[crac] RFR: Fix CPUFeatures crash on new->old CPU

[Jan Kratochvil]

On Fri, 27 Oct 2023 13:08:25 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> - reproducible on i7-1165G7 "qemu-kvm -cpu host" for a checkpoint and "qemu-kvm -cpu SandyBridge" for its restore
>
> src/hotspot/share/runtime/crac.cpp line 532:
> 
>> 530:   }
>> 531:   if (!IgnoreCPUFeatures_local) {
>> 532:     VM_Version::crac_restore_finalize();
> 
> Is this function idempotent? It's called from `VM_Crac::doit()` as well (and it should be since reading the shm is optional), but could calling it twice cause any trouble?

It is but it was just a luck. At least a comment there is wrong. I will improve it, thanks.

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PR Review Comment: https://git.openjdk.org/crac/pull/134#discussion_r1374611831