We've started to look into memory ballooning on RHEL and KVM. I thought I'd document some of my findings here.
The concept is simple. You have your RHEL host, running KVM, that host runs a number of virtual machine guests. The guests can be anything that runs on the chip archetecture that you're emulating. In my case, x86_64 and i386. We run some Windows guests, and mostly RHEL. In my testing, i'm using a RHEL guest. I'll test this on Windows at some point, and see what happens.