Alright, I know what's going on now, and it looks like a problem with
the Opensuse init script. In fact, the initrd for the Xen enabled
kernel got a *different* init script than the one for the non-Xen one.
The difference being:

--- /tmp/testing/init   2007-07-24 15:53:58.000000000 +0200
+++ /tmp/xentest/init   2007-07-24 15:54:16.000000000 +0200
@@ -308,6 +308,9 @@
     fi
 fi

+caps="$(</proc/xen/capabilities)"
+if [ "$caps" != "${caps%control_d*}" ]; then
+
 params=
 for p in $(cat /proc/cmdline) ; do
   case $p in
@@ -509,6 +512,32 @@
 echo "Loading dm-snapshot"
 modprobe dm-snapshot $params

+else
+
+params=
+for p in $(cat /proc/cmdline) ; do
+  case $p in
+    dm-mod.*)
+      params="$params ${p#dm-mod.}"
+      ;;
+  esac
+done
+echo "Loading dm-mod"
+modprobe dm-mod $params
+
+params=
+for p in $(cat /proc/cmdline) ; do
+  case $p in
+    dm-snapshot.*)
+      params="$params ${p#dm-snapshot.}"
+      ;;
+  esac
+done
+echo "Loading dm-snapshot"
+modprobe dm-snapshot $params
+
+fi
+
 echo -n "Waiting for /dev/mapper/control to appear: "
 for i in 1 2 3 4 5; do
     [ -e /dev/mapper/control ] && break

In clear: the Xen init script reads /proc/xen/capabilities and if it
doesn't find the magic string "control_d" in it, willfully *skips*
loading all the SCSI and ATA stuff.

The missing piece then is the innocent little line:

/init: line 311: /proc/xen/capabilities: No such file or directory

appearing on my screen during boot ... BOOM!

If I just diligently type all the skipped modprobe commands

$ modprobe scsi_mod
$ modprobe sd_mod
$ modprobe processor
$ modprobe thermal
$ modprobe libata
$ modprobe ahci
$ modprobe pata_marvell
$ modprobe scsi_transport_spi
$ modprobe aic7xxx
$ modprobe fan
$ modprobe edd
$ ^D

into the fallback shell by hand, the system comes up without further ado.

So there, case solved. Now you sort it out who's to fix what. :-)

Thanks,
Tilman

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
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