Re: [PATCH 07/10] cpu/SMT: Allow enabling partial SMT states via sysfs

[Thomas Gleixner]

On Thu, Jun 15 2023 at 17:46, Laurent Dufour wrote:
>  
> -     if (ctrlval != cpu_smt_control) {
> +     orig_threads = cpu_smt_num_threads;
> +     cpu_smt_num_threads = num_threads;
> +
> +     if (num_threads > orig_threads) {
> +             ret = cpuhp_smt_enable();
> +     } else if (num_threads < orig_threads) {
> +             ret = cpuhp_smt_disable(ctrlval);
> +     } else if (ctrlval != cpu_smt_control) {
>               switch (ctrlval) {
>               case CPU_SMT_ENABLED:
>                       ret = cpuhp_smt_enable();

This switch() is still as pointless as in the previous version.

OFF -> ON, ON -> OFF, ON -> FORCE_OFF are covered by the num_threads
comparisons.

So the only case where (ctrlval != cpu_smt_control) is relevant is the
OFF -> FORCE_OFF transition because in that case the number of threads
is not changing.

          force_off = ctrlval != cpu_smt_control && ctrval == 
CPU_SMT_FORCE_DISABLED;

          if (num_threads > orig_threads)
                  ret = cpuhp_smt_enable();
          else if (num_threads < orig_threads || force_off)
                  ret = cpuhp_smt_disable(ctrlval);

Should just work, no?

Thanks,

        tglx