You can apply the latest Oracle VM Server for SPARC package to a system that runs at least the following versions of the system firmware, which are platform specific and depend on the requirements of the CPU in the machine.
Fujitsu M10 servers: XCP2210
SPARC M6 servers: 9.1.0.g
SPARC M5 servers: 9.0.1.f
SPARC T5 servers: 9.1.0.b
SPARC T4 servers: 8.4.0.a
SPARC T3 servers: 8.3
UltraSPARC T2 Plus servers: 7.4.5
UltraSPARC T2 servers: 7.4.5