RFR: 8315195: RISC-V: Update hwprobe query for new extensions [v2]

[Fei Yang]

On Tue, 29 Aug 2023 08:49:51 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Hi all, please consider.
>> 
>> Linux 6.5 added new extensions to hwprobe.
>> Manually tested with qemu patch: https://lists.nongnu.org/archive/html/qemu-devel/2023-08/msg04784.html
>> And https://bugs.openjdk.org/browse/JDK-8315206 applied.
>> 
>> Also cleanup vendor path, the goal is to only have vendor specific extension in vendor paths.
>> But since we also have older kernels we need to support them also.
>> 
>> Thanks!
>
> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   pre-6.5 kernel support

Changes requested by fyang (Reviewer).

src/hotspot/os_cpu/linux_riscv/riscv_hwprobe.cpp line 147:

> 145:   if (is_set(RISCV_HWPROBE_KEY_IMA_EXT_0, RISCV_HWPROBE_EXT_ZBS)) {
> 146:     VM_Version::ext_Zbs.enable_feature();
> 147:   }

Hi, I think we should move JVM options for those RV extensions out of `EXPERIMENTAL` once they are auto-enabled like this. It should be OK at least for options like UseRVV, UseZba, UseZbb and UseZbs as they have been baked for quite some time.

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PR Review: https://git.openjdk.org/jdk/pull/15465#pullrequestreview-1602133992
PR Review Comment: https://git.openjdk.org/jdk/pull/15465#discussion_r1309863021