vagrant-cachier-ng/docs/buckets/rvm.md

rvm

Compatible with probably with any type of linux guest distro, will hook into the cache folder under the result of running rvm info as the default SSH user (usualy vagrant) on your guest. If you use rvm on the guest machine, make sure it is already installed before enabling the bucket, otherwise you won't benefit from this plugin.

To manually enable it:

Vagrant.configure("2") do |config|
  config.vm.box = 'some-box-with-rvm-installed'
  config.cache.enable :gem
end