Information about what cpu supports Hardware virtualization.
VT-x, shows in /proc/cpuinfo as the vmx flag. (grep vmx /proc/cpuinfo)
See Wikipedia's article on x86 virtualization, for a list of processors that include it.
AMD-V, shows in /proc/cpuinfo as the svm flag. (grep svm /proc/cpuinfo)
AKA Pacifica, AKA AMD Virtualization
KVM for PowerPC supports selected embedded cores. It also supports all 64-bit server / desktop class CPUs like the G5, POWER4 and above, Cell, 970MP, and 32-bit desktop class CPUs like the G3, G4, e300, etc.
Every S390 that has 64-bit support can use KVM. So if your mainframe is at least a z9, you're good!