RISC-V RVA23 profile support

[Robbin Ehn]

Hi,

>From some digging, I also gathered that Hotspot now supports close to half of the mandatory extensions of RVA23.

The other half either don't provide useful instructions for us at the
moment, or they specify something that we don't care about.
For example:
- zawrs provides new instructions, but there are no good use-cases for them.
- zvkt specifies hardware behavior we don't care about.

If we missed an extension we could use, please let us know.

As Fei says, the default is to enable all non-experimental extensions
that the kernel tells us about via hwprobe - there is no need to make
any profile default.

I'd say JDK 25 can take advantage of all relevant extensions in RVA23.

Thanks, Robbin



/Robbin


>
>   Regards,
>   Pushkar
>
>   [1] https://github.com/openjdk/jdk/blob/28942406020881be79b7543105b9eb2a0dda429e/src/hotspot/cpu/riscv/globals_riscv.hpp#L97
>   [2] https://www.phoronix.com/news/Ubuntu-25.10-To-Require-RVA23
>
>
> </pushkar.kulkarni at canonical.com>