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Re: [Xen-devel] RFC/Patch: Support for other bootloaders

On Tue, Mar 22, 2005 at 09:18:52AM -0500, Michal Ostrowski wrote:
> It is my opinion that it is preferable to have C code in place of
> assembly code for such tasks.

Using the linux boot format will always be an unpleasant hack, and is
only useful when multiboot loaders don't work (Xen + xenlinux + initrd
is three files, and linux only deals with two files).  I'd rather keep
this grimness separate from Xen.

As far as I can tell, the "right" answer to this problem is to port the
relevant network driver to GrUB.

> That issue aside, here are my thoughts on some of the other issues in
> this space:
> 1.  Xen command-line arguments should come from the boot-loader at boot
> time, not hard-coded into a boot image.

Fixed this morning in mbootpack.  I'll be uploading a version that
passes the boot-time command line later today.
> 2.  dom0 command-line arguments are appended to Xen command-line
> arguments, separated by  "---"  (Linux command-line parsing allows for
> "--").

Also implemented this morning in mbootpack.

> 3.  Using a ramdisk with dom0 requires that Linux be able to package a
> ramdisk within itself or that Xen at some level supports some form of a
> ram-disk format that allows multiple images to be packed into one
> module.   I think it might be feasible to get Linux to support the
> former. 

If we provide Xen with a struct mb_info that tells it where xenlinux and
the initrd are, it will boot them, without needing to change either Xen
or Linux.  That works already.

> PS:  mbootpack did not work on my system.  It printed:
> mbootpack v0.1 (alpha)
> and then nothing else happened.

Urgh.  Can you send me the command line you used to mbootpack?  It works
fine for me from EXTLINUX, though I don't have a PXELINUX test rig at
the moment, or a HS20 blade.


Tim Deegan                           (My opinions, not the University's)
Systems Research Group
University of Cambridge Computer Laboratory

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