The attack is all about bypassing memory protection, which without an MMU to provide any, is moot --- code has access to all of memory to read normally anyway.
Cortex-M has an MPU, not MMU to provide protection for memory regions.
But as said above, the MPU/MMU has no effect on this bug, this is ab out speculative execution and determining information from a cache side channel attack.
But as said above, the MPU/MMU has no effect on this bug, this is ab out speculative execution and determining information from a cache side channel attack.