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target/ppc: Add privileged message send facilities
The Processor Control facility for POWER8 processors and later provides a mechanism for the hypervisor to send messages to other threads in the system (msgsnd instruction) and cause hypervisor-level exceptions. Privileged non-hypervisor programs can also send messages (msgsndp instruction) but are restricted to the threads of the same subprocessor and cause privileged-level exceptions. The Directed Privileged Doorbell Exception State (DPDES) register reflects the state of pending privileged doorbell exceptions and can be used to modify that state. The register can be used to read and modify the state of privileged doorbell exceptions for all threads of a subprocessor and thus is a shared facility for that subprocessor. The register can be read/written by the hypervisor and read by the supervisor if enabled in the HFSCR, otherwise a hypervisor facility unavailable exception is generated. The privileged message send and clear instructions (msgsndp & msgclrp) are used to generate and clear the presence of a directed privileged doorbell exception, respectively. The msgsndp instruction can be used to target any thread of the current subprocessor, msgclrp acts on the thread issuing the instruction. These instructions are privileged, but will generate a hypervisor facility unavailable exception if not enabled in the HFSCR and executed in privileged non-hypervisor state. The HV facility unavailable exception will be addressed in other patch. Add and implement this register and instructions by reading or modifying the pending interrupt state of the cpu. Note that TCG only supports one thread per core and so we only need to worry about the cpu making the access. Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com> Signed-off-by: Cédric Le Goater <clg@kaod.org> Message-Id: <20200120104935.24449-2-clg@kaod.org> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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