/*
 * 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>
 *   K. Y. Srinivasan <kys@microsoft.com>
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/completion.h>
#include <linux/hyperv.h>
#include <linux/kernel_stat.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/sched/task_stack.h>

#include <asm/mshyperv.h>
#include <linux/notifier.h>
#include <linux/ptrace.h>
#include <linux/screen_info.h>
#include <linux/kdebug.h>
#include <linux/efi.h>
#include <linux/random.h>
#include "hyperv_vmbus.h"

struct vmbus_dynid {
        struct list_head node;
        struct hv_vmbus_device_id id;
};

static struct acpi_device  *hv_acpi_dev;

static struct completion probe_event;

static int hyperv_cpuhp_online;

static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,
                              void *args)
{
        struct pt_regs *regs;

        regs = current_pt_regs();

        hyperv_report_panic(regs, val);
        return NOTIFY_DONE;
}

static int hyperv_die_event(struct notifier_block *nb, unsigned long val,
                            void *args)
{
        struct die_args *die = (struct die_args *)args;
        struct pt_regs *regs = die->regs;

        hyperv_report_panic(regs, val);
        return NOTIFY_DONE;
}

static struct notifier_block hyperv_die_block = {
        .notifier_call = hyperv_die_event,
};
static struct notifier_block hyperv_panic_block = {
        .notifier_call = hyperv_panic_event,
};

static const char *fb_mmio_name = "fb_range";
static struct resource *fb_mmio;
static struct resource *hyperv_mmio;
static DEFINE_SEMAPHORE(hyperv_mmio_lock);

static int vmbus_exists(void)
{
        if (hv_acpi_dev == NULL)
                return -ENODEV;

        return 0;
}

#define VMBUS_ALIAS_LEN ((sizeof((struct hv_vmbus_device_id *)0)->guid) * 2)
static void print_alias_name(struct hv_device *hv_dev, char *alias_name)
{
        int i;
        for (i = 0; i < VMBUS_ALIAS_LEN; i += 2)
                sprintf(&alias_name[i], "%02x", hv_dev->dev_type.b[i/2]);
}

static u8 channel_monitor_group(const struct vmbus_channel *channel)
{
        return (u8)channel->offermsg.monitorid / 32;
}

static u8 channel_monitor_offset(const struct vmbus_channel *channel)
{
        return (u8)channel->offermsg.monitorid % 32;
}

static u32 channel_pending(const struct vmbus_channel *channel,
                           const struct hv_monitor_page *monitor_page)
{
        u8 monitor_group = channel_monitor_group(channel);

        return monitor_page->trigger_group[monitor_group].pending;
}

static u32 channel_latency(const struct vmbus_channel *channel,
                           const struct hv_monitor_page *monitor_page)
{
        u8 monitor_group = channel_monitor_group(channel);
        u8 monitor_offset = channel_monitor_offset(channel);

        return monitor_page->latency[monitor_group][monitor_offset];
}

static u32 channel_conn_id(struct vmbus_channel *channel,
                           struct hv_monitor_page *monitor_page)
{
        u8 monitor_group = channel_monitor_group(channel);
        u8 monitor_offset = channel_monitor_offset(channel);
        return monitor_page->parameter[monitor_group][monitor_offset].connectionid.u.id;
}

static ssize_t id_show(struct device *dev, struct device_attribute *dev_attr,
                       char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n", hv_dev->channel->offermsg.child_relid);
}
static DEVICE_ATTR_RO(id);

static ssize_t state_show(struct device *dev, struct device_attribute *dev_attr,
                          char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n", hv_dev->channel->state);
}
static DEVICE_ATTR_RO(state);

static ssize_t monitor_id_show(struct device *dev,
                               struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n", hv_dev->channel->offermsg.monitorid);
}
static DEVICE_ATTR_RO(monitor_id);

static ssize_t class_id_show(struct device *dev,
                               struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "{%pUl}\n",
                       hv_dev->channel->offermsg.offer.if_type.b);
}
static DEVICE_ATTR_RO(class_id);

static ssize_t device_id_show(struct device *dev,
                              struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "{%pUl}\n",
                       hv_dev->channel->offermsg.offer.if_instance.b);
}
static DEVICE_ATTR_RO(device_id);

static ssize_t modalias_show(struct device *dev,
                             struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        char alias_name[VMBUS_ALIAS_LEN + 1];

        print_alias_name(hv_dev, alias_name);
        return sprintf(buf, "vmbus:%s\n", alias_name);
}
static DEVICE_ATTR_RO(modalias);

static ssize_t server_monitor_pending_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_pending(hv_dev->channel,
                                       vmbus_connection.monitor_pages[1]));
}
static DEVICE_ATTR_RO(server_monitor_pending);

static ssize_t client_monitor_pending_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_pending(hv_dev->channel,
                                       vmbus_connection.monitor_pages[1]));
}
static DEVICE_ATTR_RO(client_monitor_pending);

static ssize_t server_monitor_latency_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_latency(hv_dev->channel,
                                       vmbus_connection.monitor_pages[0]));
}
static DEVICE_ATTR_RO(server_monitor_latency);

static ssize_t client_monitor_latency_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_latency(hv_dev->channel,
                                       vmbus_connection.monitor_pages[1]));
}
static DEVICE_ATTR_RO(client_monitor_latency);

static ssize_t server_monitor_conn_id_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_conn_id(hv_dev->channel,
                                       vmbus_connection.monitor_pages[0]));
}
static DEVICE_ATTR_RO(server_monitor_conn_id);

static ssize_t client_monitor_conn_id_show(struct device *dev,
                                           struct device_attribute *dev_attr,
                                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);

        if (!hv_dev->channel)
                return -ENODEV;
        return sprintf(buf, "%d\n",
                       channel_conn_id(hv_dev->channel,
                                       vmbus_connection.monitor_pages[1]));
}
static DEVICE_ATTR_RO(client_monitor_conn_id);

static ssize_t out_intr_mask_show(struct device *dev,
                                  struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info outbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
        return sprintf(buf, "%d\n", outbound.current_interrupt_mask);
}
static DEVICE_ATTR_RO(out_intr_mask);

static ssize_t out_read_index_show(struct device *dev,
                                   struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info outbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
        return sprintf(buf, "%d\n", outbound.current_read_index);
}
static DEVICE_ATTR_RO(out_read_index);

static ssize_t out_write_index_show(struct device *dev,
                                    struct device_attribute *dev_attr,
                                    char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info outbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
        return sprintf(buf, "%d\n", outbound.current_write_index);
}
static DEVICE_ATTR_RO(out_write_index);

static ssize_t out_read_bytes_avail_show(struct device *dev,
                                         struct device_attribute *dev_attr,
                                         char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info outbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
        return sprintf(buf, "%d\n", outbound.bytes_avail_toread);
}
static DEVICE_ATTR_RO(out_read_bytes_avail);

static ssize_t out_write_bytes_avail_show(struct device *dev,
                                          struct device_attribute *dev_attr,
                                          char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info outbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
        return sprintf(buf, "%d\n", outbound.bytes_avail_towrite);
}
static DEVICE_ATTR_RO(out_write_bytes_avail);

static ssize_t in_intr_mask_show(struct device *dev,
                                 struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info inbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
        return sprintf(buf, "%d\n", inbound.current_interrupt_mask);
}
static DEVICE_ATTR_RO(in_intr_mask);

static ssize_t in_read_index_show(struct device *dev,
                                  struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info inbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
        return sprintf(buf, "%d\n", inbound.current_read_index);
}
static DEVICE_ATTR_RO(in_read_index);

static ssize_t in_write_index_show(struct device *dev,
                                   struct device_attribute *dev_attr, char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info inbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
        return sprintf(buf, "%d\n", inbound.current_write_index);
}
static DEVICE_ATTR_RO(in_write_index);

static ssize_t in_read_bytes_avail_show(struct device *dev,
                                        struct device_attribute *dev_attr,
                                        char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info inbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
        return sprintf(buf, "%d\n", inbound.bytes_avail_toread);
}
static DEVICE_ATTR_RO(in_read_bytes_avail);

static ssize_t in_write_bytes_avail_show(struct device *dev,
                                         struct device_attribute *dev_attr,
                                         char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct hv_ring_buffer_debug_info inbound;

        if (!hv_dev->channel)
                return -ENODEV;
        hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
        return sprintf(buf, "%d\n", inbound.bytes_avail_towrite);
}
static DEVICE_ATTR_RO(in_write_bytes_avail);

static ssize_t channel_vp_mapping_show(struct device *dev,
                                       struct device_attribute *dev_attr,
                                       char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        struct vmbus_channel *channel = hv_dev->channel, *cur_sc;
        unsigned long flags;
        int buf_size = PAGE_SIZE, n_written, tot_written;
        struct list_head *cur;

        if (!channel)
                return -ENODEV;

        tot_written = snprintf(buf, buf_size, "%u:%u\n",
                channel->offermsg.child_relid, channel->target_cpu);

        spin_lock_irqsave(&channel->lock, flags);

        list_for_each(cur, &channel->sc_list) {
                if (tot_written >= buf_size - 1)
                        break;

                cur_sc = list_entry(cur, struct vmbus_channel, sc_list);
                n_written = scnprintf(buf + tot_written,
                                     buf_size - tot_written,
                                     "%u:%u\n",
                                     cur_sc->offermsg.child_relid,
                                     cur_sc->target_cpu);
                tot_written += n_written;
        }

        spin_unlock_irqrestore(&channel->lock, flags);

        return tot_written;
}
static DEVICE_ATTR_RO(channel_vp_mapping);

static ssize_t vendor_show(struct device *dev,
                           struct device_attribute *dev_attr,
                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        return sprintf(buf, "0x%x\n", hv_dev->vendor_id);
}
static DEVICE_ATTR_RO(vendor);

static ssize_t device_show(struct device *dev,
                           struct device_attribute *dev_attr,
                           char *buf)
{
        struct hv_device *hv_dev = device_to_hv_device(dev);
        return sprintf(buf, "0x%x\n", hv_dev->device_id);
}
static DEVICE_ATTR_RO(device);

/* Set up per device attributes in /sys/bus/vmbus/devices/<bus device> */
static struct attribute *vmbus_dev_attrs[] = {
        &dev_attr_id.attr,
        &dev_attr_state.attr,
        &dev_attr_monitor_id.attr,
        &dev_attr_class_id.attr,
        &dev_attr_device_id.attr,
        &dev_attr_modalias.attr,
        &dev_attr_server_monitor_pending.attr,
        &dev_attr_client_monitor_pending.attr,
        &dev_attr_server_monitor_latency.attr,
        &dev_attr_client_monitor_latency.attr,
        &dev_attr_server_monitor_conn_id.attr,
        &dev_attr_client_monitor_conn_id.attr,
        &dev_attr_out_intr_mask.attr,
        &dev_attr_out_read_index.attr,
        &dev_attr_out_write_index.attr,
        &dev_attr_out_read_bytes_avail.attr,
        &dev_attr_out_write_bytes_avail.attr,
        &dev_attr_in_intr_mask.attr,
        &dev_attr_in_read_index.attr,
        &dev_attr_in_write_index.attr,
        &dev_attr_in_read_bytes_avail.attr,
        &dev_attr_in_write_bytes_avail.attr,
        &dev_attr_channel_vp_mapping.attr,
        &dev_attr_vendor.attr,
        &dev_attr_device.attr,
        NULL,
};
ATTRIBUTE_GROUPS(vmbus_dev);

/*
 * vmbus_uevent - add uevent for our device
 *
 * This routine is invoked when a device is added or removed on the vmbus to
 * generate a uevent to udev in the userspace. The udev will then look at its
 * rule and the uevent generated here to load the appropriate driver
 *
 * The alias string will be of the form vmbus:guid where guid is the string
 * representation of the device guid (each byte of the guid will be
 * represented with two hex characters.
 */
static int vmbus_uevent(struct device *device, struct kobj_uevent_env *env)
{
        struct hv_device *dev = device_to_hv_device(device);
        int ret;
        char alias_name[VMBUS_ALIAS_LEN + 1];

        print_alias_name(dev, alias_name);
        ret = add_uevent_var(env, "MODALIAS=vmbus:%s", alias_name);
        return ret;
}

static const uuid_le null_guid;

static inline bool is_null_guid(const uuid_le *guid)
{
        if (uuid_le_cmp(*guid, null_guid))
                return false;
        return true;
}

/*
 * Return a matching hv_vmbus_device_id pointer.
 * If there is no match, return NULL.
 */
static const struct hv_vmbus_device_id *hv_vmbus_get_id(struct hv_driver *drv,
                                        const uuid_le *guid)
{
        const struct hv_vmbus_device_id *id = NULL;
        struct vmbus_dynid *dynid;

        /* Look at the dynamic ids first, before the static ones */
        spin_lock(&drv->dynids.lock);
        list_for_each_entry(dynid, &drv->dynids.list, node) {
                if (!uuid_le_cmp(dynid->id.guid, *guid)) {
                        id = &dynid->id;
                        break;
                }
        }
        spin_unlock(&drv->dynids.lock);

        if (id)
                return id;

        id = drv->id_table;
        if (id == NULL)
                return NULL; /* empty device table */

        for (; !is_null_guid(&id->guid); id++)
                if (!uuid_le_cmp(id->guid, *guid))
                        return id;

        return NULL;
}

/* vmbus_add_dynid - add a new device ID to this driver and re-probe devices */
static int vmbus_add_dynid(struct hv_driver *drv, uuid_le *guid)
{
        struct vmbus_dynid *dynid;

        dynid = kzalloc(sizeof(*dynid), GFP_KERNEL);
        if (!dynid)
                return -ENOMEM;

        dynid->id.guid = *guid;

        spin_lock(&drv->dynids.lock);
        list_add_tail(&dynid->node, &drv->dynids.list);
        spin_unlock(&drv->dynids.lock);

        return driver_attach(&drv->driver);
}

static void vmbus_free_dynids(struct hv_driver *drv)
{
        struct vmbus_dynid *dynid, *n;

        spin_lock(&drv->dynids.lock);
        list_for_each_entry_safe(dynid, n, &drv->dynids.list, node) {
                list_del(&dynid->node);
                kfree(dynid);
        }
        spin_unlock(&drv->dynids.lock);
}

/*
 * store_new_id - sysfs frontend to vmbus_add_dynid()
 *
 * Allow GUIDs to be added to an existing driver via sysfs.
 */
static ssize_t new_id_store(struct device_driver *driver, const char *buf,
                            size_t count)
{
        struct hv_driver *drv = drv_to_hv_drv(driver);
        uuid_le guid;
        ssize_t retval;

        retval = uuid_le_to_bin(buf, &guid);
        if (retval)
                return retval;

        if (hv_vmbus_get_id(drv, &guid))
                return -EEXIST;

        retval = vmbus_add_dynid(drv, &guid);
        if (retval)
                return retval;
        return count;
}
static DRIVER_ATTR_WO(new_id);

/*
 * store_remove_id - remove a PCI device ID from this driver
 *
 * Removes a dynamic pci device ID to this driver.
 */
static ssize_t remove_id_store(struct device_driver *driver, const char *buf,
                               size_t count)
{
        struct hv_driver *drv = drv_to_hv_drv(driver);
        struct vmbus_dynid *dynid, *n;
        uuid_le guid;
        ssize_t retval;

        retval = uuid_le_to_bin(buf, &guid);
        if (retval)
                return retval;

        retval = -ENODEV;
        spin_lock(&drv->dynids.lock);
        list_for_each_entry_safe(dynid, n, &drv->dynids.list, node) {
                struct hv_vmbus_device_id *id = &dynid->id;

                if (!uuid_le_cmp(id->guid, guid)) {
                        list_del(&dynid->node);
                        kfree(dynid);
                        retval = count;
                        break;
                }
        }
        spin_unlock(&drv->dynids.lock);

        return retval;
}
static DRIVER_ATTR_WO(remove_id);

static struct attribute *vmbus_drv_attrs[] = {
        &driver_attr_new_id.attr,
        &driver_attr_remove_id.attr,
        NULL,
};
ATTRIBUTE_GROUPS(vmbus_drv);


/*
 * vmbus_match - Attempt to match the specified device to the specified driver
 */
static int vmbus_match(struct device *device, struct device_driver *driver)
{
        struct hv_driver *drv = drv_to_hv_drv(driver);
        struct hv_device *hv_dev = device_to_hv_device(device);

        /* The hv_sock driver handles all hv_sock offers. */
        if (is_hvsock_channel(hv_dev->channel))
                return drv->hvsock;

        if (hv_vmbus_get_id(drv, &hv_dev->dev_type))
                return 1;

        return 0;
}

/*
 * vmbus_probe - Add the new vmbus's child device
 */
static int vmbus_probe(struct device *child_device)
{
        int ret = 0;
        struct hv_driver *drv =
                        drv_to_hv_drv(child_device->driver);
        struct hv_device *dev = device_to_hv_device(child_device);
        const struct hv_vmbus_device_id *dev_id;

        dev_id = hv_vmbus_get_id(drv, &dev->dev_type);
        if (drv->probe) {
                ret = drv->probe(dev, dev_id);
                if (ret != 0)
                        pr_err("probe failed for device %s (%d)\n",
                               dev_name(child_device), ret);

        } else {
                pr_err("probe not set for driver %s\n",
                       dev_name(child_device));
                ret = -ENODEV;
        }
        return ret;
}

/*
 * vmbus_remove - Remove a vmbus device
 */
static int vmbus_remove(struct device *child_device)
{
        struct hv_driver *drv;
        struct hv_device *dev = device_to_hv_device(child_device);

        if (child_device->driver) {
                drv = drv_to_hv_drv(child_device->driver);
                if (drv->remove)
                        drv->remove(dev);
        }

        return 0;
}


/*
 * vmbus_shutdown - Shutdown a vmbus device
 */
static void vmbus_shutdown(struct device *child_device)
{
        struct hv_driver *drv;
        struct hv_device *dev = device_to_hv_device(child_device);


        /* The device may not be attached yet */
        if (!child_device->driver)
                return;

        drv = drv_to_hv_drv(child_device->driver);

        if (drv->shutdown)
                drv->shutdown(dev);
}


/*
 * vmbus_device_release - Final callback release of the vmbus child device
 */
static void vmbus_device_release(struct device *device)
{
        struct hv_device *hv_dev = device_to_hv_device(device);
        struct vmbus_channel *channel = hv_dev->channel;

        mutex_lock(&vmbus_connection.channel_mutex);
        hv_process_channel_removal(channel->offermsg.child_relid);
        mutex_unlock(&vmbus_connection.channel_mutex);
        kfree(hv_dev);

}

/* The one and only one */
static struct bus_type  hv_bus = {
        .name =         "vmbus",
        .match =                vmbus_match,
        .shutdown =             vmbus_shutdown,
        .remove =               vmbus_remove,
        .probe =                vmbus_probe,
        .uevent =               vmbus_uevent,
        .dev_groups =           vmbus_dev_groups,
        .drv_groups =           vmbus_drv_groups,
};

struct onmessage_work_context {
        struct work_struct work;
        struct hv_message msg;
};

static void vmbus_onmessage_work(struct work_struct *work)
{
        struct onmessage_work_context *ctx;

        /* Do not process messages if we're in DISCONNECTED state */
        if (vmbus_connection.conn_state == DISCONNECTED)
                return;

        ctx = container_of(work, struct onmessage_work_context,
                           work);
        vmbus_onmessage(&ctx->msg);
        kfree(ctx);
}

static void hv_process_timer_expiration(struct hv_message *msg,
                                        struct hv_per_cpu_context *hv_cpu)
{
        struct clock_event_device *dev = hv_cpu->clk_evt;

        if (dev->event_handler)
                dev->event_handler(dev);

        vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
}

void vmbus_on_msg_dpc(unsigned long data)
{
        struct hv_per_cpu_context *hv_cpu = (void *)data;
        void *page_addr = hv_cpu->synic_message_page;
        struct hv_message *msg = (struct hv_message *)page_addr +
                                  VMBUS_MESSAGE_SINT;
        struct vmbus_channel_message_header *hdr;
        const struct vmbus_channel_message_table_entry *entry;
        struct onmessage_work_context *ctx;
        u32 message_type = msg->header.message_type;

        if (message_type == HVMSG_NONE)
                /* no msg */
                return;

        hdr = (struct vmbus_channel_message_header *)msg->u.payload;

        trace_vmbus_on_msg_dpc(hdr);

        if (hdr->msgtype >= CHANNELMSG_COUNT) {
                WARN_ONCE(1, "unknown msgtype=%d\n", hdr->msgtype);
                goto msg_handled;
        }

        entry = &channel_message_table[hdr->msgtype];
        if (entry->handler_type == VMHT_BLOCKING) {
                ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
                if (ctx == NULL)
                        return;

                INIT_WORK(&ctx->work, vmbus_onmessage_work);
                memcpy(&ctx->msg, msg, sizeof(*msg));

                /*
                 * The host can generate a rescind message while we
                 * may still be handling the original offer. We deal with
                 * this condition by ensuring the processing is done on the
                 * same CPU.
                 */
                switch (hdr->msgtype) {
                case CHANNELMSG_RESCIND_CHANNELOFFER:
                        /*
                         * If we are handling the rescind message;
                         * schedule the work on the global work queue.
                         */
                        schedule_work_on(vmbus_connection.connect_cpu,
                                         &ctx->work);
                        break;

                case CHANNELMSG_OFFERCHANNEL:
                        atomic_inc(&vmbus_connection.offer_in_progress);
                        queue_work_on(vmbus_connection.connect_cpu,
                                      vmbus_connection.work_queue,
                                      &ctx->work);
                        break;

                default:
                        queue_work(vmbus_connection.work_queue, &ctx->work);
                }
        } else
                entry->message_handler(hdr);

msg_handled:
        vmbus_signal_eom(msg, message_type);
}


/*
 * Direct callback for channels using other deferred processing
 */
static void vmbus_channel_isr(struct vmbus_channel *channel)
{
        void (*callback_fn)(void *);

        callback_fn = READ_ONCE(channel->onchannel_callback);
        if (likely(callback_fn != NULL))
                (*callback_fn)(channel->channel_callback_context);
}

/*
 * Schedule all channels with events pending
 */
static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
{
        unsigned long *recv_int_page;
        u32 maxbits, relid;

        if (vmbus_proto_version < VERSION_WIN8) {
                maxbits = MAX_NUM_CHANNELS_SUPPORTED;
                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.
                 */
                void *page_addr = hv_cpu->synic_event_page;
                union hv_synic_event_flags *event
                        = (union hv_synic_event_flags *)page_addr +
                                                 VMBUS_MESSAGE_SINT;

                maxbits = HV_EVENT_FLAGS_COUNT;
                recv_int_page = event->flags;
        }

        if (unlikely(!recv_int_page))
                return;

        for_each_set_bit(relid, recv_int_page, maxbits) {
                struct vmbus_channel *channel;

                if (!sync_test_and_clear_bit(relid, recv_int_page))
                        continue;

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

                rcu_read_lock();

                /* Find channel based on relid */
                list_for_each_entry_rcu(channel, &hv_cpu->chan_list, percpu_list) {
                        if (channel->offermsg.child_relid != relid)
                                continue;

                        if (channel->rescind)
                                continue;

                        trace_vmbus_chan_sched(channel);

                        ++channel->interrupts;

                        switch (channel->callback_mode) {
                        case HV_CALL_ISR:
                                vmbus_channel_isr(channel);
                                break;

                        case HV_CALL_BATCHED:
                                hv_begin_read(&channel->inbound);
                                /* fallthrough */
                        case HV_CALL_DIRECT:
                                tasklet_schedule(&channel->callback_event);
                        }
                }

                rcu_read_unlock();
        }
}

static void vmbus_isr(void)
{
        struct hv_per_cpu_context *hv_cpu
                = this_cpu_ptr(hv_context.cpu_context);
        void *page_addr = hv_cpu->synic_event_page;
        struct hv_message *msg;
        union hv_synic_event_flags *event;
        bool handled = false;

        if (unlikely(page_addr == NULL))
                return;

        event = (union hv_synic_event_flags *)page_addr +
                                         VMBUS_MESSAGE_SINT;
        /*
         * Check for events before checking for messages. This is the order
         * in which events and messages are checked in Windows guests on
         * Hyper-V, and the Windows team suggested we do the same.
         */

        if ((vmbus_proto_version == VERSION_WS2008) ||
                (vmbus_proto_version == VERSION_WIN7)) {

                /* Since we are a child, we only need to check bit 0 */
                if (sync_test_and_clear_bit(0, event->flags))
                        handled = true;
        } else {
                /*
                 * Our host is win8 or above. The signaling mechanism
                 * has changed and we can directly look at the event page.
                 * If bit n is set then we have an interrup on the channel
                 * whose id is n.
                 */

                handled = true;
        }

        if (handled)
                vmbus_chan_sched(hv_cpu);

        page_addr = hv_cpu->synic_message_page;
        msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;

        /* Check if there are actual msgs to be processed */
        if (msg->header.message_type != HVMSG_NONE) {
                if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
                        hv_process_timer_expiration(msg, hv_cpu);
                else
                        tasklet_schedule(&hv_cpu->msg_dpc);
        }

        add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR, 0);
}


/*
 * vmbus_bus_init -Main vmbus driver initialization routine.
 *
 * Here, we
 *      - initialize the vmbus driver context
 *      - invoke the vmbus hv main init routine
 *      - retrieve the channel offers
 */
static int vmbus_bus_init(void)
{
        int ret;

        /* Hypervisor initialization...setup hypercall page..etc */
        ret = hv_init();
        if (ret != 0) {
                pr_err("Unable to initialize the hypervisor - 0x%x\n", ret);
                return ret;
        }

        ret = bus_register(&hv_bus);
        if (ret)
                return ret;

        hv_setup_vmbus_irq(vmbus_isr);

        ret = hv_synic_alloc();
        if (ret)
                goto err_alloc;
        /*
         * Initialize the per-cpu interrupt state and
         * connect to the host.
         */
        ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
                                hv_synic_init, hv_synic_cleanup);
        if (ret < 0)
                goto err_alloc;
        hyperv_cpuhp_online = ret;

        ret = vmbus_connect();
        if (ret)
                goto err_connect;

        /*
         * Only register if the crash MSRs are available
         */
        if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
                register_die_notifier(&hyperv_die_block);
                atomic_notifier_chain_register(&panic_notifier_list,
                                               &hyperv_panic_block);
        }

        vmbus_request_offers();

        return 0;

err_connect:
        cpuhp_remove_state(hyperv_cpuhp_online);
err_alloc:
        hv_synic_free();
        hv_remove_vmbus_irq();

        bus_unregister(&hv_bus);

        return ret;
}

/**
 * __vmbus_child_driver_register() - Register a vmbus's driver
 * @hv_driver: Pointer to driver structure you want to register
 * @owner: owner module of the drv
 * @mod_name: module name string
 *
 * Registers the given driver with Linux through the 'driver_register()' call
 * and sets up the hyper-v vmbus handling for this driver.
 * It will return the state of the 'driver_register()' call.
 *
 */
int __vmbus_driver_register(struct hv_driver *hv_driver, struct module *owner, const char *mod_name)
{
        int ret;

        pr_info("registering driver %s\n", hv_driver->name);

        ret = vmbus_exists();
        if (ret < 0)
                return ret;

        hv_driver->driver.name = hv_driver->name;
        hv_driver->driver.owner = owner;
        hv_driver->driver.mod_name = mod_name;
        hv_driver->driver.bus = &hv_bus;

        spin_lock_init(&hv_driver->dynids.lock);
        INIT_LIST_HEAD(&hv_driver->dynids.list);

        ret = driver_register(&hv_driver->driver);

        return ret;
}
EXPORT_SYMBOL_GPL(__vmbus_driver_register);

/**
 * vmbus_driver_unregister() - Unregister a vmbus's driver
 * @hv_driver: Pointer to driver structure you want to
 *             un-register
 *
 * Un-register the given driver that was previous registered with a call to
 * vmbus_driver_register()
 */
void vmbus_driver_unregister(struct hv_driver *hv_driver)
{
        pr_info("unregistering driver %s\n", hv_driver->name);

        if (!vmbus_exists()) {
                driver_unregister(&hv_driver->driver);
                vmbus_free_dynids(hv_driver);
        }
}
EXPORT_SYMBOL_GPL(vmbus_driver_unregister);


/*
 * Called when last reference to channel is gone.
 */
static void vmbus_chan_release(struct kobject *kobj)
{
        struct vmbus_channel *channel
                = container_of(kobj, struct vmbus_channel, kobj);

        kfree_rcu(channel, rcu);
}

struct vmbus_chan_attribute {
        struct attribute attr;
        ssize_t (*show)(const struct vmbus_channel *chan, char *buf);
        ssize_t (*store)(struct vmbus_channel *chan,
                         const char *buf, size_t count);
};
#define VMBUS_CHAN_ATTR(_name, _mode, _show, _store) \
        struct vmbus_chan_attribute chan_attr_##_name \
                = __ATTR(_name, _mode, _show, _store)
#define VMBUS_CHAN_ATTR_RW(_name) \
        struct vmbus_chan_attribute chan_attr_##_name = __ATTR_RW(_name)
#define VMBUS_CHAN_ATTR_RO(_name) \
        struct vmbus_chan_attribute chan_attr_##_name = __ATTR_RO(_name)
#define VMBUS_CHAN_ATTR_WO(_name) \
        struct vmbus_chan_attribute chan_attr_##_name = __ATTR_WO(_name)

static ssize_t vmbus_chan_attr_show(struct kobject *kobj,
                                    struct attribute *attr, char *buf)
{
        const struct vmbus_chan_attribute *attribute
                = container_of(attr, struct vmbus_chan_attribute, attr);
        const struct vmbus_channel *chan
                = container_of(kobj, struct vmbus_channel, kobj);

        if (!attribute->show)
                return -EIO;

        return attribute->show(chan, buf);
}

static const struct sysfs_ops vmbus_chan_sysfs_ops = {
        .show = vmbus_chan_attr_show,
};

static ssize_t out_mask_show(const struct vmbus_channel *channel, char *buf)
{
        const struct hv_ring_buffer_info *rbi = &channel->outbound;

        return sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask);
}
static VMBUS_CHAN_ATTR_RO(out_mask);

static ssize_t in_mask_show(const struct vmbus_channel *channel, char *buf)
{
        const struct hv_ring_buffer_info *rbi = &channel->inbound;

        return sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask);
}
static VMBUS_CHAN_ATTR_RO(in_mask);

static ssize_t read_avail_show(const struct vmbus_channel *channel, char *buf)
{
        const struct hv_ring_buffer_info *rbi = &channel->inbound;

        return sprintf(buf, "%u\n", hv_get_bytes_to_read(rbi));
}
static VMBUS_CHAN_ATTR_RO(read_avail);

static ssize_t write_avail_show(const struct vmbus_channel *channel, char *buf)
{
        const struct hv_ring_buffer_info *rbi = &channel->outbound;

        return sprintf(buf, "%u\n", hv_get_bytes_to_write(rbi));
}
static VMBUS_CHAN_ATTR_RO(write_avail);

static ssize_t show_target_cpu(const struct vmbus_channel *channel, char *buf)
{
        return sprintf(buf, "%u\n", channel->target_cpu);
}
static VMBUS_CHAN_ATTR(cpu, S_IRUGO, show_target_cpu, NULL);

static ssize_t channel_pending_show(const struct vmbus_channel *channel,
                                    char *buf)
{
        return sprintf(buf, "%d\n",
                       channel_pending(channel,
                                       vmbus_connection.monitor_pages[1]));
}
static VMBUS_CHAN_ATTR(pending, S_IRUGO, channel_pending_show, NULL);

static ssize_t channel_latency_show(const struct vmbus_channel *channel,
                                    char *buf)
{
        return sprintf(buf, "%d\n",
                       channel_latency(channel,
                                       vmbus_connection.monitor_pages[1]));
}
static VMBUS_CHAN_ATTR(latency, S_IRUGO, channel_latency_show, NULL);

static ssize_t channel_interrupts_show(const struct vmbus_channel *channel, char *buf)
{
        return sprintf(buf, "%llu\n", channel->interrupts);
}
static VMBUS_CHAN_ATTR(interrupts, S_IRUGO, channel_interrupts_show, NULL);

static ssize_t channel_events_show(const struct vmbus_channel *channel, char *buf)
{
        return sprintf(buf, "%llu\n", channel->sig_events);
}
static VMBUS_CHAN_ATTR(events, S_IRUGO, channel_events_show, NULL);

static ssize_t subchannel_monitor_id_show(const struct vmbus_channel *channel,
                                          char *buf)
{
        return sprintf(buf, "%u\n", channel->offermsg.monitorid);
}
static VMBUS_CHAN_ATTR(monitor_id, S_IRUGO, subchannel_monitor_id_show, NULL);

static ssize_t subchannel_id_show(const struct vmbus_channel *channel,
                                  char *buf)
{
        return sprintf(buf, "%u\n",
                       channel->offermsg.offer.sub_channel_index);
}
static VMBUS_CHAN_ATTR_RO(subchannel_id);

static struct attribute *vmbus_chan_attrs[] = {
        &chan_attr_out_mask.attr,
        &chan_attr_in_mask.attr,
        &chan_attr_read_avail.attr,
        &chan_attr_write_avail.attr,
        &chan_attr_cpu.attr,
        &chan_attr_pending.attr,
        &chan_attr_latency.attr,
        &chan_attr_interrupts.attr,
        &chan_attr_events.attr,
        &chan_attr_monitor_id.attr,
        &chan_attr_subchannel_id.attr,
        NULL
};

static struct kobj_type vmbus_chan_ktype = {
        .sysfs_ops = &vmbus_chan_sysfs_ops,
        .release = vmbus_chan_release,
        .default_attrs = vmbus_chan_attrs,
};

/*
 * vmbus_add_channel_kobj - setup a sub-directory under device/channels
 */
int vmbus_add_channel_kobj(struct hv_device *dev, struct vmbus_channel *channel)
{
        struct kobject *kobj = &channel->kobj;
        u32 relid = channel->offermsg.child_relid;
        int ret;

        kobj->kset = dev->channels_kset;
        ret = kobject_init_and_add(kobj, &vmbus_chan_ktype, NULL,
                                   "%u", relid);
        if (ret)
                return ret;

        kobject_uevent(kobj, KOBJ_ADD);

        return 0;
}

/*
 * vmbus_device_create - Creates and registers a new child device
 * on the vmbus.
 */
struct hv_device *vmbus_device_create(const uuid_le *type,
                                      const uuid_le *instance,
                                      struct vmbus_channel *channel)
{
        struct hv_device *child_device_obj;

        child_device_obj = kzalloc(sizeof(struct hv_device), GFP_KERNEL);
        if (!child_device_obj) {
                pr_err("Unable to allocate device object for child device\n");
                return NULL;
        }

        child_device_obj->channel = channel;
        memcpy(&child_device_obj->dev_type, type, sizeof(uuid_le));
        memcpy(&child_device_obj->dev_instance, instance,
               sizeof(uuid_le));
        child_device_obj->vendor_id = 0x1414; /* MSFT vendor ID */


        return child_device_obj;
}

/*
 * vmbus_device_register - Register the child device
 */
int vmbus_device_register(struct hv_device *child_device_obj)
{
        struct kobject *kobj = &child_device_obj->device.kobj;
        int ret;

        dev_set_name(&child_device_obj->device, "%pUl",
                     child_device_obj->channel->offermsg.offer.if_instance.b);

        child_device_obj->device.bus = &hv_bus;
        child_device_obj->device.parent = &hv_acpi_dev->dev;
        child_device_obj->device.release = vmbus_device_release;

        /*
         * Register with the LDM. This will kick off the driver/device
         * binding...which will eventually call vmbus_match() and vmbus_probe()
         */
        ret = device_register(&child_device_obj->device);
        if (ret) {
                pr_err("Unable to register child device\n");
                return ret;
        }

        child_device_obj->channels_kset = kset_create_and_add("channels",
                                                              NULL, kobj);
        if (!child_device_obj->channels_kset) {
                ret = -ENOMEM;
                goto err_dev_unregister;
        }

        ret = vmbus_add_channel_kobj(child_device_obj,
                                     child_device_obj->channel);
        if (ret) {
                pr_err("Unable to register primary channeln");
                goto err_kset_unregister;
        }

        return 0;

err_kset_unregister:
        kset_unregister(child_device_obj->channels_kset);

err_dev_unregister:
        device_unregister(&child_device_obj->device);
        return ret;
}

/*
 * vmbus_device_unregister - Remove the specified child device
 * from the vmbus.
 */
void vmbus_device_unregister(struct hv_device *device_obj)
{
        pr_debug("child device %s unregistered\n",
                dev_name(&device_obj->device));

        kset_unregister(device_obj->channels_kset);

        /*
         * Kick off the process of unregistering the device.
         * This will call vmbus_remove() and eventually vmbus_device_release()
         */
        device_unregister(&device_obj->device);
}


/*
 * VMBUS is an acpi enumerated device. Get the information we
 * need from DSDT.
 */
#define VTPM_BASE_ADDRESS 0xfed40000
static acpi_status vmbus_walk_resources(struct acpi_resource *res, void *ctx)
{
        resource_size_t start = 0;
        resource_size_t end = 0;
        struct resource *new_res;
        struct resource **old_res = &hyperv_mmio;
        struct resource **prev_res = NULL;

        switch (res->type) {

        /*
         * "Address" descriptors are for bus windows. Ignore
         * "memory" descriptors, which are for registers on
         * devices.
         */
        case ACPI_RESOURCE_TYPE_ADDRESS32:
                start = res->data.address32.address.minimum;
                end = res->data.address32.address.maximum;
                break;

        case ACPI_RESOURCE_TYPE_ADDRESS64:
                start = res->data.address64.address.minimum;
                end = res->data.address64.address.maximum;
                break;

        default:
                /* Unused resource type */
                return AE_OK;

        }
        /*
         * Ignore ranges that are below 1MB, as they're not
         * necessary or useful here.
         */
        if (end < 0x100000)
                return AE_OK;

        new_res = kzalloc(sizeof(*new_res), GFP_ATOMIC);
        if (!new_res)
                return AE_NO_MEMORY;

        /* If this range overlaps the virtual TPM, truncate it. */
        if (end > VTPM_BASE_ADDRESS && start < VTPM_BASE_ADDRESS)
                end = VTPM_BASE_ADDRESS;

        new_res->name = "hyperv mmio";
        new_res->flags = IORESOURCE_MEM;
        new_res->start = start;
        new_res->end = end;

        /*
         * If two ranges are adjacent, merge them.
         */
        do {
                if (!*old_res) {
                        *old_res = new_res;
                        break;
                }

                if (((*old_res)->end + 1) == new_res->start) {
                        (*old_res)->end = new_res->end;
                        kfree(new_res);
                        break;
                }

                if ((*old_res)->start == new_res->end + 1) {
                        (*old_res)->start = new_res->start;
                        kfree(new_res);
                        break;
                }

                if ((*old_res)->start > new_res->end) {
                        new_res->sibling = *old_res;
                        if (prev_res)
                                (*prev_res)->sibling = new_res;
                        *old_res = new_res;
                        break;
                }

                prev_res = old_res;
                old_res = &(*old_res)->sibling;

        } while (1);

        return AE_OK;
}

static int vmbus_acpi_remove(struct acpi_device *device)
{
        struct resource *cur_res;
        struct resource *next_res;

        if (hyperv_mmio) {
                if (fb_mmio) {
                        __release_region(hyperv_mmio, fb_mmio->start,
                                         resource_size(fb_mmio));
                        fb_mmio = NULL;
                }

                for (cur_res = hyperv_mmio; cur_res; cur_res = next_res) {
                        next_res = cur_res->sibling;
                        kfree(cur_res);
                }
        }

        return 0;
}

static void vmbus_reserve_fb(void)
{
        int size;
        /*
         * Make a claim for the frame buffer in the resource tree under the
         * first node, which will be the one below 4GB.  The length seems to
         * be underreported, particularly in a Generation 1 VM.  So start out
         * reserving a larger area and make it smaller until it succeeds.
         */

        if (screen_info.lfb_base) {
                if (efi_enabled(EFI_BOOT))
                        size = max_t(__u32, screen_info.lfb_size, 0x800000);
                else
                        size = max_t(__u32, screen_info.lfb_size, 0x4000000);

                for (; !fb_mmio && (size >= 0x100000); size >>= 1) {
                        fb_mmio = __request_region(hyperv_mmio,
                                                   screen_info.lfb_base, size,
                                                   fb_mmio_name, 0);
                }
        }
}

/**
 * vmbus_allocate_mmio() - Pick a memory-mapped I/O range.
 * @new:                If successful, supplied a pointer to the
 *                      allocated MMIO space.
 * @device_obj:         Identifies the caller
 * @min:                Minimum guest physical address of the
 *                      allocation
 * @max:                Maximum guest physical address
 * @size:               Size of the range to be allocated
 * @align:              Alignment of the range to be allocated
 * @fb_overlap_ok:      Whether this allocation can be allowed
 *                      to overlap the video frame buffer.
 *
 * This function walks the resources granted to VMBus by the
 * _CRS object in the ACPI namespace underneath the parent
 * "bridge" whether that's a root PCI bus in the Generation 1
 * case or a Module Device in the Generation 2 case.  It then
 * attempts to allocate from the global MMIO pool in a way that
 * matches the constraints supplied in these parameters and by
 * that _CRS.
 *
 * Return: 0 on success, -errno on failure
 */
int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
                        resource_size_t min, resource_size_t max,
                        resource_size_t size, resource_size_t align,
                        bool fb_overlap_ok)
{
        struct resource *iter, *shadow;
        resource_size_t range_min, range_max, start;
        const char *dev_n = dev_name(&device_obj->device);
        int retval;

        retval = -ENXIO;
        down(&hyperv_mmio_lock);

        /*
         * If overlaps with frame buffers are allowed, then first attempt to
         * make the allocation from within the reserved region.  Because it
         * is already reserved, no shadow allocation is necessary.
         */
        if (fb_overlap_ok && fb_mmio && !(min > fb_mmio->end) &&
            !(max < fb_mmio->start)) {

                range_min = fb_mmio->start;
                range_max = fb_mmio->end;
                start = (range_min + align - 1) & ~(align - 1);
                for (; start + size - 1 <= range_max; start += align) {
                        *new = request_mem_region_exclusive(start, size, dev_n);
                        if (*new) {
                                retval = 0;
                                goto exit;
                        }
                }
        }

        for (iter = hyperv_mmio; iter; iter = iter->sibling) {
                if ((iter->start >= max) || (iter->end <= min))
                        continue;

                range_min = iter->start;
                range_max = iter->end;
                start = (range_min + align - 1) & ~(align - 1);
                for (; start + size - 1 <= range_max; start += align) {
                        shadow = __request_region(iter, start, size, NULL,
                                                  IORESOURCE_BUSY);
                        if (!shadow)
                                continue;

                        *new = request_mem_region_exclusive(start, size, dev_n);
                        if (*new) {
                                shadow->name = (char *)*new;
                                retval = 0;
                                goto exit;
                        }

                        __release_region(iter, start, size);
                }
        }

exit:
        up(&hyperv_mmio_lock);
        return retval;
}
EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);

/**
 * vmbus_free_mmio() - Free a memory-mapped I/O range.
 * @start:              Base address of region to release.
 * @size:               Size of the range to be allocated
 *
 * This function releases anything requested by
 * vmbus_mmio_allocate().
 */
void vmbus_free_mmio(resource_size_t start, resource_size_t size)
{
        struct resource *iter;

        down(&hyperv_mmio_lock);
        for (iter = hyperv_mmio; iter; iter = iter->sibling) {
                if ((iter->start >= start + size) || (iter->end <= start))
                        continue;

                __release_region(iter, start, size);
        }
        release_mem_region(start, size);
        up(&hyperv_mmio_lock);

}
EXPORT_SYMBOL_GPL(vmbus_free_mmio);

static int vmbus_acpi_add(struct acpi_device *device)
{
        acpi_status result;
        int ret_val = -ENODEV;
        struct acpi_device *ancestor;

        hv_acpi_dev = device;

        result = acpi_walk_resources(device->handle, METHOD_NAME__CRS,
                                        vmbus_walk_resources, NULL);

        if (ACPI_FAILURE(result))
                goto acpi_walk_err;
        /*
         * Some ancestor of the vmbus acpi device (Gen1 or Gen2
         * firmware) is the VMOD that has the mmio ranges. Get that.
         */
        for (ancestor = device->parent; ancestor; ancestor = ancestor->parent) {
                result = acpi_walk_resources(ancestor->handle, METHOD_NAME__CRS,
                                             vmbus_walk_resources, NULL);

                if (ACPI_FAILURE(result))
                        continue;
                if (hyperv_mmio) {
                        vmbus_reserve_fb();
                        break;
                }
        }
        ret_val = 0;

acpi_walk_err:
        complete(&probe_event);
        if (ret_val)
                vmbus_acpi_remove(device);
        return ret_val;
}

static const struct acpi_device_id vmbus_acpi_device_ids[] = {
        {"VMBUS", 0},
        {"VMBus", 0},
        {"", 0},
};
MODULE_DEVICE_TABLE(acpi, vmbus_acpi_device_ids);

static struct acpi_driver vmbus_acpi_driver = {
        .name = "vmbus",
        .ids = vmbus_acpi_device_ids,
        .ops = {
                .add = vmbus_acpi_add,
                .remove = vmbus_acpi_remove,
        },
};

static void hv_kexec_handler(void)
{
        hv_synic_clockevents_cleanup();
        vmbus_initiate_unload(false);
        vmbus_connection.conn_state = DISCONNECTED;
        /* Make sure conn_state is set as hv_synic_cleanup checks for it */
        mb();
        cpuhp_remove_state(hyperv_cpuhp_online);
        hyperv_cleanup();
};

static void hv_crash_handler(struct pt_regs *regs)
{
        vmbus_initiate_unload(true);
        /*
         * In crash handler we can't schedule synic cleanup for all CPUs,
         * doing the cleanup for current CPU only. This should be sufficient
         * for kdump.
         */
        vmbus_connection.conn_state = DISCONNECTED;
        hv_synic_cleanup(smp_processor_id());
        hyperv_cleanup();
};

static int __init hv_acpi_init(void)
{
        int ret, t;

        if (!hv_is_hyperv_initialized())
                return -ENODEV;

        init_completion(&probe_event);

        /*
         * Get ACPI resources first.
         */
        ret = acpi_bus_register_driver(&vmbus_acpi_driver);

        if (ret)
                return ret;

        t = wait_for_completion_timeout(&probe_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        ret = vmbus_bus_init();
        if (ret)
                goto cleanup;

        hv_setup_kexec_handler(hv_kexec_handler);
        hv_setup_crash_handler(hv_crash_handler);

        return 0;

cleanup:
        acpi_bus_unregister_driver(&vmbus_acpi_driver);
        hv_acpi_dev = NULL;
        return ret;
}

static void __exit vmbus_exit(void)
{
        int cpu;

        hv_remove_kexec_handler();
        hv_remove_crash_handler();
        vmbus_connection.conn_state = DISCONNECTED;
        hv_synic_clockevents_cleanup();
        vmbus_disconnect();
        hv_remove_vmbus_irq();
        for_each_online_cpu(cpu) {
                struct hv_per_cpu_context *hv_cpu
                        = per_cpu_ptr(hv_context.cpu_context, cpu);

                tasklet_kill(&hv_cpu->msg_dpc);
        }
        vmbus_free_channels();

        if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
                unregister_die_notifier(&hyperv_die_block);
                atomic_notifier_chain_unregister(&panic_notifier_list,
                                                 &hyperv_panic_block);
        }
        bus_unregister(&hv_bus);

        cpuhp_remove_state(hyperv_cpuhp_online);
        hv_synic_free();
        acpi_bus_unregister_driver(&vmbus_acpi_driver);
}


MODULE_LICENSE("GPL");

subsys_initcall(hv_acpi_init);
module_exit(vmbus_exit);