Re: [PATCH 0/9] Add CPU-type to topology

Brice Goglin
2024-06-18T12:49:16Z

Le 17/06/2024 à 11:11, Pawan Gupta a écrit :
> Hi,
>
> This series adds support for CPU-type (CPUID.1A.EAX[31-24] on Intel) to
> differentiate between hybrid variants P+E, P-only, E-only that share the
> same Family/Model/Stepping. One of the use case for CPU-type is the
> affected CPU table for CPU vulnerabilities, which can now use the CPU-type
> to filter the unaffected variants.
>
> * Patch 1 adds cpu-type to CPU topology structure and introduces
> topology_cpu_type() to get the CPU-type.
>
> * Patch 2-4 replaces usages of get_this_hybrid_cpu_type() with
> topology_cpu_type().
>
> * Patch 5-7 Updates CPU-matching infrastructure to use CPU-type.
>
> * Patch 8 cleans up the affected CPU list.
>
> * Patch 9 uses the CPU-type to exclude P-only parts from the RFDS affected
> list.

Hello

Is there still a plan to expose this info in sysfs? Userspace currently
uses frequencies to guess which cores are E or P. Intel sent some
patches several years ago [1], but they got abandoned nowhere as far as
I know. There was also some discussion about using a "capacity" field
like ARM does, but IIRC Intel didn't like the idea in the end.

Thanks

Brice

[1] https://lkml.org/lkml/2020/10/2/1208