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

[Robbin Ehn]

On Thu, 23 Jan 2025 09:51:23 GMT, Robbin Ehn <rehn 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

Merged and updated, using kernel_compare and 6.8.5.

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PR Comment: https://git.openjdk.org/jdk/pull/23256#issuecomment-2615028605