[Qemu-devel] [PATCH 1/3] python/qemu: Allow to launch the VM without qmp

[Wainer dos Santos Moschetta <wainersm@redhat.com>]

QEMUMachine launches the VM with a monitor enabled, afterwards
a qmp connection is attempted on _post_launch(). In case
the QEMU process exits with an error, qmp.accept() reaches
timeout and raises an exception.

But sometimes you don't need that monitor. As an example,
when a test launches the VM expecting its immediate crash,
and only intend to check the process's return code. In this
case the fact that launch() tries to establish the qmp
connection (ending up in an exception) is troublesome.

So this patch adds the set_qmp_monitor() that allow to
launch the VM without creating the monitor machinery.

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
---
 python/qemu/__init__.py | 72 +++++++++++++++++++++++++++--------------
 1 file changed, 48 insertions(+), 24 deletions(-)

diff --git a/python/qemu/__init__.py b/python/qemu/__init__.py
index dbaf8a5311..dd577e9446 100644
--- a/python/qemu/__init__.py
+++ b/python/qemu/__init__.py
@@ -113,6 +113,7 @@ class QEMUMachine(object):
         self._events = []
         self._iolog = None
         self._socket_scm_helper = socket_scm_helper
+        self._qmp_set = True   # Enable QMP monitor by default.
         self._qmp = None
         self._qemu_full_args = None
         self._test_dir = test_dir
@@ -227,15 +228,7 @@ class QEMUMachine(object):
                 self._iolog = iolog.read()
 
     def _base_args(self):
-        if isinstance(self._monitor_address, tuple):
-            moncdev = "socket,id=mon,host=%s,port=%s" % (
-                self._monitor_address[0],
-                self._monitor_address[1])
-        else:
-            moncdev = 'socket,id=mon,path=%s' % self._vm_monitor
-        args = ['-chardev', moncdev,
-                '-mon', 'chardev=mon,mode=control',
-                '-display', 'none', '-vga', 'none']
+        args = ['-display', 'none', '-vga', 'none']
         if self._machine is not None:
             args.extend(['-machine', self._machine])
         if self._console_set:
@@ -249,23 +242,33 @@ class QEMUMachine(object):
             else:
                 device = '%s,chardev=console' % self._console_device_type
                 args.extend(['-device', device])
+        if self._qmp_set:
+            if isinstance(self._monitor_address, tuple):
+                moncdev = "socket,id=mon,host=%s,port=%s" % (
+                    self._monitor_address[0],
+                    self._monitor_address[1])
+            else:
+                moncdev = 'socket,id=mon,path=%s' % self._vm_monitor
+            args.extend(['-chardev', moncdev, '-mon', 'chardev=mon,mode=control'])
+
         return args
 
     def _pre_launch(self):
         self._temp_dir = tempfile.mkdtemp(dir=self._test_dir)
-        if self._monitor_address is not None:
-            self._vm_monitor = self._monitor_address
-        else:
-            self._vm_monitor = os.path.join(self._temp_dir,
-                                            self._name + "-monitor.sock")
         self._qemu_log_path = os.path.join(self._temp_dir, self._name + ".log")
         self._qemu_log_file = open(self._qemu_log_path, 'wb')
 
-        self._qmp = qmp.QEMUMonitorProtocol(self._vm_monitor,
-                                            server=True)
-
+        if self._qmp_set:
+            if self._monitor_address is not None:
+                self._vm_monitor = self._monitor_address
+            else:
+                self._vm_monitor = os.path.join(self._temp_dir,
+                                            self._name + "-monitor.sock")
+            self._qmp = qmp.QEMUMonitorProtocol(self._vm_monitor,
+                                                    server=True)
     def _post_launch(self):
-        self._qmp.accept()
+        if self._qmp:
+            self._qmp.accept()
 
     def _post_shutdown(self):
         if self._qemu_log_file is not None:
@@ -328,7 +331,8 @@ class QEMUMachine(object):
         Wait for the VM to power off
         """
         self._popen.wait()
-        self._qmp.close()
+        if self._qmp:
+            self._qmp.close()
         self._load_io_log()
         self._post_shutdown()
 
@@ -337,11 +341,14 @@ class QEMUMachine(object):
         Terminate the VM and clean up
         """
         if self.is_running():
-            try:
-                self._qmp.cmd('quit')
-                self._qmp.close()
-            except:
-                self._popen.kill()
+            if self._qmp:
+                try:
+                    self._qmp.cmd('quit')
+                    self._qmp.close()
+                except:
+                    self._popen.kill()
+            else:
+                self._popen.terminate()
             self._popen.wait()
 
         self._load_io_log()
@@ -358,6 +365,23 @@ class QEMUMachine(object):
 
         self._launched = False
 
+    def set_qmp_monitor(self, disabled=False, monitor_address=None):
+        """
+        Set the QMP monitor.
+
+        @param disabled: if True, qmp monitor options will be removed from the
+                         base arguments of the resulting QEMU command line.
+        @param monitor_address: address for the QMP monitor.
+        @note: call this function before launch().
+        """
+        if disabled:
+            self._qmp_set = False
+            self._qmp = None
+        else:
+            self._qmp_set = True
+            if monitor_address:
+                self._monitor_address = monitor_address
+
     def qmp(self, cmd, conv_keys=True, **args):
         """
         Invoke a QMP command and return the response dict
-- 
2.21.0