/*-
 * Copyright (c) 2014,2016-2017 Microsoft Corp.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 *      Author: Sainath Varanasi.
 *      Date:   4/2012
 *      Email:  bsdic@microsoft.com
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/uio.h>
#include <sys/bus.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/reboot.h>
#include <sys/lock.h>
#include <sys/taskqueue.h>
#include <sys/selinfo.h>
#include <sys/sysctl.h>
#include <sys/poll.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/syscallsubr.h>
#include <sys/sysproto.h>
#include <sys/un.h>
#include <sys/endian.h>
#include <sys/_null.h>
#include <sys/sema.h>
#include <sys/signal.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/mutex.h>

#include <dev/hyperv/include/hyperv.h>
#include <dev/hyperv/include/vmbus.h>
#include <dev/hyperv/utilities/hv_utilreg.h>
#include <dev/hyperv/utilities/vmbus_icreg.h>
#include <dev/hyperv/utilities/vmbus_icvar.h>

#include "unicode.h"
#include "hv_kvp.h"
#include "vmbus_if.h"

/* hv_kvp defines */
#define BUFFERSIZE      sizeof(struct hv_kvp_msg)
#define kvp_hdr         hdr.kvp_hdr

#define KVP_FWVER_MAJOR         3
#define KVP_FWVER               VMBUS_IC_VERSION(KVP_FWVER_MAJOR, 0)

#define KVP_MSGVER_MAJOR        4
#define KVP_MSGVER              VMBUS_IC_VERSION(KVP_MSGVER_MAJOR, 0)

/* hv_kvp debug control */
static int hv_kvp_log = 0;

#define hv_kvp_log_error(...)   do {                            \
        if (hv_kvp_log > 0)                             \
                log(LOG_ERR, "hv_kvp: " __VA_ARGS__);   \
} while (0)

#define hv_kvp_log_info(...) do {                               \
        if (hv_kvp_log > 1)                             \
                log(LOG_INFO, "hv_kvp: " __VA_ARGS__);          \
} while (0)

static const struct vmbus_ic_desc vmbus_kvp_descs[] = {
        {
                .ic_guid = { .hv_guid = {
                    0xe7, 0xf4, 0xa0, 0xa9, 0x45, 0x5a, 0x96, 0x4d,
                    0xb8, 0x27, 0x8a, 0x84, 0x1e, 0x8c, 0x3,  0xe6 } },
                .ic_desc = "Hyper-V KVP"
        },
        VMBUS_IC_DESC_END
};

/* character device prototypes */
static d_open_t         hv_kvp_dev_open;
static d_close_t        hv_kvp_dev_close;
static d_read_t         hv_kvp_dev_daemon_read;
static d_write_t        hv_kvp_dev_daemon_write;
static d_poll_t         hv_kvp_dev_daemon_poll;

/* hv_kvp character device structure */
static struct cdevsw hv_kvp_cdevsw =
{
        .d_version      = D_VERSION,
        .d_open         = hv_kvp_dev_open,
        .d_close        = hv_kvp_dev_close,
        .d_read         = hv_kvp_dev_daemon_read,
        .d_write        = hv_kvp_dev_daemon_write,
        .d_poll         = hv_kvp_dev_daemon_poll,
        .d_name         = "hv_kvp_dev",
};


/*
 * Global state to track and synchronize multiple
 * KVP transaction requests from the host.
 */
typedef struct hv_kvp_sc {
        struct vmbus_ic_softc   util_sc;
        device_t                dev;

        /* Unless specified the pending mutex should be
         * used to alter the values of the following parameters:
         * 1. req_in_progress
         * 2. req_timed_out
         */
        struct mtx              pending_mutex;

        struct task             task;

        /* To track if transaction is active or not */
        boolean_t               req_in_progress;
        /* Tracks if daemon did not reply back in time */
        boolean_t               req_timed_out;
        /* Tracks if daemon is serving a request currently */
        boolean_t               daemon_busy;

        /* Length of host message */
        uint32_t                host_msg_len;

        /* Host message id */
        uint64_t                host_msg_id;

        /* Current kvp message from the host */
        struct hv_kvp_msg       *host_kvp_msg;

         /* Current kvp message for daemon */
        struct hv_kvp_msg       daemon_kvp_msg;

        /* Rcv buffer for communicating with the host*/
        uint8_t                 *rcv_buf;

        /* Device semaphore to control communication */
        struct sema             dev_sema;

        /* Indicates if daemon registered with driver */
        boolean_t               register_done;

        /* Character device status */
        boolean_t               dev_accessed;

        struct cdev *hv_kvp_dev;

        struct proc *daemon_task;

        struct selinfo hv_kvp_selinfo;
} hv_kvp_sc;

/* hv_kvp prototypes */
static int      hv_kvp_req_in_progress(hv_kvp_sc *sc);
static void     hv_kvp_transaction_init(hv_kvp_sc *sc, uint32_t, uint64_t, uint8_t *);
static void     hv_kvp_send_msg_to_daemon(hv_kvp_sc *sc);
static void     hv_kvp_process_request(void *context, int pending);

/*
 * hv_kvp low level functions
 */

/*
 * Check if kvp transaction is in progres
 */
static int
hv_kvp_req_in_progress(hv_kvp_sc *sc)
{

        return (sc->req_in_progress);
}


/*
 * This routine is called whenever a message is received from the host
 */
static void
hv_kvp_transaction_init(hv_kvp_sc *sc, uint32_t rcv_len,
                        uint64_t request_id, uint8_t *rcv_buf)
{

        /* Store all the relevant message details in the global structure */
        /* Do not need to use mutex for req_in_progress here */
        sc->req_in_progress = true;
        sc->host_msg_len = rcv_len;
        sc->host_msg_id = request_id;
        sc->rcv_buf = rcv_buf;
        sc->host_kvp_msg = (struct hv_kvp_msg *)&rcv_buf[
            sizeof(struct hv_vmbus_pipe_hdr) +
            sizeof(struct hv_vmbus_icmsg_hdr)];
}

/*
 * Convert ip related info in umsg from utf8 to utf16 and store in hmsg
 */
static int
hv_kvp_convert_utf8_ipinfo_to_utf16(struct hv_kvp_msg *umsg,
                                    struct hv_kvp_ip_msg *host_ip_msg)
{
        int err_ip, err_subnet, err_gway, err_dns, err_adap;
        int UNUSED_FLAG = 1;

        utf8_to_utf16((uint16_t *)host_ip_msg->kvp_ip_val.ip_addr,
            MAX_IP_ADDR_SIZE,
            (char *)umsg->body.kvp_ip_val.ip_addr,
            strlen((char *)umsg->body.kvp_ip_val.ip_addr),
            UNUSED_FLAG,
            &err_ip);
        utf8_to_utf16((uint16_t *)host_ip_msg->kvp_ip_val.sub_net,
            MAX_IP_ADDR_SIZE,
            (char *)umsg->body.kvp_ip_val.sub_net,
            strlen((char *)umsg->body.kvp_ip_val.sub_net),
            UNUSED_FLAG,
            &err_subnet);
        utf8_to_utf16((uint16_t *)host_ip_msg->kvp_ip_val.gate_way,
            MAX_GATEWAY_SIZE,
            (char *)umsg->body.kvp_ip_val.gate_way,
            strlen((char *)umsg->body.kvp_ip_val.gate_way),
            UNUSED_FLAG,
            &err_gway);
        utf8_to_utf16((uint16_t *)host_ip_msg->kvp_ip_val.dns_addr,
            MAX_IP_ADDR_SIZE,
            (char *)umsg->body.kvp_ip_val.dns_addr,
            strlen((char *)umsg->body.kvp_ip_val.dns_addr),
            UNUSED_FLAG,
            &err_dns);
        utf8_to_utf16((uint16_t *)host_ip_msg->kvp_ip_val.adapter_id,
            MAX_ADAPTER_ID_SIZE,
            (char *)umsg->body.kvp_ip_val.adapter_id,
            strlen((char *)umsg->body.kvp_ip_val.adapter_id),
            UNUSED_FLAG,
            &err_adap);

        host_ip_msg->kvp_ip_val.dhcp_enabled = umsg->body.kvp_ip_val.dhcp_enabled;
        host_ip_msg->kvp_ip_val.addr_family = umsg->body.kvp_ip_val.addr_family;

        return (err_ip | err_subnet | err_gway | err_dns | err_adap);
}


/*
 * Convert ip related info in hmsg from utf16 to utf8 and store in umsg
 */
static int
hv_kvp_convert_utf16_ipinfo_to_utf8(struct hv_kvp_ip_msg *host_ip_msg,
                                    struct hv_kvp_msg *umsg)
{
        int err_ip, err_subnet, err_gway, err_dns, err_adap;
        int UNUSED_FLAG = 1;
        device_t *devs;
        int devcnt;

        /* IP Address */
        utf16_to_utf8((char *)umsg->body.kvp_ip_val.ip_addr,
            MAX_IP_ADDR_SIZE,
            (uint16_t *)host_ip_msg->kvp_ip_val.ip_addr,
            MAX_IP_ADDR_SIZE,
            UNUSED_FLAG,
            &err_ip);

        /* Adapter ID : GUID */
        utf16_to_utf8((char *)umsg->body.kvp_ip_val.adapter_id,
            MAX_ADAPTER_ID_SIZE,
            (uint16_t *)host_ip_msg->kvp_ip_val.adapter_id,
            MAX_ADAPTER_ID_SIZE,
            UNUSED_FLAG,
            &err_adap);

        if (devclass_get_devices(devclass_find("hn"), &devs, &devcnt) == 0) {
                for (devcnt = devcnt - 1; devcnt >= 0; devcnt--) {
                        device_t dev = devs[devcnt];
                        struct vmbus_channel *chan;
                        char buf[HYPERV_GUID_STRLEN];
                        int n;

                        chan = vmbus_get_channel(dev);
                        n = hyperv_guid2str(vmbus_chan_guid_inst(chan), buf,
                            sizeof(buf));

                        /*
                         * The string in the 'kvp_ip_val.adapter_id' has
                         * braces around the GUID; skip the leading brace
                         * in 'kvp_ip_val.adapter_id'.
                         */
                        if (strncmp(buf,
                            ((char *)&umsg->body.kvp_ip_val.adapter_id) + 1,
                            n) == 0) {
                                strlcpy((char *)umsg->body.kvp_ip_val.adapter_id,
                                    device_get_nameunit(dev), MAX_ADAPTER_ID_SIZE);
                                break;
                        }
                }
                free(devs, M_TEMP);
        }

        /* Address Family , DHCP , SUBNET, Gateway, DNS */
        umsg->kvp_hdr.operation = host_ip_msg->operation;
        umsg->body.kvp_ip_val.addr_family = host_ip_msg->kvp_ip_val.addr_family;
        umsg->body.kvp_ip_val.dhcp_enabled = host_ip_msg->kvp_ip_val.dhcp_enabled;
        utf16_to_utf8((char *)umsg->body.kvp_ip_val.sub_net, MAX_IP_ADDR_SIZE,
            (uint16_t *)host_ip_msg->kvp_ip_val.sub_net,
            MAX_IP_ADDR_SIZE,
            UNUSED_FLAG,
            &err_subnet);

        utf16_to_utf8((char *)umsg->body.kvp_ip_val.gate_way, MAX_GATEWAY_SIZE,
            (uint16_t *)host_ip_msg->kvp_ip_val.gate_way,
            MAX_GATEWAY_SIZE,
            UNUSED_FLAG,
            &err_gway);

        utf16_to_utf8((char *)umsg->body.kvp_ip_val.dns_addr, MAX_IP_ADDR_SIZE,
            (uint16_t *)host_ip_msg->kvp_ip_val.dns_addr,
            MAX_IP_ADDR_SIZE,
            UNUSED_FLAG,
            &err_dns);

        return (err_ip | err_subnet | err_gway | err_dns | err_adap);
}


/*
 * Prepare a user kvp msg based on host kvp msg (utf16 to utf8)
 * Ensure utf16_utf8 takes care of the additional string terminating char!!
 */
static void
hv_kvp_convert_hostmsg_to_usermsg(struct hv_kvp_msg *hmsg, struct hv_kvp_msg *umsg)
{
        int utf_err = 0;
        uint32_t value_type;
        struct hv_kvp_ip_msg *host_ip_msg;

        host_ip_msg = (struct hv_kvp_ip_msg*)hmsg;
        memset(umsg, 0, sizeof(struct hv_kvp_msg));

        umsg->kvp_hdr.operation = hmsg->kvp_hdr.operation;
        umsg->kvp_hdr.pool = hmsg->kvp_hdr.pool;

        switch (umsg->kvp_hdr.operation) {
        case HV_KVP_OP_SET_IP_INFO:
                hv_kvp_convert_utf16_ipinfo_to_utf8(host_ip_msg, umsg);
                break;

        case HV_KVP_OP_GET_IP_INFO:
                utf16_to_utf8((char *)umsg->body.kvp_ip_val.adapter_id,
                    MAX_ADAPTER_ID_SIZE,
                    (uint16_t *)host_ip_msg->kvp_ip_val.adapter_id,
                    MAX_ADAPTER_ID_SIZE, 1, &utf_err);

                umsg->body.kvp_ip_val.addr_family =
                    host_ip_msg->kvp_ip_val.addr_family;
                break;

        case HV_KVP_OP_SET:
                value_type = hmsg->body.kvp_set.data.value_type;

                switch (value_type) {
                case HV_REG_SZ:
                        umsg->body.kvp_set.data.value_size =
                            utf16_to_utf8(
                                (char *)umsg->body.kvp_set.data.msg_value.value,
                                HV_KVP_EXCHANGE_MAX_VALUE_SIZE - 1,
                                (uint16_t *)hmsg->body.kvp_set.data.msg_value.value,
                                hmsg->body.kvp_set.data.value_size,
                                1, &utf_err);
                        /* utf8 encoding */
                        umsg->body.kvp_set.data.value_size =
                            umsg->body.kvp_set.data.value_size / 2;
                        break;

                case HV_REG_U32:
                        umsg->body.kvp_set.data.value_size =
                            sprintf(umsg->body.kvp_set.data.msg_value.value, "%d",
                                hmsg->body.kvp_set.data.msg_value.value_u32) + 1;
                        break;

                case HV_REG_U64:
                        umsg->body.kvp_set.data.value_size =
                            sprintf(umsg->body.kvp_set.data.msg_value.value, "%llu",
                                (unsigned long long)
                                hmsg->body.kvp_set.data.msg_value.value_u64) + 1;
                        break;
                }

                umsg->body.kvp_set.data.key_size =
                    utf16_to_utf8(
                        umsg->body.kvp_set.data.key,
                        HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1,
                        (uint16_t *)hmsg->body.kvp_set.data.key,
                        hmsg->body.kvp_set.data.key_size,
                        1, &utf_err);

                /* utf8 encoding */
                umsg->body.kvp_set.data.key_size =
                    umsg->body.kvp_set.data.key_size / 2;
                break;

        case HV_KVP_OP_GET:
                umsg->body.kvp_get.data.key_size =
                    utf16_to_utf8(umsg->body.kvp_get.data.key,
                        HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1,
                        (uint16_t *)hmsg->body.kvp_get.data.key,
                        hmsg->body.kvp_get.data.key_size,
                        1, &utf_err);
                /* utf8 encoding */
                umsg->body.kvp_get.data.key_size =
                    umsg->body.kvp_get.data.key_size / 2;
                break;

        case HV_KVP_OP_DELETE:
                umsg->body.kvp_delete.key_size =
                    utf16_to_utf8(umsg->body.kvp_delete.key,
                        HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1,
                        (uint16_t *)hmsg->body.kvp_delete.key,
                        hmsg->body.kvp_delete.key_size,
                        1, &utf_err);
                /* utf8 encoding */
                umsg->body.kvp_delete.key_size =
                    umsg->body.kvp_delete.key_size / 2;
                break;

        case HV_KVP_OP_ENUMERATE:
                umsg->body.kvp_enum_data.index =
                    hmsg->body.kvp_enum_data.index;
                break;

        default:
                hv_kvp_log_info("%s: daemon_kvp_msg: Invalid operation : %d\n",
                    __func__, umsg->kvp_hdr.operation);
        }
}


/*
 * Prepare a host kvp msg based on user kvp msg (utf8 to utf16)
 */
static int
hv_kvp_convert_usermsg_to_hostmsg(struct hv_kvp_msg *umsg, struct hv_kvp_msg *hmsg)
{
        int hkey_len = 0, hvalue_len = 0, utf_err = 0;
        struct hv_kvp_exchg_msg_value *host_exchg_data;
        char *key_name, *value;

        struct hv_kvp_ip_msg *host_ip_msg = (struct hv_kvp_ip_msg *)hmsg;

        switch (hmsg->kvp_hdr.operation) {
        case HV_KVP_OP_GET_IP_INFO:
                return (hv_kvp_convert_utf8_ipinfo_to_utf16(umsg, host_ip_msg));

        case HV_KVP_OP_SET_IP_INFO:
        case HV_KVP_OP_SET:
        case HV_KVP_OP_DELETE:
                return (0);

        case HV_KVP_OP_ENUMERATE:
                host_exchg_data = &hmsg->body.kvp_enum_data.data;
                key_name = umsg->body.kvp_enum_data.data.key;
                hkey_len = utf8_to_utf16((uint16_t *)host_exchg_data->key,
                                ((HV_KVP_EXCHANGE_MAX_KEY_SIZE / 2) - 2),
                                key_name, strlen(key_name),
                                1, &utf_err);
                /* utf16 encoding */
                host_exchg_data->key_size = 2 * (hkey_len + 1);
                value = umsg->body.kvp_enum_data.data.msg_value.value;
                hvalue_len = utf8_to_utf16(
                                (uint16_t *)host_exchg_data->msg_value.value,
                                ((HV_KVP_EXCHANGE_MAX_VALUE_SIZE / 2) - 2),
                                value, strlen(value),
                                1, &utf_err);
                host_exchg_data->value_size = 2 * (hvalue_len + 1);
                host_exchg_data->value_type = HV_REG_SZ;

                if ((hkey_len < 0) || (hvalue_len < 0))
                        return (EINVAL);

                return (0);

        case HV_KVP_OP_GET:
                host_exchg_data = &hmsg->body.kvp_get.data;
                value = umsg->body.kvp_get.data.msg_value.value;
                hvalue_len = utf8_to_utf16(
                                (uint16_t *)host_exchg_data->msg_value.value,
                                ((HV_KVP_EXCHANGE_MAX_VALUE_SIZE / 2) - 2),
                                value, strlen(value),
                                1, &utf_err);
                /* Convert value size to uft16 */
                host_exchg_data->value_size = 2 * (hvalue_len + 1);
                /* Use values by string */
                host_exchg_data->value_type = HV_REG_SZ;

                if (hvalue_len < 0)
                        return (EINVAL);

                return (0);

        default:
                return (EINVAL);
        }
}


/*
 * Send the response back to the host.
 */
static void
hv_kvp_respond_host(hv_kvp_sc *sc, uint32_t error)
{
        struct hv_vmbus_icmsg_hdr *hv_icmsg_hdrp;

        hv_icmsg_hdrp = (struct hv_vmbus_icmsg_hdr *)
            &sc->rcv_buf[sizeof(struct hv_vmbus_pipe_hdr)];

        hv_icmsg_hdrp->status = error;
        hv_icmsg_hdrp->icflags = HV_ICMSGHDRFLAG_TRANSACTION |
            HV_ICMSGHDRFLAG_RESPONSE;

        error = vmbus_chan_send(vmbus_get_channel(sc->dev),
            VMBUS_CHANPKT_TYPE_INBAND, 0, sc->rcv_buf, sc->host_msg_len,
            sc->host_msg_id);
        if (error)
                hv_kvp_log_info("%s: hv_kvp_respond_host: sendpacket error:%d\n",
                        __func__, error);
}


/*
 * This is the main kvp kernel process that interacts with both user daemon
 * and the host
 */
static void
hv_kvp_send_msg_to_daemon(hv_kvp_sc *sc)
{
        struct hv_kvp_msg *hmsg = sc->host_kvp_msg;
        struct hv_kvp_msg *umsg = &sc->daemon_kvp_msg;

        /* Prepare kvp_msg to be sent to user */
        hv_kvp_convert_hostmsg_to_usermsg(hmsg, umsg);

        /* Send the msg to user via function deamon_read - setting sema */
        sema_post(&sc->dev_sema);

        /* We should wake up the daemon, in case it's doing poll() */
        selwakeup(&sc->hv_kvp_selinfo);
}


/*
 * Function to read the kvp request buffer from host
 * and interact with daemon
 */
static void
hv_kvp_process_request(void *context, int pending)
{
        uint8_t *kvp_buf;
        struct vmbus_channel *channel;
        uint32_t recvlen = 0;
        uint64_t requestid;
        struct hv_vmbus_icmsg_hdr *icmsghdrp;
        int ret = 0, error;
        hv_kvp_sc *sc;

        hv_kvp_log_info("%s: entering hv_kvp_process_request\n", __func__);

        sc = (hv_kvp_sc*)context;
        kvp_buf = sc->util_sc.ic_buf;
        channel = vmbus_get_channel(sc->dev);

        recvlen = sc->util_sc.ic_buflen;
        ret = vmbus_chan_recv(channel, kvp_buf, &recvlen, &requestid);
        KASSERT(ret != ENOBUFS, ("hvkvp recvbuf is not large enough"));
        /* XXX check recvlen to make sure that it contains enough data */

        while ((ret == 0) && (recvlen > 0)) {
                icmsghdrp = (struct hv_vmbus_icmsg_hdr *)
                    &kvp_buf[sizeof(struct hv_vmbus_pipe_hdr)];

                hv_kvp_transaction_init(sc, recvlen, requestid, kvp_buf);
                if (icmsghdrp->icmsgtype == HV_ICMSGTYPE_NEGOTIATE) {
                        error = vmbus_ic_negomsg(&sc->util_sc,
                            kvp_buf, &recvlen, KVP_FWVER, KVP_MSGVER);
                        /* XXX handle vmbus_ic_negomsg failure. */
                        if (!error)
                                hv_kvp_respond_host(sc, HV_S_OK);
                        else
                                hv_kvp_respond_host(sc, HV_E_FAIL);
                        /*
                         * It is ok to not acquire the mutex before setting
                         * req_in_progress here because negotiation is the
                         * first thing that happens and hence there is no
                         * chance of a race condition.
                         */

                        sc->req_in_progress = false;
                        hv_kvp_log_info("%s :version negotiated\n", __func__);

                } else {
                        if (!sc->daemon_busy) {

                                hv_kvp_log_info("%s: issuing query to daemon\n", __func__);
                                mtx_lock(&sc->pending_mutex);
                                sc->req_timed_out = false;
                                sc->daemon_busy = true;
                                mtx_unlock(&sc->pending_mutex);

                                hv_kvp_send_msg_to_daemon(sc);
                                hv_kvp_log_info("%s: waiting for daemon\n", __func__);
                        }

                        /* Wait 5 seconds for daemon to respond back */
                        tsleep(sc, 0, "kvpworkitem", 5 * hz);
                        hv_kvp_log_info("%s: came out of wait\n", __func__);
                }

                mtx_lock(&sc->pending_mutex);

                /* Notice that once req_timed_out is set to true
                 * it will remain true until the next request is
                 * sent to the daemon. The response from daemon
                 * is forwarded to host only when this flag is
                 * false.
                 */
                sc->req_timed_out = true;

                /*
                 * Cancel request if so need be.
                 */
                if (hv_kvp_req_in_progress(sc)) {
                        hv_kvp_log_info("%s: request was still active after wait so failing\n", __func__);
                        hv_kvp_respond_host(sc, HV_E_FAIL);
                        sc->req_in_progress = false;
                }

                mtx_unlock(&sc->pending_mutex);

                /*
                 * Try reading next buffer
                 */
                recvlen = sc->util_sc.ic_buflen;
                ret = vmbus_chan_recv(channel, kvp_buf, &recvlen, &requestid);
                KASSERT(ret != ENOBUFS, ("hvkvp recvbuf is not large enough"));
                /* XXX check recvlen to make sure that it contains enough data */

                hv_kvp_log_info("%s: read: context %p, ret =%d, recvlen=%d\n",
                        __func__, context, ret, recvlen);
        }
}


/*
 * Callback routine that gets called whenever there is a message from host
 */
static void
hv_kvp_callback(struct vmbus_channel *chan __unused, void *context)
{
        hv_kvp_sc *sc = (hv_kvp_sc*)context;
        /*
         The first request from host will not be handled until daemon is registered.
         when callback is triggered without a registered daemon, callback just return.
         When a new daemon gets regsitered, this callbcak is trigged from _write op.
        */
        if (sc->register_done) {
                hv_kvp_log_info("%s: Queuing work item\n", __func__);
                taskqueue_enqueue(taskqueue_thread, &sc->task);
        }
}

static int
hv_kvp_dev_open(struct cdev *dev, int oflags, int devtype,
                                struct thread *td)
{
        hv_kvp_sc *sc = (hv_kvp_sc*)dev->si_drv1;

        hv_kvp_log_info("%s: Opened device \"hv_kvp_device\" successfully.\n", __func__);
        if (sc->dev_accessed)
                return (-EBUSY);

        sc->daemon_task = curproc;
        sc->dev_accessed = true;
        sc->daemon_busy = false;
        return (0);
}


static int
hv_kvp_dev_close(struct cdev *dev __unused, int fflag __unused, int devtype __unused,
                                 struct thread *td __unused)
{
        hv_kvp_sc *sc = (hv_kvp_sc*)dev->si_drv1;

        hv_kvp_log_info("%s: Closing device \"hv_kvp_device\".\n", __func__);
        sc->dev_accessed = false;
        sc->register_done = false;
        return (0);
}


/*
 * hv_kvp_daemon read invokes this function
 * acts as a send to daemon
 */
static int
hv_kvp_dev_daemon_read(struct cdev *dev, struct uio *uio, int ioflag __unused)
{
        size_t amt;
        int error = 0;
        struct hv_kvp_msg *hv_kvp_dev_buf;
        hv_kvp_sc *sc = (hv_kvp_sc*)dev->si_drv1;

        /* Read is not allowed util registering is done. */
        if (!sc->register_done)
                return (EPERM);

        sema_wait(&sc->dev_sema);

        hv_kvp_dev_buf = malloc(sizeof(*hv_kvp_dev_buf), M_TEMP, M_WAITOK);
        memcpy(hv_kvp_dev_buf, &sc->daemon_kvp_msg, sizeof(struct hv_kvp_msg));

        amt = MIN(uio->uio_resid, uio->uio_offset >= BUFFERSIZE + 1 ? 0 :
                BUFFERSIZE + 1 - uio->uio_offset);

        if ((error = uiomove(hv_kvp_dev_buf, amt, uio)) != 0)
                hv_kvp_log_info("%s: hv_kvp uiomove read failed!\n", __func__);

        free(hv_kvp_dev_buf, M_TEMP);
        return (error);
}


/*
 * hv_kvp_daemon write invokes this function
 * acts as a receive from daemon
 */
static int
hv_kvp_dev_daemon_write(struct cdev *dev, struct uio *uio, int ioflag __unused)
{
        size_t amt;
        int error = 0;
        struct hv_kvp_msg *hv_kvp_dev_buf;
        hv_kvp_sc *sc = (hv_kvp_sc*)dev->si_drv1;

        uio->uio_offset = 0;
        hv_kvp_dev_buf = malloc(sizeof(*hv_kvp_dev_buf), M_TEMP, M_WAITOK);

        amt = MIN(uio->uio_resid, BUFFERSIZE);
        error = uiomove(hv_kvp_dev_buf, amt, uio);

        if (error != 0) {
                free(hv_kvp_dev_buf, M_TEMP);
                return (error);
        }
        memcpy(&sc->daemon_kvp_msg, hv_kvp_dev_buf, sizeof(struct hv_kvp_msg));

        free(hv_kvp_dev_buf, M_TEMP);
        if (sc->register_done == false) {
                if (sc->daemon_kvp_msg.kvp_hdr.operation == HV_KVP_OP_REGISTER) {
                        sc->register_done = true;
                        hv_kvp_callback(vmbus_get_channel(sc->dev), dev->si_drv1);
                }
                else {
                        hv_kvp_log_info("%s, KVP Registration Failed\n", __func__);
                        return (EINVAL);
                }
        } else {

                mtx_lock(&sc->pending_mutex);

                if(!sc->req_timed_out) {
                        struct hv_kvp_msg *hmsg = sc->host_kvp_msg;
                        struct hv_kvp_msg *umsg = &sc->daemon_kvp_msg;

                        error = hv_kvp_convert_usermsg_to_hostmsg(umsg, hmsg);
                        hv_kvp_respond_host(sc, umsg->hdr.error);
                        wakeup(sc);
                        sc->req_in_progress = false;
                        if (umsg->hdr.error != HV_S_OK)
                                hv_kvp_log_info("%s, Error 0x%x from daemon\n",
                                    __func__, umsg->hdr.error);
                        if (error)
                                hv_kvp_log_info("%s, Error from convert\n", __func__);
                }

                sc->daemon_busy = false;
                mtx_unlock(&sc->pending_mutex);
        }

        return (error);
}


/*
 * hv_kvp_daemon poll invokes this function to check if data is available
 * for daemon to read.
 */
static int
hv_kvp_dev_daemon_poll(struct cdev *dev, int events, struct thread *td)
{
        int revents = 0;
        hv_kvp_sc *sc = (hv_kvp_sc*)dev->si_drv1;

        mtx_lock(&sc->pending_mutex);
        /*
         * We check global flag daemon_busy for the data availiability for
         * userland to read. Deamon_busy is set to true before driver has data
         * for daemon to read. It is set to false after daemon sends
         * then response back to driver.
         */
        if (sc->daemon_busy == true)
                revents = POLLIN;
        else
                selrecord(td, &sc->hv_kvp_selinfo);

        mtx_unlock(&sc->pending_mutex);

        return (revents);
}

static int
hv_kvp_probe(device_t dev)
{

        return (vmbus_ic_probe(dev, vmbus_kvp_descs));
}

static int
hv_kvp_attach(device_t dev)
{
        int error;
        struct sysctl_oid_list *child;
        struct sysctl_ctx_list *ctx;

        hv_kvp_sc *sc = (hv_kvp_sc*)device_get_softc(dev);

        sc->dev = dev;
        sema_init(&sc->dev_sema, 0, "hv_kvp device semaphore");
        mtx_init(&sc->pending_mutex, "hv-kvp pending mutex",
                NULL, MTX_DEF);

        ctx = device_get_sysctl_ctx(dev);
        child = SYSCTL_CHILDREN(device_get_sysctl_tree(dev));

        SYSCTL_ADD_INT(ctx, child, OID_AUTO, "hv_kvp_log",
            CTLFLAG_RWTUN, &hv_kvp_log, 0, "Hyperv KVP service log level");

        TASK_INIT(&sc->task, 0, hv_kvp_process_request, sc);

        /* create character device */
        error = make_dev_p(MAKEDEV_CHECKNAME | MAKEDEV_WAITOK,
                        &sc->hv_kvp_dev,
                        &hv_kvp_cdevsw,
                        0,
                        UID_ROOT,
                        GID_WHEEL,
                        0640,
                        "hv_kvp_dev");

        if (error != 0)
                return (error);
        sc->hv_kvp_dev->si_drv1 = sc;

        return (vmbus_ic_attach(dev, hv_kvp_callback));
}

static int
hv_kvp_detach(device_t dev)
{
        hv_kvp_sc *sc = (hv_kvp_sc*)device_get_softc(dev);

        if (sc->daemon_task != NULL) {
                PROC_LOCK(sc->daemon_task);
                kern_psignal(sc->daemon_task, SIGKILL);
                PROC_UNLOCK(sc->daemon_task);
        }

        destroy_dev(sc->hv_kvp_dev);
        return (vmbus_ic_detach(dev));
}

static device_method_t kvp_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe, hv_kvp_probe),
        DEVMETHOD(device_attach, hv_kvp_attach),
        DEVMETHOD(device_detach, hv_kvp_detach),
        DEVMETHOD_END
};

static driver_t kvp_driver = { "hvkvp", kvp_methods, sizeof(hv_kvp_sc)};

DRIVER_MODULE(hv_kvp, vmbus, kvp_driver, NULL, NULL);
MODULE_VERSION(hv_kvp, 1);
MODULE_DEPEND(hv_kvp, vmbus, 1, 1, 1);