[crac] RFR: 8373027: [CRaC] [CRIU] x86: FPU xsave area present, but host cpu doesn't support it

[Radim Vansa]

On Wed, 3 Dec 2025 15:08:08 GMT, Jan Kratochvil <jkratochvil at openjdk.org> wrote:

> In some cases (such as AWS `t3.nano` -> `m1.small`) CRIU refuses to restore:
> 
> x86: FPU xsave area present, but host cpu doesn't support it
> 
> 
> I think (based on information of @rvansa `xsave` is not needed for the safepoint of JDK checkpoint/restore.

While the analysis in JIRA makes sense to me, can you think of a (manual) stress test that could prove this? I would imagine an application being checkpointed while doing heavy FPU calculations. On restore, we would assert that there was not a miscalculation? We should validate such test on machine that is expected to fail, by ignoring CPU features as well as setting `--cpu-cap=none` and see that it really does miscalculate, or fail in a different way...

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PR Comment: https://git.openjdk.org/crac/pull/279#issuecomment-3625596940