[notaplumber]

Operating systems can't disable HT/SMT in the same way as the BIOS/firmware can, but presumably it will be fine if the kernel only schedules the idle process on HT "cores", it will spend much of, or all its time in a lower power state (MWAIT? C-states?), presumably the CPU is smart enough to handle that.

[mehrdadn]

I guess figuring out whether it's only "presumably" or actually "actually" was why I asked the question in the first place.

[notaplumber]

Hmm. This thread on the OpenBSD lists suggests it may be adequate, of course disabling in the BIOS is certainly a better option, if you can.

https://marc.info/?t=152938773300027&r=1&w=2