RFR: 8365633: Incorrect info is reported on hybrid CPU [v2]

[Yasumasa Suenaga]

On Thu, 21 Aug 2025 15:23:25 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> Is it possible to find from CPUID or OS calls the information about hybrid CPU configuration?

I hope so too, but it is difficult as @dholmes-ora said unfortunately.

We can use `1Ah` leaf of `CPUID` to identify whether P core or not like [this code](https://github.com/YaSuenag/garakuta/blob/ebe4c8da6ed890f6144c1c32ff02b5ed3200df14/check-hybrid-cores/hy-core-check.c#L60-L95). However we would face following problem:

1. Leaf `1Ah` returns the information for the logical processor which was issued - we need to issue `CPUID` on all of logical processors with processor affinity.
2. We can identify "Intel Core" (P core) or not ("Intel Atom") via leaf `1Ah`, however we might not distinguish whether E core or LP core.
    * In Core Ultra 5 225U, both E core and LP core is Crestmont, thus they have same native model ID.

OS (Windows and Linux at least) cannot expose information about details of CPU cores AFAICS, thus it is difficult to show processor details to the user on `VM.info` and hs_err log.

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PR Comment: https://git.openjdk.org/jdk/pull/26808#issuecomment-3212570100