Vector on Banana Pi BPI-F3

[Robbin Ehn]

Hey!

There seems to be a large interest in running openjdk with vector on
this board out-of-the-box.
The vendor kernel have vector from 6.4 back-ported without hwprobe.
And FYI: the vendor kernel for k230 has THEAD vector patches.
Both do the right thing during context switches (sources have been checked).

It seems like we have three options, anymore?

A:
Keep what we do: i.e. no hwprobe no V.
Downside no V (default) on contemporary boards.
Hence no V coverage in CI testing and disappointed early adopters.

B:
Enable it for triplet mvendorid/marchid/mimplid.
Only V for this specific board, other boards and/or updates to this
board require new binaries.

C:
Enable it for boards with V in hwcap.
Downside boards false reporting V (1.0), such as K230 small-CPU and THEAD,
needs to be handled, safe fetch vsetvli and vsetvli v1.0 check can fix
those two examples.
If we miss a board or a new board comes out we may lack proper check thus crash.

In PRs:
https://github.com/openjdk/jdk/pull/19472
https://github.com/openjdk/jdk/pull/19679

Options A was used.

The question is if we can reconsider due to the benefits and use
another option allowing V to automatically work?

Thanks, Robbin