OSCL-LXR linux-6.0.1/​drivers/​hv/​vmbus_drv.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2009, Microsoft Corporation.
  *
  * 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/isolation.h>
 #include <linux/sched/task_stack.h>
 
 #include <linux/delay.h>
 #include <linux/notifier.h>
 #include <linux/panic_notifier.h>
 #include <linux/ptrace.h>
 #include <linux/screen_info.h>
 #include <linux/kdebug.h>
 #include <linux/efi.h>
 #include <linux/random.h>
 #include <linux/kernel.h>
 #include <linux/syscore_ops.h>
 #include <linux/dma-map-ops.h>
 #include <linux/pci.h>
 #include <clocksource/hyperv_timer.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 void *hv_panic_page;
 
 static long __percpu *vmbus_evt;
 
 /* Values parsed from ACPI DSDT */
 int vmbus_irq;
 int vmbus_interrupt;
 
 /*
  * Boolean to control whether to report panic messages over Hyper-V.
  *
  * It can be set via /proc/sys/kernel/hyperv_record_panic_msg
  */
 static int sysctl_record_panic_msg = 1;
 
 static int hyperv_report_reg(void)
 {
     return !sysctl_record_panic_msg || !hv_panic_page;
 }
 
 static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,
                   void *args)
 {
     struct pt_regs *regs;
 
     vmbus_initiate_unload(true);
 
     /*
      * Hyper-V should be notified only once about a panic.  If we will be
      * doing hv_kmsg_dump() with kmsg data later, don't do the notification
      * here.
      */
     if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE
         && hyperv_report_reg()) {
         regs = current_pt_regs();
         hyperv_report_panic(regs, val, false);
     }
     return NOTIFY_DONE;
 }
 
 static int hyperv_die_event(struct notifier_block *nb, unsigned long val,
                 void *args)
 {
     struct die_args *die = args;
     struct pt_regs *regs = die->regs;
 
     /* Don't notify Hyper-V if the die event is other than oops */
     if (val != DIE_OOPS)
         return NOTIFY_DONE;
 
     /*
      * Hyper-V should be notified only once about a panic.  If we will be
      * doing hv_kmsg_dump() with kmsg data later, don't do the notification
      * here.
      */
     if (hyperv_report_reg())
         hyperv_report_panic(regs, val, true);
     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_MUTEX(hyperv_mmio_lock);
 
 static int vmbus_exists(void)
 {
     if (hv_acpi_dev == NULL)
         return -ENODEV;
 
     return 0;
 }
 
 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);
 }
 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);
 }
 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);
 
     return sprintf(buf, "vmbus:%*phN\n", UUID_SIZE, &hv_dev->dev_type);
 }
 static DEVICE_ATTR_RO(modalias);
 
 #ifdef CONFIG_NUMA
 static ssize_t numa_node_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
 {
     struct hv_device *hv_dev = device_to_hv_device(dev);
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     return sprintf(buf, "%d\n", cpu_to_node(hv_dev->channel->target_cpu));
 }
 static DEVICE_ATTR_RO(numa_node);
 #endif
 
 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[0]));
 }
 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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
                       &outbound);
     if (ret < 0)
         return ret;
 
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
                       &outbound);
     if (ret < 0)
         return ret;
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
                       &outbound);
     if (ret < 0)
         return ret;
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
                       &outbound);
     if (ret < 0)
         return ret;
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
                       &outbound);
     if (ret < 0)
         return ret;
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
     if (ret < 0)
         return ret;
 
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
     if (ret < 0)
         return ret;
 
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
     if (ret < 0)
         return ret;
 
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
     if (ret < 0)
         return ret;
 
     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;
     int ret;
 
     if (!hv_dev->channel)
         return -ENODEV;
 
     ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
     if (ret < 0)
         return ret;
 
     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;
     int buf_size = PAGE_SIZE, n_written, tot_written;
     struct list_head *cur;
 
     if (!channel)
         return -ENODEV;
 
     mutex_lock(&vmbus_connection.channel_mutex);
 
     tot_written = snprintf(buf, buf_size, "%u:%u\n",
         channel->offermsg.child_relid, channel->target_cpu);
 
     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;
     }
 
     mutex_unlock(&vmbus_connection.channel_mutex);
 
     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);
 
 static ssize_t driver_override_store(struct device *dev,
                      struct device_attribute *attr,
                      const char *buf, size_t count)
 {
     struct hv_device *hv_dev = device_to_hv_device(dev);
     int ret;
 
     ret = driver_set_override(dev, &hv_dev->driver_override, buf, count);
     if (ret)
         return ret;
 
     return count;
 }
 
 static ssize_t driver_override_show(struct device *dev,
                     struct device_attribute *attr, char *buf)
 {
     struct hv_device *hv_dev = device_to_hv_device(dev);
     ssize_t len;
 
     device_lock(dev);
     len = snprintf(buf, PAGE_SIZE, "%s\n", hv_dev->driver_override);
     device_unlock(dev);
 
     return len;
 }
 static DEVICE_ATTR_RW(driver_override);
 
 /* 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,
 #ifdef CONFIG_NUMA
     &dev_attr_numa_node.attr,
 #endif
     &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,
     &dev_attr_driver_override.attr,
     NULL,
 };
 
 /*
  * Device-level attribute_group callback function. Returns the permission for
  * each attribute, and returns 0 if an attribute is not visible.
  */
 static umode_t vmbus_dev_attr_is_visible(struct kobject *kobj,
                      struct attribute *attr, int idx)
 {
     struct device *dev = kobj_to_dev(kobj);
     const struct hv_device *hv_dev = device_to_hv_device(dev);
 
     /* Hide the monitor attributes if the monitor mechanism is not used. */
     if (!hv_dev->channel->offermsg.monitor_allocated &&
         (attr == &dev_attr_monitor_id.attr ||
          attr == &dev_attr_server_monitor_pending.attr ||
          attr == &dev_attr_client_monitor_pending.attr ||
          attr == &dev_attr_server_monitor_latency.attr ||
          attr == &dev_attr_client_monitor_latency.attr ||
          attr == &dev_attr_server_monitor_conn_id.attr ||
          attr == &dev_attr_client_monitor_conn_id.attr))
         return 0;
 
     return attr->mode;
 }
 
 static const struct attribute_group vmbus_dev_group = {
     .attrs = vmbus_dev_attrs,
     .is_visible = vmbus_dev_attr_is_visible
 };
 __ATTRIBUTE_GROUPS(vmbus_dev);
 
 /* Set up the attribute for /sys/bus/vmbus/hibernation */
 static ssize_t hibernation_show(struct bus_type *bus, char *buf)
 {
     return sprintf(buf, "%d\n", !!hv_is_hibernation_supported());
 }
 
 static BUS_ATTR_RO(hibernation);
 
 static struct attribute *vmbus_bus_attrs[] = {
     &bus_attr_hibernation.attr,
     NULL,
 };
 static const struct attribute_group vmbus_bus_group = {
     .attrs = vmbus_bus_attrs,
 };
 __ATTRIBUTE_GROUPS(vmbus_bus);
 
 /*
  * 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);
     const char *format = "MODALIAS=vmbus:%*phN";
 
     return add_uevent_var(env, format, UUID_SIZE, &dev->dev_type);
 }
 
 static const struct hv_vmbus_device_id *
 hv_vmbus_dev_match(const struct hv_vmbus_device_id *id, const guid_t *guid)
 {
     if (id == NULL)
         return NULL; /* empty device table */
 
     for (; !guid_is_null(&id->guid); id++)
         if (guid_equal(&id->guid, guid))
             return id;
 
     return NULL;
 }
 
 static const struct hv_vmbus_device_id *
 hv_vmbus_dynid_match(struct hv_driver *drv, const guid_t *guid)
 {
     const struct hv_vmbus_device_id *id = NULL;
     struct vmbus_dynid *dynid;
 
     spin_lock(&drv->dynids.lock);
     list_for_each_entry(dynid, &drv->dynids.list, node) {
         if (guid_equal(&dynid->id.guid, guid)) {
             id = &dynid->id;
             break;
         }
     }
     spin_unlock(&drv->dynids.lock);
 
     return id;
 }
 
 static const struct hv_vmbus_device_id vmbus_device_null;
 
 /*
  * 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,
                             struct hv_device *dev)
 {
     const guid_t *guid = &dev->dev_type;
     const struct hv_vmbus_device_id *id;
 
     /* When driver_override is set, only bind to the matching driver */
     if (dev->driver_override && strcmp(dev->driver_override, drv->name))
         return NULL;
 
     /* Look at the dynamic ids first, before the static ones */
     id = hv_vmbus_dynid_match(drv, guid);
     if (!id)
         id = hv_vmbus_dev_match(drv->id_table, guid);
 
     /* driver_override will always match, send a dummy id */
     if (!id && dev->driver_override)
         id = &vmbus_device_null;
 
     return id;
 }
 
 /* vmbus_add_dynid - add a new device ID to this driver and re-probe devices */
 static int vmbus_add_dynid(struct hv_driver *drv, guid_t *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);
     guid_t guid;
     ssize_t retval;
 
     retval = guid_parse(buf, &guid);
     if (retval)
         return retval;
 
     if (hv_vmbus_dynid_match(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;
     guid_t guid;
     ssize_t retval;
 
     retval = guid_parse(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 (guid_equal(&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))
         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);
     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_dma_configure -- Configure DMA coherence for VMbus device
  */
 static int vmbus_dma_configure(struct device *child_device)
 {
     /*
      * On ARM64, propagate the DMA coherence setting from the top level
      * VMbus ACPI device to the child VMbus device being added here.
      * On x86/x64 coherence is assumed and these calls have no effect.
      */
     hv_setup_dma_ops(child_device,
         device_get_dma_attr(&hv_acpi_dev->dev) == DEV_DMA_COHERENT);
     return 0;
 }
 
 /*
  * vmbus_remove - Remove a vmbus device
  */
 static void 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);
     }
 }
 
 /*
  * 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);
 }
 
 #ifdef CONFIG_PM_SLEEP
 /*
  * vmbus_suspend - Suspend a vmbus device
  */
 static int vmbus_suspend(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 0;
 
     drv = drv_to_hv_drv(child_device->driver);
     if (!drv->suspend)
         return -EOPNOTSUPP;
 
     return drv->suspend(dev);
 }
 
 /*
  * vmbus_resume - Resume a vmbus device
  */
 static int vmbus_resume(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 0;
 
     drv = drv_to_hv_drv(child_device->driver);
     if (!drv->resume)
         return -EOPNOTSUPP;
 
     return drv->resume(dev);
 }
 #else
 #define vmbus_suspend NULL
 #define vmbus_resume NULL
 #endif /* CONFIG_PM_SLEEP */
 
 /*
  * 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;
 
     hv_debug_rm_dev_dir(hv_dev);
 
     mutex_lock(&vmbus_connection.channel_mutex);
     hv_process_channel_removal(channel);
     mutex_unlock(&vmbus_connection.channel_mutex);
     kfree(hv_dev);
 }
 
 /*
  * Note: we must use the "noirq" ops: see the comment before vmbus_bus_pm.
  *
  * suspend_noirq/resume_noirq are set to NULL to support Suspend-to-Idle: we
  * shouldn't suspend the vmbus devices upon Suspend-to-Idle, otherwise there
  * is no way to wake up a Generation-2 VM.
  *
  * The other 4 ops are for hibernation.
  */
 
 static const struct dev_pm_ops vmbus_pm = {
     .suspend_noirq  = NULL,
     .resume_noirq   = NULL,
     .freeze_noirq   = vmbus_suspend,
     .thaw_noirq = vmbus_resume,
     .poweroff_noirq = vmbus_suspend,
     .restore_noirq  = vmbus_resume,
 };
 
 /* 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,
     .dma_configure =    vmbus_dma_configure,
     .dev_groups =       vmbus_dev_groups,
     .drv_groups =       vmbus_drv_groups,
     .bus_groups =       vmbus_bus_groups,
     .pm =           &vmbus_pm,
 };
 
 struct onmessage_work_context {
     struct work_struct work;
     struct {
         struct hv_message_header header;
         u8 payload[];
     } 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((struct vmbus_channel_message_header *)
             &ctx->msg.payload);
     kfree(ctx);
 }
 
 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_copy, *msg = (struct hv_message *)page_addr +
                   VMBUS_MESSAGE_SINT;
     struct vmbus_channel_message_header *hdr;
     enum vmbus_channel_message_type msgtype;
     const struct vmbus_channel_message_table_entry *entry;
     struct onmessage_work_context *ctx;
     __u8 payload_size;
     u32 message_type;
 
     /*
      * 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
      * it is being used in 'struct vmbus_channel_message_header' definition
      * which is supposed to match hypervisor ABI.
      */
     BUILD_BUG_ON(sizeof(enum vmbus_channel_message_type) != sizeof(u32));
 
     /*
      * Since the message is in memory shared with the host, an erroneous or
      * malicious Hyper-V could modify the message while vmbus_on_msg_dpc()
      * or individual message handlers are executing; to prevent this, copy
      * the message into private memory.
      */
     memcpy(&msg_copy, msg, sizeof(struct hv_message));
 
     message_type = msg_copy.header.message_type;
     if (message_type == HVMSG_NONE)
         /* no msg */
         return;
 
     hdr = (struct vmbus_channel_message_header *)msg_copy.u.payload;
     msgtype = hdr->msgtype;
 
     trace_vmbus_on_msg_dpc(hdr);
 
     if (msgtype >= CHANNELMSG_COUNT) {
         WARN_ONCE(1, "unknown msgtype=%d\n", msgtype);
         goto msg_handled;
     }
 
     payload_size = msg_copy.header.payload_size;
     if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) {
         WARN_ONCE(1, "payload size is too large (%d)\n", payload_size);
         goto msg_handled;
     }
 
     entry = &channel_message_table[msgtype];
 
     if (!entry->message_handler)
         goto msg_handled;
 
     if (payload_size < entry->min_payload_len) {
         WARN_ONCE(1, "message too short: msgtype=%d len=%d\n", msgtype, payload_size);
         goto msg_handled;
     }
 
     if (entry->handler_type == VMHT_BLOCKING) {
         ctx = kmalloc(struct_size(ctx, msg.payload, payload_size), GFP_ATOMIC);
         if (ctx == NULL)
             return;
 
         INIT_WORK(&ctx->work, vmbus_onmessage_work);
         memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size);
 
         /*
          * The host can generate a rescind message while we
          * may still be handling the original offer. We deal with
          * this condition by relying on the synchronization provided
          * by offer_in_progress and by channel_mutex.  See also the
          * inline comments in vmbus_onoffer_rescind().
          */
         switch (msgtype) {
         case CHANNELMSG_RESCIND_CHANNELOFFER:
             /*
              * If we are handling the rescind message;
              * schedule the work on the global work queue.
              *
              * The OFFER message and the RESCIND message should
              * not be handled by the same serialized work queue,
              * because the OFFER handler may call vmbus_open(),
              * which tries to open the channel by sending an
              * OPEN_CHANNEL message to the host and waits for
              * the host's response; however, if the host has
              * rescinded the channel before it receives the
              * OPEN_CHANNEL message, the host just silently
              * ignores the OPEN_CHANNEL message; as a result,
              * the guest's OFFER handler hangs for ever, if we
              * handle the RESCIND message in the same serialized
              * work queue: the RESCIND handler can not start to
              * run before the OFFER handler finishes.
              */
             if (vmbus_connection.ignore_any_offer_msg)
                 break;
             queue_work(vmbus_connection.rescind_work_queue, &ctx->work);
             break;
 
         case CHANNELMSG_OFFERCHANNEL:
             /*
              * The host sends the offer message of a given channel
              * before sending the rescind message of the same
              * channel.  These messages are sent to the guest's
              * connect CPU; the guest then starts processing them
              * in the tasklet handler on this CPU:
              *
              * VMBUS_CONNECT_CPU
              *
              * [vmbus_on_msg_dpc()]
              * atomic_inc()  // CHANNELMSG_OFFERCHANNEL
              * queue_work()
              * ...
              * [vmbus_on_msg_dpc()]
              * schedule_work()  // CHANNELMSG_RESCIND_CHANNELOFFER
              *
              * We rely on the memory-ordering properties of the
              * queue_work() and schedule_work() primitives, which
              * guarantee that the atomic increment will be visible
              * to the CPUs which will execute the offer & rescind
              * works by the time these works will start execution.
              */
             if (vmbus_connection.ignore_any_offer_msg)
                 break;
             atomic_inc(&vmbus_connection.offer_in_progress);
             fallthrough;
 
         default:
             queue_work(vmbus_connection.work_queue, &ctx->work);
         }
     } else
         entry->message_handler(hdr);
 
 msg_handled:
     vmbus_signal_eom(msg, message_type);
 }
 
 #ifdef CONFIG_PM_SLEEP
 /*
  * Fake RESCIND_CHANNEL messages to clean up hv_sock channels by force for
  * hibernation, because hv_sock connections can not persist across hibernation.
  */
 static void vmbus_force_channel_rescinded(struct vmbus_channel *channel)
 {
     struct onmessage_work_context *ctx;
     struct vmbus_channel_rescind_offer *rescind;
 
     WARN_ON(!is_hvsock_channel(channel));
 
     /*
      * Allocation size is small and the allocation should really not fail,
      * otherwise the state of the hv_sock connections ends up in limbo.
      */
     ctx = kzalloc(sizeof(*ctx) + sizeof(*rescind),
               GFP_KERNEL | __GFP_NOFAIL);
 
     /*
      * So far, these are not really used by Linux. Just set them to the
      * reasonable values conforming to the definitions of the fields.
      */
     ctx->msg.header.message_type = 1;
     ctx->msg.header.payload_size = sizeof(*rescind);
 
     /* These values are actually used by Linux. */
     rescind = (struct vmbus_channel_rescind_offer *)ctx->msg.payload;
     rescind->header.msgtype = CHANNELMSG_RESCIND_CHANNELOFFER;
     rescind->child_relid = channel->offermsg.child_relid;
 
     INIT_WORK(&ctx->work, vmbus_onmessage_work);
 
     queue_work(vmbus_connection.work_queue, &ctx->work);
 }
 #endif /* CONFIG_PM_SLEEP */
 
 /*
  * 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;
 
     /*
      * 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) {
         void (*callback_fn)(void *context);
         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;
 
         /*
          * Pairs with the kfree_rcu() in vmbus_chan_release().
          * Guarantees that the channel data structure doesn't
          * get freed while the channel pointer below is being
          * dereferenced.
          */
         rcu_read_lock();
 
         /* Find channel based on relid */
         channel = relid2channel(relid);
         if (channel == NULL)
             goto sched_unlock_rcu;
 
         if (channel->rescind)
             goto sched_unlock_rcu;
 
         /*
          * Make sure that the ring buffer data structure doesn't get
          * freed while we dereference the ring buffer pointer.  Test
          * for the channel's onchannel_callback being NULL within a
          * sched_lock critical section.  See also the inline comments
          * in vmbus_reset_channel_cb().
          */
         spin_lock(&channel->sched_lock);
 
         callback_fn = channel->onchannel_callback;
         if (unlikely(callback_fn == NULL))
             goto sched_unlock;
 
         trace_vmbus_chan_sched(channel);
 
         ++channel->interrupts;
 
         switch (channel->callback_mode) {
         case HV_CALL_ISR:
             (*callback_fn)(channel->channel_callback_context);
             break;
 
         case HV_CALL_BATCHED:
             hv_begin_read(&channel->inbound);
             fallthrough;
         case HV_CALL_DIRECT:
             tasklet_schedule(&channel->callback_event);
         }
 
 sched_unlock:
         spin_unlock(&channel->sched_lock);
 sched_unlock_rcu:
         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;
     struct hv_message *msg;
 
     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_stimer0_isr();
             vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
         } else
             tasklet_schedule(&hv_cpu->msg_dpc);
     }
 
     add_interrupt_randomness(vmbus_interrupt);
 }
 
 static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id)
 {
     vmbus_isr();
     return IRQ_HANDLED;
 }
 
 /*
  * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
  * buffer and call into Hyper-V to transfer the data.
  */
 static void hv_kmsg_dump(struct kmsg_dumper *dumper,
              enum kmsg_dump_reason reason)
 {
     struct kmsg_dump_iter iter;
     size_t bytes_written;
 
     /* We are only interested in panics. */
     if ((reason != KMSG_DUMP_PANIC) || (!sysctl_record_panic_msg))
         return;
 
     /*
      * Write dump contents to the page. No need to synchronize; panic should
      * be single-threaded.
      */
     kmsg_dump_rewind(&iter);
     kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
                  &bytes_written);
     if (!bytes_written)
         return;
     /*
      * P3 to contain the physical address of the panic page & P4 to
      * contain the size of the panic data in that page. Rest of the
      * registers are no-op when the NOTIFY_MSG flag is set.
      */
     hv_set_register(HV_REGISTER_CRASH_P0, 0);
     hv_set_register(HV_REGISTER_CRASH_P1, 0);
     hv_set_register(HV_REGISTER_CRASH_P2, 0);
     hv_set_register(HV_REGISTER_CRASH_P3, virt_to_phys(hv_panic_page));
     hv_set_register(HV_REGISTER_CRASH_P4, bytes_written);
 
     /*
      * Let Hyper-V know there is crash data available along with
      * the panic message.
      */
     hv_set_register(HV_REGISTER_CRASH_CTL,
            (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
 }
 
 static struct kmsg_dumper hv_kmsg_dumper = {
     .dump = hv_kmsg_dump,
 };
 
 static void hv_kmsg_dump_register(void)
 {
     int ret;
 
     hv_panic_page = hv_alloc_hyperv_zeroed_page();
     if (!hv_panic_page) {
         pr_err("Hyper-V: panic message page memory allocation failed\n");
         return;
     }
 
     ret = kmsg_dump_register(&hv_kmsg_dumper);
     if (ret) {
         pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
         hv_free_hyperv_page((unsigned long)hv_panic_page);
         hv_panic_page = NULL;
     }
 }
 
 static struct ctl_table_header *hv_ctl_table_hdr;
 
 /*
  * sysctl option to allow the user to control whether kmsg data should be
  * reported to Hyper-V on panic.
  */
 static struct ctl_table hv_ctl_table[] = {
     {
         .procname       = "hyperv_record_panic_msg",
         .data           = &sysctl_record_panic_msg,
         .maxlen         = sizeof(int),
         .mode           = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE
     },
     {}
 };
 
 static struct ctl_table hv_root_table[] = {
     {
         .procname   = "kernel",
         .mode       = 0555,
         .child      = hv_ctl_table
     },
     {}
 };
 
 /*
  * 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;
 
     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;
 
     /*
      * VMbus interrupts are best modeled as per-cpu interrupts. If
      * on an architecture with support for per-cpu IRQs (e.g. ARM64),
      * allocate a per-cpu IRQ using standard Linux kernel functionality.
      * If not on such an architecture (e.g., x86/x64), then rely on
      * code in the arch-specific portion of the code tree to connect
      * the VMbus interrupt handler.
      */
 
     if (vmbus_irq == -1) {
         hv_setup_vmbus_handler(vmbus_isr);
     } else {
         vmbus_evt = alloc_percpu(long);
         ret = request_percpu_irq(vmbus_irq, vmbus_percpu_isr,
                 "Hyper-V VMbus", vmbus_evt);
         if (ret) {
             pr_err("Can't request Hyper-V VMbus IRQ %d, Err %d",
                     vmbus_irq, ret);
             free_percpu(vmbus_evt);
             goto err_setup;
         }
     }
 
     ret = hv_synic_alloc();
     if (ret)
         goto err_alloc;
 
     /*
      * Initialize the per-cpu interrupt state and stimer state.
      * Then 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_cpuhp;
     hyperv_cpuhp_online = ret;
 
     ret = vmbus_connect();
     if (ret)
         goto err_connect;
 
     if (hv_is_isolation_supported())
         sysctl_record_panic_msg = 0;
 
     /*
      * Only register if the crash MSRs are available
      */
     if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
         u64 hyperv_crash_ctl;
         /*
          * Panic message recording (sysctl_record_panic_msg)
          * is enabled by default in non-isolated guests and
          * disabled by default in isolated guests; the panic
          * message recording won't be available in isolated
          * guests should the following registration fail.
          */
         hv_ctl_table_hdr = register_sysctl_table(hv_root_table);
         if (!hv_ctl_table_hdr)
             pr_err("Hyper-V: sysctl table register error");
 
         /*
          * Register for panic kmsg callback only if the right
          * capability is supported by the hypervisor.
          */
         hyperv_crash_ctl = hv_get_register(HV_REGISTER_CRASH_CTL);
         if (hyperv_crash_ctl & HV_CRASH_CTL_CRASH_NOTIFY_MSG)
             hv_kmsg_dump_register();
 
         register_die_notifier(&hyperv_die_block);
     }
 
     /*
      * Always register the panic notifier because we need to unload
      * the VMbus channel connection to prevent any VMbus
      * activity after the VM panics.
      */
     atomic_notifier_chain_register(&panic_notifier_list,
                    &hyperv_panic_block);
 
     vmbus_request_offers();
 
     return 0;
 
 err_connect:
     cpuhp_remove_state(hyperv_cpuhp_online);
 err_cpuhp:
     hv_synic_free();
 err_alloc:
     if (vmbus_irq == -1) {
         hv_remove_vmbus_handler();
     } else {
         free_percpu_irq(vmbus_irq, vmbus_evt);
         free_percpu(vmbus_evt);
     }
 err_setup:
     bus_unregister(&hv_bus);
     unregister_sysctl_table(hv_ctl_table_hdr);
     hv_ctl_table_hdr = NULL;
     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)(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);
     struct vmbus_channel *chan
         = container_of(kobj, struct vmbus_channel, kobj);
 
     if (!attribute->show)
         return -EIO;
 
     return attribute->show(chan, buf);
 }
 
 static ssize_t vmbus_chan_attr_store(struct kobject *kobj,
                      struct attribute *attr, const char *buf,
                      size_t count)
 {
     const struct vmbus_chan_attribute *attribute
         = container_of(attr, struct vmbus_chan_attribute, attr);
     struct vmbus_channel *chan
         = container_of(kobj, struct vmbus_channel, kobj);
 
     if (!attribute->store)
         return -EIO;
 
     return attribute->store(chan, buf, count);
 }
 
 static const struct sysfs_ops vmbus_chan_sysfs_ops = {
     .show = vmbus_chan_attr_show,
     .store = vmbus_chan_attr_store,
 };
 
 static ssize_t out_mask_show(struct vmbus_channel *channel, char *buf)
 {
     struct hv_ring_buffer_info *rbi = &channel->outbound;
     ssize_t ret;
 
     mutex_lock(&rbi->ring_buffer_mutex);
     if (!rbi->ring_buffer) {
         mutex_unlock(&rbi->ring_buffer_mutex);
         return -EINVAL;
     }
 
     ret = sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask);
     mutex_unlock(&rbi->ring_buffer_mutex);
     return ret;
 }
 static VMBUS_CHAN_ATTR_RO(out_mask);
 
 static ssize_t in_mask_show(struct vmbus_channel *channel, char *buf)
 {
     struct hv_ring_buffer_info *rbi = &channel->inbound;
     ssize_t ret;
 
     mutex_lock(&rbi->ring_buffer_mutex);
     if (!rbi->ring_buffer) {
         mutex_unlock(&rbi->ring_buffer_mutex);
         return -EINVAL;
     }
 
     ret = sprintf(buf, "%u\n", rbi->ring_buffer->interrupt_mask);
     mutex_unlock(&rbi->ring_buffer_mutex);
     return ret;
 }
 static VMBUS_CHAN_ATTR_RO(in_mask);
 
 static ssize_t read_avail_show(struct vmbus_channel *channel, char *buf)
 {
     struct hv_ring_buffer_info *rbi = &channel->inbound;
     ssize_t ret;
 
     mutex_lock(&rbi->ring_buffer_mutex);
     if (!rbi->ring_buffer) {
         mutex_unlock(&rbi->ring_buffer_mutex);
         return -EINVAL;
     }
 
     ret = sprintf(buf, "%u\n", hv_get_bytes_to_read(rbi));
     mutex_unlock(&rbi->ring_buffer_mutex);
     return ret;
 }
 static VMBUS_CHAN_ATTR_RO(read_avail);
 
 static ssize_t write_avail_show(struct vmbus_channel *channel, char *buf)
 {
     struct hv_ring_buffer_info *rbi = &channel->outbound;
     ssize_t ret;
 
     mutex_lock(&rbi->ring_buffer_mutex);
     if (!rbi->ring_buffer) {
         mutex_unlock(&rbi->ring_buffer_mutex);
         return -EINVAL;
     }
 
     ret = sprintf(buf, "%u\n", hv_get_bytes_to_write(rbi));
     mutex_unlock(&rbi->ring_buffer_mutex);
     return ret;
 }
 static VMBUS_CHAN_ATTR_RO(write_avail);
 
 static ssize_t target_cpu_show(struct vmbus_channel *channel, char *buf)
 {
     return sprintf(buf, "%u\n", channel->target_cpu);
 }
 static ssize_t target_cpu_store(struct vmbus_channel *channel,
                 const char *buf, size_t count)
 {
     u32 target_cpu, origin_cpu;
     ssize_t ret = count;
 
     if (vmbus_proto_version < VERSION_WIN10_V4_1)
         return -EIO;
 
     if (sscanf(buf, "%uu", &target_cpu) != 1)
         return -EIO;
 
     /* Validate target_cpu for the cpumask_test_cpu() operation below. */
     if (target_cpu >= nr_cpumask_bits)
         return -EINVAL;
 
     if (!cpumask_test_cpu(target_cpu, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ)))
         return -EINVAL;
 
     /* No CPUs should come up or down during this. */
     cpus_read_lock();
 
     if (!cpu_online(target_cpu)) {
         cpus_read_unlock();
         return -EINVAL;
     }
 
     /*
      * Synchronizes target_cpu_store() and channel closure:
      *
      * { Initially: state = CHANNEL_OPENED }
      *
      * CPU1             CPU2
      *
      * [target_cpu_store()]     [vmbus_disconnect_ring()]
      *
      * LOCK channel_mutex       LOCK channel_mutex
      * LOAD r1 = state      LOAD r2 = state
      * IF (r1 == CHANNEL_OPENED)    IF (r2 == CHANNEL_OPENED)
      *   SEND MODIFYCHANNEL       STORE state = CHANNEL_OPEN
      *   [...]            SEND CLOSECHANNEL
      * UNLOCK channel_mutex     UNLOCK channel_mutex
      *
      * Forbids: r1 == r2 == CHANNEL_OPENED (i.e., CPU1's LOCK precedes
      *      CPU2's LOCK) && CPU2's SEND precedes CPU1's SEND
      *
      * Note.  The host processes the channel messages "sequentially", in
      * the order in which they are received on a per-partition basis.
      */
     mutex_lock(&vmbus_connection.channel_mutex);
 
     /*
      * Hyper-V will ignore MODIFYCHANNEL messages for "non-open" channels;
      * avoid sending the message and fail here for such channels.
      */
     if (channel->state != CHANNEL_OPENED_STATE) {
         ret = -EIO;
         goto cpu_store_unlock;
     }
 
     origin_cpu = channel->target_cpu;
     if (target_cpu == origin_cpu)
         goto cpu_store_unlock;
 
     if (vmbus_send_modifychannel(channel,
                      hv_cpu_number_to_vp_number(target_cpu))) {
         ret = -EIO;
         goto cpu_store_unlock;
     }
 
     /*
      * For version before VERSION_WIN10_V5_3, the following warning holds:
      *
      * Warning.  At this point, there is *no* guarantee that the host will
      * have successfully processed the vmbus_send_modifychannel() request.
      * See the header comment of vmbus_send_modifychannel() for more info.
      *
      * Lags in the processing of the above vmbus_send_modifychannel() can
      * result in missed interrupts if the "old" target CPU is taken offline
      * before Hyper-V starts sending interrupts to the "new" target CPU.
      * But apart from this offlining scenario, the code tolerates such
      * lags.  It will function correctly even if a channel interrupt comes
      * in on a CPU that is different from the channel target_cpu value.
      */
 
     channel->target_cpu = target_cpu;
 
     /* See init_vp_index(). */
     if (hv_is_perf_channel(channel))
         hv_update_allocated_cpus(origin_cpu, target_cpu);
 
     /* Currently set only for storvsc channels. */
     if (channel->change_target_cpu_callback) {
         (*channel->change_target_cpu_callback)(channel,
                 origin_cpu, target_cpu);
     }
 
 cpu_store_unlock:
     mutex_unlock(&vmbus_connection.channel_mutex);
     cpus_read_unlock();
     return ret;
 }
 static VMBUS_CHAN_ATTR(cpu, 0644, target_cpu_show, target_cpu_store);
 
 static ssize_t channel_pending_show(struct vmbus_channel *channel,
                     char *buf)
 {
     return sprintf(buf, "%d\n",
                channel_pending(channel,
                        vmbus_connection.monitor_pages[1]));
 }
 static VMBUS_CHAN_ATTR(pending, 0444, channel_pending_show, NULL);
 
 static ssize_t channel_latency_show(struct vmbus_channel *channel,
                     char *buf)
 {
     return sprintf(buf, "%d\n",
                channel_latency(channel,
                        vmbus_connection.monitor_pages[1]));
 }
 static VMBUS_CHAN_ATTR(latency, 0444, channel_latency_show, NULL);
 
 static ssize_t channel_interrupts_show(struct vmbus_channel *channel, char *buf)
 {
     return sprintf(buf, "%llu\n", channel->interrupts);
 }
 static VMBUS_CHAN_ATTR(interrupts, 0444, channel_interrupts_show, NULL);
 
 static ssize_t channel_events_show(struct vmbus_channel *channel, char *buf)
 {
     return sprintf(buf, "%llu\n", channel->sig_events);
 }
 static VMBUS_CHAN_ATTR(events, 0444, channel_events_show, NULL);
 
 static ssize_t channel_intr_in_full_show(struct vmbus_channel *channel,
                      char *buf)
 {
     return sprintf(buf, "%llu\n",
                (unsigned long long)channel->intr_in_full);
 }
 static VMBUS_CHAN_ATTR(intr_in_full, 0444, channel_intr_in_full_show, NULL);
 
 static ssize_t channel_intr_out_empty_show(struct vmbus_channel *channel,
                        char *buf)
 {
     return sprintf(buf, "%llu\n",
                (unsigned long long)channel->intr_out_empty);
 }
 static VMBUS_CHAN_ATTR(intr_out_empty, 0444, channel_intr_out_empty_show, NULL);
 
 static ssize_t channel_out_full_first_show(struct vmbus_channel *channel,
                        char *buf)
 {
     return sprintf(buf, "%llu\n",
                (unsigned long long)channel->out_full_first);
 }
 static VMBUS_CHAN_ATTR(out_full_first, 0444, channel_out_full_first_show, NULL);
 
 static ssize_t channel_out_full_total_show(struct vmbus_channel *channel,
                        char *buf)
 {
     return sprintf(buf, "%llu\n",
                (unsigned long long)channel->out_full_total);
 }
 static VMBUS_CHAN_ATTR(out_full_total, 0444, channel_out_full_total_show, NULL);
 
 static ssize_t subchannel_monitor_id_show(struct vmbus_channel *channel,
                       char *buf)
 {
     return sprintf(buf, "%u\n", channel->offermsg.monitorid);
 }
 static VMBUS_CHAN_ATTR(monitor_id, 0444, subchannel_monitor_id_show, NULL);
 
 static ssize_t subchannel_id_show(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_intr_in_full.attr,
     &chan_attr_intr_out_empty.attr,
     &chan_attr_out_full_first.attr,
     &chan_attr_out_full_total.attr,
     &chan_attr_monitor_id.attr,
     &chan_attr_subchannel_id.attr,
     NULL
 };
 
 /*
  * Channel-level attribute_group callback function. Returns the permission for
  * each attribute, and returns 0 if an attribute is not visible.
  */
 static umode_t vmbus_chan_attr_is_visible(struct kobject *kobj,
                       struct attribute *attr, int idx)
 {
     const struct vmbus_channel *channel =
         container_of(kobj, struct vmbus_channel, kobj);
 
     /* Hide the monitor attributes if the monitor mechanism is not used. */
     if (!channel->offermsg.monitor_allocated &&
         (attr == &chan_attr_pending.attr ||
          attr == &chan_attr_latency.attr ||
          attr == &chan_attr_monitor_id.attr))
         return 0;
 
     return attr->mode;
 }
 
 static struct attribute_group vmbus_chan_group = {
     .attrs = vmbus_chan_attrs,
     .is_visible = vmbus_chan_attr_is_visible
 };
 
 static struct kobj_type vmbus_chan_ktype = {
     .sysfs_ops = &vmbus_chan_sysfs_ops,
     .release = vmbus_chan_release,
 };
 
 /*
  * vmbus_add_channel_kobj - setup a sub-directory under device/channels
  */
 int vmbus_add_channel_kobj(struct hv_device *dev, struct vmbus_channel *channel)
 {
     const struct device *device = &dev->device;
     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) {
         kobject_put(kobj);
         return ret;
     }
 
     ret = sysfs_create_group(kobj, &vmbus_chan_group);
 
     if (ret) {
         /*
          * The calling functions' error handling paths will cleanup the
          * empty channel directory.
          */
         kobject_put(kobj);
         dev_err(device, "Unable to set up channel sysfs files\n");
         return ret;
     }
 
     kobject_uevent(kobj, KOBJ_ADD);
 
     return 0;
 }
 
 /*
  * vmbus_remove_channel_attr_group - remove the channel's attribute group
  */
 void vmbus_remove_channel_attr_group(struct vmbus_channel *channel)
 {
     sysfs_remove_group(&channel->kobj, &vmbus_chan_group);
 }
 
 /*
  * vmbus_device_create - Creates and registers a new child device
  * on the vmbus.
  */
 struct hv_device *vmbus_device_create(const guid_t *type,
                       const guid_t *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;
     guid_copy(&child_device_obj->dev_type, type);
     guid_copy(&child_device_obj->dev_instance, instance);
     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);
 
     child_device_obj->device.bus = &hv_bus;
     child_device_obj->device.parent = &hv_acpi_dev->dev;
     child_device_obj->device.release = vmbus_device_release;
 
     child_device_obj->device.dma_parms = &child_device_obj->dma_parms;
     child_device_obj->device.dma_mask = &child_device_obj->dma_mask;
     dma_set_mask(&child_device_obj->device, DMA_BIT_MASK(64));
 
     /*
      * 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;
     }
     hv_debug_add_dev_dir(child_device_obj);
 
     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;
     struct resource r;
 
     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;
 
     /*
      * The IRQ information is needed only on ARM64, which Hyper-V
      * sets up in the extended format. IRQ information is present
      * on x86/x64 in the non-extended format but it is not used by
      * Linux. So don't bother checking for the non-extended format.
      */
     case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
         if (!acpi_dev_resource_interrupt(res, 0, &r)) {
             pr_err("Unable to parse Hyper-V ACPI interrupt\n");
             return AE_ERROR;
         }
         /* ARM64 INTID for VMbus */
         vmbus_interrupt = res->data.extended_irq.interrupts[0];
         /* Linux IRQ number */
         vmbus_irq = r.start;
         return AE_OK;
 
     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)
 {
     resource_size_t start = 0, size;
     struct pci_dev *pdev;
 
     if (efi_enabled(EFI_BOOT)) {
         /* Gen2 VM: get FB base from EFI framebuffer */
         start = screen_info.lfb_base;
         size = max_t(__u32, screen_info.lfb_size, 0x800000);
     } else {
         /* Gen1 VM: get FB base from PCI */
         pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,
                       PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
         if (!pdev)
             return;
 
         if (pdev->resource[0].flags & IORESOURCE_MEM) {
             start = pci_resource_start(pdev, 0);
             size = pci_resource_len(pdev, 0);
         }
 
         /*
          * Release the PCI device so hyperv_drm or hyperv_fb driver can
          * grab it later.
          */
         pci_dev_put(pdev);
     }
 
     if (!start)
         return;
 
     /*
      * 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.
      */
     for (; !fb_mmio && (size >= 0x100000); size >>= 1)
         fb_mmio = __request_region(hyperv_mmio, start, 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, end;
     const char *dev_n = dev_name(&device_obj->device);
     int retval;
 
     retval = -ENXIO;
     mutex_lock(&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) {
             end = start + size - 1;
 
             /* Skip the whole fb_mmio region if not fb_overlap_ok */
             if (!fb_overlap_ok && fb_mmio &&
                 (((start >= fb_mmio->start) && (start <= fb_mmio->end)) ||
                  ((end >= fb_mmio->start) && (end <= fb_mmio->end))))
                 continue;
 
             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:
     mutex_unlock(&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;
 
     mutex_lock(&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);
     mutex_unlock(&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;
 
     /*
      * Older versions of Hyper-V for ARM64 fail to include the _CCA
      * method on the top level VMbus device in the DSDT. But devices
      * are hardware coherent in all current Hyper-V use cases, so fix
      * up the ACPI device to behave as if _CCA is present and indicates
      * hardware coherence.
      */
     ACPI_COMPANION_SET(&device->dev, device);
     if (IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED) &&
         device_get_dma_attr(&device->dev) == DEV_DMA_NOT_SUPPORTED) {
         pr_info("No ACPI _CCA found; assuming coherent device I/O\n");
         device->flags.cca_seen = true;
         device->flags.coherent_dma = true;
     }
 
     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;
 }
 
 #ifdef CONFIG_PM_SLEEP
 static int vmbus_bus_suspend(struct device *dev)
 {
     struct hv_per_cpu_context *hv_cpu = per_cpu_ptr(
             hv_context.cpu_context, VMBUS_CONNECT_CPU);
     struct vmbus_channel *channel, *sc;
 
     tasklet_disable(&hv_cpu->msg_dpc);
     vmbus_connection.ignore_any_offer_msg = true;
     /* The tasklet_enable() takes care of providing a memory barrier */
     tasklet_enable(&hv_cpu->msg_dpc);
 
     /* Drain all the workqueues as we are in suspend */
     drain_workqueue(vmbus_connection.rescind_work_queue);
     drain_workqueue(vmbus_connection.work_queue);
     drain_workqueue(vmbus_connection.handle_primary_chan_wq);
     drain_workqueue(vmbus_connection.handle_sub_chan_wq);
 
     mutex_lock(&vmbus_connection.channel_mutex);
     list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
         if (!is_hvsock_channel(channel))
             continue;
 
         vmbus_force_channel_rescinded(channel);
     }
     mutex_unlock(&vmbus_connection.channel_mutex);
 
     /*
      * Wait until all the sub-channels and hv_sock channels have been
      * cleaned up. Sub-channels should be destroyed upon suspend, otherwise
      * they would conflict with the new sub-channels that will be created
      * in the resume path. hv_sock channels should also be destroyed, but
      * a hv_sock channel of an established hv_sock connection can not be
      * really destroyed since it may still be referenced by the userspace
      * application, so we just force the hv_sock channel to be rescinded
      * by vmbus_force_channel_rescinded(), and the userspace application
      * will thoroughly destroy the channel after hibernation.
      *
      * Note: the counter nr_chan_close_on_suspend may never go above 0 if
      * the VM has no sub-channel and hv_sock channel, e.g. a 1-vCPU VM.
      */
     if (atomic_read(&vmbus_connection.nr_chan_close_on_suspend) > 0)
         wait_for_completion(&vmbus_connection.ready_for_suspend_event);
 
     if (atomic_read(&vmbus_connection.nr_chan_fixup_on_resume) != 0) {
         pr_err("Can not suspend due to a previous failed resuming\n");
         return -EBUSY;
     }
 
     mutex_lock(&vmbus_connection.channel_mutex);
 
     list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
         /*
          * Remove the channel from the array of channels and invalidate
          * the channel's relid.  Upon resume, vmbus_onoffer() will fix
          * up the relid (and other fields, if necessary) and add the
          * channel back to the array.
          */
         vmbus_channel_unmap_relid(channel);
         channel->offermsg.child_relid = INVALID_RELID;
 
         if (is_hvsock_channel(channel)) {
             if (!channel->rescind) {
                 pr_err("hv_sock channel not rescinded!\n");
                 WARN_ON_ONCE(1);
             }
             continue;
         }
 
         list_for_each_entry(sc, &channel->sc_list, sc_list) {
             pr_err("Sub-channel not deleted!\n");
             WARN_ON_ONCE(1);
         }
 
         atomic_inc(&vmbus_connection.nr_chan_fixup_on_resume);
     }
 
     mutex_unlock(&vmbus_connection.channel_mutex);
 
     vmbus_initiate_unload(false);
 
     /* Reset the event for the next resume. */
     reinit_completion(&vmbus_connection.ready_for_resume_event);
 
     return 0;
 }
 
 static int vmbus_bus_resume(struct device *dev)
 {
     struct vmbus_channel_msginfo *msginfo;
     size_t msgsize;
     int ret;
 
     vmbus_connection.ignore_any_offer_msg = false;
 
     /*
      * We only use the 'vmbus_proto_version', which was in use before
      * hibernation, to re-negotiate with the host.
      */
     if (!vmbus_proto_version) {
         pr_err("Invalid proto version = 0x%x\n", vmbus_proto_version);
         return -EINVAL;
     }
 
     msgsize = sizeof(*msginfo) +
           sizeof(struct vmbus_channel_initiate_contact);
 
     msginfo = kzalloc(msgsize, GFP_KERNEL);
 
     if (msginfo == NULL)
         return -ENOMEM;
 
     ret = vmbus_negotiate_version(msginfo, vmbus_proto_version);
 
     kfree(msginfo);
 
     if (ret != 0)
         return ret;
 
     WARN_ON(atomic_read(&vmbus_connection.nr_chan_fixup_on_resume) == 0);
 
     vmbus_request_offers();
 
     if (wait_for_completion_timeout(
         &vmbus_connection.ready_for_resume_event, 10 * HZ) == 0)
         pr_err("Some vmbus device is missing after suspending?\n");
 
     /* Reset the event for the next suspend. */
     reinit_completion(&vmbus_connection.ready_for_suspend_event);
 
     return 0;
 }
 #else
 #define vmbus_bus_suspend NULL
 #define vmbus_bus_resume NULL
 #endif /* CONFIG_PM_SLEEP */
 
 static const struct acpi_device_id vmbus_acpi_device_ids[] = {
     {"VMBUS", 0},
     {"VMBus", 0},
     {"", 0},
 };
 MODULE_DEVICE_TABLE(acpi, vmbus_acpi_device_ids);
 
 /*
  * Note: we must use the "no_irq" ops, otherwise hibernation can not work with
  * PCI device assignment, because "pci_dev_pm_ops" uses the "noirq" ops: in
  * the resume path, the pci "noirq" restore op runs before "non-noirq" op (see
  * resume_target_kernel() -> dpm_resume_start(), and hibernation_restore() ->
  * dpm_resume_end()). This means vmbus_bus_resume() and the pci-hyperv's
  * resume callback must also run via the "noirq" ops.
  *
  * Set suspend_noirq/resume_noirq to NULL for Suspend-to-Idle: see the comment
  * earlier in this file before vmbus_pm.
  */
 
 static const struct dev_pm_ops vmbus_bus_pm = {
     .suspend_noirq  = NULL,
     .resume_noirq   = NULL,
     .freeze_noirq   = vmbus_bus_suspend,
     .thaw_noirq = vmbus_bus_resume,
     .poweroff_noirq = vmbus_bus_suspend,
     .restore_noirq  = vmbus_bus_resume
 };
 
 static struct acpi_driver vmbus_acpi_driver = {
     .name = "vmbus",
     .ids = vmbus_acpi_device_ids,
     .ops = {
         .add = vmbus_acpi_add,
         .remove = vmbus_acpi_remove,
     },
     .drv.pm = &vmbus_bus_pm,
 };
 
 static void hv_kexec_handler(void)
 {
     hv_stimer_global_cleanup();
     vmbus_initiate_unload(false);
     /* Make sure conn_state is set as hv_synic_cleanup checks for it */
     mb();
     cpuhp_remove_state(hyperv_cpuhp_online);
 };
 
 static void hv_crash_handler(struct pt_regs *regs)
 {
     int cpu;
 
     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.
      */
     cpu = smp_processor_id();
     hv_stimer_cleanup(cpu);
     hv_synic_disable_regs(cpu);
 };
 
 static int hv_synic_suspend(void)
 {
     /*
      * When we reach here, all the non-boot CPUs have been offlined.
      * If we're in a legacy configuration where stimer Direct Mode is
      * not enabled, the stimers on the non-boot CPUs have been unbound
      * in hv_synic_cleanup() -> hv_stimer_legacy_cleanup() ->
      * hv_stimer_cleanup() -> clockevents_unbind_device().
      *
      * hv_synic_suspend() only runs on CPU0 with interrupts disabled.
      * Here we do not call hv_stimer_legacy_cleanup() on CPU0 because:
      * 1) it's unnecessary as interrupts remain disabled between
      * syscore_suspend() and syscore_resume(): see create_image() and
      * resume_target_kernel()
      * 2) the stimer on CPU0 is automatically disabled later by
      * syscore_suspend() -> timekeeping_suspend() -> tick_suspend() -> ...
      * -> clockevents_shutdown() -> ... -> hv_ce_shutdown()
      * 3) a warning would be triggered if we call
      * clockevents_unbind_device(), which may sleep, in an
      * interrupts-disabled context.
      */
 
     hv_synic_disable_regs(0);
 
     return 0;
 }
 
 static void hv_synic_resume(void)
 {
     hv_synic_enable_regs(0);
 
     /*
      * Note: we don't need to call hv_stimer_init(0), because the timer
      * on CPU0 is not unbound in hv_synic_suspend(), and the timer is
      * automatically re-enabled in timekeeping_resume().
      */
 }
 
 /* The callbacks run only on CPU0, with irqs_disabled. */
 static struct syscore_ops hv_synic_syscore_ops = {
     .suspend = hv_synic_suspend,
     .resume = hv_synic_resume,
 };
 
 static int __init hv_acpi_init(void)
 {
     int ret, t;
 
     if (!hv_is_hyperv_initialized())
         return -ENODEV;
 
     if (hv_root_partition)
         return 0;
 
     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;
     }
 
     /*
      * If we're on an architecture with a hardcoded hypervisor
      * vector (i.e. x86/x64), override the VMbus interrupt found
      * in the ACPI tables. Ensure vmbus_irq is not set since the
      * normal Linux IRQ mechanism is not used in this case.
      */
 #ifdef HYPERVISOR_CALLBACK_VECTOR
     vmbus_interrupt = HYPERVISOR_CALLBACK_VECTOR;
     vmbus_irq = -1;
 #endif
 
     hv_debug_init();
 
     ret = vmbus_bus_init();
     if (ret)
         goto cleanup;
 
     hv_setup_kexec_handler(hv_kexec_handler);
     hv_setup_crash_handler(hv_crash_handler);
 
     register_syscore_ops(&hv_synic_syscore_ops);
 
     return 0;
 
 cleanup:
     acpi_bus_unregister_driver(&vmbus_acpi_driver);
     hv_acpi_dev = NULL;
     return ret;
 }
 
 static void __exit vmbus_exit(void)
 {
     int cpu;
 
     unregister_syscore_ops(&hv_synic_syscore_ops);
 
     hv_remove_kexec_handler();
     hv_remove_crash_handler();
     vmbus_connection.conn_state = DISCONNECTED;
     hv_stimer_global_cleanup();
     vmbus_disconnect();
     if (vmbus_irq == -1) {
         hv_remove_vmbus_handler();
     } else {
         free_percpu_irq(vmbus_irq, vmbus_evt);
         free_percpu(vmbus_evt);
     }
     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);
     }
     hv_debug_rm_all_dir();
 
     vmbus_free_channels();
     kfree(vmbus_connection.channels);
 
     if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
         kmsg_dump_unregister(&hv_kmsg_dumper);
         unregister_die_notifier(&hyperv_die_block);
     }
 
     /*
      * The panic notifier is always registered, hence we should
      * also unconditionally unregister it here as well.
      */
     atomic_notifier_chain_unregister(&panic_notifier_list,
                      &hyperv_panic_block);
 
     free_page((unsigned long)hv_panic_page);
     unregister_sysctl_table(hv_ctl_table_hdr);
     hv_ctl_table_hdr = NULL;
     bus_unregister(&hv_bus);
 
     cpuhp_remove_state(hyperv_cpuhp_online);
     hv_synic_free();
     acpi_bus_unregister_driver(&vmbus_acpi_driver);
 }
 
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Microsoft Hyper-V VMBus Driver");
 
 subsys_initcall(hv_acpi_init);
 module_exit(vmbus_exit);