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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2012, Microsoft Corporation.
  *
  * Author:
  *   K. Y. Srinivasan <kys@microsoft.com>
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/kernel.h>
 #include <linux/jiffies.h>
 #include <linux/mman.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/kthread.h>
 #include <linux/completion.h>
 #include <linux/count_zeros.h>
 #include <linux/memory_hotplug.h>
 #include <linux/memory.h>
 #include <linux/notifier.h>
 #include <linux/percpu_counter.h>
 #include <linux/page_reporting.h>
 
 #include <linux/hyperv.h>
 #include <asm/hyperv-tlfs.h>
 
 #include <asm/mshyperv.h>
 
 #define CREATE_TRACE_POINTS
 #include "hv_trace_balloon.h"
 
 /*
  * We begin with definitions supporting the Dynamic Memory protocol
  * with the host.
  *
  * Begin protocol definitions.
  */
 
 
 
 /*
  * Protocol versions. The low word is the minor version, the high word the major
  * version.
  *
  * History:
  * Initial version 1.0
  * Changed to 0.1 on 2009/03/25
  * Changes to 0.2 on 2009/05/14
  * Changes to 0.3 on 2009/12/03
  * Changed to 1.0 on 2011/04/05
  */
 
 #define DYNMEM_MAKE_VERSION(Major, Minor) ((__u32)(((Major) << 16) | (Minor)))
 #define DYNMEM_MAJOR_VERSION(Version) ((__u32)(Version) >> 16)
 #define DYNMEM_MINOR_VERSION(Version) ((__u32)(Version) & 0xff)
 
 enum {
     DYNMEM_PROTOCOL_VERSION_1 = DYNMEM_MAKE_VERSION(0, 3),
     DYNMEM_PROTOCOL_VERSION_2 = DYNMEM_MAKE_VERSION(1, 0),
     DYNMEM_PROTOCOL_VERSION_3 = DYNMEM_MAKE_VERSION(2, 0),
 
     DYNMEM_PROTOCOL_VERSION_WIN7 = DYNMEM_PROTOCOL_VERSION_1,
     DYNMEM_PROTOCOL_VERSION_WIN8 = DYNMEM_PROTOCOL_VERSION_2,
     DYNMEM_PROTOCOL_VERSION_WIN10 = DYNMEM_PROTOCOL_VERSION_3,
 
     DYNMEM_PROTOCOL_VERSION_CURRENT = DYNMEM_PROTOCOL_VERSION_WIN10
 };
 
 
 
 /*
  * Message Types
  */
 
 enum dm_message_type {
     /*
      * Version 0.3
      */
     DM_ERROR            = 0,
     DM_VERSION_REQUEST      = 1,
     DM_VERSION_RESPONSE     = 2,
     DM_CAPABILITIES_REPORT      = 3,
     DM_CAPABILITIES_RESPONSE    = 4,
     DM_STATUS_REPORT        = 5,
     DM_BALLOON_REQUEST      = 6,
     DM_BALLOON_RESPONSE     = 7,
     DM_UNBALLOON_REQUEST        = 8,
     DM_UNBALLOON_RESPONSE       = 9,
     DM_MEM_HOT_ADD_REQUEST      = 10,
     DM_MEM_HOT_ADD_RESPONSE     = 11,
     DM_VERSION_03_MAX       = 11,
     /*
      * Version 1.0.
      */
     DM_INFO_MESSAGE         = 12,
     DM_VERSION_1_MAX        = 12
 };
 
 
 /*
  * Structures defining the dynamic memory management
  * protocol.
  */
 
 union dm_version {
     struct {
         __u16 minor_version;
         __u16 major_version;
     };
     __u32 version;
 } __packed;
 
 
 union dm_caps {
     struct {
         __u64 balloon:1;
         __u64 hot_add:1;
         /*
          * To support guests that may have alignment
          * limitations on hot-add, the guest can specify
          * its alignment requirements; a value of n
          * represents an alignment of 2^n in mega bytes.
          */
         __u64 hot_add_alignment:4;
         __u64 reservedz:58;
     } cap_bits;
     __u64 caps;
 } __packed;
 
 union dm_mem_page_range {
     struct  {
         /*
          * The PFN number of the first page in the range.
          * 40 bits is the architectural limit of a PFN
          * number for AMD64.
          */
         __u64 start_page:40;
         /*
          * The number of pages in the range.
          */
         __u64 page_cnt:24;
     } finfo;
     __u64  page_range;
 } __packed;
 
 
 
 /*
  * The header for all dynamic memory messages:
  *
  * type: Type of the message.
  * size: Size of the message in bytes; including the header.
  * trans_id: The guest is responsible for manufacturing this ID.
  */
 
 struct dm_header {
     __u16 type;
     __u16 size;
     __u32 trans_id;
 } __packed;
 
 /*
  * A generic message format for dynamic memory.
  * Specific message formats are defined later in the file.
  */
 
 struct dm_message {
     struct dm_header hdr;
     __u8 data[]; /* enclosed message */
 } __packed;
 
 
 /*
  * Specific message types supporting the dynamic memory protocol.
  */
 
 /*
  * Version negotiation message. Sent from the guest to the host.
  * The guest is free to try different versions until the host
  * accepts the version.
  *
  * dm_version: The protocol version requested.
  * is_last_attempt: If TRUE, this is the last version guest will request.
  * reservedz: Reserved field, set to zero.
  */
 
 struct dm_version_request {
     struct dm_header hdr;
     union dm_version version;
     __u32 is_last_attempt:1;
     __u32 reservedz:31;
 } __packed;
 
 /*
  * Version response message; Host to Guest and indicates
  * if the host has accepted the version sent by the guest.
  *
  * is_accepted: If TRUE, host has accepted the version and the guest
  * should proceed to the next stage of the protocol. FALSE indicates that
  * guest should re-try with a different version.
  *
  * reservedz: Reserved field, set to zero.
  */
 
 struct dm_version_response {
     struct dm_header hdr;
     __u64 is_accepted:1;
     __u64 reservedz:63;
 } __packed;
 
 /*
  * Message reporting capabilities. This is sent from the guest to the
  * host.
  */
 
 struct dm_capabilities {
     struct dm_header hdr;
     union dm_caps caps;
     __u64 min_page_cnt;
     __u64 max_page_number;
 } __packed;
 
 /*
  * Response to the capabilities message. This is sent from the host to the
  * guest. This message notifies if the host has accepted the guest's
  * capabilities. If the host has not accepted, the guest must shutdown
  * the service.
  *
  * is_accepted: Indicates if the host has accepted guest's capabilities.
  * reservedz: Must be 0.
  */
 
 struct dm_capabilities_resp_msg {
     struct dm_header hdr;
     __u64 is_accepted:1;
     __u64 reservedz:63;
 } __packed;
 
 /*
  * This message is used to report memory pressure from the guest.
  * This message is not part of any transaction and there is no
  * response to this message.
  *
  * num_avail: Available memory in pages.
  * num_committed: Committed memory in pages.
  * page_file_size: The accumulated size of all page files
  *         in the system in pages.
  * zero_free: The number of zero and free pages.
  * page_file_writes: The writes to the page file in pages.
  * io_diff: An indicator of file cache efficiency or page file activity,
  *      calculated as File Cache Page Fault Count - Page Read Count.
  *      This value is in pages.
  *
  * Some of these metrics are Windows specific and fortunately
  * the algorithm on the host side that computes the guest memory
  * pressure only uses num_committed value.
  */
 
 struct dm_status {
     struct dm_header hdr;
     __u64 num_avail;
     __u64 num_committed;
     __u64 page_file_size;
     __u64 zero_free;
     __u32 page_file_writes;
     __u32 io_diff;
 } __packed;
 
 
 /*
  * Message to ask the guest to allocate memory - balloon up message.
  * This message is sent from the host to the guest. The guest may not be
  * able to allocate as much memory as requested.
  *
  * num_pages: number of pages to allocate.
  */
 
 struct dm_balloon {
     struct dm_header hdr;
     __u32 num_pages;
     __u32 reservedz;
 } __packed;
 
 
 /*
  * Balloon response message; this message is sent from the guest
  * to the host in response to the balloon message.
  *
  * reservedz: Reserved; must be set to zero.
  * more_pages: If FALSE, this is the last message of the transaction.
  * if TRUE there will atleast one more message from the guest.
  *
  * range_count: The number of ranges in the range array.
  *
  * range_array: An array of page ranges returned to the host.
  *
  */
 
 struct dm_balloon_response {
     struct dm_header hdr;
     __u32 reservedz;
     __u32 more_pages:1;
     __u32 range_count:31;
     union dm_mem_page_range range_array[];
 } __packed;
 
 /*
  * Un-balloon message; this message is sent from the host
  * to the guest to give guest more memory.
  *
  * more_pages: If FALSE, this is the last message of the transaction.
  * if TRUE there will atleast one more message from the guest.
  *
  * reservedz: Reserved; must be set to zero.
  *
  * range_count: The number of ranges in the range array.
  *
  * range_array: An array of page ranges returned to the host.
  *
  */
 
 struct dm_unballoon_request {
     struct dm_header hdr;
     __u32 more_pages:1;
     __u32 reservedz:31;
     __u32 range_count;
     union dm_mem_page_range range_array[];
 } __packed;
 
 /*
  * Un-balloon response message; this message is sent from the guest
  * to the host in response to an unballoon request.
  *
  */
 
 struct dm_unballoon_response {
     struct dm_header hdr;
 } __packed;
 
 
 /*
  * Hot add request message. Message sent from the host to the guest.
  *
  * mem_range: Memory range to hot add.
  *
  */
 
 struct dm_hot_add {
     struct dm_header hdr;
     union dm_mem_page_range range;
 } __packed;
 
 /*
  * Hot add response message.
  * This message is sent by the guest to report the status of a hot add request.
  * If page_count is less than the requested page count, then the host should
  * assume all further hot add requests will fail, since this indicates that
  * the guest has hit an upper physical memory barrier.
  *
  * Hot adds may also fail due to low resources; in this case, the guest must
  * not complete this message until the hot add can succeed, and the host must
  * not send a new hot add request until the response is sent.
  * If VSC fails to hot add memory DYNMEM_NUMBER_OF_UNSUCCESSFUL_HOTADD_ATTEMPTS
  * times it fails the request.
  *
  *
  * page_count: number of pages that were successfully hot added.
  *
  * result: result of the operation 1: success, 0: failure.
  *
  */
 
 struct dm_hot_add_response {
     struct dm_header hdr;
     __u32 page_count;
     __u32 result;
 } __packed;
 
 /*
  * Types of information sent from host to the guest.
  */
 
 enum dm_info_type {
     INFO_TYPE_MAX_PAGE_CNT = 0,
     MAX_INFO_TYPE
 };
 
 
 /*
  * Header for the information message.
  */
 
 struct dm_info_header {
     enum dm_info_type type;
     __u32 data_size;
 } __packed;
 
 /*
  * This message is sent from the host to the guest to pass
  * some relevant information (win8 addition).
  *
  * reserved: no used.
  * info_size: size of the information blob.
  * info: information blob.
  */
 
 struct dm_info_msg {
     struct dm_header hdr;
     __u32 reserved;
     __u32 info_size;
     __u8  info[];
 };
 
 /*
  * End protocol definitions.
  */
 
 /*
  * State to manage hot adding memory into the guest.
  * The range start_pfn : end_pfn specifies the range
  * that the host has asked us to hot add. The range
  * start_pfn : ha_end_pfn specifies the range that we have
  * currently hot added. We hot add in multiples of 128M
  * chunks; it is possible that we may not be able to bring
  * online all the pages in the region. The range
  * covered_start_pfn:covered_end_pfn defines the pages that can
  * be brough online.
  */
 
 struct hv_hotadd_state {
     struct list_head list;
     unsigned long start_pfn;
     unsigned long covered_start_pfn;
     unsigned long covered_end_pfn;
     unsigned long ha_end_pfn;
     unsigned long end_pfn;
     /*
      * A list of gaps.
      */
     struct list_head gap_list;
 };
 
 struct hv_hotadd_gap {
     struct list_head list;
     unsigned long start_pfn;
     unsigned long end_pfn;
 };
 
 struct balloon_state {
     __u32 num_pages;
     struct work_struct wrk;
 };
 
 struct hot_add_wrk {
     union dm_mem_page_range ha_page_range;
     union dm_mem_page_range ha_region_range;
     struct work_struct wrk;
 };
 
 static bool allow_hibernation;
 static bool hot_add = true;
 static bool do_hot_add;
 /*
  * Delay reporting memory pressure by
  * the specified number of seconds.
  */
 static uint pressure_report_delay = 45;
 
 /*
  * The last time we posted a pressure report to host.
  */
 static unsigned long last_post_time;
 
 module_param(hot_add, bool, (S_IRUGO | S_IWUSR));
 MODULE_PARM_DESC(hot_add, "If set attempt memory hot_add");
 
 module_param(pressure_report_delay, uint, (S_IRUGO | S_IWUSR));
 MODULE_PARM_DESC(pressure_report_delay, "Delay in secs in reporting pressure");
 static atomic_t trans_id = ATOMIC_INIT(0);
 
 static int dm_ring_size = VMBUS_RING_SIZE(16 * 1024);
 
 /*
  * Driver specific state.
  */
 
 enum hv_dm_state {
     DM_INITIALIZING = 0,
     DM_INITIALIZED,
     DM_BALLOON_UP,
     DM_BALLOON_DOWN,
     DM_HOT_ADD,
     DM_INIT_ERROR
 };
 
 
 static __u8 recv_buffer[HV_HYP_PAGE_SIZE];
 static __u8 balloon_up_send_buffer[HV_HYP_PAGE_SIZE];
 #define PAGES_IN_2M (2 * 1024 * 1024 / PAGE_SIZE)
 #define HA_CHUNK (128 * 1024 * 1024 / PAGE_SIZE)
 
 struct hv_dynmem_device {
     struct hv_device *dev;
     enum hv_dm_state state;
     struct completion host_event;
     struct completion config_event;
 
     /*
      * Number of pages we have currently ballooned out.
      */
     unsigned int num_pages_ballooned;
     unsigned int num_pages_onlined;
     unsigned int num_pages_added;
 
     /*
      * State to manage the ballooning (up) operation.
      */
     struct balloon_state balloon_wrk;
 
     /*
      * State to execute the "hot-add" operation.
      */
     struct hot_add_wrk ha_wrk;
 
     /*
      * This state tracks if the host has specified a hot-add
      * region.
      */
     bool host_specified_ha_region;
 
     /*
      * State to synchronize hot-add.
      */
     struct completion  ol_waitevent;
     /*
      * This thread handles hot-add
      * requests from the host as well as notifying
      * the host with regards to memory pressure in
      * the guest.
      */
     struct task_struct *thread;
 
     /*
      * Protects ha_region_list, num_pages_onlined counter and individual
      * regions from ha_region_list.
      */
     spinlock_t ha_lock;
 
     /*
      * A list of hot-add regions.
      */
     struct list_head ha_region_list;
 
     /*
      * We start with the highest version we can support
      * and downgrade based on the host; we save here the
      * next version to try.
      */
     __u32 next_version;
 
     /*
      * The negotiated version agreed by host.
      */
     __u32 version;
 
     struct page_reporting_dev_info pr_dev_info;
 
     /*
      * Maximum number of pages that can be hot_add-ed
      */
     __u64 max_dynamic_page_count;
 };
 
 static struct hv_dynmem_device dm_device;
 
 static void post_status(struct hv_dynmem_device *dm);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 static inline bool has_pfn_is_backed(struct hv_hotadd_state *has,
                      unsigned long pfn)
 {
     struct hv_hotadd_gap *gap;
 
     /* The page is not backed. */
     if ((pfn < has->covered_start_pfn) || (pfn >= has->covered_end_pfn))
         return false;
 
     /* Check for gaps. */
     list_for_each_entry(gap, &has->gap_list, list) {
         if ((pfn >= gap->start_pfn) && (pfn < gap->end_pfn))
             return false;
     }
 
     return true;
 }
 
 static unsigned long hv_page_offline_check(unsigned long start_pfn,
                        unsigned long nr_pages)
 {
     unsigned long pfn = start_pfn, count = 0;
     struct hv_hotadd_state *has;
     bool found;
 
     while (pfn < start_pfn + nr_pages) {
         /*
          * Search for HAS which covers the pfn and when we find one
          * count how many consequitive PFNs are covered.
          */
         found = false;
         list_for_each_entry(has, &dm_device.ha_region_list, list) {
             while ((pfn >= has->start_pfn) &&
                    (pfn < has->end_pfn) &&
                    (pfn < start_pfn + nr_pages)) {
                 found = true;
                 if (has_pfn_is_backed(has, pfn))
                     count++;
                 pfn++;
             }
         }
 
         /*
          * This PFN is not in any HAS (e.g. we're offlining a region
          * which was present at boot), no need to account for it. Go
          * to the next one.
          */
         if (!found)
             pfn++;
     }
 
     return count;
 }
 
 static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
                   void *v)
 {
     struct memory_notify *mem = (struct memory_notify *)v;
     unsigned long flags, pfn_count;
 
     switch (val) {
     case MEM_ONLINE:
     case MEM_CANCEL_ONLINE:
         complete(&dm_device.ol_waitevent);
         break;
 
     case MEM_OFFLINE:
         spin_lock_irqsave(&dm_device.ha_lock, flags);
         pfn_count = hv_page_offline_check(mem->start_pfn,
                           mem->nr_pages);
         if (pfn_count <= dm_device.num_pages_onlined) {
             dm_device.num_pages_onlined -= pfn_count;
         } else {
             /*
              * We're offlining more pages than we managed to online.
              * This is unexpected. In any case don't let
              * num_pages_onlined wrap around zero.
              */
             WARN_ON_ONCE(1);
             dm_device.num_pages_onlined = 0;
         }
         spin_unlock_irqrestore(&dm_device.ha_lock, flags);
         break;
     case MEM_GOING_ONLINE:
     case MEM_GOING_OFFLINE:
     case MEM_CANCEL_OFFLINE:
         break;
     }
     return NOTIFY_OK;
 }
 
 static struct notifier_block hv_memory_nb = {
     .notifier_call = hv_memory_notifier,
     .priority = 0
 };
 
 /* Check if the particular page is backed and can be onlined and online it. */
 static void hv_page_online_one(struct hv_hotadd_state *has, struct page *pg)
 {
     if (!has_pfn_is_backed(has, page_to_pfn(pg))) {
         if (!PageOffline(pg))
             __SetPageOffline(pg);
         return;
     }
     if (PageOffline(pg))
         __ClearPageOffline(pg);
 
     /* This frame is currently backed; online the page. */
     generic_online_page(pg, 0);
 
     lockdep_assert_held(&dm_device.ha_lock);
     dm_device.num_pages_onlined++;
 }
 
 static void hv_bring_pgs_online(struct hv_hotadd_state *has,
                 unsigned long start_pfn, unsigned long size)
 {
     int i;
 
     pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
     for (i = 0; i < size; i++)
         hv_page_online_one(has, pfn_to_page(start_pfn + i));
 }
 
 static void hv_mem_hot_add(unsigned long start, unsigned long size,
                 unsigned long pfn_count,
                 struct hv_hotadd_state *has)
 {
     int ret = 0;
     int i, nid;
     unsigned long start_pfn;
     unsigned long processed_pfn;
     unsigned long total_pfn = pfn_count;
     unsigned long flags;
 
     for (i = 0; i < (size/HA_CHUNK); i++) {
         start_pfn = start + (i * HA_CHUNK);
 
         spin_lock_irqsave(&dm_device.ha_lock, flags);
         has->ha_end_pfn +=  HA_CHUNK;
 
         if (total_pfn > HA_CHUNK) {
             processed_pfn = HA_CHUNK;
             total_pfn -= HA_CHUNK;
         } else {
             processed_pfn = total_pfn;
             total_pfn = 0;
         }
 
         has->covered_end_pfn +=  processed_pfn;
         spin_unlock_irqrestore(&dm_device.ha_lock, flags);
 
         reinit_completion(&dm_device.ol_waitevent);
 
         nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
         ret = add_memory(nid, PFN_PHYS((start_pfn)),
                 (HA_CHUNK << PAGE_SHIFT), MHP_MERGE_RESOURCE);
 
         if (ret) {
             pr_err("hot_add memory failed error is %d\n", ret);
             if (ret == -EEXIST) {
                 /*
                  * This error indicates that the error
                  * is not a transient failure. This is the
                  * case where the guest's physical address map
                  * precludes hot adding memory. Stop all further
                  * memory hot-add.
                  */
                 do_hot_add = false;
             }
             spin_lock_irqsave(&dm_device.ha_lock, flags);
             has->ha_end_pfn -= HA_CHUNK;
             has->covered_end_pfn -=  processed_pfn;
             spin_unlock_irqrestore(&dm_device.ha_lock, flags);
             break;
         }
 
         /*
          * Wait for memory to get onlined. If the kernel onlined the
          * memory when adding it, this will return directly. Otherwise,
          * it will wait for user space to online the memory. This helps
          * to avoid adding memory faster than it is getting onlined. As
          * adding succeeded, it is ok to proceed even if the memory was
          * not onlined in time.
          */
         wait_for_completion_timeout(&dm_device.ol_waitevent, 5 * HZ);
         post_status(&dm_device);
     }
 }
 
 static void hv_online_page(struct page *pg, unsigned int order)
 {
     struct hv_hotadd_state *has;
     unsigned long flags;
     unsigned long pfn = page_to_pfn(pg);
 
     spin_lock_irqsave(&dm_device.ha_lock, flags);
     list_for_each_entry(has, &dm_device.ha_region_list, list) {
         /* The page belongs to a different HAS. */
         if ((pfn < has->start_pfn) ||
                 (pfn + (1UL << order) > has->end_pfn))
             continue;
 
         hv_bring_pgs_online(has, pfn, 1UL << order);
         break;
     }
     spin_unlock_irqrestore(&dm_device.ha_lock, flags);
 }
 
 static int pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
 {
     struct hv_hotadd_state *has;
     struct hv_hotadd_gap *gap;
     unsigned long residual, new_inc;
     int ret = 0;
     unsigned long flags;
 
     spin_lock_irqsave(&dm_device.ha_lock, flags);
     list_for_each_entry(has, &dm_device.ha_region_list, list) {
         /*
          * If the pfn range we are dealing with is not in the current
          * "hot add block", move on.
          */
         if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
             continue;
 
         /*
          * If the current start pfn is not where the covered_end
          * is, create a gap and update covered_end_pfn.
          */
         if (has->covered_end_pfn != start_pfn) {
             gap = kzalloc(sizeof(struct hv_hotadd_gap), GFP_ATOMIC);
             if (!gap) {
                 ret = -ENOMEM;
                 break;
             }
 
             INIT_LIST_HEAD(&gap->list);
             gap->start_pfn = has->covered_end_pfn;
             gap->end_pfn = start_pfn;
             list_add_tail(&gap->list, &has->gap_list);
 
             has->covered_end_pfn = start_pfn;
         }
 
         /*
          * If the current hot add-request extends beyond
          * our current limit; extend it.
          */
         if ((start_pfn + pfn_cnt) > has->end_pfn) {
             residual = (start_pfn + pfn_cnt - has->end_pfn);
             /*
              * Extend the region by multiples of HA_CHUNK.
              */
             new_inc = (residual / HA_CHUNK) * HA_CHUNK;
             if (residual % HA_CHUNK)
                 new_inc += HA_CHUNK;
 
             has->end_pfn += new_inc;
         }
 
         ret = 1;
         break;
     }
     spin_unlock_irqrestore(&dm_device.ha_lock, flags);
 
     return ret;
 }
 
 static unsigned long handle_pg_range(unsigned long pg_start,
                     unsigned long pg_count)
 {
     unsigned long start_pfn = pg_start;
     unsigned long pfn_cnt = pg_count;
     unsigned long size;
     struct hv_hotadd_state *has;
     unsigned long pgs_ol = 0;
     unsigned long old_covered_state;
     unsigned long res = 0, flags;
 
     pr_debug("Hot adding %lu pages starting at pfn 0x%lx.\n", pg_count,
         pg_start);
 
     spin_lock_irqsave(&dm_device.ha_lock, flags);
     list_for_each_entry(has, &dm_device.ha_region_list, list) {
         /*
          * If the pfn range we are dealing with is not in the current
          * "hot add block", move on.
          */
         if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
             continue;
 
         old_covered_state = has->covered_end_pfn;
 
         if (start_pfn < has->ha_end_pfn) {
             /*
              * This is the case where we are backing pages
              * in an already hot added region. Bring
              * these pages online first.
              */
             pgs_ol = has->ha_end_pfn - start_pfn;
             if (pgs_ol > pfn_cnt)
                 pgs_ol = pfn_cnt;
 
             has->covered_end_pfn +=  pgs_ol;
             pfn_cnt -= pgs_ol;
             /*
              * Check if the corresponding memory block is already
              * online. It is possible to observe struct pages still
              * being uninitialized here so check section instead.
              * In case the section is online we need to bring the
              * rest of pfns (which were not backed previously)
              * online too.
              */
             if (start_pfn > has->start_pfn &&
                 online_section_nr(pfn_to_section_nr(start_pfn)))
                 hv_bring_pgs_online(has, start_pfn, pgs_ol);
 
         }
 
         if ((has->ha_end_pfn < has->end_pfn) && (pfn_cnt > 0)) {
             /*
              * We have some residual hot add range
              * that needs to be hot added; hot add
              * it now. Hot add a multiple of
              * of HA_CHUNK that fully covers the pages
              * we have.
              */
             size = (has->end_pfn - has->ha_end_pfn);
             if (pfn_cnt <= size) {
                 size = ((pfn_cnt / HA_CHUNK) * HA_CHUNK);
                 if (pfn_cnt % HA_CHUNK)
                     size += HA_CHUNK;
             } else {
                 pfn_cnt = size;
             }
             spin_unlock_irqrestore(&dm_device.ha_lock, flags);
             hv_mem_hot_add(has->ha_end_pfn, size, pfn_cnt, has);
             spin_lock_irqsave(&dm_device.ha_lock, flags);
         }
         /*
          * If we managed to online any pages that were given to us,
          * we declare success.
          */
         res = has->covered_end_pfn - old_covered_state;
         break;
     }
     spin_unlock_irqrestore(&dm_device.ha_lock, flags);
 
     return res;
 }
 
 static unsigned long process_hot_add(unsigned long pg_start,
                     unsigned long pfn_cnt,
                     unsigned long rg_start,
                     unsigned long rg_size)
 {
     struct hv_hotadd_state *ha_region = NULL;
     int covered;
     unsigned long flags;
 
     if (pfn_cnt == 0)
         return 0;
 
     if (!dm_device.host_specified_ha_region) {
         covered = pfn_covered(pg_start, pfn_cnt);
         if (covered < 0)
             return 0;
 
         if (covered)
             goto do_pg_range;
     }
 
     /*
      * If the host has specified a hot-add range; deal with it first.
      */
 
     if (rg_size != 0) {
         ha_region = kzalloc(sizeof(struct hv_hotadd_state), GFP_KERNEL);
         if (!ha_region)
             return 0;
 
         INIT_LIST_HEAD(&ha_region->list);
         INIT_LIST_HEAD(&ha_region->gap_list);
 
         ha_region->start_pfn = rg_start;
         ha_region->ha_end_pfn = rg_start;
         ha_region->covered_start_pfn = pg_start;
         ha_region->covered_end_pfn = pg_start;
         ha_region->end_pfn = rg_start + rg_size;
 
         spin_lock_irqsave(&dm_device.ha_lock, flags);
         list_add_tail(&ha_region->list, &dm_device.ha_region_list);
         spin_unlock_irqrestore(&dm_device.ha_lock, flags);
     }
 
 do_pg_range:
     /*
      * Process the page range specified; bringing them
      * online if possible.
      */
     return handle_pg_range(pg_start, pfn_cnt);
 }
 
 #endif
 
 static void hot_add_req(struct work_struct *dummy)
 {
     struct dm_hot_add_response resp;
 #ifdef CONFIG_MEMORY_HOTPLUG
     unsigned long pg_start, pfn_cnt;
     unsigned long rg_start, rg_sz;
 #endif
     struct hv_dynmem_device *dm = &dm_device;
 
     memset(&resp, 0, sizeof(struct dm_hot_add_response));
     resp.hdr.type = DM_MEM_HOT_ADD_RESPONSE;
     resp.hdr.size = sizeof(struct dm_hot_add_response);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
     pg_start = dm->ha_wrk.ha_page_range.finfo.start_page;
     pfn_cnt = dm->ha_wrk.ha_page_range.finfo.page_cnt;
 
     rg_start = dm->ha_wrk.ha_region_range.finfo.start_page;
     rg_sz = dm->ha_wrk.ha_region_range.finfo.page_cnt;
 
     if ((rg_start == 0) && (!dm->host_specified_ha_region)) {
         unsigned long region_size;
         unsigned long region_start;
 
         /*
          * The host has not specified the hot-add region.
          * Based on the hot-add page range being specified,
          * compute a hot-add region that can cover the pages
          * that need to be hot-added while ensuring the alignment
          * and size requirements of Linux as it relates to hot-add.
          */
         region_size = (pfn_cnt / HA_CHUNK) * HA_CHUNK;
         if (pfn_cnt % HA_CHUNK)
             region_size += HA_CHUNK;
 
         region_start = (pg_start / HA_CHUNK) * HA_CHUNK;
 
         rg_start = region_start;
         rg_sz = region_size;
     }
 
     if (do_hot_add)
         resp.page_count = process_hot_add(pg_start, pfn_cnt,
                         rg_start, rg_sz);
 
     dm->num_pages_added += resp.page_count;
 #endif
     /*
      * The result field of the response structure has the
      * following semantics:
      *
      * 1. If all or some pages hot-added: Guest should return success.
      *
      * 2. If no pages could be hot-added:
      *
      * If the guest returns success, then the host
      * will not attempt any further hot-add operations. This
      * signifies a permanent failure.
      *
      * If the guest returns failure, then this failure will be
      * treated as a transient failure and the host may retry the
      * hot-add operation after some delay.
      */
     if (resp.page_count > 0)
         resp.result = 1;
     else if (!do_hot_add)
         resp.result = 1;
     else
         resp.result = 0;
 
     if (!do_hot_add || resp.page_count == 0) {
         if (!allow_hibernation)
             pr_err("Memory hot add failed\n");
         else
             pr_info("Ignore hot-add request!\n");
     }
 
     dm->state = DM_INITIALIZED;
     resp.hdr.trans_id = atomic_inc_return(&trans_id);
     vmbus_sendpacket(dm->dev->channel, &resp,
             sizeof(struct dm_hot_add_response),
             (unsigned long)NULL,
             VM_PKT_DATA_INBAND, 0);
 }
 
 static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
 {
     struct dm_info_header *info_hdr;
 
     info_hdr = (struct dm_info_header *)msg->info;
 
     switch (info_hdr->type) {
     case INFO_TYPE_MAX_PAGE_CNT:
         if (info_hdr->data_size == sizeof(__u64)) {
             __u64 *max_page_count = (__u64 *)&info_hdr[1];
 
             pr_info("Max. dynamic memory size: %llu MB\n",
                 (*max_page_count) >> (20 - HV_HYP_PAGE_SHIFT));
             dm->max_dynamic_page_count = *max_page_count;
         }
 
         break;
     default:
         pr_warn("Received Unknown type: %d\n", info_hdr->type);
     }
 }
 
 static unsigned long compute_balloon_floor(void)
 {
     unsigned long min_pages;
     unsigned long nr_pages = totalram_pages();
 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
     /* Simple continuous piecewiese linear function:
      *  max MiB -> min MiB  gradient
      *       0         0
      *      16        16
      *      32        24
      *     128        72    (1/2)
      *     512       168    (1/4)
      *    2048       360    (1/8)
      *    8192       744    (1/16)
      *   32768      1512    (1/32)
      */
     if (nr_pages < MB2PAGES(128))
         min_pages = MB2PAGES(8) + (nr_pages >> 1);
     else if (nr_pages < MB2PAGES(512))
         min_pages = MB2PAGES(40) + (nr_pages >> 2);
     else if (nr_pages < MB2PAGES(2048))
         min_pages = MB2PAGES(104) + (nr_pages >> 3);
     else if (nr_pages < MB2PAGES(8192))
         min_pages = MB2PAGES(232) + (nr_pages >> 4);
     else
         min_pages = MB2PAGES(488) + (nr_pages >> 5);
 #undef MB2PAGES
     return min_pages;
 }
 
 /*
  * Compute total committed memory pages
  */
 
 static unsigned long get_pages_committed(struct hv_dynmem_device *dm)
 {
     return vm_memory_committed() +
         dm->num_pages_ballooned +
         (dm->num_pages_added > dm->num_pages_onlined ?
          dm->num_pages_added - dm->num_pages_onlined : 0) +
         compute_balloon_floor();
 }
 
 /*
  * Post our status as it relates memory pressure to the
  * host. Host expects the guests to post this status
  * periodically at 1 second intervals.
  *
  * The metrics specified in this protocol are very Windows
  * specific and so we cook up numbers here to convey our memory
  * pressure.
  */
 
 static void post_status(struct hv_dynmem_device *dm)
 {
     struct dm_status status;
     unsigned long now = jiffies;
     unsigned long last_post = last_post_time;
     unsigned long num_pages_avail, num_pages_committed;
 
     if (pressure_report_delay > 0) {
         --pressure_report_delay;
         return;
     }
 
     if (!time_after(now, (last_post_time + HZ)))
         return;
 
     memset(&status, 0, sizeof(struct dm_status));
     status.hdr.type = DM_STATUS_REPORT;
     status.hdr.size = sizeof(struct dm_status);
     status.hdr.trans_id = atomic_inc_return(&trans_id);
 
     /*
      * The host expects the guest to report free and committed memory.
      * Furthermore, the host expects the pressure information to include
      * the ballooned out pages. For a given amount of memory that we are
      * managing we need to compute a floor below which we should not
      * balloon. Compute this and add it to the pressure report.
      * We also need to report all offline pages (num_pages_added -
      * num_pages_onlined) as committed to the host, otherwise it can try
      * asking us to balloon them out.
      */
     num_pages_avail = si_mem_available();
     num_pages_committed = get_pages_committed(dm);
 
     trace_balloon_status(num_pages_avail, num_pages_committed,
                  vm_memory_committed(), dm->num_pages_ballooned,
                  dm->num_pages_added, dm->num_pages_onlined);
 
     /* Convert numbers of pages into numbers of HV_HYP_PAGEs. */
     status.num_avail = num_pages_avail * NR_HV_HYP_PAGES_IN_PAGE;
     status.num_committed = num_pages_committed * NR_HV_HYP_PAGES_IN_PAGE;
 
     /*
      * If our transaction ID is no longer current, just don't
      * send the status. This can happen if we were interrupted
      * after we picked our transaction ID.
      */
     if (status.hdr.trans_id != atomic_read(&trans_id))
         return;
 
     /*
      * If the last post time that we sampled has changed,
      * we have raced, don't post the status.
      */
     if (last_post != last_post_time)
         return;
 
     last_post_time = jiffies;
     vmbus_sendpacket(dm->dev->channel, &status,
                 sizeof(struct dm_status),
                 (unsigned long)NULL,
                 VM_PKT_DATA_INBAND, 0);
 
 }
 
 static void free_balloon_pages(struct hv_dynmem_device *dm,
              union dm_mem_page_range *range_array)
 {
     int num_pages = range_array->finfo.page_cnt;
     __u64 start_frame = range_array->finfo.start_page;
     struct page *pg;
     int i;
 
     for (i = 0; i < num_pages; i++) {
         pg = pfn_to_page(i + start_frame);
         __ClearPageOffline(pg);
         __free_page(pg);
         dm->num_pages_ballooned--;
         adjust_managed_page_count(pg, 1);
     }
 }
 
 
 
 static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
                     unsigned int num_pages,
                     struct dm_balloon_response *bl_resp,
                     int alloc_unit)
 {
     unsigned int i, j;
     struct page *pg;
 
     for (i = 0; i < num_pages / alloc_unit; i++) {
         if (bl_resp->hdr.size + sizeof(union dm_mem_page_range) >
             HV_HYP_PAGE_SIZE)
             return i * alloc_unit;
 
         /*
          * We execute this code in a thread context. Furthermore,
          * we don't want the kernel to try too hard.
          */
         pg = alloc_pages(GFP_HIGHUSER | __GFP_NORETRY |
                 __GFP_NOMEMALLOC | __GFP_NOWARN,
                 get_order(alloc_unit << PAGE_SHIFT));
 
         if (!pg)
             return i * alloc_unit;
 
         dm->num_pages_ballooned += alloc_unit;
 
         /*
          * If we allocatted 2M pages; split them so we
          * can free them in any order we get.
          */
 
         if (alloc_unit != 1)
             split_page(pg, get_order(alloc_unit << PAGE_SHIFT));
 
         /* mark all pages offline */
         for (j = 0; j < alloc_unit; j++) {
             __SetPageOffline(pg + j);
             adjust_managed_page_count(pg + j, -1);
         }
 
         bl_resp->range_count++;
         bl_resp->range_array[i].finfo.start_page =
             page_to_pfn(pg);
         bl_resp->range_array[i].finfo.page_cnt = alloc_unit;
         bl_resp->hdr.size += sizeof(union dm_mem_page_range);
 
     }
 
     return i * alloc_unit;
 }
 
 static void balloon_up(struct work_struct *dummy)
 {
     unsigned int num_pages = dm_device.balloon_wrk.num_pages;
     unsigned int num_ballooned = 0;
     struct dm_balloon_response *bl_resp;
     int alloc_unit;
     int ret;
     bool done = false;
     int i;
     long avail_pages;
     unsigned long floor;
 
     /*
      * We will attempt 2M allocations. However, if we fail to
      * allocate 2M chunks, we will go back to PAGE_SIZE allocations.
      */
     alloc_unit = PAGES_IN_2M;
 
     avail_pages = si_mem_available();
     floor = compute_balloon_floor();
 
     /* Refuse to balloon below the floor. */
     if (avail_pages < num_pages || avail_pages - num_pages < floor) {
         pr_info("Balloon request will be partially fulfilled. %s\n",
             avail_pages < num_pages ? "Not enough memory." :
             "Balloon floor reached.");
 
         num_pages = avail_pages > floor ? (avail_pages - floor) : 0;
     }
 
     while (!done) {
         memset(balloon_up_send_buffer, 0, HV_HYP_PAGE_SIZE);
         bl_resp = (struct dm_balloon_response *)balloon_up_send_buffer;
         bl_resp->hdr.type = DM_BALLOON_RESPONSE;
         bl_resp->hdr.size = sizeof(struct dm_balloon_response);
         bl_resp->more_pages = 1;
 
         num_pages -= num_ballooned;
         num_ballooned = alloc_balloon_pages(&dm_device, num_pages,
                             bl_resp, alloc_unit);
 
         if (alloc_unit != 1 && num_ballooned == 0) {
             alloc_unit = 1;
             continue;
         }
 
         if (num_ballooned == 0 || num_ballooned == num_pages) {
             pr_debug("Ballooned %u out of %u requested pages.\n",
                 num_pages, dm_device.balloon_wrk.num_pages);
 
             bl_resp->more_pages = 0;
             done = true;
             dm_device.state = DM_INITIALIZED;
         }
 
         /*
          * We are pushing a lot of data through the channel;
          * deal with transient failures caused because of the
          * lack of space in the ring buffer.
          */
 
         do {
             bl_resp->hdr.trans_id = atomic_inc_return(&trans_id);
             ret = vmbus_sendpacket(dm_device.dev->channel,
                         bl_resp,
                         bl_resp->hdr.size,
                         (unsigned long)NULL,
                         VM_PKT_DATA_INBAND, 0);
 
             if (ret == -EAGAIN)
                 msleep(20);
             post_status(&dm_device);
         } while (ret == -EAGAIN);
 
         if (ret) {
             /*
              * Free up the memory we allocatted.
              */
             pr_err("Balloon response failed\n");
 
             for (i = 0; i < bl_resp->range_count; i++)
                 free_balloon_pages(&dm_device,
                          &bl_resp->range_array[i]);
 
             done = true;
         }
     }
 
 }
 
 static void balloon_down(struct hv_dynmem_device *dm,
             struct dm_unballoon_request *req)
 {
     union dm_mem_page_range *range_array = req->range_array;
     int range_count = req->range_count;
     struct dm_unballoon_response resp;
     int i;
     unsigned int prev_pages_ballooned = dm->num_pages_ballooned;
 
     for (i = 0; i < range_count; i++) {
         free_balloon_pages(dm, &range_array[i]);
         complete(&dm_device.config_event);
     }
 
     pr_debug("Freed %u ballooned pages.\n",
         prev_pages_ballooned - dm->num_pages_ballooned);
 
     if (req->more_pages == 1)
         return;
 
     memset(&resp, 0, sizeof(struct dm_unballoon_response));
     resp.hdr.type = DM_UNBALLOON_RESPONSE;
     resp.hdr.trans_id = atomic_inc_return(&trans_id);
     resp.hdr.size = sizeof(struct dm_unballoon_response);
 
     vmbus_sendpacket(dm_device.dev->channel, &resp,
                 sizeof(struct dm_unballoon_response),
                 (unsigned long)NULL,
                 VM_PKT_DATA_INBAND, 0);
 
     dm->state = DM_INITIALIZED;
 }
 
 static void balloon_onchannelcallback(void *context);
 
 static int dm_thread_func(void *dm_dev)
 {
     struct hv_dynmem_device *dm = dm_dev;
 
     while (!kthread_should_stop()) {
         wait_for_completion_interruptible_timeout(
                         &dm_device.config_event, 1*HZ);
         /*
          * The host expects us to post information on the memory
          * pressure every second.
          */
         reinit_completion(&dm_device.config_event);
         post_status(dm);
     }
 
     return 0;
 }
 
 
 static void version_resp(struct hv_dynmem_device *dm,
             struct dm_version_response *vresp)
 {
     struct dm_version_request version_req;
     int ret;
 
     if (vresp->is_accepted) {
         /*
          * We are done; wakeup the
          * context waiting for version
          * negotiation.
          */
         complete(&dm->host_event);
         return;
     }
     /*
      * If there are more versions to try, continue
      * with negotiations; if not
      * shutdown the service since we are not able
      * to negotiate a suitable version number
      * with the host.
      */
     if (dm->next_version == 0)
         goto version_error;
 
     memset(&version_req, 0, sizeof(struct dm_version_request));
     version_req.hdr.type = DM_VERSION_REQUEST;
     version_req.hdr.size = sizeof(struct dm_version_request);
     version_req.hdr.trans_id = atomic_inc_return(&trans_id);
     version_req.version.version = dm->next_version;
     dm->version = version_req.version.version;
 
     /*
      * Set the next version to try in case current version fails.
      * Win7 protocol ought to be the last one to try.
      */
     switch (version_req.version.version) {
     case DYNMEM_PROTOCOL_VERSION_WIN8:
         dm->next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
         version_req.is_last_attempt = 0;
         break;
     default:
         dm->next_version = 0;
         version_req.is_last_attempt = 1;
     }
 
     ret = vmbus_sendpacket(dm->dev->channel, &version_req,
                 sizeof(struct dm_version_request),
                 (unsigned long)NULL,
                 VM_PKT_DATA_INBAND, 0);
 
     if (ret)
         goto version_error;
 
     return;
 
 version_error:
     dm->state = DM_INIT_ERROR;
     complete(&dm->host_event);
 }
 
 static void cap_resp(struct hv_dynmem_device *dm,
             struct dm_capabilities_resp_msg *cap_resp)
 {
     if (!cap_resp->is_accepted) {
         pr_err("Capabilities not accepted by host\n");
         dm->state = DM_INIT_ERROR;
     }
     complete(&dm->host_event);
 }
 
 static void balloon_onchannelcallback(void *context)
 {
     struct hv_device *dev = context;
     u32 recvlen;
     u64 requestid;
     struct dm_message *dm_msg;
     struct dm_header *dm_hdr;
     struct hv_dynmem_device *dm = hv_get_drvdata(dev);
     struct dm_balloon *bal_msg;
     struct dm_hot_add *ha_msg;
     union dm_mem_page_range *ha_pg_range;
     union dm_mem_page_range *ha_region;
 
     memset(recv_buffer, 0, sizeof(recv_buffer));
     vmbus_recvpacket(dev->channel, recv_buffer,
              HV_HYP_PAGE_SIZE, &recvlen, &requestid);
 
     if (recvlen > 0) {
         dm_msg = (struct dm_message *)recv_buffer;
         dm_hdr = &dm_msg->hdr;
 
         switch (dm_hdr->type) {
         case DM_VERSION_RESPONSE:
             version_resp(dm,
                  (struct dm_version_response *)dm_msg);
             break;
 
         case DM_CAPABILITIES_RESPONSE:
             cap_resp(dm,
                  (struct dm_capabilities_resp_msg *)dm_msg);
             break;
 
         case DM_BALLOON_REQUEST:
             if (allow_hibernation) {
                 pr_info("Ignore balloon-up request!\n");
                 break;
             }
 
             if (dm->state == DM_BALLOON_UP)
                 pr_warn("Currently ballooning\n");
             bal_msg = (struct dm_balloon *)recv_buffer;
             dm->state = DM_BALLOON_UP;
             dm_device.balloon_wrk.num_pages = bal_msg->num_pages;
             schedule_work(&dm_device.balloon_wrk.wrk);
             break;
 
         case DM_UNBALLOON_REQUEST:
             if (allow_hibernation) {
                 pr_info("Ignore balloon-down request!\n");
                 break;
             }
 
             dm->state = DM_BALLOON_DOWN;
             balloon_down(dm,
                  (struct dm_unballoon_request *)recv_buffer);
             break;
 
         case DM_MEM_HOT_ADD_REQUEST:
             if (dm->state == DM_HOT_ADD)
                 pr_warn("Currently hot-adding\n");
             dm->state = DM_HOT_ADD;
             ha_msg = (struct dm_hot_add *)recv_buffer;
             if (ha_msg->hdr.size == sizeof(struct dm_hot_add)) {
                 /*
                  * This is a normal hot-add request specifying
                  * hot-add memory.
                  */
                 dm->host_specified_ha_region = false;
                 ha_pg_range = &ha_msg->range;
                 dm->ha_wrk.ha_page_range = *ha_pg_range;
                 dm->ha_wrk.ha_region_range.page_range = 0;
             } else {
                 /*
                  * Host is specifying that we first hot-add
                  * a region and then partially populate this
                  * region.
                  */
                 dm->host_specified_ha_region = true;
                 ha_pg_range = &ha_msg->range;
                 ha_region = &ha_pg_range[1];
                 dm->ha_wrk.ha_page_range = *ha_pg_range;
                 dm->ha_wrk.ha_region_range = *ha_region;
             }
             schedule_work(&dm_device.ha_wrk.wrk);
             break;
 
         case DM_INFO_MESSAGE:
             process_info(dm, (struct dm_info_msg *)dm_msg);
             break;
 
         default:
             pr_warn_ratelimited("Unhandled message: type: %d\n", dm_hdr->type);
 
         }
     }
 
 }
 
 /* Hyper-V only supports reporting 2MB pages or higher */
 #define HV_MIN_PAGE_REPORTING_ORDER 9
 #define HV_MIN_PAGE_REPORTING_LEN (HV_HYP_PAGE_SIZE << HV_MIN_PAGE_REPORTING_ORDER)
 static int hv_free_page_report(struct page_reporting_dev_info *pr_dev_info,
             struct scatterlist *sgl, unsigned int nents)
 {
     unsigned long flags;
     struct hv_memory_hint *hint;
     int i;
     u64 status;
     struct scatterlist *sg;
 
     WARN_ON_ONCE(nents > HV_MEMORY_HINT_MAX_GPA_PAGE_RANGES);
     WARN_ON_ONCE(sgl->length < HV_MIN_PAGE_REPORTING_LEN);
     local_irq_save(flags);
     hint = *(struct hv_memory_hint **)this_cpu_ptr(hyperv_pcpu_input_arg);
     if (!hint) {
         local_irq_restore(flags);
         return -ENOSPC;
     }
 
     hint->type = HV_EXT_MEMORY_HEAT_HINT_TYPE_COLD_DISCARD;
     hint->reserved = 0;
     for_each_sg(sgl, sg, nents, i) {
         union hv_gpa_page_range *range;
 
         range = &hint->ranges[i];
         range->address_space = 0;
         /* page reporting only reports 2MB pages or higher */
         range->page.largepage = 1;
         range->page.additional_pages =
             (sg->length / HV_MIN_PAGE_REPORTING_LEN) - 1;
         range->page_size = HV_GPA_PAGE_RANGE_PAGE_SIZE_2MB;
         range->base_large_pfn =
             page_to_hvpfn(sg_page(sg)) >> HV_MIN_PAGE_REPORTING_ORDER;
     }
 
     status = hv_do_rep_hypercall(HV_EXT_CALL_MEMORY_HEAT_HINT, nents, 0,
                      hint, NULL);
     local_irq_restore(flags);
     if ((status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS) {
         pr_err("Cold memory discard hypercall failed with status %llx\n",
             status);
         return -EINVAL;
     }
 
     return 0;
 }
 
 static void enable_page_reporting(void)
 {
     int ret;
 
     /* Essentially, validating 'PAGE_REPORTING_MIN_ORDER' is big enough. */
     if (pageblock_order < HV_MIN_PAGE_REPORTING_ORDER) {
         pr_debug("Cold memory discard is only supported on 2MB pages and above\n");
         return;
     }
 
     if (!hv_query_ext_cap(HV_EXT_CAPABILITY_MEMORY_COLD_DISCARD_HINT)) {
         pr_debug("Cold memory discard hint not supported by Hyper-V\n");
         return;
     }
 
     BUILD_BUG_ON(PAGE_REPORTING_CAPACITY > HV_MEMORY_HINT_MAX_GPA_PAGE_RANGES);
     dm_device.pr_dev_info.report = hv_free_page_report;
     ret = page_reporting_register(&dm_device.pr_dev_info);
     if (ret < 0) {
         dm_device.pr_dev_info.report = NULL;
         pr_err("Failed to enable cold memory discard: %d\n", ret);
     } else {
         pr_info("Cold memory discard hint enabled\n");
     }
 }
 
 static void disable_page_reporting(void)
 {
     if (dm_device.pr_dev_info.report) {
         page_reporting_unregister(&dm_device.pr_dev_info);
         dm_device.pr_dev_info.report = NULL;
     }
 }
 
 static int ballooning_enabled(void)
 {
     /*
      * Disable ballooning if the page size is not 4k (HV_HYP_PAGE_SIZE),
      * since currently it's unclear to us whether an unballoon request can
      * make sure all page ranges are guest page size aligned.
      */
     if (PAGE_SIZE != HV_HYP_PAGE_SIZE) {
         pr_info("Ballooning disabled because page size is not 4096 bytes\n");
         return 0;
     }
 
     return 1;
 }
 
 static int hot_add_enabled(void)
 {
     /*
      * Disable hot add on ARM64, because we currently rely on
      * memory_add_physaddr_to_nid() to get a node id of a hot add range,
      * however ARM64's memory_add_physaddr_to_nid() always return 0 and
      * DM_MEM_HOT_ADD_REQUEST doesn't have the NUMA node information for
      * add_memory().
      */
     if (IS_ENABLED(CONFIG_ARM64)) {
         pr_info("Memory hot add disabled on ARM64\n");
         return 0;
     }
 
     return 1;
 }
 
 static int balloon_connect_vsp(struct hv_device *dev)
 {
     struct dm_version_request version_req;
     struct dm_capabilities cap_msg;
     unsigned long t;
     int ret;
 
     /*
      * max_pkt_size should be large enough for one vmbus packet header plus
      * our receive buffer size. Hyper-V sends messages up to
      * HV_HYP_PAGE_SIZE bytes long on balloon channel.
      */
     dev->channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
 
     ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0,
              balloon_onchannelcallback, dev);
     if (ret)
         return ret;
 
     /*
      * Initiate the hand shake with the host and negotiate
      * a version that the host can support. We start with the
      * highest version number and go down if the host cannot
      * support it.
      */
     memset(&version_req, 0, sizeof(struct dm_version_request));
     version_req.hdr.type = DM_VERSION_REQUEST;
     version_req.hdr.size = sizeof(struct dm_version_request);
     version_req.hdr.trans_id = atomic_inc_return(&trans_id);
     version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN10;
     version_req.is_last_attempt = 0;
     dm_device.version = version_req.version.version;
 
     ret = vmbus_sendpacket(dev->channel, &version_req,
                    sizeof(struct dm_version_request),
                    (unsigned long)NULL, VM_PKT_DATA_INBAND, 0);
     if (ret)
         goto out;
 
     t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
     if (t == 0) {
         ret = -ETIMEDOUT;
         goto out;
     }
 
     /*
      * If we could not negotiate a compatible version with the host
      * fail the probe function.
      */
     if (dm_device.state == DM_INIT_ERROR) {
         ret = -EPROTO;
         goto out;
     }
 
     pr_info("Using Dynamic Memory protocol version %u.%u\n",
         DYNMEM_MAJOR_VERSION(dm_device.version),
         DYNMEM_MINOR_VERSION(dm_device.version));
 
     /*
      * Now submit our capabilities to the host.
      */
     memset(&cap_msg, 0, sizeof(struct dm_capabilities));
     cap_msg.hdr.type = DM_CAPABILITIES_REPORT;
     cap_msg.hdr.size = sizeof(struct dm_capabilities);
     cap_msg.hdr.trans_id = atomic_inc_return(&trans_id);
 
     /*
      * When hibernation (i.e. virtual ACPI S4 state) is enabled, the host
      * currently still requires the bits to be set, so we have to add code
      * to fail the host's hot-add and balloon up/down requests, if any.
      */
     cap_msg.caps.cap_bits.balloon = ballooning_enabled();
     cap_msg.caps.cap_bits.hot_add = hot_add_enabled();
 
     /*
      * Specify our alignment requirements as it relates
      * memory hot-add. Specify 128MB alignment.
      */
     cap_msg.caps.cap_bits.hot_add_alignment = 7;
 
     /*
      * Currently the host does not use these
      * values and we set them to what is done in the
      * Windows driver.
      */
     cap_msg.min_page_cnt = 0;
     cap_msg.max_page_number = -1;
 
     ret = vmbus_sendpacket(dev->channel, &cap_msg,
                    sizeof(struct dm_capabilities),
                    (unsigned long)NULL, VM_PKT_DATA_INBAND, 0);
     if (ret)
         goto out;
 
     t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
     if (t == 0) {
         ret = -ETIMEDOUT;
         goto out;
     }
 
     /*
      * If the host does not like our capabilities,
      * fail the probe function.
      */
     if (dm_device.state == DM_INIT_ERROR) {
         ret = -EPROTO;
         goto out;
     }
 
     return 0;
 out:
     vmbus_close(dev->channel);
     return ret;
 }
 
 /*
  * DEBUGFS Interface
  */
 #ifdef CONFIG_DEBUG_FS
 
 /**
  * hv_balloon_debug_show - shows statistics of balloon operations.
  * @f: pointer to the &struct seq_file.
  * @offset: ignored.
  *
  * Provides the statistics that can be accessed in hv-balloon in the debugfs.
  *
  * Return: zero on success or an error code.
  */
 static int hv_balloon_debug_show(struct seq_file *f, void *offset)
 {
     struct hv_dynmem_device *dm = f->private;
     char *sname;
 
     seq_printf(f, "%-22s: %u.%u\n", "host_version",
                 DYNMEM_MAJOR_VERSION(dm->version),
                 DYNMEM_MINOR_VERSION(dm->version));
 
     seq_printf(f, "%-22s:", "capabilities");
     if (ballooning_enabled())
         seq_puts(f, " enabled");
 
     if (hot_add_enabled())
         seq_puts(f, " hot_add");
 
     seq_puts(f, "\n");
 
     seq_printf(f, "%-22s: %u", "state", dm->state);
     switch (dm->state) {
     case DM_INITIALIZING:
             sname = "Initializing";
             break;
     case DM_INITIALIZED:
             sname = "Initialized";
             break;
     case DM_BALLOON_UP:
             sname = "Balloon Up";
             break;
     case DM_BALLOON_DOWN:
             sname = "Balloon Down";
             break;
     case DM_HOT_ADD:
             sname = "Hot Add";
             break;
     case DM_INIT_ERROR:
             sname = "Error";
             break;
     default:
             sname = "Unknown";
     }
     seq_printf(f, " (%s)\n", sname);
 
     /* HV Page Size */
     seq_printf(f, "%-22s: %ld\n", "page_size", HV_HYP_PAGE_SIZE);
 
     /* Pages added with hot_add */
     seq_printf(f, "%-22s: %u\n", "pages_added", dm->num_pages_added);
 
     /* pages that are "onlined"/used from pages_added */
     seq_printf(f, "%-22s: %u\n", "pages_onlined", dm->num_pages_onlined);
 
     /* pages we have given back to host */
     seq_printf(f, "%-22s: %u\n", "pages_ballooned", dm->num_pages_ballooned);
 
     seq_printf(f, "%-22s: %lu\n", "total_pages_committed",
                 get_pages_committed(dm));
 
     seq_printf(f, "%-22s: %llu\n", "max_dynamic_page_count",
                 dm->max_dynamic_page_count);
 
     return 0;
 }
 
 DEFINE_SHOW_ATTRIBUTE(hv_balloon_debug);
 
 static void  hv_balloon_debugfs_init(struct hv_dynmem_device *b)
 {
     debugfs_create_file("hv-balloon", 0444, NULL, b,
             &hv_balloon_debug_fops);
 }
 
 static void  hv_balloon_debugfs_exit(struct hv_dynmem_device *b)
 {
     debugfs_remove(debugfs_lookup("hv-balloon", NULL));
 }
 
 #else
 
 static inline void hv_balloon_debugfs_init(struct hv_dynmem_device  *b)
 {
 }
 
 static inline void hv_balloon_debugfs_exit(struct hv_dynmem_device *b)
 {
 }
 
 #endif  /* CONFIG_DEBUG_FS */
 
 static int balloon_probe(struct hv_device *dev,
              const struct hv_vmbus_device_id *dev_id)
 {
     int ret;
 
     allow_hibernation = hv_is_hibernation_supported();
     if (allow_hibernation)
         hot_add = false;
 
 #ifdef CONFIG_MEMORY_HOTPLUG
     do_hot_add = hot_add;
 #else
     do_hot_add = false;
 #endif
     dm_device.dev = dev;
     dm_device.state = DM_INITIALIZING;
     dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN8;
     init_completion(&dm_device.host_event);
     init_completion(&dm_device.config_event);
     INIT_LIST_HEAD(&dm_device.ha_region_list);
     spin_lock_init(&dm_device.ha_lock);
     INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
     INIT_WORK(&dm_device.ha_wrk.wrk, hot_add_req);
     dm_device.host_specified_ha_region = false;
 
 #ifdef CONFIG_MEMORY_HOTPLUG
     set_online_page_callback(&hv_online_page);
     init_completion(&dm_device.ol_waitevent);
     register_memory_notifier(&hv_memory_nb);
 #endif
 
     hv_set_drvdata(dev, &dm_device);
 
     ret = balloon_connect_vsp(dev);
     if (ret != 0)
         goto connect_error;
 
     enable_page_reporting();
     dm_device.state = DM_INITIALIZED;
 
     dm_device.thread =
          kthread_run(dm_thread_func, &dm_device, "hv_balloon");
     if (IS_ERR(dm_device.thread)) {
         ret = PTR_ERR(dm_device.thread);
         goto probe_error;
     }
 
     hv_balloon_debugfs_init(&dm_device);
 
     return 0;
 
 probe_error:
     dm_device.state = DM_INIT_ERROR;
     dm_device.thread  = NULL;
     disable_page_reporting();
     vmbus_close(dev->channel);
 connect_error:
 #ifdef CONFIG_MEMORY_HOTPLUG
     unregister_memory_notifier(&hv_memory_nb);
     restore_online_page_callback(&hv_online_page);
 #endif
     return ret;
 }
 
 static int balloon_remove(struct hv_device *dev)
 {
     struct hv_dynmem_device *dm = hv_get_drvdata(dev);
     struct hv_hotadd_state *has, *tmp;
     struct hv_hotadd_gap *gap, *tmp_gap;
     unsigned long flags;
 
     if (dm->num_pages_ballooned != 0)
         pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
 
     hv_balloon_debugfs_exit(dm);
 
     cancel_work_sync(&dm->balloon_wrk.wrk);
     cancel_work_sync(&dm->ha_wrk.wrk);
 
     kthread_stop(dm->thread);
 
     /*
      * This is to handle the case when balloon_resume()
      * call has failed and some cleanup has been done as
      * a part of the error handling.
      */
     if (dm_device.state != DM_INIT_ERROR) {
         disable_page_reporting();
         vmbus_close(dev->channel);
 #ifdef CONFIG_MEMORY_HOTPLUG
         unregister_memory_notifier(&hv_memory_nb);
         restore_online_page_callback(&hv_online_page);
 #endif
     }
 
     spin_lock_irqsave(&dm_device.ha_lock, flags);
     list_for_each_entry_safe(has, tmp, &dm->ha_region_list, list) {
         list_for_each_entry_safe(gap, tmp_gap, &has->gap_list, list) {
             list_del(&gap->list);
             kfree(gap);
         }
         list_del(&has->list);
         kfree(has);
     }
     spin_unlock_irqrestore(&dm_device.ha_lock, flags);
 
     return 0;
 }
 
 static int balloon_suspend(struct hv_device *hv_dev)
 {
     struct hv_dynmem_device *dm = hv_get_drvdata(hv_dev);
 
     tasklet_disable(&hv_dev->channel->callback_event);
 
     cancel_work_sync(&dm->balloon_wrk.wrk);
     cancel_work_sync(&dm->ha_wrk.wrk);
 
     if (dm->thread) {
         kthread_stop(dm->thread);
         dm->thread = NULL;
         vmbus_close(hv_dev->channel);
     }
 
     tasklet_enable(&hv_dev->channel->callback_event);
 
     return 0;
 
 }
 
 static int balloon_resume(struct hv_device *dev)
 {
     int ret;
 
     dm_device.state = DM_INITIALIZING;
 
     ret = balloon_connect_vsp(dev);
 
     if (ret != 0)
         goto out;
 
     dm_device.thread =
          kthread_run(dm_thread_func, &dm_device, "hv_balloon");
     if (IS_ERR(dm_device.thread)) {
         ret = PTR_ERR(dm_device.thread);
         dm_device.thread = NULL;
         goto close_channel;
     }
 
     dm_device.state = DM_INITIALIZED;
     return 0;
 close_channel:
     vmbus_close(dev->channel);
 out:
     dm_device.state = DM_INIT_ERROR;
     disable_page_reporting();
 #ifdef CONFIG_MEMORY_HOTPLUG
     unregister_memory_notifier(&hv_memory_nb);
     restore_online_page_callback(&hv_online_page);
 #endif
     return ret;
 }
 
 static const struct hv_vmbus_device_id id_table[] = {
     /* Dynamic Memory Class ID */
     /* 525074DC-8985-46e2-8057-A307DC18A502 */
     { HV_DM_GUID, },
     { },
 };
 
 MODULE_DEVICE_TABLE(vmbus, id_table);
 
 static  struct hv_driver balloon_drv = {
     .name = "hv_balloon",
     .id_table = id_table,
     .probe =  balloon_probe,
     .remove =  balloon_remove,
     .suspend = balloon_suspend,
     .resume = balloon_resume,
     .driver = {
         .probe_type = PROBE_PREFER_ASYNCHRONOUS,
     },
 };
 
 static int __init init_balloon_drv(void)
 {
 
     return vmbus_driver_register(&balloon_drv);
 }
 
 module_init(init_balloon_drv);
 
 MODULE_DESCRIPTION("Hyper-V Balloon");
 MODULE_LICENSE("GPL");

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