xen-hvm Instances fail to start on Debian Bookworm (probably related to vncpasswd setting)

[rbott]

After an Upgrade to Debian Bookworm, xen-hvm instances fail to start:

gnt-instance start xen-test-instance01

Waiting for job 258 for [xen-test-instance01.staging.ganeti.org](http://xen-test-instance01.staging.ganeti.org/) ...
Job 258 for [xen-test-instance01.staging.ganeti.org](http://xen-test-instance01.staging.ganeti.org/) has failed: Failure: command execution error:
Could not start instance '[xen-test-instance01.staging.ganeti.org](http://xen-test-instance01.staging.ganeti.org/)': Hypervisor error: Failed to start instance [xen-test-instance01.staging.ganeti.org](http://xen-test-instance01.staging.ganeti.org/): exited with exit code 3 (Parsing config from /etc/xen/[xen-test-instance01.staging.ganeti.org](http://xen-test-instance01.staging.ganeti.org/)
WARNING: you seem to be using "kernel" directive to override HVM guest firmware. Ignore that. Use "firmware_override" instead if you really want a non-default firmware
WARNING: ignoring device_model directive.
WARNING: Use "device_model_override" instead if you really want a non-default device_model
libxl: error: libxl_qmp.c:1399:qmp_ev_fd_callback: Domain 9:error on QMP socket: Connection reset by peer
libxl: error: libxl_qmp.c:1438:qmp_ev_fd_callback: Domain 9:Error happened with the QMP connection to QEMU
libxl: error: libxl_dm.c:3371:device_model_postconfig_done: Domain 9:Post DM startup configs failed, rc=-26
libxl: error: libxl_create.c:1896:domcreate_devmodel_started: Domain 9:device model did not start: -26
libxl: error: libxl_aoutils.c:646:libxl__kill_xs_path: Device Model already exited
libxl: error: libxl_domain.c:1183:libxl__destroy_domid: Domain 9:Non-existant domain
libxl: error: libxl_domain.c:1137:domain_destroy_callback: Domain 9:Unable to destroy guest
libxl: error: libxl_domain.c:1064:domain_destroy_cb: Domain 9:Destruction of domain failed
). Moved config file to /var/log/ganeti/xen/xen-test-instance01.staging.ganeti.org-2024-05-16_16_14_29

There seems to be an (unconfirmed) Debian Bug Report (#1041533) which links the error messages to the vnc_password_file setting of Ganeti (or rather the vncpasswd setting of xen). If that actually is the problem, the solution would outside of Ganeti and somewhere between xen and qemu.

There is no workaround available, as Ganeti forces the use of VNC and a VNC password upon the user.