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[Xen-users] PV-Grub and multiboot kernels

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Subject: [Xen-users] PV-Grub and multiboot kernels
From: Franklin Webber <franklin@xxxxxxxxxxxxxx>
Date: Tue, 30 Dec 2008 16:09:52 -0500
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Hello Xen-users,

I am trying to load two executables into a single VM
at different addresses.  The goal is to pass control
to the first executable, which will treat the second
executable as data.

Can PV-Grub be used to accomplish this?  I suspect
ordinary Grub should be able to do this, outside of Xen,
with a configuration like this:


  title   a multiboot test
  root    (hd0,0)
  kernel  /boot/first-exec.elf
  module  /boot/second-exec.elf

and I have successfully booted into an ordinary
multiboot-format kernel with this configuration.
However, when I start PV-Grub with the following

  kernel = "/usr/lib/xen/boot/pv-grub-x86_32.gz"
  extra = "(hd0,0)/boot/grub/menu.lst"
  memory = 64
  name = "GRUB"
  vif = [ '' ]
  disk = [ 'file:/home/linuxfilesys,hda1,w' ]

I see:

  root    (hd0,0)
   Filesystem type is ext2fs, partition type 0x83
  kernel  /boot/first-exec.elf
  module  /boot/second-exec.elf

  Error 20: Multiboot kernel must be loaded before modules

  Press any key to continue...

Note that first-exec.elf has both a Xen guest kernel
header and a multiboot kernel header.  So, if I remove
the "module ..." line from menu.lst , I can boot
first-exec.elf in a Xen VM, and if I run the Grub
"mbchk" tool on first-exec.elf , it says "All checks passed.".
But apparently PV-Grub is not convinced that it's
really a multiboot kernel.

Do you know if what I'm trying to do is possible?
Or am I wasting my time?
There are still more experiments with the structure
of first-exec.elf I can try to ensure that it really
is a multiboot kernel, but it would help to know first that
other people have already accomplished the same thing.

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