Environment:

Host: XCP-ng (mtxen8)
Xen version: (please fill – run xl info | grep xen_version)
VM UUID: c3880bcc-9d46-1de6-e031-306894311cd2
Guest: Windows Server / Windows 10/11 (build 26100)
XCP-ng Windows Guest Tools: 9.2.350.0
Workload: PostgreSQL 18
Device-model: qemu-upstream-compat

Platform parameters (after fix):

viridian=true
viridian_time_ref_count=true
viridian_reference_tsc=true
viridian_stimer=true
viridian_apic_assist=true
viridian_crash_ctl=true
device-model=qemu-upstream-compat

Problem Description
The Windows VM periodically becomes completely unresponsive (both RDP and Xen console).

From the host the domain stays in permanent blocked state (-b----) and the QEMU device-model process disappears after receiving SIGTERM. The guest has to be force-destroyed and started again to recover.
This has happened multiple times (at least 4–5 unexpected shutdowns in the last 10 days).

Detailed Timeline of last occurrence (5 Oct 2026)

Time (approx),Event
3 Oct 07:25,Last clean PostgreSQL checkpoint
Several hours later,Guest becomes unresponsive
4 Oct 22:18:52,Windows Event 6008 – “previous system shutdown was unexpected”
4 Oct 22:18:55,Host log: qemu-dm-352: terminating on signal 15 from pid 1526469
After that,Domain remains registered but QEMU is gone → console + RDP dead
5 Oct ~10:22,Forced xe vm-shutdown force=true + clean start
After restart,"Everything works again (new domid, new QEMU process)"

xl list 352
# State: -b----   (permanently blocked)

ps aux | grep qemu-dm | grep 352
# → no process

# daemon.log
Oct  5 10:18:55 qemu-dm-352: terminating on signal 15 from pid 1526469