Understanding KVM in RHEL 6

I need some help in understanding how KVM works in RHEL 6.

I recently installed RHEL 6 and noticed that in RHEL 6 two processes are created for each VM. This is different from what I'm used to in RHEL 5.5 where there was only one process for each VM. Moreover when I "pin" my VM to specific CPU core, only one of the processes becomes "pinned" - the other one "travels" across the free cores... Can somebody explain to me what this 2nd process is about? And why it doesn't follow "virsh cpupin" configuration?

Another question is how can I "reserve CPU resources" for the specific VM. In other words, how can I be sure that specific VM instance gets at least 1 or 2 CPU cores _exclusively_ and no other VM or application on my host machine can "starve" it? I thought that this can be done using cgroups, but I can't find proper documentation on it...

Thank you in advance,

    Alex