It should be noted that this isn't quite true. The default (production-grade) KVM module shipped in SmartOS presently only supports Intel CPUs with both VT-x a

It should be noted that this isn't quite true. The default (production-grade) KVM module shipped in SmartOS presently only supports Intel CPUs with both VT-x and EPT. SmartOS itself runs fine on AMD CPUs, and you can use everything except KVM for hardware-accelerated virtual machines.