/*
 *
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/hyperv.h>
#include <linux/export.h>
#include <asm/hyperv.h>
#include "hyperv_vmbus.h"


struct vmbus_connection vmbus_connection = {
        .conn_state             = DISCONNECTED,
        .next_gpadl_handle      = ATOMIC_INIT(0xE1E10),
};

/*
 * Negotiated protocol version with the host.
 */
__u32 vmbus_proto_version;
EXPORT_SYMBOL_GPL(vmbus_proto_version);

static __u32 vmbus_get_next_version(__u32 current_version)
{
        switch (current_version) {
        case (VERSION_WIN7):
                return VERSION_WS2008;

        case (VERSION_WIN8):
                return VERSION_WIN7;

        case (VERSION_WS2008):
        default:
                return VERSION_INVAL;
        }
}

static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
                                        __u32 version)
{
        int ret = 0;
        struct vmbus_channel_initiate_contact *msg;
        unsigned long flags;
        int t;

        init_completion(&msginfo->waitevent);

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

        msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
        msg->vmbus_version_requested = version;
        msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
        msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages);
        msg->monitor_page2 = virt_to_phys(
                        (void *)((unsigned long)vmbus_connection.monitor_pages +
                                 PAGE_SIZE));

        /*
         * Add to list before we send the request since we may
         * receive the response before returning from this routine
         */
        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
        list_add_tail(&msginfo->msglistentry,
                      &vmbus_connection.chn_msg_list);

        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

        ret = vmbus_post_msg(msg,
                               sizeof(struct vmbus_channel_initiate_contact));
        if (ret != 0) {
                spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
                list_del(&msginfo->msglistentry);
                spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
                                        flags);
                return ret;
        }

        /* Wait for the connection response */
        t =  wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
        if (t == 0) {
                spin_lock_irqsave(&vmbus_connection.channelmsg_lock,
                                flags);
                list_del(&msginfo->msglistentry);
                spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
                                        flags);
                return -ETIMEDOUT;
        }

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

        /* Check if successful */
        if (msginfo->response.version_response.version_supported) {
                vmbus_connection.conn_state = CONNECTED;
        } else {
                return -ECONNREFUSED;
        }

        return ret;
}

/*
 * vmbus_connect - Sends a connect request on the partition service connection
 */
int vmbus_connect(void)
{
        int ret = 0;
        struct vmbus_channel_msginfo *msginfo = NULL;
        __u32 version;

        /* Initialize the vmbus connection */
        vmbus_connection.conn_state = CONNECTING;
        vmbus_connection.work_queue = create_workqueue("hv_vmbus_con");
        if (!vmbus_connection.work_queue) {
                ret = -ENOMEM;
                goto cleanup;
        }

        INIT_LIST_HEAD(&vmbus_connection.chn_msg_list);
        spin_lock_init(&vmbus_connection.channelmsg_lock);

        INIT_LIST_HEAD(&vmbus_connection.chn_list);
        spin_lock_init(&vmbus_connection.channel_lock);

        /*
         * Setup the vmbus event connection for channel interrupt
         * abstraction stuff
         */
        vmbus_connection.int_page =
        (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO, 0);
        if (vmbus_connection.int_page == NULL) {
                ret = -ENOMEM;
                goto cleanup;
        }

        vmbus_connection.recv_int_page = vmbus_connection.int_page;
        vmbus_connection.send_int_page =
                (void *)((unsigned long)vmbus_connection.int_page +
                        (PAGE_SIZE >> 1));

        /*
         * Setup the monitor notification facility. The 1st page for
         * parent->child and the 2nd page for child->parent
         */
        vmbus_connection.monitor_pages =
        (void *)__get_free_pages((GFP_KERNEL|__GFP_ZERO), 1);
        if (vmbus_connection.monitor_pages == NULL) {
                ret = -ENOMEM;
                goto cleanup;
        }

        msginfo = kzalloc(sizeof(*msginfo) +
                          sizeof(struct vmbus_channel_initiate_contact),
                          GFP_KERNEL);
        if (msginfo == NULL) {
                ret = -ENOMEM;
                goto cleanup;
        }

        /*
         * Negotiate a compatible VMBUS version number with the
         * host. We start with the highest number we can support
         * and work our way down until we negotiate a compatible
         * version.
         */

        version = VERSION_CURRENT;

        do {
                ret = vmbus_negotiate_version(msginfo, version);
                if (ret == 0)
                        break;

                version = vmbus_get_next_version(version);
        } while (version != VERSION_INVAL);

        if (version == VERSION_INVAL)
                goto cleanup;

        vmbus_proto_version = version;
        pr_info("Hyper-V Host Build:%d-%d.%d-%d-%d.%d; Vmbus version:%d.%d\n",
                    host_info_eax, host_info_ebx >> 16,
                    host_info_ebx & 0xFFFF, host_info_ecx,
                    host_info_edx >> 24, host_info_edx & 0xFFFFFF,
                    version >> 16, version & 0xFFFF);

        kfree(msginfo);
        return 0;

cleanup:
        pr_err("Unable to connect to host\n");
        vmbus_connection.conn_state = DISCONNECTED;

        if (vmbus_connection.work_queue)
                destroy_workqueue(vmbus_connection.work_queue);

        if (vmbus_connection.int_page) {
                free_pages((unsigned long)vmbus_connection.int_page, 0);
                vmbus_connection.int_page = NULL;
        }

        if (vmbus_connection.monitor_pages) {
                free_pages((unsigned long)vmbus_connection.monitor_pages, 1);
                vmbus_connection.monitor_pages = NULL;
        }

        kfree(msginfo);

        return ret;
}


/*
 * relid2channel - Get the channel object given its
 * child relative id (ie channel id)
 */
struct vmbus_channel *relid2channel(u32 relid)
{
        struct vmbus_channel *channel;
        struct vmbus_channel *found_channel  = NULL;
        unsigned long flags;

        spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
                if (channel->offermsg.child_relid == relid) {
                        found_channel = channel;
                        break;
                }
        }
        spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);

        return found_channel;
}

/*
 * process_chn_event - Process a channel event notification
 */
static void process_chn_event(u32 relid)
{
        struct vmbus_channel *channel;
        unsigned long flags;
        void *arg;
        bool read_state;
        u32 bytes_to_read;

        /*
         * Find the channel based on this relid and invokes the
         * channel callback to process the event
         */
        channel = relid2channel(relid);

        if (!channel) {
                pr_err("channel not found for relid - %u\n", relid);
                return;
        }

        /*
         * A channel once created is persistent even when there
         * is no driver handling the device. An unloading driver
         * sets the onchannel_callback to NULL under the
         * protection of the channel inbound_lock. Thus, checking
         * and invoking the driver specific callback takes care of
         * orderly unloading of the driver.
         */

        spin_lock_irqsave(&channel->inbound_lock, flags);
        if (channel->onchannel_callback != NULL) {
                arg = channel->channel_callback_context;
                read_state = channel->batched_reading;
                /*
                 * This callback reads the messages sent by the host.
                 * We can optimize host to guest signaling by ensuring:
                 * 1. While reading the channel, we disable interrupts from
                 *    host.
                 * 2. Ensure that we process all posted messages from the host
                 *    before returning from this callback.
                 * 3. Once we return, enable signaling from the host. Once this
                 *    state is set we check to see if additional packets are
                 *    available to read. In this case we repeat the process.
                 */

                do {
                        hv_begin_read(&channel->inbound);
                        channel->onchannel_callback(arg);
                        bytes_to_read = hv_end_read(&channel->inbound);
                } while (read_state && (bytes_to_read != 0));
        } else {
                pr_err("no channel callback for relid - %u\n", relid);
        }

        spin_unlock_irqrestore(&channel->inbound_lock, flags);
}

/*
 * vmbus_on_event - Handler for events
 */
void vmbus_on_event(unsigned long data)
{
        u32 dword;
        u32 maxdword;
        int bit;
        u32 relid;
        u32 *recv_int_page = NULL;
        void *page_addr;
        int cpu = smp_processor_id();
        union hv_synic_event_flags *event;

        if ((vmbus_proto_version == VERSION_WS2008) ||
                (vmbus_proto_version == VERSION_WIN7)) {
                maxdword = MAX_NUM_CHANNELS_SUPPORTED >> 5;
                recv_int_page = vmbus_connection.recv_int_page;
        } else {
                /*
                 * When the host is win8 and beyond, the event page
                 * can be directly checked to get the id of the channel
                 * that has the interrupt pending.
                 */
                maxdword = HV_EVENT_FLAGS_DWORD_COUNT;
                page_addr = hv_context.synic_event_page[cpu];
                event = (union hv_synic_event_flags *)page_addr +
                                                 VMBUS_MESSAGE_SINT;
                recv_int_page = event->flags32;
        }



        /* Check events */
        if (!recv_int_page)
                return;
        for (dword = 0; dword < maxdword; dword++) {
                if (!recv_int_page[dword])
                        continue;
                for (bit = 0; bit < 32; bit++) {
                        if (sync_test_and_clear_bit(bit,
                                (unsigned long *)&recv_int_page[dword])) {
                                relid = (dword << 5) + bit;

                                if (relid == 0)
                                        /*
                                         * Special case - vmbus
                                         * channel protocol msg
                                         */
                                        continue;

                                process_chn_event(relid);
                        }
                }
        }
}

/*
 * vmbus_post_msg - Send a msg on the vmbus's message connection
 */
int vmbus_post_msg(void *buffer, size_t buflen)
{
        union hv_connection_id conn_id;
        int ret = 0;
        int retries = 0;

        conn_id.asu32 = 0;
        conn_id.u.id = VMBUS_MESSAGE_CONNECTION_ID;

        /*
         * hv_post_message() can have transient failures because of
         * insufficient resources. Retry the operation a couple of
         * times before giving up.
         */
        while (retries < 3) {
                ret =  hv_post_message(conn_id, 1, buffer, buflen);
                if (ret != HV_STATUS_INSUFFICIENT_BUFFERS)
                        return ret;
                retries++;
                msleep(100);
        }
        return ret;
}

/*
 * vmbus_set_event - Send an event notification to the parent
 */
int vmbus_set_event(struct vmbus_channel *channel)
{
        u32 child_relid = channel->offermsg.child_relid;

        if (!channel->is_dedicated_interrupt) {
                /* Each u32 represents 32 channels */
                sync_set_bit(child_relid & 31,
                        (unsigned long *)vmbus_connection.send_int_page +
                        (child_relid >> 5));
        }

        return hv_signal_event(channel->sig_event);
}