Re: [patch V4 02/41] cpu/SMT: Make SMT control more robust against enumeration failures

[Thomas Gleixner]

On Tue, Aug 15 2023 at 14:15, Dave Hansen wrote:
> On 8/14/23 01:53, Thomas Gleixner wrote:
>> -static inline bool cpu_smt_allowed(unsigned int cpu)
>> +static inline bool cpu_bootable(unsigned int cpu)
>>  {
>>  	if (cpu_smt_control == CPU_SMT_ENABLED)
>>  		return true;
>>  
>> +	if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
>> +		return true;
>
> I found this new pair of if()'s rather counterintuitive to read.
>
> The first one reads like:
>
> 	"If SMT is not supported, the CPU is always bootable"
>
> but "supported" could easily mean CONFIG_SMP==n (which is actually
> covered in the next case).  Would this be better named:
>
> 	CPU_SMT_NOT_ENUMERATED
> or
> 	CPU_SMT_NOT_DETECTED
>
> ?

Yes, no, maybe. I rather keep them as is because the strings which are
exposed via sysfs cannot be changed and are matching.

> 	/* Every CPU is bootable on non-SMT systems: */
> 	if (cpu_smt_control == CPU_SMT_NOT_DETECTED)
> 		return true;
>
> For the next one:
>
>> +	if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
>> +		return true;
>
> This reads a bit like "SMT is not implemented" rather than "SMT controls
> are not implemented".  Maybe a comment would help:
>
> 	/* All CPUs are bootable if controls are not implemented: */

Sure.