Re: Xen hypervisor

[Jan Nieuwenhuizen]

Danny Milosavljevic writes:

> Hi Janneke,
>
> with our (gnu bootloader grub) already supporting multiboot, it would be easy
> for us to add official support for the Xen hypervisor & Linux.
>
> I've already packaged xen and it's ready to be used.
>
> In order to boot Xen, the grub config should read something like this:

Nice; this could help a lot with hurd work, notably 64bit/x86_64 and SMP
work, IIUC.

> Note especially that "multiboot" is "/xen-4.1-amd64.gz", and that "module"
> statements are used for the linux kernel and for the initrd.

OK.

> The work you have been doing for the Hurd already fetches both the "multiboot"
> and the "module" parameters from the boot-parameters via
> boot-parameters->menu-entry.
>
> But I can't find how I can set the multiboot-modules in my operating-system
> definition.

Yes,..currently, you only can if you're "hurd":

gnu/system.scm has:
--8<---------------cut here---------------start------------->8---
(define (boot-parameters->menu-entry conf)
  (let* ((kernel (boot-parameters-kernel conf))
         (multiboot-modules (boot-parameters-multiboot-modules conf))
         (multiboot? (pair? multiboot-modules)))
--8<---------------cut here---------------end--------------->8---

and

--8<---------------cut here---------------start------------->8---
(define (operating-system-multiboot-modules os)
  (if (operating-system-hurd os) (hurd-multiboot-modules os) '()))
--8<---------------cut here---------------end--------------->8---

> Like,
>
> (operating-system
>   (kernel (file-append xen "/boot/xen.gz"))
>   (multiboot-modules (list linux-libre initrd)))

Yes, we need some an indirection.  There already is

--8<---------------cut here---------------start------------->8---
(define (hurd-multiboot-modules os)
  (let* ((hurd (operating-system-hurd os))
         (root-file-system-command
          (list (file-append hurd "/hurd/ext2fs.static")
                "ext2fs"
                "--multiboot-command-line='${kernel-command-line}'"
                "--host-priv-port='${host-port}'"
                "--device-master-port='${device-port}'"
                "--exec-server-task='${exec-task}'"
                "--store-type=typed"
                "--x-xattr-translator-records"
                "'${root}'" "'$(task-create)'" "'$(task-resume)'"))
...
--8<---------------cut here---------------end--------------->8---

> Also, how do I get guix's usual initrd into that multiboot-modules list ?

Yes, that's another thing that would need to change, if you look at

gnu/bootloader/grub.scm has:
--8<---------------cut here---------------start------------->8---
(define* (grub-configuration-file config entries
...
      (if linux
          (let ((arguments (menu-entry-linux-arguments entry))
          ...
          (let ((kernel (menu-entry-multiboot-kernel entry))
          ...
--8<---------------cut here---------------end--------------->8---

we don't do multiboot when we're doing linux.

> Do you think it would make sense to adapt boot-parameters->menu-entry
> slightly so one could specify both a multiboot kernel and a linux kernel
> at the same time?  Or would that be too magical?

Hmm, I'd have to see the patch ;-)  We need a parameterisation, not sure
if splitting case LINUX in two is preferrable over a third flavor.

HTH!

Greetings,
Janneke

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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