Adding virtual cores to VCPUs to XenServer VM
go to xencenter, shut down VM. add another VCPU, then do the following...
Get the UUID using the following command
xe vm-list name-label=<Name of the VM>
Set the number of cores per processor using the following command
xe vm-param-set platform:cores-per-socket=’4’ uuid=<VM UUID from Step1>
Set the number of VCPU’s at startup with the following command
xe vm-param-set VCPUs-at-startup='2' uuid=<VM-UUID> note: this value may need to be 1 for the first go around with these commands.
Finally, Set the number of max cores with the following command
xe vm-param-set VCPUs-max='4'