retrieve paused/running state at migration start

This patch fixes the bug where paused/running state is not
transmitted during migration.  As a result, in the QEMU driver
for example the machine was always started on the destination
end.

In order to do so, just read the state and if it is appropriate and
set the VIR_MIGRATE_PAUSED flag.

* src/libvirt.c (virDomainMigrateVersion1, virDomainMigrateVersion2):
  Automatically add VIR_MIGRATE_PAUSED when appropriate.
* src/xen/xend_internal.c (xenDaemonDomainMigratePerform): Give a nicer
  error message when migration of paused domains is attempted.

src/libvirt.c

@@ -2963,7 +2963,13 @@ virDomainMigrateVersion1 (virDomainPtr domain,
     virDomainPtr ddomain = NULL;
     char *uri_out = NULL;
     char *cookie = NULL;
-    int cookielen = 0;
+    int cookielen = 0, ret;
+    virDomainInfo info;
+
+    ret = virDomainGetInfo (domain, &info);
+    if (ret == 0 && info.state == VIR_DOMAIN_PAUSED) {
+        flags |= VIR_MIGRATE_PAUSED;
+    }
 
     /* Prepare the migration.
      *
@@ -3028,6 +3034,7 @@ virDomainMigrateVersion2 (virDomainPtr domain,
     char *cookie = NULL;
     char *dom_xml = NULL;
     int cookielen = 0, ret;
+    virDomainInfo info;
 
     /* Prepare the migration.
      *
@@ -3054,6 +3061,11 @@ virDomainMigrateVersion2 (virDomainPtr domain,
     if (!dom_xml)
         return NULL;
 
+    ret = virDomainGetInfo (domain, &info);
+    if (ret == 0 && info.state == VIR_DOMAIN_PAUSED) {
+        flags |= VIR_MIGRATE_PAUSED;
+    }
+
     ret = dconn->driver->domainMigratePrepare2
         (dconn, &cookie, &cookielen, uri, &uri_out, flags, dname,
          bandwidth, dom_xml);

src/xen/xend_internal.c

@@ -4444,6 +4444,15 @@ xenDaemonDomainMigratePerform (virDomainPtr domain,
     if (flags & VIR_MIGRATE_PERSIST_DEST)
         flags &= ~VIR_MIGRATE_PERSIST_DEST;
 
+    /* This is buggy in Xend, but could be supported in principle.  Give
+     * a nice error message.
+     */
+    if (flags & VIR_MIGRATE_PAUSED) {
+        virXendError (conn, VIR_ERR_NO_SUPPORT,
+                      "%s", _("xenDaemonDomainMigrate: xend cannot migrate paused domains"));
+        return -1;
+    }
+
     /* XXX we could easily do tunnelled & peer2peer migration too
        if we want to. support these... */
     if (flags != 0) {