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

Dave Hansen
2023-08-15T21:16:46Z

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

?

/* 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: */