XCP-ng 8.3 updates announcements and testing

gleh

New maintenance update candidates for XCP-ng 8.3 LTS

This batch of updates contains performance improvements, fixes, a guest tools update, and other improvements.

What changed

Virtualization & System

kernel: Fix potential deadlocks in the NFS subsystem.
xen:
- Enable Viridian enlightenments to prepare for support of Windows VMs with >64 vCPUs
- Sync with XenServer release 4.17.7-2. It fixes XSA-511, which didn't affect XCP-ng.
systemd: Fix detection of NVMe controllers with multiple namespaces

Control Plane

xapi:
- Improve RPU stability by only migrating VMs to already-updated hosts
- Improve VDI migration performance by pipelining NBD writes
guest-templates-json:
- Sync with XenServer's guest-templates-json-2.0.16-1. It removes the Kylin Linux 7 Guest template.
- Disable Viridian in the "Other install media" template by default. As a reminder, Windows VMs must use Windows templates.

Storage

blktap:
1. A fix for a tapdisk crash happening when tapdisk pauses a VDI when a coalesce is in progress. This issue was caused by a use-after-free bug. We took time to thoroughly audit the code around pause/commit/cancel operations, and thus robustify the pause and commit code in this release.
2. Customers could get tapdisk with infinite stalled IO on QCOW2 VDI. A race-condition was identified that could allow to miss a notification from the front-end and therefore never check the blkif ring for new requests.
3. On a tapdisk running on a supporter node, CBT metadata does not flush before a pause operation. During the pause operation, the master host modifies the CBT metadata, then after the unpause the old metadata are flushed and discard master's modifications. Finally the CBT logs are detected as inconsistent and discarded.
4. Grow up the QCOW2 metadata cache to help on big disks.
sm:
- Robustify iSCSI calls against race condition and bad access using lock context manager.
- Retry host key tag removal when XAPI is unreachable or restarted to prevent errors and finish action.
- Explicitly notify a missing LINSTOR resource definition instead of displaying a human-unreadable trace.
- Repair LINSTOR RAW volume creation. Regression caused by QCOW2 code refactoring.
- Fix LINSTOR SR creation when a VG is missing on a host. Changes in behavior brought by an update of LINSTOR RPMs broke this feature, which prevented the creation of an SR in this situation. We're expanding the test suite to prevent this in the future.
- To help recovering from an eventual LINSTOR database corruption, it's now backed up regularly and after every major operation, locally on the master, and on the DRBD LINSTOR database volume.
- Fixed an issue on shared LVM-based SR (LVMoISCSI, LVMoHBA) where a failed live leaf coalesce of a QCOW2 image on a slave host caused the SRs to remain in an SR_FAILURE_1200 error state until the VM using the VDI was stopped or tapdisk was manually paused.
- Reduce qemu-img log verbosity in SMlog.
- Fix LVM metadata corruption on slave when CBT log deletion is triggered on VDI activation.
- Prevent an incorrect online coalesce to be reported as successful and causing issues with the QCOW2 chain.
- Add QCOW2 support during interrupted leaf-coalesce operations on file-based SRs.

Network

openvswitch: The openvswitch package no longer installs the unused openvswitch-cfg-update XAPI plugin file, which has been superseded by openvswitch-config-update from xapi-core. This is only meant to avoid confusion and brings no functional change.

UI

xo-lite:
- [Treeview] Add VM tree actions (PR #10304)
- [Pool/networks] Add the possibility to create new network or bonded network (PR #10145)
- [VM] Add VDIs page with table and side panel (PR #10269)
- [Host/Network] Add ability to rescan physical network interfaces (PIFs) (PR #10147)
- Fix inconsistent spacing in side panel cards (PR #10279)
- Fix missing collapse buttons on pools and hosts in the tree sidebar (added hasChildren prop) (PR #10244)
- [Pool/networks] Add the possibility to create new internal network (PR #10235)

Drivers and Middleware

vendor-drivers: The out of tree microsemi-aacraid driver from the RPM has proven to be unreliable. It has several issues, is missing patches from upstream and hasn't been updated for a while. So, we switch back to the in-tree driver just like XCP-ng 8.2 was doing.
xcp-ng-pv-tools:
- Update to XCP-ng Windows Guest Tools 9.2.385.
- Include the XenTools-fix-9.2.351.msp hotfix tool for users running 9.2.350.

Others

openssl: Update to 3.5.5

Versions

blktap: 3.55.5-9.5.xcpng8.3 -> 3.55.5-11.1.xcpng8.3
gpumon: 24.1.0-96.1.xcpng8.3 -> 24.1.0-98.1.xcpng8.3
guest-templates-json: 2.0.15-1.1.xcpng8.3 -> 2.0.16-1.1.xcpng8.3
kernel: 4.19.19-8.0.46.10.xcpng8.3 -> 4.19.19-8.0.46.12.xcpng8.3
openssl: 3.0.9-2.0.1.3.xcpng8.3 -> 3.5.5-1.3.xcpng8.3
openvswitch: 2.17.7-4.1.xcpng8.3 -> 2.17.7-4.2.xcpng8.3
sm: 3.2.12-23.5.xcpng8.3 -> 3.2.12-25.1.xcpng8.3
systemd: 219-57.5.xcpng8.3 -> 219-57.5.1.xcpng8.3
vendor-drivers: 2.0.3-1.1.xcpng8.3 -> 2.0.3-1.2.xcpng8.3
xapi: 26.1.16-1.2.xcpng8.3 -> 26.1.19-1.1.xcpng8.3
xcp-featured: 1.2.1-4.xcpng8.3 -> 1.2.1-5.xcpng8.3
xcp-ng-pv-tools: 8.3-18.xcpng8.3 -> 8.3-19.xcpng8.3
xen: 4.17.6-12.3.xcpng8.3 -> 4.17.7-2.3.xcpng8.3
xo-lite: 0.24.0-1.xcpng8.3 -> 0.25.0-1.xcpng8.3

Test on XCP-ng 8.3

yum clean metadata --enablerepo=xcp-ng-testing,xcp-ng-candidates
yum update --enablerepo=xcp-ng-testing,xcp-ng-candidates
reboot

The usual update rules apply: pool coordinator first, etc.

What to test

As usual, normal use and anything else you want to test.

Test window before official release of the updates

4 days

We would like to thank users who shared feedback since our last call for testing:
@bufanda, @acebmxer, @MajorP93, @flakpyro, @Andrew, @mthird, @manilx, @XCP-ng-JustGreat

flakpyro

@gleh said:

Disable Viridian in the "Other install media" template by default. As a reminder, Windows VMs must use Windows templates.

Working on testing this update out however this change has me a bit concerned. Will existing Windows VMs using "Other install media" be affected by this? Or is this just for VMs created going forward? Back in 2024 when we migrated from VMware using V2V all Windows VMs we migrated were created with "Other Install Media" as I'm guessing that's just how the migration process worked at the time.

dinhngtu

@flakpyro These template updates only concern new "from scratch" VMs. Older VMs should not be impacted at all.

But if some of your VMs are missing Viridian settings, you may run into poor performance and/or odd Windows issues. You can correct them using the instructions documented here: https://docs.xcp-ng.org/vms/#enabling-viridian-extensions

flakpyro

@dinhngtu Thanks for clarifying. I can confirm our windows VMs that were migrated with V2V with "Other Install media" do show having this enabled.

I will deploy to my usual batch of test hosts and update this post with my results.

dinhngtu

@flakpyro Note that various important Viridian settings are not yet settable via Xen Orchestra, so you might want to confirm using xe instead.

flakpyro

@dinhngtu We did initially run into this issue a number of years ago and were able to fix it by following this kb article at the time:
https://support.citrix.com/external/article?articleUrl=CTX692813-xenserver-potential-performance-issues-on-imported-windows-vms&language=en_US

Checking s few random migrated windows VMs and it appears these flags are still set as they should be.

acebmxer

@gleh

Installed patches on home lab. No initial issues found. Existing Windows 11 vm no issues with it on basic vm functions. Created new Windows 11 vm with 26h2 iso no issues. Also installed guest tools in both vms.

Screenshot 2026-10-01 121017.png

flakpyro

Installed on my usual test hosts without any issues so far.

olivierlambert

That's a pretty beefy update! It's great to see the live storage migration performance improving by a very nice margin

olivierlambert

Tested in my home lab, no issues so far (Intel CPU).

abudef

I have to say that the acceleration of the migration is really dramatic, which is particularly useful for occasional ad hoc migrations where another task needs to be performed immediately after the migration is completed.
and thanks!

bufanda

Installed on my usual lab pool. No issues so far seen.

jr-m4

Installed on 3xDell PowerEdge R350 in HA. And so far, I haven't noticed anything out of the ordinary.

JeffBerntsen

Installed and running on my lab system and my twinstor test pair and no problems yet.

Andrew

@gleh Up and running on busy pools. Rolling pool reboot worked correctly.

gduperrey

Thank you everyone for your tests and your feedback!

The updates are live now: https://xcp-ng.org/blog/2026/10/05/october-2026-updates-1-for-xcp-ng-8-3-lts/

We decided not to release the xen update that was initially included in the testing phase of this update cycle. It introduced changes related to support for Windows VMs with more than 64 vCPUs; a feature that is not yet fully supported and requires further work to be completely implemented.

We therefore chose to postpone it to avoid any regressions or user confusion, aiming to release a properly finalized and documented version in the near future.

This version should have no impact on your test environments, and they can continue to operate as is. Any future xen update should have a higher version number and should install over the current one.

However, if you do not wish to keep this update on your test environments, you can downgrade using the command yum downgrade xen-*.

bvitnik

@gleh said:

Disable Viridian in the "Other install media" template by default. As a reminder, Windows VMs must use Windows templates.

What is the rationale for disabling Viridian? Does it have any negative effects for non Windows VMs?

acebmxer

@gduperrey

Just tried to install the patches pushed today to home lab. All but 1 vm evactuated from the primary host.

Screenshot 2026-10-05 144713.png

 },
                    "taskRef": "OpaqueRef:f56d3f5e-d41c-c8eb-3c70-4676f74de68c",
                    "message": "task has been destroyed before completion",
                    "name": "Error",
                    "stack": "Error: task has been destroyed before completion\n    at Xapi._removeRecordFromCache (file:///opt/xen-orchestra/packages/xen-api/index.mjs:1462:21)\n    at file:///opt/xen-orchestra/packages/xen-api/index.mjs:1429:18\n    at Set.forEach (<anonymous>)\n    at file:///opt/xen-orchestra/packages/xen-api/index.mjs:1428:20"
                  }

Rolling pool update.txt

VM that wouldnt migrate -

Screenshot 2026-10-05 145334.png

Screenshot 2026-10-05 150252.png

Screenshot 2026-10-05 150324.png

Screenshot 2026-10-05 150353.png

TeddyAstie

@bvitnik
Various reasons :

In some niche cases, it can cause compatibility issues with guests.
Viridian exposes additionnal attack surface e.g VSA-2025-006 and VSA-2026-031
and given that this is generally unused for non-Windows guests, there is no good reason to expose it to the guest

For Windows guests, use of the dedicated Windows template is strongly encouraged, as it brings additional viridian flags and other tunings for better compatibility and performance.

bvitnik

@TeddyAstie Thanks