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I have a quad core machine which is running debian with a xen kernel. I am running a couple linux servers on there which don't do a lot of CPU intesive stuff, but I have there a windows server 2008 vm, which seems to be sucking the life out of one single vcpu. Is there a way to give it more vcpus? vcpus = 2 for example does nothing, which does the charm on the linux vms. Even xm list still shows the vm with one vcpu.

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When Windows installed selects the HAL library appropriate the the hardware your installing on. If you install XP on a single CPU system then the uniprocessor HAL is selected. If you then add a second vcpu to the guest then the windows HAL won't see it.

You'll need to replace Window's hal or try re-installing the guest.

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