// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * 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 <asm/page.h>
#include <asm/mshyperv.h>

#include "hyperv_vmbus.h"

/*
 * hv_gpadl_size - Return the real size of a gpadl, the size that Hyper-V uses
 *
 * For BUFFER gpadl, Hyper-V uses the exact same size as the guest does.
 *
 * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the header
 * (because of the alignment requirement), however, the hypervisor only
 * uses the first HV_HYP_PAGE_SIZE as the header, therefore leaving a
 * (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap. And since there are two rings in a
 * ringbuffer, the total size for a RING gpadl that Hyper-V uses is the
 * total size that the guest uses minus twice of the gap size.
 */
static inline u32 hv_gpadl_size(enum hv_gpadl_type type, u32 size)
{
        switch (type) {
        case HV_GPADL_BUFFER:
                return size;
        case HV_GPADL_RING:
                /* The size of a ringbuffer must be page-aligned */
                BUG_ON(size % PAGE_SIZE);
                /*
                 * Two things to notice here:
                 * 1) We're processing two ring buffers as a unit
                 * 2) We're skipping any space larger than HV_HYP_PAGE_SIZE in
                 * the first guest-size page of each of the two ring buffers.
                 * So we effectively subtract out two guest-size pages, and add
                 * back two Hyper-V size pages.
                 */
                return size - 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
        }
        BUG();
        return 0;
}

/*
 * hv_ring_gpadl_send_hvpgoffset - Calculate the send offset (in unit of
 *                                 HV_HYP_PAGE) in a ring gpadl based on the
 *                                 offset in the guest
 *
 * @offset: the offset (in bytes) where the send ringbuffer starts in the
 *               virtual address space of the guest
 */
static inline u32 hv_ring_gpadl_send_hvpgoffset(u32 offset)
{

        /*
         * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the
         * header (because of the alignment requirement), however, the
         * hypervisor only uses the first HV_HYP_PAGE_SIZE as the header,
         * therefore leaving a (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap.
         *
         * And to calculate the effective send offset in gpadl, we need to
         * substract this gap.
         */
        return (offset - (PAGE_SIZE - HV_HYP_PAGE_SIZE)) >> HV_HYP_PAGE_SHIFT;
}

/*
 * hv_gpadl_hvpfn - Return the Hyper-V page PFN of the @i th Hyper-V page in
 *                  the gpadl
 *
 * @type: the type of the gpadl
 * @kbuffer: the pointer to the gpadl in the guest
 * @size: the total size (in bytes) of the gpadl
 * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
 *               virtual address space of the guest
 * @i: the index
 */
static inline u64 hv_gpadl_hvpfn(enum hv_gpadl_type type, void *kbuffer,
                                 u32 size, u32 send_offset, int i)
{
        int send_idx = hv_ring_gpadl_send_hvpgoffset(send_offset);
        unsigned long delta = 0UL;

        switch (type) {
        case HV_GPADL_BUFFER:
                break;
        case HV_GPADL_RING:
                if (i == 0)
                        delta = 0;
                else if (i <= send_idx)
                        delta = PAGE_SIZE - HV_HYP_PAGE_SIZE;
                else
                        delta = 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
                break;
        default:
                BUG();
                break;
        }

        return virt_to_hvpfn(kbuffer + delta + (HV_HYP_PAGE_SIZE * i));
}

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

        trace_vmbus_setevent(channel);

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

                /* 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_free_ring - drop mapping of ring buffer */
void vmbus_free_ring(struct vmbus_channel *channel)
{
        hv_ringbuffer_cleanup(&channel->outbound);
        hv_ringbuffer_cleanup(&channel->inbound);

        if (channel->ringbuffer_page) {
                __free_pages(channel->ringbuffer_page,
                             get_order(channel->ringbuffer_pagecount
                                       << PAGE_SHIFT));
                channel->ringbuffer_page = NULL;
        }
}
EXPORT_SYMBOL_GPL(vmbus_free_ring);

/* vmbus_alloc_ring - allocate and map pages for ring buffer */
int vmbus_alloc_ring(struct vmbus_channel *newchannel,
                     u32 send_size, u32 recv_size)
{
        struct page *page;
        int order;

        if (send_size % PAGE_SIZE || recv_size % PAGE_SIZE)
                return -EINVAL;

        /* Allocate the ring buffer */
        order = get_order(send_size + recv_size);
        page = alloc_pages_node(cpu_to_node(newchannel->target_cpu),
                                GFP_KERNEL|__GFP_ZERO, order);

        if (!page)
                page = alloc_pages(GFP_KERNEL|__GFP_ZERO, order);

        if (!page)
                return -ENOMEM;

        newchannel->ringbuffer_page = page;
        newchannel->ringbuffer_pagecount = (send_size + recv_size) >> PAGE_SHIFT;
        newchannel->ringbuffer_send_offset = send_size >> PAGE_SHIFT;

        return 0;
}
EXPORT_SYMBOL_GPL(vmbus_alloc_ring);

/* Used for Hyper-V Socket: a guest client's connect() to the host */
int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id,
                                  const guid_t *shv_host_servie_id)
{
        struct vmbus_channel_tl_connect_request conn_msg;
        int ret;

        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;

        ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true);

        trace_vmbus_send_tl_connect_request(&conn_msg, ret);

        return ret;
}
EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request);

static int send_modifychannel_without_ack(struct vmbus_channel *channel, u32 target_vp)
{
        struct vmbus_channel_modifychannel msg;
        int ret;

        memset(&msg, 0, sizeof(msg));
        msg.header.msgtype = CHANNELMSG_MODIFYCHANNEL;
        msg.child_relid = channel->offermsg.child_relid;
        msg.target_vp = target_vp;

        ret = vmbus_post_msg(&msg, sizeof(msg), true);
        trace_vmbus_send_modifychannel(&msg, ret);

        return ret;
}

static int send_modifychannel_with_ack(struct vmbus_channel *channel, u32 target_vp)
{
        struct vmbus_channel_modifychannel *msg;
        struct vmbus_channel_msginfo *info;
        unsigned long flags;
        int ret;

        info = kzalloc(sizeof(struct vmbus_channel_msginfo) +
                                sizeof(struct vmbus_channel_modifychannel),
                       GFP_KERNEL);
        if (!info)
                return -ENOMEM;

        init_completion(&info->waitevent);
        info->waiting_channel = channel;

        msg = (struct vmbus_channel_modifychannel *)info->msg;
        msg->header.msgtype = CHANNELMSG_MODIFYCHANNEL;
        msg->child_relid = channel->offermsg.child_relid;
        msg->target_vp = target_vp;

        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(*msg), true);
        trace_vmbus_send_modifychannel(msg, ret);
        if (ret != 0) {
                spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
                list_del(&info->msglistentry);
                spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
                goto free_info;
        }

        /*
         * Release channel_mutex; otherwise, vmbus_onoffer_rescind() could block on
         * the mutex and be unable to signal the completion.
         *
         * See the caller target_cpu_store() for information about the usage of the
         * mutex.
         */
        mutex_unlock(&vmbus_connection.channel_mutex);
        wait_for_completion(&info->waitevent);
        mutex_lock(&vmbus_connection.channel_mutex);

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

        if (info->response.modify_response.status)
                ret = -EAGAIN;

free_info:
        kfree(info);
        return ret;
}

/*
 * Set/change the vCPU (@target_vp) the channel (@child_relid) will interrupt.
 *
 * CHANNELMSG_MODIFYCHANNEL messages are aynchronous.  When VMbus version 5.3
 * or later is negotiated, Hyper-V always sends an ACK in response to such a
 * message.  For VMbus version 5.2 and earlier, it never sends an ACK.  With-
 * out an ACK, we can not know when the host will stop interrupting the "old"
 * vCPU and start interrupting the "new" vCPU for the given channel.
 *
 * The CHANNELMSG_MODIFYCHANNEL message type is supported since VMBus version
 * VERSION_WIN10_V4_1.
 */
int vmbus_send_modifychannel(struct vmbus_channel *channel, u32 target_vp)
{
        if (vmbus_proto_version >= VERSION_WIN10_V5_3)
                return send_modifychannel_with_ack(channel, target_vp);
        return send_modifychannel_without_ack(channel, target_vp);
}
EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);

/*
 * create_gpadl_header - Creates a gpadl for the specified buffer
 */
static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
                               u32 size, u32 send_offset,
                               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 = hv_gpadl_size(type, size) >> HV_HYP_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 = hv_gpadl_size(type, size);
                for (i = 0; i < pfncount; i++)
                        gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
                                type, kbuffer, size, send_offset, i);
                *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 guarantees that this is ok.
                         */
                        for (i = 0; i < pfncurr; i++)
                                gpadl_body->pfn[i] = hv_gpadl_hvpfn(type,
                                        kbuffer, size, send_offset, 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;

                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 = hv_gpadl_size(type, size);
                for (i = 0; i < pagecount; i++)
                        gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
                                type, kbuffer, size, send_offset, i);

                *msginfo = msgheader;
        }

        return 0;
nomem:
        kfree(msgheader);
        kfree(msgbody);
        return -ENOMEM;
}

/*
 * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
 *
 * @channel: a channel
 * @type: the type of the corresponding GPADL, only meaningful for the guest.
 * @kbuffer: from kmalloc or vmalloc
 * @size: page-size multiple
 * @send_offset: the offset (in bytes) where the send ring buffer starts,
 *              should be 0 for BUFFER type gpadl
 * @gpadl_handle: some funky thing
 */
static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
                                   enum hv_gpadl_type type, void *kbuffer,
                                   u32 size, u32 send_offset,
                                   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(type, kbuffer, size, send_offset, &msginfo);
        if (ret)
                return ret;

        init_completion(&msginfo->waitevent);
        msginfo->waiting_channel = channel;

        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);

        if (channel->rescind) {
                ret = -ENODEV;
                goto cleanup;
        }

        ret = vmbus_post_msg(gpadlmsg, msginfo->msgsize -
                             sizeof(*msginfo), true);

        trace_vmbus_establish_gpadl_header(gpadlmsg, ret);

        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),
                                     true);

                trace_vmbus_establish_gpadl_body(gpadl_body, ret);

                if (ret != 0)
                        goto cleanup;

        }
        wait_for_completion(&msginfo->waitevent);

        if (msginfo->response.gpadl_created.creation_status != 0) {
                pr_err("Failed to establish GPADL: err = 0x%x\n",
                       msginfo->response.gpadl_created.creation_status);

                ret = -EDQUOT;
                goto cleanup;
        }

        if (channel->rescind) {
                ret = -ENODEV;
                goto cleanup;
        }

        /* 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;
}

/*
 * vmbus_establish_gpadl - Establish 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)
{
        return __vmbus_establish_gpadl(channel, HV_GPADL_BUFFER, kbuffer, size,
                                       0U, gpadl_handle);
}
EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);

/**
 * request_arr_init - Allocates memory for the requestor array. Each slot
 * keeps track of the next available slot in the array. Initially, each
 * slot points to the next one (as in a Linked List). The last slot
 * does not point to anything, so its value is U64_MAX by default.
 * @size The size of the array
 */
static u64 *request_arr_init(u32 size)
{
        int i;
        u64 *req_arr;

        req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL);
        if (!req_arr)
                return NULL;

        for (i = 0; i < size - 1; i++)
                req_arr[i] = i + 1;

        /* Last slot (no more available slots) */
        req_arr[i] = U64_MAX;

        return req_arr;
}

/*
 * vmbus_alloc_requestor - Initializes @rqstor's fields.
 * Index 0 is the first free slot
 * @size: Size of the requestor array
 */
static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size)
{
        u64 *rqst_arr;
        unsigned long *bitmap;

        rqst_arr = request_arr_init(size);
        if (!rqst_arr)
                return -ENOMEM;

        bitmap = bitmap_zalloc(size, GFP_KERNEL);
        if (!bitmap) {
                kfree(rqst_arr);
                return -ENOMEM;
        }

        rqstor->req_arr = rqst_arr;
        rqstor->req_bitmap = bitmap;
        rqstor->size = size;
        rqstor->next_request_id = 0;
        spin_lock_init(&rqstor->req_lock);

        return 0;
}

/*
 * vmbus_free_requestor - Frees memory allocated for @rqstor
 * @rqstor: Pointer to the requestor struct
 */
static void vmbus_free_requestor(struct vmbus_requestor *rqstor)
{
        kfree(rqstor->req_arr);
        bitmap_free(rqstor->req_bitmap);
}

static int __vmbus_open(struct vmbus_channel *newchannel,
                       void *userdata, u32 userdatalen,
                       void (*onchannelcallback)(void *context), void *context)
{
        struct vmbus_channel_open_channel *open_msg;
        struct vmbus_channel_msginfo *open_info = NULL;
        struct page *page = newchannel->ringbuffer_page;
        u32 send_pages, recv_pages;
        unsigned long flags;
        int err;

        if (userdatalen > MAX_USER_DEFINED_BYTES)
                return -EINVAL;

        send_pages = newchannel->ringbuffer_send_offset;
        recv_pages = newchannel->ringbuffer_pagecount - send_pages;

        if (newchannel->state != CHANNEL_OPEN_STATE)
                return -EINVAL;

        /* Create and init requestor */
        if (newchannel->rqstor_size) {
                if (vmbus_alloc_requestor(&newchannel->requestor, newchannel->rqstor_size))
                        return -ENOMEM;
        }

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

        err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages);
        if (err)
                goto error_clean_ring;

        err = hv_ringbuffer_init(&newchannel->inbound,
                                 &page[send_pages], recv_pages);
        if (err)
                goto error_clean_ring;

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

        err = __vmbus_establish_gpadl(newchannel, HV_GPADL_RING,
                                      page_address(newchannel->ringbuffer_page),
                                      (send_pages + recv_pages) << PAGE_SHIFT,
                                      newchannel->ringbuffer_send_offset << PAGE_SHIFT,
                                      &newchannel->ringbuffer_gpadlhandle);
        if (err)
                goto error_clean_ring;

        /* Create and init the channel open message */
        open_info = kzalloc(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_info->waiting_channel = newchannel;

        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;
        /*
         * The unit of ->downstream_ringbuffer_pageoffset is HV_HYP_PAGE and
         * the unit of ->ringbuffer_send_offset (i.e. send_pages) is PAGE, so
         * here we calculate it into HV_HYP_PAGE.
         */
        open_msg->downstream_ringbuffer_pageoffset =
                hv_ring_gpadl_send_hvpgoffset(send_pages << PAGE_SHIFT);
        open_msg->target_vp = hv_cpu_number_to_vp_number(newchannel->target_cpu);

        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);

        if (newchannel->rescind) {
                err = -ENODEV;
                goto error_clean_msglist;
        }

        err = vmbus_post_msg(open_msg,
                             sizeof(struct vmbus_channel_open_channel), true);

        trace_vmbus_open(open_msg, err);

        if (err != 0)
                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 (newchannel->rescind) {
                err = -ENODEV;
                goto error_free_info;
        }

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

        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_info:
        kfree(open_info);
error_free_gpadl:
        vmbus_teardown_gpadl(newchannel, newchannel->ringbuffer_gpadlhandle);
        newchannel->ringbuffer_gpadlhandle = 0;
error_clean_ring:
        hv_ringbuffer_cleanup(&newchannel->outbound);
        hv_ringbuffer_cleanup(&newchannel->inbound);
        vmbus_free_requestor(&newchannel->requestor);
        newchannel->state = CHANNEL_OPEN_STATE;
        return err;
}

/*
 * vmbus_connect_ring - Open the channel but reuse ring buffer
 */
int vmbus_connect_ring(struct vmbus_channel *newchannel,
                       void (*onchannelcallback)(void *context), void *context)
{
        return  __vmbus_open(newchannel, NULL, 0, onchannelcallback, context);
}
EXPORT_SYMBOL_GPL(vmbus_connect_ring);

/*
 * 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)
{
        int err;

        err = vmbus_alloc_ring(newchannel, send_ringbuffer_size,
                               recv_ringbuffer_size);
        if (err)
                return err;

        err = __vmbus_open(newchannel, userdata, userdatalen,
                           onchannelcallback, context);
        if (err)
                vmbus_free_ring(newchannel);

        return err;
}
EXPORT_SYMBOL_GPL(vmbus_open);

/*
 * 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 = kzalloc(sizeof(*info) +
                       sizeof(struct vmbus_channel_gpadl_teardown), GFP_KERNEL);
        if (!info)
                return -ENOMEM;

        init_completion(&info->waitevent);
        info->waiting_channel = channel;

        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);

        if (channel->rescind)
                goto post_msg_err;

        ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_gpadl_teardown),
                             true);

        trace_vmbus_teardown_gpadl(msg, ret);

        if (ret)
                goto post_msg_err;

        wait_for_completion(&info->waitevent);

post_msg_err:
        /*
         * If the channel has been rescinded;
         * we will be awakened by the rescind
         * handler; set the error code to zero so we don't leak memory.
         */
        if (channel->rescind)
                ret = 0;

        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);

void vmbus_reset_channel_cb(struct vmbus_channel *channel)
{
        unsigned long flags;

        /*
         * vmbus_on_event(), running in the per-channel 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, so here we must stop it
         * first.
         *
         * vmbus_chan_sched() might call the netvsc driver callback function
         * that ends up scheduling NAPI work that accesses the ring buffer.
         * At this point, we have to ensure that any such work is completed
         * and that the channel ring buffer is no longer being accessed, cf.
         * the calls to napi_disable() in netvsc_device_remove().
         */
        tasklet_disable(&channel->callback_event);

        /* See the inline comments in vmbus_chan_sched(). */
        spin_lock_irqsave(&channel->sched_lock, flags);
        channel->onchannel_callback = NULL;
        spin_unlock_irqrestore(&channel->sched_lock, flags);

        channel->sc_creation_callback = NULL;

        /* Re-enable tasklet for use on re-open */
        tasklet_enable(&channel->callback_event);
}

static int vmbus_close_internal(struct vmbus_channel *channel)
{
        struct vmbus_channel_close_channel *msg;
        int ret;

        vmbus_reset_channel_cb(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 disable 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)
                return -EINVAL;

        channel->state = CHANNEL_OPEN_STATE;

        /* 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),
                             true);

        trace_vmbus_close_internal(msg, ret);

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

        /* Tear down the gpadl for the channel's ring buffer */
        else if (channel->ringbuffer_gpadlhandle) {
                ret = vmbus_teardown_gpadl(channel,
                                           channel->ringbuffer_gpadlhandle);
                if (ret) {
                        pr_err("Close failed: teardown gpadl return %d\n", ret);
                        /*
                         * If we failed to teardown gpadl,
                         * it is perhaps better to leak memory.
                         */
                }

                channel->ringbuffer_gpadlhandle = 0;
        }

        if (!ret)
                vmbus_free_requestor(&channel->requestor);

        return ret;
}

/* disconnect ring - close all channels */
int vmbus_disconnect_ring(struct vmbus_channel *channel)
{
        struct vmbus_channel *cur_channel, *tmp;
        int ret;

        if (channel->primary_channel != NULL)
                return -EINVAL;

        list_for_each_entry_safe(cur_channel, tmp, &channel->sc_list, sc_list) {
                if (cur_channel->rescind)
                        wait_for_completion(&cur_channel->rescind_event);

                mutex_lock(&vmbus_connection.channel_mutex);
                if (vmbus_close_internal(cur_channel) == 0) {
                        vmbus_free_ring(cur_channel);

                        if (cur_channel->rescind)
                                hv_process_channel_removal(cur_channel);
                }
                mutex_unlock(&vmbus_connection.channel_mutex);
        }

        /*
         * Now close the primary.
         */
        mutex_lock(&vmbus_connection.channel_mutex);
        ret = vmbus_close_internal(channel);
        mutex_unlock(&vmbus_connection.channel_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(vmbus_disconnect_ring);

/*
 * vmbus_close - Close the specified channel
 */
void vmbus_close(struct vmbus_channel *channel)
{
        if (vmbus_disconnect_ring(channel) == 0)
                vmbus_free_ring(channel);
}
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 send the data from.

 * @bufferlen: Maximum size of what the buffer holds.
 * @requestid: Identifier of the request
 * @type: Type of packet that is being sent e.g. negotiate, time
 *        packet etc.
 * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
 *
 * 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)
{
        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;
        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 = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */

        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, requestid);
}
EXPORT_SYMBOL(vmbus_sendpacket);

/*
 * vmbus_sendpacket_pagebuffer - 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(struct vmbus_channel *channel,
                                struct hv_page_buffer pagebuffers[],
                                u32 pagecount, void *buffer, u32 bufferlen,
                                u64 requestid)
{
        int i;
        struct vmbus_channel_packet_page_buffer desc;
        u32 descsize;
        u32 packetlen;
        u32 packetlen_aligned;
        struct kvec 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 granularity */
        desc.length8 = (u16)(packetlen_aligned >> 3);
        desc.transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
        desc.reserved = 0;
        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, requestid);
}
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;

        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 granularity */
        desc->length8 = (u16)(packetlen_aligned >> 3);
        desc->transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
        desc->reserved = 0;
        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, requestid);
}
EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);

/**
 * __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 buffer can hold.
 * @buffer_actual_len: The actual size of the data after it was received.
 * @requestid: Identifier of the request
 * @raw: true means keep the vmpacket_descriptor header in the received data.
 *
 * 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);

/*
 * vmbus_next_request_id - Returns a new request id. It is also
 * the index at which the guest memory address is stored.
 * Uses a spin lock to avoid race conditions.
 * @rqstor: Pointer to the requestor struct
 * @rqst_add: Guest memory address to be stored in the array
 */
u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
{
        unsigned long flags;
        u64 current_id;
        const struct vmbus_channel *channel =
                container_of(rqstor, const struct vmbus_channel, requestor);

        /* Check rqstor has been initialized */
        if (!channel->rqstor_size)
                return VMBUS_NO_RQSTOR;

        spin_lock_irqsave(&rqstor->req_lock, flags);
        current_id = rqstor->next_request_id;

        /* Requestor array is full */
        if (current_id >= rqstor->size) {
                spin_unlock_irqrestore(&rqstor->req_lock, flags);
                return VMBUS_RQST_ERROR;
        }

        rqstor->next_request_id = rqstor->req_arr[current_id];
        rqstor->req_arr[current_id] = rqst_addr;

        /* The already held spin lock provides atomicity */
        bitmap_set(rqstor->req_bitmap, current_id, 1);

        spin_unlock_irqrestore(&rqstor->req_lock, flags);

        /*
         * Cannot return an ID of 0, which is reserved for an unsolicited
         * message from Hyper-V.
         */
        return current_id + 1;
}
EXPORT_SYMBOL_GPL(vmbus_next_request_id);

/*
 * vmbus_request_addr - Returns the memory address stored at @trans_id
 * in @rqstor. Uses a spin lock to avoid race conditions.
 * @rqstor: Pointer to the requestor struct
 * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
 * next request id.
 */
u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id)
{
        unsigned long flags;
        u64 req_addr;
        const struct vmbus_channel *channel =
                container_of(rqstor, const struct vmbus_channel, requestor);

        /* Check rqstor has been initialized */
        if (!channel->rqstor_size)
                return VMBUS_NO_RQSTOR;

        /* Hyper-V can send an unsolicited message with ID of 0 */
        if (!trans_id)
                return trans_id;

        spin_lock_irqsave(&rqstor->req_lock, flags);

        /* Data corresponding to trans_id is stored at trans_id - 1 */
        trans_id--;

        /* Invalid trans_id */
        if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap)) {
                spin_unlock_irqrestore(&rqstor->req_lock, flags);
                return VMBUS_RQST_ERROR;
        }

        req_addr = rqstor->req_arr[trans_id];
        rqstor->req_arr[trans_id] = rqstor->next_request_id;
        rqstor->next_request_id = trans_id;

        /* The already held spin lock provides atomicity */
        bitmap_clear(rqstor->req_bitmap, trans_id, 1);

        spin_unlock_irqrestore(&rqstor->req_lock, flags);
        return req_addr;
}
EXPORT_SYMBOL_GPL(vmbus_request_addr);