Change the semantics of GetDomainPath so that it always succeeds, regardless of

whether a domain has been introduced to the store.  Added a separate message
XS_IS_DOMAIN_INTRODUCED and API for that (xs_is_domain_introduced) to determine
whether the domain has really been introduced.  This change means that the
tools can determine the correct domain path earlier in the domain creation
process, which is particularly a factor with live migration, as it allows us
to create the devices earlier in the process, and unpause the new domain before
performing the introduce.  Until recently we already had these features, but
the simplification of the interface between xend and xenstored caused breakage.

No longer clear out the domain path when a domain is introduced -- this was a
hack to work around the recent problematic semantics of GetDomainPath.

Do not write the contents of the info block to the store.  All the configuration
info is written to the /vm path, and anything else in the info block is either
dealt with explicitly or is ephemeral and has no place in the store.

Signed-off-by: Ewan Mellor <ewan@xensource.com>

tools/python/xen/lowlevel/xs/xs.c

@@ -795,11 +795,10 @@ static PyObject *xspy_close(PyObject *self, PyObject *args, PyObject *kwds)
 }
 
 #define xspy_get_domain_path_doc "\n"			\
-	"Return store path of domain.\n"		\
+	"Return store path of domain, whether or not the domain exists.\n" \
 	" domid [int]: domain id\n"			\
 	"\n"						\
 	"Returns: [string] domain store path.\n"	\
-	"         None if domid doesn't exist.\n"	\
 	"Raises RuntimeError on error.\n"		\
 	"\n"
 

tools/python/xen/xend/XendCheckpoint.py

@@ -144,6 +144,8 @@ def restore(xd, fd):
         if handler.store_mfn is None or handler.console_mfn is None:
             raise XendError('Could not read store/console MFN')
 
+        dominfo.unpause()
+
         dominfo.completeRestore(handler.store_mfn, handler.console_mfn)
 
         return dominfo

tools/python/xen/xend/XendDomainInfo.py

@@ -198,7 +198,7 @@ def recreate(xeninfo, priv):
         vm = XendDomainInfo(xeninfo, domid, dompath, True)
 
     except Exception, exn:
-        if True:
+        if priv:
             log.warn(str(exn))
 
         vm = XendDomainInfo(xeninfo, domid, dompath, True)
@@ -223,7 +223,9 @@ def restore(config):
     try:
         vm.construct()
         vm.storeVmDetails()
+        vm.createDevices()
         vm.createChannels()
+        vm.storeDomDetails()
         return vm
     except:
         vm.destroy()
@@ -337,8 +339,8 @@ def dom_get(dom):
         log.debug("domain_getinfo(%d) failed, ignoring: %s", dom, str(err))
     return None
 
-class XendDomainInfo:
 
+class XendDomainInfo:
 
     def __init__(self, info, domid = None, dompath = None, augment = False):
 
@@ -558,13 +560,13 @@ class XendDomainInfo:
 
     def completeRestore(self, store_mfn, console_mfn):
 
+        log.debug("XendDomainInfo.completeRestore")
+
         self.store_mfn = store_mfn
         self.console_mfn = console_mfn
 
         self.introduceDomain()
-        self.create_devices()
         self.storeDomDetails()
-        self.unpause()
         self.refreshShutdown()
 
 
@@ -597,10 +599,6 @@ class XendDomainInfo:
             'memory/target':      str(self.info['memory_KiB'])
             }
 
-        for (k, v) in self.info.items():
-            if v:
-                to_store[k] = str(v)
-
         def f(n, v):
             if v is not None:
                 to_store[n] = str(v)
@@ -1055,6 +1053,10 @@ class XendDomainInfo:
             raise VmError('Creating domain failed: name=%s' %
                           self.info['name'])
 
+        self.dompath = GetDomainPath(self.domid)
+
+        self.removeDom()
+
         # Set maximum number of vcpus in domain
         xc.domain_max_vcpus(self.domid, int(self.info['vcpus']))
 
@@ -1065,8 +1067,6 @@ class XendDomainInfo:
         assert self.store_port is not None
         
         IntroduceDomain(self.domid, self.store_mfn, self.store_port)
-        self.dompath = GetDomainPath(self.domid)
-        assert self.dompath
 
 
     def initDomain(self):
@@ -1105,7 +1105,7 @@ class XendDomainInfo:
 
         self.introduceDomain()
 
-        self.create_devices()
+        self.createDevices()
 
         self.info['start_time'] = time.time()
 
@@ -1209,23 +1209,21 @@ class XendDomainInfo:
             raise
 
 
-    def create_configured_devices(self):
-        for (n, c) in self.info['device']:
-            self.createDevice(n, c)
+    ## public:
 
-
-    def create_devices(self):
+    def createDevices(self):
         """Create the devices for a vm.
 
         @raise: VmError for invalid devices
         """
-        self.create_configured_devices()
+
+        for (n, c) in self.info['device']:
+            self.createDevice(n, c)
+
         if self.image:
             self.image.createDeviceModel()
 
 
-    ## public:
-
     def device_create(self, dev_config):
         """Create a new device.