTXF_extra_info;
 
         gso->u.gso.size = skb_shinfo(skb)->gso_size;
         gso->u.gso.type = (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) ?
             XEN_NETIF_GSO_TYPE_TCPV6 :
             XEN_NETIF_GSO_TYPE_TCPV4;
         gso->u.gso.pad = 0;
         gso->u.gso.features = 0;
 
         gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
         gso->flags = 0;
     }
 
     /* Requests for the rest of the linear area. */
     xennet_make_txreqs(&info, page, offset, len);
 
     /* Requests for all the frags. */
     for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
         xennet_make_txreqs(&info, skb_frag_page(frag),
                     skb_frag_off(frag),
                     skb_frag_size(frag));
     }
 
     /* First request has the packet length. */
     first_tx->size = skb->len;
 
     /* timestamp packet in software */
     skb_tx_timestamp(skb);
 
     xennet_mark_tx_pending(queue);
 
     RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
     if (notify)
         notify_remote_via_irq(queue->tx_irq);
 
     u64_stats_update_begin(&tx_stats->syncp);
     tx_stats->bytes += skb->len;
     tx_stats->packets++;
     u64_stats_update_end(&tx_stats->syncp);
 
     /* Note: It is not safe to access skb after xennet_tx_buf_gc()! */
     xennet_tx_buf_gc(queue);
 
     if (!netfront_tx_slot_available(queue))
         netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
 
     spin_unlock_irqrestore(&queue->tx_lock, flags);
 
     return NETDEV_TX_OK;
 
  drop:
     dev->stats.tx_dropped++;
     dev_kfree_skb_any(skb);
     return NETDEV_TX_OK;
 }
 
 static int xennet_close(struct net_device *dev)
 {
     struct netfront_info *np = netdev_priv(dev);
     unsigned int num_queues = dev->real_num_tx_queues;
     unsigned int i;
     struct netfront_queue *queue;
     netif_tx_stop_all_queues(np->netdev);
     for (i = 0; i < num_queues; ++i) {
         queue = &np->queues[i];
         napi_disable(&queue->napi);
     }
     return 0;
 }
 
 static void xennet_destroy_queues(struct netfront_info *info)
 {
     unsigned int i;
 
     for (i = 0; i < info->netdev->real_num_tx_queues; i++) {
         struct netfront_queue *queue = &info->queues[i];
 
         if (netif_running(info->netdev))
             napi_disable(&queue->napi);
         netif_napi_del(&queue->napi);
     }
 
     kfree(info->queues);
     info->queues = NULL;
 }
 
 static void xennet_uninit(struct net_device *dev)
 {
     struct netfront_info *np = netdev_priv(dev);
     xennet_destroy_queues(np);
 }
 
 static void xennet_set_rx_rsp_cons(struct netfront_queue *queue, RING_IDX val)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&queue->rx_cons_lock, flags);
     queue->rx.rsp_cons = val;
     queue->rx_rsp_unconsumed = XEN_RING_NR_UNCONSUMED_RESPONSES(&queue->rx);
     spin_unlock_irqrestore(&queue->rx_cons_lock, flags);
 }
 
 static void xennet_move_rx_slot(struct netfront_queue *queue, struct sk_buff *skb,
                 grant_ref_t ref)
 {
     int new = xennet_rxidx(queue->rx.req_prod_pvt);
 
     BUG_ON(queue->rx_skbs[new]);
     queue->rx_skbs[new] = skb;
     queue->grant_rx_ref[new] = ref;
     RING_GET_REQUEST(&queue->rx, queue->rx.req_prod_pvt)->id = new;
     RING_GET_REQUEST(&queue->rx, queue->rx.req_prod_pvt)->gref = ref;
     queue->rx.req_prod_pvt++;
 }
 
 static int xennet_get_extras(struct netfront_queue *queue,
                  struct xen_netif_extra_info *extras,
                  RING_IDX rp)
 
 {
     struct xen_netif_extra_info extra;
     struct device *dev = &queue->info->netdev->dev;
     RING_IDX cons = queue->rx.rsp_cons;
     int err = 0;
 
     do {
         struct sk_buff *skb;
         grant_ref_t ref;
 
         if (unlikely(cons + 1 == rp)) {
             if (net_ratelimit())
                 dev_warn(dev, "Missing extra info\n");
             err = -EBADR;
             break;
         }
 
         RING_COPY_RESPONSE(&queue->rx, ++cons, &extra);
 
         if (unlikely(!extra.type ||
                  extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
             if (net_ratelimit())
                 dev_warn(dev, "Invalid extra type: %d\n",
                      extra.type);
             err = -EINVAL;
         } else {
             extras[extra.type - 1] = extra;
         }
 
         skb = xennet_get_rx_skb(queue, cons);
         ref = xennet_get_rx_ref(queue, cons);
         xennet_move_rx_slot(queue, skb, ref);
     } while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
 
     xennet_set_rx_rsp_cons(queue, cons);
     return err;
 }
 
 static u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
            struct xen_netif_rx_response *rx, struct bpf_prog *prog,
            struct xdp_buff *xdp, bool *need_xdp_flush)
 {
     struct xdp_frame *xdpf;
     u32 len = rx->status;
     u32 act;
     int err;
 
     xdp_init_buff(xdp, XEN_PAGE_SIZE - XDP_PACKET_HEADROOM,
               &queue->xdp_rxq);
     xdp_prepare_buff(xdp, page_address(pdata), XDP_PACKET_HEADROOM,
              len, false);
 
     act = bpf_prog_run_xdp(prog, xdp);
     switch (act) {
     case XDP_TX:
         get_page(pdata);
         xdpf = xdp_convert_buff_to_frame(xdp);
         err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0);
         if (unlikely(!err))
             xdp_return_frame_rx_napi(xdpf);
         else if (unlikely(err < 0))
             trace_xdp_exception(queue->info->netdev, prog, act);
         break;
     case XDP_REDIRECT:
         get_page(pdata);
         err = xdp_do_redirect(queue->info->netdev, xdp, prog);
         *need_xdp_flush = true;
         if (unlikely(err))
             trace_xdp_exception(queue->info->netdev, prog, act);
         break;
     case XDP_PASS:
     case XDP_DROP:
         break;
 
     case XDP_ABORTED:
         trace_xdp_exception(queue->info->netdev, prog, act);
         break;
 
     default:
         bpf_warn_invalid_xdp_action(queue->info->netdev, prog, act);
     }
 
     return act;
 }
 
 static int xennet_get_responses(struct netfront_queue *queue,
                 struct netfront_rx_info *rinfo, RING_IDX rp,
                 struct sk_buff_head *list,
                 bool *need_xdp_flush)
 {
     struct xen_netif_rx_response *rx = &rinfo->rx, rx_local;
     int max = XEN_NETIF_NR_SLOTS_MIN + (rx->status <= RX_COPY_THRESHOLD);
     RING_IDX cons = queue->rx.rsp_cons;
     struct sk_buff *skb = xennet_get_rx_skb(queue, cons);
     struct xen_netif_extra_info *extras = rinfo->extras;
     grant_ref_t ref = xennet_get_rx_ref(queue, cons);
     struct device *dev = &queue->info->netdev->dev;
     struct bpf_prog *xdp_prog;
     struct xdp_buff xdp;
     int slots = 1;
     int err = 0;
     u32 verdict;
 
     if (rx->flags & XEN_NETRXF_extra_info) {
         err = xennet_get_extras(queue, extras, rp);
         if (!err) {
             if (extras[XEN_NETIF_EXTRA_TYPE_XDP - 1].type) {
                 struct xen_netif_extra_info *xdp;
 
                 xdp = &extras[XEN_NETIF_EXTRA_TYPE_XDP - 1];
                 rx->offset = xdp->u.xdp.headroom;
             }
         }
         cons = queue->rx.rsp_cons;
     }
 
     for (;;) {
         /*
          * This definitely indicates a bug, either in this driver or in
          * the backend driver. In future this should flag the bad
          * situation to the system controller to reboot the backend.
          */
         if (ref == INVALID_GRANT_REF) {
             if (net_ratelimit())
                 dev_warn(dev, "Bad rx response id %d.\n",
                      rx->id);
             err = -EINVAL;
             goto next;
         }
 
         if (unlikely(rx->status < 0 ||
                  rx->offset + rx->status > XEN_PAGE_SIZE)) {
             if (net_ratelimit())
                 dev_warn(dev, "rx->offset: %u, size: %d\n",
                      rx->offset, rx->status);
             xennet_move_rx_slot(queue, skb, ref);
             err = -EINVAL;
             goto next;
         }
 
         if (!gnttab_end_foreign_access_ref(ref)) {
             dev_alert(dev,
                   "Grant still in use by backend domain\n");
             queue->info->broken = true;
             dev_alert(dev, "Disabled for further use\n");
             return -EINVAL;
         }
 
         gnttab_release_grant_reference(&queue->gref_rx_head, ref);
 
         rcu_read_lock();
         xdp_prog = rcu_dereference(queue->xdp_prog);
         if (xdp_prog) {
             if (!(rx->flags & XEN_NETRXF_more_data)) {
                 /* currently only a single page contains data */
                 verdict = xennet_run_xdp(queue,
                              skb_frag_page(&skb_shinfo(skb)->frags[0]),
                              rx, xdp_prog, &xdp, need_xdp_flush);
                 if (verdict != XDP_PASS)
                     err = -EINVAL;
             } else {
                 /* drop the frame */
                 err = -EINVAL;
             }
         }
         rcu_read_unlock();
 
         __skb_queue_tail(list, skb);
 
 next:
         if (!(rx->flags & XEN_NETRXF_more_data))
             break;
 
         if (cons + slots == rp) {
             if (net_ratelimit())
                 dev_warn(dev, "Need more slots\n");
             err = -ENOENT;
             break;
         }
 
         RING_COPY_RESPONSE(&queue->rx, cons + slots, &rx_local);
         rx = &rx_local;
         skb = xennet_get_rx_skb(queue, cons + slots);
         ref = xennet_get_rx_ref(queue, cons + slots);
         slots++;
     }
 
     if (unlikely(slots > max)) {
         if (net_ratelimit())
             dev_warn(dev, "Too many slots\n");
         err = -E2BIG;
     }
 
     if (unlikely(err))
         xennet_set_rx_rsp_cons(queue, cons + slots);
 
     return err;
 }
 
 static int xennet_set_skb_gso(struct sk_buff *skb,
                   struct xen_netif_extra_info *gso)
 {
     if (!gso->u.gso.size) {
         if (net_ratelimit())
             pr_warn("GSO size must not be zero\n");
         return -EINVAL;
     }
 
     if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4 &&
         gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV6) {
         if (net_ratelimit())
             pr_warn("Bad GSO type %d\n", gso->u.gso.type);
         return -EINVAL;
     }
 
     skb_shinfo(skb)->gso_size = gso->u.gso.size;
     skb_shinfo(skb)->gso_type =
         (gso->u.gso.type == XEN_NETIF_GSO_TYPE_TCPV4) ?
         SKB_GSO_TCPV4 :
         SKB_GSO_TCPV6;
 
     /* Header must be checked, and gso_segs computed. */
     skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
     skb_shinfo(skb)->gso_segs = 0;
 
     return 0;
 }
 
 static int xennet_fill_frags(struct netfront_queue *queue,
                  struct sk_buff *skb,
                  struct sk_buff_head *list)
 {
     RING_IDX cons = queue->rx.rsp_cons;
     struct sk_buff *nskb;
 
     while ((nskb = __skb_dequeue(list))) {
         struct xen_netif_rx_response rx;
         skb_frag_t *nfrag = &skb_shinfo(nskb)->frags[0];
 
         RING_COPY_RESPONSE(&queue->rx, ++cons, &rx);
 
         if (skb_shinfo(skb)->nr_frags == MAX_SKB_FRAGS) {
             unsigned int pull_to = NETFRONT_SKB_CB(skb)->pull_to;
 
             BUG_ON(pull_to < skb_headlen(skb));
             __pskb_pull_tail(skb, pull_to - skb_headlen(skb));
         }
         if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) {
             xennet_set_rx_rsp_cons(queue,
                            ++cons + skb_queue_len(list));
             kfree_skb(nskb);
             return -ENOENT;
         }
 
         skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
                 skb_frag_page(nfrag),
                 rx.offset, rx.status, PAGE_SIZE);
 
         skb_shinfo(nskb)->nr_frags = 0;
         kfree_skb(nskb);
     }
 
     xennet_set_rx_rsp_cons(queue, cons);
 
     return 0;
 }
 
 static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
 {
     bool recalculate_partial_csum = false;
 
     /*
      * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
      * peers can fail to set NETRXF_csum_blank when sending a GSO
      * frame. In this case force the SKB to CHECKSUM_PARTIAL and
      * recalculate the partial checksum.
      */
     if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) {
         struct netfront_info *np = netdev_priv(dev);
         atomic_inc(&np->rx_gso_checksum_fixup);
         skb->ip_summed = CHECKSUM_PARTIAL;
         recalculate_partial_csum = true;
     }
 
     /* A non-CHECKSUM_PARTIAL SKB does not require setup. */
     if (skb->ip_summed != CHECKSUM_PARTIAL)
         return 0;
 
     return skb_checksum_setup(skb, recalculate_partial_csum);
 }
 
 static int handle_incoming_queue(struct netfront_queue *queue,
                  struct sk_buff_head *rxq)
 {
     struct netfront_stats *rx_stats = this_cpu_ptr(queue->info->rx_stats);
     int packets_dropped = 0;
     struct sk_buff *skb;
 
     while ((skb = __skb_dequeue(rxq)) != NULL) {
         int pull_to = NETFRONT_SKB_CB(skb)->pull_to;
 
         if (pull_to > skb_headlen(skb))
             __pskb_pull_tail(skb, pull_to - skb_headlen(skb));
 
         /* Ethernet work: Delayed to here as it peeks the header. */
         skb->protocol = eth_type_trans(skb, queue->info->netdev);
         skb_reset_network_header(skb);
 
         if (checksum_setup(queue->info->netdev, skb)) {
             kfree_skb(skb);
             packets_dropped++;
             queue->info->netdev->stats.rx_errors++;
             continue;
         }
 
         u64_stats_update_begin(&rx_stats->syncp);
         rx_stats->packets++;
         rx_stats->bytes += skb->len;
         u64_stats_update_end(&rx_stats->syncp);
 
         /* Pass it up. */
         napi_gro_receive(&queue->napi, skb);
     }
 
     return packets_dropped;
 }
 
 static int xennet_poll(struct napi_struct *napi, int budget)
 {
     struct netfront_queue *queue = container_of(napi, struct netfront_queue, napi);
     struct net_device *dev = queue->info->netdev;
     struct sk_buff *skb;
     struct netfront_rx_info rinfo;
     struct xen_netif_rx_response *rx = &rinfo.rx;
     struct xen_netif_extra_info *extras = rinfo.extras;
     RING_IDX i, rp;
     int work_done;
     struct sk_buff_head rxq;
     struct sk_buff_head errq;
     struct sk_buff_head tmpq;
     int err;
     bool need_xdp_flush = false;
 
     spin_lock(&queue->rx_lock);
 
     skb_queue_head_init(&rxq);
     skb_queue_head_init(&errq);
     skb_queue_head_init(&tmpq);
 
     rp = queue->rx.sring->rsp_prod;
     if (RING_RESPONSE_PROD_OVERFLOW(&queue->rx, rp)) {
         dev_alert(&dev->dev, "Illegal number of responses %u\n",
               rp - queue->rx.rsp_cons);
         queue->info->broken = true;
         spin_unlock(&queue->rx_lock);
         return 0;
     }
     rmb(); /* Ensure we see queued responses up to 'rp'. */
 
     i = queue->rx.rsp_cons;
     work_done = 0;
     while ((i != rp) && (work_done < budget)) {
         RING_COPY_RESPONSE(&queue->rx, i, rx);
         memset(extras, 0, sizeof(rinfo.extras));
 
         err = xennet_get_responses(queue, &rinfo, rp, &tmpq,
                        &need_xdp_flush);
 
         if (unlikely(err)) {
             if (queue->info->broken) {
                 spin_unlock(&queue->rx_lock);
                 return 0;
             }
 err:
             while ((skb = __skb_dequeue(&tmpq)))
                 __skb_queue_tail(&errq, skb);
             dev->stats.rx_errors++;
             i = queue->rx.rsp_cons;
             continue;
         }
 
         skb = __skb_dequeue(&tmpq);
 
         if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
             struct xen_netif_extra_info *gso;
             gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
 
             if (unlikely(xennet_set_skb_gso(skb, gso))) {
                 __skb_queue_head(&tmpq, skb);
                 xennet_set_rx_rsp_cons(queue,
                                queue->rx.rsp_cons +
                                skb_queue_len(&tmpq));
                 goto err;
             }
         }
 
         NETFRONT_SKB_CB(skb)->pull_to = rx->status;
         if (NETFRONT_SKB_CB(skb)->pull_to > RX_COPY_THRESHOLD)
             NETFRONT_SKB_CB(skb)->pull_to = RX_COPY_THRESHOLD;
 
         skb_frag_off_set(&skb_shinfo(skb)->frags[0], rx->offset);
         skb_frag_size_set(&skb_shinfo(skb)->frags[0], rx->status);
         skb->data_len = rx->status;
         skb->len += rx->status;
 
         if (unlikely(xennet_fill_frags(queue, skb, &tmpq)))
             goto err;
 
         if (rx->flags & XEN_NETRXF_csum_blank)
             skb->ip_summed = CHECKSUM_PARTIAL;
         else if (rx->flags & XEN_NETRXF_data_validated)
             skb->ip_summed = CHECKSUM_UNNECESSARY;
 
         __skb_queue_tail(&rxq, skb);
 
         i = queue->rx.rsp_cons + 1;
         xennet_set_rx_rsp_cons(queue, i);
         work_done++;
     }
     if (need_xdp_flush)
         xdp_do_flush();
 
     __skb_queue_purge(&errq);
 
     work_done -= handle_incoming_queue(queue, &rxq);
 
     xennet_alloc_rx_buffers(queue);
 
     if (work_done < budget) {
         int more_to_do = 0;
 
         napi_complete_done(napi, work_done);
 
         RING_FINAL_CHECK_FOR_RESPONSES(&queue->rx, more_to_do);
         if (more_to_do)
             napi_schedule(napi);
     }
 
     spin_unlock(&queue->rx_lock);
 
     return work_done;
 }
 
 static int xennet_change_mtu(struct net_device *dev, int mtu)
 {
     int max = xennet_can_sg(dev) ? XEN_NETIF_MAX_TX_SIZE : ETH_DATA_LEN;
 
     if (mtu > max)
         return -EINVAL;
     dev->mtu = mtu;
     return 0;
 }
 
 static void xennet_get_stats64(struct net_device *dev,
                    struct rtnl_link_stats64 *tot)
 {
     struct netfront_info *np = netdev_priv(dev);
     int cpu;
 
     for_each_possible_cpu(cpu) {
         struct netfront_stats *rx_stats = per_cpu_ptr(np->rx_stats, cpu);
         struct netfront_stats *tx_stats = per_cpu_ptr(np->tx_stats, cpu);
         u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
         unsigned int start;
 
         do {
             start = u64_stats_fetch_begin_irq(&tx_stats->syncp);
             tx_packets = tx_stats->packets;
             tx_bytes = tx_stats->bytes;
         } while (u64_stats_fetch_retry_irq(&tx_stats->syncp, start));
 
         do {
             start = u64_stats_fetch_begin_irq(&rx_stats->syncp);
             rx_packets = rx_stats->packets;
             rx_bytes = rx_stats->bytes;
         } while (u64_stats_fetch_retry_irq(&rx_stats->syncp, start));
 
         tot->rx_packets += rx_packets;
         tot->tx_packets += tx_packets;
         tot->rx_bytes   += rx_bytes;
         tot->tx_bytes   += tx_bytes;
     }
 
     tot->rx_errors  = dev->stats.rx_errors;
     tot->tx_dropped = dev->stats.tx_dropped;
 }
 
 static void xennet_release_tx_bufs(struct netfront_queue *queue)
 {
     struct sk_buff *skb;
     int i;
 
     for (i = 0; i < NET_TX_RING_SIZE; i++) {
         /* Skip over entries which are actually freelist references */
         if (!queue->tx_skbs[i])
             continue;
 
         skb = queue->tx_skbs[i];
         queue->tx_skbs[i] = NULL;
         get_page(queue->grant_tx_page[i]);
         gnttab_end_foreign_access(queue->grant_tx_ref[i],
                       queue->grant_tx_page[i]);
         queue->grant_tx_page[i] = NULL;
         queue->grant_tx_ref[i] = INVALID_GRANT_REF;
         add_id_to_list(&queue->tx_skb_freelist, queue->tx_link, i);
         dev_kfree_skb_irq(skb);
     }
 }
 
 static void xennet_release_rx_bufs(struct netfront_queue *queue)
 {
     int id, ref;
 
     spin_lock_bh(&queue->rx_lock);
 
     for (id = 0; id < NET_RX_RING_SIZE; id++) {
         struct sk_buff *skb;
         struct page *page;
 
         skb = queue->rx_skbs[id];
         if (!skb)
             continue;
 
         ref = queue->grant_rx_ref[id];
         if (ref == INVALID_GRANT_REF)
             continue;
 
         page = skb_frag_page(&skb_shinfo(skb)->frags[0]);
 
         /* gnttab_end_foreign_access() needs a page ref until
          * foreign access is ended (which may be deferred).
          */
         get_page(page);
         gnttab_end_foreign_access(ref, page);
         queue->grant_rx_ref[id] = INVALID_GRANT_REF;
 
         kfree_skb(skb);
     }
 
     spin_unlock_bh(&queue->rx_lock);
 }
 
 static netdev_features_t xennet_fix_features(struct net_device *dev,
     netdev_features_t features)
 {
     struct netfront_info *np = netdev_priv(dev);
 
     if (features & NETIF_F_SG &&
         !xenbus_read_unsigned(np->xbdev->otherend, "feature-sg", 0))
         features &= ~NETIF_F_SG;
 
     if (features & NETIF_F_IPV6_CSUM &&
         !xenbus_read_unsigned(np->xbdev->otherend,
                   "feature-ipv6-csum-offload", 0))
         features &= ~NETIF_F_IPV6_CSUM;
 
     if (features & NETIF_F_TSO &&
         !xenbus_read_unsigned(np->xbdev->otherend, "feature-gso-tcpv4", 0))
         features &= ~NETIF_F_TSO;
 
     if (features & NETIF_F_TSO6 &&
         !xenbus_read_unsigned(np->xbdev->otherend, "feature-gso-tcpv6", 0))
         features &= ~NETIF_F_TSO6;
 
     return features;
 }
 
 static int xennet_set_features(struct net_device *dev,
     netdev_features_t features)
 {
     if (!(features & NETIF_F_SG) && dev->mtu > ETH_DATA_LEN) {
         netdev_info(dev, "Reducing MTU because no SG offload");
         dev->mtu = ETH_DATA_LEN;
     }
 
     return 0;
 }
 
 static bool xennet_handle_tx(struct netfront_queue *queue, unsigned int *eoi)
 {
     unsigned long flags;
 
     if (unlikely(queue->info->broken))
         return false;
 
     spin_lock_irqsave(&queue->tx_lock, flags);
     if (xennet_tx_buf_gc(queue))
         *eoi = 0;
     spin_unlock_irqrestore(&queue->tx_lock, flags);
 
     return true;
 }
 
 static irqreturn_t xennet_tx_interrupt(int irq, void *dev_id)
 {
     unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS;
 
     if (likely(xennet_handle_tx(dev_id, &eoiflag)))
         xen_irq_lateeoi(irq, eoiflag);
 
     return IRQ_HANDLED;
 }
 
 static bool xennet_handle_rx(struct netfront_queue *queue, unsigned int *eoi)
 {
     unsigned int work_queued;
     unsigned long flags;
 
     if (unlikely(queue->info->broken))
         return false;
 
     spin_lock_irqsave(&queue->rx_cons_lock, flags);
     work_queued = XEN_RING_NR_UNCONSUMED_RESPONSES(&queue->rx);
     if (work_queued > queue->rx_rsp_unconsumed) {
         queue->rx_rsp_unconsumed = work_queued;
         *eoi = 0;
     } else if (unlikely(work_queued < queue->rx_rsp_unconsumed)) {
         const struct device *dev = &queue->info->netdev->dev;
 
         spin_unlock_irqrestore(&queue->rx_cons_lock, flags);
         dev_alert(dev, "RX producer index going backwards\n");
         dev_alert(dev, "Disabled for further use\n");
         queue->info->broken = true;
         return false;
     }
     spin_unlock_irqrestore(&queue->rx_cons_lock, flags);
 
     if (likely(netif_carrier_ok(queue->info->netdev) && work_queued))
         napi_schedule(&queue->napi);
 
     return true;
 }
 
 static irqreturn_t xennet_rx_interrupt(int irq, void *dev_id)
 {
     unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS;
 
     if (likely(xennet_handle_rx(dev_id, &eoiflag)))
         xen_irq_lateeoi(irq, eoiflag);
 
     return IRQ_HANDLED;
 }
 
 static irqreturn_t xennet_interrupt(int irq, void *dev_id)
 {
     unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS;
 
     if (xennet_handle_tx(dev_id, &eoiflag) &&
         xennet_handle_rx(dev_id, &eoiflag))
         xen_irq_lateeoi(irq, eoiflag);
 
     return IRQ_HANDLED;
 }
 
 #ifdef CONFIG_NET_POLL_CONTROLLER
 static void xennet_poll_controller(struct net_device *dev)
 {
     /* Poll each queue */
     struct netfront_info *info = netdev_priv(dev);
     unsigned int num_queues = dev->real_num_tx_queues;
     unsigned int i;
 
     if (info->broken)
         return;
 
     for (i = 0; i < num_queues; ++i)
         xennet_interrupt(0, &info->queues[i]);
 }
 #endif
 
 #define NETBACK_XDP_HEADROOM_DISABLE    0
 #define NETBACK_XDP_HEADROOM_ENABLE 1
 
 static int talk_to_netback_xdp(struct netfront_info *np, int xdp)
 {
     int err;
     unsigned short headroom;
 
     headroom = xdp ? XDP_PACKET_HEADROOM : 0;
     err = xenbus_printf(XBT_NIL, np->xbdev->nodename,
                 "xdp-headroom", "%hu",
                 headroom);
     if (err)
         pr_warn("Error writing xdp-headroom\n");
 
     return err;
 }
 
 static int xennet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
               struct netlink_ext_ack *extack)
 {
     unsigned long max_mtu = XEN_PAGE_SIZE - XDP_PACKET_HEADROOM;
     struct netfront_info *np = netdev_priv(dev);
     struct bpf_prog *old_prog;
     unsigned int i, err;
 
     if (dev->mtu > max_mtu) {
         netdev_warn(dev, "XDP requires MTU less than %lu\n", max_mtu);
         return -EINVAL;
     }
 
     if (!np->netback_has_xdp_headroom)
         return 0;
 
     xenbus_switch_state(np->xbdev, XenbusStateReconfiguring);
 
     err = talk_to_netback_xdp(np, prog ? NETBACK_XDP_HEADROOM_ENABLE :
                   NETBACK_XDP_HEADROOM_DISABLE);
     if (err)
         return err;
 
     /* avoid the race with XDP headroom adjustment */
     wait_event(module_wq,
            xenbus_read_driver_state(np->xbdev->otherend) ==
            XenbusStateReconfigured);
     np->netfront_xdp_enabled = true;
 
     old_prog = rtnl_dereference(np->queues[0].xdp_prog);
 
     if (prog)
         bpf_prog_add(prog, dev->real_num_tx_queues);
 
     for (i = 0; i < dev->real_num_tx_queues; ++i)
         rcu_assign_pointer(np->queues[i].xdp_prog, prog);
 
     if (old_prog)
         for (i = 0; i < dev->real_num_tx_queues; ++i)
             bpf_prog_put(old_prog);
 
     xenbus_switch_state(np->xbdev, XenbusStateConnected);
 
     return 0;
 }
 
 static int xennet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 {
     struct netfront_info *np = netdev_priv(dev);
 
     if (np->broken)
         return -ENODEV;
 
     switch (xdp->command) {
     case XDP_SETUP_PROG:
         return xennet_xdp_set(dev, xdp->prog, xdp->extack);
     default:
         return -EINVAL;
     }
 }
 
 static const struct net_device_ops xennet_netdev_ops = {
     .ndo_uninit          = xennet_uninit,
     .ndo_open            = xennet_open,
     .ndo_stop            = xennet_close,
     .ndo_start_xmit      = xennet_start_xmit,
     .ndo_change_mtu      = xennet_change_mtu,
     .ndo_get_stats64     = xennet_get_stats64,
     .ndo_set_mac_address = eth_mac_addr,
     .ndo_validate_addr   = eth_validate_addr,
     .ndo_fix_features    = xennet_fix_features,
     .ndo_set_features    = xennet_set_features,
     .ndo_select_queue    = xennet_select_queue,
     .ndo_bpf            = xennet_xdp,
     .ndo_xdp_xmit       = xennet_xdp_xmit,
 #ifdef CONFIG_NET_POLL_CONTROLLER
     .ndo_poll_controller = xennet_poll_controller,
 #endif
 };
 
 static void xennet_free_netdev(struct net_device *netdev)
 {
     struct netfront_info *np = netdev_priv(netdev);
 
     free_percpu(np->rx_stats);
     free_percpu(np->tx_stats);
     free_netdev(netdev);
 }
 
 static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 {
     int err;
     struct net_device *netdev;
     struct netfront_info *np;
 
     netdev = alloc_etherdev_mq(sizeof(struct netfront_info), xennet_max_queues);
     if (!netdev)
         return ERR_PTR(-ENOMEM);
 
     np                   = netdev_priv(netdev);
     np->xbdev            = dev;
 
     np->queues = NULL;
 
     err = -ENOMEM;
     np->rx_stats = netdev_alloc_pcpu_stats(struct netfront_stats);
     if (np->rx_stats == NULL)
         goto exit;
     np->tx_stats = netdev_alloc_pcpu_stats(struct netfront_stats);
     if (np->tx_stats == NULL)
         goto exit;
 
     netdev->netdev_ops  = &xennet_netdev_ops;
 
     netdev->features        = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
                   NETIF_F_GSO_ROBUST;
     netdev->hw_features = NETIF_F_SG |
                   NETIF_F_IPV6_CSUM |
                   NETIF_F_TSO | NETIF_F_TSO6;
 
     /*
          * Assume that all hw features are available for now. This set
          * will be adjusted by the call to netdev_update_features() in
          * xennet_connect() which is the earliest point where we can
          * negotiate with the backend regarding supported features.
          */
     netdev->features |= netdev->hw_features;
 
     netdev->ethtool_ops = &xennet_ethtool_ops;
     netdev->min_mtu = ETH_MIN_MTU;
     netdev->max_mtu = XEN_NETIF_MAX_TX_SIZE;
     SET_NETDEV_DEV(netdev, &dev->dev);
 
     np->netdev = netdev;
     np->netfront_xdp_enabled = false;
 
     netif_carrier_off(netdev);
 
     do {
         xenbus_switch_state(dev, XenbusStateInitialising);
         err = wait_event_timeout(module_wq,
                  xenbus_read_driver_state(dev->otherend) !=
                  XenbusStateClosed &&
                  xenbus_read_driver_state(dev->otherend) !=
                  XenbusStateUnknown, XENNET_TIMEOUT);
     } while (!err);
 
     return netdev;
 
  exit:
     xennet_free_netdev(netdev);
     return ERR_PTR(err);
 }
 
 /*
  * Entry point to this code when a new device is created.  Allocate the basic
  * structures and the ring buffers for communication with the backend, and
  * inform the backend of the appropriate details for those.
  */
 static int netfront_probe(struct xenbus_device *dev,
               const struct xenbus_device_id *id)
 {
     int err;
     struct net_device *netdev;
     struct netfront_info *info;
 
     netdev = xennet_create_dev(dev);
     if (IS_ERR(netdev)) {
         err = PTR_ERR(netdev);
         xenbus_dev_fatal(dev, err, "creating netdev");
         return err;
     }
 
     info = netdev_priv(netdev);
     dev_set_drvdata(&dev->dev, info);
 #ifdef CONFIG_SYSFS
     info->netdev->sysfs_groups[0] = &xennet_dev_group;
 #endif
 
     return 0;
 }
 
 static void xennet_end_access(int ref, void *page)
 {
     /* This frees the page as a side-effect */
     if (ref != INVALID_GRANT_REF)
         gnttab_end_foreign_access(ref, virt_to_page(page));
 }
 
 static void xennet_disconnect_backend(struct netfront_info *info)
 {
     unsigned int i = 0;
     unsigned int num_queues = info->netdev->real_num_tx_queues;
 
     netif_carrier_off(info->netdev);
 
     for (i = 0; i < num_queues && info->queues; ++i) {
         struct netfront_queue *queue = &info->queues[i];
 
         del_timer_sync(&queue->rx_refill_timer);
 
         if (queue->tx_irq && (queue->tx_irq == queue->rx_irq))
             unbind_from_irqhandler(queue->tx_irq, queue);
         if (queue->tx_irq && (queue->tx_irq != queue->rx_irq)) {
             unbind_from_irqhandler(queue->tx_irq, queue);
             unbind_from_irqhandler(queue->rx_irq, queue);
         }
         queue->tx_evtchn = queue->rx_evtchn = 0;
         queue->tx_irq = queue->rx_irq = 0;
 
         if (netif_running(info->netdev))
             napi_synchronize(&queue->napi);
 
         xennet_release_tx_bufs(queue);
         xennet_release_rx_bufs(queue);
         gnttab_free_grant_references(queue->gref_tx_head);
         gnttab_free_grant_references(queue->gref_rx_head);
 
         /* End access and free the pages */
         xennet_end_access(queue->tx_ring_ref, queue->tx.sring);
         xennet_end_access(queue->rx_ring_ref, queue->rx.sring);
 
         queue->tx_ring_ref = INVALID_GRANT_REF;
         queue->rx_ring_ref = INVALID_GRANT_REF;
         queue->tx.sring = NULL;
         queue->rx.sring = NULL;
 
         page_pool_destroy(queue->page_pool);
     }
 }
 
 /*
  * We are reconnecting to the backend, due to a suspend/resume, or a backend
  * driver restart.  We tear down our netif structure and recreate it, but
  * leave the device-layer structures intact so that this is transparent to the
  * rest of the kernel.
  */
 static int netfront_resume(struct xenbus_device *dev)
 {
     struct netfront_info *info = dev_get_drvdata(&dev->dev);
 
     dev_dbg(&dev->dev, "%s\n", dev->nodename);
 
     netif_tx_lock_bh(info->netdev);
     netif_device_detach(info->netdev);
     netif_tx_unlock_bh(info->netdev);
 
     xennet_disconnect_backend(info);
     return 0;
 }
 
 static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
 {
     char *s, *e, *macstr;
     int i;
 
     macstr = s = xenbus_read(XBT_NIL, dev->nodename, "mac", NULL);
     if (IS_ERR(macstr))
         return PTR_ERR(macstr);
 
     for (i = 0; i < ETH_ALEN; i++) {
         mac[i] = simple_strtoul(s, &e, 16);
         if ((s == e) || (*e != ((i == ETH_ALEN-1) ? '\0' : ':'))) {
             kfree(macstr);
             return -ENOENT;
         }
         s = e+1;
     }
 
     kfree(macstr);
     return 0;
 }
 
 static int setup_netfront_single(struct netfront_queue *queue)
 {
     int err;
 
     err = xenbus_alloc_evtchn(queue->info->xbdev, &queue->tx_evtchn);
     if (err < 0)
         goto fail;
 
     err = bind_evtchn_to_irqhandler_lateeoi(queue->tx_evtchn,
                         xennet_interrupt, 0,
                         queue->info->netdev->name,
                         queue);
     if (err < 0)
         goto bind_fail;
     queue->rx_evtchn = queue->tx_evtchn;
     queue->rx_irq = queue->tx_irq = err;
 
     return 0;
 
 bind_fail:
     xenbus_free_evtchn(queue->info->xbdev, queue->tx_evtchn);
     queue->tx_evtchn = 0;
 fail:
     return err;
 }
 
 static int setup_netfront_split(struct netfront_queue *queue)
 {
     int err;
 
     err = xenbus_alloc_evtchn(queue->info->xbdev, &queue->tx_evtchn);
     if (err < 0)
         goto fail;
     err = xenbus_alloc_evtchn(queue->info->xbdev, &queue->rx_evtchn);
     if (err < 0)
         goto alloc_rx_evtchn_fail;
 
     snprintf(queue->tx_irq_name, sizeof(queue->tx_irq_name),
          "%s-tx", queue->name);
     err = bind_evtchn_to_irqhandler_lateeoi(queue->tx_evtchn,
                         xennet_tx_interrupt, 0,
                         queue->tx_irq_name, queue);
     if (err < 0)
         goto bind_tx_fail;
     queue->tx_irq = err;
 
     snprintf(queue->rx_irq_name, sizeof(queue->rx_irq_name),
          "%s-rx", queue->name);
     err = bind_evtchn_to_irqhandler_lateeoi(queue->rx_evtchn,
                         xennet_rx_interrupt, 0,
                         queue->rx_irq_name, queue);
     if (err < 0)
         goto bind_rx_fail;
     queue->rx_irq = err;
 
     return 0;
 
 bind_rx_fail:
     unbind_from_irqhandler(queue->tx_irq, queue);
     queue->tx_irq = 0;
 bind_tx_fail:
     xenbus_free_evtchn(queue->info->xbdev, queue->rx_evtchn);
     queue->rx_evtchn = 0;
 alloc_rx_evtchn_fail:
     xenbus_free_evtchn(queue->info->xbdev, queue->tx_evtchn);
     queue->tx_evtchn = 0;
 fail:
     return err;
 }
 
 static int setup_netfront(struct xenbus_device *dev,
             struct netfront_queue *queue, unsigned int feature_split_evtchn)
 {
     struct xen_netif_tx_sring *txs;
     struct xen_netif_rx_sring *rxs;
     int err;
 
     queue->tx_ring_ref = INVALID_GRANT_REF;
     queue->rx_ring_ref = INVALID_GRANT_REF;
     queue->rx.sring = NULL;
     queue->tx.sring = NULL;
 
     err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH, (void **)&txs,
                 1, &queue->tx_ring_ref);
     if (err)
         goto fail;
 
     XEN_FRONT_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE);
 
     err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH, (void **)&rxs,
                 1, &queue->rx_ring_ref);
     if (err)
         goto fail;
 
     XEN_FRONT_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE);
 
     if (feature_split_evtchn)
         err = setup_netfront_split(queue);
     /* setup single event channel if
      *  a) feature-split-event-channels == 0
      *  b) feature-split-event-channels == 1 but failed to setup
      */
     if (!feature_split_evtchn || err)
         err = setup_netfront_single(queue);
 
     if (err)
         goto fail;
 
     return 0;
 
  fail:
     xenbus_teardown_ring((void **)&queue->rx.sring, 1, &queue->rx_ring_ref);
     xenbus_teardown_ring((void **)&queue->tx.sring, 1, &queue->tx_ring_ref);
 
     return err;
 }
 
 /* Queue-specific initialisation
  * This used to be done in xennet_create_dev() but must now
  * be run per-queue.
  */
 static int xennet_init_queue(struct netfront_queue *queue)
 {
     unsigned short i;
     int err = 0;
     char *devid;
 
     spin_lock_init(&queue->tx_lock);
     spin_lock_init(&queue->rx_lock);
     spin_lock_init(&queue->rx_cons_lock);
 
     timer_setup(&queue->rx_refill_timer, rx_refill_timeout, 0);
 
     devid = strrchr(queue->info->xbdev->nodename, '/') + 1;
     snprintf(queue->name, sizeof(queue->name), "vif%s-q%u",
          devid, queue->id);
 
     /* Initialise tx_skb_freelist as a free chain containing every entry. */
     queue->tx_skb_freelist = 0;
     queue->tx_pend_queue = TX_LINK_NONE;
     for (i = 0; i < NET_TX_RING_SIZE; i++) {
         queue->tx_link[i] = i + 1;
         queue->grant_tx_ref[i] = INVALID_GRANT_REF;
         queue->grant_tx_page[i] = NULL;
     }
     queue->tx_link[NET_TX_RING_SIZE - 1] = TX_LINK_NONE;
 
     /* Clear out rx_skbs */
     for (i = 0; i < NET_RX_RING_SIZE; i++) {
         queue->rx_skbs[i] = NULL;
         queue->grant_rx_ref[i] = INVALID_GRANT_REF;
     }
 
     /* A grant for every tx ring slot */
     if (gnttab_alloc_grant_references(NET_TX_RING_SIZE,
                       &queue->gref_tx_head) < 0) {
         pr_alert("can't alloc tx grant refs\n");
         err = -ENOMEM;
         goto exit;
     }
 
     /* A grant for every rx ring slot */
     if (gnttab_alloc_grant_references(NET_RX_RING_SIZE,
                       &queue->gref_rx_head) < 0) {
         pr_alert("can't alloc rx grant refs\n");
         err = -ENOMEM;
         goto exit_free_tx;
     }
 
     return 0;
 
  exit_free_tx:
     gnttab_free_grant_references(queue->gref_tx_head);
  exit:
     return err;
 }
 
 static int write_queue_xenstore_keys(struct netfront_queue *queue,
                struct xenbus_transaction *xbt, int write_hierarchical)
 {
     /* Write the queue-specific keys into XenStore in the traditional
      * way for a single queue, or in a queue subkeys for multiple
      * queues.
      */
     struct xenbus_device *dev = queue->info->xbdev;
     int err;
     const char *message;
     char *path;
     size_t pathsize;
 
     /* Choose the correct place to write the keys */
     if (write_hierarchical) {
         pathsize = strlen(dev->nodename) + 10;
         path = kzalloc(pathsize, GFP_KERNEL);
         if (!path) {
             err = -ENOMEM;
             message = "out of memory while writing ring references";
             goto error;
         }
         snprintf(path, pathsize, "%s/queue-%u",
                 dev->nodename, queue->id);
     } else {
         path = (char *)dev->nodename;
     }
 
     /* Write ring references */
     err = xenbus_printf(*xbt, path, "tx-ring-ref", "%u",
             queue->tx_ring_ref);
     if (err) {
         message = "writing tx-ring-ref";
         goto error;
     }
 
     err = xenbus_printf(*xbt, path, "rx-ring-ref", "%u",
             queue->rx_ring_ref);
     if (err) {
         message = "writing rx-ring-ref";
         goto error;
     }
 
     /* Write event channels; taking into account both shared
      * and split event channel scenarios.
      */
     if (queue->tx_evtchn == queue->rx_evtchn) {
         /* Shared event channel */
         err = xenbus_printf(*xbt, path,
                 "event-channel", "%u", queue->tx_evtchn);
         if (err) {
             message = "writing event-channel";
             goto error;
         }
     } else {
         /* Split event channels */
         err = xenbus_printf(*xbt, path,
                 "event-channel-tx", "%u", queue->tx_evtchn);
         if (err) {
             message = "writing event-channel-tx";
             goto error;
         }
 
         err = xenbus_printf(*xbt, path,
                 "event-channel-rx", "%u", queue->rx_evtchn);
         if (err) {
             message = "writing event-channel-rx";
             goto error;
         }
     }
 
     if (write_hierarchical)
         kfree(path);
     return 0;
 
 error:
     if (write_hierarchical)
         kfree(path);
     xenbus_dev_fatal(dev, err, "%s", message);
     return err;
 }
 
 
 
 static int xennet_create_page_pool(struct netfront_queue *queue)
 {
     int err;
     struct page_pool_params pp_params = {
         .order = 0,
         .flags = 0,
         .pool_size = NET_RX_RING_SIZE,
         .nid = NUMA_NO_NODE,
         .dev = &queue->info->netdev->dev,
         .offset = XDP_PACKET_HEADROOM,
         .max_len = XEN_PAGE_SIZE - XDP_PACKET_HEADROOM,
     };
 
     queue->page_pool = page_pool_create(&pp_params);
     if (IS_ERR(queue->page_pool)) {
         err = PTR_ERR(queue->page_pool);
         queue->page_pool = NULL;
         return err;
     }
 
     err = xdp_rxq_info_reg(&queue->xdp_rxq, queue->info->netdev,
                    queue->id, 0);
     if (err) {
         netdev_err(queue->info->netdev, "xdp_rxq_info_reg failed\n");
         goto err_free_pp;
     }
 
     err = xdp_rxq_info_reg_mem_model(&queue->xdp_rxq,
                      MEM_TYPE_PAGE_POOL, queue->page_pool);
     if (err) {
         netdev_err(queue->info->netdev, "xdp_rxq_info_reg_mem_model failed\n");
         goto err_unregister_rxq;
     }
     return 0;
 
 err_unregister_rxq:
     xdp_rxq_info_unreg(&queue->xdp_rxq);
 err_free_pp:
     page_pool_destroy(queue->page_pool);
     queue->page_pool = NULL;
     return err;
 }
 
 static int xennet_create_queues(struct netfront_info *info,
                 unsigned int *num_queues)
 {
     unsigned int i;
     int ret;
 
     info->queues = kcalloc(*num_queues, sizeof(struct netfront_queue),
                    GFP_KERNEL);
     if (!info->queues)
         return -ENOMEM;
 
     for (i = 0; i < *num_queues; i++) {
         struct netfront_queue *queue = &info->queues[i];
 
         queue->id = i;
         queue->info = info;
 
         ret = xennet_init_queue(queue);
         if (ret < 0) {
             dev_warn(&info->xbdev->dev,
                  "only created %d queues\n", i);
             *num_queues = i;
             break;
         }
 
         /* use page pool recycling instead of buddy allocator */
         ret = xennet_create_page_pool(queue);
         if (ret < 0) {
             dev_err(&info->xbdev->dev, "can't allocate page pool\n");
             *num_queues = i;
             return ret;
         }
 
         netif_napi_add(queue->info->netdev, &queue->napi,
                    xennet_poll, 64);
         if (netif_running(info->netdev))
             napi_enable(&queue->napi);
     }
 
     netif_set_real_num_tx_queues(info->netdev, *num_queues);
 
     if (*num_queues == 0) {
         dev_err(&info->xbdev->dev, "no queues\n");
         return -EINVAL;
     }
     return 0;
 }
 
 /* Common code used when first setting up, and when resuming. */
 static int talk_to_netback(struct xenbus_device *dev,
                struct netfront_info *info)
 {
     const char *message;
     struct xenbus_transaction xbt;
     int err;
     unsigned int feature_split_evtchn;
     unsigned int i = 0;
     unsigned int max_queues = 0;
     struct netfront_queue *queue = NULL;
     unsigned int num_queues = 1;
     u8 addr[ETH_ALEN];
 
     info->netdev->irq = 0;
 
     /* Check if backend is trusted. */
     info->bounce = !xennet_trusted ||
                !xenbus_read_unsigned(dev->nodename, "trusted", 1);
 
     /* Check if backend supports multiple queues */
     max_queues = xenbus_read_unsigned(info->xbdev->otherend,
                       "multi-queue-max-queues", 1);
     num_queues = min(max_queues, xennet_max_queues);
 
     /* Check feature-split-event-channels */
     feature_split_evtchn = xenbus_read_unsigned(info->xbdev->otherend,
                     "feature-split-event-channels", 0);
 
     /* Read mac addr. */
     err = xen_net_read_mac(dev, addr);
     if (err) {
         xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
         goto out_unlocked;
     }
     eth_hw_addr_set(info->netdev, addr);
 
     info->netback_has_xdp_headroom = xenbus_read_unsigned(info->xbdev->otherend,
                                   "feature-xdp-headroom", 0);
     if (info->netback_has_xdp_headroom) {
         /* set the current xen-netfront xdp state */
         err = talk_to_netback_xdp(info, info->netfront_xdp_enabled ?
                       NETBACK_XDP_HEADROOM_ENABLE :
                       NETBACK_XDP_HEADROOM_DISABLE);
         if (err)
             goto out_unlocked;
     }
 
     rtnl_lock();
     if (info->queues)
         xennet_destroy_queues(info);
 
     /* For the case of a reconnect reset the "broken" indicator. */
     info->broken = false;
 
     err = xennet_create_queues(info, &num_queues);
     if (err < 0) {
         xenbus_dev_fatal(dev, err, "creating queues");
         kfree(info->queues);
         info->queues = NULL;
         goto out;
     }
     rtnl_unlock();
 
     /* Create shared ring, alloc event channel -- for each queue */
     for (i = 0; i < num_queues; ++i) {
         queue = &info->queues[i];
         err = setup_netfront(dev, queue, feature_split_evtchn);
         if (err)
             goto destroy_ring;
     }
 
 again:
     err = xenbus_transaction_start(&xbt);
     if (err) {
         xenbus_dev_fatal(dev, err, "starting transaction");
         goto destroy_ring;
     }
 
     if (xenbus_exists(XBT_NIL,
               info->xbdev->otherend, "multi-queue-max-queues")) {
         /* Write the number of queues */
         err = xenbus_printf(xbt, dev->nodename,
                     "multi-queue-num-queues", "%u", num_queues);
         if (err) {
             message = "writing multi-queue-num-queues";
             goto abort_transaction_no_dev_fatal;
         }
     }
 
     if (num_queues == 1) {
         err = write_queue_xenstore_keys(&info->queues[0], &xbt, 0); /* flat */
         if (err)
             goto abort_transaction_no_dev_fatal;
     } else {
         /* Write the keys for each queue */
         for (i = 0; i < num_queues; ++i) {
             queue = &info->queues[i];
             err = write_queue_xenstore_keys(queue, &xbt, 1); /* hierarchical */
             if (err)
                 goto abort_transaction_no_dev_fatal;
         }
     }
 
     /* The remaining keys are not queue-specific */
     err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u",
                 1);
     if (err) {
         message = "writing request-rx-copy";
         goto abort_transaction;
     }
 
     err = xenbus_printf(xbt, dev->nodename, "feature-rx-notify", "%d", 1);
     if (err) {
         message = "writing feature-rx-notify";
         goto abort_transaction;
     }
 
     err = xenbus_printf(xbt, dev->nodename, "feature-sg", "%d", 1);
     if (err) {
         message = "writing feature-sg";
         goto abort_transaction;
     }
 
     err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv4", "%d", 1);
     if (err) {
         message = "writing feature-gso-tcpv4";
         goto abort_transaction;
     }
 
     err = xenbus_write(xbt, dev->nodename, "feature-gso-tcpv6", "1");
     if (err) {
         message = "writing feature-gso-tcpv6";
         goto abort_transaction;
     }
 
     err = xenbus_write(xbt, dev->nodename, "feature-ipv6-csum-offload",
                "1");
     if (err) {
         message = "writing feature-ipv6-csum-offload";
         goto abort_transaction;
     }
 
     err = xenbus_transaction_end(xbt, 0);
     if (err) {
         if (err == -EAGAIN)
             goto again;
         xenbus_dev_fatal(dev, err, "completing transaction");
         goto destroy_ring;
     }
 
     return 0;
 
  abort_transaction:
     xenbus_dev_fatal(dev, err, "%s", message);
 abort_transaction_no_dev_fatal:
     xenbus_transaction_end(xbt, 1);
  destroy_ring:
     xennet_disconnect_backend(info);
     rtnl_lock();
     xennet_destroy_queues(info);
  out:
     rtnl_unlock();
 out_unlocked:
     device_unregister(&dev->dev);
     return err;
 }
 
 static int xennet_connect(struct net_device *dev)
 {
     struct netfront_info *np = netdev_priv(dev);
     unsigned int num_queues = 0;
     int err;
     unsigned int j = 0;
     struct netfront_queue *queue = NULL;
 
     if (!xenbus_read_unsigned(np->xbdev->otherend, "feature-rx-copy", 0)) {
         dev_info(&dev->dev,
              "backend does not support copying receive path\n");
         return -ENODEV;
     }
 
     err = talk_to_netback(np->xbdev, np);
     if (err)
         return err;
     if (np->netback_has_xdp_headroom)
         pr_info("backend supports XDP headroom\n");
     if (np->bounce)
         dev_info(&np->xbdev->dev,
              "bouncing transmitted data to zeroed pages\n");
 
     /* talk_to_netback() sets the correct number of queues */
     num_queues = dev->real_num_tx_queues;
 
     if (dev->reg_state == NETREG_UNINITIALIZED) {
         err = register_netdev(dev);
         if (err) {
             pr_warn("%s: register_netdev err=%d\n", __func__, err);
             device_unregister(&np->xbdev->dev);
             return err;
         }
     }
 
     rtnl_lock();
     netdev_update_features(dev);
     rtnl_unlock();
 
     /*
      * All public and private state should now be sane.  Get
      * ready to start sending and receiving packets and give the driver
      * domain a kick because we've probably just requeued some
      * packets.
      */
     netif_tx_lock_bh(np->netdev);
     netif_device_attach(np->netdev);
     netif_tx_unlock_bh(np->netdev);
 
     netif_carrier_on(np->netdev);
     for (j = 0; j < num_queues; ++j) {
         queue = &np->queues[j];
 
         notify_remote_via_irq(queue->tx_irq);
         if (queue->tx_irq != queue->rx_irq)
             notify_remote_via_irq(queue->rx_irq);
 
         spin_lock_bh(&queue->rx_lock);
         xennet_alloc_rx_buffers(queue);
         spin_unlock_bh(&queue->rx_lock);
     }
 
     return 0;
 }
 
 /*
  * Callback received when the backend's state changes.
  */
 static void netback_changed(struct xenbus_device *dev,
                 enum xenbus_state backend_state)
 {
     struct netfront_info *np = dev_get_drvdata(&dev->dev);
     struct net_device *netdev = np->netdev;
 
     dev_dbg(&dev->dev, "%s\n", xenbus_strstate(backend_state));
 
     wake_up_all(&module_wq);
 
     switch (backend_state) {
     case XenbusStateInitialising:
     case XenbusStateInitialised:
     case XenbusStateReconfiguring:
     case XenbusStateReconfigured:
     case XenbusStateUnknown:
         break;
 
     case XenbusStateInitWait:
         if (dev->state != XenbusStateInitialising)
             break;
         if (xennet_connect(netdev) != 0)
             break;
         xenbus_switch_state(dev, XenbusStateConnected);
         break;
 
     case XenbusStateConnected:
         netdev_notify_peers(netdev);
         break;
 
     case XenbusStateClosed:
         if (dev->state == XenbusStateClosed)
             break;
         fallthrough;    /* Missed the backend's CLOSING state */
     case XenbusStateClosing:
         xenbus_frontend_closed(dev);
         break;
     }
 }
 
 static const struct xennet_stat {
     char name[ETH_GSTRING_LEN];
     u16 offset;
 } xennet_stats[] = {
     {
         "rx_gso_checksum_fixup",
         offsetof(struct netfront_info, rx_gso_checksum_fixup)
     },
 };
 
 static int xennet_get_sset_count(struct net_device *dev, int string_set)
 {
     switch (string_set) {
     case ETH_SS_STATS:
         return ARRAY_SIZE(xennet_stats);
     default:
         return -EINVAL;
     }
 }
 
 static void xennet_get_ethtool_stats(struct net_device *dev,
                      struct ethtool_stats *stats, u64 * data)
 {
     void *np = netdev_priv(dev);
     int i;
 
     for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
         data[i] = atomic_read((atomic_t *)(np + xennet_stats[i].offset));
 }
 
 static void xennet_get_strings(struct net_device *dev, u32 stringset, u8 * data)
 {
     int i;
 
     switch (stringset) {
     case ETH_SS_STATS:
         for (i = 0; i < ARRAY_SIZE(xennet_stats); i++)
             memcpy(data + i * ETH_GSTRING_LEN,
                    xennet_stats[i].name, ETH_GSTRING_LEN);
         break;
     }
 }
 
 static const struct ethtool_ops xennet_ethtool_ops =
 {
     .get_link = ethtool_op_get_link,
 
     .get_sset_count = xennet_get_sset_count,
     .get_ethtool_stats = xennet_get_ethtool_stats,
     .get_strings = xennet_get_strings,
     .get_ts_info = ethtool_op_get_ts_info,
 };
 
 #ifdef CONFIG_SYSFS
 static ssize_t show_rxbuf(struct device *dev,
               struct device_attribute *attr, char *buf)
 {
     return sprintf(buf, "%lu\n", NET_RX_RING_SIZE);
 }
 
 static ssize_t store_rxbuf(struct device *dev,
                struct device_attribute *attr,
                const char *buf, size_t len)
 {
     char *endp;
 
     if (!capable(CAP_NET_ADMIN))
         return -EPERM;
 
     simple_strtoul(buf, &endp, 0);
     if (endp == buf)
         return -EBADMSG;
 
     /* rxbuf_min and rxbuf_max are no longer configurable. */
 
     return len;
 }
 
 static DEVICE_ATTR(rxbuf_min, 0644, show_rxbuf, store_rxbuf);
 static DEVICE_ATTR(rxbuf_max, 0644, show_rxbuf, store_rxbuf);
 static DEVICE_ATTR(rxbuf_cur, 0444, show_rxbuf, NULL);
 
 static struct attribute *xennet_dev_attrs[] = {
     &dev_attr_rxbuf_min.attr,
     &dev_attr_rxbuf_max.attr,
     &dev_attr_rxbuf_cur.attr,
     NULL
 };
 
 static const struct attribute_group xennet_dev_group = {
     .attrs = xennet_dev_attrs
 };
 #endif /* CONFIG_SYSFS */
 
 static void xennet_bus_close(struct xenbus_device *dev)
 {
     int ret;
 
     if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
         return;
     do {
         xenbus_switch_state(dev, XenbusStateClosing);
         ret = wait_event_timeout(module_wq,
                    xenbus_read_driver_state(dev->otherend) ==
                    XenbusStateClosing ||
                    xenbus_read_driver_state(dev->otherend) ==
                    XenbusStateClosed ||
                    xenbus_read_driver_state(dev->otherend) ==
                    XenbusStateUnknown,
                    XENNET_TIMEOUT);
     } while (!ret);
 
     if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
         return;
 
     do {
         xenbus_switch_state(dev, XenbusStateClosed);
         ret = wait_event_timeout(module_wq,
                    xenbus_read_driver_state(dev->otherend) ==
                    XenbusStateClosed ||
                    xenbus_read_driver_state(dev->otherend) ==
                    XenbusStateUnknown,
                    XENNET_TIMEOUT);
     } while (!ret);
 }
 
 static int xennet_remove(struct xenbus_device *dev)
 {
     struct netfront_info *info = dev_get_drvdata(&dev->dev);
 
     xennet_bus_close(dev);
     xennet_disconnect_backend(info);
 
     if (info->netdev->reg_state == NETREG_REGISTERED)
         unregister_netdev(info->netdev);
 
     if (info->queues) {
         rtnl_lock();
         xennet_destroy_queues(info);
         rtnl_unlock();
     }
     xennet_free_netdev(info->netdev);
 
     return 0;
 }
 
 static const struct xenbus_device_id netfront_ids[] = {
     { "vif" },
     { "" }
 };
 
 static struct xenbus_driver netfront_driver = {
     .ids = netfront_ids,
     .probe = netfront_probe,
     .remove = xennet_remove,
     .resume = netfront_resume,
     .otherend_changed = netback_changed,
 };
 
 static int __init netif_init(void)
 {
     if (!xen_domain())
         return -ENODEV;
 
     if (!xen_has_pv_nic_devices())
         return -ENODEV;
 
     pr_info("Initialising Xen virtual ethernet driver\n");
 
     /* Allow as many queues as there are CPUs inut max. 8 if user has not
      * specified a value.
      */
     if (xennet_max_queues == 0)
         xennet_max_queues = min_t(unsigned int, MAX_QUEUES_DEFAULT,
                       num_online_cpus());
 
     return xenbus_register_frontend(&netfront_driver);
 }
 module_init(netif_init);
 
 
 static void __exit netif_exit(void)
 {
     xenbus_unregister_driver(&netfront_driver);
 }
 module_exit(netif_exit);
 
 MODULE_DESCRIPTION("Xen virtual network device frontend");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("xen:vif");
 MODULE_ALIAS("xennet");