Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 1043 insertions, 0 deletions

diff --git a/kernel/drivers/net/xen-netback/xenbus.c b/kernel/drivers/net/xen-netback/xenbus.c
new file mode 100644
index 000000000..ec383b0f5
--- /dev/null
+++ b/kernel/drivers/net/xen-netback/xenbus.c
@@ -0,0 +1,1043 @@
+/*
+ * Xenbus code for netif backend
+ *
+ * Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
+ * 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 as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "common.h"
+#include <linux/vmalloc.h>
+#include <linux/rtnetlink.h>
+
+struct backend_info {
+	struct xenbus_device *dev;
+	struct xenvif *vif;
+
+	/* This is the state that will be reflected in xenstore when any
+	 * active hotplug script completes.
+	 */
+	enum xenbus_state state;
+
+	enum xenbus_state frontend_state;
+	struct xenbus_watch hotplug_status_watch;
+	u8 have_hotplug_status_watch:1;
+
+	const char *hotplug_script;
+};
+
+static int connect_rings(struct backend_info *be, struct xenvif_queue *queue);
+static void connect(struct backend_info *be);
+static int read_xenbus_vif_flags(struct backend_info *be);
+static int backend_create_xenvif(struct backend_info *be);
+static void unregister_hotplug_status_watch(struct backend_info *be);
+static void xen_unregister_watchers(struct xenvif *vif);
+static void set_backend_state(struct backend_info *be,
+			      enum xenbus_state state);
+
+#ifdef CONFIG_DEBUG_FS
+struct dentry *xen_netback_dbg_root = NULL;
+
+static int xenvif_read_io_ring(struct seq_file *m, void *v)
+{
+	struct xenvif_queue *queue = m->private;
+	struct xen_netif_tx_back_ring *tx_ring = &queue->tx;
+	struct xen_netif_rx_back_ring *rx_ring = &queue->rx;
+	struct netdev_queue *dev_queue;
+
+	if (tx_ring->sring) {
+		struct xen_netif_tx_sring *sring = tx_ring->sring;
+
+		seq_printf(m, "Queue %d\nTX: nr_ents %u\n", queue->id,
+			   tx_ring->nr_ents);
+		seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+			   sring->req_prod,
+			   sring->req_prod - sring->rsp_prod,
+			   tx_ring->req_cons,
+			   tx_ring->req_cons - sring->rsp_prod,
+			   sring->req_event,
+			   sring->req_event - sring->rsp_prod);
+		seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n",
+			   sring->rsp_prod,
+			   tx_ring->rsp_prod_pvt,
+			   tx_ring->rsp_prod_pvt - sring->rsp_prod,
+			   sring->rsp_event,
+			   sring->rsp_event - sring->rsp_prod);
+		seq_printf(m, "pending prod %u pending cons %u nr_pending_reqs %u\n",
+			   queue->pending_prod,
+			   queue->pending_cons,
+			   nr_pending_reqs(queue));
+		seq_printf(m, "dealloc prod %u dealloc cons %u dealloc_queue %u\n\n",
+			   queue->dealloc_prod,
+			   queue->dealloc_cons,
+			   queue->dealloc_prod - queue->dealloc_cons);
+	}
+
+	if (rx_ring->sring) {
+		struct xen_netif_rx_sring *sring = rx_ring->sring;
+
+		seq_printf(m, "RX: nr_ents %u\n", rx_ring->nr_ents);
+		seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+			   sring->req_prod,
+			   sring->req_prod - sring->rsp_prod,
+			   rx_ring->req_cons,
+			   rx_ring->req_cons - sring->rsp_prod,
+			   sring->req_event,
+			   sring->req_event - sring->rsp_prod);
+		seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n\n",
+			   sring->rsp_prod,
+			   rx_ring->rsp_prod_pvt,
+			   rx_ring->rsp_prod_pvt - sring->rsp_prod,
+			   sring->rsp_event,
+			   sring->rsp_event - sring->rsp_prod);
+	}
+
+	seq_printf(m, "NAPI state: %lx NAPI weight: %d TX queue len %u\n"
+		   "Credit timer_pending: %d, credit: %lu, usec: %lu\n"
+		   "remaining: %lu, expires: %lu, now: %lu\n",
+		   queue->napi.state, queue->napi.weight,
+		   skb_queue_len(&queue->tx_queue),
+		   timer_pending(&queue->credit_timeout),
+		   queue->credit_bytes,
+		   queue->credit_usec,
+		   queue->remaining_credit,
+		   queue->credit_timeout.expires,
+		   jiffies);
+
+	dev_queue = netdev_get_tx_queue(queue->vif->dev, queue->id);
+
+	seq_printf(m, "\nRx internal queue: len %u max %u pkts %u %s\n",
+		   queue->rx_queue_len, queue->rx_queue_max,
+		   skb_queue_len(&queue->rx_queue),
+		   netif_tx_queue_stopped(dev_queue) ? "stopped" : "running");
+
+	return 0;
+}
+
+#define XENVIF_KICK_STR "kick"
+#define BUFFER_SIZE     32
+
+static ssize_t
+xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
+		     loff_t *ppos)
+{
+	struct xenvif_queue *queue =
+		((struct seq_file *)filp->private_data)->private;
+	int len;
+	char write[BUFFER_SIZE];
+
+	/* don't allow partial writes and check the length */
+	if (*ppos != 0)
+		return 0;
+	if (count >= sizeof(write))
+		return -ENOSPC;
+
+	len = simple_write_to_buffer(write,
+				     sizeof(write) - 1,
+				     ppos,
+				     buf,
+				     count);
+	if (len < 0)
+		return len;
+
+	write[len] = '\0';
+
+	if (!strncmp(write, XENVIF_KICK_STR, sizeof(XENVIF_KICK_STR) - 1))
+		xenvif_interrupt(0, (void *)queue);
+	else {
+		pr_warn("Unknown command to io_ring_q%d. Available: kick\n",
+			queue->id);
+		count = -EINVAL;
+	}
+	return count;
+}
+
+static int xenvif_dump_open(struct inode *inode, struct file *filp)
+{
+	int ret;
+	void *queue = NULL;
+
+	if (inode->i_private)
+		queue = inode->i_private;
+	ret = single_open(filp, xenvif_read_io_ring, queue);
+	filp->f_mode |= FMODE_PWRITE;
+	return ret;
+}
+
+static const struct file_operations xenvif_dbg_io_ring_ops_fops = {
+	.owner = THIS_MODULE,
+	.open = xenvif_dump_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = xenvif_write_io_ring,
+};
+
+static void xenvif_debugfs_addif(struct xenvif *vif)
+{
+	struct dentry *pfile;
+	int i;
+
+	if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+		return;
+
+	vif->xenvif_dbg_root = debugfs_create_dir(vif->dev->name,
+						  xen_netback_dbg_root);
+	if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root)) {
+		for (i = 0; i < vif->num_queues; ++i) {
+			char filename[sizeof("io_ring_q") + 4];
+
+			snprintf(filename, sizeof(filename), "io_ring_q%d", i);
+			pfile = debugfs_create_file(filename,
+						    S_IRUSR | S_IWUSR,
+						    vif->xenvif_dbg_root,
+						    &vif->queues[i],
+						    &xenvif_dbg_io_ring_ops_fops);
+			if (IS_ERR_OR_NULL(pfile))
+				pr_warn("Creation of io_ring file returned %ld!\n",
+					PTR_ERR(pfile));
+		}
+	} else
+		netdev_warn(vif->dev,
+			    "Creation of vif debugfs dir returned %ld!\n",
+			    PTR_ERR(vif->xenvif_dbg_root));
+}
+
+static void xenvif_debugfs_delif(struct xenvif *vif)
+{
+	if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+		return;
+
+	if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root))
+		debugfs_remove_recursive(vif->xenvif_dbg_root);
+	vif->xenvif_dbg_root = NULL;
+}
+#endif /* CONFIG_DEBUG_FS */
+
+static int netback_remove(struct xenbus_device *dev)
+{
+	struct backend_info *be = dev_get_drvdata(&dev->dev);
+
+	set_backend_state(be, XenbusStateClosed);
+
+	unregister_hotplug_status_watch(be);
+	if (be->vif) {
+		kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
+		xen_unregister_watchers(be->vif);
+		xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
+		xenvif_free(be->vif);
+		be->vif = NULL;
+	}
+	kfree(be->hotplug_script);
+	kfree(be);
+	dev_set_drvdata(&dev->dev, NULL);
+	return 0;
+}
+
+
+/**
+ * Entry point to this code when a new device is created.  Allocate the basic
+ * structures and switch to InitWait.
+ */
+static int netback_probe(struct xenbus_device *dev,
+			 const struct xenbus_device_id *id)
+{
+	const char *message;
+	struct xenbus_transaction xbt;
+	int err;
+	int sg;
+	const char *script;
+	struct backend_info *be = kzalloc(sizeof(struct backend_info),
+					  GFP_KERNEL);
+	if (!be) {
+		xenbus_dev_fatal(dev, -ENOMEM,
+				 "allocating backend structure");
+		return -ENOMEM;
+	}
+
+	be->dev = dev;
+	dev_set_drvdata(&dev->dev, be);
+
+	sg = 1;
+
+	do {
+		err = xenbus_transaction_start(&xbt);
+		if (err) {
+			xenbus_dev_fatal(dev, err, "starting transaction");
+			goto fail;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-sg", "%d", sg);
+		if (err) {
+			message = "writing feature-sg";
+			goto abort_transaction;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv4",
+				    "%d", sg);
+		if (err) {
+			message = "writing feature-gso-tcpv4";
+			goto abort_transaction;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6",
+				    "%d", sg);
+		if (err) {
+			message = "writing feature-gso-tcpv6";
+			goto abort_transaction;
+		}
+
+		/* We support partial checksum setup for IPv6 packets */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-ipv6-csum-offload",
+				    "%d", 1);
+		if (err) {
+			message = "writing feature-ipv6-csum-offload";
+			goto abort_transaction;
+		}
+
+		/* We support rx-copy path. */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-rx-copy", "%d", 1);
+		if (err) {
+			message = "writing feature-rx-copy";
+			goto abort_transaction;
+		}
+
+		/*
+		 * We don't support rx-flip path (except old guests who don't
+		 * grok this feature flag).
+		 */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-rx-flip", "%d", 0);
+		if (err) {
+			message = "writing feature-rx-flip";
+			goto abort_transaction;
+		}
+
+		err = xenbus_transaction_end(xbt, 0);
+	} while (err == -EAGAIN);
+
+	if (err) {
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto fail;
+	}
+
+	/*
+	 * Split event channels support, this is optional so it is not
+	 * put inside the above loop.
+	 */
+	err = xenbus_printf(XBT_NIL, dev->nodename,
+			    "feature-split-event-channels",
+			    "%u", separate_tx_rx_irq);
+	if (err)
+		pr_debug("Error writing feature-split-event-channels\n");
+
+	/* Multi-queue support: This is an optional feature. */
+	err = xenbus_printf(XBT_NIL, dev->nodename,
+			    "multi-queue-max-queues", "%u", xenvif_max_queues);
+	if (err)
+		pr_debug("Error writing multi-queue-max-queues\n");
+
+	script = xenbus_read(XBT_NIL, dev->nodename, "script", NULL);
+	if (IS_ERR(script)) {
+		err = PTR_ERR(script);
+		xenbus_dev_fatal(dev, err, "reading script");
+		goto fail;
+	}
+
+	be->hotplug_script = script;
+
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto fail;
+
+	be->state = XenbusStateInitWait;
+
+	/* This kicks hotplug scripts, so do it immediately. */
+	err = backend_create_xenvif(be);
+	if (err)
+		goto fail;
+
+	return 0;
+
+abort_transaction:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, err, "%s", message);
+fail:
+	pr_debug("failed\n");
+	netback_remove(dev);
+	return err;
+}
+
+
+/*
+ * Handle the creation of the hotplug script environment.  We add the script
+ * and vif variables to the environment, for the benefit of the vif-* hotplug
+ * scripts.
+ */
+static int netback_uevent(struct xenbus_device *xdev,
+			  struct kobj_uevent_env *env)
+{
+	struct backend_info *be = dev_get_drvdata(&xdev->dev);
+
+	if (!be)
+		return 0;
+
+	if (add_uevent_var(env, "script=%s", be->hotplug_script))
+		return -ENOMEM;
+
+	if (!be->vif)
+		return 0;
+
+	return add_uevent_var(env, "vif=%s", be->vif->dev->name);
+}
+
+
+static int backend_create_xenvif(struct backend_info *be)
+{
+	int err;
+	long handle;
+	struct xenbus_device *dev = be->dev;
+	struct xenvif *vif;
+
+	if (be->vif != NULL)
+		return 0;
+
+	err = xenbus_scanf(XBT_NIL, dev->nodename, "handle", "%li", &handle);
+	if (err != 1) {
+		xenbus_dev_fatal(dev, err, "reading handle");
+		return (err < 0) ? err : -EINVAL;
+	}
+
+	vif = xenvif_alloc(&dev->dev, dev->otherend_id, handle);
+	if (IS_ERR(vif)) {
+		err = PTR_ERR(vif);
+		xenbus_dev_fatal(dev, err, "creating interface");
+		return err;
+	}
+	be->vif = vif;
+
+	kobject_uevent(&dev->dev.kobj, KOBJ_ONLINE);
+	return 0;
+}
+
+static void backend_disconnect(struct backend_info *be)
+{
+	if (be->vif) {
+		xen_unregister_watchers(be->vif);
+#ifdef CONFIG_DEBUG_FS
+		xenvif_debugfs_delif(be->vif);
+#endif /* CONFIG_DEBUG_FS */
+		xenvif_disconnect(be->vif);
+	}
+}
+
+static void backend_connect(struct backend_info *be)
+{
+	if (be->vif)
+		connect(be);
+}
+
+static inline void backend_switch_state(struct backend_info *be,
+					enum xenbus_state state)
+{
+	struct xenbus_device *dev = be->dev;
+
+	pr_debug("%s -> %s\n", dev->nodename, xenbus_strstate(state));
+	be->state = state;
+
+	/* If we are waiting for a hotplug script then defer the
+	 * actual xenbus state change.
+	 */
+	if (!be->have_hotplug_status_watch)
+		xenbus_switch_state(dev, state);
+}
+
+/* Handle backend state transitions:
+ *
+ * The backend state starts in InitWait and the following transitions are
+ * allowed.
+ *
+ * InitWait -> Connected
+ *
+ *    ^    \         |
+ *    |     \        |
+ *    |      \       |
+ *    |       \      |
+ *    |        \     |
+ *    |         \    |
+ *    |          V   V
+ *
+ *  Closed  <-> Closing
+ *
+ * The state argument specifies the eventual state of the backend and the
+ * function transitions to that state via the shortest path.
+ */
+static void set_backend_state(struct backend_info *be,
+			      enum xenbus_state state)
+{
+	while (be->state != state) {
+		switch (be->state) {
+		case XenbusStateClosed:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+				pr_info("%s: prepare for reconnect\n",
+					be->dev->nodename);
+				backend_switch_state(be, XenbusStateInitWait);
+				break;
+			case XenbusStateClosing:
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateInitWait:
+			switch (state) {
+			case XenbusStateConnected:
+				backend_connect(be);
+				backend_switch_state(be, XenbusStateConnected);
+				break;
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateConnected:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				backend_disconnect(be);
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateClosing:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+			case XenbusStateClosed:
+				backend_switch_state(be, XenbusStateClosed);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		default:
+			BUG();
+		}
+	}
+}
+
+/**
+ * Callback received when the frontend's state changes.
+ */
+static void frontend_changed(struct xenbus_device *dev,
+			     enum xenbus_state frontend_state)
+{
+	struct backend_info *be = dev_get_drvdata(&dev->dev);
+
+	pr_debug("%s -> %s\n", dev->otherend, xenbus_strstate(frontend_state));
+
+	be->frontend_state = frontend_state;
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		set_backend_state(be, XenbusStateInitWait);
+		break;
+
+	case XenbusStateInitialised:
+		break;
+
+	case XenbusStateConnected:
+		set_backend_state(be, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		set_backend_state(be, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		set_backend_state(be, XenbusStateClosed);
+		if (xenbus_dev_is_online(dev))
+			break;
+		/* fall through if not online */
+	case XenbusStateUnknown:
+		set_backend_state(be, XenbusStateClosed);
+		device_unregister(&dev->dev);
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+				 frontend_state);
+		break;
+	}
+}
+
+
+static void xen_net_read_rate(struct xenbus_device *dev,
+			      unsigned long *bytes, unsigned long *usec)
+{
+	char *s, *e;
+	unsigned long b, u;
+	char *ratestr;
+
+	/* Default to unlimited bandwidth. */
+	*bytes = ~0UL;
+	*usec = 0;
+
+	ratestr = xenbus_read(XBT_NIL, dev->nodename, "rate", NULL);
+	if (IS_ERR(ratestr))
+		return;
+
+	s = ratestr;
+	b = simple_strtoul(s, &e, 10);
+	if ((s == e) || (*e != ','))
+		goto fail;
+
+	s = e + 1;
+	u = simple_strtoul(s, &e, 10);
+	if ((s == e) || (*e != '\0'))
+		goto fail;
+
+	*bytes = b;
+	*usec = u;
+
+	kfree(ratestr);
+	return;
+
+ fail:
+	pr_warn("Failed to parse network rate limit. Traffic unlimited.\n");
+	kfree(ratestr);
+}
+
+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 void xen_net_rate_changed(struct xenbus_watch *watch,
+				const char **vec, unsigned int len)
+{
+	struct xenvif *vif = container_of(watch, struct xenvif, credit_watch);
+	struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
+	unsigned long   credit_bytes;
+	unsigned long   credit_usec;
+	unsigned int queue_index;
+
+	xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+	for (queue_index = 0; queue_index < vif->num_queues; queue_index++) {
+		struct xenvif_queue *queue = &vif->queues[queue_index];
+
+		queue->credit_bytes = credit_bytes;
+		queue->credit_usec = credit_usec;
+		if (!mod_timer_pending(&queue->credit_timeout, jiffies) &&
+			queue->remaining_credit > queue->credit_bytes) {
+			queue->remaining_credit = queue->credit_bytes;
+		}
+	}
+}
+
+static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
+{
+	int err = 0;
+	char *node;
+	unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");
+
+	if (vif->credit_watch.node)
+		return -EADDRINUSE;
+
+	node = kmalloc(maxlen, GFP_KERNEL);
+	if (!node)
+		return -ENOMEM;
+	snprintf(node, maxlen, "%s/rate", dev->nodename);
+	vif->credit_watch.node = node;
+	vif->credit_watch.callback = xen_net_rate_changed;
+	err = register_xenbus_watch(&vif->credit_watch);
+	if (err) {
+		pr_err("Failed to set watcher %s\n", vif->credit_watch.node);
+		kfree(node);
+		vif->credit_watch.node = NULL;
+		vif->credit_watch.callback = NULL;
+	}
+	return err;
+}
+
+static void xen_unregister_watchers(struct xenvif *vif)
+{
+	if (vif->credit_watch.node) {
+		unregister_xenbus_watch(&vif->credit_watch);
+		kfree(vif->credit_watch.node);
+		vif->credit_watch.node = NULL;
+	}
+}
+
+static void unregister_hotplug_status_watch(struct backend_info *be)
+{
+	if (be->have_hotplug_status_watch) {
+		unregister_xenbus_watch(&be->hotplug_status_watch);
+		kfree(be->hotplug_status_watch.node);
+	}
+	be->have_hotplug_status_watch = 0;
+}
+
+static void hotplug_status_changed(struct xenbus_watch *watch,
+				   const char **vec,
+				   unsigned int vec_size)
+{
+	struct backend_info *be = container_of(watch,
+					       struct backend_info,
+					       hotplug_status_watch);
+	char *str;
+	unsigned int len;
+
+	str = xenbus_read(XBT_NIL, be->dev->nodename, "hotplug-status", &len);
+	if (IS_ERR(str))
+		return;
+	if (len == sizeof("connected")-1 && !memcmp(str, "connected", len)) {
+		/* Complete any pending state change */
+		xenbus_switch_state(be->dev, be->state);
+
+		/* Not interested in this watch anymore. */
+		unregister_hotplug_status_watch(be);
+	}
+	kfree(str);
+}
+
+static void connect(struct backend_info *be)
+{
+	int err;
+	struct xenbus_device *dev = be->dev;
+	unsigned long credit_bytes, credit_usec;
+	unsigned int queue_index;
+	unsigned int requested_num_queues;
+	struct xenvif_queue *queue;
+
+	/* Check whether the frontend requested multiple queues
+	 * and read the number requested.
+	 */
+	err = xenbus_scanf(XBT_NIL, dev->otherend,
+			   "multi-queue-num-queues",
+			   "%u", &requested_num_queues);
+	if (err < 0) {
+		requested_num_queues = 1; /* Fall back to single queue */
+	} else if (requested_num_queues > xenvif_max_queues) {
+		/* buggy or malicious guest */
+		xenbus_dev_fatal(dev, err,
+				 "guest requested %u queues, exceeding the maximum of %u.",
+				 requested_num_queues, xenvif_max_queues);
+		return;
+	}
+
+	err = xen_net_read_mac(dev, be->vif->fe_dev_addr);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
+		return;
+	}
+
+	xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+	xen_unregister_watchers(be->vif);
+	xen_register_watchers(dev, be->vif);
+	read_xenbus_vif_flags(be);
+
+	/* Use the number of queues requested by the frontend */
+	be->vif->queues = vzalloc(requested_num_queues *
+				  sizeof(struct xenvif_queue));
+	be->vif->num_queues = requested_num_queues;
+	be->vif->stalled_queues = requested_num_queues;
+
+	for (queue_index = 0; queue_index < requested_num_queues; ++queue_index) {
+		queue = &be->vif->queues[queue_index];
+		queue->vif = be->vif;
+		queue->id = queue_index;
+		snprintf(queue->name, sizeof(queue->name), "%s-q%u",
+				be->vif->dev->name, queue->id);
+
+		err = xenvif_init_queue(queue);
+		if (err) {
+			/* xenvif_init_queue() cleans up after itself on
+			 * failure, but we need to clean up any previously
+			 * initialised queues. Set num_queues to i so that
+			 * earlier queues can be destroyed using the regular
+			 * disconnect logic.
+			 */
+			be->vif->num_queues = queue_index;
+			goto err;
+		}
+
+		queue->credit_bytes = credit_bytes;
+		queue->remaining_credit = credit_bytes;
+		queue->credit_usec = credit_usec;
+
+		err = connect_rings(be, queue);
+		if (err) {
+			/* connect_rings() cleans up after itself on failure,
+			 * but we need to clean up after xenvif_init_queue() here,
+			 * and also clean up any previously initialised queues.
+			 */
+			xenvif_deinit_queue(queue);
+			be->vif->num_queues = queue_index;
+			goto err;
+		}
+	}
+
+#ifdef CONFIG_DEBUG_FS
+	xenvif_debugfs_addif(be->vif);
+#endif /* CONFIG_DEBUG_FS */
+
+	/* Initialisation completed, tell core driver the number of
+	 * active queues.
+	 */
+	rtnl_lock();
+	netif_set_real_num_tx_queues(be->vif->dev, requested_num_queues);
+	netif_set_real_num_rx_queues(be->vif->dev, requested_num_queues);
+	rtnl_unlock();
+
+	xenvif_carrier_on(be->vif);
+
+	unregister_hotplug_status_watch(be);
+	err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch,
+				   hotplug_status_changed,
+				   "%s/%s", dev->nodename, "hotplug-status");
+	if (!err)
+		be->have_hotplug_status_watch = 1;
+
+	netif_tx_wake_all_queues(be->vif->dev);
+
+	return;
+
+err:
+	if (be->vif->num_queues > 0)
+		xenvif_disconnect(be->vif); /* Clean up existing queues */
+	vfree(be->vif->queues);
+	be->vif->queues = NULL;
+	be->vif->num_queues = 0;
+	return;
+}
+
+
+static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
+{
+	struct xenbus_device *dev = be->dev;
+	unsigned int num_queues = queue->vif->num_queues;
+	unsigned long tx_ring_ref, rx_ring_ref;
+	unsigned int tx_evtchn, rx_evtchn;
+	int err;
+	char *xspath;
+	size_t xspathsize;
+	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
+
+	/* If the frontend requested 1 queue, or we have fallen back
+	 * to single queue due to lack of frontend support for multi-
+	 * queue, expect the remaining XenStore keys in the toplevel
+	 * directory. Otherwise, expect them in a subdirectory called
+	 * queue-N.
+	 */
+	if (num_queues == 1) {
+		xspath = kzalloc(strlen(dev->otherend) + 1, GFP_KERNEL);
+		if (!xspath) {
+			xenbus_dev_fatal(dev, -ENOMEM,
+					 "reading ring references");
+			return -ENOMEM;
+		}
+		strcpy(xspath, dev->otherend);
+	} else {
+		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
+		xspath = kzalloc(xspathsize, GFP_KERNEL);
+		if (!xspath) {
+			xenbus_dev_fatal(dev, -ENOMEM,
+					 "reading ring references");
+			return -ENOMEM;
+		}
+		snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend,
+			 queue->id);
+	}
+
+	err = xenbus_gather(XBT_NIL, xspath,
+			    "tx-ring-ref", "%lu", &tx_ring_ref,
+			    "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "reading %s/ring-ref",
+				 xspath);
+		goto err;
+	}
+
+	/* Try split event channels first, then single event channel. */
+	err = xenbus_gather(XBT_NIL, xspath,
+			    "event-channel-tx", "%u", &tx_evtchn,
+			    "event-channel-rx", "%u", &rx_evtchn, NULL);
+	if (err < 0) {
+		err = xenbus_scanf(XBT_NIL, xspath,
+				   "event-channel", "%u", &tx_evtchn);
+		if (err < 0) {
+			xenbus_dev_fatal(dev, err,
+					 "reading %s/event-channel(-tx/rx)",
+					 xspath);
+			goto err;
+		}
+		rx_evtchn = tx_evtchn;
+	}
+
+	/* Map the shared frame, irq etc. */
+	err = xenvif_connect(queue, tx_ring_ref, rx_ring_ref,
+			     tx_evtchn, rx_evtchn);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "mapping shared-frames %lu/%lu port tx %u rx %u",
+				 tx_ring_ref, rx_ring_ref,
+				 tx_evtchn, rx_evtchn);
+		goto err;
+	}
+
+	err = 0;
+err: /* Regular return falls through with err == 0 */
+	kfree(xspath);
+	return err;
+}
+
+static int read_xenbus_vif_flags(struct backend_info *be)
+{
+	struct xenvif *vif = be->vif;
+	struct xenbus_device *dev = be->dev;
+	unsigned int rx_copy;
+	int err, val;
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
+			   &rx_copy);
+	if (err == -ENOENT) {
+		err = 0;
+		rx_copy = 0;
+	}
+	if (err < 0) {
+		xenbus_dev_fatal(dev, err, "reading %s/request-rx-copy",
+				 dev->otherend);
+		return err;
+	}
+	if (!rx_copy)
+		return -EOPNOTSUPP;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend,
+			 "feature-rx-notify", "%d", &val) < 0)
+		val = 0;
+	if (!val) {
+		/* - Reduce drain timeout to poll more frequently for
+		 *   Rx requests.
+		 * - Disable Rx stall detection.
+		 */
+		be->vif->drain_timeout = msecs_to_jiffies(30);
+		be->vif->stall_timeout = 0;
+	}
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->can_sg = !!val;
+
+	vif->gso_mask = 0;
+	vif->gso_prefix_mask = 0;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV4);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4-prefix",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV4);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV6);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6-prefix",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV6);
+
+	if (vif->gso_mask & vif->gso_prefix_mask) {
+		xenbus_dev_fatal(dev, err,
+				 "%s: gso and gso prefix flags are not "
+				 "mutually exclusive",
+				 dev->otherend);
+		return -EOPNOTSUPP;
+	}
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->ip_csum = !val;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->ipv6_csum = !!val;
+
+	return 0;
+}
+
+static const struct xenbus_device_id netback_ids[] = {
+	{ "vif" },
+	{ "" }
+};
+
+static struct xenbus_driver netback_driver = {
+	.ids = netback_ids,
+	.probe = netback_probe,
+	.remove = netback_remove,
+	.uevent = netback_uevent,
+	.otherend_changed = frontend_changed,
+};
+
+int xenvif_xenbus_init(void)
+{
+	return xenbus_register_backend(&netback_driver);
+}
+
+void xenvif_xenbus_fini(void)
+{
+	return xenbus_unregister_driver(&netback_driver);
+}