1. A method of processing a guest event in a hypervisor-controlled system, the method comprising: triggering, based on the guest event, a first firmware service, the first firmware service being specific for the guest event in a firmware, the guest event being associated with a guest and with a guest state and a guest memory encrypted with a guest key; processing, by the firmware, information associated with the guest event, the information comprising information of the guest state and the guest memory, and presenting only a subset of the information of the guest state and the guest memory in decrypted form to a hypervisor, wherein the subset of the information is selected to suffice for the hypervisor to process the guest event; retaining, by the firmware, a part of the information of the guest state and the guest memory that is not being sent to the hypervisor; processing, by the hypervisor, the guest event based on the received subset of the information of the guest state and the guest memory and sending a process result to the firmware triggering a second firmware service, the second firmware service being specific for the guest event; processing, by the firmware, the received process result together with the part of the information of the guest state and the guest memory that was not sent to the hypervisor, generating to generate a state and/or memory modification; and performing, by the firmware, the state and/or memory modification associated with the guest event at the guest memory in encrypted form.