qemu-kvm is the KVM 'wrapper' that provides the virtualised environment for the vCMP guests. So you'll see one of these for every guest you have running.
I see pretty much the same thing for an 11.4.1 vCMP host with 4x guests. Except I have consistently 1x vm with ~100% and 3 with 30-50%. As each vCMP is tied to a physical core (2x virtual cores as they have hyper threading), they're not going to really impact on anything.
It's possible it's an artefact of the way the kvm's are pinned to processors. (Like the way the systems used to run TMM at 100%, yet TMM itself was idle. It was simply being dispatched to idle).
H