Merge remote-tracking branch 'remotes/amit-migration/tags/for-2.2-2' into staging

Fix from a while back that unfortunately got ignored.  Dave Gilbert says
it may actually fix a case where autoconverge would break on a repeat
migration (and not just fix stats).

# gpg: Signature made Thu 20 Nov 2014 12:52:41 GMT using RSA key ID 854083B6
# gpg: Good signature from "Amit Shah <amit@amitshah.net>"
# gpg:                 aka "Amit Shah <amit@kernel.org>"
# gpg:                 aka "Amit Shah <amitshah@gmx.net>"

* remotes/amit-migration/tags/for-2.2-2:
  migration: static variables will not be reset at second migration
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

arch_init.c

@@ -486,15 +486,23 @@ static void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length)
 
 
 /* Needs iothread lock! */
+/* Fix me: there are too many global variables used in migration process. */
+static int64_t start_time;
+static int64_t bytes_xfer_prev;
+static int64_t num_dirty_pages_period;
+
+static void migration_bitmap_sync_init(void)
+{
+    start_time = 0;
+    bytes_xfer_prev = 0;
+    num_dirty_pages_period = 0;
+}
 
 static void migration_bitmap_sync(void)
 {
     RAMBlock *block;
     uint64_t num_dirty_pages_init = migration_dirty_pages;
     MigrationState *s = migrate_get_current();
-    static int64_t start_time;
-    static int64_t bytes_xfer_prev;
-    static int64_t num_dirty_pages_period;
     int64_t end_time;
     int64_t bytes_xfer_now;
     static uint64_t xbzrle_cache_miss_prev;
@@ -774,6 +782,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     mig_throttle_on = false;
     dirty_rate_high_cnt = 0;
     bitmap_sync_count = 0;
+    migration_bitmap_sync_init();
 
     if (migrate_use_xbzrle()) {
         XBZRLE_cache_lock();