Merge tag 'io_uring-5.11-2021-01-16' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / hv / channel_mgmt.c

// 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/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/cpu.h>
#include <linux/hyperv.h>
#include <asm/mshyperv.h>

#include "hyperv_vmbus.h"

static void init_vp_index(struct vmbus_channel *channel);

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 = false,
        },

        /* 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_UNKNOWN,
          .perf_device = false,
        },
};

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

/*
 * The rescinded channel may be blocked waiting for a response from the host;
 * take care of that.
 */
static void vmbus_rescind_cleanup(struct vmbus_channel *channel)
{
        struct vmbus_channel_msginfo *msginfo;
        unsigned long flags;


        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
        channel->rescind = true;
        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
                                msglistentry) {

                if (msginfo->waiting_channel == channel) {
                        complete(&msginfo->waitevent);
                        break;
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}

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

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

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

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

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

/**
 * vmbus_prep_negotiate_resp() - Create default response for Negotiate message
 * @icmsghdrp: Pointer to msg header structure
 * @buf: Raw buffer channel data
 * @fw_version: The framework versions we can support.
 * @fw_vercnt: The size of @fw_version.
 * @srv_version: The service versions we can support.
 * @srv_vercnt: The size of @srv_version.
 * @nego_fw_version: The selected framework version.
 * @nego_srv_version: The selected service version.
 *
 * Note: Versions are given in decreasing order.
 *
 * Set up and fill in default negotiate response message.
 * Mainly used by Hyper-V drivers.
 */
bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
                                u8 *buf, const int *fw_version, int fw_vercnt,
                                const int *srv_version, int srv_vercnt,
                                int *nego_fw_version, int *nego_srv_version)
{
        int icframe_major, icframe_minor;
        int icmsg_major, icmsg_minor;
        int fw_major, fw_minor;
        int srv_major, srv_minor;
        int i, j;
        bool found_match = false;
        struct icmsg_negotiate *negop;

        icmsghdrp->icmsgsize = 0x10;
        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 < fw_vercnt; i++) {
                fw_major = (fw_version[i] >> 16);
                fw_minor = (fw_version[i] & 0xFFFF);

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

                if (found_match)
                        break;
        }

        if (!found_match)
                goto fw_error;

        found_match = false;

        for (i = 0; i < srv_vercnt; i++) {
                srv_major = (srv_version[i] >> 16);
                srv_minor = (srv_version[i] & 0xFFFF);

                for (j = negop->icframe_vercnt;
                        (j < negop->icframe_vercnt + negop->icmsg_vercnt);
                        j++) {

                        if ((negop->icversion_data[j].major == srv_major) &&
                                (negop->icversion_data[j].minor == srv_minor)) {

                                icmsg_major = negop->icversion_data[j].major;
                                icmsg_minor = negop->icversion_data[j].minor;
                                found_match = true;
                                break;
                        }
                }

                if (found_match)
                        break;
        }

        /*
         * 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;
        }

        if (nego_fw_version)
                *nego_fw_version = (icframe_major << 16) | icframe_minor;

        if (nego_srv_version)
                *nego_srv_version = (icmsg_major << 16) | icmsg_minor;

        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;

        spin_lock_init(&channel->sched_lock);
        init_completion(&channel->rescind_event);

        INIT_LIST_HEAD(&channel->sc_list);

        tasklet_init(&channel->callback_event,
                     vmbus_on_event, (unsigned long)channel);

        hv_ringbuffer_pre_init(channel);

        return channel;
}

/*
 * free_channel - Release the resources used by the vmbus channel object
 */
static void free_channel(struct vmbus_channel *channel)
{
        tasklet_kill(&channel->callback_event);
        vmbus_remove_channel_attr_group(channel);

        kobject_put(&channel->kobj);
}

void vmbus_channel_map_relid(struct vmbus_channel *channel)
{
        if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
                return;
        /*
         * The mapping of the channel's relid is visible from the CPUs that
         * execute vmbus_chan_sched() by the time that vmbus_chan_sched() will
         * execute:
         *
         *  (a) In the "normal (i.e., not resuming from hibernation)" path,
         *      the full barrier in smp_store_mb() guarantees that the store
         *      is propagated to all CPUs before the add_channel_work work
         *      is queued.  In turn, add_channel_work is queued before the
         *      channel's ring buffer is allocated/initialized and the
         *      OPENCHANNEL message for the channel is sent in vmbus_open().
         *      Hyper-V won't start sending the interrupts for the channel
         *      before the OPENCHANNEL message is acked.  The memory barrier
         *      in vmbus_chan_sched() -> sync_test_and_clear_bit() ensures
         *      that vmbus_chan_sched() must find the channel's relid in
         *      recv_int_page before retrieving the channel pointer from the
         *      array of channels.
         *
         *  (b) In the "resuming from hibernation" path, the smp_store_mb()
         *      guarantees that the store is propagated to all CPUs before
         *      the VMBus connection is marked as ready for the resume event
         *      (cf. check_ready_for_resume_event()).  The interrupt handler
         *      of the VMBus driver and vmbus_chan_sched() can not run before
         *      vmbus_bus_resume() has completed execution (cf. resume_noirq).
         */
        smp_store_mb(
                vmbus_connection.channels[channel->offermsg.child_relid],
                channel);
}

void vmbus_channel_unmap_relid(struct vmbus_channel *channel)
{
        if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
                return;
        WRITE_ONCE(
                vmbus_connection.channels[channel->offermsg.child_relid],
                NULL);
}

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

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

        trace_vmbus_release_relid(&msg, ret);
}

void hv_process_channel_removal(struct vmbus_channel *channel)
{
        lockdep_assert_held(&vmbus_connection.channel_mutex);
        BUG_ON(!channel->rescind);

        /*
         * hv_process_channel_removal() could find INVALID_RELID only for
         * hv_sock channels.  See the inline comments in vmbus_onoffer().
         */
        WARN_ON(channel->offermsg.child_relid == INVALID_RELID &&
                !is_hvsock_channel(channel));

        /*
         * Upon suspend, an in-use hv_sock channel is removed from the array of
         * channels and the relid is invalidated.  After hibernation, when the
         * user-space appplication destroys the channel, it's unnecessary and
         * unsafe to remove the channel from the array of channels.  See also
         * the inline comments before the call of vmbus_release_relid() below.
         */
        if (channel->offermsg.child_relid != INVALID_RELID)
                vmbus_channel_unmap_relid(channel);

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

        /*
         * If this is a "perf" channel, updates the hv_numa_map[] masks so that
         * init_vp_index() can (re-)use the CPU.
         */
        if (hv_is_perf_channel(channel))
                hv_clear_alloced_cpu(channel->target_cpu);

        /*
         * Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
         * the relid is invalidated; after hibernation, when the user-space app
         * destroys the channel, the relid is INVALID_RELID, and in this case
         * it's unnecessary and unsafe to release the old relid, since the same
         * relid can refer to a completely different channel now.
         */
        if (channel->offermsg.child_relid != INVALID_RELID)
                vmbus_release_relid(channel->offermsg.child_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);
        }
}

/* Note: the function can run concurrently for primary/sub channels. */
static void vmbus_add_channel_work(struct work_struct *work)
{
        struct vmbus_channel *newchannel =
                container_of(work, struct vmbus_channel, add_channel_work);
        struct vmbus_channel *primary_channel = newchannel->primary_channel;
        int ret;

        /*
         * 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 (primary_channel != NULL) {
                /* newchannel is a sub-channel. */
                struct hv_device *dev = primary_channel->device_obj;

                if (vmbus_add_channel_kobj(dev, newchannel))
                        goto err_deq_chan;

                if (primary_channel->sc_creation_callback != NULL)
                        primary_channel->sc_creation_callback(newchannel);

                newchannel->probe_done = true;
                return;
        }

        /*
         * Start the process of binding the primary channel to the driver
         */
        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 = newchannel->device_id;
        /*
         * Add the new device to the bus. This will kick off device-driver
         * binding which eventually invokes the device driver's AddDevice()
         * method.
         */
        ret = vmbus_device_register(newchannel->device_obj);

        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;
        }

        newchannel->probe_done = true;
        return;

err_deq_chan:
        mutex_lock(&vmbus_connection.channel_mutex);

        /*
         * We need to set the flag, otherwise
         * vmbus_onoffer_rescind() can be blocked.
         */
        newchannel->probe_done = true;

        if (primary_channel == NULL)
                list_del(&newchannel->listentry);
        else
                list_del(&newchannel->sc_list);

        /* vmbus_process_offer() has mapped the channel. */
        vmbus_channel_unmap_relid(newchannel);

        mutex_unlock(&vmbus_connection.channel_mutex);

        vmbus_release_relid(newchannel->offermsg.child_relid);

        free_channel(newchannel);
}

/*
 * 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;
        struct workqueue_struct *wq;
        bool fnew = true;

        /*
         * Synchronize vmbus_process_offer() and CPU hotplugging:
         *
         * CPU1                         CPU2
         *
         * [vmbus_process_offer()]      [Hot removal of the CPU]
         *
         * CPU_READ_LOCK                CPUS_WRITE_LOCK
         * LOAD cpu_online_mask         SEARCH chn_list
         * STORE target_cpu             LOAD target_cpu
         * INSERT chn_list              STORE cpu_online_mask
         * CPUS_READ_UNLOCK             CPUS_WRITE_UNLOCK
         *
         * Forbids: CPU1's LOAD from *not* seing CPU2's STORE &&
         *              CPU2's SEARCH from *not* seeing CPU1's INSERT
         *
         * Forbids: CPU2's SEARCH from seeing CPU1's INSERT &&
         *              CPU2's LOAD from *not* seing CPU1's STORE
         */
        cpus_read_lock();

        /*
         * Serializes the modifications of the chn_list list as well as
         * the accesses to next_numa_node_id in init_vp_index().
         */
        mutex_lock(&vmbus_connection.channel_mutex);

        init_vp_index(newchannel);

        /* Remember the channels that should be cleaned up upon suspend. */
        if (is_hvsock_channel(newchannel) || is_sub_channel(newchannel))
                atomic_inc(&vmbus_connection.nr_chan_close_on_suspend);

        /*
         * Now that we have acquired the channel_mutex,
         * we can release the potentially racing rescind thread.
         */
        atomic_dec(&vmbus_connection.offer_in_progress);

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

        if (fnew) {
                list_add_tail(&newchannel->listentry,
                              &vmbus_connection.chn_list);
        } else {
                /*
                 * Check to see if this is a valid sub-channel.
                 */
                if (newchannel->offermsg.offer.sub_channel_index == 0) {
                        mutex_unlock(&vmbus_connection.channel_mutex);
                        /*
                         * Don't call free_channel(), because newchannel->kobj
                         * is not initialized yet.
                         */
                        kfree(newchannel);
                        WARN_ON_ONCE(1);
                        return;
                }
                /*
                 * Process the sub-channel.
                 */
                newchannel->primary_channel = channel;
                list_add_tail(&newchannel->sc_list, &channel->sc_list);
        }

        vmbus_channel_map_relid(newchannel);

        mutex_unlock(&vmbus_connection.channel_mutex);
        cpus_read_unlock();

        /*
         * vmbus_process_offer() mustn't call channel->sc_creation_callback()
         * directly for sub-channels, because sc_creation_callback() ->
         * vmbus_open() may never get the host's response to the
         * OPEN_CHANNEL message (the host may rescind a channel at any time,
         * e.g. in the case of hot removing a NIC), and vmbus_onoffer_rescind()
         * may not wake up the vmbus_open() as it's blocked due to a non-zero
         * vmbus_connection.offer_in_progress, and finally we have a deadlock.
         *
         * The above is also true for primary channels, if the related device
         * drivers use sync probing mode by default.
         *
         * And, usually the handling of primary channels and sub-channels can
         * depend on each other, so we should offload them to different
         * workqueues to avoid possible deadlock, e.g. in sync-probing mode,
         * NIC1's netvsc_subchan_work() can race with NIC2's netvsc_probe() ->
         * rtnl_lock(), and causes deadlock: the former gets the rtnl_lock
         * and waits for all the sub-channels to appear, but the latter
         * can't get the rtnl_lock and this blocks the handling of
         * sub-channels.
         */
        INIT_WORK(&newchannel->add_channel_work, vmbus_add_channel_work);
        wq = fnew ? vmbus_connection.handle_primary_chan_wq :
                    vmbus_connection.handle_sub_chan_wq;
        queue_work(wq, &newchannel->add_channel_work);
}

/*
 * 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.
 *
 * For pre-win8 hosts or non-performance critical channels we assign the
 * VMBUS_CONNECT_CPU.
 *
 * Starting with win8, performance critical channels will be distributed
 * evenly among all the available NUMA nodes.  Once the node is assigned,
 * we will assign the CPU based on a simple round robin scheme.
 */
static void init_vp_index(struct vmbus_channel *channel)
{
        bool perf_chn = hv_is_perf_channel(channel);
        cpumask_var_t available_mask;
        struct cpumask *alloced_mask;
        u32 target_cpu;
        int numa_node;

        if ((vmbus_proto_version == VERSION_WS2008) ||
            (vmbus_proto_version == VERSION_WIN7) || (!perf_chn) ||
            !alloc_cpumask_var(&available_mask, GFP_KERNEL)) {
                /*
                 * Prior to win8, all channel interrupts are
                 * delivered on VMBUS_CONNECT_CPU.
                 * Also if the channel is not a performance critical
                 * channel, bind it to VMBUS_CONNECT_CPU.
                 * In case alloc_cpumask_var() fails, bind it to
                 * VMBUS_CONNECT_CPU.
                 */
                channel->target_cpu = VMBUS_CONNECT_CPU;
                if (perf_chn)
                        hv_set_alloced_cpu(VMBUS_CONNECT_CPU);
                return;
        }

        while (true) {
                numa_node = next_numa_node_id++;
                if (numa_node == nr_node_ids) {
                        next_numa_node_id = 0;
                        continue;
                }
                if (cpumask_empty(cpumask_of_node(numa_node)))
                        continue;
                break;
        }
        alloced_mask = &hv_context.hv_numa_map[numa_node];

        if (cpumask_weight(alloced_mask) ==
            cpumask_weight(cpumask_of_node(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(numa_node));

        target_cpu = cpumask_first(available_mask);
        cpumask_set_cpu(target_cpu, alloced_mask);

        channel->target_cpu = target_cpu;

        free_cpumask_var(available_mask);
}

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, i;

        /*
         * 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.
         *
         * Wait no more than 10 seconds so that the panic path can't get
         * hung forever in case the response message isn't seen.
         */
        for (i = 0; i < 1000; i++) {
                if (completion_done(&vmbus_connection.unload_event))
                        break;

                for_each_online_cpu(cpu) {
                        struct hv_per_cpu_context *hv_cpu
                                = per_cpu_ptr(hv_context.cpu_context, cpu);

                        page_addr = hv_cpu->synic_message_page;
                        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) {
                struct hv_per_cpu_context *hv_cpu
                        = per_cpu_ptr(hv_context.cpu_context, cpu);

                page_addr = hv_cpu->synic_message_page;
                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;

        if (xchg(&vmbus_connection.conn_state, DISCONNECTED) == DISCONNECTED)
                return;

        /* 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),
                       !crash);

        /*
         * 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();
}

static void check_ready_for_resume_event(void)
{
        /*
         * If all the old primary channels have been fixed up, then it's safe
         * to resume.
         */
        if (atomic_dec_and_test(&vmbus_connection.nr_chan_fixup_on_resume))
                complete(&vmbus_connection.ready_for_resume_event);
}

static void vmbus_setup_channel_state(struct vmbus_channel *channel,
                                      struct vmbus_channel_offer_channel *offer)
{
        /*
         * Setup state for signalling the host.
         */
        channel->sig_event = VMBUS_EVENT_CONNECTION_ID;

        if (vmbus_proto_version != VERSION_WS2008) {
                channel->is_dedicated_interrupt =
                                (offer->is_dedicated_interrupt != 0);
                channel->sig_event = offer->connection_id;
        }

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

/*
 * find_primary_channel_by_offer - Get the channel object given the new offer.
 * This is only used in the resume path of hibernation.
 */
static struct vmbus_channel *
find_primary_channel_by_offer(const struct vmbus_channel_offer_channel *offer)
{
        struct vmbus_channel *channel = NULL, *iter;
        const guid_t *inst1, *inst2;

        /* Ignore sub-channel offers. */
        if (offer->offer.sub_channel_index != 0)
                return NULL;

        mutex_lock(&vmbus_connection.channel_mutex);

        list_for_each_entry(iter, &vmbus_connection.chn_list, listentry) {
                inst1 = &iter->offermsg.offer.if_instance;
                inst2 = &offer->offer.if_instance;

                if (guid_equal(inst1, inst2)) {
                        channel = iter;
                        break;
                }
        }

        mutex_unlock(&vmbus_connection.channel_mutex);

        return channel;
}

/*
 * 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 *oldchannel, *newchannel;
        size_t offer_sz;

        offer = (struct vmbus_channel_offer_channel *)hdr;

        trace_vmbus_onoffer(offer);

        oldchannel = find_primary_channel_by_offer(offer);

        if (oldchannel != NULL) {
                /*
                 * We're resuming from hibernation: all the sub-channel and
                 * hv_sock channels we had before the hibernation should have
                 * been cleaned up, and now we must be seeing a re-offered
                 * primary channel that we had before the hibernation.
                 */

                /*
                 * { Initially: channel relid = INVALID_RELID,
                 *              channels[valid_relid] = NULL }
                 *
                 * CPU1                                 CPU2
                 *
                 * [vmbus_onoffer()]                    [vmbus_device_release()]
                 *
                 * LOCK channel_mutex                   LOCK channel_mutex
                 * STORE channel relid = valid_relid    LOAD r1 = channel relid
                 * MAP_RELID channel                    if (r1 != INVALID_RELID)
                 * UNLOCK channel_mutex                   UNMAP_RELID channel
                 *                                      UNLOCK channel_mutex
                 *
                 * Forbids: r1 == valid_relid &&
                 *              channels[valid_relid] == channel
                 *
                 * Note.  r1 can be INVALID_RELID only for an hv_sock channel.
                 * None of the hv_sock channels which were present before the
                 * suspend are re-offered upon the resume.  See the WARN_ON()
                 * in hv_process_channel_removal().
                 */
                mutex_lock(&vmbus_connection.channel_mutex);

                atomic_dec(&vmbus_connection.offer_in_progress);

                WARN_ON(oldchannel->offermsg.child_relid != INVALID_RELID);
                /* Fix up the relid. */
                oldchannel->offermsg.child_relid = offer->child_relid;

                offer_sz = sizeof(*offer);
                if (memcmp(offer, &oldchannel->offermsg, offer_sz) != 0) {
                        /*
                         * This is not an error, since the host can also change
                         * the other field(s) of the offer, e.g. on WS RS5
                         * (Build 17763), the offer->connection_id of the
                         * Mellanox VF vmbus device can change when the host
                         * reoffers the device upon resume.
                         */
                        pr_debug("vmbus offer changed: relid=%d\n",
                                 offer->child_relid);

                        print_hex_dump_debug("Old vmbus offer: ",
                                             DUMP_PREFIX_OFFSET, 16, 4,
                                             &oldchannel->offermsg, offer_sz,
                                             false);
                        print_hex_dump_debug("New vmbus offer: ",
                                             DUMP_PREFIX_OFFSET, 16, 4,
                                             offer, offer_sz, false);

                        /* Fix up the old channel. */
                        vmbus_setup_channel_state(oldchannel, offer);
                }

                /* Add the channel back to the array of channels. */
                vmbus_channel_map_relid(oldchannel);
                check_ready_for_resume_event();

                mutex_unlock(&vmbus_connection.channel_mutex);
                return;
        }

        /* Allocate the channel object and save this offer. */
        newchannel = alloc_channel();
        if (!newchannel) {
                vmbus_release_relid(offer->child_relid);
                atomic_dec(&vmbus_connection.offer_in_progress);
                pr_err("Unable to allocate channel object\n");
                return;
        }

        vmbus_setup_channel_state(newchannel, offer);

        vmbus_process_offer(newchannel);
}

static void check_ready_for_suspend_event(void)
{
        /*
         * If all the sub-channels or hv_sock channels have been cleaned up,
         * then it's safe to suspend.
         */
        if (atomic_dec_and_test(&vmbus_connection.nr_chan_close_on_suspend))
                complete(&vmbus_connection.ready_for_suspend_event);
}

/*
 * 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;
        struct device *dev;
        bool clean_up_chan_for_suspend;

        rescind = (struct vmbus_channel_rescind_offer *)hdr;

        trace_vmbus_onoffer_rescind(rescind);

        /*
         * The offer msg and the corresponding rescind msg
         * from the host are guranteed to be ordered -
         * offer comes in first and then the rescind.
         * Since we process these events in work elements,
         * and with preemption, we may end up processing
         * the events out of order.  We rely on the synchronization
         * provided by offer_in_progress and by channel_mutex for
         * ordering these events:
         *
         * { Initially: offer_in_progress = 1 }
         *
         * CPU1                         CPU2
         *
         * [vmbus_onoffer()]            [vmbus_onoffer_rescind()]
         *
         * LOCK channel_mutex           WAIT_ON offer_in_progress == 0
         * DECREMENT offer_in_progress  LOCK channel_mutex
         * STORE channels[]             LOAD channels[]
         * UNLOCK channel_mutex         UNLOCK channel_mutex
         *
         * Forbids: CPU2's LOAD from *not* seeing CPU1's STORE
         */

        while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
                /*
                 * We wait here until any channel offer is currently
                 * being processed.
                 */
                msleep(1);
        }

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

        if (channel == NULL) {
                /*
                 * We failed in processing the offer message;
                 * we would have cleaned up the relid in that
                 * failure path.
                 */
                return;
        }

        clean_up_chan_for_suspend = is_hvsock_channel(channel) ||
                                    is_sub_channel(channel);
        /*
         * Before setting channel->rescind in vmbus_rescind_cleanup(), we
         * should make sure the channel callback is not running any more.
         */
        vmbus_reset_channel_cb(channel);

        /*
         * Now wait for offer handling to complete.
         */
        vmbus_rescind_cleanup(channel);
        while (READ_ONCE(channel->probe_done) == false) {
                /*
                 * We wait here until any channel offer is currently
                 * being processed.
                 */
                msleep(1);
        }

        /*
         * At this point, the rescind handling can proceed safely.
         */

        if (channel->device_obj) {
                if (channel->chn_rescind_callback) {
                        channel->chn_rescind_callback(channel);

                        if (clean_up_chan_for_suspend)
                                check_ready_for_suspend_event();

                        return;
                }
                /*
                 * 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);
                }
        }
        if (channel->primary_channel != NULL) {
                /*
                 * Sub-channel is being rescinded. Following is the channel
                 * close sequence when initiated from the driveri (refer to
                 * vmbus_close() for details):
                 * 1. Close all sub-channels first
                 * 2. Then close the primary channel.
                 */
                mutex_lock(&vmbus_connection.channel_mutex);
                if (channel->state == CHANNEL_OPEN_STATE) {
                        /*
                         * The channel is currently not open;
                         * it is safe for us to cleanup the channel.
                         */
                        hv_process_channel_removal(channel);
                } else {
                        complete(&channel->rescind_event);
                }
                mutex_unlock(&vmbus_connection.channel_mutex);
        }

        /* The "channel" may have been freed. Do not access it any longer. */

        if (clean_up_chan_for_suspend)
                check_ready_for_suspend_event();
}

void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
{
        BUG_ON(!is_hvsock_channel(channel));

        /* We always get a rescind msg when a connection is closed. */
        while (!READ_ONCE(channel->probe_done) || !READ_ONCE(channel->rescind))
                msleep(1);

        vmbus_device_unregister(channel->device_obj);
}
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;

        trace_vmbus_onopen_result(result);

        /*
         * 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;

        trace_vmbus_ongpadl_created(gpadlcreated);

        /*
         * 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;

        trace_vmbus_ongpadl_torndown(gpadl_torndown);

        /*
         * 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;

        trace_vmbus_onversion_response(version_response);

        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 */
const struct vmbus_channel_message_table_entry
channel_message_table[CHANNELMSG_COUNT] = {
        { CHANNELMSG_INVALID,                   0, NULL, 0},
        { CHANNELMSG_OFFERCHANNEL,              0, vmbus_onoffer,
                sizeof(struct vmbus_channel_offer_channel)},
        { CHANNELMSG_RESCIND_CHANNELOFFER,      0, vmbus_onoffer_rescind,
                sizeof(struct vmbus_channel_rescind_offer) },
        { CHANNELMSG_REQUESTOFFERS,             0, NULL, 0},
        { CHANNELMSG_ALLOFFERS_DELIVERED,       1, vmbus_onoffers_delivered, 0},
        { CHANNELMSG_OPENCHANNEL,               0, NULL, 0},
        { CHANNELMSG_OPENCHANNEL_RESULT,        1, vmbus_onopen_result,
                sizeof(struct vmbus_channel_open_result)},
        { CHANNELMSG_CLOSECHANNEL,              0, NULL, 0},
        { CHANNELMSG_GPADL_HEADER,              0, NULL, 0},
        { CHANNELMSG_GPADL_BODY,                0, NULL, 0},
        { CHANNELMSG_GPADL_CREATED,             1, vmbus_ongpadl_created,
                sizeof(struct vmbus_channel_gpadl_created)},
        { CHANNELMSG_GPADL_TEARDOWN,            0, NULL, 0},
        { CHANNELMSG_GPADL_TORNDOWN,            1, vmbus_ongpadl_torndown,
                sizeof(struct vmbus_channel_gpadl_torndown) },
        { CHANNELMSG_RELID_RELEASED,            0, NULL, 0},
        { CHANNELMSG_INITIATE_CONTACT,          0, NULL, 0},
        { CHANNELMSG_VERSION_RESPONSE,          1, vmbus_onversion_response,
                sizeof(struct vmbus_channel_version_response)},
        { CHANNELMSG_UNLOAD,                    0, NULL, 0},
        { CHANNELMSG_UNLOAD_RESPONSE,           1, vmbus_unload_response, 0},
        { CHANNELMSG_18,                        0, NULL, 0},
        { CHANNELMSG_19,                        0, NULL, 0},
        { CHANNELMSG_20,                        0, NULL, 0},
        { CHANNELMSG_TL_CONNECT_REQUEST,        0, NULL, 0},
        { CHANNELMSG_MODIFYCHANNEL,             0, NULL, 0},
        { CHANNELMSG_TL_CONNECT_RESULT,         0, NULL, 0},
};

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

        /*
         * vmbus_on_msg_dpc() makes sure the hdr->msgtype here can not go
         * out of bound and the message_handler pointer can not be NULL.
         */
        channel_message_table[hdr->msgtype].message_handler(hdr);
}

/*
 * 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),
                             true);

        trace_vmbus_request_offers(ret);

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

                goto cleanup;
        }

cleanup:
        kfree(msginfo);

        return ret;
}

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);