Comment # 25 on bug 1230345 from Ruediger Oertel

confirmed. patch works for me:

before:
Unsupported SCSI disk layout when multipath device

updated:
s390zl21:~ # rpm -q --changelog s390-tools | head
* Mon Sep 16 2024 Nikolay Gueorguiev <nikolay.gueorguiev@suse.com>
* Applied patches (bsc#1230345)
  - zipl/src: add basic support for multiple target base disks
  -
s390-tools-01-zipl-src-add-basic-support-for-multiple-target-base-disks.patch
  -
s390-tools-02-zipl-src-add-basic-support-for-multiple-target-base-disks.patch


now:
s390zl21:~ # /boot2/gen_zipl_conf 
Using config file '/boot2/zipl.conf' (from command line)
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Building bootmap in '/boot2/zipl'
Building menu 'menu'
Adding #1: IPL section 'KIWI_SLES15_20240919' (default)
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Adding #2: IPL section 'KIWI_SLES15_20240912'
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Adding #3: IPL section 'KIWI_SLES15_20240909'
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Run /lib/s390-tools/zipl_helper.device-mapper 254:1
Preparing boot device for LD-IPL: dm-1.
Done.


thank you!