[04/18] migration: introduce postcopy-only pending

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 5c30ef7..dc656be 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -58,8 +58,9 @@  typedef struct SaveVMHandlers {
     /* This runs outside the iothread lock!  */
     int (*save_live_setup)(QEMUFile *f, void *opaque);
     void (*save_live_pending)(QEMUFile *f, void *opaque, uint64_t max_size,
-                              uint64_t *non_postcopiable_pending,
-                              uint64_t *postcopiable_pending);
+                              uint64_t *res_precopy_only,
+                              uint64_t *res_compatible,
+                              uint64_t *res_postcopy_only);
     LoadStateHandler *load_state;
 } SaveVMHandlers;
 
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index ee7c760..d88bcda 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -114,8 +114,9 @@  void qemu_savevm_state_cleanup(void);
 void qemu_savevm_state_complete_postcopy(QEMUFile *f);
 void qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only);
 void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
-                               uint64_t *res_non_postcopiable,
-                               uint64_t *res_postcopiable);
+                               uint64_t *res_precopy_only,
+                               uint64_t *res_compatible,
+                               uint64_t *res_postcopy_only);
 void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command,
                               uint16_t len, uint8_t *data);
 void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
diff --git a/migration/block.c b/migration/block.c
index ebc10e6..83b0785 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -830,8 +830,9 @@  static int block_save_complete(QEMUFile *f, void *opaque)
 }
 
 static void block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
-                               uint64_t *non_postcopiable_pending,
-                               uint64_t *postcopiable_pending)
+                               uint64_t *res_precopy_only,
+                               uint64_t *res_compatible,
+                               uint64_t *res_postcopy_only)
 {
     /* Estimate pending number of bytes to send */
     uint64_t pending;
@@ -852,7 +853,7 @@  static void block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
 
     DPRINTF("Enter save live pending  %" PRIu64 "\n", pending);
     /* We don't do postcopy */
-    *non_postcopiable_pending += pending;
+    *res_precopy_only += pending;
 }
 
 static int block_load(QEMUFile *f, void *opaque, int version_id)
diff --git a/migration/migration.c b/migration/migration.c
index 4300de0..01a7bd5 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1764,20 +1764,21 @@  static void *migration_thread(void *opaque)
         uint64_t pending_size;
 
         if (!qemu_file_rate_limit(s->to_dst_file)) {
-            uint64_t pend_post, pend_nonpost;
+            uint64_t pend_pre, pend_compat, pend_post;
 
-            qemu_savevm_state_pending(s->to_dst_file, max_size, &pend_nonpost,
-                                      &pend_post);
-            pending_size = pend_nonpost + pend_post;
+            qemu_savevm_state_pending(s->to_dst_file, max_size, &pend_pre,
+                                      &pend_compat, &pend_post);
+            pending_size = pend_pre + pend_compat + pend_post;
             trace_migrate_pending(pending_size, max_size,
-                                  pend_post, pend_nonpost);
+                                  pend_pre, pend_compat, pend_post);
             if (pending_size && pending_size >= max_size) {
                 /* Still a significant amount to transfer */
 
                 if (migrate_postcopy() &&
                     s->state != MIGRATION_STATUS_POSTCOPY_ACTIVE &&
-                    pend_nonpost <= max_size &&
-                    atomic_read(&s->start_postcopy)) {
+                    pend_pre <= max_size &&
+                    (atomic_read(&s->start_postcopy) ||
+                     (pend_pre + pend_compat <= max_size))) {
 
                     if (!postcopy_start(s, &old_vm_running)) {
                         current_active_state = MIGRATION_STATUS_POSTCOPY_ACTIVE;
diff --git a/migration/ram.c b/migration/ram.c
index 424ce0b..fd843b7 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2062,8 +2062,9 @@  static int ram_save_complete(QEMUFile *f, void *opaque)
 }
 
 static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
-                             uint64_t *non_postcopiable_pending,
-                             uint64_t *postcopiable_pending)
+                             uint64_t *res_precopy_only,
+                             uint64_t *res_compatible,
+                             uint64_t *res_postcopy_only)
 {
     uint64_t remaining_size;
 
@@ -2081,9 +2082,9 @@  static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
 
     if (migrate_postcopy_ram()) {
         /* We can do postcopy, and all the data is postcopiable */
-        *postcopiable_pending += remaining_size;
+        *res_compatible += remaining_size;
     } else {
-        *non_postcopiable_pending += remaining_size;
+        *res_precopy_only += remaining_size;
     }
 }
 
diff --git a/migration/savevm.c b/migration/savevm.c
index cce542f..7757a29 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1114,13 +1114,15 @@  void qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only)
  * for units that can't do postcopy.
  */
 void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
-                               uint64_t *res_non_postcopiable,
-                               uint64_t *res_postcopiable)
+                               uint64_t *res_precopy_only,
+                               uint64_t *res_compatible,
+                               uint64_t *res_postcopy_only)
 {
     SaveStateEntry *se;
 
-    *res_non_postcopiable = 0;
-    *res_postcopiable = 0;
+    *res_precopy_only = 0;
+    *res_compatible = 0;
+    *res_postcopy_only = 0;
 
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
@@ -1133,7 +1135,7 @@  void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
             }
         }
         se->ops->save_live_pending(f, se->opaque, max_size,
-                                   res_non_postcopiable, res_postcopiable);
+                res_precopy_only, res_compatible, res_postcopy_only);
     }
 }
 
diff --git a/migration/trace-events b/migration/trace-events
index 8568dab..bcc6124 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -74,7 +74,7 @@  migrate_fd_cleanup(void) ""
 migrate_fd_error(const char *error_desc) "error=%s"
 migrate_fd_cancel(void) ""
 migrate_handle_rp_req_pages(const char *rbname, size_t start, size_t len) "in %s at %zx len %zx"
-migrate_pending(uint64_t size, uint64_t max, uint64_t post, uint64_t nonpost) "pending size %" PRIu64 " max %" PRIu64 " (post=%" PRIu64 " nonpost=%" PRIu64 ")"
+migrate_pending(uint64_t size, uint64_t max, uint64_t pre, uint64_t compat, uint64_t post) "pending size %" PRIu64 " max %" PRIu64 " (pre = %" PRIu64 " compat=%" PRIu64 " post=%" PRIu64 ")"
 migrate_send_rp_message(int msg_type, uint16_t len) "%d: len %d"
 migration_completion_file_err(void) ""
 migration_completion_postcopy_end(void) ""