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

From: Thomas Gleixner <[email-masked]>
Date: Thu, 22 Jun 2023 11:12:24 +0200

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