Initial import

1 files changed, 2159 insertions, 0 deletions

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
new file mode 100644
index 000000000..e031c9432
--- /dev/null
+++ b/drivers/net/xen-netfront.c
@@ -0,0 +1,2159 @@
+/*
+ * 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 <asm/xen/page.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 */
+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 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 GRANT_INVALID_REF	0
+
+#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
+#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, 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)
+
+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 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 skb_entry.link.
+	 *
+	 *  NB. Freelist index entries are always going to be less than
+	 *  PAGE_OFFSET, whereas pointers to skbs will always be equal or
+	 *  greater than PAGE_OFFSET: we use this property to distinguish
+	 *  them.
+	 */
+	union skb_entry {
+		struct sk_buff *skb;
+		unsigned long link;
+	} tx_skbs[NET_TX_RING_SIZE];
+	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;
+
+	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];
+};
+
+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;
+
+	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];
+};
+
+static void skb_entry_set_link(union skb_entry *list, unsigned short id)
+{
+	list->link = id;
+}
+
+static int skb_entry_is_link(const union skb_entry *list)
+{
+	BUILD_BUG_ON(sizeof(list->skb) != sizeof(list->link));
+	return (unsigned long)list->skb < PAGE_OFFSET;
+}
+
+/*
+ * Access macros for acquiring freeing slots in tx_skbs[].
+ */
+
+static void add_id_to_freelist(unsigned *head, union skb_entry *list,
+			       unsigned short id)
+{
+	skb_entry_set_link(&list[id], *head);
+	*head = id;
+}
+
+static unsigned short get_id_from_freelist(unsigned *head,
+					   union skb_entry *list)
+{
+	unsigned int id = *head;
+	*head = list[id].link;
+	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] = GRANT_INVALID_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(unsigned long data)
+{
+	struct netfront_queue *queue = (struct netfront_queue *)data;
+	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 - MAX_SKB_FRAGS - 2);
+}
+
+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 = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
+	if (!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;
+
+	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;
+		unsigned long pfn;
+		struct xen_netif_rx_request *req;
+
+		skb = xennet_alloc_one_rx_buffer(queue);
+		if (!skb)
+			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);
+		BUG_ON((signed short)ref < 0);
+		queue->grant_rx_ref[id] = ref;
+
+		pfn = page_to_pfn(skb_frag_page(&skb_shinfo(skb)->frags[0]));
+
+		req = RING_GET_REQUEST(&queue->rx, req_prod);
+		gnttab_grant_foreign_access_ref(ref,
+						queue->info->xbdev->otherend_id,
+						pfn_to_mfn(pfn),
+						0);
+
+		req->id = id;
+		req->gref = ref;
+	}
+
+	queue->rx.req_prod_pvt = req_prod;
+
+	/* Not enough requests? Try again later. */
+	if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN) {
+		mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10));
+		return;
+	}
+
+	wmb();		/* barrier so backend seens requests */
+
+	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;
+
+	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 void xennet_tx_buf_gc(struct netfront_queue *queue)
+{
+	RING_IDX cons, prod;
+	unsigned short id;
+	struct sk_buff *skb;
+
+	BUG_ON(!netif_carrier_ok(queue->info->netdev));
+
+	do {
+		prod = queue->tx.sring->rsp_prod;
+		rmb(); /* Ensure we see responses up to 'rp'. */
+
+		for (cons = queue->tx.rsp_cons; cons != prod; cons++) {
+			struct xen_netif_tx_response *txrsp;
+
+			txrsp = RING_GET_RESPONSE(&queue->tx, cons);
+			if (txrsp->status == XEN_NETIF_RSP_NULL)
+				continue;
+
+			id  = txrsp->id;
+			skb = queue->tx_skbs[id].skb;
+			if (unlikely(gnttab_query_foreign_access(
+				queue->grant_tx_ref[id]) != 0)) {
+				pr_alert("%s: warning -- grant still in use by backend domain\n",
+					 __func__);
+				BUG();
+			}
+			gnttab_end_foreign_access_ref(
+				queue->grant_tx_ref[id], GNTMAP_readonly);
+			gnttab_release_grant_reference(
+				&queue->gref_tx_head, queue->grant_tx_ref[id]);
+			queue->grant_tx_ref[id] = GRANT_INVALID_REF;
+			queue->grant_tx_page[id] = NULL;
+			add_id_to_freelist(&queue->tx_skb_freelist, queue->tx_skbs, id);
+			dev_kfree_skb_irq(skb);
+		}
+
+		queue->tx.rsp_cons = prod;
+
+		/*
+		 * Set a new event, then check for race with update of tx_cons.
+		 * Note that it is essential to schedule a callback, no matter
+		 * how few buffers are pending. Even if there is space in the
+		 * transmit ring, higher layers may be blocked because too much
+		 * data is outstanding: in such cases notification from Xen is
+		 * likely to be the only kick that we'll get.
+		 */
+		queue->tx.sring->rsp_event =
+			prod + ((queue->tx.sring->req_prod - prod) >> 1) + 1;
+		mb();		/* update shared area */
+	} while ((cons == prod) && (prod != queue->tx.sring->rsp_prod));
+
+	xennet_maybe_wake_tx(queue);
+}
+
+static struct xen_netif_tx_request *xennet_make_one_txreq(
+	struct netfront_queue *queue, struct sk_buff *skb,
+	struct page *page, unsigned int offset, unsigned int len)
+{
+	unsigned int id;
+	struct xen_netif_tx_request *tx;
+	grant_ref_t ref;
+
+	len = min_t(unsigned int, PAGE_SIZE - offset, len);
+
+	id = get_id_from_freelist(&queue->tx_skb_freelist, queue->tx_skbs);
+	tx = RING_GET_REQUEST(&queue->tx, queue->tx.req_prod_pvt++);
+	ref = gnttab_claim_grant_reference(&queue->gref_tx_head);
+	BUG_ON((signed short)ref < 0);
+
+	gnttab_grant_foreign_access_ref(ref, queue->info->xbdev->otherend_id,
+					page_to_mfn(page), GNTMAP_readonly);
+
+	queue->tx_skbs[id].skb = skb;
+	queue->grant_tx_page[id] = page;
+	queue->grant_tx_ref[id] = ref;
+
+	tx->id = id;
+	tx->gref = ref;
+	tx->offset = offset;
+	tx->size = len;
+	tx->flags = 0;
+
+	return tx;
+}
+
+static struct xen_netif_tx_request *xennet_make_txreqs(
+	struct netfront_queue *queue, struct xen_netif_tx_request *tx,
+	struct sk_buff *skb, 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) {
+		tx->flags |= XEN_NETTXF_more_data;
+		tx = xennet_make_one_txreq(queue, skb_get(skb),
+					   page, offset, len);
+		page++;
+		offset = 0;
+		len -= tx->size;
+	}
+
+	return tx;
+}
+
+/*
+ * 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 pages;
+
+	pages = PFN_UP(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 = frag->page_offset;
+
+		/* Skip unused frames from start of page */
+		offset &= ~PAGE_MASK;
+
+		pages += PFN_UP(offset + size);
+	}
+
+	return pages;
+}
+
+static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
+			       void *accel_priv, select_queue_fallback_t fallback)
+{
+	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 int 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 *tx, *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;
+	unsigned int num_queues = dev->real_num_tx_queues;
+	u16 queue_index;
+
+	/* Drop the packet if no queues are set up */
+	if (num_queues < 1)
+		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_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);
+	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. */
+	first_tx = tx = xennet_make_one_txreq(queue, skb,
+					      page, offset, len);
+	page++;
+	offset = 0;
+	len -= tx->size;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL)
+		/* local packet? */
+		tx->flags |= XEN_NETTXF_csum_blank | XEN_NETTXF_data_validated;
+	else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
+		/* remote but checksummed. */
+		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++);
+
+		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. */
+	tx = xennet_make_txreqs(queue, tx, skb, 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];
+		tx = xennet_make_txreqs(queue, tx, skb,
+					skb_frag_page(frag), frag->page_offset,
+					skb_frag_size(frag));
+	}
+
+	/* First request has the packet length. */
+	first_tx->size = skb->len;
+
+	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_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;
+		}
+
+		extra = (struct xen_netif_extra_info *)
+			RING_GET_RESPONSE(&queue->rx, ++cons);
+
+		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 {
+			memcpy(&extras[extra->type - 1], extra,
+			       sizeof(*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);
+
+	queue->rx.rsp_cons = cons;
+	return err;
+}
+
+static int xennet_get_responses(struct netfront_queue *queue,
+				struct netfront_rx_info *rinfo, RING_IDX rp,
+				struct sk_buff_head *list)
+{
+	struct xen_netif_rx_response *rx = &rinfo->rx;
+	struct xen_netif_extra_info *extras = rinfo->extras;
+	struct device *dev = &queue->info->netdev->dev;
+	RING_IDX cons = queue->rx.rsp_cons;
+	struct sk_buff *skb = xennet_get_rx_skb(queue, cons);
+	grant_ref_t ref = xennet_get_rx_ref(queue, cons);
+	int max = MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD);
+	int slots = 1;
+	int err = 0;
+	unsigned long ret;
+
+	if (rx->flags & XEN_NETRXF_extra_info) {
+		err = xennet_get_extras(queue, extras, rp);
+		cons = queue->rx.rsp_cons;
+	}
+
+	for (;;) {
+		if (unlikely(rx->status < 0 ||
+			     rx->offset + rx->status > PAGE_SIZE)) {
+			if (net_ratelimit())
+				dev_warn(dev, "rx->offset: %x, size: %u\n",
+					 rx->offset, rx->status);
+			xennet_move_rx_slot(queue, skb, ref);
+			err = -EINVAL;
+			goto next;
+		}
+
+		/*
+		 * 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 == GRANT_INVALID_REF) {
+			if (net_ratelimit())
+				dev_warn(dev, "Bad rx response id %d.\n",
+					 rx->id);
+			err = -EINVAL;
+			goto next;
+		}
+
+		ret = gnttab_end_foreign_access_ref(ref, 0);
+		BUG_ON(!ret);
+
+		gnttab_release_grant_reference(&queue->gref_rx_head, ref);
+
+		__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;
+		}
+
+		rx = RING_GET_RESPONSE(&queue->rx, cons + slots);
+		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))
+		queue->rx.rsp_cons = 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 RING_IDX xennet_fill_frags(struct netfront_queue *queue,
+				  struct sk_buff *skb,
+				  struct sk_buff_head *list)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	RING_IDX cons = queue->rx.rsp_cons;
+	struct sk_buff *nskb;
+
+	while ((nskb = __skb_dequeue(list))) {
+		struct xen_netif_rx_response *rx =
+			RING_GET_RESPONSE(&queue->rx, ++cons);
+		skb_frag_t *nfrag = &skb_shinfo(nskb)->frags[0];
+
+		if (shinfo->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));
+		}
+		BUG_ON(shinfo->nr_frags >= MAX_SKB_FRAGS);
+
+		skb_add_rx_frag(skb, shinfo->nr_frags, skb_frag_page(nfrag),
+				rx->offset, rx->status, PAGE_SIZE);
+
+		skb_shinfo(nskb)->nr_frags = 0;
+		kfree_skb(nskb);
+	}
+
+	return cons;
+}
+
+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;
+
+	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;
+	rmb(); /* Ensure we see queued responses up to 'rp'. */
+
+	i = queue->rx.rsp_cons;
+	work_done = 0;
+	while ((i != rp) && (work_done < budget)) {
+		memcpy(rx, RING_GET_RESPONSE(&queue->rx, i), sizeof(*rx));
+		memset(extras, 0, sizeof(rinfo.extras));
+
+		err = xennet_get_responses(queue, &rinfo, rp, &tmpq);
+
+		if (unlikely(err)) {
+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);
+				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_shinfo(skb)->frags[0].page_offset = rx->offset;
+		skb_frag_size_set(&skb_shinfo(skb)->frags[0], rx->status);
+		skb->data_len = rx->status;
+		skb->len += rx->status;
+
+		i = xennet_fill_frags(queue, skb, &tmpq);
+
+		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);
+
+		queue->rx.rsp_cons = ++i;
+		work_done++;
+	}
+
+	__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(napi);
+
+		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 struct rtnl_link_stats64 *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;
+
+	return tot;
+}
+
+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 (skb_entry_is_link(&queue->tx_skbs[i]))
+			continue;
+
+		skb = queue->tx_skbs[i].skb;
+		get_page(queue->grant_tx_page[i]);
+		gnttab_end_foreign_access(queue->grant_tx_ref[i],
+					  GNTMAP_readonly,
+					  (unsigned long)page_address(queue->grant_tx_page[i]));
+		queue->grant_tx_page[i] = NULL;
+		queue->grant_tx_ref[i] = GRANT_INVALID_REF;
+		add_id_to_freelist(&queue->tx_skb_freelist, queue->tx_skbs, 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 == GRANT_INVALID_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, 0,
+					  (unsigned long)page_address(page));
+		queue->grant_rx_ref[id] = GRANT_INVALID_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);
+	int val;
+
+	if (features & NETIF_F_SG) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend, "feature-sg",
+				 "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			features &= ~NETIF_F_SG;
+	}
+
+	if (features & NETIF_F_IPV6_CSUM) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+				 "feature-ipv6-csum-offload", "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			features &= ~NETIF_F_IPV6_CSUM;
+	}
+
+	if (features & NETIF_F_TSO) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+				 "feature-gso-tcpv4", "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			features &= ~NETIF_F_TSO;
+	}
+
+	if (features & NETIF_F_TSO6) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+				 "feature-gso-tcpv6", "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			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 irqreturn_t xennet_tx_interrupt(int irq, void *dev_id)
+{
+	struct netfront_queue *queue = dev_id;
+	unsigned long flags;
+
+	spin_lock_irqsave(&queue->tx_lock, flags);
+	xennet_tx_buf_gc(queue);
+	spin_unlock_irqrestore(&queue->tx_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t xennet_rx_interrupt(int irq, void *dev_id)
+{
+	struct netfront_queue *queue = dev_id;
+	struct net_device *dev = queue->info->netdev;
+
+	if (likely(netif_carrier_ok(dev) &&
+		   RING_HAS_UNCONSUMED_RESPONSES(&queue->rx)))
+		napi_schedule(&queue->napi);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t xennet_interrupt(int irq, void *dev_id)
+{
+	xennet_tx_interrupt(irq, dev_id);
+	xennet_rx_interrupt(irq, dev_id);
+	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;
+	for (i = 0; i < num_queues; ++i)
+		xennet_interrupt(0, &info->queues[i]);
+}
+#endif
+
+static const struct net_device_ops xennet_netdev_ops = {
+	.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,
+#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;
+
+	/* No need to use rtnl_lock() before the call below as it
+	 * happens before register_netdev().
+	 */
+	netif_set_real_num_tx_queues(netdev, 0);
+	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;
+	SET_NETDEV_DEV(netdev, &dev->dev);
+
+	np->netdev = netdev;
+
+	netif_carrier_off(netdev);
+
+	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
+	err = register_netdev(info->netdev);
+	if (err) {
+		pr_warn("%s: register_netdev err=%d\n", __func__, err);
+		goto fail;
+	}
+
+	return 0;
+
+ fail:
+	xennet_free_netdev(netdev);
+	dev_set_drvdata(&dev->dev, NULL);
+	return err;
+}
+
+static void xennet_end_access(int ref, void *page)
+{
+	/* This frees the page as a side-effect */
+	if (ref != GRANT_INVALID_REF)
+		gnttab_end_foreign_access(ref, 0, (unsigned long)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; ++i) {
+		struct netfront_queue *queue = &info->queues[i];
+
+		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;
+
+		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 = GRANT_INVALID_REF;
+		queue->rx_ring_ref = GRANT_INVALID_REF;
+		queue->tx.sring = NULL;
+		queue->rx.sring = NULL;
+	}
+}
+
+/**
+ * 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);
+
+	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(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(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(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;
+	grant_ref_t gref;
+	int err;
+
+	queue->tx_ring_ref = GRANT_INVALID_REF;
+	queue->rx_ring_ref = GRANT_INVALID_REF;
+	queue->rx.sring = NULL;
+	queue->tx.sring = NULL;
+
+	txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
+	if (!txs) {
+		err = -ENOMEM;
+		xenbus_dev_fatal(dev, err, "allocating tx ring page");
+		goto fail;
+	}
+	SHARED_RING_INIT(txs);
+	FRONT_RING_INIT(&queue->tx, txs, PAGE_SIZE);
+
+	err = xenbus_grant_ring(dev, txs, 1, &gref);
+	if (err < 0)
+		goto grant_tx_ring_fail;
+	queue->tx_ring_ref = gref;
+
+	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
+	if (!rxs) {
+		err = -ENOMEM;
+		xenbus_dev_fatal(dev, err, "allocating rx ring page");
+		goto alloc_rx_ring_fail;
+	}
+	SHARED_RING_INIT(rxs);
+	FRONT_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
+
+	err = xenbus_grant_ring(dev, rxs, 1, &gref);
+	if (err < 0)
+		goto grant_rx_ring_fail;
+	queue->rx_ring_ref = gref;
+
+	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 || (feature_split_evtchn && err))
+		err = setup_netfront_single(queue);
+
+	if (err)
+		goto alloc_evtchn_fail;
+
+	return 0;
+
+	/* If we fail to setup netfront, it is safe to just revoke access to
+	 * granted pages because backend is not accessing it at this point.
+	 */
+alloc_evtchn_fail:
+	gnttab_end_foreign_access_ref(queue->rx_ring_ref, 0);
+grant_rx_ring_fail:
+	free_page((unsigned long)rxs);
+alloc_rx_ring_fail:
+	gnttab_end_foreign_access_ref(queue->tx_ring_ref, 0);
+grant_tx_ring_fail:
+	free_page((unsigned long)txs);
+fail:
+	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;
+
+	spin_lock_init(&queue->tx_lock);
+	spin_lock_init(&queue->rx_lock);
+
+	init_timer(&queue->rx_refill_timer);
+	queue->rx_refill_timer.data = (unsigned long)queue;
+	queue->rx_refill_timer.function = rx_refill_timeout;
+
+	snprintf(queue->name, sizeof(queue->name), "%s-q%u",
+		 queue->info->netdev->name, queue->id);
+
+	/* Initialise tx_skbs as a free chain containing every entry. */
+	queue->tx_skb_freelist = 0;
+	for (i = 0; i < NET_TX_RING_SIZE; i++) {
+		skb_entry_set_link(&queue->tx_skbs[i], i+1);
+		queue->grant_tx_ref[i] = GRANT_INVALID_REF;
+		queue->grant_tx_page[i] = NULL;
+	}
+
+	/* Clear out rx_skbs */
+	for (i = 0; i < NET_RX_RING_SIZE; i++) {
+		queue->rx_skbs[i] = NULL;
+		queue->grant_rx_ref[i] = GRANT_INVALID_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 void xennet_destroy_queues(struct netfront_info *info)
+{
+	unsigned int i;
+
+	rtnl_lock();
+
+	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);
+		del_timer_sync(&queue->rx_refill_timer);
+		netif_napi_del(&queue->napi);
+	}
+
+	rtnl_unlock();
+
+	kfree(info->queues);
+	info->queues = NULL;
+}
+
+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;
+
+	rtnl_lock();
+
+	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->netdev->dev,
+				 "only created %d queues\n", i);
+			num_queues = i;
+			break;
+		}
+
+		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);
+
+	rtnl_unlock();
+
+	if (num_queues == 0) {
+		dev_err(&info->netdev->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;
+
+	info->netdev->irq = 0;
+
+	/* Check if backend supports multiple queues */
+	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+			   "multi-queue-max-queues", "%u", &max_queues);
+	if (err < 0)
+		max_queues = 1;
+	num_queues = min(max_queues, xennet_max_queues);
+
+	/* Check feature-split-event-channels */
+	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+			   "feature-split-event-channels", "%u",
+			   &feature_split_evtchn);
+	if (err < 0)
+		feature_split_evtchn = 0;
+
+	/* Read mac addr. */
+	err = xen_net_read_mac(dev, info->netdev->dev_addr);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
+		goto out;
+	}
+
+	if (info->queues)
+		xennet_destroy_queues(info);
+
+	err = xennet_create_queues(info, num_queues);
+	if (err < 0)
+		goto destroy_ring;
+
+	/* 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) {
+			/* setup_netfront() will tidy up the current
+			 * queue on error, but we need to clean up
+			 * those already allocated.
+			 */
+			if (i > 0) {
+				rtnl_lock();
+				netif_set_real_num_tx_queues(info->netdev, i);
+				rtnl_unlock();
+				goto destroy_ring;
+			} else {
+				goto out;
+			}
+		}
+	}
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "starting transaction");
+		goto destroy_ring;
+	}
+
+	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 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;
+		}
+
+		/* 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);
+	kfree(info->queues);
+	info->queues = NULL;
+	rtnl_lock();
+	netif_set_real_num_tx_queues(info->netdev, 0);
+	rtnl_unlock();
+ out:
+	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 feature_rx_copy;
+	unsigned int j = 0;
+	struct netfront_queue *queue = NULL;
+
+	err = xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+			   "feature-rx-copy", "%u", &feature_rx_copy);
+	if (err != 1)
+		feature_rx_copy = 0;
+
+	if (!feature_rx_copy) {
+		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;
+
+	/* talk_to_netback() sets the correct number of queues */
+	num_queues = dev->real_num_tx_queues;
+
+	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_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_irq(&queue->tx_lock);
+		xennet_tx_buf_gc(queue);
+		spin_unlock_irq(&queue->tx_lock);
+
+		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));
+
+	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;
+		/* Missed the backend's CLOSING state -- fallthrough */
+	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,
+};
+
+#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;
+	unsigned long target;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	target = 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, S_IRUGO|S_IWUSR, show_rxbuf, store_rxbuf);
+static DEVICE_ATTR(rxbuf_max, S_IRUGO|S_IWUSR, show_rxbuf, store_rxbuf);
+static DEVICE_ATTR(rxbuf_cur, S_IRUGO, 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 int xennet_remove(struct xenbus_device *dev)
+{
+	struct netfront_info *info = dev_get_drvdata(&dev->dev);
+
+	dev_dbg(&dev->dev, "%s\n", dev->nodename);
+
+	xennet_disconnect_backend(info);
+
+	unregister_netdev(info->netdev);
+
+	xennet_destroy_queues(info);
+	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, by default */
+	xennet_max_queues = 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");