/*
 * 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/interrupt.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/hyperv.h>

#include "hyperv_vmbus.h"

static void init_vp_index(struct vmbus_channel *channel, u16 dev_type);

static const struct vmbus_device vmbus_devs[] = {
        /* IDE */
        { .dev_type = HV_IDE,
          HV_IDE_GUID,
          .perf_device = true,
        },

        /* SCSI */
        { .dev_type = HV_SCSI,
          HV_SCSI_GUID,
          .perf_device = true,
        },

        /* Fibre Channel */
        { .dev_type = HV_FC,
          HV_SYNTHFC_GUID,
          .perf_device = true,
        },

        /* Synthetic NIC */
        { .dev_type = HV_NIC,
          HV_NIC_GUID,
          .perf_device = true,
        },

        /* Network Direct */
        { .dev_type = HV_ND,
          HV_ND_GUID,
          .perf_device = true,
        },

        /* PCIE */
        { .dev_type = HV_PCIE,
          HV_PCIE_GUID,
          .perf_device = true,
        },

        /* Synthetic Frame Buffer */
        { .dev_type = HV_FB,
          HV_SYNTHVID_GUID,
          .perf_device = false,
        },

        /* Synthetic Keyboard */
        { .dev_type = HV_KBD,
          HV_KBD_GUID,
          .perf_device = false,
        },

        /* Synthetic MOUSE */
        { .dev_type = HV_MOUSE,
          HV_MOUSE_GUID,
          .perf_device = false,
        },

        /* KVP */
        { .dev_type = HV_KVP,
          HV_KVP_GUID,
          .perf_device = false,
        },

        /* Time Synch */
        { .dev_type = HV_TS,
          HV_TS_GUID,
          .perf_device = false,
        },

        /* Heartbeat */
        { .dev_type = HV_HB,
          HV_HEART_BEAT_GUID,
          .perf_device = false,
        },

        /* Shutdown */
        { .dev_type = HV_SHUTDOWN,
          HV_SHUTDOWN_GUID,
          .perf_device = false,
        },

        /* File copy */
        { .dev_type = HV_FCOPY,
          HV_FCOPY_GUID,
          .perf_device = false,
        },

        /* Backup */
        { .dev_type = HV_BACKUP,
          HV_VSS_GUID,
          .perf_device = false,
        },

        /* Dynamic Memory */
        { .dev_type = HV_DM,
          HV_DM_GUID,
          .perf_device = false,
        },

        /* Unknown GUID */
        { .dev_type = HV_UNKOWN,
          .perf_device = false,
        },
};

static const struct {
        uuid_le guid;
} vmbus_unsupported_devs[] = {
        { HV_AVMA1_GUID },
        { HV_AVMA2_GUID },
        { HV_RDV_GUID   },
};

static bool is_unsupported_vmbus_devs(const uuid_le *guid)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(vmbus_unsupported_devs); i++)
                if (!uuid_le_cmp(*guid, vmbus_unsupported_devs[i].guid))
                        return true;
        return false;
}

static u16 hv_get_dev_type(const struct vmbus_channel *channel)
{
        const uuid_le *guid = &channel->offermsg.offer.if_type;
        u16 i;

        if (is_hvsock_channel(channel) || is_unsupported_vmbus_devs(guid))
                return HV_UNKOWN;

        for (i = HV_IDE; i < HV_UNKOWN; i++) {
                if (!uuid_le_cmp(*guid, vmbus_devs[i].guid))
                        return i;
        }
        pr_info("Unknown GUID: %pUl\n", guid);
        return i;
}

/**
 * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
 * @icmsghdrp: Pointer to msg header structure
 * @icmsg_negotiate: Pointer to negotiate message structure
 * @buf: Raw buffer channel data
 *
 * @icmsghdrp is of type &struct icmsg_hdr.
 * @negop is of type &struct icmsg_negotiate.
 * Set up and fill in default negotiate response message.
 *
 * The fw_version specifies the  framework version that
 * we can support and srv_version specifies the service
 * version we can support.
 *
 * Mainly used by Hyper-V drivers.
 */
bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
                                struct icmsg_negotiate *negop, u8 *buf,
                                int fw_version, int srv_version)
{
        int icframe_major, icframe_minor;
        int icmsg_major, icmsg_minor;
        int fw_major, fw_minor;
        int srv_major, srv_minor;
        int i;
        bool found_match = false;

        icmsghdrp->icmsgsize = 0x10;
        fw_major = (fw_version >> 16);
        fw_minor = (fw_version & 0xFFFF);

        srv_major = (srv_version >> 16);
        srv_minor = (srv_version & 0xFFFF);

        negop = (struct icmsg_negotiate *)&buf[
                sizeof(struct vmbuspipe_hdr) +
                sizeof(struct icmsg_hdr)];

        icframe_major = negop->icframe_vercnt;
        icframe_minor = 0;

        icmsg_major = negop->icmsg_vercnt;
        icmsg_minor = 0;

        /*
         * Select the framework version number we will
         * support.
         */

        for (i = 0; i < negop->icframe_vercnt; i++) {
                if ((negop->icversion_data[i].major == fw_major) &&
                   (negop->icversion_data[i].minor == fw_minor)) {
                        icframe_major = negop->icversion_data[i].major;
                        icframe_minor = negop->icversion_data[i].minor;
                        found_match = true;
                }
        }

        if (!found_match)
                goto fw_error;

        found_match = false;

        for (i = negop->icframe_vercnt;
                 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
                if ((negop->icversion_data[i].major == srv_major) &&
                   (negop->icversion_data[i].minor == srv_minor)) {
                        icmsg_major = negop->icversion_data[i].major;
                        icmsg_minor = negop->icversion_data[i].minor;
                        found_match = true;
                }
        }

        /*
         * Respond with the framework and service
         * version numbers we can support.
         */

fw_error:
        if (!found_match) {
                negop->icframe_vercnt = 0;
                negop->icmsg_vercnt = 0;
        } else {
                negop->icframe_vercnt = 1;
                negop->icmsg_vercnt = 1;
        }

        negop->icversion_data[0].major = icframe_major;
        negop->icversion_data[0].minor = icframe_minor;
        negop->icversion_data[1].major = icmsg_major;
        negop->icversion_data[1].minor = icmsg_minor;
        return found_match;
}

EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);

/*
 * alloc_channel - Allocate and initialize a vmbus channel object
 */
static struct vmbus_channel *alloc_channel(void)
{
        struct vmbus_channel *channel;

        channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
        if (!channel)
                return NULL;

        channel->acquire_ring_lock = true;
        spin_lock_init(&channel->inbound_lock);
        spin_lock_init(&channel->lock);

        INIT_LIST_HEAD(&channel->sc_list);
        INIT_LIST_HEAD(&channel->percpu_list);

        return channel;
}

/*
 * free_channel - Release the resources used by the vmbus channel object
 */
static void free_channel(struct vmbus_channel *channel)
{
        kfree(channel);
}

static void percpu_channel_enq(void *arg)
{
        struct vmbus_channel *channel = arg;
        int cpu = smp_processor_id();

        list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
}

static void percpu_channel_deq(void *arg)
{
        struct vmbus_channel *channel = arg;

        list_del(&channel->percpu_list);
}


static void vmbus_release_relid(u32 relid)
{
        struct vmbus_channel_relid_released msg;

        memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
        msg.child_relid = relid;
        msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
        vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
}

void hv_event_tasklet_disable(struct vmbus_channel *channel)
{
        struct tasklet_struct *tasklet;
        tasklet = hv_context.event_dpc[channel->target_cpu];
        tasklet_disable(tasklet);
}

void hv_event_tasklet_enable(struct vmbus_channel *channel)
{
        struct tasklet_struct *tasklet;
        tasklet = hv_context.event_dpc[channel->target_cpu];
        tasklet_enable(tasklet);

        /* In case there is any pending event */
        tasklet_schedule(tasklet);
}

void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
{
        unsigned long flags;
        struct vmbus_channel *primary_channel;

        BUG_ON(!channel->rescind);
        BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));

        hv_event_tasklet_disable(channel);
        if (channel->target_cpu != get_cpu()) {
                put_cpu();
                smp_call_function_single(channel->target_cpu,
                                         percpu_channel_deq, channel, true);
        } else {
                percpu_channel_deq(channel);
                put_cpu();
        }
        hv_event_tasklet_enable(channel);

        if (channel->primary_channel == NULL) {
                list_del(&channel->listentry);

                primary_channel = channel;
        } else {
                primary_channel = channel->primary_channel;
                spin_lock_irqsave(&primary_channel->lock, flags);
                list_del(&channel->sc_list);
                primary_channel->num_sc--;
                spin_unlock_irqrestore(&primary_channel->lock, flags);
        }

        /*
         * We need to free the bit for init_vp_index() to work in the case
         * of sub-channel, when we reload drivers like hv_netvsc.
         */
        if (channel->affinity_policy == HV_LOCALIZED)
                cpumask_clear_cpu(channel->target_cpu,
                                  &primary_channel->alloced_cpus_in_node);

        vmbus_release_relid(relid);

        free_channel(channel);
}

void vmbus_free_channels(void)
{
        struct vmbus_channel *channel, *tmp;

        list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
                listentry) {
                /* hv_process_channel_removal() needs this */
                channel->rescind = true;

                vmbus_device_unregister(channel->device_obj);
        }
}

/*
 * vmbus_process_offer - Process the offer by creating a channel/device
 * associated with this offer
 */
static void vmbus_process_offer(struct vmbus_channel *newchannel)
{
        struct vmbus_channel *channel;
        bool fnew = true;
        unsigned long flags;
        u16 dev_type;
        int ret;

        /* Make sure this is a new offer */
        mutex_lock(&vmbus_connection.channel_mutex);

        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
                if (!uuid_le_cmp(channel->offermsg.offer.if_type,
                        newchannel->offermsg.offer.if_type) &&
                        !uuid_le_cmp(channel->offermsg.offer.if_instance,
                                newchannel->offermsg.offer.if_instance)) {
                        fnew = false;
                        break;
                }
        }

        if (fnew)
                list_add_tail(&newchannel->listentry,
                              &vmbus_connection.chn_list);

        mutex_unlock(&vmbus_connection.channel_mutex);

        if (!fnew) {
                /*
                 * Check to see if this is a sub-channel.
                 */
                if (newchannel->offermsg.offer.sub_channel_index != 0) {
                        /*
                         * Process the sub-channel.
                         */
                        newchannel->primary_channel = channel;
                        spin_lock_irqsave(&channel->lock, flags);
                        list_add_tail(&newchannel->sc_list, &channel->sc_list);
                        channel->num_sc++;
                        spin_unlock_irqrestore(&channel->lock, flags);
                } else
                        goto err_free_chan;
        }

        dev_type = hv_get_dev_type(newchannel);
        if (dev_type == HV_NIC)
                set_channel_signal_state(newchannel, HV_SIGNAL_POLICY_EXPLICIT);

        init_vp_index(newchannel, dev_type);

        hv_event_tasklet_disable(newchannel);
        if (newchannel->target_cpu != get_cpu()) {
                put_cpu();
                smp_call_function_single(newchannel->target_cpu,
                                         percpu_channel_enq,
                                         newchannel, true);
        } else {
                percpu_channel_enq(newchannel);
                put_cpu();
        }
        hv_event_tasklet_enable(newchannel);

        /*
         * This state is used to indicate a successful open
         * so that when we do close the channel normally, we
         * can cleanup properly
         */
        newchannel->state = CHANNEL_OPEN_STATE;

        if (!fnew) {
                if (channel->sc_creation_callback != NULL)
                        channel->sc_creation_callback(newchannel);
                return;
        }

        /*
         * Start the process of binding this offer to the driver
         * We need to set the DeviceObject field before calling
         * vmbus_child_dev_add()
         */
        newchannel->device_obj = vmbus_device_create(
                &newchannel->offermsg.offer.if_type,
                &newchannel->offermsg.offer.if_instance,
                newchannel);
        if (!newchannel->device_obj)
                goto err_deq_chan;

        newchannel->device_obj->device_id = dev_type;
        /*
         * Add the new device to the bus. This will kick off device-driver
         * binding which eventually invokes the device driver's AddDevice()
         * method.
         */
        mutex_lock(&vmbus_connection.channel_mutex);
        ret = vmbus_device_register(newchannel->device_obj);
        mutex_unlock(&vmbus_connection.channel_mutex);

        if (ret != 0) {
                pr_err("unable to add child device object (relid %d)\n",
                        newchannel->offermsg.child_relid);
                kfree(newchannel->device_obj);
                goto err_deq_chan;
        }
        return;

err_deq_chan:
        mutex_lock(&vmbus_connection.channel_mutex);
        list_del(&newchannel->listentry);
        mutex_unlock(&vmbus_connection.channel_mutex);

        hv_event_tasklet_disable(newchannel);
        if (newchannel->target_cpu != get_cpu()) {
                put_cpu();
                smp_call_function_single(newchannel->target_cpu,
                                         percpu_channel_deq, newchannel, true);
        } else {
                percpu_channel_deq(newchannel);
                put_cpu();
        }
        hv_event_tasklet_enable(newchannel);

        vmbus_release_relid(newchannel->offermsg.child_relid);

err_free_chan:
        free_channel(newchannel);
}

/*
 * We use this state to statically distribute the channel interrupt load.
 */
static int next_numa_node_id;

/*
 * Starting with Win8, we can statically distribute the incoming
 * channel interrupt load by binding a channel to VCPU.
 * We do this in a hierarchical fashion:
 * First distribute the primary channels across available NUMA nodes
 * and then distribute the subchannels amongst the CPUs in the NUMA
 * node assigned to the primary channel.
 *
 * For pre-win8 hosts or non-performance critical channels we assign the
 * first CPU in the first NUMA node.
 */
static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
{
        u32 cur_cpu;
        bool perf_chn = vmbus_devs[dev_type].perf_device;
        struct vmbus_channel *primary = channel->primary_channel;
        int next_node;
        struct cpumask available_mask;
        struct cpumask *alloced_mask;

        if ((vmbus_proto_version == VERSION_WS2008) ||
            (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
                /*
                 * Prior to win8, all channel interrupts are
                 * delivered on cpu 0.
                 * Also if the channel is not a performance critical
                 * channel, bind it to cpu 0.
                 */
                channel->numa_node = 0;
                channel->target_cpu = 0;
                channel->target_vp = hv_context.vp_index[0];
                return;
        }

        /*
         * Based on the channel affinity policy, we will assign the NUMA
         * nodes.
         */

        if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {
                while (true) {
                        next_node = next_numa_node_id++;
                        if (next_node == nr_node_ids) {
                                next_node = next_numa_node_id = 0;
                                continue;
                        }
                        if (cpumask_empty(cpumask_of_node(next_node)))
                                continue;
                        break;
                }
                channel->numa_node = next_node;
                primary = channel;
        }
        alloced_mask = &hv_context.hv_numa_map[primary->numa_node];

        if (cpumask_weight(alloced_mask) ==
            cpumask_weight(cpumask_of_node(primary->numa_node))) {
                /*
                 * We have cycled through all the CPUs in the node;
                 * reset the alloced map.
                 */
                cpumask_clear(alloced_mask);
        }

        cpumask_xor(&available_mask, alloced_mask,
                    cpumask_of_node(primary->numa_node));

        cur_cpu = -1;

        if (primary->affinity_policy == HV_LOCALIZED) {
                /*
                 * Normally Hyper-V host doesn't create more subchannels
                 * than there are VCPUs on the node but it is possible when not
                 * all present VCPUs on the node are initialized by guest.
                 * Clear the alloced_cpus_in_node to start over.
                 */
                if (cpumask_equal(&primary->alloced_cpus_in_node,
                                  cpumask_of_node(primary->numa_node)))
                        cpumask_clear(&primary->alloced_cpus_in_node);
        }

        while (true) {
                cur_cpu = cpumask_next(cur_cpu, &available_mask);
                if (cur_cpu >= nr_cpu_ids) {
                        cur_cpu = -1;
                        cpumask_copy(&available_mask,
                                     cpumask_of_node(primary->numa_node));
                        continue;
                }

                if (primary->affinity_policy == HV_LOCALIZED) {
                        /*
                         * NOTE: in the case of sub-channel, we clear the
                         * sub-channel related bit(s) in
                         * primary->alloced_cpus_in_node in
                         * hv_process_channel_removal(), so when we
                         * reload drivers like hv_netvsc in SMP guest, here
                         * we're able to re-allocate
                         * bit from primary->alloced_cpus_in_node.
                         */
                        if (!cpumask_test_cpu(cur_cpu,
                                              &primary->alloced_cpus_in_node)) {
                                cpumask_set_cpu(cur_cpu,
                                                &primary->alloced_cpus_in_node);
                                cpumask_set_cpu(cur_cpu, alloced_mask);
                                break;
                        }
                } else {
                        cpumask_set_cpu(cur_cpu, alloced_mask);
                        break;
                }
        }

        channel->target_cpu = cur_cpu;
        channel->target_vp = hv_context.vp_index[cur_cpu];
}

static void vmbus_wait_for_unload(void)
{
        int cpu;
        void *page_addr;
        struct hv_message *msg;
        struct vmbus_channel_message_header *hdr;
        u32 message_type;

        /*
         * CHANNELMSG_UNLOAD_RESPONSE is always delivered to the CPU which was
         * used for initial contact or to CPU0 depending on host version. When
         * we're crashing on a different CPU let's hope that IRQ handler on
         * the cpu which receives CHANNELMSG_UNLOAD_RESPONSE is still
         * functional and vmbus_unload_response() will complete
         * vmbus_connection.unload_event. If not, the last thing we can do is
         * read message pages for all CPUs directly.
         */
        while (1) {
                if (completion_done(&vmbus_connection.unload_event))
                        break;

                for_each_online_cpu(cpu) {
                        page_addr = hv_context.synic_message_page[cpu];
                        msg = (struct hv_message *)page_addr +
                                VMBUS_MESSAGE_SINT;

                        message_type = READ_ONCE(msg->header.message_type);
                        if (message_type == HVMSG_NONE)
                                continue;

                        hdr = (struct vmbus_channel_message_header *)
                                msg->u.payload;

                        if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE)
                                complete(&vmbus_connection.unload_event);

                        vmbus_signal_eom(msg, message_type);
                }

                mdelay(10);
        }

        /*
         * We're crashing and already got the UNLOAD_RESPONSE, cleanup all
         * maybe-pending messages on all CPUs to be able to receive new
         * messages after we reconnect.
         */
        for_each_online_cpu(cpu) {
                page_addr = hv_context.synic_message_page[cpu];
                msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
                msg->header.message_type = HVMSG_NONE;
        }
}

/*
 * vmbus_unload_response - Handler for the unload response.
 */
static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
{
        /*
         * This is a global event; just wakeup the waiting thread.
         * Once we successfully unload, we can cleanup the monitor state.
         */
        complete(&vmbus_connection.unload_event);
}

void vmbus_initiate_unload(bool crash)
{
        struct vmbus_channel_message_header hdr;

        /* Pre-Win2012R2 hosts don't support reconnect */
        if (vmbus_proto_version < VERSION_WIN8_1)
                return;

        init_completion(&vmbus_connection.unload_event);
        memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
        hdr.msgtype = CHANNELMSG_UNLOAD;
        vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header));

        /*
         * vmbus_initiate_unload() is also called on crash and the crash can be
         * happening in an interrupt context, where scheduling is impossible.
         */
        if (!crash)
                wait_for_completion(&vmbus_connection.unload_event);
        else
                vmbus_wait_for_unload();
}

/*
 * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
 *
 */
static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_offer_channel *offer;
        struct vmbus_channel *newchannel;

        offer = (struct vmbus_channel_offer_channel *)hdr;

        /* Allocate the channel object and save this offer. */
        newchannel = alloc_channel();
        if (!newchannel) {
                pr_err("Unable to allocate channel object\n");
                return;
        }

        /*
         * By default we setup state to enable batched
         * reading. A specific service can choose to
         * disable this prior to opening the channel.
         */
        newchannel->batched_reading = true;

        /*
         * Setup state for signalling the host.
         */
        newchannel->sig_event = (struct hv_input_signal_event *)
                                (ALIGN((unsigned long)
                                &newchannel->sig_buf,
                                HV_HYPERCALL_PARAM_ALIGN));

        newchannel->sig_event->connectionid.asu32 = 0;
        newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
        newchannel->sig_event->flag_number = 0;
        newchannel->sig_event->rsvdz = 0;

        if (vmbus_proto_version != VERSION_WS2008) {
                newchannel->is_dedicated_interrupt =
                                (offer->is_dedicated_interrupt != 0);
                newchannel->sig_event->connectionid.u.id =
                                offer->connection_id;
        }

        memcpy(&newchannel->offermsg, offer,
               sizeof(struct vmbus_channel_offer_channel));
        newchannel->monitor_grp = (u8)offer->monitorid / 32;
        newchannel->monitor_bit = (u8)offer->monitorid % 32;

        vmbus_process_offer(newchannel);
}

/*
 * vmbus_onoffer_rescind - Rescind offer handler.
 *
 * We queue a work item to process this offer synchronously
 */
static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_rescind_offer *rescind;
        struct vmbus_channel *channel;
        unsigned long flags;
        struct device *dev;

        rescind = (struct vmbus_channel_rescind_offer *)hdr;

        mutex_lock(&vmbus_connection.channel_mutex);
        channel = relid2channel(rescind->child_relid);

        if (channel == NULL) {
                /*
                 * This is very impossible, because in
                 * vmbus_process_offer(), we have already invoked
                 * vmbus_release_relid() on error.
                 */
                goto out;
        }

        spin_lock_irqsave(&channel->lock, flags);
        channel->rescind = true;
        spin_unlock_irqrestore(&channel->lock, flags);

        if (channel->device_obj) {
                if (channel->chn_rescind_callback) {
                        channel->chn_rescind_callback(channel);
                        goto out;
                }
                /*
                 * We will have to unregister this device from the
                 * driver core.
                 */
                dev = get_device(&channel->device_obj->device);
                if (dev) {
                        vmbus_device_unregister(channel->device_obj);
                        put_device(dev);
                }
        } else {
                hv_process_channel_removal(channel,
                        channel->offermsg.child_relid);
        }

out:
        mutex_unlock(&vmbus_connection.channel_mutex);
}

void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
{
        mutex_lock(&vmbus_connection.channel_mutex);

        BUG_ON(!is_hvsock_channel(channel));

        channel->rescind = true;
        vmbus_device_unregister(channel->device_obj);

        mutex_unlock(&vmbus_connection.channel_mutex);
}
EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);


/*
 * vmbus_onoffers_delivered -
 * This is invoked when all offers have been delivered.
 *
 * Nothing to do here.
 */
static void vmbus_onoffers_delivered(
                        struct vmbus_channel_message_header *hdr)
{
}

/*
 * vmbus_onopen_result - Open result handler.
 *
 * This is invoked when we received a response to our channel open request.
 * Find the matching request, copy the response and signal the requesting
 * thread.
 */
static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_open_result *result;
        struct vmbus_channel_msginfo *msginfo;
        struct vmbus_channel_message_header *requestheader;
        struct vmbus_channel_open_channel *openmsg;
        unsigned long flags;

        result = (struct vmbus_channel_open_result *)hdr;

        /*
         * Find the open msg, copy the result and signal/unblock the wait event
         */
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
                                msglistentry) {
                requestheader =
                        (struct vmbus_channel_message_header *)msginfo->msg;

                if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
                        openmsg =
                        (struct vmbus_channel_open_channel *)msginfo->msg;
                        if (openmsg->child_relid == result->child_relid &&
                            openmsg->openid == result->openid) {
                                memcpy(&msginfo->response.open_result,
                                       result,
                                       sizeof(
                                        struct vmbus_channel_open_result));
                                complete(&msginfo->waitevent);
                                break;
                        }
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}

/*
 * vmbus_ongpadl_created - GPADL created handler.
 *
 * This is invoked when we received a response to our gpadl create request.
 * Find the matching request, copy the response and signal the requesting
 * thread.
 */
static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_gpadl_created *gpadlcreated;
        struct vmbus_channel_msginfo *msginfo;
        struct vmbus_channel_message_header *requestheader;
        struct vmbus_channel_gpadl_header *gpadlheader;
        unsigned long flags;

        gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;

        /*
         * Find the establish msg, copy the result and signal/unblock the wait
         * event
         */
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
                                msglistentry) {
                requestheader =
                        (struct vmbus_channel_message_header *)msginfo->msg;

                if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
                        gpadlheader =
                        (struct vmbus_channel_gpadl_header *)requestheader;

                        if ((gpadlcreated->child_relid ==
                             gpadlheader->child_relid) &&
                            (gpadlcreated->gpadl == gpadlheader->gpadl)) {
                                memcpy(&msginfo->response.gpadl_created,
                                       gpadlcreated,
                                       sizeof(
                                        struct vmbus_channel_gpadl_created));
                                complete(&msginfo->waitevent);
                                break;
                        }
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}

/*
 * vmbus_ongpadl_torndown - GPADL torndown handler.
 *
 * This is invoked when we received a response to our gpadl teardown request.
 * Find the matching request, copy the response and signal the requesting
 * thread.
 */
static void vmbus_ongpadl_torndown(
                        struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_gpadl_torndown *gpadl_torndown;
        struct vmbus_channel_msginfo *msginfo;
        struct vmbus_channel_message_header *requestheader;
        struct vmbus_channel_gpadl_teardown *gpadl_teardown;
        unsigned long flags;

        gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;

        /*
         * Find the open msg, copy the result and signal/unblock the wait event
         */
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
                                msglistentry) {
                requestheader =
                        (struct vmbus_channel_message_header *)msginfo->msg;

                if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
                        gpadl_teardown =
                        (struct vmbus_channel_gpadl_teardown *)requestheader;

                        if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
                                memcpy(&msginfo->response.gpadl_torndown,
                                       gpadl_torndown,
                                       sizeof(

                                        struct vmbus_channel_gpadl_torndown));
                                complete(&msginfo->waitevent);
                                break;
                        }
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}

/*
 * vmbus_onversion_response - Version response handler
 *
 * This is invoked when we received a response to our initiate contact request.
 * Find the matching request, copy the response and signal the requesting
 * thread.
 */
static void vmbus_onversion_response(
                struct vmbus_channel_message_header *hdr)
{
        struct vmbus_channel_msginfo *msginfo;
        struct vmbus_channel_message_header *requestheader;
        struct vmbus_channel_version_response *version_response;
        unsigned long flags;

        version_response = (struct vmbus_channel_version_response *)hdr;
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);

        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
                                msglistentry) {
                requestheader =
                        (struct vmbus_channel_message_header *)msginfo->msg;

                if (requestheader->msgtype ==
                    CHANNELMSG_INITIATE_CONTACT) {
                        memcpy(&msginfo->response.version_response,
                              version_response,
                              sizeof(struct vmbus_channel_version_response));
                        complete(&msginfo->waitevent);
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}

/* Channel message dispatch table */
struct vmbus_channel_message_table_entry
        channel_message_table[CHANNELMSG_COUNT] = {
        {CHANNELMSG_INVALID,                    0, NULL},
        {CHANNELMSG_OFFERCHANNEL,               0, vmbus_onoffer},
        {CHANNELMSG_RESCIND_CHANNELOFFER,       0, vmbus_onoffer_rescind},
        {CHANNELMSG_REQUESTOFFERS,              0, NULL},
        {CHANNELMSG_ALLOFFERS_DELIVERED,        1, vmbus_onoffers_delivered},
        {CHANNELMSG_OPENCHANNEL,                0, NULL},
        {CHANNELMSG_OPENCHANNEL_RESULT,         1, vmbus_onopen_result},
        {CHANNELMSG_CLOSECHANNEL,               0, NULL},
        {CHANNELMSG_GPADL_HEADER,               0, NULL},
        {CHANNELMSG_GPADL_BODY,                 0, NULL},
        {CHANNELMSG_GPADL_CREATED,              1, vmbus_ongpadl_created},
        {CHANNELMSG_GPADL_TEARDOWN,             0, NULL},
        {CHANNELMSG_GPADL_TORNDOWN,             1, vmbus_ongpadl_torndown},
        {CHANNELMSG_RELID_RELEASED,             0, NULL},
        {CHANNELMSG_INITIATE_CONTACT,           0, NULL},
        {CHANNELMSG_VERSION_RESPONSE,           1, vmbus_onversion_response},
        {CHANNELMSG_UNLOAD,                     0, NULL},
        {CHANNELMSG_UNLOAD_RESPONSE,            1, vmbus_unload_response},
        {CHANNELMSG_18,                         0, NULL},
        {CHANNELMSG_19,                         0, NULL},
        {CHANNELMSG_20,                         0, NULL},
        {CHANNELMSG_TL_CONNECT_REQUEST,         0, NULL},
};

/*
 * vmbus_onmessage - Handler for channel protocol messages.
 *
 * This is invoked in the vmbus worker thread context.
 */
void vmbus_onmessage(void *context)
{
        struct hv_message *msg = context;
        struct vmbus_channel_message_header *hdr;
        int size;

        hdr = (struct vmbus_channel_message_header *)msg->u.payload;
        size = msg->header.payload_size;

        if (hdr->msgtype >= CHANNELMSG_COUNT) {
                pr_err("Received invalid channel message type %d size %d\n",
                           hdr->msgtype, size);
                print_hex_dump_bytes("", DUMP_PREFIX_NONE,
                                     (unsigned char *)msg->u.payload, size);
                return;
        }

        if (channel_message_table[hdr->msgtype].message_handler)
                channel_message_table[hdr->msgtype].message_handler(hdr);
        else
                pr_err("Unhandled channel message type %d\n", hdr->msgtype);
}

/*
 * vmbus_request_offers - Send a request to get all our pending offers.
 */
int vmbus_request_offers(void)
{
        struct vmbus_channel_message_header *msg;
        struct vmbus_channel_msginfo *msginfo;
        int ret;

        msginfo = kmalloc(sizeof(*msginfo) +
                          sizeof(struct vmbus_channel_message_header),
                          GFP_KERNEL);
        if (!msginfo)
                return -ENOMEM;

        msg = (struct vmbus_channel_message_header *)msginfo->msg;

        msg->msgtype = CHANNELMSG_REQUESTOFFERS;


        ret = vmbus_post_msg(msg,
                               sizeof(struct vmbus_channel_message_header));
        if (ret != 0) {
                pr_err("Unable to request offers - %d\n", ret);

                goto cleanup;
        }

cleanup:
        kfree(msginfo);

        return ret;
}

/*
 * Retrieve the (sub) channel on which to send an outgoing request.
 * When a primary channel has multiple sub-channels, we try to
 * distribute the load equally amongst all available channels.
 */
struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
{
        struct list_head *cur, *tmp;
        int cur_cpu;
        struct vmbus_channel *cur_channel;
        struct vmbus_channel *outgoing_channel = primary;
        int next_channel;
        int i = 1;

        if (list_empty(&primary->sc_list))
                return outgoing_channel;

        next_channel = primary->next_oc++;

        if (next_channel > (primary->num_sc)) {
                primary->next_oc = 0;
                return outgoing_channel;
        }

        cur_cpu = hv_context.vp_index[get_cpu()];
        put_cpu();
        list_for_each_safe(cur, tmp, &primary->sc_list) {
                cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
                if (cur_channel->state != CHANNEL_OPENED_STATE)
                        continue;

                if (cur_channel->target_vp == cur_cpu)
                        return cur_channel;

                if (i == next_channel)
                        return cur_channel;

                i++;
        }

        return outgoing_channel;
}
EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel);

static void invoke_sc_cb(struct vmbus_channel *primary_channel)
{
        struct list_head *cur, *tmp;
        struct vmbus_channel *cur_channel;

        if (primary_channel->sc_creation_callback == NULL)
                return;

        list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
                cur_channel = list_entry(cur, struct vmbus_channel, sc_list);

                primary_channel->sc_creation_callback(cur_channel);
        }
}

void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
                                void (*sc_cr_cb)(struct vmbus_channel *new_sc))
{
        primary_channel->sc_creation_callback = sc_cr_cb;
}
EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);

bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
{
        bool ret;

        ret = !list_empty(&primary->sc_list);

        if (ret) {
                /*
                 * Invoke the callback on sub-channel creation.
                 * This will present a uniform interface to the
                 * clients.
                 */
                invoke_sc_cb(primary);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);

void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
                void (*chn_rescind_cb)(struct vmbus_channel *))
{
        channel->chn_rescind_callback = chn_rescind_cb;
}
EXPORT_SYMBOL_GPL(vmbus_set_chn_rescind_callback);