diff --git a/tests/vm/basevm.py b/tests/vm/basevm.py
index 3b4403ddcb..ec92c8f105 100755
--- a/tests/vm/basevm.py
+++ b/tests/vm/basevm.py
@@ -32,15 +32,40 @@ import shutil
 import multiprocessing
 import traceback
 
-SSH_KEY = open(os.path.join(os.path.dirname(__file__),
-               "..", "keys", "id_rsa")).read()
-SSH_PUB_KEY = open(os.path.join(os.path.dirname(__file__),
-                   "..", "keys", "id_rsa.pub")).read()
-
+SSH_KEY_FILE = os.path.join(os.path.dirname(__file__),
+               "..", "keys", "id_rsa")
+SSH_PUB_KEY_FILE = os.path.join(os.path.dirname(__file__),
+                   "..", "keys", "id_rsa.pub")
+SSH_KEY = open(SSH_KEY_FILE).read()
+SSH_PUB_KEY = open(SSH_PUB_KEY_FILE).read()
+
+# This is the standard configuration.
+# Any or all of these can be overridden by
+# passing in a config argument to the VM constructor.
+DEFAULT_CONFIG = {
+    'cpu'             : "max",
+    'machine'         : 'pc',
+    'guest_user'      : "qemu",
+    'guest_pass'      : "qemupass",
+    'root_pass'       : "qemupass",
+    'ssh_key_file'    : SSH_KEY_FILE,
+    'ssh_pub_key_file': SSH_PUB_KEY_FILE,
+    'memory'          : "4G",
+    'extra_args'      : [],
+    'dns'             : "",
+    'ssh_port'        : 0,
+    'install_cmds'    : "",
+    'boot_dev_type'   : "block",
+    'ssh_timeout'     : 1,
+}
+BOOT_DEVICE = {
+    'block' :  "-drive file={},if=none,id=drive0,cache=writeback "\
+               "-device virtio-blk,drive=drive0,bootindex=0",
+    'scsi'  :  "-device virtio-scsi-device,id=scsi "\
+               "-drive file={},format=raw,if=none,id=hd0 "\
+               "-device scsi-hd,drive=hd0,bootindex=0",
+}
 class BaseVM(object):
-    GUEST_USER = "qemu"
-    GUEST_PASS = "qemupass"
-    ROOT_PASS = "qemupass"
 
     envvars = [
         "https_proxy",
@@ -59,19 +84,26 @@ class BaseVM(object):
     poweroff = "poweroff"
     # enable IPv6 networking
     ipv6 = True
-    def __init__(self, debug=False, vcpus=None):
+    def __init__(self, debug=False, vcpus=None, config=None):
         self._guest = None
+        # Allow input config to override defaults.
+        self._config = DEFAULT_CONFIG.copy()
+        if config != None:
+            self._config.update(config)
         self._tmpdir = os.path.realpath(tempfile.mkdtemp(prefix="vm-test-",
                                                          suffix=".tmp",
                                                          dir="."))
         atexit.register(shutil.rmtree, self._tmpdir)
-
+        self._config['ssh_key'] = \
+            open(self._config['ssh_key_file']).read().rstrip()
+        self._config['ssh_pub_key'] = \
+            open(self._config['ssh_pub_key_file']).read().rstrip()
         self._ssh_key_file = os.path.join(self._tmpdir, "id_rsa")
-        open(self._ssh_key_file, "w").write(SSH_KEY)
+        open(self._ssh_key_file, "w").write(self._config['ssh_key'])
         subprocess.check_call(["chmod", "600", self._ssh_key_file])
 
         self._ssh_pub_key_file = os.path.join(self._tmpdir, "id_rsa.pub")
-        open(self._ssh_pub_key_file, "w").write(SSH_PUB_KEY)
+        open(self._ssh_pub_key_file, "w").write(self._config['ssh_pub_key'])
 
         self.debug = debug
         self._stderr = sys.stderr
@@ -80,11 +112,14 @@ class BaseVM(object):
             self._stdout = sys.stdout
         else:
             self._stdout = self._devnull
+        netdev = "user,id=vnet,hostfwd=:127.0.0.1:{}-:22"
         self._args = [ \
-            "-nodefaults", "-m", "4G",
-            "-cpu", "max",
-            "-netdev", "user,id=vnet,hostfwd=:127.0.0.1:0-:22" +
-                       (",ipv6=no" if not self.ipv6 else ""),
+            "-nodefaults", "-m", self._config['memory'],
+            "-cpu", self._config['cpu'],
+            "-netdev",
+            netdev.format(self._config['ssh_port']) +
+            (",ipv6=no" if not self.ipv6 else "") +
+            (",dns=" + self._config['dns'] if self._config['dns'] else ""),
             "-device", "virtio-net-pci,netdev=vnet",
             "-vnc", "127.0.0.1:0,to=20"]
         if vcpus and vcpus > 1:
@@ -95,6 +130,25 @@ class BaseVM(object):
             logging.info("KVM not available, not using -enable-kvm")
         self._data_args = []
 
+    def wait_boot(self, wait_string=None):
+        """Wait for the standard string we expect
+           on completion of a normal boot.
+           The user can also choose to override with an
+           alternate string to wait for."""
+        if wait_string is None:
+            if self.login_prompt is None:
+                raise Exception("self.login_prompt not defined")
+            wait_string = self.login_prompt
+        self.console_init()
+        self.console_wait(wait_string)
+
+    def __getattr__(self, name):
+        # Support direct access to config by key.
+        # for example, access self._config['cpu'] by self.cpu
+        if name.lower() in self._config.keys():
+            return self._config[name.lower()]
+        return object.__getattribute__(self, name)
+
     def _download_with_cache(self, url, sha256sum=None, sha512sum=None):
         def check_sha256sum(fname):
             if not sha256sum:
@@ -126,7 +180,8 @@ class BaseVM(object):
                    "-t",
                    "-o", "StrictHostKeyChecking=no",
                    "-o", "UserKnownHostsFile=" + os.devnull,
-                   "-o", "ConnectTimeout=1",
+                   "-o",
+                   "ConnectTimeout={}".format(self._config["ssh_timeout"]),
                    "-p", self.ssh_port, "-i", self._ssh_key_file]
         # If not in debug mode, set ssh to quiet mode to
         # avoid printing the results of commands.
@@ -176,15 +231,15 @@ class BaseVM(object):
                             "virtio-blk,drive=%s,serial=%s,bootindex=1" % (name, name)]
 
     def boot(self, img, extra_args=[]):
-        args = self._args + [
-            "-device", "VGA",
-            "-drive", "file=%s,if=none,id=drive0,cache=writeback" % img,
-            "-device", "virtio-blk,drive=drive0,bootindex=0"]
-        args += self._data_args + extra_args
+        boot_dev = BOOT_DEVICE[self._config['boot_dev_type']]
+        boot_params = boot_dev.format(img)
+        args = self._args + boot_params.split(' ')
+        args += self._data_args + extra_args + self._config['extra_args']
+        args += ["-device", "VGA"]
         logging.debug("QEMU args: %s", " ".join(args))
         qemu_bin = os.environ.get("QEMU", "qemu-system-" + self.arch)
         guest = QEMUMachine(binary=qemu_bin, args=args)
-        guest.set_machine('pc')
+        guest.set_machine(self._config['machine'])
         guest.set_console()
         try:
             guest.launch()
@@ -331,7 +386,6 @@ class BaseVM(object):
 
     def shutdown(self):
         self._guest.shutdown()
-
     def wait(self):
         self._guest.wait()
 
@@ -379,15 +433,17 @@ def parse_args(vmcls):
     parser.disable_interspersed_args()
     return parser.parse_args()
 
-def main(vmcls):
+def main(vmcls, config=None):
     try:
+        if config == None:
+            config = {}
         args, argv = parse_args(vmcls)
         if not argv and not args.build_qemu and not args.build_image:
             print("Nothing to do?")
             return 1
         logging.basicConfig(level=(logging.DEBUG if args.debug
                                    else logging.WARN))
-        vm = vmcls(debug=args.debug, vcpus=args.jobs)
+        vm = vmcls(debug=args.debug, vcpus=args.jobs, config=config)
         if args.build_image:
             if os.path.exists(args.image) and not args.force:
                 sys.stderr.writelines(["Image file exists: %s\n" % args.image,
