Hi all,
We have a production Windows Server 2012 R2 VM (SQL Server) that has crashed three times with the same bugcheck in xenvbd.sys. Looking for advice and for a safe download of the last 2012 R2-compatible tools.
Environment
- XCP-ng 7.6.0 (yes, we know it's EOL; [OPTIONAL - keep or delete: a host refresh/upgrade is already being planned]. Right now we need a stopgap for this VM.)
- Storage: LVM over FC (HPE MSA 1040), multipath
- VM: Windows Server 2012 R2 (build 9600.18505), 8 vCPU, 64 GB RAM (static, dynamic min = max)
- PV drivers: Citrix xenvbd.sys 8.1.0.130 (old Citrix tools)
Crashes (identical each time)
- 2026-06-17, 2026-09-01, 2026-10-08
- BUGCHECK 0xD1 DRIVER_IRQL_NOT_LESS_OR_EQUAL (0x18, 0x2, 0x1, xenvbd+0x8795)
- Write to NULL+0x18: lock xadd dword ptr [rcx+18h],eax with rcx = 0
- Stack (from MEMORY.DMP):
nt!KiRetireDpcList -> nt!KiExecuteAllDpcs
-> xenvbd+0xf464 -> xenvbd+0x6f55 -> xenvbd+0xfecb -> xenvbd+0x8795
i.e. crash in a DPC, apparently in the I/O completion path.
Context
- The VM ran with 16 GB RAM from 2023-09 to 2026-02 with zero crashes (no restarts at all in ~29 months).
- On 2026-02-06 RAM was raised to 64 GB (SQL max server memory 14 GB -> 48 GB).
- First crash 4 months later; intervals between crashes so far: 131, 76, 37 days.
- Host logs at the time of the last crash: no FC/SCSI/multipath errors. The only event on this VM's VDIs was one SMGC coalesce with a clean tapdisk pause/unpause about 12 minutes before the crash.
Questions
- Is this a known xenvbd bug fixed in later versions (e.g. the 9.2.1 fix "A storage error can cause Windows VMs to crash", or the grant table exhaustion fix in 9.3.1)?
- A reply in the XSA-468 thread pointed to XenServer VM Tools 9.2.3 as the last version supporting 2012/2012 R2. Where can it be downloaded from an official source? downloads.xenserver.com only offers 9.6.0, and the same URL pattern for 9.2.3 returns 404.
- Could the RAM increase (16 -> 64 GB) plausibly trigger this with old xenvbd (grant tables, larger I/O)? Is there a workaround that doesn't require a driver update (e.g. a host-side setting)?
We know 2012 R2 is EOL; we are looking for a safe stopgap.
Thanks!
