The second implementation (useGCM) uses // the newer KMA instruction which performs both operations (but still requires // KIMD to hash large nonces). // Keep in sync with crypto/tls.hasAESGCMHardwareSup. var useGHASH = cpu.S390XHasAES && cpu.S390XHasAESCTR && cpu.S390XHasGHASH var useGCM = useGHASH && cpu.S390XHasAESGCM func init() { impl.Register("gcm", "CPACF/KIMD", &useGHASH) impl.Register("gcm", "CPACF/KMA", &useGCM) } func checkGenericIsExpect() { if useGHASH || useGCM { panic("gcm: internal...