[zootm]

I believe it's because the "normal". EC2 instances are paravirtualised through Xen, whereas the types listed are hardware virtualisation. Not sure though.

[sdfjkl]

Used to be that only the Windows instances were HVM (thus the defenestration hack using them to get FreeBSD onto AWS) and all the Unix ones used paravirtualization - has this changed?

[zootm]

I think cluster instances are always HVM, not sure about high IO.

[cperciva]

Cluster, high-I/O, and M3 all have HVM available. Basically, all the new instance types released since I started complaining to EC2 engineers about how HVM is so much easier to work with than PV... ;-)

[sdfjkl]

Ah, so we could've had FreeBSD by coughing up the cash for one of those - or was there any special porting needed for it?

[cperciva]

Porting was needed, but I've done it for you.