MIPS: Ensure FCSR cause bits are clear after invoking FPU emulator
When running the emulator to handle an instruction that raised an FP unimplemented operation exception, the FCSR cause bits were being cleared. This is done to ensure that the kernel does not take an FP exception when later restoring FP context to registers. However, this was not being done when the emulator is invoked in response to a coprocessor unusable exception. This happens in 2 cases: - There is no FPU present in the system. In this case things were OK, since the FP context is never restored to hardware registers and thus no FP exception may be raised when restoring FCSR. - The FPU could not be configured to the mode required by the task. In this case it would be possible for the emulator to set cause bits which are later restored to hardware if the task migrates to a CPU whose associated FPU does support its mode requirements, or if the tasks FP mode requirements change. Consistently clear the cause bits after invoking the emulator, by moving the clearing to process_fpemu_return and ensuring this is always called before the tasks FP context is restored. This will make it easier to catch further paths invoking the emulator in future, as will be introduced in further patches. Signed-off-by:Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9165/ Signed-off-by:
Ralf Baechle <ralf@linux-mips.org>
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