/*
   * Copyright (c) 2009, Microsoft Corporation.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope 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, write to the Free Software Foundation, Inc., 59 Temple
   * Place - Suite 330, Boston, MA 02111-1307 USA.
   *
   * Authors:
   *   Haiyang Zhang <haiyangz@microsoft.com>
   *   Hank Janssen  <hjanssen@microsoft.com>
   */
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/wait.h>
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/list.h>
  #include <linux/module.h>
  #include <linux/completion.h>
  #include <linux/delay.h>
  #include <linux/hyperv.h>
  
  #include "hyperv_vmbus.h"
  
  static void init_vp_index(struct vmbus_channel *channel,
  			  const uuid_le *type_guid);
  
  /**
   * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
   * @icmsghdrp: Pointer to msg header structure
   * @icmsg_negotiate: Pointer to negotiate message structure
   * @buf: Raw buffer channel data
   *
   * @icmsghdrp is of type &struct icmsg_hdr.
   * @negop is of type &struct icmsg_negotiate.
   * Set up and fill in default negotiate response message.
   *
   * The fw_version specifies the  framework version that
   * we can support and srv_version specifies the service
   * version we can support.
   *
   * Mainly used by Hyper-V drivers.
   */
  bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
  				struct icmsg_negotiate *negop, u8 *buf,
  				int fw_version, int srv_version)
  {
  	int icframe_major, icframe_minor;
  	int icmsg_major, icmsg_minor;
  	int fw_major, fw_minor;
  	int srv_major, srv_minor;
  	int i;
  	bool found_match = false;
  
  	icmsghdrp->icmsgsize = 0x10;
  	fw_major = (fw_version >> 16);
  	fw_minor = (fw_version & 0xFFFF);
  
  	srv_major = (srv_version >> 16);
  	srv_minor = (srv_version & 0xFFFF);
  
  	negop = (struct icmsg_negotiate *)&buf[
  		sizeof(struct vmbuspipe_hdr) +
  		sizeof(struct icmsg_hdr)];
  
  	icframe_major = negop->icframe_vercnt;
  	icframe_minor = 0;
  
  	icmsg_major = negop->icmsg_vercnt;
  	icmsg_minor = 0;
  
  	/*
  	 * Select the framework version number we will
  	 * support.
  	 */
  
  	for (i = 0; i < negop->icframe_vercnt; i++) {
  		if ((negop->icversion_data[i].major == fw_major) &&
  		   (negop->icversion_data[i].minor == fw_minor)) {
  			icframe_major = negop->icversion_data[i].major;
  			icframe_minor = negop->icversion_data[i].minor;
  			found_match = true;
  		}
  	}
  
  	if (!found_match)
  		goto fw_error;
  
  	found_match = false;
  
  	for (i = negop->icframe_vercnt;
  		 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
  		if ((negop->icversion_data[i].major == srv_major) &&
  		   (negop->icversion_data[i].minor == srv_minor)) {
  			icmsg_major = negop->icversion_data[i].major;
  			icmsg_minor = negop->icversion_data[i].minor;
  			found_match = true;
  		}
  	}
  
  	/*
  	 * Respond with the framework and service
  	 * version numbers we can support.
  	 */
  
  fw_error:
  	if (!found_match) {
  		negop->icframe_vercnt = 0;
  		negop->icmsg_vercnt = 0;
  	} else {
  		negop->icframe_vercnt = 1;
  		negop->icmsg_vercnt = 1;
  	}
  
  	negop->icversion_data[0].major = icframe_major;
  	negop->icversion_data[0].minor = icframe_minor;
  	negop->icversion_data[1].major = icmsg_major;
  	negop->icversion_data[1].minor = icmsg_minor;
  	return found_match;
  }
  
  EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
  
  /*
   * alloc_channel - Allocate and initialize a vmbus channel object
   */
  static struct vmbus_channel *alloc_channel(void)
  {
  	static atomic_t chan_num = ATOMIC_INIT(0);
  	struct vmbus_channel *channel;
  
  	channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
  	if (!channel)
  		return NULL;
  
  	channel->id = atomic_inc_return(&chan_num);
  	spin_lock_init(&channel->inbound_lock);
  	spin_lock_init(&channel->lock);
  
  	INIT_LIST_HEAD(&channel->sc_list);
  	INIT_LIST_HEAD(&channel->percpu_list);
  
  	return channel;
  }
  
  /*
   * free_channel - Release the resources used by the vmbus channel object
   */
  static void free_channel(struct vmbus_channel *channel)
  {
  	kfree(channel);
  }
  
  static void percpu_channel_enq(void *arg)
  {
  	struct vmbus_channel *channel = arg;
  	int cpu = smp_processor_id();
  
  	list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
  }
  
  static void percpu_channel_deq(void *arg)
  {
  	struct vmbus_channel *channel = arg;
  
  	list_del(&channel->percpu_list);
  }
  
  
  void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
  {
  	struct vmbus_channel_relid_released msg;
  	unsigned long flags;
  	struct vmbus_channel *primary_channel;
  
  	memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
  	msg.child_relid = relid;
  	msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
  	vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
  
  	if (channel == NULL)
  		return;
  
  	BUG_ON(!channel->rescind);
  
  	if (channel->target_cpu != get_cpu()) {
  		put_cpu();
  		smp_call_function_single(channel->target_cpu,
  					 percpu_channel_deq, channel, true);
  	} else {
  		percpu_channel_deq(channel);
  		put_cpu();
  	}
  
  	if (channel->primary_channel == NULL) {
  		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
  		list_del(&channel->listentry);
  		spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
  
  		primary_channel = channel;
  	} else {
  		primary_channel = channel->primary_channel;
  		spin_lock_irqsave(&primary_channel->lock, flags);
  		list_del(&channel->sc_list);
  		primary_channel->num_sc--;
  		spin_unlock_irqrestore(&primary_channel->lock, flags);
  	}
  
  	/*
  	 * We need to free the bit for init_vp_index() to work in the case
  	 * of sub-channel, when we reload drivers like hv_netvsc.
  	 */
  	cpumask_clear_cpu(channel->target_cpu,
  			  &primary_channel->alloced_cpus_in_node);
  
  	free_channel(channel);
  }
  
  void vmbus_free_channels(void)
  {
  	struct vmbus_channel *channel, *tmp;
  
  	list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
  		listentry) {
  		/* hv_process_channel_removal() needs this */
  		channel->rescind = true;
  
  		vmbus_device_unregister(channel->device_obj);
  	}
  }
  
  /*
   * vmbus_process_offer - Process the offer by creating a channel/device
   * associated with this offer
   */
  static void vmbus_process_offer(struct vmbus_channel *newchannel)
  {
  	struct vmbus_channel *channel;
  	bool fnew = true;
  	unsigned long flags;
  
  	/* Make sure this is a new offer */
  	spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
  
  	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
  		if (!uuid_le_cmp(channel->offermsg.offer.if_type,
  			newchannel->offermsg.offer.if_type) &&
  			!uuid_le_cmp(channel->offermsg.offer.if_instance,
  				newchannel->offermsg.offer.if_instance)) {
  			fnew = false;
  			break;
  		}
  	}
  
  	if (fnew)
  		list_add_tail(&newchannel->listentry,
  			      &vmbus_connection.chn_list);
  
  	spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
  
  	if (!fnew) {
  		/*
  		 * Check to see if this is a sub-channel.
  		 */
  		if (newchannel->offermsg.offer.sub_channel_index != 0) {
  			/*
  			 * Process the sub-channel.
  			 */
  			newchannel->primary_channel = channel;
  			spin_lock_irqsave(&channel->lock, flags);
  			list_add_tail(&newchannel->sc_list, &channel->sc_list);
  			channel->num_sc++;
  			spin_unlock_irqrestore(&channel->lock, flags);
  		} else
  			goto err_free_chan;
  	}
  
  	init_vp_index(newchannel, &newchannel->offermsg.offer.if_type);
  
  	if (newchannel->target_cpu != get_cpu()) {
  		put_cpu();
  		smp_call_function_single(newchannel->target_cpu,
  					 percpu_channel_enq,
  					 newchannel, true);
  	} else {
  		percpu_channel_enq(newchannel);
  		put_cpu();
  	}
  
  	/*
  	 * This state is used to indicate a successful open
  	 * so that when we do close the channel normally, we
  	 * can cleanup properly
  	 */
  	newchannel->state = CHANNEL_OPEN_STATE;
  
  	if (!fnew) {
  		if (channel->sc_creation_callback != NULL)
  			channel->sc_creation_callback(newchannel);
  		return;
  	}
  
  	/*
  	 * Start the process of binding this offer to the driver
  	 * We need to set the DeviceObject field before calling
  	 * vmbus_child_dev_add()
  	 */
  	newchannel->device_obj = vmbus_device_create(
  		&newchannel->offermsg.offer.if_type,
  		&newchannel->offermsg.offer.if_instance,
  		newchannel);
  	if (!newchannel->device_obj)
  		goto err_deq_chan;
  
  	/*
  	 * Add the new device to the bus. This will kick off device-driver
  	 * binding which eventually invokes the device driver's AddDevice()
  	 * method.
  	 */
  	if (vmbus_device_register(newchannel->device_obj) != 0) {
  		pr_err("unable to add child device object (relid %d)
  ",
  			newchannel->offermsg.child_relid);
  		kfree(newchannel->device_obj);
  		goto err_deq_chan;
  	}
  	return;
  
  err_deq_chan:
  	spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
  	list_del(&newchannel->listentry);
  	spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
  
  	if (newchannel->target_cpu != get_cpu()) {
  		put_cpu();
  		smp_call_function_single(newchannel->target_cpu,
  					 percpu_channel_deq, newchannel, true);
  	} else {
  		percpu_channel_deq(newchannel);
  		put_cpu();
  	}
  
  err_free_chan:
  	free_channel(newchannel);
  }
  
  enum {
  	IDE = 0,
  	SCSI,
  	NIC,
  	ND_NIC,
  	MAX_PERF_CHN,
  };
  
  /*
   * This is an array of device_ids (device types) that are performance critical.
   * We attempt to distribute the interrupt load for these devices across
   * all available CPUs.
   */
  static const struct hv_vmbus_device_id hp_devs[] = {
  	/* IDE */
  	{ HV_IDE_GUID, },
  	/* Storage - SCSI */
  	{ HV_SCSI_GUID, },
  	/* Network */
  	{ HV_NIC_GUID, },
  	/* NetworkDirect Guest RDMA */
  	{ HV_ND_GUID, },
  };
  
  
  /*
   * We use this state to statically distribute the channel interrupt load.
   */
  static int next_numa_node_id;
  
  /*
   * Starting with Win8, we can statically distribute the incoming
   * channel interrupt load by binding a channel to VCPU.
   * We do this in a hierarchical fashion:
   * First distribute the primary channels across available NUMA nodes
   * and then distribute the subchannels amongst the CPUs in the NUMA
   * node assigned to the primary channel.
   *
   * For pre-win8 hosts or non-performance critical channels we assign the
   * first CPU in the first NUMA node.
   */
  static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_guid)
  {
  	u32 cur_cpu;
  	int i;
  	bool perf_chn = false;
  	struct vmbus_channel *primary = channel->primary_channel;
  	int next_node;
  	struct cpumask available_mask;
  	struct cpumask *alloced_mask;
  
  	for (i = IDE; i < MAX_PERF_CHN; i++) {
  		if (!memcmp(type_guid->b, hp_devs[i].guid,
  				 sizeof(uuid_le))) {
  			perf_chn = true;
  			break;
  		}
  	}
  	if ((vmbus_proto_version == VERSION_WS2008) ||
  	    (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
  		/*
  		 * Prior to win8, all channel interrupts are
  		 * delivered on cpu 0.
  		 * Also if the channel is not a performance critical
  		 * channel, bind it to cpu 0.
  		 */
  		channel->numa_node = 0;
  		channel->target_cpu = 0;
  		channel->target_vp = hv_context.vp_index[0];
  		return;
  	}
  
  	/*
  	 * We distribute primary channels evenly across all the available
  	 * NUMA nodes and within the assigned NUMA node we will assign the
  	 * first available CPU to the primary channel.
  	 * The sub-channels will be assigned to the CPUs available in the
  	 * NUMA node evenly.
  	 */
  	if (!primary) {
  		while (true) {
  			next_node = next_numa_node_id++;
  			if (next_node == nr_node_ids)
  				next_node = next_numa_node_id = 0;
  			if (cpumask_empty(cpumask_of_node(next_node)))
  				continue;
  			break;
  		}
  		channel->numa_node = next_node;
  		primary = channel;
  	}
  	alloced_mask = &hv_context.hv_numa_map[primary->numa_node];
  
  	if (cpumask_weight(alloced_mask) ==
  	    cpumask_weight(cpumask_of_node(primary->numa_node))) {
  		/*
  		 * We have cycled through all the CPUs in the node;
  		 * reset the alloced map.
  		 */
  		cpumask_clear(alloced_mask);
  	}
  
  	cpumask_xor(&available_mask, alloced_mask,
  		    cpumask_of_node(primary->numa_node));
  
  	cur_cpu = -1;
  
  	/*
  	 * Normally Hyper-V host doesn't create more subchannels than there
  	 * are VCPUs on the node but it is possible when not all present VCPUs
  	 * on the node are initialized by guest. Clear the alloced_cpus_in_node
  	 * to start over.
  	 */
  	if (cpumask_equal(&primary->alloced_cpus_in_node,
  			  cpumask_of_node(primary->numa_node)))
  		cpumask_clear(&primary->alloced_cpus_in_node);
  
  	while (true) {
  		cur_cpu = cpumask_next(cur_cpu, &available_mask);
  		if (cur_cpu >= nr_cpu_ids) {
  			cur_cpu = -1;
  			cpumask_copy(&available_mask,
  				     cpumask_of_node(primary->numa_node));
  			continue;
  		}
  
  		/*
  		 * NOTE: in the case of sub-channel, we clear the sub-channel
  		 * related bit(s) in primary->alloced_cpus_in_node in
  		 * hv_process_channel_removal(), so when we reload drivers
  		 * like hv_netvsc in SMP guest, here we're able to re-allocate
  		 * bit from primary->alloced_cpus_in_node.
  		 */
  		if (!cpumask_test_cpu(cur_cpu,
  				&primary->alloced_cpus_in_node)) {
  			cpumask_set_cpu(cur_cpu,
  					&primary->alloced_cpus_in_node);
  			cpumask_set_cpu(cur_cpu, alloced_mask);
  			break;
  		}
  	}
  
  	channel->target_cpu = cur_cpu;
  	channel->target_vp = hv_context.vp_index[cur_cpu];
  }
  
  static void vmbus_wait_for_unload(void)
  {
  	int cpu = smp_processor_id();
  	void *page_addr = hv_context.synic_message_page[cpu];
  	struct hv_message *msg = (struct hv_message *)page_addr +
  				  VMBUS_MESSAGE_SINT;
  	struct vmbus_channel_message_header *hdr;
  	bool unloaded = false;
  
  	while (1) {
  		if (msg->header.message_type == HVMSG_NONE) {
  			mdelay(10);
  			continue;
  		}
  
  		hdr = (struct vmbus_channel_message_header *)msg->u.payload;
  		if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE)
  			unloaded = true;
  
  		msg->header.message_type = HVMSG_NONE;
  		/*
  		 * header.message_type needs to be written before we do
  		 * wrmsrl() below.
  		 */
  		mb();
  
  		if (msg->header.message_flags.msg_pending)
  			wrmsrl(HV_X64_MSR_EOM, 0);
  
  		if (unloaded)
  			break;
  	}
  }
  
  /*
   * vmbus_unload_response - Handler for the unload response.
   */
  static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
  {
  	/*
  	 * This is a global event; just wakeup the waiting thread.
  	 * Once we successfully unload, we can cleanup the monitor state.
  	 */
  	complete(&vmbus_connection.unload_event);
  }
  
  void vmbus_initiate_unload(void)
  {
  	struct vmbus_channel_message_header hdr;
  
  	/* Pre-Win2012R2 hosts don't support reconnect */
  	if (vmbus_proto_version < VERSION_WIN8_1)
  		return;
  
  	init_completion(&vmbus_connection.unload_event);
  	memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
  	hdr.msgtype = CHANNELMSG_UNLOAD;
  	vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header));
  
  	/*
  	 * vmbus_initiate_unload() is also called on crash and the crash can be
  	 * happening in an interrupt context, where scheduling is impossible.
  	 */
  	if (!in_interrupt())
  		wait_for_completion(&vmbus_connection.unload_event);
  	else
  		vmbus_wait_for_unload();
  }
  
  /*
   * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
   *
   */
  static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_offer_channel *offer;
  	struct vmbus_channel *newchannel;
  
  	offer = (struct vmbus_channel_offer_channel *)hdr;
  
  	/* Allocate the channel object and save this offer. */
  	newchannel = alloc_channel();
  	if (!newchannel) {
  		pr_err("Unable to allocate channel object
  ");
  		return;
  	}
  
  	/*
  	 * By default we setup state to enable batched
  	 * reading. A specific service can choose to
  	 * disable this prior to opening the channel.
  	 */
  	newchannel->batched_reading = true;
  
  	/*
  	 * Setup state for signalling the host.
  	 */
  	newchannel->sig_event = (struct hv_input_signal_event *)
  				(ALIGN((unsigned long)
  				&newchannel->sig_buf,
  				HV_HYPERCALL_PARAM_ALIGN));
  
  	newchannel->sig_event->connectionid.asu32 = 0;
  	newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
  	newchannel->sig_event->flag_number = 0;
  	newchannel->sig_event->rsvdz = 0;
  
  	if (vmbus_proto_version != VERSION_WS2008) {
  		newchannel->is_dedicated_interrupt =
  				(offer->is_dedicated_interrupt != 0);
  		newchannel->sig_event->connectionid.u.id =
  				offer->connection_id;
  	}
  
  	memcpy(&newchannel->offermsg, offer,
  	       sizeof(struct vmbus_channel_offer_channel));
  	newchannel->monitor_grp = (u8)offer->monitorid / 32;
  	newchannel->monitor_bit = (u8)offer->monitorid % 32;
  
  	vmbus_process_offer(newchannel);
  }
  
  /*
   * vmbus_onoffer_rescind - Rescind offer handler.
   *
   * We queue a work item to process this offer synchronously
   */
  static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_rescind_offer *rescind;
  	struct vmbus_channel *channel;
  	unsigned long flags;
  	struct device *dev;
  
  	rescind = (struct vmbus_channel_rescind_offer *)hdr;
  	channel = relid2channel(rescind->child_relid);
  
  	if (channel == NULL) {
  		hv_process_channel_removal(NULL, rescind->child_relid);
  		return;
  	}
  
  	spin_lock_irqsave(&channel->lock, flags);
  	channel->rescind = true;
  	spin_unlock_irqrestore(&channel->lock, flags);
  
  	if (channel->device_obj) {
  		/*
  		 * We will have to unregister this device from the
  		 * driver core.
  		 */
  		dev = get_device(&channel->device_obj->device);
  		if (dev) {
  			vmbus_device_unregister(channel->device_obj);
  			put_device(dev);
  		}
  	} else {
  		hv_process_channel_removal(channel,
  			channel->offermsg.child_relid);
  	}
  }
  
  /*
   * vmbus_onoffers_delivered -
   * This is invoked when all offers have been delivered.
   *
   * Nothing to do here.
   */
  static void vmbus_onoffers_delivered(
  			struct vmbus_channel_message_header *hdr)
  {
  }
  
  /*
   * vmbus_onopen_result - Open result handler.
   *
   * This is invoked when we received a response to our channel open request.
   * Find the matching request, copy the response and signal the requesting
   * thread.
   */
  static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_open_result *result;
  	struct vmbus_channel_msginfo *msginfo;
  	struct vmbus_channel_message_header *requestheader;
  	struct vmbus_channel_open_channel *openmsg;
  	unsigned long flags;
  
  	result = (struct vmbus_channel_open_result *)hdr;
  
  	/*
  	 * Find the open msg, copy the result and signal/unblock the wait event
  	 */
  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
  
  	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
  				msglistentry) {
  		requestheader =
  			(struct vmbus_channel_message_header *)msginfo->msg;
  
  		if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
  			openmsg =
  			(struct vmbus_channel_open_channel *)msginfo->msg;
  			if (openmsg->child_relid == result->child_relid &&
  			    openmsg->openid == result->openid) {
  				memcpy(&msginfo->response.open_result,
  				       result,
  				       sizeof(
  					struct vmbus_channel_open_result));
  				complete(&msginfo->waitevent);
  				break;
  			}
  		}
  	}
  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
  }
  
  /*
   * vmbus_ongpadl_created - GPADL created handler.
   *
   * This is invoked when we received a response to our gpadl create request.
   * Find the matching request, copy the response and signal the requesting
   * thread.
   */
  static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_gpadl_created *gpadlcreated;
  	struct vmbus_channel_msginfo *msginfo;
  	struct vmbus_channel_message_header *requestheader;
  	struct vmbus_channel_gpadl_header *gpadlheader;
  	unsigned long flags;
  
  	gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
  
  	/*
  	 * Find the establish msg, copy the result and signal/unblock the wait
  	 * event
  	 */
  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
  
  	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
  				msglistentry) {
  		requestheader =
  			(struct vmbus_channel_message_header *)msginfo->msg;
  
  		if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
  			gpadlheader =
  			(struct vmbus_channel_gpadl_header *)requestheader;
  
  			if ((gpadlcreated->child_relid ==
  			     gpadlheader->child_relid) &&
  			    (gpadlcreated->gpadl == gpadlheader->gpadl)) {
  				memcpy(&msginfo->response.gpadl_created,
  				       gpadlcreated,
  				       sizeof(
  					struct vmbus_channel_gpadl_created));
  				complete(&msginfo->waitevent);
  				break;
  			}
  		}
  	}
  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
  }
  
  /*
   * vmbus_ongpadl_torndown - GPADL torndown handler.
   *
   * This is invoked when we received a response to our gpadl teardown request.
   * Find the matching request, copy the response and signal the requesting
   * thread.
   */
  static void vmbus_ongpadl_torndown(
  			struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_gpadl_torndown *gpadl_torndown;
  	struct vmbus_channel_msginfo *msginfo;
  	struct vmbus_channel_message_header *requestheader;
  	struct vmbus_channel_gpadl_teardown *gpadl_teardown;
  	unsigned long flags;
  
  	gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
  
  	/*
  	 * Find the open msg, copy the result and signal/unblock the wait event
  	 */
  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
  
  	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
  				msglistentry) {
  		requestheader =
  			(struct vmbus_channel_message_header *)msginfo->msg;
  
  		if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
  			gpadl_teardown =
  			(struct vmbus_channel_gpadl_teardown *)requestheader;
  
  			if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
  				memcpy(&msginfo->response.gpadl_torndown,
  				       gpadl_torndown,
  				       sizeof(
  					struct vmbus_channel_gpadl_torndown));
  				complete(&msginfo->waitevent);
  				break;
  			}
  		}
  	}
  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
  }
  
  /*
   * vmbus_onversion_response - Version response handler
   *
   * This is invoked when we received a response to our initiate contact request.
   * Find the matching request, copy the response and signal the requesting
   * thread.
   */
  static void vmbus_onversion_response(
  		struct vmbus_channel_message_header *hdr)
  {
  	struct vmbus_channel_msginfo *msginfo;
  	struct vmbus_channel_message_header *requestheader;
  	struct vmbus_channel_version_response *version_response;
  	unsigned long flags;
  
  	version_response = (struct vmbus_channel_version_response *)hdr;
  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
  
  	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
  				msglistentry) {
  		requestheader =
  			(struct vmbus_channel_message_header *)msginfo->msg;
  
  		if (requestheader->msgtype ==
  		    CHANNELMSG_INITIATE_CONTACT) {
  			memcpy(&msginfo->response.version_response,
  			      version_response,
  			      sizeof(struct vmbus_channel_version_response));
  			complete(&msginfo->waitevent);
  		}
  	}
  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
  }
  
  /* Channel message dispatch table */
  struct vmbus_channel_message_table_entry
  	channel_message_table[CHANNELMSG_COUNT] = {
  	{CHANNELMSG_INVALID,			0, NULL},
  	{CHANNELMSG_OFFERCHANNEL,		0, vmbus_onoffer},
  	{CHANNELMSG_RESCIND_CHANNELOFFER,	0, vmbus_onoffer_rescind},
  	{CHANNELMSG_REQUESTOFFERS,		0, NULL},
  	{CHANNELMSG_ALLOFFERS_DELIVERED,	1, vmbus_onoffers_delivered},
  	{CHANNELMSG_OPENCHANNEL,		0, NULL},
  	{CHANNELMSG_OPENCHANNEL_RESULT,		1, vmbus_onopen_result},
  	{CHANNELMSG_CLOSECHANNEL,		0, NULL},
  	{CHANNELMSG_GPADL_HEADER,		0, NULL},
  	{CHANNELMSG_GPADL_BODY,			0, NULL},
  	{CHANNELMSG_GPADL_CREATED,		1, vmbus_ongpadl_created},
  	{CHANNELMSG_GPADL_TEARDOWN,		0, NULL},
  	{CHANNELMSG_GPADL_TORNDOWN,		1, vmbus_ongpadl_torndown},
  	{CHANNELMSG_RELID_RELEASED,		0, NULL},
  	{CHANNELMSG_INITIATE_CONTACT,		0, NULL},
  	{CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response},
  	{CHANNELMSG_UNLOAD,			0, NULL},
  	{CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response},
  };
  
  /*
   * vmbus_onmessage - Handler for channel protocol messages.
   *
   * This is invoked in the vmbus worker thread context.
   */
  void vmbus_onmessage(void *context)
  {
  	struct hv_message *msg = context;
  	struct vmbus_channel_message_header *hdr;
  	int size;
  
  	hdr = (struct vmbus_channel_message_header *)msg->u.payload;
  	size = msg->header.payload_size;
  
  	if (hdr->msgtype >= CHANNELMSG_COUNT) {
  		pr_err("Received invalid channel message type %d size %d
  ",
  			   hdr->msgtype, size);
  		print_hex_dump_bytes("", DUMP_PREFIX_NONE,
  				     (unsigned char *)msg->u.payload, size);
  		return;
  	}
  
  	if (channel_message_table[hdr->msgtype].message_handler)
  		channel_message_table[hdr->msgtype].message_handler(hdr);
  	else
  		pr_err("Unhandled channel message type %d
  ", hdr->msgtype);
  }
  
  /*
   * vmbus_request_offers - Send a request to get all our pending offers.
   */
  int vmbus_request_offers(void)
  {
  	struct vmbus_channel_message_header *msg;
  	struct vmbus_channel_msginfo *msginfo;
  	int ret;
  
  	msginfo = kmalloc(sizeof(*msginfo) +
  			  sizeof(struct vmbus_channel_message_header),
  			  GFP_KERNEL);
  	if (!msginfo)
  		return -ENOMEM;
  
  	msg = (struct vmbus_channel_message_header *)msginfo->msg;
  
  	msg->msgtype = CHANNELMSG_REQUESTOFFERS;
  
  
  	ret = vmbus_post_msg(msg,
  			       sizeof(struct vmbus_channel_message_header));
  	if (ret != 0) {
  		pr_err("Unable to request offers - %d
  ", ret);
  
  		goto cleanup;
  	}
  
  cleanup:
  	kfree(msginfo);
  
  	return ret;
  }
  
  /*
   * Retrieve the (sub) channel on which to send an outgoing request.
   * When a primary channel has multiple sub-channels, we try to
   * distribute the load equally amongst all available channels.
   */
  struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
  {
  	struct list_head *cur, *tmp;
  	int cur_cpu;
  	struct vmbus_channel *cur_channel;
  	struct vmbus_channel *outgoing_channel = primary;
  	int next_channel;
  	int i = 1;
  
  	if (list_empty(&primary->sc_list))
  		return outgoing_channel;
  
  	next_channel = primary->next_oc++;
  
  	if (next_channel > (primary->num_sc)) {
  		primary->next_oc = 0;
  		return outgoing_channel;
  	}
  
  	cur_cpu = hv_context.vp_index[get_cpu()];
  	put_cpu();
  	list_for_each_safe(cur, tmp, &primary->sc_list) {
  		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
  		if (cur_channel->state != CHANNEL_OPENED_STATE)
  			continue;
  
  		if (cur_channel->target_vp == cur_cpu)
  			return cur_channel;
  
  		if (i == next_channel)
  			return cur_channel;
  
  		i++;
  	}
  
  	return outgoing_channel;
  }
  EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel);
  
  static void invoke_sc_cb(struct vmbus_channel *primary_channel)
  {
  	struct list_head *cur, *tmp;
  	struct vmbus_channel *cur_channel;
  
  	if (primary_channel->sc_creation_callback == NULL)
  		return;
  
  	list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
  		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
  
  		primary_channel->sc_creation_callback(cur_channel);
  	}
  }
  
  void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
  				void (*sc_cr_cb)(struct vmbus_channel *new_sc))
  {
  	primary_channel->sc_creation_callback = sc_cr_cb;
  }
  EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);
  
  bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
  {
  	bool ret;
  
  	ret = !list_empty(&primary->sc_list);
  
  	if (ret) {
  		/*
  		 * Invoke the callback on sub-channel creation.
  		 * This will present a uniform interface to the
  		 * clients.
  		 */
  		invoke_sc_cb(primary);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);