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

[Aleksey Shipilev]

On Mon, 2 Dec 2024 15:44:56 GMT, Evgeny Astigeevich <eastigeevich at openjdk.org> wrote:

>> I think this part later in the same method does the sync for us already:
>> https://github.com/openjdk/jdk/blob/b8233989e7605268dda908e6b639ca373789792b/src/hotspot/cpu/aarch64/vm_version_aarch64.cpp#L590-L597
>
> Maybe it's worth to move your new code under IF at line 518?
> 
> if (UseSVE > 0) {
>   int vl = get_current_sve_vector_length();
>   if ((FLAG_IS_DEFAULT(MaxVectorSize)) {
>       MaxVectorSize = vl;
>   }
> 
>   if (vl < 0) {
>      warning("Unable to get SVE vector length on this system. Disabling SVE. Specify -XX:UseSVE=0 to avoid this warning.");
>       FLAG_SET_DEFAULT(UseSVE, 0);
>   } else if (MaxVectorSize < FloatRegister::sve_vl_min) {
>       ...
>   }

Aha. I think the other way around: we need to do more checks right near the `_initial_sve_vector_length` inits. Hold on...

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PR Review Comment: https://git.openjdk.org/jdk/pull/22479#discussion_r1866168695