Using the KVM API

> Is there any way to tell if a given process has created a KVM/VCPU?

Nothing better than lsof or equivalent.

> Is there a limit as to how many can be created on the system total,

As far as I know, no limit on the number of VMs other than available memory, but at the moment some limits exist on the number of VCPUs per VM. Those limits seem fixable, not inherent, though.

> and how to enumerate all of the existing ones?

Not as far as I know.