Add support for saving VM state after test failure

client/common_lib/utils.py

Index: client/common_lib/utils.py
diff --git a/client/common_lib/utils.py b/client/common_lib/utils.py
index 47f3cb4c2e11d32a7331f6d12fbc448a6ee09b7f..caba7a8a32f2fab18d1a08a2711262b2152f7f71 100644
--- a/client/common_lib/utils.py
+++ b/client/common_lib/utils.py
@@ -2,7 +2,7 @@
 # Copyright 2008 Google Inc. Released under the GPL v2
 
 import os, pickle, random, re, resource, select, shutil, signal, StringIO
-import socket, struct, subprocess, sys, time, textwrap, urlparse
+import socket, struct, subprocess, sys, time, textwrap, urlparse, platform
 import warnings, smtplib, logging, urllib2
 from threading import Thread, Event
 try:
@@ -1708,3 +1708,26 @@ def get_unused_port():
         # Check if this port is unused on the other protocol.
         if port and try_bind(port, socket.SOCK_DGRAM, socket.IPPROTO_UDP):
             return port
+
+
+def save_vm_state(checkpoint):
+    """Saves the current state of the virtual machine
+
+    This function is a NOOP if the test is not running under a virtual machine
+    with the USB serial port redirected.
+
+    Arguments:
+      checkpoint - Name used to identify this state
+
+    Returns:
+      None
+    """
+    # The QEMU monitor has been redirected to the guest serial port located at
+    # /dev/ttyUSB0. To save the state of the VM, we just send the 'savevm'
+    # command to the serial port.
+    proc = platform.processor()
+    if proc.find('QEMU') >= 0 and os.path.exists('/dev/ttyUSB0'):
+        logging.info('Saving VM state "%s"' % checkpoint)
+        serial = open('/dev/ttyUSB0', 'w')
+        serial.write("savevm %s\r\n" % checkpoint)
+        logging.info('Done saving VM state "%s"' % checkpoint)