kvm-83. That said, as you've probably already read in the docs, KVM is a "technology preview" in RHEL 5.x...6.0 will be the first version with official/stable KVM support by Red Hat.
My understanding is that KVM was tech preview in RHEL/CentOS 5.4 and officially supported from RHEL/CentOS 5.5.
Am I mistaken?