SMP with hyperthreading CPU (5.3)?

[Luke]

> If not - what should I do besides enabling "SMP" in the kernel config
> file (sure enough "cpu I386_CPU" which effectively disables SMP is
> commented out)

I haven't updated my system since August, but back then the "apic" device 
was also required.  5.3 may be different.
This is the relevant section from my 5.2-CURRENT hyperthreading kernel 
from last August.

# To make an SMP kernel, the next two are needed
options         SMP             # Symmetric MultiProcessor Kernel
device          apic            # I/O APIC