fix(instances): a migration runs in the mode the VM's state allows, and is logged as it ran

moveto read the VM state for each flag and dropped options that did
not fit it, so a request could run as something else than asked; the
log then named the mode from the form ("live" or "offline"), not the
one used. The API did not log at all and answered "instance migrate is
started" after the migration had finished.

- moveto reads the state once. A running VM migrates live, or without
  live paused for the transfer (non-live); a paused VM stays paused; a
  shut-off VM moves offline. Live for a shut-off VM, offline for a
  running or paused one, and any other state are refused before
  anything changes. unsafe, auto converge (live only) and compressed
  apply to a running VM.
- migrate_instance logs the outcome for the VM page and the API: the
  mode and options used, or the error. The API answers
  "instance is migrated (<mode>)" and accepts requests that leave out
  an optional option.
- Post copy is gone from the form, the view and the API: only the
  flag was set, and without migrateStartPostCopy, which the app never
  called, the migration never switched to post copy.

vrtManager/instance.py

@@ -27,7 +27,6 @@ try:
         VIR_MIGRATE_LIVE,
         VIR_MIGRATE_OFFLINE,
         VIR_MIGRATE_PERSIST_DEST,
-        VIR_MIGRATE_POSTCOPY,
         VIR_MIGRATE_UNDEFINE_SOURCE,
         VIR_MIGRATE_UNSAFE,
         VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY,
@@ -111,35 +110,45 @@ class wvmInstances(wvmConnect):
         dom = self.get_instance(name)
         dom.resume()
 
-    def moveto(
-        self,
-        conn,
-        name,
-        live,
-        unsafe,
-        offline,
-        autoconverge=False,
-        compress=False,
-        postcopy=False,
-        uri=None,
-    ):
-        """uri: the native migration URI (tcp://address) on the destination;
-        None lets libvirt use the destination's own hostname."""
+    def moveto(self, conn, name, live, unsafe, offline, autoconverge=False, compress=False, uri=None):
+        """Migrates the VM of conn (a wvmInstance on the source) here.
+
+        The mode follows the VM's state, read once: a running VM migrates
+        live or, without live, paused for the transfer (non-live); a paused
+        VM stays paused; a shut-off VM moves offline. A request that does not
+        fit the state is refused. unsafe, autoconverge (live only) and
+        compress apply to a running VM. uri: the native migration URI
+        (tcp://address) on the destination; None lets libvirt use the
+        destination's own hostname. Returns the mode and options used, for
+        the log."""
+        state = conn.get_status()
+        if state == 5:
+            if live:
+                raise util.OperationError("A shut-off VM cannot be migrated live")
+            mode = ["offline"]
+        elif state in (1, 3):
+            if offline:
+                raise util.OperationError("A running or paused VM cannot be migrated offline")
+            mode = ["live" if live else "non-live"]
+        else:
+            raise util.OperationError("The VM can be migrated when it is running, paused or shut off")
+
         # The source definition always goes: one left behind points at the
         # same (shared) disks as the migrated VM and could be started again.
         flags = VIR_MIGRATE_PERSIST_DEST | VIR_MIGRATE_UNDEFINE_SOURCE
-        if live and conn.get_status() != 5:
-            flags |= VIR_MIGRATE_LIVE
-        if unsafe and conn.get_status() == 1:
-            flags |= VIR_MIGRATE_UNSAFE
-        if offline and conn.get_status() == 5:
+        if state == 5:
             flags |= VIR_MIGRATE_OFFLINE
-        if not offline and autoconverge:
-            flags |= VIR_MIGRATE_AUTO_CONVERGE
-        if not offline and compress and conn.get_status() == 1:
-            flags |= VIR_MIGRATE_COMPRESSED
-        if not offline and postcopy and conn.get_status() == 1:
-            flags |= VIR_MIGRATE_POSTCOPY
+        elif live:
+            flags |= VIR_MIGRATE_LIVE
+        if state == 1:
+            for wanted, flag, label in (
+                (unsafe, VIR_MIGRATE_UNSAFE, "unsafe"),
+                (autoconverge and live, VIR_MIGRATE_AUTO_CONVERGE, "auto converge"),
+                (compress, VIR_MIGRATE_COMPRESSED, "compressed"),
+            ):
+                if wanted:
+                    flags |= flag
+                    mode.append(label)
 
         dom = conn.instance
 
@@ -151,13 +160,15 @@ class wvmInstances(wvmConnect):
                 "Destination host emulator is different. Cannot be migrated"
             )
 
-        if conn.get_status() == 5:
+        if state == 5:
             # Workaround for a libvirt bug (RHEL-156800), see move_definition.
             # Once supported hosts all run a fixed libvirt, this branch and
-            # move_definition can go: VIR_MIGRATE_OFFLINE is set above.
+            # move_definition can go: the flags above are those for
+            # dom.migrate.
             self.move_definition(dom)
-            return
-        dom.migrate(self.wvm, flags, None, uri, 0)
+        else:
+            dom.migrate(self.wvm, flags, None, uri, 0)
+        return ", ".join(mode)
 
     def move_definition(self, dom):
         """Migrates a shut-off VM: that is only its definition, as the disks