- EBADCPU is returned is scheduler tries to run a process on a CPU
that either does not exist or isn't booted
- this change was originally meant to deal with stupid cpuid
instruction which provides totally useless information about
hyper-threading and MPS which does not deal with ht at all. ACPI
provides correct information. If ht is turned off it looks like some
CPUs failed to boot. Nevertheless this patch may be handy for
testing/benchmarking in the future.