v9fs is the code-name for the linux kernel client implementation of the Plan 9 remote file system protocol 9p. The original kernel port was documented in this paper, it later added support for virtio so that it could be used as a paravirtualized file system interface for KVM. Documentation for how to use v9fs with qemu/kvm can be found (here)[https://wiki.qemu.org/Documentation/9psetup], and there are also examples of how to use 9p as your root filesystem.
This Github group contains a mirror of the official kernel.org development trees for v9fs as well as mirrors of several of the more popular servers, as well as support repositories for testing and performance measurement.
You can contribute to v9fs by joining the mailing list, the archives of the mailing list are available here