[crac] RFR: RFC: -XX:CPUFeatures=0xnumber for CPU migration [v35]

[Jan Kratochvil]

On Thu, 15 Jun 2023 11:56:15 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Jan Kratochvil has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 110 commits:
>> 
>>  - Merge branch 'crac' into crac-altstack-cpu-cpuexplicit-strip
>>  - Fix slowdebug compilation.
>>    Split better get_processor_features_hardware/get_processor_features_hotspot().
>>  - Compatibility with non-X86; untested.
>>  - Simplify error reporting by err_msg().
>>  - Fix printing missing features on target CPU.
>>  - Fix hotspot 'ht' vs. glibc 'htt'.
>>  - CPUFeatures refactorization.
>>    Start CPU Features checking without libc.
>>  - Reintroduce initialize_processor_count() requiring -XX:+CRaCCPUCountInit.
>>     - requested by Anton Kozlov
>>  - Remove initialize_processor_count().
>>     - requested by Anton Kozlov
>>     - it was crashing for me for 4 CPU <-> 16 CPU moves
>>  - Reintroduce the "leftover" code which was not leftover.
>>  - ... and 100 more: https://git.openjdk.org/crac/compare/a282698d...7c567e99
>
> src/hotspot/cpu/x86/vm_version_x86.cpp line 2564:
> 
>> 2562: 
>> 2563:   if (ShowCPUFeatures)
>> 2564:     nonlibc_tty_print_using_features_cr();
> 
> Do I understand correctly that at this point all features are checked, and this can be a regular printing function call, involving libc?

In fact it was already using a regular printing function (`print_cr()`). It was just a wrongly named function, renamed it to: `print_using_features_cr()`

> src/hotspot/cpu/x86/vm_version_x86.cpp line 2608:
> 
>> 2606: 
>> 2607:   if (ShowCPUFeatures)
>> 2608:     nonlibc_tty_print_using_features_cr();
> 
> Can be a regular printing function call?

In fact it was already using a regular printing function (`print_cr()`). It was just a wrongly named function, renamed it to: `print_using_features_cr()`

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PR Review Comment: https://git.openjdk.org/crac/pull/41#discussion_r1236723880
PR Review Comment: https://git.openjdk.org/crac/pull/41#discussion_r1236724418