/*

   * 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/module.h>

  #include <linux/hyperv.h>

  #include <linux/uio.h>

  #include <linux/interrupt.h>

  #include "hyperv_vmbus.h"

  #define NUM_PAGES_SPANNED(addr, len) \
  ((PAGE_ALIGN(addr + len) >> PAGE_SHIFT) - (addr >> PAGE_SHIFT))

  /*

   * vmbus_setevent- Trigger an event notification on the specified

   * channel.

   */

  void vmbus_setevent(struct vmbus_channel *channel)

  {

  	struct hv_monitor_page *monitorpage;

  	/*
  	 * For channels marked as in "low latency" mode
  	 * bypass the monitor page mechanism.
  	 */
  	if ((channel->offermsg.monitor_allocated) &&
  	    (!channel->low_latency)) {

  		/* Each u32 represents 32 channels */

  		sync_set_bit(channel->offermsg.child_relid & 31,

  			(unsigned long *) vmbus_connection.send_int_page +

  			(channel->offermsg.child_relid >> 5));

  		/* Get the child to parent monitor page */
  		monitorpage = vmbus_connection.monitor_pages[1];

  		sync_set_bit(channel->monitor_bit,

  			(unsigned long *)&monitorpage->trigger_group
  					[channel->monitor_grp].pending);

  	} else {

  		vmbus_set_event(channel);

  	}

  }

  EXPORT_SYMBOL_GPL(vmbus_setevent);

  /*

   * vmbus_open - Open the specified channel.

   */

  int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,

  		     u32 recv_ringbuffer_size, void *userdata, u32 userdatalen,
  		     void (*onchannelcallback)(void *context), void *context)

  {

  	struct vmbus_channel_open_channel *open_msg;

  	struct vmbus_channel_msginfo *open_info = NULL;

  	unsigned long flags;

  	int ret, err = 0;

  	struct page *page;

  	if (send_ringbuffer_size % PAGE_SIZE ||
  	    recv_ringbuffer_size % PAGE_SIZE)
  		return -EINVAL;

  	spin_lock_irqsave(&newchannel->lock, flags);

  	if (newchannel->state == CHANNEL_OPEN_STATE) {
  		newchannel->state = CHANNEL_OPENING_STATE;
  	} else {

  		spin_unlock_irqrestore(&newchannel->lock, flags);

  		return -EINVAL;
  	}

  	spin_unlock_irqrestore(&newchannel->lock, flags);

  	newchannel->onchannel_callback = onchannelcallback;
  	newchannel->channel_callback_context = context;

  	/* Allocate the ring buffer */

  	page = alloc_pages_node(cpu_to_node(newchannel->target_cpu),
  				GFP_KERNEL|__GFP_ZERO,
  				get_order(send_ringbuffer_size +
  				recv_ringbuffer_size));
  
  	if (!page)

  		page = alloc_pages(GFP_KERNEL|__GFP_ZERO,
  				   get_order(send_ringbuffer_size +
  					     recv_ringbuffer_size));

  	if (!page) {

  		err = -ENOMEM;

  		goto error_set_chnstate;

  	}

  	newchannel->ringbuffer_pages = page_address(page);

  	newchannel->ringbuffer_pagecount = (send_ringbuffer_size +

  					   recv_ringbuffer_size) >> PAGE_SHIFT;

  	ret = hv_ringbuffer_init(&newchannel->outbound, page,
  				 send_ringbuffer_size >> PAGE_SHIFT);

  	if (ret != 0) {

  		err = ret;

  		goto error_free_pages;

  	}

  	ret = hv_ringbuffer_init(&newchannel->inbound,
  				 &page[send_ringbuffer_size >> PAGE_SHIFT],
  				 recv_ringbuffer_size >> PAGE_SHIFT);

  	if (ret != 0) {

  		err = ret;

  		goto error_free_pages;

  	}

  	/* Establish the gpadl for the ring buffer */

  	newchannel->ringbuffer_gpadlhandle = 0;

  	ret = vmbus_establish_gpadl(newchannel,

  				    page_address(page),
  				    send_ringbuffer_size +
  				    recv_ringbuffer_size,
  				    &newchannel->ringbuffer_gpadlhandle);

  	if (ret != 0) {

  		err = ret;

  		goto error_free_pages;

  	}

  	/* Create and init the channel open message */

  	open_info = kmalloc(sizeof(*open_info) +

  			   sizeof(struct vmbus_channel_open_channel),
  			   GFP_KERNEL);

  	if (!open_info) {

  		err = -ENOMEM;

  		goto error_free_gpadl;

  	}

  	init_completion(&open_info->waitevent);

  	open_msg = (struct vmbus_channel_open_channel *)open_info->msg;

  	open_msg->header.msgtype = CHANNELMSG_OPENCHANNEL;
  	open_msg->openid = newchannel->offermsg.child_relid;
  	open_msg->child_relid = newchannel->offermsg.child_relid;
  	open_msg->ringbuffer_gpadlhandle = newchannel->ringbuffer_gpadlhandle;
  	open_msg->downstream_ringbuffer_pageoffset = send_ringbuffer_size >>

  						  PAGE_SHIFT;

  	open_msg->target_vp = newchannel->target_vp;

  	if (userdatalen > MAX_USER_DEFINED_BYTES) {

  		err = -EINVAL;

  		goto error_free_gpadl;

  	}

  	if (userdatalen)

  		memcpy(open_msg->userdata, userdata, userdatalen);

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_add_tail(&open_info->msglistentry,

  		      &vmbus_connection.chn_msg_list);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	ret = vmbus_post_msg(open_msg,

  			       sizeof(struct vmbus_channel_open_channel));

  	if (ret != 0) {
  		err = ret;

  		goto error_clean_msglist;

  	}

  	wait_for_completion(&open_info->waitevent);

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_del(&open_info->msglistentry);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	if (open_info->response.open_result.status) {
  		err = -EAGAIN;

  		goto error_free_gpadl;

  	}

  	newchannel->state = CHANNEL_OPENED_STATE;

  	kfree(open_info);

  	return 0;

  error_clean_msglist:

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
  	list_del(&open_info->msglistentry);
  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  error_free_gpadl:

  	vmbus_teardown_gpadl(newchannel, newchannel->ringbuffer_gpadlhandle);

  	kfree(open_info);
  error_free_pages:

  	hv_ringbuffer_cleanup(&newchannel->outbound);
  	hv_ringbuffer_cleanup(&newchannel->inbound);
  	__free_pages(page,
  		     get_order(send_ringbuffer_size + recv_ringbuffer_size));

  error_set_chnstate:

  	newchannel->state = CHANNEL_OPEN_STATE;

  	return err;

  }

  EXPORT_SYMBOL_GPL(vmbus_open);

  /* Used for Hyper-V Socket: a guest client's connect() to the host */
  int vmbus_send_tl_connect_request(const uuid_le *shv_guest_servie_id,
  				  const uuid_le *shv_host_servie_id)
  {
  	struct vmbus_channel_tl_connect_request conn_msg;
  
  	memset(&conn_msg, 0, sizeof(conn_msg));
  	conn_msg.header.msgtype = CHANNELMSG_TL_CONNECT_REQUEST;
  	conn_msg.guest_endpoint_id = *shv_guest_servie_id;
  	conn_msg.host_service_id = *shv_host_servie_id;
  
  	return vmbus_post_msg(&conn_msg, sizeof(conn_msg));
  }
  EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request);

  /*

   * create_gpadl_header - Creates a gpadl for the specified buffer

   */

  static int create_gpadl_header(void *kbuffer, u32 size,

  			       struct vmbus_channel_msginfo **msginfo)

  {
  	int i;

  	int pagecount;

  	struct vmbus_channel_gpadl_header *gpadl_header;
  	struct vmbus_channel_gpadl_body *gpadl_body;
  	struct vmbus_channel_msginfo *msgheader;
  	struct vmbus_channel_msginfo *msgbody = NULL;
  	u32 msgsize;

  	int pfnsum, pfncount, pfnleft, pfncurr, pfnsize;

  	pagecount = size >> PAGE_SHIFT;

  	/* do we need a gpadl body msg */

  	pfnsize = MAX_SIZE_CHANNEL_MESSAGE -

  		  sizeof(struct vmbus_channel_gpadl_header) -
  		  sizeof(struct gpa_range);

  	pfncount = pfnsize / sizeof(u64);

  	if (pagecount > pfncount) {

  		/* we need a gpadl body */

  		/* fill in the header */

  		msgsize = sizeof(struct vmbus_channel_msginfo) +

  			  sizeof(struct vmbus_channel_gpadl_header) +

  			  sizeof(struct gpa_range) + pfncount * sizeof(u64);
  		msgheader =  kzalloc(msgsize, GFP_KERNEL);
  		if (!msgheader)

  			goto nomem;

  		INIT_LIST_HEAD(&msgheader->submsglist);
  		msgheader->msgsize = msgsize;

  		gpadl_header = (struct vmbus_channel_gpadl_header *)

  			msgheader->msg;
  		gpadl_header->rangecount = 1;
  		gpadl_header->range_buflen = sizeof(struct gpa_range) +

  					 pagecount * sizeof(u64);

  		gpadl_header->range[0].byte_offset = 0;
  		gpadl_header->range[0].byte_count = size;

  		for (i = 0; i < pfncount; i++)

  			gpadl_header->range[0].pfn_array[i] = slow_virt_to_phys(
  				kbuffer + PAGE_SIZE * i) >> PAGE_SHIFT;

  		*msginfo = msgheader;

  		pfnsum = pfncount;
  		pfnleft = pagecount - pfncount;

  		/* how many pfns can we fit */

  		pfnsize = MAX_SIZE_CHANNEL_MESSAGE -

  			  sizeof(struct vmbus_channel_gpadl_body);

  		pfncount = pfnsize / sizeof(u64);

  		/* fill in the body */

  		while (pfnleft) {
  			if (pfnleft > pfncount)
  				pfncurr = pfncount;

  			else

  				pfncurr = pfnleft;

  			msgsize = sizeof(struct vmbus_channel_msginfo) +

  				  sizeof(struct vmbus_channel_gpadl_body) +

  				  pfncurr * sizeof(u64);
  			msgbody = kzalloc(msgsize, GFP_KERNEL);

  
  			if (!msgbody) {
  				struct vmbus_channel_msginfo *pos = NULL;
  				struct vmbus_channel_msginfo *tmp = NULL;
  				/*
  				 * Free up all the allocated messages.
  				 */
  				list_for_each_entry_safe(pos, tmp,
  					&msgheader->submsglist,
  					msglistentry) {
  
  					list_del(&pos->msglistentry);
  					kfree(pos);
  				}

  				goto nomem;

  			}

  			msgbody->msgsize = msgsize;

  			gpadl_body =

  				(struct vmbus_channel_gpadl_body *)msgbody->msg;

  
  			/*

  			 * Gpadl is u32 and we are using a pointer which could
  			 * be 64-bit

  			 * This is governed by the guest/host protocol and
  			 * so the hypervisor gurantees that this is ok.

  			 */

  			for (i = 0; i < pfncurr; i++)

  				gpadl_body->pfn[i] = slow_virt_to_phys(
  					kbuffer + PAGE_SIZE * (pfnsum + i)) >>
  					PAGE_SHIFT;

  			/* add to msg header */

  			list_add_tail(&msgbody->msglistentry,
  				      &msgheader->submsglist);

  			pfnsum += pfncurr;
  			pfnleft -= pfncurr;

  		}

  	} else {

  		/* everything fits in a header */

  		msgsize = sizeof(struct vmbus_channel_msginfo) +

  			  sizeof(struct vmbus_channel_gpadl_header) +

  			  sizeof(struct gpa_range) + pagecount * sizeof(u64);
  		msgheader = kzalloc(msgsize, GFP_KERNEL);
  		if (msgheader == NULL)

  			goto nomem;

  
  		INIT_LIST_HEAD(&msgheader->submsglist);

  		msgheader->msgsize = msgsize;

  
  		gpadl_header = (struct vmbus_channel_gpadl_header *)

  			msgheader->msg;
  		gpadl_header->rangecount = 1;
  		gpadl_header->range_buflen = sizeof(struct gpa_range) +

  					 pagecount * sizeof(u64);

  		gpadl_header->range[0].byte_offset = 0;
  		gpadl_header->range[0].byte_count = size;

  		for (i = 0; i < pagecount; i++)

  			gpadl_header->range[0].pfn_array[i] = slow_virt_to_phys(
  				kbuffer + PAGE_SIZE * i) >> PAGE_SHIFT;

  
  		*msginfo = msgheader;

  	}
  
  	return 0;

  nomem:

  	kfree(msgheader);
  	kfree(msgbody);

  	return -ENOMEM;

  }

  /*

   * vmbus_establish_gpadl - Estabish a GPADL for the specified buffer

   *

   * @channel: a channel

   * @kbuffer: from kmalloc or vmalloc

   * @size: page-size multiple
   * @gpadl_handle: some funky thing

   */

  int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,

  			       u32 size, u32 *gpadl_handle)

  {

  	struct vmbus_channel_gpadl_header *gpadlmsg;
  	struct vmbus_channel_gpadl_body *gpadl_body;

  	struct vmbus_channel_msginfo *msginfo = NULL;

  	struct vmbus_channel_msginfo *submsginfo, *tmp;

  	struct list_head *curr;

  	u32 next_gpadl_handle;

  	unsigned long flags;

  	int ret = 0;

  	next_gpadl_handle =
  		(atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);

  	ret = create_gpadl_header(kbuffer, size, &msginfo);

  	if (ret)
  		return ret;

  	init_completion(&msginfo->waitevent);

  	gpadlmsg = (struct vmbus_channel_gpadl_header *)msginfo->msg;
  	gpadlmsg->header.msgtype = CHANNELMSG_GPADL_HEADER;
  	gpadlmsg->child_relid = channel->offermsg.child_relid;
  	gpadlmsg->gpadl = next_gpadl_handle;

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_add_tail(&msginfo->msglistentry,

  		      &vmbus_connection.chn_msg_list);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	ret = vmbus_post_msg(gpadlmsg, msginfo->msgsize -

  			       sizeof(*msginfo));

  	if (ret != 0)

  		goto cleanup;

  	list_for_each(curr, &msginfo->submsglist) {
  		submsginfo = (struct vmbus_channel_msginfo *)curr;
  		gpadl_body =
  			(struct vmbus_channel_gpadl_body *)submsginfo->msg;

  		gpadl_body->header.msgtype =
  			CHANNELMSG_GPADL_BODY;
  		gpadl_body->gpadl = next_gpadl_handle;

  		ret = vmbus_post_msg(gpadl_body,
  				     submsginfo->msgsize -
  				     sizeof(*submsginfo));
  		if (ret != 0)
  			goto cleanup;

  	}

  	wait_for_completion(&msginfo->waitevent);

  	/* At this point, we received the gpadl created msg */

  	*gpadl_handle = gpadlmsg->gpadl;

  cleanup:

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_del(&msginfo->msglistentry);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
  				 msglistentry) {
  		kfree(submsginfo);
  	}

  	kfree(msginfo);

  	return ret;
  }

  EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);

  /*

   * vmbus_teardown_gpadl -Teardown the specified GPADL handle

   */

  int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle)

  {

  	struct vmbus_channel_gpadl_teardown *msg;

  	struct vmbus_channel_msginfo *info;

  	unsigned long flags;

  	int ret;

  	info = kmalloc(sizeof(*info) +
  		       sizeof(struct vmbus_channel_gpadl_teardown), GFP_KERNEL);

  	if (!info)
  		return -ENOMEM;

  	init_completion(&info->waitevent);

  	msg = (struct vmbus_channel_gpadl_teardown *)info->msg;

  	msg->header.msgtype = CHANNELMSG_GPADL_TEARDOWN;
  	msg->child_relid = channel->offermsg.child_relid;
  	msg->gpadl = gpadl_handle;

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_add_tail(&info->msglistentry,

  		      &vmbus_connection.chn_msg_list);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	ret = vmbus_post_msg(msg,

  			       sizeof(struct vmbus_channel_gpadl_teardown));

  	if (ret)
  		goto post_msg_err;
  
  	wait_for_completion(&info->waitevent);

  post_msg_err:

  	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

  	list_del(&info->msglistentry);

  	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

  	kfree(info);

  	return ret;
  }

  EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl);

  static void reset_channel_cb(void *arg)
  {
  	struct vmbus_channel *channel = arg;
  
  	channel->onchannel_callback = NULL;
  }

  static int vmbus_close_internal(struct vmbus_channel *channel)

  {

  	struct vmbus_channel_close_channel *msg;

  	int ret;

  	/*
  	 * process_chn_event(), running in the tasklet, can race
  	 * with vmbus_close_internal() in the case of SMP guest, e.g., when
  	 * the former is accessing channel->inbound.ring_buffer, the latter
  	 * could be freeing the ring_buffer pages.
  	 *
  	 * To resolve the race, we can serialize them by disabling the
  	 * tasklet when the latter is running here.
  	 */

  	hv_event_tasklet_disable(channel);

  	/*
  	 * In case a device driver's probe() fails (e.g.,
  	 * util_probe() -> vmbus_open() returns -ENOMEM) and the device is
  	 * rescinded later (e.g., we dynamically disble an Integrated Service
  	 * in Hyper-V Manager), the driver's remove() invokes vmbus_close():
  	 * here we should skip most of the below cleanup work.
  	 */
  	if (channel->state != CHANNEL_OPENED_STATE) {
  		ret = -EINVAL;
  		goto out;
  	}

  	channel->state = CHANNEL_OPEN_STATE;
  	channel->sc_creation_callback = NULL;

  	/* Stop callback and cancel the timer asap */

  	if (channel->target_cpu != get_cpu()) {
  		put_cpu();

  		smp_call_function_single(channel->target_cpu, reset_channel_cb,
  					 channel, true);

  	} else {

  		reset_channel_cb(channel);

  		put_cpu();
  	}

  	/* Send a closing message */

  	msg = &channel->close_msg.msg;

  	msg->header.msgtype = CHANNELMSG_CLOSECHANNEL;
  	msg->child_relid = channel->offermsg.child_relid;

  	ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_close_channel));

  	if (ret) {
  		pr_err("Close failed: close post msg return is %d
  ", ret);
  		/*
  		 * If we failed to post the close msg,
  		 * it is perhaps better to leak memory.
  		 */

  		goto out;

  	}

  	/* Tear down the gpadl for the channel's ring buffer */

  	if (channel->ringbuffer_gpadlhandle) {
  		ret = vmbus_teardown_gpadl(channel,
  					   channel->ringbuffer_gpadlhandle);
  		if (ret) {
  			pr_err("Close failed: teardown gpadl return %d
  ", ret);
  			/*
  			 * If we failed to teardown gpadl,
  			 * it is perhaps better to leak memory.
  			 */

  			goto out;

  		}
  	}

  	/* Cleanup the ring buffers for this channel */

  	hv_ringbuffer_cleanup(&channel->outbound);
  	hv_ringbuffer_cleanup(&channel->inbound);

  	free_pages((unsigned long)channel->ringbuffer_pages,
  		get_order(channel->ringbuffer_pagecount * PAGE_SIZE));

  out:

  	hv_event_tasklet_enable(channel);

  	return ret;

  }

  
  /*
   * vmbus_close - Close the specified channel
   */
  void vmbus_close(struct vmbus_channel *channel)
  {
  	struct list_head *cur, *tmp;
  	struct vmbus_channel *cur_channel;
  
  	if (channel->primary_channel != NULL) {
  		/*
  		 * We will only close sub-channels when
  		 * the primary is closed.
  		 */
  		return;
  	}
  	/*
  	 * Close all the sub-channels first and then close the
  	 * primary channel.
  	 */
  	list_for_each_safe(cur, tmp, &channel->sc_list) {
  		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
  		if (cur_channel->state != CHANNEL_OPENED_STATE)
  			continue;
  		vmbus_close_internal(cur_channel);
  	}
  	/*
  	 * Now close the primary.
  	 */
  	vmbus_close_internal(channel);
  }

  EXPORT_SYMBOL_GPL(vmbus_close);

  int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,

  			   u32 bufferlen, u64 requestid,

  			   enum vmbus_packet_type type, u32 flags, bool kick_q)

  {

  	struct vmpacket_descriptor desc;

  	u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;

  	u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));

  	struct kvec bufferlist[3];

  	u64 aligned_data = 0;

  	bool lock = channel->acquire_ring_lock;

  	int num_vecs = ((bufferlen != 0) ? 3 : 1);

  	/* Setup the descriptor */

  	desc.type = type; /* VmbusPacketTypeDataInBand; */
  	desc.flags = flags; /* VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED; */

  	/* in 8-bytes granularity */

  	desc.offset8 = sizeof(struct vmpacket_descriptor) >> 3;
  	desc.len8 = (u16)(packetlen_aligned >> 3);
  	desc.trans_id = requestid;

  	bufferlist[0].iov_base = &desc;
  	bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
  	bufferlist[1].iov_base = buffer;
  	bufferlist[1].iov_len = bufferlen;
  	bufferlist[2].iov_base = &aligned_data;
  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);

  	return hv_ringbuffer_write(channel, bufferlist, num_vecs,
  				   lock, kick_q);

  }

  EXPORT_SYMBOL(vmbus_sendpacket_ctl);
  
  /**
   * vmbus_sendpacket() - Send the specified buffer on the given channel
   * @channel: Pointer to vmbus_channel structure.
   * @buffer: Pointer to the buffer you want to receive the data into.
   * @bufferlen: Maximum size of what the the buffer will hold
   * @requestid: Identifier of the request
   * @type: Type of packet that is being send e.g. negotiate, time
   * packet etc.
   *
   * Sends data in @buffer directly to hyper-v via the vmbus
   * This will send the data unparsed to hyper-v.
   *
   * Mainly used by Hyper-V drivers.
   */
  int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
  			   u32 bufferlen, u64 requestid,
  			   enum vmbus_packet_type type, u32 flags)
  {
  	return vmbus_sendpacket_ctl(channel, buffer, bufferlen, requestid,
  				    type, flags, true);
  }

  EXPORT_SYMBOL(vmbus_sendpacket);

  /*

   * vmbus_sendpacket_pagebuffer_ctl - Send a range of single-page buffer
   * packets using a GPADL Direct packet type. This interface allows you
   * to control notifying the host. This will be useful for sending
   * batched data. Also the sender can control the send flags
   * explicitly.

   */

  int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,

  				     struct hv_page_buffer pagebuffers[],
  				     u32 pagecount, void *buffer, u32 bufferlen,

  				     u64 requestid,
  				     u32 flags,
  				     bool kick_q)

  {

  	int i;

  	struct vmbus_channel_packet_page_buffer desc;

  	u32 descsize;
  	u32 packetlen;
  	u32 packetlen_aligned;

  	struct kvec bufferlist[3];

  	u64 aligned_data = 0;

  	bool lock = channel->acquire_ring_lock;

  	if (pagecount > MAX_PAGE_BUFFER_COUNT)

  		return -EINVAL;

  	/*

  	 * Adjust the size down since vmbus_channel_packet_page_buffer is the

  	 * largest size we support
  	 */

  	descsize = sizeof(struct vmbus_channel_packet_page_buffer) -
  			  ((MAX_PAGE_BUFFER_COUNT - pagecount) *

  			  sizeof(struct hv_page_buffer));

  	packetlen = descsize + bufferlen;

  	packetlen_aligned = ALIGN(packetlen, sizeof(u64));

  	/* Setup the descriptor */

  	desc.type = VM_PKT_DATA_USING_GPA_DIRECT;

  	desc.flags = flags;

  	desc.dataoffset8 = descsize >> 3; /* in 8-bytes grandularity */
  	desc.length8 = (u16)(packetlen_aligned >> 3);
  	desc.transactionid = requestid;
  	desc.rangecount = pagecount;
  
  	for (i = 0; i < pagecount; i++) {

  		desc.range[i].len = pagebuffers[i].len;
  		desc.range[i].offset = pagebuffers[i].offset;
  		desc.range[i].pfn	 = pagebuffers[i].pfn;

  	}

  	bufferlist[0].iov_base = &desc;
  	bufferlist[0].iov_len = descsize;
  	bufferlist[1].iov_base = buffer;
  	bufferlist[1].iov_len = bufferlen;
  	bufferlist[2].iov_base = &aligned_data;
  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);

  	return hv_ringbuffer_write(channel, bufferlist, 3,
  				   lock, kick_q);

  }

  EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer_ctl);

  
  /*
   * vmbus_sendpacket_pagebuffer - Send a range of single-page buffer
   * packets using a GPADL Direct packet type.
   */
  int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
  				     struct hv_page_buffer pagebuffers[],
  				     u32 pagecount, void *buffer, u32 bufferlen,
  				     u64 requestid)
  {
  	u32 flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
  	return vmbus_sendpacket_pagebuffer_ctl(channel, pagebuffers, pagecount,
  					       buffer, bufferlen, requestid,
  					       flags, true);
  
  }

  EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer);

  /*

   * vmbus_sendpacket_multipagebuffer - Send a multi-page buffer packet

   * using a GPADL Direct packet type.

   * The buffer includes the vmbus descriptor.
   */
  int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
  			      struct vmbus_packet_mpb_array *desc,
  			      u32 desc_size,
  			      void *buffer, u32 bufferlen, u64 requestid)
  {

  	u32 packetlen;
  	u32 packetlen_aligned;
  	struct kvec bufferlist[3];
  	u64 aligned_data = 0;

  	bool lock = channel->acquire_ring_lock;

  
  	packetlen = desc_size + bufferlen;
  	packetlen_aligned = ALIGN(packetlen, sizeof(u64));
  
  	/* Setup the descriptor */
  	desc->type = VM_PKT_DATA_USING_GPA_DIRECT;
  	desc->flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
  	desc->dataoffset8 = desc_size >> 3; /* in 8-bytes grandularity */
  	desc->length8 = (u16)(packetlen_aligned >> 3);
  	desc->transactionid = requestid;
  	desc->rangecount = 1;
  
  	bufferlist[0].iov_base = desc;
  	bufferlist[0].iov_len = desc_size;
  	bufferlist[1].iov_base = buffer;
  	bufferlist[1].iov_len = bufferlen;
  	bufferlist[2].iov_base = &aligned_data;
  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);

  	return hv_ringbuffer_write(channel, bufferlist, 3,
  				   lock, true);

  }
  EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
  
  /*
   * vmbus_sendpacket_multipagebuffer - Send a multi-page buffer packet
   * using a GPADL Direct packet type.

   */

  int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,

  				struct hv_multipage_buffer *multi_pagebuffer,
  				void *buffer, u32 bufferlen, u64 requestid)

  {

  	struct vmbus_channel_packet_multipage_buffer desc;

  	u32 descsize;
  	u32 packetlen;
  	u32 packetlen_aligned;

  	struct kvec bufferlist[3];

  	u64 aligned_data = 0;

  	bool lock = channel->acquire_ring_lock;

  	u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,
  					 multi_pagebuffer->len);

  	if (pfncount > MAX_MULTIPAGE_BUFFER_COUNT)

  		return -EINVAL;

  	/*

  	 * Adjust the size down since vmbus_channel_packet_multipage_buffer is

  	 * the largest size we support
  	 */

  	descsize = sizeof(struct vmbus_channel_packet_multipage_buffer) -
  			  ((MAX_MULTIPAGE_BUFFER_COUNT - pfncount) *

  			  sizeof(u64));

  	packetlen = descsize + bufferlen;

  	packetlen_aligned = ALIGN(packetlen, sizeof(u64));

  	/* Setup the descriptor */

  	desc.type = VM_PKT_DATA_USING_GPA_DIRECT;

  	desc.flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;

  	desc.dataoffset8 = descsize >> 3; /* in 8-bytes grandularity */
  	desc.length8 = (u16)(packetlen_aligned >> 3);
  	desc.transactionid = requestid;

  	desc.rangecount = 1;

  	desc.range.len = multi_pagebuffer->len;
  	desc.range.offset = multi_pagebuffer->offset;

  	memcpy(desc.range.pfn_array, multi_pagebuffer->pfn_array,

  	       pfncount * sizeof(u64));

  	bufferlist[0].iov_base = &desc;
  	bufferlist[0].iov_len = descsize;
  	bufferlist[1].iov_base = buffer;
  	bufferlist[1].iov_len = bufferlen;
  	bufferlist[2].iov_base = &aligned_data;
  	bufferlist[2].iov_len = (packetlen_aligned - packetlen);

  	return hv_ringbuffer_write(channel, bufferlist, 3,
  				   lock, true);

  }

  EXPORT_SYMBOL_GPL(vmbus_sendpacket_multipagebuffer);

  
  /**

   * vmbus_recvpacket() - Retrieve the user packet on the specified channel

   * @channel: Pointer to vmbus_channel structure.
   * @buffer: Pointer to the buffer you want to receive the data into.
   * @bufferlen: Maximum size of what the the buffer will hold
   * @buffer_actual_len: The actual size of the data after it was received
   * @requestid: Identifier of the request

   *
   * Receives directly from the hyper-v vmbus and puts the data it received
   * into Buffer. This will receive the data unparsed from hyper-v.
   *
   * Mainly used by Hyper-V drivers.

   */

  static inline int
  __vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
  		   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,
  		   bool raw)

  {

  	return hv_ringbuffer_read(channel, buffer, bufferlen,
  				  buffer_actual_len, requestid, raw);

  }
  
  int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
  		     u32 bufferlen, u32 *buffer_actual_len,
  		     u64 *requestid)
  {
  	return __vmbus_recvpacket(channel, buffer, bufferlen,
  				  buffer_actual_len, requestid, false);

  }

  EXPORT_SYMBOL(vmbus_recvpacket);

  /*

   * vmbus_recvpacket_raw - Retrieve the raw packet on the specified channel

   */

  int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,

  			      u32 bufferlen, u32 *buffer_actual_len,
  			      u64 *requestid)

  {

  	return __vmbus_recvpacket(channel, buffer, bufferlen,
  				  buffer_actual_len, requestid, true);

  }

  EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);