The historic critique of microkernel architectures was IPC performance overhead resulting from frequent context switches between user-space services. Modern verified automotive microkernels solve this with hardware-optimized fastpath IPC routines, passing messages directly through CPU general-purpose registers without touching main memory.
When an application invokes Call IPC, the verified kernel verifies the endpoint capability in fewer than 100 assembly instructions. Message contents remain in registers r2-r7, while the kernel switches hardware thread pointers and resumes the recipient in the same core cycle.
Automotive steer-by-wire and brake-by-wire loops enforce maximum end-to-end processing budgets of 500 microseconds. Because seL4 guarantees worst-case execution time (WCET) bounds on every kernel entry, engineers can mathematically prove that multi-process microkernel stacks will never violate dynamic control deadlines.