Mouse Pointer Does Not Align in XenCenter or VNC Console for MCS-Created XenServer VMs
Article ID: CTX230727
Updated On:
Description
When accessing an MCS-created XenServer VM through the XenCenter or VNC console, the mouse pointer inside the VM may not align with the real mouse pointer.
This behavior can occur when USB controller/tablet emulation is disabled for the VM. In this state, the VM console may fall back to a relative PS/2 mouse device, which can cause the console pointer to no longer track the real mouse pointer 1:1.
This issue is typically seen in XenCenter or the VNC console. It does not indicate an HDX session mouse alignment issue.
Environment
The DisablePerformanceOptimizations=true hosting connection option changes the emulated device settings applied to newly created MCS VMs on the XenServer hosting connection.
Use this option only after reviewing the expected impact on the environment. Keeping USB emulation enabled can add host CPU/scalability overhead, especially at higher VM density.
Cause
Citrix Virtual Apps and Desktops / MCS applies performance optimizations to newly created XenServer VMs. These optimizations can disable unused emulated devices, including USB controller/tablet emulation.
When USB tablet emulation is disabled, the VM console may use a relative PS/2 mouse device instead of an absolute pointing device. This can cause the mouse pointer inside the XenCenter or VNC console to become offset from the real mouse pointer.
The DisablePerformanceOptimizations=true option prevents these emulated device optimizations from applying to newly created VMs on that XenServer hosting connection.
Resolution
To enable USB controller/tablet emulation for newly created MCS VMs, update the XenServer hosting connection in Citrix Studio.
1. Open Citrix Studio.
2. Go to Hosting.
3. Select the XenServer hosting connection.
4. Edit the hosting connection.
5. Go to the Advanced settings.
6. In Connection options, add:
DisablePerformanceOptimizations=true
7. Apply the change.
This affects only new VMs created from that hosting connection. Existing VMs are not changed.
For existing VMs, set the USB platform parameters directly on the VM from the XenServer host console.
1. Identify the VM UUID:
xe vm-list
2. Set the USB parameters to true:
xe vm-param-set uuid= platform:usb=true
xe vm-param-set uuid= platform:usb_tablet=true
3. Reboot the VM.
After the VM reboots, reconnect through XenCenter or the VNC console and confirm the mouse pointer alignment.
Issue/Introduction
When accessing an MCS-created XenServer VM through XenCenter or the VNC console, the mouse pointer inside the VM may not align with the physical mouse pointer.
Additional Information
DisablePerformanceOptimizations=true is a CVAD/MCS hosting connection option used with XenServer. It is not a XenServer host-level setting.
When this option is not enabled, MCS may apply per-VM emulated device optimizations such as:
platform:parallel=none
platform:usb=false
platform:usb_tablet=false
other_config:hvm_serial=none
XenServer/QEMU consumes these settings when the VM starts. They do not affect MCS provisioning logic, inventory, power actions, or XenAPI call volume.
Expected performance impact:
Keeping USB emulation enabled can add host CPU/scalability overhead. The expected impact is approximately 0.9%, or roughly 1%, of one CPU core per VM for USB emulation.
For example, at 200 VMs, this can add up to approximately 1.8 CPU cores, or roughly 2 CPU cores, used for USB emulation.
For a small number of VMs, the impact may be minimal. At higher VM density, this can affect single-server scalability and should be considered before applying DisablePerformanceOptimizations=true broadly.
If the VMs are primarily accessed through HDX sessions, these console-related emulated devices may provide little benefit during normal user sessions.
