RFR: 8347343: RISC-V: Unchecked zicntr csr reads [v2]

[Robbin Ehn]

> Hi, please consider.
> 
> The rdinstret/rdcycle/rdtime are really useful and would be great to add in e.g. JFR.
> But as of now they are not used and zicntr is not yet in hwprobe therefore this patch just make sure they can't be used.
> 
> If we need them before hwprobe we can add a flag for manually enabling them.
> 
> Sanity tested.
> 
> Thanks!

Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:

  Review comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23003/files
  - new: https://git.openjdk.org/jdk/pull/23003/files/f05fd1f9..d3d141a4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23003&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23003&range=00-01

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23003.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23003/head:pull/23003

PR: https://git.openjdk.org/jdk/pull/23003