From 554c0309797eca83b8b3fa4c98767b7ae8468555 Mon Sep 17 00:00:00 2001
From: Cedric Hombourger <cedric.hombourger@siemens.com>
Date: Thu, 9 Apr 2026 14:49:41 +0200
Subject: [PATCH] feat(power/qemu): generate/use a virtual machine UUID

SMBIOS can expose a unique machine identifier for the Operating
System to identify the machine it is running on. Make the qemu
power controller generate/use a machine ID and pass it over to
qemu via the -uuid option.

Signed-off-by: Cedric Hombourger <cedric.hombourger@siemens.com>
---
 .github/wordlist.txt |  1 +
 configs/qemu.ini     |  1 +
 docs/config.rst      |  5 +++++
 mtda/power/qemu.py   | 30 ++++++++++++++++++++++++++++++
 4 files changed, 37 insertions(+)

diff --git a/.github/wordlist.txt b/.github/wordlist.txt
index 9e2e098a..8e10b617 100644
--- a/.github/wordlist.txt
+++ b/.github/wordlist.txt
@@ -133,6 +133,7 @@ unmuted
 uncomment
 Uptime
 usb
+UUID
 vdc
 VDC
 VLC
diff --git a/configs/qemu.ini b/configs/qemu.ini
index 530ebf8a..f69e15fc 100644
--- a/configs/qemu.ini
+++ b/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
diff --git a/docs/config.rst b/docs/config.rst
index cfae26e0..26426d77 100644
--- a/docs/config.rst
+++ b/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.
 
diff --git a/mtda/power/qemu.py b/mtda/power/qemu.py
index b190e444..05e0334e 100644
--- a/mtda/power/qemu.py
+++ b/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: