Description of problem:
Updating DomU kernels to kernel-xen, the slice can no longer see the block
device on boot. I managed to get around this by running:
mkinitrd --preload=xenblk
and pointing to the new initrd before booting to the new kernel.

Now, I think it's mkinitrd run by the kernel-xen install script that failes to
notice the need for xenblk but just in case, I've ccd xen-maint in this.

Version-Release number of selected component (if applicable):


How reproducible:
Update a DomU kernel to kernel-xen, have a look at the initrd made, you should
notice the lack of xenblk. The slice will not boot up now.

Steps to Reproduce:
1. yum install kernel-xen
2.
3.
  
Actual results:
Slice does not "see" the block device and hence does not boot.

Expected results:
The slice should boot.

Additional info:
After the slice is back up you still need to --preload=xenblk to create the
right initrd (I've tried mkintrd and lloking at the init script, it does not
load the module) so I beleive the slice should break again on the next kernel
update.

I would imagine it's a trivial patch to mkinitrd to notice it's a xen (none
Dom0/DomU) kernel and preload the xenblk.

Let me know if you need any more info.

Thanks.