Comment 58 for bug 1304001

"xen:balloon: reserve_additional_memory: add_memory() failed: -17" can only occur in HVM guests if the balloon target is set above the maximum allowed by the guest's memory map.

This is likely a bug in the EC2 toolstack. Perhaps this was introduced as a workaround for the problem fixed by c275a57f5ec (xen/balloon: Set balloon's initial state to number of existing RAM pages) which was added in Linux 3.13?