Pool update does not complete when CPU feature set has changed

Pool update does not complete when CPU feature set has changed

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Article ID: CTX231947

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Updated On:

Description

When applying a hotfix that contains CPU feature set changes to a XenServer host or pool that has running VMs, the XenCenter Install Update wizard might stop after installing the update on one or more of the hosts and display the following error:

The host does not have some of the CPU features that the VM is currently using

This message can be displayed when the update process tries to migrate a VM on shared storage from a host that has not been updated to a host that has been updated: 
The install update wizard has stopped on the last panel, 'Install Update'. The error message is displayed at the bottom. The Finish button is active, but the Previous and Cancel buttons are inactive.

This message can also be displayed when the update process tries to resume VMs on local storage that were suspended while their host was updated: 
A message box with the title 'Error Starting VM'. The message box says "There were no servers available to start VM name-of-VM". Listed are servers that have the error.

In both cases, error messages are also displayed on the Notifications page: 
On the Events tab of the Notifications page there are two errors logged. The first says Pool CPU features reduced and lists the pool name. The second error says Host CPU features reduced and lists the host.

Resolution

The host that has the new update installed has a different set of CPU features than those required by some or all of the VMs in the pool or on the host. These VMs cannot be migrated to this host or resumed on this host.

Migrating VMs on shared storage

If you saw the message when trying to migrate VMs located on shared storage between hosts, complete the following steps to update the rest of your pool:

  1. Click Finish to close the Install Update wizard.
  2. For each VM on a host that has not been updated yet, attempt to manually migrate the VM to an updated host.
  3. If the VM cannot be migrated, move it to the updated host by using these steps:
    1. Stop the VM. For example, right-click on the VM in the tree view and select Shut Down.
    2. Start the VM on an updated host. For example, right-click on the VM in the tree view and select Start On. Choose an updated host.
  4. Use the Install Update wizard to restart the update process.
  5. On the Select Servers panel, select the hosts that you moved the VMs off.

 

Resuming VMs on local storage

If you saw the message when trying to resume suspended VMs on local storage on an updated host, complete the following steps to resume the VMs on your updated host:

  1. Force shutdown the VM. For example, right-click on the VM in the tree view and select Force Shut Down.
  2. Start the VM on the updated host. For example, right-click on the VM in the tree view and select Start.
Note: You must fully shut down the VM and start it again. Attempting to reboot the VM does not fix this issue.

Problem Cause

The new update that you are applying removes CPU features that were present in an earlier version of the microcode. You cannot migrate or resume a VM on a host that has had the features removed if the VM was previously using those features.
 

January 2018

Now withdrawn hotfixes for CTX231390 - Citrix XenServer Multiple Security Updates supplied updated microcode produced by the CPU vendor, which enabled additional features to allow mitigation of the vulnerabilities. Subsequently, potential issues have been found with that microcode and tha latest updates for CTX231390 - Citrix XenServer Multiple Security Updates remove the microcode and the CPU features it contained.


November 2019

The hotfixes for CTX263684 - Citrix Hypervisor Multiple Security Updates update the microcode for Sandy Bridge CPUs. After applying these hotfixes, the feature set of these CPUs is reduced.

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