Two s390x changes landed in Debian unstable today:
- A new version of zipl-installer that will infer the root filesystem to pass to the kernel using mapdevfs instead of enforcing a single DASD partition for it.
- A new version of sysconfig-hardware that contains a hook that activates all configured disks in the initramfs instead of a single one passed in as the root parameter in the kernel command-line. Thanks to Stephen Powell for the patch.
With this it should be possible to install Debian on s390x with root on LVM. I'd be happy to hear feedback about installations with any configuration, be it root on a single DASD or root on LVM. Unless you set both mirror/udeb/suite and mirror/suite to unstable you'll need to wait until the changes are in testing, though. (The debian-installer build does not matter as zipl-installer is not part of the initrd and sysconfig-hardware is part of the installation.)
Furthermore I uploaded a new version of Hercules - a z/Architecture emulator - to get a few more years of maintenance into Debian. See its upstream changelog for details on the changes (old 3.07 → new 3.11).
At this point qemu at master is also usable for s390x emulation. It is much faster than Hercules, but it uses newfangled I/O subsystems like virtio. Hence we will need to do some more patching to make debian-installer just work. One patch for netcfg is in to support virtio networking correctly, but then it forces the user to configure a DASD. (Which would be as wrong if Fibre Channel were to be used.) In the end qemu and KVM on s390x look so much like a normal x86 VM that we could drop most of the special-casing of s390x (netcfg-static instead of netcfg; network-console instead of using the VM console; DASD configuration instead of simply using virtio-blk devices; I guess we get to keep zIPL for booting).