q-dev: fix auto-attachment of block devices

qubes/ext/block.py

@@ -470,7 +470,8 @@ def on_device_pre_attached_block(self, vm, event, device, options):
             vm.app.env.get_template('libvirt/devices/block.xml').render(
                 device=device, vm=vm, options=options))
 
-    def pre_attachment_internal(self, vm, device, options):
+    def pre_attachment_internal(
+            self, vm, device, options, expected_attachment=None):
         if isinstance(device, qubes.device_protocol.UnknownDevice):
             print(f'{device.devclass.capitalize()} device {device} '
                   'not available, skipping.', file=sys.stderr)
@@ -519,7 +520,7 @@ def pre_attachment_internal(self, vm, device, options):
                   file=sys.stderr)
             return
 
-        if device.attachment:
+        if device.attachment != expected_attachment:
             raise qubes.devices.DeviceAlreadyAttached(
                 'Device {!s} already attached to {!s}'.format(
                     device, device.attachment)
@@ -546,11 +547,9 @@ async def on_domain_start(self, vm, _event, **_kwargs):
 
     def notify_auto_attached(self, vm, device, options):
         # bypass DeviceCollection logic preventing double attach
-        self.pre_attachment_internal(vm, device, options)
-
-        vm.libvirt_domain.attachDevice(
-            vm.app.env.get_template('libvirt/devices/block.xml').render(
-                device=device, vm=vm, options=options))
+        # we expected that these devices are already attached to this vm
+        self.pre_attachment_internal(
+            vm, device, options, expected_attachment=vm)
 
     @qubes.ext.handler('domain-shutdown')
     async def on_domain_shutdown(self, vm, event, **_kwargs):

templates/libvirt/xen.xml

@@ -156,6 +156,11 @@
 
             {# start external devices from xvdi #}
             {% set counter = {'i': 4} %}
+            {% for assignment in vm.devices.block.get_assigned_devices(False) %}
+                {% set device = assignment.device %}
+                {% set options = assignment.options %}
+                {% include 'libvirt/devices/block.xml' %}
+            {% endfor %}
 
             {% if vm.netvm %}
                 {% include 'libvirt/devices/net.xml' with context %}