feat(power/qemu): generate/use a virtual machine UUID

.github/wordlist.txt

@@ -133,6 +133,7 @@ unmuted
 uncomment
 Uptime
 usb
+UUID
 vdc
 VDC
 VLC

configs/qemu.ini

@@ -51,6 +51,7 @@ storage.0.size=16
 #storage.1=/var/lib/mtda/extra-ssd.img
 #storage.1.size=16
 watchdog=i6300esb
+#uuid=11111111-2222-3333-4444-555555555555
 
 # ---------------------------------------------------------------------------
 # Shared Storage settings

docs/config.rst

@@ -369,6 +369,11 @@ The following settings are supported:
 * ``swtpm``: string [optional]
     Path to the ``swtpm`` binary to support emulation of a TPM device.
 
+* ``uuid``: string [optional]
+    UUID to assign to the QEMU/KVM virtual machine (passed via ``-uuid``).
+    When not set, a UUID is automatically generated and persisted in
+    ``/var/lib/mtda/qemu-uuid`` so the same value is reused across restarts.
+
 * ``watchdog``: string [optional]
     Name of the watchdog driver provided by QEMU/KVM for the selected machine.
 

mtda/power/qemu.py

@@ -20,6 +20,7 @@
 import threading
 import time
 import multiprocessing
+import uuid
 
 # Local imports
 from mtda.power.controller import PowerController
@@ -47,6 +48,7 @@ def __init__(self, mtda):
         self.pidOfSwTpm = None
         self.pidOfWebsockify = None
         self.swtpm = "/usr/bin/swtpm"
+        self.uuid = None
         self.watchdog = None
         self.websockify = "/usr/bin/websockify"
 
@@ -79,6 +81,11 @@ def configure(self, conf):
             self.swtpm = os.path.realpath(conf['swtpm'])
         elif os.path.exists(self.swtpm) is False:
             self.swtpm = None
+        if 'uuid' in conf:
+            try:
+                self.uuid = str(uuid.UUID(conf['uuid']))
+            except ValueError:
+                raise ValueError(f"invalid UUID: {conf['uuid']}")
         if 'watchdog' in conf:
             self.watchdog = conf['watchdog']
         n = 0
@@ -221,6 +228,29 @@ def start(self):
         if self.watchdog is not None:
             options += f" -device {self.watchdog},id=watchdog0"
 
+        # UUID option
+        vm_uuid = self.uuid
+        if vm_uuid is None:
+            uuid_file = "/var/lib/mtda/qemu-uuid"
+            if os.path.exists(uuid_file):
+                with open(uuid_file, "r") as f:
+                    data = f.read().strip()
+                try:
+                    vm_uuid = str(uuid.UUID(data))
+                except ValueError:
+                    self.mtda.debug(1, "power.qemu.start(): "
+                                       f"invalid UUID in {uuid_file}, "
+                                       "generating a new one")
+                    vm_uuid = None
+            if not vm_uuid:
+                vm_uuid = str(uuid.uuid4())
+                os.makedirs("/var/lib/mtda", exist_ok=True)
+                with open(uuid_file, "w") as f:
+                    f.write(vm_uuid + "\n")
+                self.mtda.debug(2, "power.qemu.start(): "
+                                   f"generated UUID {vm_uuid}")
+        options += f" -uuid {vm_uuid}"
+
         # swtpm options
         if self.swtpm is not None:
             with tempfile.NamedTemporaryFile() as pidfile: