CREATING A COMMUNICATION CHANNEL BETWEEN DIFFERENT PRIVILEGE LEVELS USING WAIT-FOR-EVENT INSTRUCTION IN SYSTEMS OPERABLE AT MULTIPLE HIERARCHICAL PRIVILEGE LEVELS

In a computer system operable at multiple hierarchical privilege levels, a “wait-for-event” (WFE) communication channel between components operating at different privilege levels is established. Initially, a central processing unit (CPU) is configured to to “trap” WFE instructions issued by a client, such as an operating system, operating at one privilege level to an agent, such as a hypervisor, operating at a more privileged level. After storing a predefined special sequence in a storage component (e.g., a register), the client executes a WFE instruction. As part of trapping the WFE instruction, the agent reads and interprets the special sequence from the storage component and may respond to the special sequence by storing another special sequence in a storage component that is accessible to the client. Advantageously, the client may leverage this WFE communication channel to establish low-overhead watchdog functionality for the client.