build: move COLO under CONFIG_REPLICATION

We don't allow to use x-colo capability when replication is not
configured. So, no reason to build COLO when replication is disabled,
it's unusable in this case.

Note also that the check in migrate_caps_check() is not the only
restriction: some functions in migration/colo.c will just abort if
called with not defined CONFIG_REPLICATION, for example:

    migration_iteration_finish()
       case MIGRATION_STATUS_COLO:
           migrate_start_colo_process()
               colo_process_checkpoint()
                   abort()

It could probably make sense to have possibility to enable COLO without
REPLICATION, but this requires deeper audit of colo & replication code,
which may be done later if needed.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Acked-by: Dr. David Alan Gilbert <dave@treblig.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20230428194928.1426370-4-vsementsov@yandex-team.ru>
Signed-off-by: Juan Quintela <quintela@redhat.com>

hmp-commands.hx

@@ -1052,6 +1052,7 @@ SRST
   migration (or once already in postcopy).
 ERST
 
+#ifdef CONFIG_REPLICATION
     {
         .name       = "x_colo_lost_heartbeat",
         .args_type  = "",
@@ -1060,6 +1061,7 @@ ERST
                       "a failover or takeover is needed.",
         .cmd = hmp_x_colo_lost_heartbeat,
     },
+#endif
 
 SRST
 ``x_colo_lost_heartbeat``

migration/colo.c

@@ -26,9 +26,7 @@
 #include "qemu/rcu.h"
 #include "migration/failover.h"
 #include "migration/ram.h"
-#ifdef CONFIG_REPLICATION
 #include "block/replication.h"
-#endif
 #include "net/colo-compare.h"
 #include "net/colo.h"
 #include "block/block.h"
@@ -86,7 +84,6 @@ void colo_checkpoint_delay_set(void)
 static void secondary_vm_do_failover(void)
 {
 /* COLO needs enable block-replication */
-#ifdef CONFIG_REPLICATION
     int old_state;
     MigrationIncomingState *mis = migration_incoming_get_current();
     Error *local_err = NULL;
@@ -151,14 +148,10 @@ static void secondary_vm_do_failover(void)
     if (mis->migration_incoming_co) {
         qemu_coroutine_enter(mis->migration_incoming_co);
     }
-#else
-    abort();
-#endif
 }
 
 static void primary_vm_do_failover(void)
 {
-#ifdef CONFIG_REPLICATION
     MigrationState *s = migrate_get_current();
     int old_state;
     Error *local_err = NULL;
@@ -199,9 +192,6 @@ static void primary_vm_do_failover(void)
 
     /* Notify COLO thread that failover work is finished */
     qemu_sem_post(&s->colo_exit_sem);
-#else
-    abort();
-#endif
 }
 
 COLOMode get_colo_mode(void)
@@ -235,7 +225,6 @@ void colo_do_failover(void)
     }
 }
 
-#ifdef CONFIG_REPLICATION
 void qmp_xen_set_replication(bool enable, bool primary,
                              bool has_failover, bool failover,
                              Error **errp)
@@ -289,7 +278,6 @@ void qmp_xen_colo_do_checkpoint(Error **errp)
     /* Notify all filters of all NIC to do checkpoint */
     colo_notify_filters_event(COLO_EVENT_CHECKPOINT, errp);
 }
-#endif
 
 COLOStatus *qmp_query_colo_status(Error **errp)
 {
@@ -453,15 +441,11 @@ static int colo_do_checkpoint_transaction(MigrationState *s,
     }
     qemu_mutex_lock_iothread();
 
-#ifdef CONFIG_REPLICATION
     replication_do_checkpoint_all(&local_err);
     if (local_err) {
         qemu_mutex_unlock_iothread();
         goto out;
     }
-#else
-        abort();
-#endif
 
     colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
     if (local_err) {
@@ -579,15 +563,11 @@ static void colo_process_checkpoint(MigrationState *s)
     object_unref(OBJECT(bioc));
 
     qemu_mutex_lock_iothread();
-#ifdef CONFIG_REPLICATION
     replication_start_all(REPLICATION_MODE_PRIMARY, &local_err);
     if (local_err) {
         qemu_mutex_unlock_iothread();
         goto out;
     }
-#else
-        abort();
-#endif
 
     vm_start();
     qemu_mutex_unlock_iothread();
@@ -755,7 +735,6 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
         return;
     }
 
-#ifdef CONFIG_REPLICATION
     replication_get_error_all(&local_err);
     if (local_err) {
         error_propagate(errp, local_err);
@@ -772,9 +751,6 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
         qemu_mutex_unlock_iothread();
         return;
     }
-#else
-    abort();
-#endif
     /* Notify all filters of all NIC to do checkpoint */
     colo_notify_filters_event(COLO_EVENT_CHECKPOINT, &local_err);
 
@@ -881,15 +857,11 @@ void *colo_process_incoming_thread(void *opaque)
     object_unref(OBJECT(bioc));
 
     qemu_mutex_lock_iothread();
-#ifdef CONFIG_REPLICATION
     replication_start_all(REPLICATION_MODE_SECONDARY, &local_err);
     if (local_err) {
         qemu_mutex_unlock_iothread();
         goto out;
     }
-#else
-        abort();
-#endif
     vm_start();
     qemu_mutex_unlock_iothread();
     trace_colo_vm_state_change("stop", "run");

migration/meson.build

@@ -13,8 +13,6 @@ softmmu_ss.add(files(
   'block-dirty-bitmap.c',
   'channel.c',
   'channel-block.c',
-  'colo-failover.c',
-  'colo.c',
   'exec.c',
   'fd.c',
   'global_state.c',
@@ -33,6 +31,10 @@ softmmu_ss.add(files(
   'threadinfo.c',
 ), gnutls)
 
+if get_option('replication').allowed()
+  softmmu_ss.add(files('colo-failover.c', 'colo.c'))
+endif
+
 softmmu_ss.add(when: rdma, if_true: files('rdma.c'))
 if get_option('live_block_migration').allowed()
   softmmu_ss.add(files('block.c'))

migration/migration-hmp-cmds.c

@@ -643,13 +643,15 @@ void hmp_migrate_start_postcopy(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, err);
 }
 
+#ifdef CONFIG_REPLICATION
 void hmp_x_colo_lost_heartbeat(Monitor *mon, const QDict *qdict)
 {
     Error *err = NULL;
 
     qmp_x_colo_lost_heartbeat(&err);
     hmp_handle_error(mon, err);
 }
+#endif
 
 typedef struct HMPMigrationStatus {
     QEMUTimer *timer;

migration/migration.c

@@ -392,6 +392,12 @@ void migration_incoming_disable_colo(void)
 
 int migration_incoming_enable_colo(void)
 {
+#ifndef CONFIG_REPLICATION
+    error_report("ENABLE_COLO command come in migration stream, but COLO "
+                 "module is not built in");
+    return -ENOTSUP;
+#endif
+
     if (ram_block_discard_disable(true)) {
         error_report("COLO: cannot disable RAM discard");
         return -EBUSY;

qapi/migration.json

@@ -1366,7 +1366,8 @@
 # <- { "return": {} }
 ##
 { 'command': 'x-colo-lost-heartbeat',
-  'features': [ 'unstable' ] }
+  'features': [ 'unstable' ],
+  'if': 'CONFIG_REPLICATION' }
 
 ##
 # @migrate_cancel:
@@ -1638,7 +1639,8 @@
 ##
 { 'struct': 'COLOStatus',
   'data': { 'mode': 'COLOMode', 'last-mode': 'COLOMode',
-            'reason': 'COLOExitReason' } }
+            'reason': 'COLOExitReason' },
+  'if': 'CONFIG_REPLICATION' }
 
 ##
 # @query-colo-status:
@@ -1655,7 +1657,8 @@
 # Since: 3.1
 ##
 { 'command': 'query-colo-status',
-  'returns': 'COLOStatus' }
+  'returns': 'COLOStatus',
+  'if': 'CONFIG_REPLICATION' }
 
 ##
 # @migrate-recover:

stubs/colo.c

@@ -0,0 +1,39 @@
+#include "qemu/osdep.h"
+#include "qemu/notify.h"
+#include "net/colo-compare.h"
+#include "migration/colo.h"
+#include "migration/migration.h"
+#include "qemu/error-report.h"
+#include "qapi/qapi-commands-migration.h"
+
+void colo_shutdown(void)
+{
+}
+
+void *colo_process_incoming_thread(void *opaque)
+{
+    error_report("Impossible happend: trying to start COLO thread when COLO "
+                 "module is not built in");
+    abort();
+}
+
+void colo_checkpoint_delay_set(void)
+{
+}
+
+void migrate_start_colo_process(MigrationState *s)
+{
+    error_report("Impossible happend: trying to start COLO when COLO "
+                 "module is not built in");
+    abort();
+}
+
+bool migration_in_colo_state(void)
+{
+    return false;
+}
+
+bool migration_incoming_in_colo_state(void)
+{
+    return false;
+}

stubs/meson.build

@@ -45,6 +45,7 @@ stub_ss.add(files('target-get-monitor-def.c'))
 stub_ss.add(files('target-monitor-defs.c'))
 stub_ss.add(files('trace-control.c'))
 stub_ss.add(files('uuid.c'))
+stub_ss.add(files('colo.c'))
 stub_ss.add(files('vmstate.c'))
 stub_ss.add(files('vm-stop.c'))
 stub_ss.add(files('win32-kbd-hook.c'))