> So, if you boot without Xen (even using grub to load a GENERIC
  > kernel), what happens?  If it doesn't work, that needs addressing
  > before you bring xen into the picture.

  This is not a problme. My custom kernel boots fine with fwohci
  enabled. I have attached the dmesg.log of the system in question.

It's interesting that the fwohci is on a device with cbb; it may be
that some code makes assumptions about address space that aren't valid
under Xen.  I'd suggest filing a PR with the dmesg from GENERIC and
from XEN0 w/o fwohci configured.

cbb0 at pci2 dev 1 function 0: Ricoh 5C476 PCI-CardBus bridge (rev. 0xb3)
fwohci0 at pci2 dev 1 function 1: Ricoh 5C552 PCI-CardBus bridge/Firewire (rev. 0x08)
fwohci0: interrupting at irq 9
fwohci0: OHCI version 1.10 (ROM=0)
fwohci0: No. of Isochronous channels is 4.
fwohci0: EUI64 42:4f:c0:00:1d:4a:34:38
fwohci0: Phy 1394a available S400, 2 ports.
fwohci0: Link S400, max_rec 2048 bytes.
ieee1394if0 at fwohci0: IEEE1394 bus
fwip0 at ieee1394if0: IP over IEEE1394
fwohci0: Initiate bus reset
Ricoh product 0x0822 (system subclass 0x05, interface 0x01, revision 0x17) at pci2 dev 1 function 2 not configured


-- 
        Greg Troxel <gdt@ir.bbn.com>