1. A method, comprising: loading a virtual machine monitor (VMM) to support a plurality of virtual machines in a computer system, the VMM including a VMM multiplexer; loading a first and a second virtual machine (VM) supported by the VMM; determining a first VM platform configuration including a first hash value based on information measured from the first VM and a second VM platform configuration including a second hash value based on information measured from the second VM; using a trusted hardware device shared between the first and the second VM to compute a compound hash value based on a combination of the first VM platform configuration including the first hash value and the second VM platform configuration including the second hash value; storing the compound hash value in the trusted hardware device; receiving a request for a VMM service that is associated with the first VM, wherein the request comprises a challenger hash value; computing a current compound hash value based on a combination of the first VM platform configuration including the challenger hash value and the second VM platform configuration including the second VM hash value; determining whether the current compound hash value is equal to the stored compound hash value; and executing the received request when the current compound hash value is equal to the stored compound hash value.