Comment 2 for bug 615529

Heres some more information, this is a result of work done under the kernel-upgrades spec [1]. I had originally only used the floppy disk boot mechanism for scsi root disk, as initial boot works fine with '-kernel <grub_loader>' and virtio. If I take change the eucalyptus code to use a boot floppy for virtio root also, the result is working 'reboot'.

Heres a summary of what works, what doesn't:
- WORKS: -kernel with linux kernel, scsi disk, reboot works
- WORKS: -fda floppy, grub loader, scsi disk, reboot works
- WORKS: -kernel with linux kernel, virtio disk, reboot works
- WORKS: -fda floppy, grub loader, virtio disk, reboot works
- FAILS: -kernel with grub loader, virtio disk, reboot fails
- FAILS: -kernel with grub loader, scsi disk, wont boot (bug 611142)

notes:
 -fda floppy means grub boot floppy that loads the same grub multiboot
  image as is booted with -kernel)

--
[1] https://blueprints.launchpad.net/ubuntu/+spec/server-maverick-cloud-kernel-upgrades