I'd been confused about why when I was selecting 8vCPUs on the awesome free hypervisor licence, but was only getting 2 threads in the VM.
Not the same as this thread but this is what many searches took me to so tacking it on the end in case it helps anyone else.
What solved my vaguely related issue was expanding the CPU icon in VMs settings to get to the detailed settings, and changing the sockets to one. I don't know why the CPU had options covering multisocket as the mobo only has one CPU, but changing that setting allowed the full 8 vCPU's to be recognised.
Also a thanks - the free hypervisor licence to have 8 vCPUs is appreciated as I can fiddle around learning stuff, and leave a VM running BOINC (maths for the power of good) in the background to chew up CPU cycles :-)