1 files changed, 351 insertions, 147 deletions
diff --git a/src/python/m5/config.py b/src/python/m5/config.py
index 1e25e0d09..6f2873d40 100644
--- a/src/python/m5/config.py
+++ b/src/python/m5/config.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2004-2005 The Regents of The University of Michigan
+# Copyright (c) 2004-2006 The Regents of The University of Michigan
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -23,12 +23,14 @@
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# Authors: Steve Reinhardt
+#          Nathan Binkert
 
-from __future__ import generators
-import os, re, sys, types, inspect
+import os, re, sys, types, inspect, copy
 
 import m5
-panic = m5.panic
+from m5 import panic, cc_main
 from convert import *
 from multidict import multidict
 
@@ -82,60 +84,24 @@ class Singleton(type):
 #
 # Once a set of Python objects have been instantiated in a hierarchy,
 # calling 'instantiate(obj)' (where obj is the root of the hierarchy)
-# will generate a .ini file.  See simple-4cpu.py for an example
-# (corresponding to m5-test/simple-4cpu.ini).
+# will generate a .ini file.
 #
 #####################################################################
 
-#####################################################################
-#
-# ConfigNode/SimObject classes
-#
-# The Python class hierarchy rooted by ConfigNode (which is the base
-# class of SimObject, which in turn is the base class of all other M5
-# SimObject classes) has special attribute behavior.  In general, an
-# object in this hierarchy has three categories of attribute-like
-# things:
-#
-# 1. Regular Python methods and variables.  These must start with an
-# underscore to be treated normally.
-#
-# 2. SimObject parameters.  These values are stored as normal Python
-# attributes, but all assignments to these attributes are checked
-# against the pre-defined set of parameters stored in the class's
-# _params dictionary.  Assignments to attributes that do not
-# correspond to predefined parameters, or that are not of the correct
-# type, incur runtime errors.
+# dict to look up SimObjects based on path
+instanceDict = {}
+
+#############################
 #
-# 3. Hierarchy children.  The child nodes of a ConfigNode are stored
-# in the node's _children dictionary, but can be accessed using the
-# Python attribute dot-notation (just as they are printed out by the
-# simulator).  Children cannot be created using attribute assigment;
-# they must be added by specifying the parent node in the child's
-# constructor or using the '+=' operator.
-
-# The SimObject parameters are the most complex, for a few reasons.
-# First, both parameter descriptions and parameter values are
-# inherited.  Thus parameter description lookup must go up the
-# inheritance chain like normal attribute lookup, but this behavior
-# must be explicitly coded since the lookup occurs in each class's
-# _params attribute.  Second, because parameter values can be set
-# on SimObject classes (to implement default values), the parameter
-# checking behavior must be enforced on class attribute assignments as
-# well as instance attribute assignments.  Finally, because we allow
-# class specialization via inheritance (e.g., see the L1Cache class in
-# the simple-4cpu.py example), we must do parameter checking even on
-# class instantiation.  To provide all these features, we use a
-# metaclass to define most of the SimObject parameter behavior for
-# this class hierarchy.
+# Utility methods
 #
-#####################################################################
+#############################
 
 def isSimObject(value):
     return isinstance(value, SimObject)
 
-def isSimObjSequence(value):
-    if not isinstance(value, (list, tuple)):
+def isSimObjectSequence(value):
+    if not isinstance(value, (list, tuple)) or len(value) == 0:
         return False
 
     for val in value:
@@ -144,48 +110,76 @@ def isSimObjSequence(value):
 
     return True
 
+def isSimObjectOrSequence(value):
+    return isSimObject(value) or isSimObjectSequence(value)
+
 def isNullPointer(value):
     return isinstance(value, NullSimObject)
 
-# The metaclass for ConfigNode (and thus for everything that derives
-# from ConfigNode, including SimObject).  This class controls how new
-# classes that derive from ConfigNode are instantiated, and provides
-# inherited class behavior (just like a class controls how instances
-# of that class are instantiated, and provides inherited instance
-# behavior).
+# Apply method to object.
+# applyMethod(obj, 'meth', <args>) is equivalent to obj.meth(<args>)
+def applyMethod(obj, meth, *args, **kwargs):
+    return getattr(obj, meth)(*args, **kwargs)
+
+# If the first argument is an (non-sequence) object, apply the named
+# method with the given arguments.  If the first argument is a
+# sequence, apply the method to each element of the sequence (a la
+# 'map').
+def applyOrMap(objOrSeq, meth, *args, **kwargs):
+    if not isinstance(objOrSeq, (list, tuple)):
+        return applyMethod(objOrSeq, meth, *args, **kwargs)
+    else:
+        return [applyMethod(o, meth, *args, **kwargs) for o in objOrSeq]
+
+
+# The metaclass for SimObject.  This class controls how new classes
+# that derive from SimObject are instantiated, and provides inherited
+# class behavior (just like a class controls how instances of that
+# class are instantiated, and provides inherited instance behavior).
 class MetaSimObject(type):
     # Attributes that can be set only at initialization time
     init_keywords = { 'abstract' : types.BooleanType,
                       'type' : types.StringType }
     # Attributes that can be set any time
-    keywords = { 'check' : types.FunctionType,
-                 'children' : types.ListType }
+    keywords = { 'check' : types.FunctionType }
 
     # __new__ is called before __init__, and is where the statements
     # in the body of the class definition get loaded into the class's
-    # __dict__.  We intercept this to filter out parameter assignments
+    # __dict__.  We intercept this to filter out parameter & port assignments
     # and only allow "private" attributes to be passed to the base
     # __new__ (starting with underscore).
     def __new__(mcls, name, bases, dict):
-        # Copy "private" attributes (including special methods such as __new__)
-        # to the official dict.  Everything else goes in _init_dict to be
+        # Copy "private" attributes, functions, and classes to the
+        # official dict.  Everything else goes in _init_dict to be
         # filtered in __init__.
         cls_dict = {}
+        value_dict = {}
         for key,val in dict.items():
-            if key.startswith('_'):
+            if key.startswith('_') or isinstance(val, (types.FunctionType,
+                                                       types.TypeType)):
                 cls_dict[key] = val
-                del dict[key]
-        cls_dict['_init_dict'] = dict
+            else:
+                # must be a param/port setting
+                value_dict[key] = val
+        cls_dict['_value_dict'] = value_dict
         return super(MetaSimObject, mcls).__new__(mcls, name, bases, cls_dict)
 
-    # initialization
+    # subclass initialization
     def __init__(cls, name, bases, dict):
+        # calls type.__init__()... I think that's a no-op, but leave
+        # it here just in case it's not.
         super(MetaSimObject, cls).__init__(name, bases, dict)
 
         # initialize required attributes
-        cls._params = multidict()
-        cls._values = multidict()
-        cls._anon_subclass_counter = 0
+
+        # class-only attributes
+        cls._params = multidict() # param descriptions
+        cls._ports = multidict()  # port descriptions
+
+        # class or instance attributes
+        cls._values = multidict()   # param values
+        cls._port_map = multidict() # port bindings
+        cls._instantiated = False # really instantiated, cloned, or subclassed
 
         # We don't support multiple inheritance.  If you want to, you
         # must fix multidict to deal with it properly.
@@ -194,35 +188,34 @@ class MetaSimObject(type):
 
         base = bases[0]
 
+        # Set up general inheritance via multidicts.  A subclass will
+        # inherit all its settings from the base class.  The only time
+        # the following is not true is when we define the SimObject
+        # class itself (in which case the multidicts have no parent).
         if isinstance(base, MetaSimObject):
             cls._params.parent = base._params
+            cls._ports.parent = base._ports
             cls._values.parent = base._values
-
-            # If your parent has a value in it that's a config node, clone
-            # it.  Do this now so if we update any of the values'
-            # attributes we are updating the clone and not the original.
-            for key,val in base._values.iteritems():
-
-                # don't clone if (1) we're about to overwrite it with
-                # a local setting or (2) we've already cloned a copy
-                # from an earlier (more derived) base
-                if cls._init_dict.has_key(key) or cls._values.has_key(key):
-                    continue
-
-                if isSimObject(val):
-                    cls._values[key] = val()
-                elif isSimObjSequence(val) and len(val):
-                    cls._values[key] = [ v() for v in val ]
-
-        # now process remaining _init_dict items
-        for key,val in cls._init_dict.items():
-            if isinstance(val, (types.FunctionType, types.TypeType)):
-                type.__setattr__(cls, key, val)
-
+            cls._port_map.parent = base._port_map
+            # mark base as having been subclassed
+            base._instantiated = True
+
+        # Now process the _value_dict items.  They could be defining
+        # new (or overriding existing) parameters or ports, setting
+        # class keywords (e.g., 'abstract'), or setting parameter
+        # values or port bindings.  The first 3 can only be set when
+        # the class is defined, so we handle them here.  The others
+        # can be set later too, so just emulate that by calling
+        # setattr().
+        for key,val in cls._value_dict.items():
             # param descriptions
-            elif isinstance(val, ParamDesc):
+            if isinstance(val, ParamDesc):
                 cls._new_param(key, val)
 
+            # port objects
+            elif isinstance(val, Port):
+                cls._ports[key] = val
+
             # init-time-only keywords
             elif cls.init_keywords.has_key(key):
                 cls._set_keyword(key, val, cls.init_keywords[key])
@@ -256,10 +249,19 @@ class MetaSimObject(type):
             cls._set_keyword(attr, value, cls.keywords[attr])
             return
 
-        # must be SimObject param
+        if cls._ports.has_key(attr):
+            self._ports[attr].connect(self, attr, value)
+            return
+
+        if isSimObjectOrSequence(value) and cls._instantiated:
+            raise RuntimeError, \
+                  "cannot set SimObject parameter '%s' after\n" \
+                  "    class %s has been instantiated or subclassed" \
+                  % (attr, cls.__name__)
+
+        # check for param
         param = cls._params.get(attr, None)
         if param:
-            # It's ok: set attribute by delegating to 'object' class.
             try:
                 cls._values[attr] = param.convert(value)
             except Exception, e:
@@ -267,12 +269,12 @@ class MetaSimObject(type):
                       (e, cls.__name__, attr, value)
                 e.args = (msg, )
                 raise
-        # I would love to get rid of this
-        elif isSimObject(value) or isSimObjSequence(value):
-           cls._values[attr] = value
+        elif isSimObjectOrSequence(value):
+            # if RHS is a SimObject, it's an implicit child assignment
+            cls._values[attr] = value
         else:
             raise AttributeError, \
-                  "Class %s has no parameter %s" % (cls.__name__, attr)
+                  "Class %s has no parameter \'%s\'" % (cls.__name__, attr)
 
     def __getattr__(cls, attr):
         if cls._values.has_key(attr):
@@ -281,7 +283,7 @@ class MetaSimObject(type):
         raise AttributeError, \
               "object '%s' has no attribute '%s'" % (cls.__name__, attr)
 
-# The ConfigNode class is the root of the special hierarchy.  Most of
+# The SimObject class is the root of the special hierarchy.  Most of
 # the code in this class deals with the configuration hierarchy itself
 # (parent/child node relationships).
 class SimObject(object):
@@ -289,29 +291,79 @@ class SimObject(object):
     # get this metaclass.
     __metaclass__ = MetaSimObject
 
-    def __init__(self, _value_parent = None, **kwargs):
+    # Initialize new instance.  For objects with SimObject-valued
+    # children, we need to recursively clone the classes represented
+    # by those param values as well in a consistent "deep copy"-style
+    # fashion.  That is, we want to make sure that each instance is
+    # cloned only once, and that if there are multiple references to
+    # the same original object, we end up with the corresponding
+    # cloned references all pointing to the same cloned instance.
+    def __init__(self, **kwargs):
+        ancestor = kwargs.get('_ancestor')
+        memo_dict = kwargs.get('_memo')
+        if memo_dict is None:
+            # prepare to memoize any recursively instantiated objects
+            memo_dict = {}
+        elif ancestor:
+            # memoize me now to avoid problems with recursive calls
+            memo_dict[ancestor] = self
+
+        if not ancestor:
+            ancestor = self.__class__
+        ancestor._instantiated = True
+
+        # initialize required attributes
+        self._parent = None
         self._children = {}
-        if _value_parent and type(_value_parent) != type(self):
-            # this was called as a type conversion rather than a clone
-            raise TypeError, "Cannot convert %s to %s" % \
-                  (_value_parent.__class__.__name__, self.__class__.__name__)
-        if not _value_parent:
-            _value_parent = self.__class__
-        # clone values
-        self._values = multidict(_value_parent._values)
-        for key,val in _value_parent._values.iteritems():
+        self._ccObject = None  # pointer to C++ object
+        self._instantiated = False # really "cloned"
+
+        # Inherit parameter values from class using multidict so
+        # individual value settings can be overridden.
+        self._values = multidict(ancestor._values)
+        # clone SimObject-valued parameters
+        for key,val in ancestor._values.iteritems():
             if isSimObject(val):
-                setattr(self, key, val())
-            elif isSimObjSequence(val) and len(val):
-                setattr(self, key, [ v() for v in val ])
+                setattr(self, key, val(_memo=memo_dict))
+            elif isSimObjectSequence(val) and len(val):
+                setattr(self, key, [ v(_memo=memo_dict) for v in val ])
+        # clone port references.  no need to use a multidict here
+        # since we will be creating new references for all ports.
+        self._port_map = {}
+        for key,val in ancestor._port_map.iteritems():
+            self._port_map[key] = applyOrMap(val, 'clone', memo_dict)
         # apply attribute assignments from keyword args, if any
         for key,val in kwargs.iteritems():
             setattr(self, key, val)
 
+    # "Clone" the current instance by creating another instance of
+    # this instance's class, but that inherits its parameter values
+    # and port mappings from the current instance.  If we're in a
+    # "deep copy" recursive clone, check the _memo dict to see if
+    # we've already cloned this instance.
     def __call__(self, **kwargs):
-        return self.__class__(_value_parent = self, **kwargs)
+        memo_dict = kwargs.get('_memo')
+        if memo_dict is None:
+            # no memo_dict: must be top-level clone operation.
+            # this is only allowed at the root of a hierarchy
+            if self._parent:
+                raise RuntimeError, "attempt to clone object %s " \
+                      "not at the root of a tree (parent = %s)" \
+                      % (self, self._parent)
+            # create a new dict and use that.
+            memo_dict = {}
+            kwargs['_memo'] = memo_dict
+        elif memo_dict.has_key(self):
+            # clone already done & memoized
+            return memo_dict[self]
+        return self.__class__(_ancestor = self, **kwargs)
 
     def __getattr__(self, attr):
+        if self._ports.has_key(attr):
+            # return reference that can be assigned to another port
+            # via __setattr__
+            return self._ports[attr].makeRef(self, attr)
+
         if self._values.has_key(attr):
             return self._values[attr]
 
@@ -326,10 +378,19 @@ class SimObject(object):
             object.__setattr__(self, attr, value)
             return
 
+        if self._ports.has_key(attr):
+            # set up port connection
+            self._ports[attr].connect(self, attr, value)
+            return
+
+        if isSimObjectOrSequence(value) and self._instantiated:
+            raise RuntimeError, \
+                  "cannot set SimObject parameter '%s' after\n" \
+                  "    instance been cloned %s" % (attr, `self`)
+
         # must be SimObject param
         param = self._params.get(attr, None)
         if param:
-            # It's ok: set attribute by delegating to 'object' class.
             try:
                 value = param.convert(value)
             except Exception, e:
@@ -337,8 +398,7 @@ class SimObject(object):
                       (e, self.__class__.__name__, attr, value)
                 e.args = (msg, )
                 raise
-        # I would love to get rid of this
-        elif isSimObject(value) or isSimObjSequence(value):
+        elif isSimObjectOrSequence(value):
             pass
         else:
             raise AttributeError, "Class %s has no parameter %s" \
@@ -349,7 +409,7 @@ class SimObject(object):
 
         if isSimObject(value):
             value.set_path(self, attr)
-        elif isSimObjSequence(value):
+        elif isSimObjectSequence(value):
             value = SimObjVector(value)
             [v.set_path(self, "%s%d" % (attr, i)) for i,v in enumerate(value)]
 
@@ -376,13 +436,13 @@ class SimObject(object):
         self._children[name] = value
 
     def set_path(self, parent, name):
-        if not hasattr(self, '_parent'):
+        if not self._parent:
             self._parent = parent
             self._name = name
             parent.add_child(name, self)
 
     def path(self):
-        if not hasattr(self, '_parent'):
+        if not self._parent:
             return 'root'
         ppath = self._parent.path()
         if ppath == 'root':
@@ -423,6 +483,8 @@ class SimObject(object):
     def print_ini(self):
         print '[' + self.path() + ']'	# .ini section header
 
+        instanceDict[self.path()] = self
+
         if hasattr(self, 'type') and not isinstance(self, ParamContext):
             print 'type=%s' % self.type
 
@@ -454,6 +516,60 @@ class SimObject(object):
         for child in child_names:
             self._children[child].print_ini()
 
+    # Call C++ to create C++ object corresponding to this object and
+    # (recursively) all its children
+    def createCCObject(self):
+        self.getCCObject() # force creation
+        for child in self._children.itervalues():
+            child.createCCObject()
+
+    # Get C++ object corresponding to this object, calling C++ if
+    # necessary to construct it.  Does *not* recursively create
+    # children.
+    def getCCObject(self):
+        if not self._ccObject:
+            self._ccObject = -1 # flag to catch cycles in recursion
+            self._ccObject = cc_main.createSimObject(self.path())
+        elif self._ccObject == -1:
+            raise RuntimeError, "%s: recursive call to getCCObject()" \
+                  % self.path()
+        return self._ccObject
+
+    # Create C++ port connections corresponding to the connections in
+    # _port_map (& recursively for all children)
+    def connectPorts(self):
+        for portRef in self._port_map.itervalues():
+            applyOrMap(portRef, 'ccConnect')
+        for child in self._children.itervalues():
+            child.connectPorts()
+
+    def startQuiesce(self, quiesce_event, recursive):
+        count = 0
+        # ParamContexts don't serialize
+        if isinstance(self, SimObject) and not isinstance(self, ParamContext):
+            if self._ccObject.quiesce(quiesce_event):
+                count = 1
+        if recursive:
+            for child in self._children.itervalues():
+                count += child.startQuiesce(quiesce_event, True)
+        return count
+
+    def resume(self):
+        if isinstance(self, SimObject) and not isinstance(self, ParamContext):
+            self._ccObject.resume()
+        for child in self._children.itervalues():
+            child.resume()
+
+    def changeTiming(self, mode):
+        if isinstance(self, SimObject) and not isinstance(self, ParamContext):
+            self._ccObject.setMemoryMode(mode)
+        for child in self._children.itervalues():
+            child.changeTiming(mode)
+
+    def takeOverFrom(self, old_cpu):
+        cpu_ptr = cc_main.convertToBaseCPUPtr(old_cpu._ccObject)
+        self._ccObject.takeOverFrom(cpu_ptr)
+
     # generate output file for 'dot' to display as a pretty graph.
     # this code is currently broken.
     def outputDot(self, dot):
@@ -544,9 +660,9 @@ class BaseProxy(object):
 
         if self._search_up:
             while not done:
-                try: obj = obj._parent
-                except: break
-
+                obj = obj._parent
+                if not obj:
+                    break
                 result, done = self.find(obj)
 
         if not done:
@@ -662,16 +778,16 @@ Self = ProxyFactory(search_self = True, search_up = False)
 #
 # Parameter description classes
 #
-# The _params dictionary in each class maps parameter names to
-# either a Param or a VectorParam object.  These objects contain the
+# The _params dictionary in each class maps parameter names to either
+# a Param or a VectorParam object.  These objects contain the
 # parameter description string, the parameter type, and the default
-# value (loaded from the PARAM section of the .odesc files).  The
-# _convert() method on these objects is used to force whatever value
-# is assigned to the parameter to the appropriate type.
+# value (if any).  The convert() method on these objects is used to
+# force whatever value is assigned to the parameter to the appropriate
+# type.
 #
 # Note that the default values are loaded into the class's attribute
 # space when the parameter dictionary is initialized (in
-# MetaConfigNode._setparams()); after that point they aren't used.
+# MetaSimObject._new_param()); after that point they aren't used.
 #
 #####################################################################
 
@@ -725,7 +841,7 @@ class ParamDesc(object):
     def __getattr__(self, attr):
         if attr == 'ptype':
             try:
-                ptype = eval(self.ptype_str, m5.__dict__)
+                ptype = eval(self.ptype_str, m5.objects.__dict__)
                 if not isinstance(ptype, type):
                     panic("Param qualifier is not a type: %s" % self.ptype)
                 self.ptype = ptype
@@ -772,7 +888,7 @@ class VectorParamDesc(ParamDesc):
         if isinstance(value, (list, tuple)):
             # list: coerce each element into new list
             tmp_list = [ ParamDesc.convert(self, v) for v in value ]
-            if isSimObjSequence(tmp_list):
+            if isSimObjectSequence(tmp_list):
                 return SimObjVector(tmp_list)
             else:
                 return VectorParamValue(tmp_list)
@@ -794,7 +910,7 @@ class ParamFactory(object):
 
     # E.g., Param.Int(5, "number of widgets")
     def __call__(self, *args, **kwargs):
-        caller_frame = inspect.stack()[1][0]
+        caller_frame = inspect.currentframe().f_back
         ptype = None
         try:
             ptype = eval(self.ptype_str,
@@ -1066,7 +1182,10 @@ class EthernetAddr(ParamValue):
 
     def __str__(self):
         if self.value == NextEthernetAddr:
-            return self.addr
+            if hasattr(self, 'addr'):
+                return self.addr
+            else:
+                return "NextEthernetAddr (unresolved)"
         else:
             return self.value
 
@@ -1285,24 +1404,108 @@ MaxAddr = Addr.max
 MaxTick = Tick.max
 AllMemory = AddrRange(0, MaxAddr)
 
+
+#####################################################################
+#
+# Port objects
+#
+# Ports are used to interconnect objects in the memory system.
+#
 #####################################################################
 
-# The final hook to generate .ini files.  Called from configuration
-# script once config is built.
-def instantiate(root):
-    global ticks_per_sec
-    ticks_per_sec = float(root.clock.frequency)
-    root.print_ini()
-    noDot = True # temporary until we fix dot
-    if not noDot:
-       dot = pydot.Dot()
-       instance.outputDot(dot)
-       dot.orientation = "portrait"
-       dot.size = "8.5,11"
-       dot.ranksep="equally"
-       dot.rank="samerank"
-       dot.write("config.dot")
-       dot.write_ps("config.ps")
+# Port reference: encapsulates a reference to a particular port on a
+# particular SimObject.
+class PortRef(object):
+    def __init__(self, simobj, name, isVec):
+        assert(isSimObject(simobj))
+        self.simobj = simobj
+        self.name = name
+        self.index = -1
+        self.isVec = isVec # is this a vector port?
+        self.peer = None   # not associated with another port yet
+        self.ccConnected = False # C++ port connection done?
+
+    # Set peer port reference.  Called via __setattr__ as a result of
+    # a port assignment, e.g., "obj1.port1 = obj2.port2".
+    def setPeer(self, other):
+        if self.isVec:
+            curMap = self.simobj._port_map.get(self.name, [])
+            self.index = len(curMap)
+            curMap.append(other)
+        else:
+            curMap = self.simobj._port_map.get(self.name)
+            if curMap and not self.isVec:
+                print "warning: overwriting port", self.simobj, self.name
+            curMap = other
+        self.simobj._port_map[self.name] = curMap
+        self.peer = other
+
+    def clone(self, memo):
+        newRef = copy.copy(self)
+        assert(isSimObject(newRef.simobj))
+        newRef.simobj = newRef.simobj(_memo=memo)
+        # Tricky: if I'm the *second* PortRef in the pair to be
+        # cloned, then my peer is still in the middle of its clone
+        # method, and thus hasn't returned to its owner's
+        # SimObject.__init__ to get installed in _port_map.  As a
+        # result I have no way of finding the *new* peer object.  So I
+        # mark myself as "waiting" for my peer, and I let the *first*
+        # PortRef clone call set up both peer pointers after I return.
+        newPeer = newRef.simobj._port_map.get(self.name)
+        if newPeer:
+            if self.isVec:
+                assert(self.index != -1)
+                newPeer = newPeer[self.index]
+            # other guy is all set up except for his peer pointer
+            assert(newPeer.peer == -1) # peer must be waiting for handshake
+            newPeer.peer = newRef
+            newRef.peer = newPeer
+        else:
+            # other guy is in clone; just wait for him to do the work
+            newRef.peer = -1 # mark as waiting for handshake
+        return newRef
+
+    # Call C++ to create corresponding port connection between C++ objects
+    def ccConnect(self):
+        if self.ccConnected: # already done this
+            return
+        peer = self.peer
+        cc_main.connectPorts(self.simobj.getCCObject(), self.name, self.index,
+                             peer.simobj.getCCObject(), peer.name, peer.index)
+        self.ccConnected = True
+        peer.ccConnected = True
+
+# Port description object.  Like a ParamDesc object, this represents a
+# logical port in the SimObject class, not a particular port on a
+# SimObject instance.  The latter are represented by PortRef objects.
+class Port(object):
+    def __init__(self, desc):
+        self.desc = desc
+        self.isVec = False
+
+    # Generate a PortRef for this port on the given SimObject with the
+    # given name
+    def makeRef(self, simobj, name):
+        return PortRef(simobj, name, self.isVec)
+
+    # Connect an instance of this port (on the given SimObject with
+    # the given name) with the port described by the supplied PortRef
+    def connect(self, simobj, name, ref):
+        if not isinstance(ref, PortRef):
+            raise TypeError, \
+                  "assigning non-port reference port '%s'" % name
+        myRef = self.makeRef(simobj, name)
+        myRef.setPeer(ref)
+        ref.setPeer(myRef)
+
+# VectorPort description object.  Like Port, but represents a vector
+# of connections (e.g., as on a Bus).
+class VectorPort(Port):
+    def __init__(self, desc):
+        Port.__init__(self, desc)
+        self.isVec = True
+
+#####################################################################
 
 # __all__ defines the list of symbols that get exported when
 # 'from config import *' is invoked.  Try to keep this reasonably
@@ -1319,5 +1522,6 @@ __all__ = ['SimObject', 'ParamContext', 'Param', 'VectorParam',
            'NetworkBandwidth', 'MemoryBandwidth',
            'Range', 'AddrRange', 'MaxAddr', 'MaxTick', 'AllMemory',
            'Null', 'NULL',
-           'NextEthernetAddr', 'instantiate']
+           'NextEthernetAddr',
+           'Port', 'VectorPort']