/*
 * Copyright (c) 2010, 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/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/reboot.h>
#include <linux/hyperv.h>

static void shutdown_onchannelcallback(void *context);
static struct hv_util_service util_shutdown = {
        .util_cb = shutdown_onchannelcallback,
};

static void timesync_onchannelcallback(void *context);
static struct hv_util_service util_timesynch = {
        .util_cb = timesync_onchannelcallback,
};

static void heartbeat_onchannelcallback(void *context);
static struct hv_util_service util_heartbeat = {
        .util_cb = heartbeat_onchannelcallback,
};

static struct hv_util_service util_kvp = {
        .util_cb = hv_kvp_onchannelcallback,
        .util_init = hv_kvp_init,
        .util_deinit = hv_kvp_deinit,
};

static void perform_shutdown(struct work_struct *dummy)
{
        orderly_poweroff(true);
}

/*
 * Perform the shutdown operation in a thread context.
 */
static DECLARE_WORK(shutdown_work, perform_shutdown);

static void shutdown_onchannelcallback(void *context)
{
        struct vmbus_channel *channel = context;
        u32 recvlen;
        u64 requestid;
        u8  execute_shutdown = false;
        u8  *shut_txf_buf = util_shutdown.recv_buffer;

        struct shutdown_msg_data *shutdown_msg;

        struct icmsg_hdr *icmsghdrp;
        struct icmsg_negotiate *negop = NULL;

        vmbus_recvpacket(channel, shut_txf_buf,
                         PAGE_SIZE, &recvlen, &requestid);

        if (recvlen > 0) {
                icmsghdrp = (struct icmsg_hdr *)&shut_txf_buf[
                        sizeof(struct vmbuspipe_hdr)];

                if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
                        vmbus_prep_negotiate_resp(icmsghdrp, negop,
                                        shut_txf_buf, MAX_SRV_VER, MAX_SRV_VER);
                } else {
                        shutdown_msg =
                                (struct shutdown_msg_data *)&shut_txf_buf[
                                        sizeof(struct vmbuspipe_hdr) +
                                        sizeof(struct icmsg_hdr)];

                        switch (shutdown_msg->flags) {
                        case 0:
                        case 1:
                                icmsghdrp->status = HV_S_OK;
                                execute_shutdown = true;

                                pr_info("Shutdown request received -"
                                            " graceful shutdown initiated\n");
                                break;
                        default:
                                icmsghdrp->status = HV_E_FAIL;
                                execute_shutdown = false;

                                pr_info("Shutdown request received -"
                                            " Invalid request\n");
                                break;
                        }
                }

                icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
                        | ICMSGHDRFLAG_RESPONSE;

                vmbus_sendpacket(channel, shut_txf_buf,
                                       recvlen, requestid,
                                       VM_PKT_DATA_INBAND, 0);
        }

        if (execute_shutdown == true)
                schedule_work(&shutdown_work);
}

/*
 * Set guest time to host UTC time.
 */
static inline void do_adj_guesttime(u64 hosttime)
{
        s64 host_tns;
        struct timespec host_ts;

        host_tns = (hosttime - WLTIMEDELTA) * 100;
        host_ts = ns_to_timespec(host_tns);

        do_settimeofday(&host_ts);
}

/*
 * Set the host time in a process context.
 */

struct adj_time_work {
        struct work_struct work;
        u64     host_time;
};

static void hv_set_host_time(struct work_struct *work)
{
        struct adj_time_work    *wrk;

        wrk = container_of(work, struct adj_time_work, work);
        do_adj_guesttime(wrk->host_time);
        kfree(wrk);
}

/*
 * Synchronize time with host after reboot, restore, etc.
 *
 * ICTIMESYNCFLAG_SYNC flag bit indicates reboot, restore events of the VM.
 * After reboot the flag ICTIMESYNCFLAG_SYNC is included in the first time
 * message after the timesync channel is opened. Since the hv_utils module is
 * loaded after hv_vmbus, the first message is usually missed. The other
 * thing is, systime is automatically set to emulated hardware clock which may
 * not be UTC time or in the same time zone. So, to override these effects, we
 * use the first 50 time samples for initial system time setting.
 */
static inline void adj_guesttime(u64 hosttime, u8 flags)
{
        struct adj_time_work    *wrk;
        static s32 scnt = 50;

        wrk = kmalloc(sizeof(struct adj_time_work), GFP_ATOMIC);
        if (wrk == NULL)
                return;

        wrk->host_time = hosttime;
        if ((flags & ICTIMESYNCFLAG_SYNC) != 0) {
                INIT_WORK(&wrk->work, hv_set_host_time);
                schedule_work(&wrk->work);
                return;
        }

        if ((flags & ICTIMESYNCFLAG_SAMPLE) != 0 && scnt > 0) {
                scnt--;
                INIT_WORK(&wrk->work, hv_set_host_time);
                schedule_work(&wrk->work);
        } else
                kfree(wrk);
}

/*
 * Time Sync Channel message handler.
 */
static void timesync_onchannelcallback(void *context)
{
        struct vmbus_channel *channel = context;
        u32 recvlen;
        u64 requestid;
        struct icmsg_hdr *icmsghdrp;
        struct ictimesync_data *timedatap;
        u8 *time_txf_buf = util_timesynch.recv_buffer;

        vmbus_recvpacket(channel, time_txf_buf,
                         PAGE_SIZE, &recvlen, &requestid);

        if (recvlen > 0) {
                icmsghdrp = (struct icmsg_hdr *)&time_txf_buf[
                                sizeof(struct vmbuspipe_hdr)];

                if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
                        vmbus_prep_negotiate_resp(icmsghdrp, NULL, time_txf_buf,
                                                MAX_SRV_VER, MAX_SRV_VER);
                } else {
                        timedatap = (struct ictimesync_data *)&time_txf_buf[
                                sizeof(struct vmbuspipe_hdr) +
                                sizeof(struct icmsg_hdr)];
                        adj_guesttime(timedatap->parenttime, timedatap->flags);
                }

                icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
                        | ICMSGHDRFLAG_RESPONSE;

                vmbus_sendpacket(channel, time_txf_buf,
                                recvlen, requestid,
                                VM_PKT_DATA_INBAND, 0);
        }
}

/*
 * Heartbeat functionality.
 * Every two seconds, Hyper-V send us a heartbeat request message.
 * we respond to this message, and Hyper-V knows we are alive.
 */
static void heartbeat_onchannelcallback(void *context)
{
        struct vmbus_channel *channel = context;
        u32 recvlen;
        u64 requestid;
        struct icmsg_hdr *icmsghdrp;
        struct heartbeat_msg_data *heartbeat_msg;
        u8 *hbeat_txf_buf = util_heartbeat.recv_buffer;

        vmbus_recvpacket(channel, hbeat_txf_buf,
                         PAGE_SIZE, &recvlen, &requestid);

        if (recvlen > 0) {
                icmsghdrp = (struct icmsg_hdr *)&hbeat_txf_buf[
                                sizeof(struct vmbuspipe_hdr)];

                if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
                        vmbus_prep_negotiate_resp(icmsghdrp, NULL,
                                hbeat_txf_buf, MAX_SRV_VER, MAX_SRV_VER);
                } else {
                        heartbeat_msg =
                                (struct heartbeat_msg_data *)&hbeat_txf_buf[
                                        sizeof(struct vmbuspipe_hdr) +
                                        sizeof(struct icmsg_hdr)];

                        heartbeat_msg->seq_num += 1;
                }

                icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
                        | ICMSGHDRFLAG_RESPONSE;

                vmbus_sendpacket(channel, hbeat_txf_buf,
                                       recvlen, requestid,
                                       VM_PKT_DATA_INBAND, 0);
        }
}

static int util_probe(struct hv_device *dev,
                        const struct hv_vmbus_device_id *dev_id)
{
        struct hv_util_service *srv =
                (struct hv_util_service *)dev_id->driver_data;
        int ret;

        srv->recv_buffer = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
        if (!srv->recv_buffer)
                return -ENOMEM;
        if (srv->util_init) {
                ret = srv->util_init(srv);
                if (ret) {
                        ret = -ENODEV;
                        goto error1;
                }
        }

        /*
         * The set of services managed by the util driver are not performance
         * critical and do not need batched reading. Furthermore, some services
         * such as KVP can only handle one message from the host at a time.
         * Turn off batched reading for all util drivers before we open the
         * channel.
         */

        set_channel_read_state(dev->channel, false);

        ret = vmbus_open(dev->channel, 4 * PAGE_SIZE, 4 * PAGE_SIZE, NULL, 0,
                        srv->util_cb, dev->channel);
        if (ret)
                goto error;

        hv_set_drvdata(dev, srv);
        return 0;

error:
        if (srv->util_deinit)
                srv->util_deinit();
error1:
        kfree(srv->recv_buffer);
        return ret;
}

static int util_remove(struct hv_device *dev)
{
        struct hv_util_service *srv = hv_get_drvdata(dev);

        vmbus_close(dev->channel);
        if (srv->util_deinit)
                srv->util_deinit();
        kfree(srv->recv_buffer);

        return 0;
}

static const struct hv_vmbus_device_id id_table[] = {
        /* Shutdown guid */
        { HV_SHUTDOWN_GUID,
          .driver_data = (unsigned long)&util_shutdown
        },
        /* Time synch guid */
        { HV_TS_GUID,
          .driver_data = (unsigned long)&util_timesynch
        },
        /* Heartbeat guid */
        { HV_HEART_BEAT_GUID,
          .driver_data = (unsigned long)&util_heartbeat
        },
        /* KVP guid */
        { HV_KVP_GUID,
          .driver_data = (unsigned long)&util_kvp
        },
        { },
};

MODULE_DEVICE_TABLE(vmbus, id_table);

/* The one and only one */
static  struct hv_driver util_drv = {
        .name = "hv_util",
        .id_table = id_table,
        .probe =  util_probe,
        .remove =  util_remove,
};

static int __init init_hyperv_utils(void)
{
        pr_info("Registering HyperV Utility Driver\n");

        return vmbus_driver_register(&util_drv);
}

static void exit_hyperv_utils(void)
{
        pr_info("De-Registered HyperV Utility Driver\n");

        vmbus_driver_unregister(&util_drv);
}

module_init(init_hyperv_utils);
module_exit(exit_hyperv_utils);

MODULE_DESCRIPTION("Hyper-V Utilities");
MODULE_VERSION(HV_DRV_VERSION);
MODULE_LICENSE("GPL");