Comment 8 for bug 1836154

directly picking changes for Disco:
- at first works fine until f2a7d157 "add z14 GA2 model"
  context misses S390_FEAT_GROUP_MULTIPLE_EPOCH_PTFF in target/s390x/gen-features.c
  The define of default_GEN14_GA2 is easily added, but I wonder if the change before being
  ddf5d18a "mepochptff: warn when no mepoch and re-align group init" might also need:
  84176c79 "s390x/cpumodel: default enable mepoch for z14 and later"
  I'll try to build it without, but let me know what you think about that.

- further as we have known already d05be57d needs
  - target/s390x/cpu_features.c -> target/s390x/cpu_features_def.inc.h
  - DEF-FEAT -> FEAT_INIT
  No questions on this one.