/*
 * 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 "hyperv_vmbus.h"

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

/* Internal routines */
static int create_gpadl_header(
        void *kbuffer,  /* must be phys and virt contiguous */
        u32 size,       /* page-size multiple */
        struct vmbus_channel_msginfo **msginfo,
        u32 *messagecount);
static void vmbus_setevent(struct vmbus_channel *channel);

/*
 * vmbus_setevent- Trigger an event notification on the specified
 * channel.
 */
static void vmbus_setevent(struct vmbus_channel *channel)
{
        struct hv_monitor_page *monitorpage;

        if (channel->offermsg.monitor_allocated) {
                /* 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));

                monitorpage = vmbus_connection.monitor_pages;
                monitorpage++; /* Get the child to parent monitor page */

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

        } else {
                vmbus_set_event(channel->offermsg.child_relid);
        }
}

/*
 * vmbus_get_debug_info -Retrieve various channel debug info
 */
void vmbus_get_debug_info(struct vmbus_channel *channel,
                              struct vmbus_channel_debug_info *debuginfo)
{
        struct hv_monitor_page *monitorpage;
        u8 monitor_group = (u8)channel->offermsg.monitorid / 32;
        u8 monitor_offset = (u8)channel->offermsg.monitorid % 32;

        debuginfo->relid = channel->offermsg.child_relid;
        debuginfo->state = channel->state;
        memcpy(&debuginfo->interfacetype,
               &channel->offermsg.offer.if_type, sizeof(uuid_le));
        memcpy(&debuginfo->interface_instance,
               &channel->offermsg.offer.if_instance,
               sizeof(uuid_le));

        monitorpage = (struct hv_monitor_page *)vmbus_connection.monitor_pages;

        debuginfo->monitorid = channel->offermsg.monitorid;

        debuginfo->servermonitor_pending =
                        monitorpage->trigger_group[monitor_group].pending;
        debuginfo->servermonitor_latency =
                        monitorpage->latency[monitor_group][monitor_offset];
        debuginfo->servermonitor_connectionid =
                        monitorpage->parameter[monitor_group]
                                        [monitor_offset].connectionid.u.id;

        monitorpage++;

        debuginfo->clientmonitor_pending =
                        monitorpage->trigger_group[monitor_group].pending;
        debuginfo->clientmonitor_latency =
                        monitorpage->latency[monitor_group][monitor_offset];
        debuginfo->clientmonitor_connectionid =
                        monitorpage->parameter[monitor_group]
                                        [monitor_offset].connectionid.u.id;

        hv_ringbuffer_get_debuginfo(&channel->inbound, &debuginfo->inbound);
        hv_ringbuffer_get_debuginfo(&channel->outbound, &debuginfo->outbound);
}

/*
 * 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;
        void *in, *out;
        unsigned long flags;
        int ret, t, err = 0;

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

        /* Allocate the ring buffer */
        out = (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO,
                get_order(send_ringbuffer_size + recv_ringbuffer_size));

        if (!out)
                return -ENOMEM;


        in = (void *)((unsigned long)out + send_ringbuffer_size);

        newchannel->ringbuffer_pages = out;
        newchannel->ringbuffer_pagecount = (send_ringbuffer_size +
                                           recv_ringbuffer_size) >> PAGE_SHIFT;

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

        if (ret != 0) {
                err = ret;
                goto error0;
        }

        ret = hv_ringbuffer_init(
                &newchannel->inbound, in, recv_ringbuffer_size);
        if (ret != 0) {
                err = ret;
                goto error0;
        }


        /* Establish the gpadl for the ring buffer */
        newchannel->ringbuffer_gpadlhandle = 0;

        ret = vmbus_establish_gpadl(newchannel,
                                         newchannel->outbound.ring_buffer,
                                         send_ringbuffer_size +
                                         recv_ringbuffer_size,
                                         &newchannel->ringbuffer_gpadlhandle);

        if (ret != 0) {
                err = ret;
                goto error0;
        }

        /* 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 error0;
        }

        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->server_contextarea_gpadlhandle = 0;

        if (userdatalen > MAX_USER_DEFINED_BYTES) {
                err = -EINVAL;
                goto error0;
        }

        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)
                goto error1;

        t = wait_for_completion_timeout(&open_info->waitevent, 5*HZ);
        if (t == 0) {
                err = -ETIMEDOUT;
                goto error1;
        }


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

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

        kfree(open_info);
        return err;

error1:
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
        list_del(&open_info->msglistentry);
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

error0:
        free_pages((unsigned long)out,
                get_order(send_ringbuffer_size + recv_ringbuffer_size));
        kfree(open_info);
        return err;
}
EXPORT_SYMBOL_GPL(vmbus_open);

/*
 * create_gpadl_header - Creates a gpadl for the specified buffer
 */
static int create_gpadl_header(void *kbuffer, u32 size,
                                         struct vmbus_channel_msginfo **msginfo,
                                         u32 *messagecount)
{
        int i;
        int pagecount;
        unsigned long long pfn;
        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;
        pfn = virt_to_phys(kbuffer) >> 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] = pfn+i;
                *msginfo = msgheader;
                *messagecount = 1;

                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;
                        (*messagecount)++;
                        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] = pfn + pfnsum + i;

                        /* 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;
                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] = pfn+i;

                *msginfo = msgheader;
                *messagecount = 1;
        }

        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
 * @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;
        u32 msgcount;
        struct list_head *curr;
        u32 next_gpadl_handle;
        unsigned long flags;
        int ret = 0;
        int t;

        next_gpadl_handle = atomic_read(&vmbus_connection.next_gpadl_handle);
        atomic_inc(&vmbus_connection.next_gpadl_handle);

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

        if (msgcount > 1) {
                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;

                }
        }
        t = wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
        BUG_ON(t == 0);


        /* 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);

        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, t;

        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));

        BUG_ON(ret != 0);
        t = wait_for_completion_timeout(&info->waitevent, 5*HZ);
        BUG_ON(t == 0);

        /* Received a torndown response */
        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);

/*
 * vmbus_close - Close the specified channel
 */
void vmbus_close(struct vmbus_channel *channel)
{
        struct vmbus_channel_close_channel *msg;
        int ret;
        unsigned long flags;

        /* Stop callback and cancel the timer asap */
        spin_lock_irqsave(&channel->inbound_lock, flags);
        channel->onchannel_callback = NULL;
        spin_unlock_irqrestore(&channel->inbound_lock, flags);

        /* 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));

        BUG_ON(ret != 0);
        /* Tear down the gpadl for the channel's ring buffer */
        if (channel->ringbuffer_gpadlhandle)
                vmbus_teardown_gpadl(channel,
                                          channel->ringbuffer_gpadlhandle);

        /* 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));


}
EXPORT_SYMBOL_GPL(vmbus_close);

/**
 * 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, const void *buffer,
                           u32 bufferlen, u64 requestid,
                           enum vmbus_packet_type type, u32 flags)
{
        struct vmpacket_descriptor desc;
        u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;
        u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
        struct scatterlist bufferlist[3];
        u64 aligned_data = 0;
        int ret;


        /* 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;

        sg_init_table(bufferlist, 3);
        sg_set_buf(&bufferlist[0], &desc, sizeof(struct vmpacket_descriptor));
        sg_set_buf(&bufferlist[1], buffer, bufferlen);
        sg_set_buf(&bufferlist[2], &aligned_data,
                   packetlen_aligned - packetlen);

        ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

        if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))
                vmbus_setevent(channel);

        return ret;
}
EXPORT_SYMBOL(vmbus_sendpacket);

/*
 * 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)
{
        int ret;
        int i;
        struct vmbus_channel_packet_page_buffer desc;
        u32 descsize;
        u32 packetlen;
        u32 packetlen_aligned;
        struct scatterlist bufferlist[3];
        u64 aligned_data = 0;

        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 = 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 = 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;
        }

        sg_init_table(bufferlist, 3);
        sg_set_buf(&bufferlist[0], &desc, descsize);
        sg_set_buf(&bufferlist[1], buffer, bufferlen);
        sg_set_buf(&bufferlist[2], &aligned_data,
                packetlen_aligned - packetlen);

        ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

        if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))
                vmbus_setevent(channel);

        return ret;
}
EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer);

/*
 * 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)
{
        int ret;
        struct vmbus_channel_packet_multipage_buffer desc;
        u32 descsize;
        u32 packetlen;
        u32 packetlen_aligned;
        struct scatterlist bufferlist[3];
        u64 aligned_data = 0;
        u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,
                                         multi_pagebuffer->len);


        if ((pfncount < 0) || (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));

        sg_init_table(bufferlist, 3);
        sg_set_buf(&bufferlist[0], &desc, descsize);
        sg_set_buf(&bufferlist[1], buffer, bufferlen);
        sg_set_buf(&bufferlist[2], &aligned_data,
                packetlen_aligned - packetlen);

        ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

        if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))
                vmbus_setevent(channel);

        return ret;
}
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.
 */
int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
                        u32 bufferlen, u32 *buffer_actual_len, u64 *requestid)
{
        struct vmpacket_descriptor desc;
        u32 packetlen;
        u32 userlen;
        int ret;

        *buffer_actual_len = 0;
        *requestid = 0;


        ret = hv_ringbuffer_peek(&channel->inbound, &desc,
                             sizeof(struct vmpacket_descriptor));
        if (ret != 0)
                return 0;

        packetlen = desc.len8 << 3;
        userlen = packetlen - (desc.offset8 << 3);

        *buffer_actual_len = userlen;

        if (userlen > bufferlen) {

                pr_err("Buffer too small - got %d needs %d\n",
                           bufferlen, userlen);
                return -ETOOSMALL;
        }

        *requestid = desc.trans_id;

        /* Copy over the packet to the user buffer */
        ret = hv_ringbuffer_read(&channel->inbound, buffer, userlen,
                             (desc.offset8 << 3));


        return 0;
}
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)
{
        struct vmpacket_descriptor desc;
        u32 packetlen;
        u32 userlen;
        int ret;

        *buffer_actual_len = 0;
        *requestid = 0;


        ret = hv_ringbuffer_peek(&channel->inbound, &desc,
                             sizeof(struct vmpacket_descriptor));
        if (ret != 0)
                return 0;


        packetlen = desc.len8 << 3;
        userlen = packetlen - (desc.offset8 << 3);

        *buffer_actual_len = packetlen;

        if (packetlen > bufferlen) {
                pr_err("Buffer too small - needed %d bytes but "
                        "got space for only %d bytes\n",
                        packetlen, bufferlen);
                return -ENOBUFS;
        }

        *requestid = desc.trans_id;

        /* Copy over the entire packet to the user buffer */
        ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0);

        return 0;
}
EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);