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Re: Booting a NetBSD-amd64 kernel with "grub"

Christoph Egger wrote:
>Matthias Scheler wrote:
>> On Mon, May 19, 2008 at 11:17:01PM +0200, Christoph Egger wrote:
>>>> What part of multiboot would it have to support? Just passing the
>>>> arguments to the kernel? Or does the Xen kernel also use grub to
>>>> load the dom0 kernel?
>>> Yes. You specify the dom0 via grubs "module" directive.
>> I know that part.
>>> From there, Xen knows the dom0 binary and boots it.
>> But how? My guess is that the Xen kernel uses grub to load the dom0 kernel
>> via some kind of call. Can somebody confirm that?

>No. From Grub, Xen gets the information where the dom0 binary is and 
>which parameters to pass.
>Xen itself loads the binary and runs it.

Grub loads the dom0 binary and passes the address of it to Xen as part
of the multiboot structure. The Xen kernel doesn't contain any
filesystem or network code.

We have code in boot(8) to load the new NetBSD kernel modules, I don't
think it would be all that much work to add an extra command that will
load something into memory and call into it with a multiboot struct as
a parameter. You would do something like:

  modules enable
  load hd0a:netbsd-DOM0
  multiboot hd0a:xen.gz dom0_mem=65536 -- bootdev=wd0a ro console=pc

I spent a fair bit of time looking into this today as the two machines
that I would like to run Xen on would need their disks reformatting in
order to use Grub. I will have a bit more of a play tomorrow.

Robert Swindells

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