qemu: migration: Check domain live state after exitting the monitor

In qemuMigrationToFile we enter the monitor multiple times and don't
check if the VM is still alive after returning form the monitor. Add the
checks to skip pieces of code in case the VM crashes while saving it's
state.

src/qemu/qemu_migration.c

@@ -4731,6 +4731,13 @@ qemuMigrationToFile(virQEMUDriverPtr driver, virDomainObjPtr vm,
         qemuDomainObjExitMonitor(driver, vm);
     }
 
+    if (!virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("guest unexpectedly quit"));
+        /* nothing to tear down */
+        return -1;
+    }
+
     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATE_QEMU_FD) &&
         (!compressor || pipe(pipeFD) == 0)) {
         /* All right! We can use fd migration, which means that qemu
@@ -4818,6 +4825,12 @@ qemuMigrationToFile(virQEMUDriverPtr driver, virDomainObjPtr vm,
     }
     qemuDomainObjExitMonitor(driver, vm);
 
+    if (!virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("guest unexpectedly quit"));
+        goto cleanup;
+    }
+
     if (rc < 0)
         goto cleanup;
 
@@ -4827,7 +4840,8 @@ qemuMigrationToFile(virQEMUDriverPtr driver, virDomainObjPtr vm,
         if (rc == -2) {
             orig_err = virSaveLastError();
             virCommandAbort(cmd);
-            if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
+            if (virDomainObjIsActive(vm) &&
+                qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
                 qemuMonitorMigrateCancel(priv->mon);
                 qemuDomainObjExitMonitor(driver, vm);
             }
@@ -4845,7 +4859,8 @@ qemuMigrationToFile(virQEMUDriverPtr driver, virDomainObjPtr vm,
         orig_err = virSaveLastError();
 
     /* Restore max migration bandwidth */
-    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
+    if (virDomainObjIsActive(vm) &&
+        qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) == 0) {
         qemuMonitorSetMigrationSpeed(priv->mon, saveMigBandwidth);
         priv->migMaxBandwidth = saveMigBandwidth;
         qemuDomainObjExitMonitor(driver, vm);