1 files changed, 87 insertions, 51 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 7a14aa98d8..90fca70cb7 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -184,16 +184,27 @@ static int migration_maybe_pause(MigrationState *s,
                                  int new_state);
 static void migrate_fd_cancel(MigrationState *s);
 
-static bool migrate_allow_multi_channels = true;
+static bool migration_needs_multiple_sockets(void)
+{
+    return migrate_use_multifd() || migrate_postcopy_preempt();
+}
 
-void migrate_protocol_allow_multi_channels(bool allow)
+static bool uri_supports_multi_channels(const char *uri)
 {
-    migrate_allow_multi_channels = allow;
+    return strstart(uri, "tcp:", NULL) || strstart(uri, "unix:", NULL) ||
+           strstart(uri, "vsock:", NULL);
 }
 
-bool migrate_multi_channels_is_allowed(void)
+static bool
+migration_channels_and_uri_compatible(const char *uri, Error **errp)
 {
-    return migrate_allow_multi_channels;
+    if (migration_needs_multiple_sockets() &&
+        !uri_supports_multi_channels(uri)) {
+        error_setg(errp, "Migration requires multi-channel URIs (e.g. tcp)");
+        return false;
+    }
+
+    return true;
 }
 
 static gint page_request_addr_cmp(gconstpointer ap, gconstpointer bp)
@@ -224,6 +235,8 @@ void migration_object_init(void)
     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_sem_init(&current_incoming->postcopy_qemufile_dst_done, 0);
+
     qemu_mutex_init(&current_incoming->page_request_mutex);
     current_incoming->page_requested = g_tree_new(page_request_addr_cmp);
 
@@ -302,6 +315,8 @@ void migration_incoming_state_destroy(void)
 {
     struct MigrationIncomingState *mis = migration_incoming_get_current();
 
+    multifd_load_cleanup();
+
     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);
@@ -493,12 +508,15 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
 
-    migrate_protocol_allow_multi_channels(false); /* reset it anyway */
+    /* URI is not suitable for migration? */
+    if (!migration_channels_and_uri_compatible(uri, errp)) {
+        return;
+    }
+
     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)) {
@@ -543,13 +561,7 @@ static void process_incoming_migration_bh(void *opaque)
      */
     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. */
+    multifd_load_shutdown();
 
     dirty_bitmap_mig_before_vm_start();
 
@@ -649,9 +661,9 @@ fail:
     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);
-    }
+
+    multifd_load_cleanup();
+
     exit(EXIT_FAILURE);
 }
 
@@ -723,9 +735,29 @@ void migration_fd_process_incoming(QEMUFile *f, Error **errp)
     migration_incoming_process();
 }
 
-static bool migration_needs_multiple_sockets(void)
+/*
+ * Returns true when we want to start a new incoming migration process,
+ * false otherwise.
+ */
+static bool migration_should_start_incoming(bool main_channel)
 {
-    return migrate_use_multifd() || migrate_postcopy_preempt();
+    /* Multifd doesn't start unless all channels are established */
+    if (migrate_use_multifd()) {
+        return migration_has_all_channels();
+    }
+
+    /* Preempt channel only starts when the main channel is created */
+    if (migrate_postcopy_preempt()) {
+        return main_channel;
+    }
+
+    /*
+     * For all the rest types of migration, we should only reach here when
+     * it's the main channel that's being created, and we should always
+     * proceed with this channel.
+     */
+    assert(main_channel);
+    return true;
 }
 
 void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
@@ -789,7 +821,7 @@ void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
         }
     }
 
-    if (migration_has_all_channels()) {
+    if (migration_should_start_incoming(default_channel)) {
         /* If it's a recovery, we're done */
         if (postcopy_try_recover()) {
             return;
@@ -1378,15 +1410,6 @@ static bool migrate_caps_check(bool *cap_list,
     }
 #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");
@@ -2471,6 +2494,11 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
     MigrationState *s = migrate_get_current();
     const char *p = NULL;
 
+    /* URI is not suitable for migration? */
+    if (!migration_channels_and_uri_compatible(uri, errp)) {
+        return;
+    }
+
     if (!migrate_prepare(s, has_blk && blk, has_inc && inc,
                          has_resume && resume, errp)) {
         /* Error detected, put into errp */
@@ -2483,11 +2511,9 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         }
     }
 
-    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)) {
@@ -3022,6 +3048,7 @@ retry:
         case MIG_RP_MSG_PONG:
             tmp32 = ldl_be_p(buf);
             trace_source_return_path_thread_pong(tmp32);
+            qemu_sem_post(&ms->rp_state.rp_pong_acks);
             break;
 
         case MIG_RP_MSG_REQ_PAGES:
@@ -3155,6 +3182,13 @@ static int await_return_path_close_on_source(MigrationState *ms)
     return ms->rp_state.error;
 }
 
+static inline void
+migration_wait_main_channel(MigrationState *ms)
+{
+    /* Wait until one PONG message received */
+    qemu_sem_wait(&ms->rp_state.rp_pong_acks);
+}
+
 /*
  * Switch from normal iteration to postcopy
  * Returns non-0 on error
@@ -3169,9 +3203,12 @@ static int postcopy_start(MigrationState *ms)
     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_postcopy_preempt()) {
+        migration_wait_main_channel(ms);
+        if (postcopy_preempt_establish_channel(ms)) {
+            migrate_set_state(&ms->state, ms->state, MIGRATION_STATUS_FAILED);
+            return -1;
+        }
     }
 
     if (!migrate_pause_before_switchover()) {
@@ -3583,6 +3620,20 @@ static int postcopy_do_resume(MigrationState *s)
     }
 
     /*
+     * If preempt is enabled, re-establish the preempt channel.  Note that
+     * we do it after resume prepare to make sure the main channel will be
+     * created before the preempt channel.  E.g. with weak network, the
+     * dest QEMU may get messed up with the preempt and main channels on
+     * the order of connection setup.  This guarantees the correct order.
+     */
+    ret = postcopy_preempt_establish_channel(s);
+    if (ret) {
+        error_report("%s: postcopy_preempt_establish_channel(): %d",
+                     __func__, ret);
+        return ret;
+    }
+
+    /*
      * Last handshake with destination on the resume (destination will
      * switch to postcopy-active afterwards)
      */
@@ -3643,14 +3694,6 @@ static MigThrError postcopy_pause(MigrationState *s)
         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.
@@ -4343,15 +4386,6 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
         }
     }
 
-    /* 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,
@@ -4525,6 +4559,7 @@ static void migration_instance_finalize(Object *obj)
     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->rp_state.rp_pong_acks);
     qemu_sem_destroy(&ms->postcopy_qemufile_src_sem);
     error_free(ms->error);
 }
@@ -4571,6 +4606,7 @@ static void migration_instance_init(Object *obj)
     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->rp_state.rp_pong_acks, 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);