core: do not assume that libvirt domain is always defined

Define it only when really needed:
 - during VM creation - to generate UUID
 - just before VM startup

As a consequence we must handle possible exception when accessing
vm.libvirt_domain. It would be a good idea to make this field private in
the future. It isn't possible for now because block_* are external for
QubesVm class.

This hopefully fixes race condition when Qubes Manager tries to access
libvirt_domain (using some QubesVm.*) at the same time as other tool is
removing the domain. Additionally if Qubes Manage would loose that race, it could
define the domain again leaving some unused libvirt domain (blocking
that domain name for future use).

core-modules/000QubesVm.py

@@ -660,9 +660,14 @@ class QubesVm(object):
 
     @property
     def xid(self):
-        if self.libvirt_domain is None:
+        try:
-            return -1
             return self.libvirt_domain.ID()
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return -1
+            else:
+                raise
+
 
     def get_xid(self):
         # obsoleted
@@ -670,34 +675,17 @@ class QubesVm(object):
 
     def _update_libvirt_domain(self):
         domain_config = self.create_config_file()
-        try:
         self._libvirt_domain = vmm.libvirt_conn.defineXML(domain_config)
         self.uuid = uuid.UUID(bytes=self._libvirt_domain.UUID())
-        except libvirt.libvirtError:
-            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
-                # accept the fact that libvirt doesn't know anything about this
-                # domain...
-                pass
-            else:
-                raise
 
     @property
     def libvirt_domain(self):
-        if self._libvirt_domain is not None:
+        if self._libvirt_domain is None:
-            return self._libvirt_domain
-
-        try:
             if self.uuid is not None:
                 self._libvirt_domain = vmm.libvirt_conn.lookupByUUID(self.uuid.bytes)
             else:
                 self._libvirt_domain = vmm.libvirt_conn.lookupByName(self.name)
                 self.uuid = uuid.UUID(bytes=self._libvirt_domain.UUID())
-        except libvirt.libvirtError:
-            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
-                self._update_libvirt_domain()
-            else:
-                raise
-
         return self._libvirt_domain
 
     def get_uuid(self):
@@ -712,33 +700,41 @@ class QubesVm(object):
         if dry_run:
             return 666
 
-        if self.libvirt_domain is None:
+        try:
-            return 0
-
             if not self.libvirt_domain.isActive():
                 return 0
             return self.libvirt_domain.info()[1]
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return 0
+            else:
+                raise
 
     def get_cputime(self):
         if dry_run:
             return 666
 
-        if self.libvirt_domain is None:
+        try:
-            return 0
-
             if not self.libvirt_domain.isActive():
                 return 0
             return self.libvirt_domain.info()[4]
-
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return 0
+            else:
+                raise
 
     def get_mem_static_max(self):
         if dry_run:
             return 666
 
-        if self.libvirt_domain is None:
+        try:
-            return 0
-
             return self.libvirt_domain.maxMemory()
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return 0
+            else:
+                raise
 
     def get_prefmem(self):
         # TODO: qmemman is still xen specific
@@ -757,12 +753,17 @@ class QubesVm(object):
             import random
             return random.random() * 100
 
-        libvirt_domain = self.libvirt_domain
+        try:
-        if libvirt_domain and libvirt_domain.isActive():
+            if self.libvirt_domain.isActive():
-            return libvirt_domain.getCPUStats(
+                return self.libvirt_domain.getCPUStats(
                         libvirt.VIR_NODE_CPU_STATS_ALL_CPUS, 0)[0]['cpu_time']/10**9
             else:
                 return 0
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return 0
+            else:
+                raise
 
     def get_disk_utilization_root_img(self):
         return qubes.qubesutils.get_disk_usage(self.root_img)
@@ -777,10 +778,8 @@ class QubesVm(object):
         if dry_run:
             return "NA"
 
+        try:
             libvirt_domain = self.libvirt_domain
-        if libvirt_domain is None:
-            return "NA"
-
             if libvirt_domain.isActive():
                 if libvirt_domain.state()[0] == libvirt.VIR_DOMAIN_PAUSED:
                     return "Paused"
@@ -799,8 +798,12 @@ class QubesVm(object):
                         return "Running"
             else:
                 return 'Halted'
-
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
                 return "NA"
+            else:
+                raise
+
 
     def is_guid_running(self):
         xid = self.xid
@@ -824,17 +827,28 @@ class QubesVm(object):
         return True
 
     def is_running(self):
-        if self.libvirt_domain and self.libvirt_domain.isActive():
+        try:
+            if self.libvirt_domain.isActive():
                 return True
             else:
                 return False
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return False
+            else:
+                raise
 
     def is_paused(self):
-        if self.libvirt_domain and self.libvirt_domain.state()[0] == \
+        try:
-                libvirt.VIR_DOMAIN_PAUSED:
+            if self.libvirt_domain.state()[0] == libvirt.VIR_DOMAIN_PAUSED:
                 return True
             else:
                 return False
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                return False
+            else:
+                raise
 
     def get_start_time(self):
         if not self.is_running():
@@ -1153,6 +1167,9 @@ class QubesVm(object):
         else:
             shutil.copy(self.label.icon_path, self.icon_path)
 
+        # Make sure that we have UUID allocated
+        self._update_libvirt_domain()
+
         # fire hooks
         for hook in self.hooks_create_on_disk:
             hook(self, verbose, source_template=source_template)
@@ -1202,6 +1219,9 @@ class QubesVm(object):
                         print >> sys.stderr, "--> Copying icon: {0} -> {1}".format(src_vm.icon_path, self.icon_path)
                     shutil.copy(src_vm.icon_path, self.icon_path)
 
+        # Make sure that we have UUID allocated
+        self._update_libvirt_domain()
+
         # fire hooks
         for hook in self.hooks_clone_disk_files:
             hook(self, src_vm, verbose)
@@ -1237,6 +1257,8 @@ class QubesVm(object):
         for hook in self.hooks_remove_from_disk:
             hook(self)
 
+        self.libvirt_domain.undefine()
+
         self.storage.remove_from_disk()
 
     def write_firewall_conf(self, conf):
@@ -1771,6 +1793,7 @@ class QubesVm(object):
             raise QubesException ("VM already stopped!")
 
         self.libvirt_domain.destroy()
+        self.refresh()
 
     def suspend(self):
         self.log.debug('suspend()')

core-modules/006QubesAdminVm.py

@@ -75,6 +75,10 @@ class QubesAdminVm(QubesNetVm):
     def get_mem_static_max(self):
         return vmm.libvirt_conn.getInfo()[1]
 
+    def get_cputime(self):
+        # TODO: measure it somehow
+        return 0
+
     def get_disk_usage(self, file_or_dir):
         return 0
 

core-modules/01QubesHVm.py

@@ -219,6 +219,9 @@ class QubesHVm(QubesVm):
         except Exception as e:
             print >> sys.stderr, "WARNING: Failed to set VM icon: %s" % str(e)
 
+        # Make sure that we have UUID allocated
+        self._update_libvirt_domain()
+
         # fire hooks
         for hook in self.hooks_create_on_disk:
             hook(self, verbose, source_template=source_template)

core/qubesutils.py

@@ -334,9 +334,18 @@ def block_check_attached(qvmc, device):
         raise QubesException("You need to pass qvmc argument")
 
     for vm in qvmc.values():
+        try:
             libvirt_domain = vm.libvirt_domain
             if libvirt_domain:
-            xml = vm.libvirt_domain.XMLDesc()
+                xml = libvirt_domain.XMLDesc()
+            else:
+                xml = None
+        except libvirt.libvirtError:
+            if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                libvirt_domain = None
+            else:
+                raise
+        if xml:
             parsed_xml = etree.fromstring(xml)
             disks = parsed_xml.xpath("//domain/devices/disk")
             for disk in disks:
@@ -720,8 +729,15 @@ class QubesWatch(object):
             self._device_removed, None)
         # TODO: device attach libvirt event
         for vm in vmm.libvirt_conn.listAllDomains():
+            try:
                 if vm.isActive():
                     self._register_watches(vm)
+            except libvirt.libvirtError:
+                # this will happen if we loose a race with another tool,
+                # which can just remove the domain
+                if vmm.libvirt_conn.virConnGetLastError()[0] == libvirt.VIR_ERR_NO_DOMAIN:
+                    pass
+                raise
         # and for dom0
         self._register_watches(None)