VM guest CPU limit definition


I have tried to instantiate a VM with 88 CPUs in a host with 88 cores (with hyperthreading enabled), but I couldn’t. I wanted to instantiate just one VM in this host, it sounds weird, but it is useful for our needs. Playing with the CPU limit, I’ve found that the ‘magic number’ is 76 CPUs. I would like to know if this value is customizable and if it is, how can I change it. Probably it’s not related to OpenNebula but to the hypervisor, but I would like to know if I can change it or not and where this value is defined.

Thanks in advance.

Versions of the related components and OS (frontend, hypervisors, VMs):

I’m running OpenNebula 5.4.1 and using Ubuntu 16.04.3 LTS hosts (Kernel 4.4.0-97-generic) with this KVM hypervisor details:
Using library: libvirt 1.3.1
Using API: QEMU 1.3.1
Running hypervisor: QEMU 2.5.0

The VM guest I’m trying to instantiate is an Ubuntu 16.04.3 LTS server.