Oracle VM is the XEN implementation from Oracle which can be used as a hypervisor for virtualization of operating systems. Oracle VM could (should) be your standard choice when deploying virtualized environments that will be used to deploy Oracle products. Reason for this is that Oracle is only recognizing the hard partitioning of Oracle VM as a valid option with respect to their license policy.
Oracle is providing product certification for a lot of their products to make use of Oracle VM and the list is growing. On the list of certified products you can also find the Oracle RAC setup for production and none-production use. Oracle is even providing templates which ship Oracle Linux and a Oracle RAC implementation for quick deployment.
There are however some quite (un)documented things you have to consider when you deploy a RAC implementation on Oracle VM. A good read is the "Oracle Real Application Clusters in Oracle VM Environments" whitepaper from Oracle which is released in March 2012.
Within this whitepaper the following is stated:
"Specifically, for mission-critical, production deployments it is unsupported to co- locate Oracle VM guests hosting instances of the same Oracle RAC database on a single OVS physical server as a result of Oracle VM guest failover or automated DRS placement policy. Any Oracle VM guest failover or DRS placement policies must respect this fundamental RAC instance placement rules."
This means that, based upon this statement, if you wanted to deploy a 10 node production RAC implementation you cannot consolidate this on (lets say) 5 physical servers. You would need at least 10 physical servers and potentially 11. The 11 is if you wanted to be able to do a life migration to another physical server using Oracle VM and still be within the supported options. If you would only have 10 and you would do a life migration you would have to migrate it to one of the other 9 physical servers and at that moment you would no longer be in a supported setup.