RFR: 8348384: RISC-V: Disable auto-enable Vector on buggy kernels

[Robbin Ehn]

On Thu, 23 Jan 2025 14:05:17 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hi please consider!
>> 
>> Linux kernels pre-6.9 can copy a dirty v-state during signal return path:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/riscv/kernel/signal.c?h=v6.13-rc1&id=c27fa53b858b4ee6552a719aa599c250cf98a586
>> 
>> We should not auto-enable vector with such kernel, as we must be able to receive signals during the execution of vector code.
>> 
>> Manual tested pre and post 6.9 as expected.
>> 
>> Thanks, Robbin
>
> src/hotspot/os_cpu/linux_riscv/riscv_hwprobe.cpp line 171:
> 
>> 169:     long major, minor;
>> 170:     os::Linux::kernel_version(&major, &minor);
>> 171:     if (!(major > 6 || (major == 6 && minor >= 9))) {
> 
> Seems that the kernel patch is also there in linux-6.8.y branch?

Yes, it is in 6.8.5. As ubuntu 24.04 is using 6.8 maybe we should care?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23256#discussion_r1927194714