// 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/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/mshyperv.h>

#include "hyperv_vmbus.h"


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

        .ready_for_suspend_event= COMPLETION_INITIALIZER(
                                  vmbus_connection.ready_for_suspend_event),
        .ready_for_resume_event = COMPLETION_INITIALIZER(
                                  vmbus_connection.ready_for_resume_event),
};
EXPORT_SYMBOL_GPL(vmbus_connection);

/*
 * 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_WIN8_1):
                return VERSION_WIN8;

        case (VERSION_WIN10):
                return VERSION_WIN8_1;

        case (VERSION_WIN10_V5):
                return VERSION_WIN10;

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

int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
{
        int ret = 0;
        unsigned int cur_cpu;
        struct vmbus_channel_initiate_contact *msg;
        unsigned long flags;

        init_completion(&msginfo->waitevent);

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

        memset(msg, 0, sizeof(*msg));
        msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
        msg->vmbus_version_requested = version;

        /*
         * VMBus protocol 5.0 (VERSION_WIN10_V5) requires that we must use
         * VMBUS_MESSAGE_CONNECTION_ID_4 for the Initiate Contact Message,
         * and for subsequent messages, we must use the Message Connection ID
         * field in the host-returned Version Response Message. And, with
         * VERSION_WIN10_V5, we don't use msg->interrupt_page, but we tell
         * the host explicitly that we still use VMBUS_MESSAGE_SINT(2) for
         * compatibility.
         *
         * On old hosts, we should always use VMBUS_MESSAGE_CONNECTION_ID (1).
         */
        if (version >= VERSION_WIN10_V5) {
                msg->msg_sint = VMBUS_MESSAGE_SINT;
                vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID_4;
        } else {
                msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
                vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
        }

        msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
        msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
        /*
         * We want all channel messages to be delivered on CPU 0.
         * This has been the behavior pre-win8. This is not
         * perf issue and having all channel messages delivered on CPU 0
         * would be ok.
         * For post win8 hosts, we support receiving channel messagges on
         * all the CPUs. This is needed for kexec to work correctly where
         * the CPU attempting to connect may not be CPU 0.
         */
        if (version >= VERSION_WIN8_1) {
                cur_cpu = get_cpu();
                msg->target_vcpu = hv_cpu_number_to_vp_number(cur_cpu);
                vmbus_connection.connect_cpu = cur_cpu;
                put_cpu();
        } else {
                msg->target_vcpu = 0;
                vmbus_connection.connect_cpu = 0;
        }

        /*
         * 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),
                             true);

        trace_vmbus_negotiate_version(msg, ret);

        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 */
        wait_for_completion(&msginfo->waitevent);

        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;

                if (version >= VERSION_WIN10_V5)
                        vmbus_connection.msg_conn_id =
                                msginfo->response.version_response.msg_conn_id;
        } 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;
        }

        vmbus_connection.handle_primary_chan_wq =
                create_workqueue("hv_pri_chan");
        if (!vmbus_connection.handle_primary_chan_wq) {
                ret = -ENOMEM;
                goto cleanup;
        }

        vmbus_connection.handle_sub_chan_wq =
                create_workqueue("hv_sub_chan");
        if (!vmbus_connection.handle_sub_chan_wq) {
                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);
        mutex_init(&vmbus_connection.channel_mutex);

        /*
         * 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[0] = (void *)__get_free_pages((GFP_KERNEL|__GFP_ZERO), 0);
        vmbus_connection.monitor_pages[1] = (void *)__get_free_pages((GFP_KERNEL|__GFP_ZERO), 0);
        if ((vmbus_connection.monitor_pages[0] == NULL) ||
            (vmbus_connection.monitor_pages[1] == 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 == -ETIMEDOUT)
                        goto cleanup;

                if (vmbus_connection.conn_state == CONNECTED)
                        break;

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

        if (version == VERSION_INVAL)
                goto cleanup;

        vmbus_proto_version = version;
        pr_info("Vmbus version:%d.%d\n",
                version >> 16, version & 0xFFFF);

        kfree(msginfo);
        return 0;

cleanup:
        pr_err("Unable to connect to host\n");

        vmbus_connection.conn_state = DISCONNECTED;
        vmbus_disconnect();

        kfree(msginfo);

        return ret;
}

void vmbus_disconnect(void)
{
        /*
         * First send the unload request to the host.
         */
        vmbus_initiate_unload(false);

        if (vmbus_connection.handle_sub_chan_wq)
                destroy_workqueue(vmbus_connection.handle_sub_chan_wq);

        if (vmbus_connection.handle_primary_chan_wq)
                destroy_workqueue(vmbus_connection.handle_primary_chan_wq);

        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;
        }

        free_pages((unsigned long)vmbus_connection.monitor_pages[0], 0);
        free_pages((unsigned long)vmbus_connection.monitor_pages[1], 0);
        vmbus_connection.monitor_pages[0] = NULL;
        vmbus_connection.monitor_pages[1] = NULL;
}

/*
 * 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;
        struct list_head *cur, *tmp;
        struct vmbus_channel *cur_sc;

        BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));

        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
                if (channel->offermsg.child_relid == relid) {
                        found_channel = channel;
                        break;
                } else if (!list_empty(&channel->sc_list)) {
                        /*
                         * Deal with sub-channels.
                         */
                        list_for_each_safe(cur, tmp, &channel->sc_list) {
                                cur_sc = list_entry(cur, struct vmbus_channel,
                                                        sc_list);
                                if (cur_sc->offermsg.child_relid == relid) {
                                        found_channel = cur_sc;
                                        break;
                                }
                        }
                }
        }

        return found_channel;
}

/*
 * vmbus_on_event - Process a channel event notification
 *
 * For batched channels (default) 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.
 *    If this tasklet has been running for a long time
 *    then reschedule ourselves.
 */
void vmbus_on_event(unsigned long data)
{
        struct vmbus_channel *channel = (void *) data;
        unsigned long time_limit = jiffies + 2;

        trace_vmbus_on_event(channel);

        do {
                void (*callback_fn)(void *);

                /* A channel once created is persistent even when
                 * there is no driver handling the device. An
                 * unloading driver sets the onchannel_callback to NULL.
                 */
                callback_fn = READ_ONCE(channel->onchannel_callback);
                if (unlikely(callback_fn == NULL))
                        return;

                (*callback_fn)(channel->channel_callback_context);

                if (channel->callback_mode != HV_CALL_BATCHED)
                        return;

                if (likely(hv_end_read(&channel->inbound) == 0))
                        return;

                hv_begin_read(&channel->inbound);
        } while (likely(time_before(jiffies, time_limit)));

        /* The time limit (2 jiffies) has been reached */
        tasklet_schedule(&channel->callback_event);
}

/*
 * vmbus_post_msg - Send a msg on the vmbus's message connection
 */
int vmbus_post_msg(void *buffer, size_t buflen, bool can_sleep)
{
        struct vmbus_channel_message_header *hdr;
        union hv_connection_id conn_id;
        int ret = 0;
        int retries = 0;
        u32 usec = 1;

        conn_id.asu32 = 0;
        conn_id.u.id = vmbus_connection.msg_conn_id;

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

                switch (ret) {
                case HV_STATUS_INVALID_CONNECTION_ID:
                        /*
                         * See vmbus_negotiate_version(): VMBus protocol 5.0
                         * requires that we must use
                         * VMBUS_MESSAGE_CONNECTION_ID_4 for the Initiate
                         * Contact message, but on old hosts that only
                         * support VMBus protocol 4.0 or lower, here we get
                         * HV_STATUS_INVALID_CONNECTION_ID and we should
                         * return an error immediately without retrying.
                         */
                        hdr = buffer;
                        if (hdr->msgtype == CHANNELMSG_INITIATE_CONTACT)
                                return -EINVAL;
                        /*
                         * We could get this if we send messages too
                         * frequently.
                         */
                        ret = -EAGAIN;
                        break;
                case HV_STATUS_INSUFFICIENT_MEMORY:
                case HV_STATUS_INSUFFICIENT_BUFFERS:
                        ret = -ENOBUFS;
                        break;
                case HV_STATUS_SUCCESS:
                        return ret;
                default:
                        pr_err("hv_post_msg() failed; error code:%d\n", ret);
                        return -EINVAL;
                }

                retries++;
                if (can_sleep && usec > 1000)
                        msleep(usec / 1000);
                else if (usec < MAX_UDELAY_MS * 1000)
                        udelay(usec);
                else
                        mdelay(usec / 1000);

                if (retries < 22)
                        usec *= 2;
        }
        return ret;
}

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

        if (!channel->is_dedicated_interrupt)
                vmbus_send_interrupt(child_relid);

        ++channel->sig_events;

        hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
}
EXPORT_SYMBOL_GPL(vmbus_set_event);