qemu: Fix a possible deadlock in p2p migration

Two more calls to remote libvirtd have to be surrounded by
qemuDomainObjEnterRemoteWithDriver() and
qemuDomainObjExitRemoteWithDriver() to prevent possible deadlock between
two communicating libvirt daemons.

See commit f0c8e1cb for further details.

src/qemu/qemu_driver.c

@@ -11625,24 +11625,38 @@ static int doPeer2PeerMigrate(virDomainPtr dom,
     int ret = -1;
     virConnectPtr dconn = NULL;
     char *dom_xml;
+    bool p2p;
 
     /* the order of operations is important here; we make sure the
      * destination side is completely setup before we touch the source
      */
 
+    qemuDomainObjEnterRemoteWithDriver(driver, vm);
     dconn = virConnectOpen(uri);
+    qemuDomainObjExitRemoteWithDriver(driver, vm);
     if (dconn == NULL) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         _("Failed to connect to remote libvirt URI %s"), uri);
         return -1;
     }
-    if (!VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
-                                  VIR_DRV_FEATURE_MIGRATION_P2P)) {
+
+    qemuDomainObjEnterRemoteWithDriver(driver, vm);
+    p2p = VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
+                                   VIR_DRV_FEATURE_MIGRATION_P2P);
+    qemuDomainObjExitRemoteWithDriver(driver, vm);
+    if (!p2p) {
         qemuReportError(VIR_ERR_OPERATION_FAILED, "%s",
                         _("Destination libvirt does not support peer-to-peer migration protocol"));
         goto cleanup;
     }
 
+    /* domain may have been stopped while we were talking to remote daemon */
+    if (!virDomainObjIsActive(vm)) {
+        qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                        _("guest unexpectedly quit"));
+        goto cleanup;
+    }
+
     dom_xml = qemudVMDumpXML(driver, vm,
                              VIR_DOMAIN_XML_SECURE |
                              VIR_DOMAIN_XML_UPDATE_CPU);