We have two JVM ports underway at UC Berkeley. The first is a full port of OpenJDK (which Michael Knyszek is working on) and the second is a port of the Jikes Research VM (which I am working on).
So far, OpenJDK runs successfully on RISC-V using the Zero backend. This is effectively an interpreted version and therefore very slow, but it runs real Java applications. For example, we had a poster at the Second RISC-V workshop that shows Chisel running on RISC-V. If you are interested to try out the port, we have it available as a fork of the riscv-poky repository (due to the large number of dependencies, the most feasible way to cross-compile a JVM is using poky).
I noticed that you may have found this pull request yourself and commented on it; while it may have fallen behind the latest poky-release, it is fully functional with the Zero backend.
Michael is currently working on a port of the template-based interpreter, which should substantially improve performance and is a first step to getting the optimizing JIT up and running. We are probably 20-30% through at this point, with the first couple of Java bytecodes executing correctly. Jikes is a little bit further along the path, being able to already run a few small programs when bypassing the class loader (but still major work to do).
If you are interested in getting involved, we should definitely talk! Our goal is to get the interpreter-based JVMs working as soon as possible, but afterwards a lot more effort is needed for the optimizing JIT.