XEN Windows virtual machine does not use additional vcpu

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Environment

SUSE Linux Enterprise Server 10 Service Pack 2
SUSE Linux Enterprise Server 10 Service Pack 1

Situation

Symptoms:
When the vcpu number is increased on a Windows vm, the vm does not appear to use the additional vcpus.

xm vcpu-list shows only one vcpu as running; Others appear in a "paused" state

Resolution

Check the Windows VM to see if HAL is using the driver for multiple processors. If the VM was originally installed with a single vcpu then it probably is not.

The resolution is to install the multi-processor HAL in the Windows VM. See Microsoft's support site for the current recommended method for the operating system in question.

Disclaimer

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