migration: Use migration_transferred_bytes()

There are only two differnces with the old value:

- the amount of QEMUFile that hasn't yet been flushed.  It can be
  discussed what is more exact, the new or the old one.
- the amount of transferred bytes that we forgot to account for (the
  newer is better, i.e. exact).

Notice that this two values are used to:
a - present to the user
b - calculate the rate_limit

So a few KB here and there is not going to make a difference.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231025091117.6342-11-quintela@redhat.com>

migration/migration.c

@@ -942,7 +942,7 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
     size_t page_size = qemu_target_page_size();
 
     info->ram = g_malloc0(sizeof(*info->ram));
-    info->ram->transferred = stat64_get(&mig_stats.transferred);
+    info->ram->transferred = migration_transferred_bytes();
     info->ram->total = ram_bytes_total();
     info->ram->duplicate = stat64_get(&mig_stats.zero_pages);
     /* legacy value.  It is not used anymore */

migration/ram.c

@@ -557,7 +557,7 @@ void mig_throttle_counter_reset(void)
 
     rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     rs->num_dirty_pages_period = 0;
-    rs->bytes_xfer_prev = stat64_get(&mig_stats.transferred);
+    rs->bytes_xfer_prev = migration_transferred_bytes();
 }
 
 /**
@@ -1003,7 +1003,7 @@ static void migration_trigger_throttle(RAMState *rs)
 {
     uint64_t threshold = migrate_throttle_trigger_threshold();
     uint64_t bytes_xfer_period =
-        stat64_get(&mig_stats.transferred) - rs->bytes_xfer_prev;
+        migration_transferred_bytes() - rs->bytes_xfer_prev;
     uint64_t bytes_dirty_period = rs->num_dirty_pages_period * TARGET_PAGE_SIZE;
     uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100;
 
@@ -1073,7 +1073,7 @@ static void migration_bitmap_sync(RAMState *rs, bool last_stage)
         /* reset period counters */
         rs->time_last_bitmap_sync = end_time;
         rs->num_dirty_pages_period = 0;
-        rs->bytes_xfer_prev = stat64_get(&mig_stats.transferred);
+        rs->bytes_xfer_prev = migration_transferred_bytes();
     }
     if (migrate_events()) {
         uint64_t generation = stat64_get(&mig_stats.dirty_sync_count);