PV AMIs boot with a special boot loader called PV-GRUB, which starts the boot cycle and then chain loads the kernel specified in the menu.lst file on your image. Paravirtual guests can run on host hardware that does not have explicit support for virtualization, but they cannot take advantage of special hardware extensions such as enhanced networking or GPU processing. Historically, PV guests had better performance than HVM guests in many cases, but because of enhancements in HVM virtualization and the availability of PV drivers for HVM AMIs, this is no longer true. For more information about PV-GRUB and its use in Amazon EC2, see PV-GRUB.
The C3 and M3 current generation instance types support PV AMIs. The C1, HI1, HS1, M1, M2, and T1 previous generation instance types support PV AMIs.
To find a PV AMI, verify that the virtualization type of the AMI is set to paravirtual, using the console or the describe-images command.