[jdk21u-dev] RFR: 8345296: AArch64: VM crashes with SIGILL when prctl is disallowed [v3]

[Aleksey Shipilev]

On Mon, 16 Dec 2024 00:23:53 GMT, Lenny Primak <duke at openjdk.org> wrote:

> Looking a bit further into this, I do not understand what the "root cause" of this issue is. Is this PR a workaround? 

This fix makes sure VM does not crash if lower layer (whether native OS or whatever sandbox/virtualization layer) does not allow us to execute `prctl(PR_SVE_GET_VL)` to get SVE vector length. Whether this is a fix or a workaround depends on whether prohibiting `prctl(PR_SVE_GET_VL)` is a bug or not from the lower layer perspective :) I tend to think the innocuous `prctl`-s should be enabled, so I tend to think about this fix as the workaround.

> What architecture does this support currently, if any? It doesn't work on Mac M4, Mac M1, and under VM in Mac M1 or M4, etc. Is the root cause somewhere in MacOS? If it is, I can't find one.

By "this" you mean SVE? SVE is a feature of modern AArch64 CPUs. AFAIU, this means Apple M4+, Graviton 3+, etc.

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PR Comment: https://git.openjdk.org/jdk21u-dev/pull/1222#issuecomment-2545218860