The advanced encryption standard (AES) algorithm includes three modes with
128-bit, 192-bit, and 256-bit keys. Your hardware system only provides
hardware acceleration for the 128-bit mode. The aes_s390 module failed to
allocate a software fallback for the AES modes that are not supported by the
hardware. A possible reason for this problem is that the aes_generic module
that provides the fallback algorithms is not available.
User response
Use the 128-bit mode only or ensure that the aes_generic module is available
and loaded and reload the aes_s390 module.