Disable CPUs on boot but allow hotplug in Xen

Question

I would like to create a Xen VM with 32 possible VCPUs but have the guest OS only enable 2 of them on boot. Are there some kernel parameters I can pass in to enable this? I've played around with various combinations of additional_cpus, disabled_cpus, and possible_cpus and I can't seem to find anything that works.

Thanks!

Answer 1

I'm pretty new to Xen too, but seems like there are two Xen variables that you can set. Doing a xe vm-param-list uuid=<uuid> yields the following two variables:

VCPUs-max ( RW): 1
VCPUs-at-startup ( RW): 1

Seems like you would want to set the first one to 32 and the second one to 2 for your specific guest OS.

Answer 2

Perhaps I need to start spending more time working on my own before asking questions. I solved this issue by setting the vcpu_avail mask in the Xen config file to 3.