Partial fix for PCI devices reordering. See QubesOS/qubes-issues#6587 .

qubes/devices.py

@@ -55,6 +55,9 @@
 `domain-qdb-change:path`) to detect changes and fire
 `device-list-change:class` event.
 '''
+from collections import OrderedDict
+from typing import Optional
+
 import qubes.utils
 
 class DeviceNotAttached(qubes.exc.QubesException, KeyError):
@@ -371,6 +374,41 @@ def assignments(self, persistent=None):
             result.update(self._set)
         return result
 
+    def assignments_list(self, persistent: Optional[bool]=None):
+        '''List assignments for devices which are (or may be) attached to the
+           vm.
+
+        Devices may be attached persistently (so they are included in
+        :file:`qubes.xml`) or not. Device can also be in :file:`qubes.xml`,
+        but be temporarily detached.
+
+        :param Optional[bool] persistent: only include devices which are or are not
+        attached persistently.
+        '''
+
+        try:
+            devices = self._vm.fire_event('device-list-attached:' + self._bus,
+                persistent=persistent)
+        except Exception:  # pylint: disable=broad-except
+            self._vm.log.exception('Failed to list {} devices'.format(
+                self._bus))
+            if persistent is True:
+                # don't break app.save()
+                return list(self._set)
+            raise
+        result = []
+        if persistent is not False:  # None or True
+            result.extend(self._set)
+        if not persistent:  # None or False
+            for dev, options in devices:
+                if dev not in self._set:
+                    result.append(
+                        DeviceAssignment(
+                            backend_domain=dev.backend_domain,
+                            ident=dev.ident, options=options,
+                            bus=self._bus))
+        return result
+
     def available(self):
         '''List devices exposed by this vm'''
         devices = self._vm.fire_event('device-list:' + self._bus)
@@ -433,7 +471,7 @@ class PersistentCollection:
     '''
 
     def __init__(self):
-        self._dict = {}
+        self._dict = OrderedDict()
 
     def add(self, assignment: DeviceAssignment):
         ''' Add assignment to collection '''

qubes/vm/__init__.py

@@ -329,7 +329,7 @@ def __xml__(self):
         for devclass in self.devices:
             devices = lxml.etree.Element('devices')
             devices.set('class', devclass)
-            for device in self.devices[devclass].assignments(persistent=True):
+            for device in self.devices[devclass].assignments_list(persistent=True):
                 node = lxml.etree.Element('device')
                 node.set('backend-domain', device.backend_domain.name)
                 node.set('id', device.ident)