migrate_start_postcopy: Command to trigger transition to postcopy

Once postcopy is enabled (with migrate_set_capability), the migration
will still start on precopy mode.  To cause a transition into postcopy
the:

  migrate_start_postcopy

command must be issued.  Postcopy will start sometime after this
(when it's next checked in the migration loop).

Issuing the command before migration has started will error,
and issuing after it has finished is ignored.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 3a4ae3950ad500fce21a86147317fe3bf21fa3f0..8939b9838a3b0e8c5b7a3766235e7df575626056 100644 (file)
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1005,6 +1005,21 @@ STEXI
 @item migrate_set_parameter @var{parameter} @var{value}
 @findex migrate_set_parameter
 Set the parameter @var{parameter} for migration.
+ETEXI
+
+    {
+        .name       = "migrate_start_postcopy",
+        .args_type  = "",
+        .params     = "",
+        .help       = "Switch migration to postcopy mode",
+        .mhandler.cmd = hmp_migrate_start_postcopy,
+    },
+
+STEXI
+@item migrate_start_postcopy
+@findex migrate_start_postcopy
+Switch in-progress migration to postcopy mode. Ignored after the end of
+migration (or once already in postcopy).
 ETEXI
 
     {

diff --git a/hmp.c b/hmp.c
index a15d00c18c81d97796e546939356e5e42dc4e6a5..e1f854aefe7284034835e02cedfc165062e1040a 100644 (file)
--- a/hmp.c
+++ b/hmp.c
@@ -1293,6 +1293,13 @@ void hmp_client_migrate_info(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &err);
 }
 
+void hmp_migrate_start_postcopy(Monitor *mon, const QDict *qdict)
+{
+    Error *err = NULL;
+    qmp_migrate_start_postcopy(&err);
+    hmp_handle_error(mon, &err);
+}
+
 void hmp_set_password(Monitor *mon, const QDict *qdict)
 {
     const char *protocol  = qdict_get_str(qdict, "protocol");

diff --git a/hmp.h b/hmp.h
index 81656c3d829e85584c0c7cb9ac7dd2e84cd6980e..a8c5b5a9a6591128a2da69a867bbf5d23f3ce9ff 100644 (file)
--- a/hmp.h
+++ b/hmp.h
@@ -69,6 +69,7 @@ void hmp_migrate_set_capability(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_cache_size(Monitor *mon, const QDict *qdict);
 void hmp_client_migrate_info(Monitor *mon, const QDict *qdict);
+void hmp_migrate_start_postcopy(Monitor *mon, const QDict *qdict);
 void hmp_set_password(Monitor *mon, const QDict *qdict);
 void hmp_expire_password(Monitor *mon, const QDict *qdict);
 void hmp_eject(Monitor *mon, const QDict *qdict);

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 2e9fa3c65d63334be86fba9f7df812626f3df65d..217666650adf18c3feb756c9c58cafdbf3d4915c 100644 (file)
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -127,6 +127,9 @@ struct MigrationState
     int64_t xbzrle_cache_size;
     int64_t setup_time;
     int64_t dirty_sync_count;
+
+    /* Flag set once the migration has been asked to enter postcopy */
+    bool start_postcopy;
 };
 
 void process_incoming_migration(QEMUFile *f);

diff --git a/migration/migration.c b/migration/migration.c
index bb4c92ef9397e9d398c04fe6343212227a78c529..9c46472949fc01db618132b5d8657695e169431e 100644 (file)
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -668,6 +668,28 @@ void qmp_migrate_set_parameters(bool has_compress_level,
     }
 }
 
+void qmp_migrate_start_postcopy(Error **errp)
+{
+    MigrationState *s = migrate_get_current();
+
+    if (!migrate_postcopy_ram()) {
+        error_setg(errp, "Enable postcopy with migration_set_capability before"
+                         " the start of migration");
+        return;
+    }
+
+    if (s->state == MIGRATION_STATUS_NONE) {
+        error_setg(errp, "Postcopy must be started after migration has been"
+                         " started");
+        return;
+    }
+    /*
+     * we don't error if migration has finished since that would be racy
+     * with issuing this command.
+     */
+    atomic_set(&s->start_postcopy, true);
+}
+
 /* shared migration helpers */
 
 static void migrate_set_state(MigrationState *s, int old_state, int new_state)

diff --git a/qapi-schema.json b/qapi-schema.json
index 8638d428b97d2599bb212335fee063cd42909625..d25df930345e07454f17e55bfd8b3f0dfb76d0b5 100644 (file)
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -701,6 +701,14 @@
   'data': { 'protocol': 'str', 'hostname': 'str', '*port': 'int',
             '*tls-port': 'int', '*cert-subject': 'str' } }
 
+##
+# @migrate-start-postcopy
+#
+# Switch migration to postcopy mode
+#
+# Since: 2.5
+{ 'command': 'migrate-start-postcopy' }
+
 ##
 # @MouseInfo:
 #

diff --git a/qmp-commands.hx b/qmp-commands.hx
index d7cf0ff264f9a1db7f614cee5fb408590118c485..7f85d4046c1fcec7d225b7f8d32376593c7b6a29 100644 (file)
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -717,6 +717,25 @@ Example:
 <- { "return": {} }
 
 EQMP
+    {
+        .name       = "migrate-start-postcopy",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_migrate_start_postcopy,
+    },
+
+SQMP
+migrate-start-postcopy
+----------------------
+
+Switch an in-progress migration to postcopy mode. Ignored after the end of
+migration (or once already in postcopy).
+
+Example:
+-> { "execute": "migrate-start-postcopy" }
+<- { "return": {} }
+
+EQMP
+
     {
         .name       = "query-migrate-cache-size",
         .args_type  = "",