IWMEJOIN macro — WLM Enclave Join Service

The purpose of this service is to allow the task (TCB) invoking this service to join an enclave for the purpose of performance management. The scope of this service affects only a single TCB at the time the service is invoked unless SUBTASKS=YES is in effect. Any TCBs which are attached by the current TCB subsequently will also become part of the enclave environment. This inheritance of the enclave attribute will apply to any further level of newly attached subtasks as well. Unless SUBTASKS=YES is in effect, subtasks which exist at the time this service is invoked will not become part of the enclave environment nor will any subtasks which are created subsequently by these non-enclave TCBs become part of the enclave environment, unless they explicitly join.

Note that a task may only join an enclave if it is not already part of an enclave. In particular, a subtask which inherited the enclave attribute from its mother task (which may happen either as a result of the mother task issuing IWMEJOIN or IWM4STBG) is not allowed to use IWMEJOIN to explicitly join an enclave. This restriction is independent of whether the enclave specified is the same enclave as it is in, or a different enclave from the one it is in. Such a subtask which inherited the enclave attribute is also not allowed to use IWMELEAV to explicitly leave the enclave. The subtask would only leave the enclave upon its own (task) termination or when the enclave is deleted (IWM4EDEL). Also, a task which successfully establishes a Begin environment (IWM4STBG) may not invoke enclave Join, nor is the task allowed to use enclave Leave while this Begin environment exists.

Upon successful completion of this service, the CPU time for the TCB (and any subsequently attached subtasks) will be attributed to the enclave for the purpose of service unit calculations and performance period switches, rather than being attributed to the address space owning the TCB. Management and reporting for the enclave will include activity for the TCB until the TCB either leaves the enclave or the enclave is deleted.