qemu: Don't use query-migrate on destination

When migration fails, we need to poke QEMU monitor to check for a reason
of the failure. We did this using query-migrate QMP command, which is
not supposed to return any meaningful result on the destination side.
Thus if the monitor was still functional when we detected the migration
failure, parsing the answer from query-migrate always failed with the
following error message:

    "info migration reply was missing return status"

This irrelevant message was then used as the reason for the migration
failure replacing any message we might have had.

Let's use harmless query-status for poking the monitor to make sure we
only get an error if the monitor connection is broken.

https://bugzilla.redhat.com/show_bug.cgi?id=1374613

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_domain.c

@@ -6127,3 +6127,23 @@ qemuDomainVcpuPersistOrder(virDomainDefPtr def)
         }
     }
 }
+
+
+int
+qemuDomainCheckMonitor(virQEMUDriverPtr driver,
+                       virDomainObjPtr vm,
+                       qemuDomainAsyncJob asyncJob)
+{
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    int ret;
+
+    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
+        return -1;
+
+    ret = qemuMonitorCheck(priv->mon);
+
+    if (qemuDomainObjExitMonitor(driver, vm) < 0)
+        return -1;
+
+    return ret;
+}

src/qemu/qemu_domain.h

@@ -728,4 +728,8 @@ bool qemuDomainVcpuHotplugIsInOrder(virDomainDefPtr def)
 void qemuDomainVcpuPersistOrder(virDomainDefPtr def)
     ATTRIBUTE_NONNULL(1);
 
+int qemuDomainCheckMonitor(virQEMUDriverPtr driver,
+                           virDomainObjPtr vm,
+                           qemuDomainAsyncJob asyncJob);
+
 #endif /* __QEMU_DOMAIN_H__ */

src/qemu/qemu_migration.c

@@ -6208,14 +6208,10 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
     }
 
     if (retcode != 0) {
-        qemuDomainJobInfo info;
-
         /* Check for a possible error on the monitor in case Finish was called
          * earlier than monitor EOF handler got a chance to process the error
          */
-        qemuMigrationFetchJobStatus(driver, vm,
-                                    QEMU_ASYNC_JOB_MIGRATION_IN,
-                                    &info);
+        qemuDomainCheckMonitor(driver, vm, QEMU_ASYNC_JOB_MIGRATION_IN);
         goto endjob;
     }
 

src/qemu/qemu_monitor.c

@@ -1616,6 +1616,14 @@ qemuMonitorStopCPUs(qemuMonitorPtr mon)
 }
 
 
+int
+qemuMonitorCheck(qemuMonitorPtr mon)
+{
+    bool running;
+    return qemuMonitorGetStatus(mon, &running, NULL);
+}
+
+
 int
 qemuMonitorGetStatus(qemuMonitorPtr mon,
                      bool *running,

src/qemu/qemu_monitor.h

@@ -382,6 +382,7 @@ typedef enum {
 VIR_ENUM_DECL(qemuMonitorVMStatus)
 int qemuMonitorVMStatusToPausedReason(const char *status);
 
+int qemuMonitorCheck(qemuMonitorPtr mon);
 int qemuMonitorGetStatus(qemuMonitorPtr mon,
                          bool *running,
                          virDomainPausedReason *reason)