Thanks both, very useful. One constraint on our side: this VM runs SQL Server 2014, and per Microsoft it’s supported only up to Windows Server 2019 (not 2022/2025). So our realistic target is 2012 R2 → 2019 in-place (after updating SQL to SP3), with the old Citrix tools removed beforehand and the new XCP-ng tools installed afterwards. We’ll rehearse the whole thing on a clone first, and note down the static IP config before removing the tools.

@ovicz said:

ovicz
17 minutes ago

Why don't you upgrade the VM to Windows Server 2016 ??. It is possible to do an in-place upgrade from 12 to 16. Of course take a backup first.

Thanks @ovicz, good point. An in-place upgrade to 2016 is definitely on the table. The main constraints on our side are a 2016 license and downtime: this is a production SQL server without a regular maintenance window, so we’d first test the whole upgrade on a clone to know the exact downtime and catch surprises. One practical question if you’ve done it: did you remove the old Citrix PV tools before the in-place upgrade (and install the new XCP-ng tools afterwards), or upgrade with the old tools still installed?

Thanks a lot @dinhngtu, that's very helpful. Is there any chance the 9.1.200 tools (or at least its XenVbd) would work unofficially on Server 2012 R2?

@dinhngtu said:

dinhngtu
VATES 🪐
XCP-NG TEAM
a day ago

@hrvojer There are many bugs in older versions of the Xen PV drivers. I suggest running Windows without guest tools and drivers if you can take the performance and functionality hit (no suspend/migration on UEFI VMs, no metric reporting, etc).

Thanks @dinhngtu, appreciated.

Running without PV drivers is hard for us: this is an I/O-heavy production SQL Server and we already had timeout problems before adding RAM, so I'm worried emulated disk performance would hurt more than an occasional crash.

Our medium-term plan is to migrate SQL to a new VM with a supported Windows Server and current tools. Until then, a few follow-up questions:

1. Is there any official place to still get XenServer VM Tools 9.2.3 (or whichever last version works on 2012 R2)?
2. Would an older XCP-ng PV driver release (e.g. 8.2.2.200) likely be any better here, or is it the same xenvbd code base?
3. One more detail I missed: in the same Feb 2026 change we also enabled "Lock Pages in Memory" for the SQL Server service account (together with 16 -> 64 GB RAM). Is there any known issue between old xenvbd and locked pages / large guest memory?

Meanwhile we've capped SQL max server memory at 32 GB as a stopgap.

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. 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

1. 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)?
2. 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.
3. 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!

@dhiraj26683 Sorry for late reply, I'm interested if you solve this issue?

I have similar issue on one node in cluster, the other working well.

When memory issue happened last time I moved all VMs on 'healty' node and on problematic node I applied:

# free && sync && echo 3 > /proc/sys/vm/drop_caches && free 

After few seconds I was prompted with login (all the time server was responsive so I think it is not restarted).

I know that doesn't solve problem of not releasing cache, but I didn't have to restart server, at least - maybe

So if you have something better, please let me know!