qemu

migration.c (144203B)

---

 /*
  * QEMU live migration
  *
  * Copyright IBM, Corp. 2008
  *
  * Authors:
  *  Anthony Liguori   <aliguori@us.ibm.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
  *
  * Contributions after 2012-01-13 are licensed under the terms of the
  * GNU GPL, version 2 or (at your option) any later version.
  */
 
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 #include "migration/blocker.h"
 #include "exec.h"
 #include "fd.h"
 #include "socket.h"
 #include "sysemu/runstate.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/cpu-throttle.h"
 #include "rdma.h"
 #include "ram.h"
 #include "migration/global_state.h"
 #include "migration/misc.h"
 #include "migration.h"
 #include "savevm.h"
 #include "qemu-file.h"
 #include "migration/vmstate.h"
 #include "block/block.h"
 #include "qapi/error.h"
 #include "qapi/clone-visitor.h"
 #include "qapi/qapi-visit-migration.h"
 #include "qapi/qapi-visit-sockets.h"
 #include "qapi/qapi-commands-migration.h"
 #include "qapi/qapi-events-migration.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qnull.h"
 #include "qemu/rcu.h"
 #include "block.h"
 #include "postcopy-ram.h"
 #include "qemu/thread.h"
 #include "trace.h"
 #include "exec/target_page.h"
 #include "io/channel-buffer.h"
 #include "io/channel-tls.h"
 #include "migration/colo.h"
 #include "hw/boards.h"
 #include "hw/qdev-properties.h"
 #include "hw/qdev-properties-system.h"
 #include "monitor/monitor.h"
 #include "net/announce.h"
 #include "qemu/queue.h"
 #include "multifd.h"
 #include "qemu/yank.h"
 #include "sysemu/cpus.h"
 #include "yank_functions.h"
 #include "sysemu/qtest.h"
 
 #define MAX_THROTTLE  (128 << 20)      /* Migration transfer speed throttling */
 
 /* Amount of time to allocate to each "chunk" of bandwidth-throttled
  * data. */
 #define BUFFER_DELAY     100
 #define XFER_LIMIT_RATIO (1000 / BUFFER_DELAY)
 
 /* Time in milliseconds we are allowed to stop the source,
  * for sending the last part */
 #define DEFAULT_MIGRATE_SET_DOWNTIME 300
 
 /* Maximum migrate downtime set to 2000 seconds */
 #define MAX_MIGRATE_DOWNTIME_SECONDS 2000
 #define MAX_MIGRATE_DOWNTIME (MAX_MIGRATE_DOWNTIME_SECONDS * 1000)
 
 /* Default compression thread count */
 #define DEFAULT_MIGRATE_COMPRESS_THREAD_COUNT 8
 /* Default decompression thread count, usually decompression is at
  * least 4 times as fast as compression.*/
 #define DEFAULT_MIGRATE_DECOMPRESS_THREAD_COUNT 2
 /*0: means nocompress, 1: best speed, ... 9: best compress ratio */
 #define DEFAULT_MIGRATE_COMPRESS_LEVEL 1
 /* Define default autoconverge cpu throttle migration parameters */
 #define DEFAULT_MIGRATE_THROTTLE_TRIGGER_THRESHOLD 50
 #define DEFAULT_MIGRATE_CPU_THROTTLE_INITIAL 20
 #define DEFAULT_MIGRATE_CPU_THROTTLE_INCREMENT 10
 #define DEFAULT_MIGRATE_MAX_CPU_THROTTLE 99
 
 /* Migration XBZRLE default cache size */
 #define DEFAULT_MIGRATE_XBZRLE_CACHE_SIZE (64 * 1024 * 1024)
 
 /* The delay time (in ms) between two COLO checkpoints */
 #define DEFAULT_MIGRATE_X_CHECKPOINT_DELAY (200 * 100)
 #define DEFAULT_MIGRATE_MULTIFD_CHANNELS 2
 #define DEFAULT_MIGRATE_MULTIFD_COMPRESSION MULTIFD_COMPRESSION_NONE
 /* 0: means nocompress, 1: best speed, ... 9: best compress ratio */
 #define DEFAULT_MIGRATE_MULTIFD_ZLIB_LEVEL 1
 /* 0: means nocompress, 1: best speed, ... 20: best compress ratio */
 #define DEFAULT_MIGRATE_MULTIFD_ZSTD_LEVEL 1
 
 /* Background transfer rate for postcopy, 0 means unlimited, note
  * that page requests can still exceed this limit.
  */
 #define DEFAULT_MIGRATE_MAX_POSTCOPY_BANDWIDTH 0
 
 /*
  * Parameters for self_announce_delay giving a stream of RARP/ARP
  * packets after migration.
  */
 #define DEFAULT_MIGRATE_ANNOUNCE_INITIAL  50
 #define DEFAULT_MIGRATE_ANNOUNCE_MAX     550
 #define DEFAULT_MIGRATE_ANNOUNCE_ROUNDS    5
 #define DEFAULT_MIGRATE_ANNOUNCE_STEP    100
 
 static NotifierList migration_state_notifiers =
     NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
 
 /* Messages sent on the return path from destination to source */
 enum mig_rp_message_type {
     MIG_RP_MSG_INVALID = 0,  /* Must be 0 */
     MIG_RP_MSG_SHUT,         /* sibling will not send any more RP messages */
     MIG_RP_MSG_PONG,         /* Response to a PING; data (seq: be32 ) */
 
     MIG_RP_MSG_REQ_PAGES_ID, /* data (start: be64, len: be32, id: string) */
     MIG_RP_MSG_REQ_PAGES,    /* data (start: be64, len: be32) */
     MIG_RP_MSG_RECV_BITMAP,  /* send recved_bitmap back to source */
     MIG_RP_MSG_RESUME_ACK,   /* tell source that we are ready to resume */
 
     MIG_RP_MSG_MAX
 };
 
 /* Migration capabilities set */
 struct MigrateCapsSet {
     int size;                       /* Capability set size */
     MigrationCapability caps[];     /* Variadic array of capabilities */
 };
 typedef struct MigrateCapsSet MigrateCapsSet;
 
 /* Define and initialize MigrateCapsSet */
 #define INITIALIZE_MIGRATE_CAPS_SET(_name, ...)   \
     MigrateCapsSet _name = {    \
         .size = sizeof((int []) { __VA_ARGS__ }) / sizeof(int), \
         .caps = { __VA_ARGS__ } \
     }
 
 /* Background-snapshot compatibility check list */
 static const
 INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_snapshot,
     MIGRATION_CAPABILITY_POSTCOPY_RAM,
     MIGRATION_CAPABILITY_DIRTY_BITMAPS,
     MIGRATION_CAPABILITY_POSTCOPY_BLOCKTIME,
     MIGRATION_CAPABILITY_LATE_BLOCK_ACTIVATE,
     MIGRATION_CAPABILITY_RETURN_PATH,
     MIGRATION_CAPABILITY_MULTIFD,
     MIGRATION_CAPABILITY_PAUSE_BEFORE_SWITCHOVER,
     MIGRATION_CAPABILITY_AUTO_CONVERGE,
     MIGRATION_CAPABILITY_RELEASE_RAM,
     MIGRATION_CAPABILITY_RDMA_PIN_ALL,
     MIGRATION_CAPABILITY_COMPRESS,
     MIGRATION_CAPABILITY_XBZRLE,
     MIGRATION_CAPABILITY_X_COLO,
     MIGRATION_CAPABILITY_VALIDATE_UUID,
     MIGRATION_CAPABILITY_ZERO_COPY_SEND);
 
 /* When we add fault tolerance, we could have several
    migrations at once.  For now we don't need to add
    dynamic creation of migration */
 
 static MigrationState *current_migration;
 static MigrationIncomingState *current_incoming;
 
 static GSList *migration_blockers;
 
 static bool migration_object_check(MigrationState *ms, Error **errp);
 static int migration_maybe_pause(MigrationState *s,
                                  int *current_active_state,
                                  int new_state);
 static void migrate_fd_cancel(MigrationState *s);
 
 static bool migrate_allow_multi_channels = true;
 
 void migrate_protocol_allow_multi_channels(bool allow)
 {
     migrate_allow_multi_channels = allow;
 }
 
 bool migrate_multi_channels_is_allowed(void)
 {
     return migrate_allow_multi_channels;
 }
 
 static gint page_request_addr_cmp(gconstpointer ap, gconstpointer bp)
 {
     uintptr_t a = (uintptr_t) ap, b = (uintptr_t) bp;
 
     return (a > b) - (a < b);
 }
 
 void migration_object_init(void)
 {
     /* This can only be called once. */
     assert(!current_migration);
     current_migration = MIGRATION_OBJ(object_new(TYPE_MIGRATION));
 
     /*
      * Init the migrate incoming object as well no matter whether
      * we'll use it or not.
      */
     assert(!current_incoming);
     current_incoming = g_new0(MigrationIncomingState, 1);
     current_incoming->state = MIGRATION_STATUS_NONE;
     current_incoming->postcopy_remote_fds =
         g_array_new(FALSE, TRUE, sizeof(struct PostCopyFD));
     qemu_mutex_init(&current_incoming->rp_mutex);
     qemu_mutex_init(&current_incoming->postcopy_prio_thread_mutex);
     qemu_event_init(&current_incoming->main_thread_load_event, false);
     qemu_sem_init(&current_incoming->postcopy_pause_sem_dst, 0);
     qemu_sem_init(&current_incoming->postcopy_pause_sem_fault, 0);
     qemu_sem_init(&current_incoming->postcopy_pause_sem_fast_load, 0);
     qemu_mutex_init(&current_incoming->page_request_mutex);
     current_incoming->page_requested = g_tree_new(page_request_addr_cmp);
 
     migration_object_check(current_migration, &error_fatal);
 
     blk_mig_init();
     ram_mig_init();
     dirty_bitmap_mig_init();
 }
 
 void migration_cancel(const Error *error)
 {
     if (error) {
         migrate_set_error(current_migration, error);
     }
     migrate_fd_cancel(current_migration);
 }
 
 void migration_shutdown(void)
 {
     /*
      * When the QEMU main thread exit, the COLO thread
      * may wait a semaphore. So, we should wakeup the
      * COLO thread before migration shutdown.
      */
     colo_shutdown();
     /*
      * Cancel the current migration - that will (eventually)
      * stop the migration using this structure
      */
     migration_cancel(NULL);
     object_unref(OBJECT(current_migration));
 
     /*
      * Cancel outgoing migration of dirty bitmaps. It should
      * at least unref used block nodes.
      */
     dirty_bitmap_mig_cancel_outgoing();
 
     /*
      * Cancel incoming migration of dirty bitmaps. Dirty bitmaps
      * are non-critical data, and their loss never considered as
      * something serious.
      */
     dirty_bitmap_mig_cancel_incoming();
 }
 
 /* For outgoing */
 MigrationState *migrate_get_current(void)
 {
     /* This can only be called after the object created. */
     assert(current_migration);
     return current_migration;
 }
 
 MigrationIncomingState *migration_incoming_get_current(void)
 {
     assert(current_incoming);
     return current_incoming;
 }
 
 void migration_incoming_transport_cleanup(MigrationIncomingState *mis)
 {
     if (mis->socket_address_list) {
         qapi_free_SocketAddressList(mis->socket_address_list);
         mis->socket_address_list = NULL;
     }
 
     if (mis->transport_cleanup) {
         mis->transport_cleanup(mis->transport_data);
         mis->transport_data = mis->transport_cleanup = NULL;
     }
 }
 
 void migration_incoming_state_destroy(void)
 {
     struct MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (mis->to_src_file) {
         /* Tell source that we are done */
         migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
         qemu_fclose(mis->to_src_file);
         mis->to_src_file = NULL;
     }
 
     if (mis->from_src_file) {
         migration_ioc_unregister_yank_from_file(mis->from_src_file);
         qemu_fclose(mis->from_src_file);
         mis->from_src_file = NULL;
     }
     if (mis->postcopy_remote_fds) {
         g_array_free(mis->postcopy_remote_fds, TRUE);
         mis->postcopy_remote_fds = NULL;
     }
 
     migration_incoming_transport_cleanup(mis);
     qemu_event_reset(&mis->main_thread_load_event);
 
     if (mis->page_requested) {
         g_tree_destroy(mis->page_requested);
         mis->page_requested = NULL;
     }
 
     if (mis->postcopy_qemufile_dst) {
         migration_ioc_unregister_yank_from_file(mis->postcopy_qemufile_dst);
         qemu_fclose(mis->postcopy_qemufile_dst);
         mis->postcopy_qemufile_dst = NULL;
     }
 
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
 
 static void migrate_generate_event(int new_state)
 {
     if (migrate_use_events()) {
         qapi_event_send_migration(new_state);
     }
 }
 
 static bool migrate_late_block_activate(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[
         MIGRATION_CAPABILITY_LATE_BLOCK_ACTIVATE];
 }
 
 /*
  * Send a message on the return channel back to the source
  * of the migration.
  */
 static int migrate_send_rp_message(MigrationIncomingState *mis,
                                    enum mig_rp_message_type message_type,
                                    uint16_t len, void *data)
 {
     int ret = 0;
 
     trace_migrate_send_rp_message((int)message_type, len);
     QEMU_LOCK_GUARD(&mis->rp_mutex);
 
     /*
      * It's possible that the file handle got lost due to network
      * failures.
      */
     if (!mis->to_src_file) {
         ret = -EIO;
         return ret;
     }
 
     qemu_put_be16(mis->to_src_file, (unsigned int)message_type);
     qemu_put_be16(mis->to_src_file, len);
     qemu_put_buffer(mis->to_src_file, data, len);
     qemu_fflush(mis->to_src_file);
 
     /* It's possible that qemu file got error during sending */
     ret = qemu_file_get_error(mis->to_src_file);
 
     return ret;
 }
 
 /* Request one page from the source VM at the given start address.
  *   rb: the RAMBlock to request the page in
  *   Start: Address offset within the RB
  *   Len: Length in bytes required - must be a multiple of pagesize
  */
 int migrate_send_rp_message_req_pages(MigrationIncomingState *mis,
                                       RAMBlock *rb, ram_addr_t start)
 {
     uint8_t bufc[12 + 1 + 255]; /* start (8), len (4), rbname up to 256 */
     size_t msglen = 12; /* start + len */
     size_t len = qemu_ram_pagesize(rb);
     enum mig_rp_message_type msg_type;
     const char *rbname;
     int rbname_len;
 
     *(uint64_t *)bufc = cpu_to_be64((uint64_t)start);
     *(uint32_t *)(bufc + 8) = cpu_to_be32((uint32_t)len);
 
     /*
      * We maintain the last ramblock that we requested for page.  Note that we
      * don't need locking because this function will only be called within the
      * postcopy ram fault thread.
      */
     if (rb != mis->last_rb) {
         mis->last_rb = rb;
 
         rbname = qemu_ram_get_idstr(rb);
         rbname_len = strlen(rbname);
 
         assert(rbname_len < 256);
 
         bufc[msglen++] = rbname_len;
         memcpy(bufc + msglen, rbname, rbname_len);
         msglen += rbname_len;
         msg_type = MIG_RP_MSG_REQ_PAGES_ID;
     } else {
         msg_type = MIG_RP_MSG_REQ_PAGES;
     }
 
     return migrate_send_rp_message(mis, msg_type, msglen, bufc);
 }
 
 int migrate_send_rp_req_pages(MigrationIncomingState *mis,
                               RAMBlock *rb, ram_addr_t start, uint64_t haddr)
 {
     void *aligned = (void *)(uintptr_t)ROUND_DOWN(haddr, qemu_ram_pagesize(rb));
     bool received = false;
 
     WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) {
         received = ramblock_recv_bitmap_test_byte_offset(rb, start);
         if (!received && !g_tree_lookup(mis->page_requested, aligned)) {
             /*
              * The page has not been received, and it's not yet in the page
              * request list.  Queue it.  Set the value of element to 1, so that
              * things like g_tree_lookup() will return TRUE (1) when found.
              */
             g_tree_insert(mis->page_requested, aligned, (gpointer)1);
             mis->page_requested_count++;
             trace_postcopy_page_req_add(aligned, mis->page_requested_count);
         }
     }
 
     /*
      * If the page is there, skip sending the message.  We don't even need the
      * lock because as long as the page arrived, it'll be there forever.
      */
     if (received) {
         return 0;
     }
 
     return migrate_send_rp_message_req_pages(mis, rb, start);
 }
 
 static bool migration_colo_enabled;
 bool migration_incoming_colo_enabled(void)
 {
     return migration_colo_enabled;
 }
 
 void migration_incoming_disable_colo(void)
 {
     ram_block_discard_disable(false);
     migration_colo_enabled = false;
 }
 
 int migration_incoming_enable_colo(void)
 {
     if (ram_block_discard_disable(true)) {
         error_report("COLO: cannot disable RAM discard");
         return -EBUSY;
     }
     migration_colo_enabled = true;
     return 0;
 }
 
 void migrate_add_address(SocketAddress *address)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     QAPI_LIST_PREPEND(mis->socket_address_list,
                       QAPI_CLONE(SocketAddress, address));
 }
 
 static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
 
     migrate_protocol_allow_multi_channels(false); /* reset it anyway */
     qapi_event_send_migration(MIGRATION_STATUS_SETUP);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
         migrate_protocol_allow_multi_channels(true);
         socket_start_incoming_migration(p ? p : uri, errp);
 #ifdef CONFIG_RDMA
     } else if (strstart(uri, "rdma:", &p)) {
         rdma_start_incoming_migration(p, errp);
 #endif
     } else if (strstart(uri, "exec:", &p)) {
         exec_start_incoming_migration(p, errp);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_incoming_migration(p, errp);
     } else {
         error_setg(errp, "unknown migration protocol: %s", uri);
     }
 }
 
 static void process_incoming_migration_bh(void *opaque)
 {
     Error *local_err = NULL;
     MigrationIncomingState *mis = opaque;
 
     /* If capability late_block_activate is set:
      * Only fire up the block code now if we're going to restart the
      * VM, else 'cont' will do it.
      * This causes file locking to happen; so we don't want it to happen
      * unless we really are starting the VM.
      */
     if (!migrate_late_block_activate() ||
          (autostart && (!global_state_received() ||
             global_state_get_runstate() == RUN_STATE_RUNNING))) {
         /* Make sure all file formats throw away their mutable metadata.
          * If we get an error here, just don't restart the VM yet. */
         bdrv_activate_all(&local_err);
         if (local_err) {
             error_report_err(local_err);
             local_err = NULL;
             autostart = false;
         }
     }
 
     /*
      * This must happen after all error conditions are dealt with and
      * we're sure the VM is going to be running on this host.
      */
     qemu_announce_self(&mis->announce_timer, migrate_announce_params());
 
     if (multifd_load_cleanup(&local_err) != 0) {
         error_report_err(local_err);
         autostart = false;
     }
     /* If global state section was not received or we are in running
        state, we need to obey autostart. Any other state is set with
        runstate_set. */
 
     dirty_bitmap_mig_before_vm_start();
 
     if (!global_state_received() ||
         global_state_get_runstate() == RUN_STATE_RUNNING) {
         if (autostart) {
             vm_start();
         } else {
             runstate_set(RUN_STATE_PAUSED);
         }
     } else if (migration_incoming_colo_enabled()) {
         migration_incoming_disable_colo();
         vm_start();
     } else {
         runstate_set(global_state_get_runstate());
     }
     /*
      * This must happen after any state changes since as soon as an external
      * observer sees this event they might start to prod at the VM assuming
      * it's ready to use.
      */
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_COMPLETED);
     qemu_bh_delete(mis->bh);
     migration_incoming_state_destroy();
 }
 
 static void coroutine_fn
 process_incoming_migration_co(void *opaque)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     PostcopyState ps;
     int ret;
     Error *local_err = NULL;
 
     assert(mis->from_src_file);
     mis->migration_incoming_co = qemu_coroutine_self();
     mis->largest_page_size = qemu_ram_pagesize_largest();
     postcopy_state_set(POSTCOPY_INCOMING_NONE);
     migrate_set_state(&mis->state, MIGRATION_STATUS_NONE,
                       MIGRATION_STATUS_ACTIVE);
     ret = qemu_loadvm_state(mis->from_src_file);
 
     ps = postcopy_state_get();
     trace_process_incoming_migration_co_end(ret, ps);
     if (ps != POSTCOPY_INCOMING_NONE) {
         if (ps == POSTCOPY_INCOMING_ADVISE) {
             /*
              * Where a migration had postcopy enabled (and thus went to advise)
              * but managed to complete within the precopy period, we can use
              * the normal exit.
              */
             postcopy_ram_incoming_cleanup(mis);
         } else if (ret >= 0) {
             /*
              * Postcopy was started, cleanup should happen at the end of the
              * postcopy thread.
              */
             trace_process_incoming_migration_co_postcopy_end_main();
             return;
         }
         /* Else if something went wrong then just fall out of the normal exit */
     }
 
     /* we get COLO info, and know if we are in COLO mode */
     if (!ret && migration_incoming_colo_enabled()) {
         /* Make sure all file formats throw away their mutable metadata */
         bdrv_activate_all(&local_err);
         if (local_err) {
             error_report_err(local_err);
             goto fail;
         }
 
         qemu_thread_create(&mis->colo_incoming_thread, "COLO incoming",
              colo_process_incoming_thread, mis, QEMU_THREAD_JOINABLE);
         mis->have_colo_incoming_thread = true;
         qemu_coroutine_yield();
 
         qemu_mutex_unlock_iothread();
         /* Wait checkpoint incoming thread exit before free resource */
         qemu_thread_join(&mis->colo_incoming_thread);
         qemu_mutex_lock_iothread();
         /* We hold the global iothread lock, so it is safe here */
         colo_release_ram_cache();
     }
 
     if (ret < 0) {
         error_report("load of migration failed: %s", strerror(-ret));
         goto fail;
     }
     mis->bh = qemu_bh_new(process_incoming_migration_bh, mis);
     qemu_bh_schedule(mis->bh);
     mis->migration_incoming_co = NULL;
     return;
 fail:
     local_err = NULL;
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_FAILED);
     qemu_fclose(mis->from_src_file);
     if (multifd_load_cleanup(&local_err) != 0) {
         error_report_err(local_err);
     }
     exit(EXIT_FAILURE);
 }
 
 /**
  * migration_incoming_setup: Setup incoming migration
  * @f: file for main migration channel
  * @errp: where to put errors
  *
  * Returns: %true on success, %false on error.
  */
 static bool migration_incoming_setup(QEMUFile *f, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (multifd_load_setup(errp) != 0) {
         return false;
     }
 
     if (!mis->from_src_file) {
         mis->from_src_file = f;
     }
     qemu_file_set_blocking(f, false);
     return true;
 }
 
 void migration_incoming_process(void)
 {
     Coroutine *co = qemu_coroutine_create(process_incoming_migration_co, NULL);
     qemu_coroutine_enter(co);
 }
 
 /* Returns true if recovered from a paused migration, otherwise false */
 static bool postcopy_try_recover(void)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (mis->state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
         /* Resumed from a paused postcopy migration */
 
         /* This should be set already in migration_incoming_setup() */
         assert(mis->from_src_file);
         /* Postcopy has standalone thread to do vm load */
         qemu_file_set_blocking(mis->from_src_file, true);
 
         /* Re-configure the return path */
         mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
 
         migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
                           MIGRATION_STATUS_POSTCOPY_RECOVER);
 
         /*
          * Here, we only wake up the main loading thread (while the
          * rest threads will still be waiting), so that we can receive
          * commands from source now, and answer it if needed. The
          * rest threads will be woken up afterwards until we are sure
          * that source is ready to reply to page requests.
          */
         qemu_sem_post(&mis->postcopy_pause_sem_dst);
         return true;
     }
 
     return false;
 }
 
 void migration_fd_process_incoming(QEMUFile *f, Error **errp)
 {
     if (!migration_incoming_setup(f, errp)) {
         return;
     }
     if (postcopy_try_recover()) {
         return;
     }
     migration_incoming_process();
 }
 
 static bool migration_needs_multiple_sockets(void)
 {
     return migrate_use_multifd() || migrate_postcopy_preempt();
 }
 
 void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     Error *local_err = NULL;
     bool start_migration;
     QEMUFile *f;
 
     if (!mis->from_src_file) {
         /* The first connection (multifd may have multiple) */
         f = qemu_file_new_input(ioc);
 
         if (!migration_incoming_setup(f, errp)) {
             return;
         }
 
         /*
          * Common migration only needs one channel, so we can start
          * right now.  Some features need more than one channel, we wait.
          */
         start_migration = !migration_needs_multiple_sockets();
     } else {
         /* Multiple connections */
         assert(migration_needs_multiple_sockets());
         if (migrate_use_multifd()) {
             start_migration = multifd_recv_new_channel(ioc, &local_err);
         } else {
             assert(migrate_postcopy_preempt());
             f = qemu_file_new_input(ioc);
             start_migration = postcopy_preempt_new_channel(mis, f);
         }
         if (local_err) {
             error_propagate(errp, local_err);
             return;
         }
     }
 
     if (start_migration) {
         /* If it's a recovery, we're done */
         if (postcopy_try_recover()) {
             return;
         }
         migration_incoming_process();
     }
 }
 
 /**
  * @migration_has_all_channels: We have received all channels that we need
  *
  * Returns true when we have got connections to all the channels that
  * we need for migration.
  */
 bool migration_has_all_channels(void)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (!mis->from_src_file) {
         return false;
     }
 
     if (migrate_use_multifd()) {
         return multifd_recv_all_channels_created();
     }
 
     if (migrate_postcopy_preempt()) {
         return mis->postcopy_qemufile_dst != NULL;
     }
 
     return true;
 }
 
 /*
  * Send a 'SHUT' message on the return channel with the given value
  * to indicate that we've finished with the RP.  Non-0 value indicates
  * error.
  */
 void migrate_send_rp_shut(MigrationIncomingState *mis,
                           uint32_t value)
 {
     uint32_t buf;
 
     buf = cpu_to_be32(value);
     migrate_send_rp_message(mis, MIG_RP_MSG_SHUT, sizeof(buf), &buf);
 }
 
 /*
  * Send a 'PONG' message on the return channel with the given value
  * (normally in response to a 'PING')
  */
 void migrate_send_rp_pong(MigrationIncomingState *mis,
                           uint32_t value)
 {
     uint32_t buf;
 
     buf = cpu_to_be32(value);
     migrate_send_rp_message(mis, MIG_RP_MSG_PONG, sizeof(buf), &buf);
 }
 
 void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
                                  char *block_name)
 {
     char buf[512];
     int len;
     int64_t res;
 
     /*
      * First, we send the header part. It contains only the len of
      * idstr, and the idstr itself.
      */
     len = strlen(block_name);
     buf[0] = len;
     memcpy(buf + 1, block_name, len);
 
     if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
         error_report("%s: MSG_RP_RECV_BITMAP only used for recovery",
                      __func__);
         return;
     }
 
     migrate_send_rp_message(mis, MIG_RP_MSG_RECV_BITMAP, len + 1, buf);
 
     /*
      * Next, we dump the received bitmap to the stream.
      *
      * TODO: currently we are safe since we are the only one that is
      * using the to_src_file handle (fault thread is still paused),
      * and it's ok even not taking the mutex. However the best way is
      * to take the lock before sending the message header, and release
      * the lock after sending the bitmap.
      */
     qemu_mutex_lock(&mis->rp_mutex);
     res = ramblock_recv_bitmap_send(mis->to_src_file, block_name);
     qemu_mutex_unlock(&mis->rp_mutex);
 
     trace_migrate_send_rp_recv_bitmap(block_name, res);
 }
 
 void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value)
 {
     uint32_t buf;
 
     buf = cpu_to_be32(value);
     migrate_send_rp_message(mis, MIG_RP_MSG_RESUME_ACK, sizeof(buf), &buf);
 }
 
 MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
 {
     MigrationCapabilityStatusList *head = NULL, **tail = &head;
     MigrationCapabilityStatus *caps;
     MigrationState *s = migrate_get_current();
     int i;
 
     for (i = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
 #ifndef CONFIG_LIVE_BLOCK_MIGRATION
         if (i == MIGRATION_CAPABILITY_BLOCK) {
             continue;
         }
 #endif
         caps = g_malloc0(sizeof(*caps));
         caps->capability = i;
         caps->state = s->enabled_capabilities[i];
         QAPI_LIST_APPEND(tail, caps);
     }
 
     return head;
 }
 
 MigrationParameters *qmp_query_migrate_parameters(Error **errp)
 {
     MigrationParameters *params;
     MigrationState *s = migrate_get_current();
 
     /* TODO use QAPI_CLONE() instead of duplicating it inline */
     params = g_malloc0(sizeof(*params));
     params->has_compress_level = true;
     params->compress_level = s->parameters.compress_level;
     params->has_compress_threads = true;
     params->compress_threads = s->parameters.compress_threads;
     params->has_compress_wait_thread = true;
     params->compress_wait_thread = s->parameters.compress_wait_thread;
     params->has_decompress_threads = true;
     params->decompress_threads = s->parameters.decompress_threads;
     params->has_throttle_trigger_threshold = true;
     params->throttle_trigger_threshold = s->parameters.throttle_trigger_threshold;
     params->has_cpu_throttle_initial = true;
     params->cpu_throttle_initial = s->parameters.cpu_throttle_initial;
     params->has_cpu_throttle_increment = true;
     params->cpu_throttle_increment = s->parameters.cpu_throttle_increment;
     params->has_cpu_throttle_tailslow = true;
     params->cpu_throttle_tailslow = s->parameters.cpu_throttle_tailslow;
     params->has_tls_creds = true;
     params->tls_creds = g_strdup(s->parameters.tls_creds);
     params->has_tls_hostname = true;
     params->tls_hostname = g_strdup(s->parameters.tls_hostname);
     params->has_tls_authz = true;
     params->tls_authz = g_strdup(s->parameters.tls_authz ?
                                  s->parameters.tls_authz : "");
     params->has_max_bandwidth = true;
     params->max_bandwidth = s->parameters.max_bandwidth;
     params->has_downtime_limit = true;
     params->downtime_limit = s->parameters.downtime_limit;
     params->has_x_checkpoint_delay = true;
     params->x_checkpoint_delay = s->parameters.x_checkpoint_delay;
     params->has_block_incremental = true;
     params->block_incremental = s->parameters.block_incremental;
     params->has_multifd_channels = true;
     params->multifd_channels = s->parameters.multifd_channels;
     params->has_multifd_compression = true;
     params->multifd_compression = s->parameters.multifd_compression;
     params->has_multifd_zlib_level = true;
     params->multifd_zlib_level = s->parameters.multifd_zlib_level;
     params->has_multifd_zstd_level = true;
     params->multifd_zstd_level = s->parameters.multifd_zstd_level;
     params->has_xbzrle_cache_size = true;
     params->xbzrle_cache_size = s->parameters.xbzrle_cache_size;
     params->has_max_postcopy_bandwidth = true;
     params->max_postcopy_bandwidth = s->parameters.max_postcopy_bandwidth;
     params->has_max_cpu_throttle = true;
     params->max_cpu_throttle = s->parameters.max_cpu_throttle;
     params->has_announce_initial = true;
     params->announce_initial = s->parameters.announce_initial;
     params->has_announce_max = true;
     params->announce_max = s->parameters.announce_max;
     params->has_announce_rounds = true;
     params->announce_rounds = s->parameters.announce_rounds;
     params->has_announce_step = true;
     params->announce_step = s->parameters.announce_step;
 
     if (s->parameters.has_block_bitmap_mapping) {
         params->has_block_bitmap_mapping = true;
         params->block_bitmap_mapping =
             QAPI_CLONE(BitmapMigrationNodeAliasList,
                        s->parameters.block_bitmap_mapping);
     }
 
     return params;
 }
 
 AnnounceParameters *migrate_announce_params(void)
 {
     static AnnounceParameters ap;
 
     MigrationState *s = migrate_get_current();
 
     ap.initial = s->parameters.announce_initial;
     ap.max = s->parameters.announce_max;
     ap.rounds = s->parameters.announce_rounds;
     ap.step = s->parameters.announce_step;
 
     return &ap;
 }
 
 /*
  * Return true if we're already in the middle of a migration
  * (i.e. any of the active or setup states)
  */
 bool migration_is_setup_or_active(int state)
 {
     switch (state) {
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_PAUSED:
     case MIGRATION_STATUS_POSTCOPY_RECOVER:
     case MIGRATION_STATUS_SETUP:
     case MIGRATION_STATUS_PRE_SWITCHOVER:
     case MIGRATION_STATUS_DEVICE:
     case MIGRATION_STATUS_WAIT_UNPLUG:
     case MIGRATION_STATUS_COLO:
         return true;
 
     default:
         return false;
 
     }
 }
 
 bool migration_is_running(int state)
 {
     switch (state) {
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_PAUSED:
     case MIGRATION_STATUS_POSTCOPY_RECOVER:
     case MIGRATION_STATUS_SETUP:
     case MIGRATION_STATUS_PRE_SWITCHOVER:
     case MIGRATION_STATUS_DEVICE:
     case MIGRATION_STATUS_WAIT_UNPLUG:
     case MIGRATION_STATUS_CANCELLING:
         return true;
 
     default:
         return false;
 
     }
 }
 
 static void populate_time_info(MigrationInfo *info, MigrationState *s)
 {
     info->has_status = true;
     info->has_setup_time = true;
     info->setup_time = s->setup_time;
     if (s->state == MIGRATION_STATUS_COMPLETED) {
         info->has_total_time = true;
         info->total_time = s->total_time;
         info->has_downtime = true;
         info->downtime = s->downtime;
     } else {
         info->has_total_time = true;
         info->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) -
                            s->start_time;
         info->has_expected_downtime = true;
         info->expected_downtime = s->expected_downtime;
     }
 }
 
 static void populate_ram_info(MigrationInfo *info, MigrationState *s)
 {
     size_t page_size = qemu_target_page_size();
 
     info->has_ram = true;
     info->ram = g_malloc0(sizeof(*info->ram));
     info->ram->transferred = ram_counters.transferred;
     info->ram->total = ram_bytes_total();
     info->ram->duplicate = ram_counters.duplicate;
     /* legacy value.  It is not used anymore */
     info->ram->skipped = 0;
     info->ram->normal = ram_counters.normal;
     info->ram->normal_bytes = ram_counters.normal * page_size;
     info->ram->mbps = s->mbps;
     info->ram->dirty_sync_count = ram_counters.dirty_sync_count;
     info->ram->dirty_sync_missed_zero_copy =
             ram_counters.dirty_sync_missed_zero_copy;
     info->ram->postcopy_requests = ram_counters.postcopy_requests;
     info->ram->page_size = page_size;
     info->ram->multifd_bytes = ram_counters.multifd_bytes;
     info->ram->pages_per_second = s->pages_per_second;
     info->ram->precopy_bytes = ram_counters.precopy_bytes;
     info->ram->downtime_bytes = ram_counters.downtime_bytes;
     info->ram->postcopy_bytes = ram_counters.postcopy_bytes;
 
     if (migrate_use_xbzrle()) {
         info->has_xbzrle_cache = true;
         info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
         info->xbzrle_cache->cache_size = migrate_xbzrle_cache_size();
         info->xbzrle_cache->bytes = xbzrle_counters.bytes;
         info->xbzrle_cache->pages = xbzrle_counters.pages;
         info->xbzrle_cache->cache_miss = xbzrle_counters.cache_miss;
         info->xbzrle_cache->cache_miss_rate = xbzrle_counters.cache_miss_rate;
         info->xbzrle_cache->encoding_rate = xbzrle_counters.encoding_rate;
         info->xbzrle_cache->overflow = xbzrle_counters.overflow;
     }
 
     if (migrate_use_compression()) {
         info->has_compression = true;
         info->compression = g_malloc0(sizeof(*info->compression));
         info->compression->pages = compression_counters.pages;
         info->compression->busy = compression_counters.busy;
         info->compression->busy_rate = compression_counters.busy_rate;
         info->compression->compressed_size =
                                     compression_counters.compressed_size;
         info->compression->compression_rate =
                                     compression_counters.compression_rate;
     }
 
     if (cpu_throttle_active()) {
         info->has_cpu_throttle_percentage = true;
         info->cpu_throttle_percentage = cpu_throttle_get_percentage();
     }
 
     if (s->state != MIGRATION_STATUS_COMPLETED) {
         info->ram->remaining = ram_bytes_remaining();
         info->ram->dirty_pages_rate = ram_counters.dirty_pages_rate;
     }
 }
 
 static void populate_disk_info(MigrationInfo *info)
 {
     if (blk_mig_active()) {
         info->has_disk = true;
         info->disk = g_malloc0(sizeof(*info->disk));
         info->disk->transferred = blk_mig_bytes_transferred();
         info->disk->remaining = blk_mig_bytes_remaining();
         info->disk->total = blk_mig_bytes_total();
     }
 }
 
 static void fill_source_migration_info(MigrationInfo *info)
 {
     MigrationState *s = migrate_get_current();
     int state = qatomic_read(&s->state);
     GSList *cur_blocker = migration_blockers;
 
     info->blocked_reasons = NULL;
 
     /*
      * There are two types of reasons a migration might be blocked;
      * a) devices marked in VMState as non-migratable, and
      * b) Explicit migration blockers
      * We need to add both of them here.
      */
     qemu_savevm_non_migratable_list(&info->blocked_reasons);
 
     while (cur_blocker) {
         QAPI_LIST_PREPEND(info->blocked_reasons,
                           g_strdup(error_get_pretty(cur_blocker->data)));
         cur_blocker = g_slist_next(cur_blocker);
     }
     info->has_blocked_reasons = info->blocked_reasons != NULL;
 
     switch (state) {
     case MIGRATION_STATUS_NONE:
         /* no migration has happened ever */
         /* do not overwrite destination migration status */
         return;
     case MIGRATION_STATUS_SETUP:
         info->has_status = true;
         info->has_total_time = false;
         break;
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_CANCELLING:
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_PRE_SWITCHOVER:
     case MIGRATION_STATUS_DEVICE:
     case MIGRATION_STATUS_POSTCOPY_PAUSED:
     case MIGRATION_STATUS_POSTCOPY_RECOVER:
         /* TODO add some postcopy stats */
         populate_time_info(info, s);
         populate_ram_info(info, s);
         populate_disk_info(info);
         populate_vfio_info(info);
         break;
     case MIGRATION_STATUS_COLO:
         info->has_status = true;
         /* TODO: display COLO specific information (checkpoint info etc.) */
         break;
     case MIGRATION_STATUS_COMPLETED:
         populate_time_info(info, s);
         populate_ram_info(info, s);
         populate_vfio_info(info);
         break;
     case MIGRATION_STATUS_FAILED:
         info->has_status = true;
         if (s->error) {
             info->has_error_desc = true;
             info->error_desc = g_strdup(error_get_pretty(s->error));
         }
         break;
     case MIGRATION_STATUS_CANCELLED:
         info->has_status = true;
         break;
     case MIGRATION_STATUS_WAIT_UNPLUG:
         info->has_status = true;
         break;
     }
     info->status = state;
 }
 
 typedef enum WriteTrackingSupport {
     WT_SUPPORT_UNKNOWN = 0,
     WT_SUPPORT_ABSENT,
     WT_SUPPORT_AVAILABLE,
     WT_SUPPORT_COMPATIBLE
 } WriteTrackingSupport;
 
 static
 WriteTrackingSupport migrate_query_write_tracking(void)
 {
     /* Check if kernel supports required UFFD features */
     if (!ram_write_tracking_available()) {
         return WT_SUPPORT_ABSENT;
     }
     /*
      * Check if current memory configuration is
      * compatible with required UFFD features.
      */
     if (!ram_write_tracking_compatible()) {
         return WT_SUPPORT_AVAILABLE;
     }
 
     return WT_SUPPORT_COMPATIBLE;
 }
 
 /**
  * @migration_caps_check - check capability validity
  *
  * @cap_list: old capability list, array of bool
  * @params: new capabilities to be applied soon
  * @errp: set *errp if the check failed, with reason
  *
  * Returns true if check passed, otherwise false.
  */
 static bool migrate_caps_check(bool *cap_list,
                                MigrationCapabilityStatusList *params,
                                Error **errp)
 {
     MigrationCapabilityStatusList *cap;
     bool old_postcopy_cap;
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     old_postcopy_cap = cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM];
 
     for (cap = params; cap; cap = cap->next) {
         cap_list[cap->value->capability] = cap->value->state;
     }
 
 #ifndef CONFIG_LIVE_BLOCK_MIGRATION
     if (cap_list[MIGRATION_CAPABILITY_BLOCK]) {
         error_setg(errp, "QEMU compiled without old-style (blk/-b, inc/-i) "
                    "block migration");
         error_append_hint(errp, "Use drive_mirror+NBD instead.\n");
         return false;
     }
 #endif
 
 #ifndef CONFIG_REPLICATION
     if (cap_list[MIGRATION_CAPABILITY_X_COLO]) {
         error_setg(errp, "QEMU compiled without replication module"
                    " can't enable COLO");
         error_append_hint(errp, "Please enable replication before COLO.\n");
         return false;
     }
 #endif
 
     if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) {
         /* This check is reasonably expensive, so only when it's being
          * set the first time, also it's only the destination that needs
          * special support.
          */
         if (!old_postcopy_cap && runstate_check(RUN_STATE_INMIGRATE) &&
             !postcopy_ram_supported_by_host(mis)) {
             /* postcopy_ram_supported_by_host will have emitted a more
              * detailed message
              */
             error_setg(errp, "Postcopy is not supported");
             return false;
         }
 
         if (cap_list[MIGRATION_CAPABILITY_X_IGNORE_SHARED]) {
             error_setg(errp, "Postcopy is not compatible with ignore-shared");
             return false;
         }
     }
 
     if (cap_list[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT]) {
         WriteTrackingSupport wt_support;
         int idx;
         /*
          * Check if 'background-snapshot' capability is supported by
          * host kernel and compatible with guest memory configuration.
          */
         wt_support = migrate_query_write_tracking();
         if (wt_support < WT_SUPPORT_AVAILABLE) {
             error_setg(errp, "Background-snapshot is not supported by host kernel");
             return false;
         }
         if (wt_support < WT_SUPPORT_COMPATIBLE) {
             error_setg(errp, "Background-snapshot is not compatible "
                     "with guest memory configuration");
             return false;
         }
 
         /*
          * Check if there are any migration capabilities
          * incompatible with 'background-snapshot'.
          */
         for (idx = 0; idx < check_caps_background_snapshot.size; idx++) {
             int incomp_cap = check_caps_background_snapshot.caps[idx];
             if (cap_list[incomp_cap]) {
                 error_setg(errp,
                         "Background-snapshot is not compatible with %s",
                         MigrationCapability_str(incomp_cap));
                 return false;
             }
         }
     }
 
 #ifdef CONFIG_LINUX
     if (cap_list[MIGRATION_CAPABILITY_ZERO_COPY_SEND] &&
         (!cap_list[MIGRATION_CAPABILITY_MULTIFD] ||
          cap_list[MIGRATION_CAPABILITY_COMPRESS] ||
          cap_list[MIGRATION_CAPABILITY_XBZRLE] ||
          migrate_multifd_compression() ||
          migrate_use_tls())) {
         error_setg(errp,
                    "Zero copy only available for non-compressed non-TLS multifd migration");
         return false;
     }
 #else
     if (cap_list[MIGRATION_CAPABILITY_ZERO_COPY_SEND]) {
         error_setg(errp,
                    "Zero copy currently only available on Linux");
         return false;
     }
 #endif
 
 
     /* incoming side only */
     if (runstate_check(RUN_STATE_INMIGRATE) &&
         !migrate_multi_channels_is_allowed() &&
         cap_list[MIGRATION_CAPABILITY_MULTIFD]) {
         error_setg(errp, "multifd is not supported by current protocol");
         return false;
     }
 
     if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_PREEMPT]) {
         if (!cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) {
             error_setg(errp, "Postcopy preempt requires postcopy-ram");
             return false;
         }
 
         /*
          * Preempt mode requires urgent pages to be sent in separate
          * channel, OTOH compression logic will disorder all pages into
          * different compression channels, which is not compatible with the
          * preempt assumptions on channel assignments.
          */
         if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) {
             error_setg(errp, "Postcopy preempt not compatible with compress");
             return false;
         }
     }
 
     if (cap_list[MIGRATION_CAPABILITY_MULTIFD]) {
         if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) {
             error_setg(errp, "Multifd is not compatible with compress");
             return false;
         }
     }
 
     return true;
 }
 
 static void fill_destination_migration_info(MigrationInfo *info)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (mis->socket_address_list) {
         info->has_socket_address = true;
         info->socket_address =
             QAPI_CLONE(SocketAddressList, mis->socket_address_list);
     }
 
     switch (mis->state) {
     case MIGRATION_STATUS_NONE:
         return;
     case MIGRATION_STATUS_SETUP:
     case MIGRATION_STATUS_CANCELLING:
     case MIGRATION_STATUS_CANCELLED:
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_PAUSED:
     case MIGRATION_STATUS_POSTCOPY_RECOVER:
     case MIGRATION_STATUS_FAILED:
     case MIGRATION_STATUS_COLO:
         info->has_status = true;
         break;
     case MIGRATION_STATUS_COMPLETED:
         info->has_status = true;
         fill_destination_postcopy_migration_info(info);
         break;
     }
     info->status = mis->state;
 }
 
 MigrationInfo *qmp_query_migrate(Error **errp)
 {
     MigrationInfo *info = g_malloc0(sizeof(*info));
 
     fill_destination_migration_info(info);
     fill_source_migration_info(info);
 
     return info;
 }
 
 void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
                                   Error **errp)
 {
     MigrationState *s = migrate_get_current();
     MigrationCapabilityStatusList *cap;
     bool cap_list[MIGRATION_CAPABILITY__MAX];
 
     if (migration_is_running(s->state)) {
         error_setg(errp, QERR_MIGRATION_ACTIVE);
         return;
     }
 
     memcpy(cap_list, s->enabled_capabilities, sizeof(cap_list));
     if (!migrate_caps_check(cap_list, params, errp)) {
         return;
     }
 
     for (cap = params; cap; cap = cap->next) {
         s->enabled_capabilities[cap->value->capability] = cap->value->state;
     }
 }
 
 /*
  * Check whether the parameters are valid. Error will be put into errp
  * (if provided). Return true if valid, otherwise false.
  */
 static bool migrate_params_check(MigrationParameters *params, Error **errp)
 {
     if (params->has_compress_level &&
         (params->compress_level > 9)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "compress_level",
                    "a value between 0 and 9");
         return false;
     }
 
     if (params->has_compress_threads && (params->compress_threads < 1)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "compress_threads",
                    "a value between 1 and 255");
         return false;
     }
 
     if (params->has_decompress_threads && (params->decompress_threads < 1)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "decompress_threads",
                    "a value between 1 and 255");
         return false;
     }
 
     if (params->has_throttle_trigger_threshold &&
         (params->throttle_trigger_threshold < 1 ||
          params->throttle_trigger_threshold > 100)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "throttle_trigger_threshold",
                    "an integer in the range of 1 to 100");
         return false;
     }
 
     if (params->has_cpu_throttle_initial &&
         (params->cpu_throttle_initial < 1 ||
          params->cpu_throttle_initial > 99)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "cpu_throttle_initial",
                    "an integer in the range of 1 to 99");
         return false;
     }
 
     if (params->has_cpu_throttle_increment &&
         (params->cpu_throttle_increment < 1 ||
          params->cpu_throttle_increment > 99)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "cpu_throttle_increment",
                    "an integer in the range of 1 to 99");
         return false;
     }
 
     if (params->has_max_bandwidth && (params->max_bandwidth > SIZE_MAX)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "max_bandwidth",
                    "an integer in the range of 0 to "stringify(SIZE_MAX)
                    " bytes/second");
         return false;
     }
 
     if (params->has_downtime_limit &&
         (params->downtime_limit > MAX_MIGRATE_DOWNTIME)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "downtime_limit",
                    "an integer in the range of 0 to "
                     stringify(MAX_MIGRATE_DOWNTIME)" ms");
         return false;
     }
 
     /* x_checkpoint_delay is now always positive */
 
     if (params->has_multifd_channels && (params->multifd_channels < 1)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "multifd_channels",
                    "a value between 1 and 255");
         return false;
     }
 
     if (params->has_multifd_zlib_level &&
         (params->multifd_zlib_level > 9)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "multifd_zlib_level",
                    "a value between 0 and 9");
         return false;
     }
 
     if (params->has_multifd_zstd_level &&
         (params->multifd_zstd_level > 20)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "multifd_zstd_level",
                    "a value between 0 and 20");
         return false;
     }
 
     if (params->has_xbzrle_cache_size &&
         (params->xbzrle_cache_size < qemu_target_page_size() ||
          !is_power_of_2(params->xbzrle_cache_size))) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "xbzrle_cache_size",
                    "a power of two no less than the target page size");
         return false;
     }
 
     if (params->has_max_cpu_throttle &&
         (params->max_cpu_throttle < params->cpu_throttle_initial ||
          params->max_cpu_throttle > 99)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "max_cpu_throttle",
                    "an integer in the range of cpu_throttle_initial to 99");
         return false;
     }
 
     if (params->has_announce_initial &&
         params->announce_initial > 100000) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "announce_initial",
                    "a value between 0 and 100000");
         return false;
     }
     if (params->has_announce_max &&
         params->announce_max > 100000) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "announce_max",
                    "a value between 0 and 100000");
        return false;
     }
     if (params->has_announce_rounds &&
         params->announce_rounds > 1000) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "announce_rounds",
                    "a value between 0 and 1000");
        return false;
     }
     if (params->has_announce_step &&
         (params->announce_step < 1 ||
         params->announce_step > 10000)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                    "announce_step",
                    "a value between 0 and 10000");
        return false;
     }
 
     if (params->has_block_bitmap_mapping &&
         !check_dirty_bitmap_mig_alias_map(params->block_bitmap_mapping, errp)) {
         error_prepend(errp, "Invalid mapping given for block-bitmap-mapping: ");
         return false;
     }
 
 #ifdef CONFIG_LINUX
     if (migrate_use_zero_copy_send() &&
         ((params->has_multifd_compression && params->multifd_compression) ||
          (params->has_tls_creds && params->tls_creds && *params->tls_creds))) {
         error_setg(errp,
                    "Zero copy only available for non-compressed non-TLS multifd migration");
         return false;
     }
 #endif
 
     return true;
 }
 
 static void migrate_params_test_apply(MigrateSetParameters *params,
                                       MigrationParameters *dest)
 {
     *dest = migrate_get_current()->parameters;
 
     /* TODO use QAPI_CLONE() instead of duplicating it inline */
 
     if (params->has_compress_level) {
         dest->compress_level = params->compress_level;
     }
 
     if (params->has_compress_threads) {
         dest->compress_threads = params->compress_threads;
     }
 
     if (params->has_compress_wait_thread) {
         dest->compress_wait_thread = params->compress_wait_thread;
     }
 
     if (params->has_decompress_threads) {
         dest->decompress_threads = params->decompress_threads;
     }
 
     if (params->has_throttle_trigger_threshold) {
         dest->throttle_trigger_threshold = params->throttle_trigger_threshold;
     }
 
     if (params->has_cpu_throttle_initial) {
         dest->cpu_throttle_initial = params->cpu_throttle_initial;
     }
 
     if (params->has_cpu_throttle_increment) {
         dest->cpu_throttle_increment = params->cpu_throttle_increment;
     }
 
     if (params->has_cpu_throttle_tailslow) {
         dest->cpu_throttle_tailslow = params->cpu_throttle_tailslow;
     }
 
     if (params->has_tls_creds) {
         assert(params->tls_creds->type == QTYPE_QSTRING);
         dest->tls_creds = params->tls_creds->u.s;
     }
 
     if (params->has_tls_hostname) {
         assert(params->tls_hostname->type == QTYPE_QSTRING);
         dest->tls_hostname = params->tls_hostname->u.s;
     }
 
     if (params->has_max_bandwidth) {
         dest->max_bandwidth = params->max_bandwidth;
     }
 
     if (params->has_downtime_limit) {
         dest->downtime_limit = params->downtime_limit;
     }
 
     if (params->has_x_checkpoint_delay) {
         dest->x_checkpoint_delay = params->x_checkpoint_delay;
     }
 
     if (params->has_block_incremental) {
         dest->block_incremental = params->block_incremental;
     }
     if (params->has_multifd_channels) {
         dest->multifd_channels = params->multifd_channels;
     }
     if (params->has_multifd_compression) {
         dest->multifd_compression = params->multifd_compression;
     }
     if (params->has_xbzrle_cache_size) {
         dest->xbzrle_cache_size = params->xbzrle_cache_size;
     }
     if (params->has_max_postcopy_bandwidth) {
         dest->max_postcopy_bandwidth = params->max_postcopy_bandwidth;
     }
     if (params->has_max_cpu_throttle) {
         dest->max_cpu_throttle = params->max_cpu_throttle;
     }
     if (params->has_announce_initial) {
         dest->announce_initial = params->announce_initial;
     }
     if (params->has_announce_max) {
         dest->announce_max = params->announce_max;
     }
     if (params->has_announce_rounds) {
         dest->announce_rounds = params->announce_rounds;
     }
     if (params->has_announce_step) {
         dest->announce_step = params->announce_step;
     }
 
     if (params->has_block_bitmap_mapping) {
         dest->has_block_bitmap_mapping = true;
         dest->block_bitmap_mapping = params->block_bitmap_mapping;
     }
 }
 
 static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
 {
     MigrationState *s = migrate_get_current();
 
     /* TODO use QAPI_CLONE() instead of duplicating it inline */
 
     if (params->has_compress_level) {
         s->parameters.compress_level = params->compress_level;
     }
 
     if (params->has_compress_threads) {
         s->parameters.compress_threads = params->compress_threads;
     }
 
     if (params->has_compress_wait_thread) {
         s->parameters.compress_wait_thread = params->compress_wait_thread;
     }
 
     if (params->has_decompress_threads) {
         s->parameters.decompress_threads = params->decompress_threads;
     }
 
     if (params->has_throttle_trigger_threshold) {
         s->parameters.throttle_trigger_threshold = params->throttle_trigger_threshold;
     }
 
     if (params->has_cpu_throttle_initial) {
         s->parameters.cpu_throttle_initial = params->cpu_throttle_initial;
     }
 
     if (params->has_cpu_throttle_increment) {
         s->parameters.cpu_throttle_increment = params->cpu_throttle_increment;
     }
 
     if (params->has_cpu_throttle_tailslow) {
         s->parameters.cpu_throttle_tailslow = params->cpu_throttle_tailslow;
     }
 
     if (params->has_tls_creds) {
         g_free(s->parameters.tls_creds);
         assert(params->tls_creds->type == QTYPE_QSTRING);
         s->parameters.tls_creds = g_strdup(params->tls_creds->u.s);
     }
 
     if (params->has_tls_hostname) {
         g_free(s->parameters.tls_hostname);
         assert(params->tls_hostname->type == QTYPE_QSTRING);
         s->parameters.tls_hostname = g_strdup(params->tls_hostname->u.s);
     }
 
     if (params->has_tls_authz) {
         g_free(s->parameters.tls_authz);
         assert(params->tls_authz->type == QTYPE_QSTRING);
         s->parameters.tls_authz = g_strdup(params->tls_authz->u.s);
     }
 
     if (params->has_max_bandwidth) {
         s->parameters.max_bandwidth = params->max_bandwidth;
         if (s->to_dst_file && !migration_in_postcopy()) {
             qemu_file_set_rate_limit(s->to_dst_file,
                                 s->parameters.max_bandwidth / XFER_LIMIT_RATIO);
         }
     }
 
     if (params->has_downtime_limit) {
         s->parameters.downtime_limit = params->downtime_limit;
     }
 
     if (params->has_x_checkpoint_delay) {
         s->parameters.x_checkpoint_delay = params->x_checkpoint_delay;
         if (migration_in_colo_state()) {
             colo_checkpoint_notify(s);
         }
     }
 
     if (params->has_block_incremental) {
         s->parameters.block_incremental = params->block_incremental;
     }
     if (params->has_multifd_channels) {
         s->parameters.multifd_channels = params->multifd_channels;
     }
     if (params->has_multifd_compression) {
         s->parameters.multifd_compression = params->multifd_compression;
     }
     if (params->has_xbzrle_cache_size) {
         s->parameters.xbzrle_cache_size = params->xbzrle_cache_size;
         xbzrle_cache_resize(params->xbzrle_cache_size, errp);
     }
     if (params->has_max_postcopy_bandwidth) {
         s->parameters.max_postcopy_bandwidth = params->max_postcopy_bandwidth;
         if (s->to_dst_file && migration_in_postcopy()) {
             qemu_file_set_rate_limit(s->to_dst_file,
                     s->parameters.max_postcopy_bandwidth / XFER_LIMIT_RATIO);
         }
     }
     if (params->has_max_cpu_throttle) {
         s->parameters.max_cpu_throttle = params->max_cpu_throttle;
     }
     if (params->has_announce_initial) {
         s->parameters.announce_initial = params->announce_initial;
     }
     if (params->has_announce_max) {
         s->parameters.announce_max = params->announce_max;
     }
     if (params->has_announce_rounds) {
         s->parameters.announce_rounds = params->announce_rounds;
     }
     if (params->has_announce_step) {
         s->parameters.announce_step = params->announce_step;
     }
 
     if (params->has_block_bitmap_mapping) {
         qapi_free_BitmapMigrationNodeAliasList(
             s->parameters.block_bitmap_mapping);
 
         s->parameters.has_block_bitmap_mapping = true;
         s->parameters.block_bitmap_mapping =
             QAPI_CLONE(BitmapMigrationNodeAliasList,
                        params->block_bitmap_mapping);
     }
 }
 
 void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
 {
     MigrationParameters tmp;
 
     /* TODO Rewrite "" to null instead */
     if (params->has_tls_creds
         && params->tls_creds->type == QTYPE_QNULL) {
         qobject_unref(params->tls_creds->u.n);
         params->tls_creds->type = QTYPE_QSTRING;
         params->tls_creds->u.s = strdup("");
     }
     /* TODO Rewrite "" to null instead */
     if (params->has_tls_hostname
         && params->tls_hostname->type == QTYPE_QNULL) {
         qobject_unref(params->tls_hostname->u.n);
         params->tls_hostname->type = QTYPE_QSTRING;
         params->tls_hostname->u.s = strdup("");
     }
 
     migrate_params_test_apply(params, &tmp);
 
     if (!migrate_params_check(&tmp, errp)) {
         /* Invalid parameter */
         return;
     }
 
     migrate_params_apply(params, errp);
 }
 
 
 void qmp_migrate_start_postcopy(Error **errp)
 {
     MigrationState *s = migrate_get_current();
 
     if (!migrate_postcopy()) {
         error_setg(errp, "Enable postcopy with migrate_set_capability before"
                          " the start of migration");
         return;
     }
 
     if (s->state == MIGRATION_STATUS_NONE) {
         error_setg(errp, "Postcopy must be started after migration has been"
                          " started");
         return;
     }
     /*
      * we don't error if migration has finished since that would be racy
      * with issuing this command.
      */
     qatomic_set(&s->start_postcopy, true);
 }
 
 /* shared migration helpers */
 
 void migrate_set_state(int *state, int old_state, int new_state)
 {
     assert(new_state < MIGRATION_STATUS__MAX);
     if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
         trace_migrate_set_state(MigrationStatus_str(new_state));
         migrate_generate_event(new_state);
     }
 }
 
 static MigrationCapabilityStatus *migrate_cap_add(MigrationCapability index,
                                                   bool state)
 {
     MigrationCapabilityStatus *cap;
 
     cap = g_new0(MigrationCapabilityStatus, 1);
     cap->capability = index;
     cap->state = state;
 
     return cap;
 }
 
 void migrate_set_block_enabled(bool value, Error **errp)
 {
     MigrationCapabilityStatusList *cap = NULL;
 
     QAPI_LIST_PREPEND(cap, migrate_cap_add(MIGRATION_CAPABILITY_BLOCK, value));
     qmp_migrate_set_capabilities(cap, errp);
     qapi_free_MigrationCapabilityStatusList(cap);
 }
 
 static void migrate_set_block_incremental(MigrationState *s, bool value)
 {
     s->parameters.block_incremental = value;
 }
 
 static void block_cleanup_parameters(MigrationState *s)
 {
     if (s->must_remove_block_options) {
         /* setting to false can never fail */
         migrate_set_block_enabled(false, &error_abort);
         migrate_set_block_incremental(s, false);
         s->must_remove_block_options = false;
     }
 }
 
 static void migrate_fd_cleanup(MigrationState *s)
 {
     qemu_bh_delete(s->cleanup_bh);
     s->cleanup_bh = NULL;
 
     g_free(s->hostname);
     s->hostname = NULL;
 
     qemu_savevm_state_cleanup();
 
     if (s->to_dst_file) {
         QEMUFile *tmp;
 
         trace_migrate_fd_cleanup();
         qemu_mutex_unlock_iothread();
         if (s->migration_thread_running) {
             qemu_thread_join(&s->thread);
             s->migration_thread_running = false;
         }
         qemu_mutex_lock_iothread();
 
         multifd_save_cleanup();
         qemu_mutex_lock(&s->qemu_file_lock);
         tmp = s->to_dst_file;
         s->to_dst_file = NULL;
         qemu_mutex_unlock(&s->qemu_file_lock);
         /*
          * Close the file handle without the lock to make sure the
          * critical section won't block for long.
          */
         migration_ioc_unregister_yank_from_file(tmp);
         qemu_fclose(tmp);
     }
 
     if (s->postcopy_qemufile_src) {
         migration_ioc_unregister_yank_from_file(s->postcopy_qemufile_src);
         qemu_fclose(s->postcopy_qemufile_src);
         s->postcopy_qemufile_src = NULL;
     }
 
     assert(!migration_is_active(s));
 
     if (s->state == MIGRATION_STATUS_CANCELLING) {
         migrate_set_state(&s->state, MIGRATION_STATUS_CANCELLING,
                           MIGRATION_STATUS_CANCELLED);
     }
 
     if (s->error) {
         /* It is used on info migrate.  We can't free it */
         error_report_err(error_copy(s->error));
     }
     notifier_list_notify(&migration_state_notifiers, s);
     block_cleanup_parameters(s);
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
 
 static void migrate_fd_cleanup_schedule(MigrationState *s)
 {
     /*
      * Ref the state for bh, because it may be called when
      * there're already no other refs
      */
     object_ref(OBJECT(s));
     qemu_bh_schedule(s->cleanup_bh);
 }
 
 static void migrate_fd_cleanup_bh(void *opaque)
 {
     MigrationState *s = opaque;
     migrate_fd_cleanup(s);
     object_unref(OBJECT(s));
 }
 
 void migrate_set_error(MigrationState *s, const Error *error)
 {
     QEMU_LOCK_GUARD(&s->error_mutex);
     if (!s->error) {
         s->error = error_copy(error);
     }
 }
 
 static void migrate_error_free(MigrationState *s)
 {
     QEMU_LOCK_GUARD(&s->error_mutex);
     if (s->error) {
         error_free(s->error);
         s->error = NULL;
     }
 }
 
 void migrate_fd_error(MigrationState *s, const Error *error)
 {
     trace_migrate_fd_error(error_get_pretty(error));
     assert(s->to_dst_file == NULL);
     migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                       MIGRATION_STATUS_FAILED);
     migrate_set_error(s, error);
 }
 
 static void migrate_fd_cancel(MigrationState *s)
 {
     int old_state ;
     QEMUFile *f = migrate_get_current()->to_dst_file;
     trace_migrate_fd_cancel();
 
     WITH_QEMU_LOCK_GUARD(&s->qemu_file_lock) {
         if (s->rp_state.from_dst_file) {
             /* shutdown the rp socket, so causing the rp thread to shutdown */
             qemu_file_shutdown(s->rp_state.from_dst_file);
         }
     }
 
     do {
         old_state = s->state;
         if (!migration_is_running(old_state)) {
             break;
         }
         /* If the migration is paused, kick it out of the pause */
         if (old_state == MIGRATION_STATUS_PRE_SWITCHOVER) {
             qemu_sem_post(&s->pause_sem);
         }
         migrate_set_state(&s->state, old_state, MIGRATION_STATUS_CANCELLING);
     } while (s->state != MIGRATION_STATUS_CANCELLING);
 
     /*
      * If we're unlucky the migration code might be stuck somewhere in a
      * send/write while the network has failed and is waiting to timeout;
      * if we've got shutdown(2) available then we can force it to quit.
      * The outgoing qemu file gets closed in migrate_fd_cleanup that is
      * called in a bh, so there is no race against this cancel.
      */
     if (s->state == MIGRATION_STATUS_CANCELLING && f) {
         qemu_file_shutdown(f);
     }
     if (s->state == MIGRATION_STATUS_CANCELLING && s->block_inactive) {
         Error *local_err = NULL;
 
         bdrv_activate_all(&local_err);
         if (local_err) {
             error_report_err(local_err);
         } else {
             s->block_inactive = false;
         }
     }
 }
 
 void add_migration_state_change_notifier(Notifier *notify)
 {
     notifier_list_add(&migration_state_notifiers, notify);
 }
 
 void remove_migration_state_change_notifier(Notifier *notify)
 {
     notifier_remove(notify);
 }
 
 bool migration_in_setup(MigrationState *s)
 {
     return s->state == MIGRATION_STATUS_SETUP;
 }
 
 bool migration_has_finished(MigrationState *s)
 {
     return s->state == MIGRATION_STATUS_COMPLETED;
 }
 
 bool migration_has_failed(MigrationState *s)
 {
     return (s->state == MIGRATION_STATUS_CANCELLED ||
             s->state == MIGRATION_STATUS_FAILED);
 }
 
 bool migration_in_postcopy(void)
 {
     MigrationState *s = migrate_get_current();
 
     switch (s->state) {
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_PAUSED:
     case MIGRATION_STATUS_POSTCOPY_RECOVER:
         return true;
     default:
         return false;
     }
 }
 
 bool migration_in_postcopy_after_devices(MigrationState *s)
 {
     return migration_in_postcopy() && s->postcopy_after_devices;
 }
 
 bool migration_in_incoming_postcopy(void)
 {
     PostcopyState ps = postcopy_state_get();
 
     return ps >= POSTCOPY_INCOMING_DISCARD && ps < POSTCOPY_INCOMING_END;
 }
 
 bool migration_in_bg_snapshot(void)
 {
     MigrationState *s = migrate_get_current();
 
     return migrate_background_snapshot() &&
             migration_is_setup_or_active(s->state);
 }
 
 bool migration_is_idle(void)
 {
     MigrationState *s = current_migration;
 
     if (!s) {
         return true;
     }
 
     switch (s->state) {
     case MIGRATION_STATUS_NONE:
     case MIGRATION_STATUS_CANCELLED:
     case MIGRATION_STATUS_COMPLETED:
     case MIGRATION_STATUS_FAILED:
         return true;
     case MIGRATION_STATUS_SETUP:
     case MIGRATION_STATUS_CANCELLING:
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_POSTCOPY_ACTIVE:
     case MIGRATION_STATUS_COLO:
     case MIGRATION_STATUS_PRE_SWITCHOVER:
     case MIGRATION_STATUS_DEVICE:
     case MIGRATION_STATUS_WAIT_UNPLUG:
         return false;
     case MIGRATION_STATUS__MAX:
         g_assert_not_reached();
     }
 
     return false;
 }
 
 bool migration_is_active(MigrationState *s)
 {
     return (s->state == MIGRATION_STATUS_ACTIVE ||
             s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
 }
 
 void migrate_init(MigrationState *s)
 {
     /*
      * Reinitialise all migration state, except
      * parameters/capabilities that the user set, and
      * locks.
      */
     s->cleanup_bh = 0;
     s->vm_start_bh = 0;
     s->to_dst_file = NULL;
     s->state = MIGRATION_STATUS_NONE;
     s->rp_state.from_dst_file = NULL;
     s->rp_state.error = false;
     s->mbps = 0.0;
     s->pages_per_second = 0.0;
     s->downtime = 0;
     s->expected_downtime = 0;
     s->setup_time = 0;
     s->start_postcopy = false;
     s->postcopy_after_devices = false;
     s->migration_thread_running = false;
     error_free(s->error);
     s->error = NULL;
     s->hostname = NULL;
 
     migrate_set_state(&s->state, MIGRATION_STATUS_NONE, MIGRATION_STATUS_SETUP);
 
     s->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     s->total_time = 0;
     s->vm_was_running = false;
     s->iteration_initial_bytes = 0;
     s->threshold_size = 0;
 }
 
 int migrate_add_blocker_internal(Error *reason, Error **errp)
 {
     /* Snapshots are similar to migrations, so check RUN_STATE_SAVE_VM too. */
     if (runstate_check(RUN_STATE_SAVE_VM) || !migration_is_idle()) {
         error_propagate_prepend(errp, error_copy(reason),
                                 "disallowing migration blocker "
                                 "(migration/snapshot in progress) for: ");
         return -EBUSY;
     }
 
     migration_blockers = g_slist_prepend(migration_blockers, reason);
     return 0;
 }
 
 int migrate_add_blocker(Error *reason, Error **errp)
 {
     if (only_migratable) {
         error_propagate_prepend(errp, error_copy(reason),
                                 "disallowing migration blocker "
                                 "(--only-migratable) for: ");
         return -EACCES;
     }
 
     return migrate_add_blocker_internal(reason, errp);
 }
 
 void migrate_del_blocker(Error *reason)
 {
     migration_blockers = g_slist_remove(migration_blockers, reason);
 }
 
 void qmp_migrate_incoming(const char *uri, Error **errp)
 {
     Error *local_err = NULL;
     static bool once = true;
 
     if (!once) {
         error_setg(errp, "The incoming migration has already been started");
         return;
     }
     if (!runstate_check(RUN_STATE_INMIGRATE)) {
         error_setg(errp, "'-incoming' was not specified on the command line");
         return;
     }
 
     if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
         return;
     }
 
     qemu_start_incoming_migration(uri, &local_err);
 
     if (local_err) {
         yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         error_propagate(errp, local_err);
         return;
     }
 
     once = false;
 }
 
 void qmp_migrate_recover(const char *uri, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
     /*
      * Don't even bother to use ERRP_GUARD() as it _must_ always be set by
      * callers (no one should ignore a recover failure); if there is, it's a
      * programming error.
      */
     assert(errp);
 
     if (mis->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
         error_setg(errp, "Migrate recover can only be run "
                    "when postcopy is paused.");
         return;
     }
 
     /* If there's an existing transport, release it */
     migration_incoming_transport_cleanup(mis);
 
     /*
      * Note that this call will never start a real migration; it will
      * only re-setup the migration stream and poke existing migration
      * to continue using that newly established channel.
      */
     qemu_start_incoming_migration(uri, errp);
 }
 
 void qmp_migrate_pause(Error **errp)
 {
     MigrationState *ms = migrate_get_current();
     MigrationIncomingState *mis = migration_incoming_get_current();
     int ret;
 
     if (ms->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         /* Source side, during postcopy */
         qemu_mutex_lock(&ms->qemu_file_lock);
         ret = qemu_file_shutdown(ms->to_dst_file);
         qemu_mutex_unlock(&ms->qemu_file_lock);
         if (ret) {
             error_setg(errp, "Failed to pause source migration");
         }
         return;
     }
 
     if (mis->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         ret = qemu_file_shutdown(mis->from_src_file);
         if (ret) {
             error_setg(errp, "Failed to pause destination migration");
         }
         return;
     }
 
     error_setg(errp, "migrate-pause is currently only supported "
                "during postcopy-active state");
 }
 
 bool migration_is_blocked(Error **errp)
 {
     if (qemu_savevm_state_blocked(errp)) {
         return true;
     }
 
     if (migration_blockers) {
         error_propagate(errp, error_copy(migration_blockers->data));
         return true;
     }
 
     return false;
 }
 
 /* Returns true if continue to migrate, or false if error detected */
 static bool migrate_prepare(MigrationState *s, bool blk, bool blk_inc,
                             bool resume, Error **errp)
 {
     Error *local_err = NULL;
 
     if (resume) {
         if (s->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
             error_setg(errp, "Cannot resume if there is no "
                        "paused migration");
             return false;
         }
 
         /*
          * Postcopy recovery won't work well with release-ram
          * capability since release-ram will drop the page buffer as
          * long as the page is put into the send buffer.  So if there
          * is a network failure happened, any page buffers that have
          * not yet reached the destination VM but have already been
          * sent from the source VM will be lost forever.  Let's refuse
          * the client from resuming such a postcopy migration.
          * Luckily release-ram was designed to only be used when src
          * and destination VMs are on the same host, so it should be
          * fine.
          */
         if (migrate_release_ram()) {
             error_setg(errp, "Postcopy recovery cannot work "
                        "when release-ram capability is set");
             return false;
         }
 
         /* This is a resume, skip init status */
         return true;
     }
 
     if (migration_is_running(s->state)) {
         error_setg(errp, QERR_MIGRATION_ACTIVE);
         return false;
     }
 
     if (runstate_check(RUN_STATE_INMIGRATE)) {
         error_setg(errp, "Guest is waiting for an incoming migration");
         return false;
     }
 
     if (runstate_check(RUN_STATE_POSTMIGRATE)) {
         error_setg(errp, "Can't migrate the vm that was paused due to "
                    "previous migration");
         return false;
     }
 
     if (migration_is_blocked(errp)) {
         return false;
     }
 
     if (blk || blk_inc) {
         if (migrate_colo_enabled()) {
             error_setg(errp, "No disk migration is required in COLO mode");
             return false;
         }
         if (migrate_use_block() || migrate_use_block_incremental()) {
             error_setg(errp, "Command options are incompatible with "
                        "current migration capabilities");
             return false;
         }
         migrate_set_block_enabled(true, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             return false;
         }
         s->must_remove_block_options = true;
     }
 
     if (blk_inc) {
         migrate_set_block_incremental(s, true);
     }
 
     migrate_init(s);
     /*
      * set ram_counters compression_counters memory to zero for a
      * new migration
      */
     memset(&ram_counters, 0, sizeof(ram_counters));
     memset(&compression_counters, 0, sizeof(compression_counters));
 
     return true;
 }
 
 void qmp_migrate(const char *uri, bool has_blk, bool blk,
                  bool has_inc, bool inc, bool has_detach, bool detach,
                  bool has_resume, bool resume, Error **errp)
 {
     Error *local_err = NULL;
     MigrationState *s = migrate_get_current();
     const char *p = NULL;
 
     if (!migrate_prepare(s, has_blk && blk, has_inc && inc,
                          has_resume && resume, errp)) {
         /* Error detected, put into errp */
         return;
     }
 
     if (!(has_resume && resume)) {
         if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
             return;
         }
     }
 
     migrate_protocol_allow_multi_channels(false);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
         migrate_protocol_allow_multi_channels(true);
         socket_start_outgoing_migration(s, p ? p : uri, &local_err);
 #ifdef CONFIG_RDMA
     } else if (strstart(uri, "rdma:", &p)) {
         rdma_start_outgoing_migration(s, p, &local_err);
 #endif
     } else if (strstart(uri, "exec:", &p)) {
         exec_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_outgoing_migration(s, p, &local_err);
     } else {
         if (!(has_resume && resume)) {
             yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         }
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "uri",
                    "a valid migration protocol");
         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                           MIGRATION_STATUS_FAILED);
         block_cleanup_parameters(s);
         return;
     }
 
     if (local_err) {
         if (!(has_resume && resume)) {
             yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         }
         migrate_fd_error(s, local_err);
         error_propagate(errp, local_err);
         return;
     }
 }
 
 void qmp_migrate_cancel(Error **errp)
 {
     migration_cancel(NULL);
 }
 
 void qmp_migrate_continue(MigrationStatus state, Error **errp)
 {
     MigrationState *s = migrate_get_current();
     if (s->state != state) {
         error_setg(errp,  "Migration not in expected state: %s",
                    MigrationStatus_str(s->state));
         return;
     }
     qemu_sem_post(&s->pause_sem);
 }
 
 bool migrate_release_ram(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_RELEASE_RAM];
 }
 
 bool migrate_postcopy_ram(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_RAM];
 }
 
 bool migrate_postcopy(void)
 {
     return migrate_postcopy_ram() || migrate_dirty_bitmaps();
 }
 
 bool migrate_auto_converge(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_AUTO_CONVERGE];
 }
 
 bool migrate_zero_blocks(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_ZERO_BLOCKS];
 }
 
 bool migrate_postcopy_blocktime(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_BLOCKTIME];
 }
 
 bool migrate_use_compression(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_COMPRESS];
 }
 
 int migrate_compress_level(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.compress_level;
 }
 
 int migrate_compress_threads(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.compress_threads;
 }
 
 int migrate_compress_wait_thread(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.compress_wait_thread;
 }
 
 int migrate_decompress_threads(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.decompress_threads;
 }
 
 bool migrate_dirty_bitmaps(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_BITMAPS];
 }
 
 bool migrate_ignore_shared(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_X_IGNORE_SHARED];
 }
 
 bool migrate_validate_uuid(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_VALIDATE_UUID];
 }
 
 bool migrate_use_events(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_EVENTS];
 }
 
 bool migrate_use_multifd(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_MULTIFD];
 }
 
 bool migrate_pause_before_switchover(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[
         MIGRATION_CAPABILITY_PAUSE_BEFORE_SWITCHOVER];
 }
 
 int migrate_multifd_channels(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.multifd_channels;
 }
 
 MultiFDCompression migrate_multifd_compression(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     assert(s->parameters.multifd_compression < MULTIFD_COMPRESSION__MAX);
     return s->parameters.multifd_compression;
 }
 
 int migrate_multifd_zlib_level(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.multifd_zlib_level;
 }
 
 int migrate_multifd_zstd_level(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.multifd_zstd_level;
 }
 
 #ifdef CONFIG_LINUX
 bool migrate_use_zero_copy_send(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_ZERO_COPY_SEND];
 }
 #endif
 
 int migrate_use_tls(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.tls_creds && *s->parameters.tls_creds;
 }
 
 int migrate_use_xbzrle(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
 }
 
 uint64_t migrate_xbzrle_cache_size(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.xbzrle_cache_size;
 }
 
 static int64_t migrate_max_postcopy_bandwidth(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.max_postcopy_bandwidth;
 }
 
 bool migrate_use_block(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_BLOCK];
 }
 
 bool migrate_use_return_path(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_RETURN_PATH];
 }
 
 bool migrate_use_block_incremental(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->parameters.block_incremental;
 }
 
 bool migrate_background_snapshot(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT];
 }
 
 bool migrate_postcopy_preempt(void)
 {
     MigrationState *s;
 
     s = migrate_get_current();
 
     return s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_PREEMPT];
 }
 
 /* migration thread support */
 /*
  * Something bad happened to the RP stream, mark an error
  * The caller shall print or trace something to indicate why
  */
 static void mark_source_rp_bad(MigrationState *s)
 {
     s->rp_state.error = true;
 }
 
 static struct rp_cmd_args {
     ssize_t     len; /* -1 = variable */
     const char *name;
 } rp_cmd_args[] = {
     [MIG_RP_MSG_INVALID]        = { .len = -1, .name = "INVALID" },
     [MIG_RP_MSG_SHUT]           = { .len =  4, .name = "SHUT" },
     [MIG_RP_MSG_PONG]           = { .len =  4, .name = "PONG" },
     [MIG_RP_MSG_REQ_PAGES]      = { .len = 12, .name = "REQ_PAGES" },
     [MIG_RP_MSG_REQ_PAGES_ID]   = { .len = -1, .name = "REQ_PAGES_ID" },
     [MIG_RP_MSG_RECV_BITMAP]    = { .len = -1, .name = "RECV_BITMAP" },
     [MIG_RP_MSG_RESUME_ACK]     = { .len =  4, .name = "RESUME_ACK" },
     [MIG_RP_MSG_MAX]            = { .len = -1, .name = "MAX" },
 };
 
 /*
  * Process a request for pages received on the return path,
  * We're allowed to send more than requested (e.g. to round to our page size)
  * and we don't need to send pages that have already been sent.
  */
 static void migrate_handle_rp_req_pages(MigrationState *ms, const char* rbname,
                                        ram_addr_t start, size_t len)
 {
     long our_host_ps = qemu_real_host_page_size();
 
     trace_migrate_handle_rp_req_pages(rbname, start, len);
 
     /*
      * Since we currently insist on matching page sizes, just sanity check
      * we're being asked for whole host pages.
      */
     if (!QEMU_IS_ALIGNED(start, our_host_ps) ||
         !QEMU_IS_ALIGNED(len, our_host_ps)) {
         error_report("%s: Misaligned page request, start: " RAM_ADDR_FMT
                      " len: %zd", __func__, start, len);
         mark_source_rp_bad(ms);
         return;
     }
 
     if (ram_save_queue_pages(rbname, start, len)) {
         mark_source_rp_bad(ms);
     }
 }
 
 /* Return true to retry, false to quit */
 static bool postcopy_pause_return_path_thread(MigrationState *s)
 {
     trace_postcopy_pause_return_path();
 
     qemu_sem_wait(&s->postcopy_pause_rp_sem);
 
     trace_postcopy_pause_return_path_continued();
 
     return true;
 }
 
 static int migrate_handle_rp_recv_bitmap(MigrationState *s, char *block_name)
 {
     RAMBlock *block = qemu_ram_block_by_name(block_name);
 
     if (!block) {
         error_report("%s: invalid block name '%s'", __func__, block_name);
         return -EINVAL;
     }
 
     /* Fetch the received bitmap and refresh the dirty bitmap */
     return ram_dirty_bitmap_reload(s, block);
 }
 
 static int migrate_handle_rp_resume_ack(MigrationState *s, uint32_t value)
 {
     trace_source_return_path_thread_resume_ack(value);
 
     if (value != MIGRATION_RESUME_ACK_VALUE) {
         error_report("%s: illegal resume_ack value %"PRIu32,
                      __func__, value);
         return -1;
     }
 
     /* Now both sides are active. */
     migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_RECOVER,
                       MIGRATION_STATUS_POSTCOPY_ACTIVE);
 
     /* Notify send thread that time to continue send pages */
     qemu_sem_post(&s->rp_state.rp_sem);
 
     return 0;
 }
 
 /* Release ms->rp_state.from_dst_file in a safe way */
 static void migration_release_from_dst_file(MigrationState *ms)
 {
     QEMUFile *file;
 
     WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
         /*
          * Reset the from_dst_file pointer first before releasing it, as we
          * can't block within lock section
          */
         file = ms->rp_state.from_dst_file;
         ms->rp_state.from_dst_file = NULL;
     }
 
     qemu_fclose(file);
 }
 
 /*
  * Handles messages sent on the return path towards the source VM
  *
  */
 static void *source_return_path_thread(void *opaque)
 {
     MigrationState *ms = opaque;
     QEMUFile *rp = ms->rp_state.from_dst_file;
     uint16_t header_len, header_type;
     uint8_t buf[512];
     uint32_t tmp32, sibling_error;
     ram_addr_t start = 0; /* =0 to silence warning */
     size_t  len = 0, expected_len;
     int res;
 
     trace_source_return_path_thread_entry();
     rcu_register_thread();
 
 retry:
     while (!ms->rp_state.error && !qemu_file_get_error(rp) &&
            migration_is_setup_or_active(ms->state)) {
         trace_source_return_path_thread_loop_top();
         header_type = qemu_get_be16(rp);
         header_len = qemu_get_be16(rp);
 
         if (qemu_file_get_error(rp)) {
             mark_source_rp_bad(ms);
             goto out;
         }
 
         if (header_type >= MIG_RP_MSG_MAX ||
             header_type == MIG_RP_MSG_INVALID) {
             error_report("RP: Received invalid message 0x%04x length 0x%04x",
                          header_type, header_len);
             mark_source_rp_bad(ms);
             goto out;
         }
 
         if ((rp_cmd_args[header_type].len != -1 &&
             header_len != rp_cmd_args[header_type].len) ||
             header_len > sizeof(buf)) {
             error_report("RP: Received '%s' message (0x%04x) with"
                          "incorrect length %d expecting %zu",
                          rp_cmd_args[header_type].name, header_type, header_len,
                          (size_t)rp_cmd_args[header_type].len);
             mark_source_rp_bad(ms);
             goto out;
         }
 
         /* We know we've got a valid header by this point */
         res = qemu_get_buffer(rp, buf, header_len);
         if (res != header_len) {
             error_report("RP: Failed reading data for message 0x%04x"
                          " read %d expected %d",
                          header_type, res, header_len);
             mark_source_rp_bad(ms);
             goto out;
         }
 
         /* OK, we have the message and the data */
         switch (header_type) {
         case MIG_RP_MSG_SHUT:
             sibling_error = ldl_be_p(buf);
             trace_source_return_path_thread_shut(sibling_error);
             if (sibling_error) {
                 error_report("RP: Sibling indicated error %d", sibling_error);
                 mark_source_rp_bad(ms);
             }
             /*
              * We'll let the main thread deal with closing the RP
              * we could do a shutdown(2) on it, but we're the only user
              * anyway, so there's nothing gained.
              */
             goto out;
 
         case MIG_RP_MSG_PONG:
             tmp32 = ldl_be_p(buf);
             trace_source_return_path_thread_pong(tmp32);
             break;
 
         case MIG_RP_MSG_REQ_PAGES:
             start = ldq_be_p(buf);
             len = ldl_be_p(buf + 8);
             migrate_handle_rp_req_pages(ms, NULL, start, len);
             break;
 
         case MIG_RP_MSG_REQ_PAGES_ID:
             expected_len = 12 + 1; /* header + termination */
 
             if (header_len >= expected_len) {
                 start = ldq_be_p(buf);
                 len = ldl_be_p(buf + 8);
                 /* Now we expect an idstr */
                 tmp32 = buf[12]; /* Length of the following idstr */
                 buf[13 + tmp32] = '\0';
                 expected_len += tmp32;
             }
             if (header_len != expected_len) {
                 error_report("RP: Req_Page_id with length %d expecting %zd",
                              header_len, expected_len);
                 mark_source_rp_bad(ms);
                 goto out;
             }
             migrate_handle_rp_req_pages(ms, (char *)&buf[13], start, len);
             break;
 
         case MIG_RP_MSG_RECV_BITMAP:
             if (header_len < 1) {
                 error_report("%s: missing block name", __func__);
                 mark_source_rp_bad(ms);
                 goto out;
             }
             /* Format: len (1B) + idstr (<255B). This ends the idstr. */
             buf[buf[0] + 1] = '\0';
             if (migrate_handle_rp_recv_bitmap(ms, (char *)(buf + 1))) {
                 mark_source_rp_bad(ms);
                 goto out;
             }
             break;
 
         case MIG_RP_MSG_RESUME_ACK:
             tmp32 = ldl_be_p(buf);
             if (migrate_handle_rp_resume_ack(ms, tmp32)) {
                 mark_source_rp_bad(ms);
                 goto out;
             }
             break;
 
         default:
             break;
         }
     }
 
 out:
     res = qemu_file_get_error(rp);
     if (res) {
         if (res && migration_in_postcopy()) {
             /*
              * Maybe there is something we can do: it looks like a
              * network down issue, and we pause for a recovery.
              */
             migration_release_from_dst_file(ms);
             rp = NULL;
             if (postcopy_pause_return_path_thread(ms)) {
                 /*
                  * Reload rp, reset the rest.  Referencing it is safe since
                  * it's reset only by us above, or when migration completes
                  */
                 rp = ms->rp_state.from_dst_file;
                 ms->rp_state.error = false;
                 goto retry;
             }
         }
 
         trace_source_return_path_thread_bad_end();
         mark_source_rp_bad(ms);
     }
 
     trace_source_return_path_thread_end();
     migration_release_from_dst_file(ms);
     rcu_unregister_thread();
     return NULL;
 }
 
 static int open_return_path_on_source(MigrationState *ms,
                                       bool create_thread)
 {
     ms->rp_state.from_dst_file = qemu_file_get_return_path(ms->to_dst_file);
     if (!ms->rp_state.from_dst_file) {
         return -1;
     }
 
     trace_open_return_path_on_source();
 
     if (!create_thread) {
         /* We're done */
         return 0;
     }
 
     qemu_thread_create(&ms->rp_state.rp_thread, "return path",
                        source_return_path_thread, ms, QEMU_THREAD_JOINABLE);
     ms->rp_state.rp_thread_created = true;
 
     trace_open_return_path_on_source_continue();
 
     return 0;
 }
 
 /* Returns 0 if the RP was ok, otherwise there was an error on the RP */
 static int await_return_path_close_on_source(MigrationState *ms)
 {
     /*
      * If this is a normal exit then the destination will send a SHUT and the
      * rp_thread will exit, however if there's an error we need to cause
      * it to exit.
      */
     if (qemu_file_get_error(ms->to_dst_file) && ms->rp_state.from_dst_file) {
         /*
          * shutdown(2), if we have it, will cause it to unblock if it's stuck
          * waiting for the destination.
          */
         qemu_file_shutdown(ms->rp_state.from_dst_file);
         mark_source_rp_bad(ms);
     }
     trace_await_return_path_close_on_source_joining();
     qemu_thread_join(&ms->rp_state.rp_thread);
     ms->rp_state.rp_thread_created = false;
     trace_await_return_path_close_on_source_close();
     return ms->rp_state.error;
 }
 
 /*
  * Switch from normal iteration to postcopy
  * Returns non-0 on error
  */
 static int postcopy_start(MigrationState *ms)
 {
     int ret;
     QIOChannelBuffer *bioc;
     QEMUFile *fb;
     int64_t time_at_stop = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     int64_t bandwidth = migrate_max_postcopy_bandwidth();
     bool restart_block = false;
     int cur_state = MIGRATION_STATUS_ACTIVE;
 
     if (postcopy_preempt_wait_channel(ms)) {
         migrate_set_state(&ms->state, ms->state, MIGRATION_STATUS_FAILED);
         return -1;
     }
 
     if (!migrate_pause_before_switchover()) {
         migrate_set_state(&ms->state, MIGRATION_STATUS_ACTIVE,
                           MIGRATION_STATUS_POSTCOPY_ACTIVE);
     }
 
     trace_postcopy_start();
     qemu_mutex_lock_iothread();
     trace_postcopy_start_set_run();
 
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
     global_state_store();
     ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
     if (ret < 0) {
         goto fail;
     }
 
     ret = migration_maybe_pause(ms, &cur_state,
                                 MIGRATION_STATUS_POSTCOPY_ACTIVE);
     if (ret < 0) {
         goto fail;
     }
 
     ret = bdrv_inactivate_all();
     if (ret < 0) {
         goto fail;
     }
     restart_block = true;
 
     /*
      * Cause any non-postcopiable, but iterative devices to
      * send out their final data.
      */
     qemu_savevm_state_complete_precopy(ms->to_dst_file, true, false);
 
     /*
      * in Finish migrate and with the io-lock held everything should
      * be quiet, but we've potentially still got dirty pages and we
      * need to tell the destination to throw any pages it's already received
      * that are dirty
      */
     if (migrate_postcopy_ram()) {
         ram_postcopy_send_discard_bitmap(ms);
     }
 
     /*
      * send rest of state - note things that are doing postcopy
      * will notice we're in POSTCOPY_ACTIVE and not actually
      * wrap their state up here
      */
     /* 0 max-postcopy-bandwidth means unlimited */
     if (!bandwidth) {
         qemu_file_set_rate_limit(ms->to_dst_file, INT64_MAX);
     } else {
         qemu_file_set_rate_limit(ms->to_dst_file, bandwidth / XFER_LIMIT_RATIO);
     }
     if (migrate_postcopy_ram()) {
         /* Ping just for debugging, helps line traces up */
         qemu_savevm_send_ping(ms->to_dst_file, 2);
     }
 
     /*
      * While loading the device state we may trigger page transfer
      * requests and the fd must be free to process those, and thus
      * the destination must read the whole device state off the fd before
      * it starts processing it.  Unfortunately the ad-hoc migration format
      * doesn't allow the destination to know the size to read without fully
      * parsing it through each devices load-state code (especially the open
      * coded devices that use get/put).
      * So we wrap the device state up in a package with a length at the start;
      * to do this we use a qemu_buf to hold the whole of the device state.
      */
     bioc = qio_channel_buffer_new(4096);
     qio_channel_set_name(QIO_CHANNEL(bioc), "migration-postcopy-buffer");
     fb = qemu_file_new_output(QIO_CHANNEL(bioc));
     object_unref(OBJECT(bioc));
 
     /*
      * Make sure the receiver can get incoming pages before we send the rest
      * of the state
      */
     qemu_savevm_send_postcopy_listen(fb);
 
     qemu_savevm_state_complete_precopy(fb, false, false);
     if (migrate_postcopy_ram()) {
         qemu_savevm_send_ping(fb, 3);
     }
 
     qemu_savevm_send_postcopy_run(fb);
 
     /* <><> end of stuff going into the package */
 
     /* Last point of recovery; as soon as we send the package the destination
      * can open devices and potentially start running.
      * Lets just check again we've not got any errors.
      */
     ret = qemu_file_get_error(ms->to_dst_file);
     if (ret) {
         error_report("postcopy_start: Migration stream errored (pre package)");
         goto fail_closefb;
     }
 
     restart_block = false;
 
     /* Now send that blob */
     if (qemu_savevm_send_packaged(ms->to_dst_file, bioc->data, bioc->usage)) {
         goto fail_closefb;
     }
     qemu_fclose(fb);
 
     /* Send a notify to give a chance for anything that needs to happen
      * at the transition to postcopy and after the device state; in particular
      * spice needs to trigger a transition now
      */
     ms->postcopy_after_devices = true;
     notifier_list_notify(&migration_state_notifiers, ms);
 
     ms->downtime =  qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - time_at_stop;
 
     qemu_mutex_unlock_iothread();
 
     if (migrate_postcopy_ram()) {
         /*
          * Although this ping is just for debug, it could potentially be
          * used for getting a better measurement of downtime at the source.
          */
         qemu_savevm_send_ping(ms->to_dst_file, 4);
     }
 
     if (migrate_release_ram()) {
         ram_postcopy_migrated_memory_release(ms);
     }
 
     ret = qemu_file_get_error(ms->to_dst_file);
     if (ret) {
         error_report("postcopy_start: Migration stream errored");
         migrate_set_state(&ms->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
                               MIGRATION_STATUS_FAILED);
     }
 
     trace_postcopy_preempt_enabled(migrate_postcopy_preempt());
 
     return ret;
 
 fail_closefb:
     qemu_fclose(fb);
 fail:
     migrate_set_state(&ms->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
                           MIGRATION_STATUS_FAILED);
     if (restart_block) {
         /* A failure happened early enough that we know the destination hasn't
          * accessed block devices, so we're safe to recover.
          */
         Error *local_err = NULL;
 
         bdrv_activate_all(&local_err);
         if (local_err) {
             error_report_err(local_err);
         }
     }
     qemu_mutex_unlock_iothread();
     return -1;
 }
 
 /**
  * migration_maybe_pause: Pause if required to by
  * migrate_pause_before_switchover called with the iothread locked
  * Returns: 0 on success
  */
 static int migration_maybe_pause(MigrationState *s,
                                  int *current_active_state,
                                  int new_state)
 {
     if (!migrate_pause_before_switchover()) {
         return 0;
     }
 
     /* Since leaving this state is not atomic with posting the semaphore
      * it's possible that someone could have issued multiple migrate_continue
      * and the semaphore is incorrectly positive at this point;
      * the docs say it's undefined to reinit a semaphore that's already
      * init'd, so use timedwait to eat up any existing posts.
      */
     while (qemu_sem_timedwait(&s->pause_sem, 1) == 0) {
         /* This block intentionally left blank */
     }
 
     /*
      * If the migration is cancelled when it is in the completion phase,
      * the migration state is set to MIGRATION_STATUS_CANCELLING.
      * So we don't need to wait a semaphore, otherwise we would always
      * wait for the 'pause_sem' semaphore.
      */
     if (s->state != MIGRATION_STATUS_CANCELLING) {
         qemu_mutex_unlock_iothread();
         migrate_set_state(&s->state, *current_active_state,
                           MIGRATION_STATUS_PRE_SWITCHOVER);
         qemu_sem_wait(&s->pause_sem);
         migrate_set_state(&s->state, MIGRATION_STATUS_PRE_SWITCHOVER,
                           new_state);
         *current_active_state = new_state;
         qemu_mutex_lock_iothread();
     }
 
     return s->state == new_state ? 0 : -EINVAL;
 }
 
 /**
  * migration_completion: Used by migration_thread when there's not much left.
  *   The caller 'breaks' the loop when this returns.
  *
  * @s: Current migration state
  */
 static void migration_completion(MigrationState *s)
 {
     int ret;
     int current_active_state = s->state;
 
     if (s->state == MIGRATION_STATUS_ACTIVE) {
         qemu_mutex_lock_iothread();
         s->downtime_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
         qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
         s->vm_was_running = runstate_is_running();
         ret = global_state_store();
 
         if (!ret) {
             bool inactivate = !migrate_colo_enabled();
             ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
             trace_migration_completion_vm_stop(ret);
             if (ret >= 0) {
                 ret = migration_maybe_pause(s, &current_active_state,
                                             MIGRATION_STATUS_DEVICE);
             }
             if (ret >= 0) {
                 qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);
                 ret = qemu_savevm_state_complete_precopy(s->to_dst_file, false,
                                                          inactivate);
             }
             if (inactivate && ret >= 0) {
                 s->block_inactive = true;
             }
         }
         qemu_mutex_unlock_iothread();
 
         if (ret < 0) {
             goto fail;
         }
     } else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         trace_migration_completion_postcopy_end();
 
         qemu_mutex_lock_iothread();
         qemu_savevm_state_complete_postcopy(s->to_dst_file);
         qemu_mutex_unlock_iothread();
 
         /* Shutdown the postcopy fast path thread */
         if (migrate_postcopy_preempt()) {
             postcopy_preempt_shutdown_file(s);
         }
 
         trace_migration_completion_postcopy_end_after_complete();
     } else {
         goto fail;
     }
 
     /*
      * If rp was opened we must clean up the thread before
      * cleaning everything else up (since if there are no failures
      * it will wait for the destination to send it's status in
      * a SHUT command).
      */
     if (s->rp_state.rp_thread_created) {
         int rp_error;
         trace_migration_return_path_end_before();
         rp_error = await_return_path_close_on_source(s);
         trace_migration_return_path_end_after(rp_error);
         if (rp_error) {
             goto fail_invalidate;
         }
     }
 
     if (qemu_file_get_error(s->to_dst_file)) {
         trace_migration_completion_file_err();
         goto fail_invalidate;
     }
 
     if (migrate_colo_enabled() && s->state == MIGRATION_STATUS_ACTIVE) {
         /* COLO does not support postcopy */
         migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
                           MIGRATION_STATUS_COLO);
     } else {
         migrate_set_state(&s->state, current_active_state,
                           MIGRATION_STATUS_COMPLETED);
     }
 
     return;
 
 fail_invalidate:
     /* If not doing postcopy, vm_start() will be called: let's regain
      * control on images.
      */
     if (s->state == MIGRATION_STATUS_ACTIVE ||
         s->state == MIGRATION_STATUS_DEVICE) {
         Error *local_err = NULL;
 
         qemu_mutex_lock_iothread();
         bdrv_activate_all(&local_err);
         if (local_err) {
             error_report_err(local_err);
         } else {
             s->block_inactive = false;
         }
         qemu_mutex_unlock_iothread();
     }
 
 fail:
     migrate_set_state(&s->state, current_active_state,
                       MIGRATION_STATUS_FAILED);
 }
 
 /**
  * bg_migration_completion: Used by bg_migration_thread when after all the
  *   RAM has been saved. The caller 'breaks' the loop when this returns.
  *
  * @s: Current migration state
  */
 static void bg_migration_completion(MigrationState *s)
 {
     int current_active_state = s->state;
 
     /*
      * Stop tracking RAM writes - un-protect memory, un-register UFFD
      * memory ranges, flush kernel wait queues and wake up threads
      * waiting for write fault to be resolved.
      */
     ram_write_tracking_stop();
 
     if (s->state == MIGRATION_STATUS_ACTIVE) {
         /*
          * By this moment we have RAM content saved into the migration stream.
          * The next step is to flush the non-RAM content (device state)
          * right after the ram content. The device state has been stored into
          * the temporary buffer before RAM saving started.
          */
         qemu_put_buffer(s->to_dst_file, s->bioc->data, s->bioc->usage);
         qemu_fflush(s->to_dst_file);
     } else if (s->state == MIGRATION_STATUS_CANCELLING) {
         goto fail;
     }
 
     if (qemu_file_get_error(s->to_dst_file)) {
         trace_migration_completion_file_err();
         goto fail;
     }
 
     migrate_set_state(&s->state, current_active_state,
                       MIGRATION_STATUS_COMPLETED);
     return;
 
 fail:
     migrate_set_state(&s->state, current_active_state,
                       MIGRATION_STATUS_FAILED);
 }
 
 bool migrate_colo_enabled(void)
 {
     MigrationState *s = migrate_get_current();
     return s->enabled_capabilities[MIGRATION_CAPABILITY_X_COLO];
 }
 
 typedef enum MigThrError {
     /* No error detected */
     MIG_THR_ERR_NONE = 0,
     /* Detected error, but resumed successfully */
     MIG_THR_ERR_RECOVERED = 1,
     /* Detected fatal error, need to exit */
     MIG_THR_ERR_FATAL = 2,
 } MigThrError;
 
 static int postcopy_resume_handshake(MigrationState *s)
 {
     qemu_savevm_send_postcopy_resume(s->to_dst_file);
 
     while (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {
         qemu_sem_wait(&s->rp_state.rp_sem);
     }
 
     if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         return 0;
     }
 
     return -1;
 }
 
 /* Return zero if success, or <0 for error */
 static int postcopy_do_resume(MigrationState *s)
 {
     int ret;
 
     /*
      * Call all the resume_prepare() hooks, so that modules can be
      * ready for the migration resume.
      */
     ret = qemu_savevm_state_resume_prepare(s);
     if (ret) {
         error_report("%s: resume_prepare() failure detected: %d",
                      __func__, ret);
         return ret;
     }
 
     /*
      * Last handshake with destination on the resume (destination will
      * switch to postcopy-active afterwards)
      */
     ret = postcopy_resume_handshake(s);
     if (ret) {
         error_report("%s: handshake failed: %d", __func__, ret);
         return ret;
     }
 
     return 0;
 }
 
 /*
  * We don't return until we are in a safe state to continue current
  * postcopy migration.  Returns MIG_THR_ERR_RECOVERED if recovered, or
  * MIG_THR_ERR_FATAL if unrecovery failure happened.
  */
 static MigThrError postcopy_pause(MigrationState *s)
 {
     assert(s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
 
     while (true) {
         QEMUFile *file;
 
         /*
          * Current channel is possibly broken. Release it.  Note that this is
          * guaranteed even without lock because to_dst_file should only be
          * modified by the migration thread.  That also guarantees that the
          * unregister of yank is safe too without the lock.  It should be safe
          * even to be within the qemu_file_lock, but we didn't do that to avoid
          * taking more mutex (yank_lock) within qemu_file_lock.  TL;DR: we make
          * the qemu_file_lock critical section as small as possible.
          */
         assert(s->to_dst_file);
         migration_ioc_unregister_yank_from_file(s->to_dst_file);
         qemu_mutex_lock(&s->qemu_file_lock);
         file = s->to_dst_file;
         s->to_dst_file = NULL;
         qemu_mutex_unlock(&s->qemu_file_lock);
 
         qemu_file_shutdown(file);
         qemu_fclose(file);
 
         /*
          * Do the same to postcopy fast path socket too if there is.  No
          * locking needed because no racer as long as we do this before setting
          * status to paused.
          */
         if (s->postcopy_qemufile_src) {
             migration_ioc_unregister_yank_from_file(s->postcopy_qemufile_src);
             qemu_file_shutdown(s->postcopy_qemufile_src);
             qemu_fclose(s->postcopy_qemufile_src);
             s->postcopy_qemufile_src = NULL;
         }
 
         migrate_set_state(&s->state, s->state,
                           MIGRATION_STATUS_POSTCOPY_PAUSED);
 
         error_report("Detected IO failure for postcopy. "
                      "Migration paused.");
 
         /*
          * We wait until things fixed up. Then someone will setup the
          * status back for us.
          */
         while (s->state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
             qemu_sem_wait(&s->postcopy_pause_sem);
         }
 
         if (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {
             /* Woken up by a recover procedure. Give it a shot */
 
             if (postcopy_preempt_wait_channel(s)) {
                 /*
                  * Preempt enabled, and new channel create failed; loop
                  * back to wait for another recovery.
                  */
                 continue;
             }
 
             /*
              * Firstly, let's wake up the return path now, with a new
              * return path channel.
              */
             qemu_sem_post(&s->postcopy_pause_rp_sem);
 
             /* Do the resume logic */
             if (postcopy_do_resume(s) == 0) {
                 /* Let's continue! */
                 trace_postcopy_pause_continued();
                 return MIG_THR_ERR_RECOVERED;
             } else {
                 /*
                  * Something wrong happened during the recovery, let's
                  * pause again. Pause is always better than throwing
                  * data away.
                  */
                 continue;
             }
         } else {
             /* This is not right... Time to quit. */
             return MIG_THR_ERR_FATAL;
         }
     }
 }
 
 static MigThrError migration_detect_error(MigrationState *s)
 {
     int ret;
     int state = s->state;
     Error *local_error = NULL;
 
     if (state == MIGRATION_STATUS_CANCELLING ||
         state == MIGRATION_STATUS_CANCELLED) {
         /* End the migration, but don't set the state to failed */
         return MIG_THR_ERR_FATAL;
     }
 
     /*
      * Try to detect any file errors.  Note that postcopy_qemufile_src will
      * be NULL when postcopy preempt is not enabled.
      */
     ret = qemu_file_get_error_obj_any(s->to_dst_file,
                                       s->postcopy_qemufile_src,
                                       &local_error);
     if (!ret) {
         /* Everything is fine */
         assert(!local_error);
         return MIG_THR_ERR_NONE;
     }
 
     if (local_error) {
         migrate_set_error(s, local_error);
         error_free(local_error);
     }
 
     if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret) {
         /*
          * For postcopy, we allow the network to be down for a
          * while. After that, it can be continued by a
          * recovery phase.
          */
         return postcopy_pause(s);
     } else {
         /*
          * For precopy (or postcopy with error outside IO), we fail
          * with no time.
          */
         migrate_set_state(&s->state, state, MIGRATION_STATUS_FAILED);
         trace_migration_thread_file_err();
 
         /* Time to stop the migration, now. */
         return MIG_THR_ERR_FATAL;
     }
 }
 
 /* How many bytes have we transferred since the beginning of the migration */
 static uint64_t migration_total_bytes(MigrationState *s)
 {
     return qemu_file_total_transferred(s->to_dst_file) +
         ram_counters.multifd_bytes;
 }
 
 static void migration_calculate_complete(MigrationState *s)
 {
     uint64_t bytes = migration_total_bytes(s);
     int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     int64_t transfer_time;
 
     s->total_time = end_time - s->start_time;
     if (!s->downtime) {
         /*
          * It's still not set, so we are precopy migration.  For
          * postcopy, downtime is calculated during postcopy_start().
          */
         s->downtime = end_time - s->downtime_start;
     }
 
     transfer_time = s->total_time - s->setup_time;
     if (transfer_time) {
         s->mbps = ((double) bytes * 8.0) / transfer_time / 1000;
     }
 }
 
 static void update_iteration_initial_status(MigrationState *s)
 {
     /*
      * Update these three fields at the same time to avoid mismatch info lead
      * wrong speed calculation.
      */
     s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     s->iteration_initial_bytes = migration_total_bytes(s);
     s->iteration_initial_pages = ram_get_total_transferred_pages();
 }
 
 static void migration_update_counters(MigrationState *s,
                                       int64_t current_time)
 {
     uint64_t transferred, transferred_pages, time_spent;
     uint64_t current_bytes; /* bytes transferred since the beginning */
     double bandwidth;
 
     if (current_time < s->iteration_start_time + BUFFER_DELAY) {
         return;
     }
 
     current_bytes = migration_total_bytes(s);
     transferred = current_bytes - s->iteration_initial_bytes;
     time_spent = current_time - s->iteration_start_time;
     bandwidth = (double)transferred / time_spent;
     s->threshold_size = bandwidth * s->parameters.downtime_limit;
 
     s->mbps = (((double) transferred * 8.0) /
                ((double) time_spent / 1000.0)) / 1000.0 / 1000.0;
 
     transferred_pages = ram_get_total_transferred_pages() -
                             s->iteration_initial_pages;
     s->pages_per_second = (double) transferred_pages /
                              (((double) time_spent / 1000.0));
 
     /*
      * if we haven't sent anything, we don't want to
      * recalculate. 10000 is a small enough number for our purposes
      */
     if (ram_counters.dirty_pages_rate && transferred > 10000) {
         s->expected_downtime = ram_counters.remaining / bandwidth;
     }
 
     qemu_file_reset_rate_limit(s->to_dst_file);
 
     update_iteration_initial_status(s);
 
     trace_migrate_transferred(transferred, time_spent,
                               bandwidth, s->threshold_size);
 }
 
 /* Migration thread iteration status */
 typedef enum {
     MIG_ITERATE_RESUME,         /* Resume current iteration */
     MIG_ITERATE_SKIP,           /* Skip current iteration */
     MIG_ITERATE_BREAK,          /* Break the loop */
 } MigIterateState;
 
 /*
  * Return true if continue to the next iteration directly, false
  * otherwise.
  */
 static MigIterateState migration_iteration_run(MigrationState *s)
 {
     uint64_t pending_size, pend_pre, pend_compat, pend_post;
     bool in_postcopy = s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE;
 
     qemu_savevm_state_pending(s->to_dst_file, s->threshold_size, &pend_pre,
                               &pend_compat, &pend_post);
     pending_size = pend_pre + pend_compat + pend_post;
 
     trace_migrate_pending(pending_size, s->threshold_size,
                           pend_pre, pend_compat, pend_post);
 
     if (pending_size && pending_size >= s->threshold_size) {
         /* Still a significant amount to transfer */
         if (!in_postcopy && pend_pre <= s->threshold_size &&
             qatomic_read(&s->start_postcopy)) {
             if (postcopy_start(s)) {
                 error_report("%s: postcopy failed to start", __func__);
             }
             return MIG_ITERATE_SKIP;
         }
         /* Just another iteration step */
         qemu_savevm_state_iterate(s->to_dst_file, in_postcopy);
     } else {
         trace_migration_thread_low_pending(pending_size);
         migration_completion(s);
         return MIG_ITERATE_BREAK;
     }
 
     return MIG_ITERATE_RESUME;
 }
 
 static void migration_iteration_finish(MigrationState *s)
 {
     /* If we enabled cpu throttling for auto-converge, turn it off. */
     cpu_throttle_stop();
 
     qemu_mutex_lock_iothread();
     switch (s->state) {
     case MIGRATION_STATUS_COMPLETED:
         migration_calculate_complete(s);
         runstate_set(RUN_STATE_POSTMIGRATE);
         break;
     case MIGRATION_STATUS_COLO:
         if (!migrate_colo_enabled()) {
             error_report("%s: critical error: calling COLO code without "
                          "COLO enabled", __func__);
         }
         migrate_start_colo_process(s);
         s->vm_was_running = true;
         /* Fallthrough */
     case MIGRATION_STATUS_FAILED:
     case MIGRATION_STATUS_CANCELLED:
     case MIGRATION_STATUS_CANCELLING:
         if (s->vm_was_running) {
             if (!runstate_check(RUN_STATE_SHUTDOWN)) {
                 vm_start();
             }
         } else {
             if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
                 runstate_set(RUN_STATE_POSTMIGRATE);
             }
         }
         break;
 
     default:
         /* Should not reach here, but if so, forgive the VM. */
         error_report("%s: Unknown ending state %d", __func__, s->state);
         break;
     }
     migrate_fd_cleanup_schedule(s);
     qemu_mutex_unlock_iothread();
 }
 
 static void bg_migration_iteration_finish(MigrationState *s)
 {
     qemu_mutex_lock_iothread();
     switch (s->state) {
     case MIGRATION_STATUS_COMPLETED:
         migration_calculate_complete(s);
         break;
 
     case MIGRATION_STATUS_ACTIVE:
     case MIGRATION_STATUS_FAILED:
     case MIGRATION_STATUS_CANCELLED:
     case MIGRATION_STATUS_CANCELLING:
         break;
 
     default:
         /* Should not reach here, but if so, forgive the VM. */
         error_report("%s: Unknown ending state %d", __func__, s->state);
         break;
     }
 
     migrate_fd_cleanup_schedule(s);
     qemu_mutex_unlock_iothread();
 }
 
 /*
  * Return true if continue to the next iteration directly, false
  * otherwise.
  */
 static MigIterateState bg_migration_iteration_run(MigrationState *s)
 {
     int res;
 
     res = qemu_savevm_state_iterate(s->to_dst_file, false);
     if (res > 0) {
         bg_migration_completion(s);
         return MIG_ITERATE_BREAK;
     }
 
     return MIG_ITERATE_RESUME;
 }
 
 void migration_make_urgent_request(void)
 {
     qemu_sem_post(&migrate_get_current()->rate_limit_sem);
 }
 
 void migration_consume_urgent_request(void)
 {
     qemu_sem_wait(&migrate_get_current()->rate_limit_sem);
 }
 
 /* Returns true if the rate limiting was broken by an urgent request */
 bool migration_rate_limit(void)
 {
     int64_t now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     MigrationState *s = migrate_get_current();
 
     bool urgent = false;
     migration_update_counters(s, now);
     if (qemu_file_rate_limit(s->to_dst_file)) {
 
         if (qemu_file_get_error(s->to_dst_file)) {
             return false;
         }
         /*
          * Wait for a delay to do rate limiting OR
          * something urgent to post the semaphore.
          */
         int ms = s->iteration_start_time + BUFFER_DELAY - now;
         trace_migration_rate_limit_pre(ms);
         if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {
             /*
              * We were woken by one or more urgent things but
              * the timedwait will have consumed one of them.
              * The service routine for the urgent wake will dec
              * the semaphore itself for each item it consumes,
              * so add this one we just eat back.
              */
             qemu_sem_post(&s->rate_limit_sem);
             urgent = true;
         }
         trace_migration_rate_limit_post(urgent);
     }
     return urgent;
 }
 
 /*
  * if failover devices are present, wait they are completely
  * unplugged
  */
 
 static void qemu_savevm_wait_unplug(MigrationState *s, int old_state,
                                     int new_state)
 {
     if (qemu_savevm_state_guest_unplug_pending()) {
         migrate_set_state(&s->state, old_state, MIGRATION_STATUS_WAIT_UNPLUG);
 
         while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
                qemu_savevm_state_guest_unplug_pending()) {
             qemu_sem_timedwait(&s->wait_unplug_sem, 250);
         }
         if (s->state != MIGRATION_STATUS_WAIT_UNPLUG) {
             int timeout = 120; /* 30 seconds */
             /*
              * migration has been canceled
              * but as we have started an unplug we must wait the end
              * to be able to plug back the card
              */
             while (timeout-- && qemu_savevm_state_guest_unplug_pending()) {
                 qemu_sem_timedwait(&s->wait_unplug_sem, 250);
             }
             if (qemu_savevm_state_guest_unplug_pending() &&
                 !qtest_enabled()) {
                 warn_report("migration: partially unplugged device on "
                             "failure");
             }
         }
 
         migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, new_state);
     } else {
         migrate_set_state(&s->state, old_state, new_state);
     }
 }
 
 /*
  * Master migration thread on the source VM.
  * It drives the migration and pumps the data down the outgoing channel.
  */
 static void *migration_thread(void *opaque)
 {
     MigrationState *s = opaque;
     int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     MigThrError thr_error;
     bool urgent = false;
 
     rcu_register_thread();
 
     object_ref(OBJECT(s));
     update_iteration_initial_status(s);
 
     qemu_savevm_state_header(s->to_dst_file);
 
     /*
      * If we opened the return path, we need to make sure dst has it
      * opened as well.
      */
     if (s->rp_state.rp_thread_created) {
         /* Now tell the dest that it should open its end so it can reply */
         qemu_savevm_send_open_return_path(s->to_dst_file);
 
         /* And do a ping that will make stuff easier to debug */
         qemu_savevm_send_ping(s->to_dst_file, 1);
     }
 
     if (migrate_postcopy()) {
         /*
          * Tell the destination that we *might* want to do postcopy later;
          * if the other end can't do postcopy it should fail now, nice and
          * early.
          */
         qemu_savevm_send_postcopy_advise(s->to_dst_file);
     }
 
     if (migrate_colo_enabled()) {
         /* Notify migration destination that we enable COLO */
         qemu_savevm_send_colo_enable(s->to_dst_file);
     }
 
     qemu_savevm_state_setup(s->to_dst_file);
 
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
     s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
 
     trace_migration_thread_setup_complete();
 
     while (migration_is_active(s)) {
         if (urgent || !qemu_file_rate_limit(s->to_dst_file)) {
             MigIterateState iter_state = migration_iteration_run(s);
             if (iter_state == MIG_ITERATE_SKIP) {
                 continue;
             } else if (iter_state == MIG_ITERATE_BREAK) {
                 break;
             }
         }
 
         /*
          * Try to detect any kind of failures, and see whether we
          * should stop the migration now.
          */
         thr_error = migration_detect_error(s);
         if (thr_error == MIG_THR_ERR_FATAL) {
             /* Stop migration */
             break;
         } else if (thr_error == MIG_THR_ERR_RECOVERED) {
             /*
              * Just recovered from a e.g. network failure, reset all
              * the local variables. This is important to avoid
              * breaking transferred_bytes and bandwidth calculation
              */
             update_iteration_initial_status(s);
         }
 
         urgent = migration_rate_limit();
     }
 
     trace_migration_thread_after_loop();
     migration_iteration_finish(s);
     object_unref(OBJECT(s));
     rcu_unregister_thread();
     return NULL;
 }
 
 static void bg_migration_vm_start_bh(void *opaque)
 {
     MigrationState *s = opaque;
 
     qemu_bh_delete(s->vm_start_bh);
     s->vm_start_bh = NULL;
 
     vm_start();
     s->downtime = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - s->downtime_start;
 }
 
 /**
  * Background snapshot thread, based on live migration code.
  * This is an alternative implementation of live migration mechanism
  * introduced specifically to support background snapshots.
  *
  * It takes advantage of userfault_fd write protection mechanism introduced
  * in v5.7 kernel. Compared to existing dirty page logging migration much
  * lesser stream traffic is produced resulting in smaller snapshot images,
  * simply cause of no page duplicates can get into the stream.
  *
  * Another key point is that generated vmstate stream reflects machine state
  * 'frozen' at the beginning of snapshot creation compared to dirty page logging
  * mechanism, which effectively results in that saved snapshot is the state of VM
  * at the end of the process.
  */
 static void *bg_migration_thread(void *opaque)
 {
     MigrationState *s = opaque;
     int64_t setup_start;
     MigThrError thr_error;
     QEMUFile *fb;
     bool early_fail = true;
 
     rcu_register_thread();
     object_ref(OBJECT(s));
 
     qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);
 
     setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     /*
      * We want to save vmstate for the moment when migration has been
      * initiated but also we want to save RAM content while VM is running.
      * The RAM content should appear first in the vmstate. So, we first
      * stash the non-RAM part of the vmstate to the temporary buffer,
      * then write RAM part of the vmstate to the migration stream
      * with vCPUs running and, finally, write stashed non-RAM part of
      * the vmstate from the buffer to the migration stream.
      */
     s->bioc = qio_channel_buffer_new(512 * 1024);
     qio_channel_set_name(QIO_CHANNEL(s->bioc), "vmstate-buffer");
     fb = qemu_file_new_output(QIO_CHANNEL(s->bioc));
     object_unref(OBJECT(s->bioc));
 
     update_iteration_initial_status(s);
 
     /*
      * Prepare for tracking memory writes with UFFD-WP - populate
      * RAM pages before protecting.
      */
 #ifdef __linux__
     ram_write_tracking_prepare();
 #endif
 
     qemu_savevm_state_header(s->to_dst_file);
     qemu_savevm_state_setup(s->to_dst_file);
 
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
     s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
 
     trace_migration_thread_setup_complete();
     s->downtime_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
 
     qemu_mutex_lock_iothread();
 
     /*
      * If VM is currently in suspended state, then, to make a valid runstate
      * transition in vm_stop_force_state() we need to wakeup it up.
      */
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
     s->vm_was_running = runstate_is_running();
 
     if (global_state_store()) {
         goto fail;
     }
     /* Forcibly stop VM before saving state of vCPUs and devices */
     if (vm_stop_force_state(RUN_STATE_PAUSED)) {
         goto fail;
     }
     /*
      * Put vCPUs in sync with shadow context structures, then
      * save their state to channel-buffer along with devices.
      */
     cpu_synchronize_all_states();
     if (qemu_savevm_state_complete_precopy_non_iterable(fb, false, false)) {
         goto fail;
     }
     /*
      * Since we are going to get non-iterable state data directly
      * from s->bioc->data, explicit flush is needed here.
      */
     qemu_fflush(fb);
 
     /* Now initialize UFFD context and start tracking RAM writes */
     if (ram_write_tracking_start()) {
         goto fail;
     }
     early_fail = false;
 
     /*
      * Start VM from BH handler to avoid write-fault lock here.
      * UFFD-WP protection for the whole RAM is already enabled so
      * calling VM state change notifiers from vm_start() would initiate
      * writes to virtio VQs memory which is in write-protected region.
      */
     s->vm_start_bh = qemu_bh_new(bg_migration_vm_start_bh, s);
     qemu_bh_schedule(s->vm_start_bh);
 
     qemu_mutex_unlock_iothread();
 
     while (migration_is_active(s)) {
         MigIterateState iter_state = bg_migration_iteration_run(s);
         if (iter_state == MIG_ITERATE_SKIP) {
             continue;
         } else if (iter_state == MIG_ITERATE_BREAK) {
             break;
         }
 
         /*
          * Try to detect any kind of failures, and see whether we
          * should stop the migration now.
          */
         thr_error = migration_detect_error(s);
         if (thr_error == MIG_THR_ERR_FATAL) {
             /* Stop migration */
             break;
         }
 
         migration_update_counters(s, qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
     }
 
     trace_migration_thread_after_loop();
 
 fail:
     if (early_fail) {
         migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
                 MIGRATION_STATUS_FAILED);
         qemu_mutex_unlock_iothread();
     }
 
     bg_migration_iteration_finish(s);
 
     qemu_fclose(fb);
     object_unref(OBJECT(s));
     rcu_unregister_thread();
 
     return NULL;
 }
 
 void migrate_fd_connect(MigrationState *s, Error *error_in)
 {
     Error *local_err = NULL;
     int64_t rate_limit;
     bool resume = s->state == MIGRATION_STATUS_POSTCOPY_PAUSED;
 
     /*
      * If there's a previous error, free it and prepare for another one.
      * Meanwhile if migration completes successfully, there won't have an error
      * dumped when calling migrate_fd_cleanup().
      */
     migrate_error_free(s);
 
     s->expected_downtime = s->parameters.downtime_limit;
     if (resume) {
         assert(s->cleanup_bh);
     } else {
         assert(!s->cleanup_bh);
         s->cleanup_bh = qemu_bh_new(migrate_fd_cleanup_bh, s);
     }
     if (error_in) {
         migrate_fd_error(s, error_in);
         if (resume) {
             /*
              * Don't do cleanup for resume if channel is invalid, but only dump
              * the error.  We wait for another channel connect from the user.
              * The error_report still gives HMP user a hint on what failed.
              * It's normally done in migrate_fd_cleanup(), but call it here
              * explicitly.
              */
             error_report_err(error_copy(s->error));
         } else {
             migrate_fd_cleanup(s);
         }
         return;
     }
 
     if (resume) {
         /* This is a resumed migration */
         rate_limit = s->parameters.max_postcopy_bandwidth /
             XFER_LIMIT_RATIO;
     } else {
         /* This is a fresh new migration */
         rate_limit = s->parameters.max_bandwidth / XFER_LIMIT_RATIO;
 
         /* Notify before starting migration thread */
         notifier_list_notify(&migration_state_notifiers, s);
     }
 
     qemu_file_set_rate_limit(s->to_dst_file, rate_limit);
     qemu_file_set_blocking(s->to_dst_file, true);
 
     /*
      * Open the return path. For postcopy, it is used exclusively. For
      * precopy, only if user specified "return-path" capability would
      * QEMU uses the return path.
      */
     if (migrate_postcopy_ram() || migrate_use_return_path()) {
         if (open_return_path_on_source(s, !resume)) {
             error_report("Unable to open return-path for postcopy");
             migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED);
             migrate_fd_cleanup(s);
             return;
         }
     }
 
     /* This needs to be done before resuming a postcopy */
     if (postcopy_preempt_setup(s, &local_err)) {
         error_report_err(local_err);
         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                           MIGRATION_STATUS_FAILED);
         migrate_fd_cleanup(s);
         return;
     }
 
     if (resume) {
         /* Wakeup the main migration thread to do the recovery */
         migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
                           MIGRATION_STATUS_POSTCOPY_RECOVER);
         qemu_sem_post(&s->postcopy_pause_sem);
         return;
     }
 
     if (multifd_save_setup(&local_err) != 0) {
         error_report_err(local_err);
         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
                           MIGRATION_STATUS_FAILED);
         migrate_fd_cleanup(s);
         return;
     }
 
     if (migrate_background_snapshot()) {
         qemu_thread_create(&s->thread, "bg_snapshot",
                 bg_migration_thread, s, QEMU_THREAD_JOINABLE);
     } else {
         qemu_thread_create(&s->thread, "live_migration",
                 migration_thread, s, QEMU_THREAD_JOINABLE);
     }
     s->migration_thread_running = true;
 }
 
 void migration_global_dump(Monitor *mon)
 {
     MigrationState *ms = migrate_get_current();
 
     monitor_printf(mon, "globals:\n");
     monitor_printf(mon, "store-global-state: %s\n",
                    ms->store_global_state ? "on" : "off");
     monitor_printf(mon, "only-migratable: %s\n",
                    only_migratable ? "on" : "off");
     monitor_printf(mon, "send-configuration: %s\n",
                    ms->send_configuration ? "on" : "off");
     monitor_printf(mon, "send-section-footer: %s\n",
                    ms->send_section_footer ? "on" : "off");
     monitor_printf(mon, "decompress-error-check: %s\n",
                    ms->decompress_error_check ? "on" : "off");
     monitor_printf(mon, "clear-bitmap-shift: %u\n",
                    ms->clear_bitmap_shift);
 }
 
 #define DEFINE_PROP_MIG_CAP(name, x)             \
     DEFINE_PROP_BOOL(name, MigrationState, enabled_capabilities[x], false)
 
 static Property migration_properties[] = {
     DEFINE_PROP_BOOL("store-global-state", MigrationState,
                      store_global_state, true),
     DEFINE_PROP_BOOL("send-configuration", MigrationState,
                      send_configuration, true),
     DEFINE_PROP_BOOL("send-section-footer", MigrationState,
                      send_section_footer, true),
     DEFINE_PROP_BOOL("decompress-error-check", MigrationState,
                       decompress_error_check, true),
     DEFINE_PROP_UINT8("x-clear-bitmap-shift", MigrationState,
                       clear_bitmap_shift, CLEAR_BITMAP_SHIFT_DEFAULT),
 
     /* Migration parameters */
     DEFINE_PROP_UINT8("x-compress-level", MigrationState,
                       parameters.compress_level,
                       DEFAULT_MIGRATE_COMPRESS_LEVEL),
     DEFINE_PROP_UINT8("x-compress-threads", MigrationState,
                       parameters.compress_threads,
                       DEFAULT_MIGRATE_COMPRESS_THREAD_COUNT),
     DEFINE_PROP_BOOL("x-compress-wait-thread", MigrationState,
                       parameters.compress_wait_thread, true),
     DEFINE_PROP_UINT8("x-decompress-threads", MigrationState,
                       parameters.decompress_threads,
                       DEFAULT_MIGRATE_DECOMPRESS_THREAD_COUNT),
     DEFINE_PROP_UINT8("x-throttle-trigger-threshold", MigrationState,
                       parameters.throttle_trigger_threshold,
                       DEFAULT_MIGRATE_THROTTLE_TRIGGER_THRESHOLD),
     DEFINE_PROP_UINT8("x-cpu-throttle-initial", MigrationState,
                       parameters.cpu_throttle_initial,
                       DEFAULT_MIGRATE_CPU_THROTTLE_INITIAL),
     DEFINE_PROP_UINT8("x-cpu-throttle-increment", MigrationState,
                       parameters.cpu_throttle_increment,
                       DEFAULT_MIGRATE_CPU_THROTTLE_INCREMENT),
     DEFINE_PROP_BOOL("x-cpu-throttle-tailslow", MigrationState,
                       parameters.cpu_throttle_tailslow, false),
     DEFINE_PROP_SIZE("x-max-bandwidth", MigrationState,
                       parameters.max_bandwidth, MAX_THROTTLE),
     DEFINE_PROP_UINT64("x-downtime-limit", MigrationState,
                       parameters.downtime_limit,
                       DEFAULT_MIGRATE_SET_DOWNTIME),
     DEFINE_PROP_UINT32("x-checkpoint-delay", MigrationState,
                       parameters.x_checkpoint_delay,
                       DEFAULT_MIGRATE_X_CHECKPOINT_DELAY),
     DEFINE_PROP_UINT8("multifd-channels", MigrationState,
                       parameters.multifd_channels,
                       DEFAULT_MIGRATE_MULTIFD_CHANNELS),
     DEFINE_PROP_MULTIFD_COMPRESSION("multifd-compression", MigrationState,
                       parameters.multifd_compression,
                       DEFAULT_MIGRATE_MULTIFD_COMPRESSION),
     DEFINE_PROP_UINT8("multifd-zlib-level", MigrationState,
                       parameters.multifd_zlib_level,
                       DEFAULT_MIGRATE_MULTIFD_ZLIB_LEVEL),
     DEFINE_PROP_UINT8("multifd-zstd-level", MigrationState,
                       parameters.multifd_zstd_level,
                       DEFAULT_MIGRATE_MULTIFD_ZSTD_LEVEL),
     DEFINE_PROP_SIZE("xbzrle-cache-size", MigrationState,
                       parameters.xbzrle_cache_size,
                       DEFAULT_MIGRATE_XBZRLE_CACHE_SIZE),
     DEFINE_PROP_SIZE("max-postcopy-bandwidth", MigrationState,
                       parameters.max_postcopy_bandwidth,
                       DEFAULT_MIGRATE_MAX_POSTCOPY_BANDWIDTH),
     DEFINE_PROP_UINT8("max-cpu-throttle", MigrationState,
                       parameters.max_cpu_throttle,
                       DEFAULT_MIGRATE_MAX_CPU_THROTTLE),
     DEFINE_PROP_SIZE("announce-initial", MigrationState,
                       parameters.announce_initial,
                       DEFAULT_MIGRATE_ANNOUNCE_INITIAL),
     DEFINE_PROP_SIZE("announce-max", MigrationState,
                       parameters.announce_max,
                       DEFAULT_MIGRATE_ANNOUNCE_MAX),
     DEFINE_PROP_SIZE("announce-rounds", MigrationState,
                       parameters.announce_rounds,
                       DEFAULT_MIGRATE_ANNOUNCE_ROUNDS),
     DEFINE_PROP_SIZE("announce-step", MigrationState,
                       parameters.announce_step,
                       DEFAULT_MIGRATE_ANNOUNCE_STEP),
     DEFINE_PROP_BOOL("x-postcopy-preempt-break-huge", MigrationState,
                       postcopy_preempt_break_huge, true),
     DEFINE_PROP_STRING("tls-creds", MigrationState, parameters.tls_creds),
     DEFINE_PROP_STRING("tls-hostname", MigrationState, parameters.tls_hostname),
     DEFINE_PROP_STRING("tls-authz", MigrationState, parameters.tls_authz),
 
     /* Migration capabilities */
     DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
     DEFINE_PROP_MIG_CAP("x-rdma-pin-all", MIGRATION_CAPABILITY_RDMA_PIN_ALL),
     DEFINE_PROP_MIG_CAP("x-auto-converge", MIGRATION_CAPABILITY_AUTO_CONVERGE),
     DEFINE_PROP_MIG_CAP("x-zero-blocks", MIGRATION_CAPABILITY_ZERO_BLOCKS),
     DEFINE_PROP_MIG_CAP("x-compress", MIGRATION_CAPABILITY_COMPRESS),
     DEFINE_PROP_MIG_CAP("x-events", MIGRATION_CAPABILITY_EVENTS),
     DEFINE_PROP_MIG_CAP("x-postcopy-ram", MIGRATION_CAPABILITY_POSTCOPY_RAM),
     DEFINE_PROP_MIG_CAP("x-postcopy-preempt",
                         MIGRATION_CAPABILITY_POSTCOPY_PREEMPT),
     DEFINE_PROP_MIG_CAP("x-colo", MIGRATION_CAPABILITY_X_COLO),
     DEFINE_PROP_MIG_CAP("x-release-ram", MIGRATION_CAPABILITY_RELEASE_RAM),
     DEFINE_PROP_MIG_CAP("x-block", MIGRATION_CAPABILITY_BLOCK),
     DEFINE_PROP_MIG_CAP("x-return-path", MIGRATION_CAPABILITY_RETURN_PATH),
     DEFINE_PROP_MIG_CAP("x-multifd", MIGRATION_CAPABILITY_MULTIFD),
     DEFINE_PROP_MIG_CAP("x-background-snapshot",
             MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT),
 #ifdef CONFIG_LINUX
     DEFINE_PROP_MIG_CAP("x-zero-copy-send",
             MIGRATION_CAPABILITY_ZERO_COPY_SEND),
 #endif
 
     DEFINE_PROP_END_OF_LIST(),
 };
 
 static void migration_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->user_creatable = false;
     device_class_set_props(dc, migration_properties);
 }
 
 static void migration_instance_finalize(Object *obj)
 {
     MigrationState *ms = MIGRATION_OBJ(obj);
 
     qemu_mutex_destroy(&ms->error_mutex);
     qemu_mutex_destroy(&ms->qemu_file_lock);
     qemu_sem_destroy(&ms->wait_unplug_sem);
     qemu_sem_destroy(&ms->rate_limit_sem);
     qemu_sem_destroy(&ms->pause_sem);
     qemu_sem_destroy(&ms->postcopy_pause_sem);
     qemu_sem_destroy(&ms->postcopy_pause_rp_sem);
     qemu_sem_destroy(&ms->rp_state.rp_sem);
     qemu_sem_destroy(&ms->postcopy_qemufile_src_sem);
     error_free(ms->error);
 }
 
 static void migration_instance_init(Object *obj)
 {
     MigrationState *ms = MIGRATION_OBJ(obj);
     MigrationParameters *params = &ms->parameters;
 
     ms->state = MIGRATION_STATUS_NONE;
     ms->mbps = -1;
     ms->pages_per_second = -1;
     qemu_sem_init(&ms->pause_sem, 0);
     qemu_mutex_init(&ms->error_mutex);
 
     params->tls_hostname = g_strdup("");
     params->tls_creds = g_strdup("");
 
     /* Set has_* up only for parameter checks */
     params->has_compress_level = true;
     params->has_compress_threads = true;
     params->has_compress_wait_thread = true;
     params->has_decompress_threads = true;
     params->has_throttle_trigger_threshold = true;
     params->has_cpu_throttle_initial = true;
     params->has_cpu_throttle_increment = true;
     params->has_cpu_throttle_tailslow = true;
     params->has_max_bandwidth = true;
     params->has_downtime_limit = true;
     params->has_x_checkpoint_delay = true;
     params->has_block_incremental = true;
     params->has_multifd_channels = true;
     params->has_multifd_compression = true;
     params->has_multifd_zlib_level = true;
     params->has_multifd_zstd_level = true;
     params->has_xbzrle_cache_size = true;
     params->has_max_postcopy_bandwidth = true;
     params->has_max_cpu_throttle = true;
     params->has_announce_initial = true;
     params->has_announce_max = true;
     params->has_announce_rounds = true;
     params->has_announce_step = true;
     params->has_tls_creds = true;
     params->has_tls_hostname = true;
     params->has_tls_authz = true;
 
     qemu_sem_init(&ms->postcopy_pause_sem, 0);
     qemu_sem_init(&ms->postcopy_pause_rp_sem, 0);
     qemu_sem_init(&ms->rp_state.rp_sem, 0);
     qemu_sem_init(&ms->rate_limit_sem, 0);
     qemu_sem_init(&ms->wait_unplug_sem, 0);
     qemu_sem_init(&ms->postcopy_qemufile_src_sem, 0);
     qemu_mutex_init(&ms->qemu_file_lock);
 }
 
 /*
  * Return true if check pass, false otherwise. Error will be put
  * inside errp if provided.
  */
 static bool migration_object_check(MigrationState *ms, Error **errp)
 {
     MigrationCapabilityStatusList *head = NULL;
     /* Assuming all off */
     bool cap_list[MIGRATION_CAPABILITY__MAX] = { 0 }, ret;
     int i;
 
     if (!migrate_params_check(&ms->parameters, errp)) {
         return false;
     }
 
     for (i = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
         if (ms->enabled_capabilities[i]) {
             QAPI_LIST_PREPEND(head, migrate_cap_add(i, true));
         }
     }
 
     ret = migrate_caps_check(cap_list, head, errp);
 
     /* It works with head == NULL */
     qapi_free_MigrationCapabilityStatusList(head);
 
     return ret;
 }
 
 static const TypeInfo migration_type = {
     .name = TYPE_MIGRATION,
     /*
      * NOTE: TYPE_MIGRATION is not really a device, as the object is
      * not created using qdev_new(), it is not attached to the qdev
      * device tree, and it is never realized.
      *
      * TODO: Make this TYPE_OBJECT once QOM provides something like
      * TYPE_DEVICE's "-global" properties.
      */
     .parent = TYPE_DEVICE,
     .class_init = migration_class_init,
     .class_size = sizeof(MigrationClass),
     .instance_size = sizeof(MigrationState),
     .instance_init = migration_instance_init,
     .instance_finalize = migration_instance_finalize,
 };
 
 static void register_migration_types(void)
 {
     type_register_static(&migration_type);
 }
 
 type_init(register_migration_types);