Behaviour of update-grub when Xen enabled kernels are installed.

[Ian Campbell]

Hi all,

The version of update-grub in Debian's grub-legacy packages[0] has an
interesting feature where it attempts to detect when I kernel is
compiled for Xen and chooses to include it in the menu depending on
whether it is running inside a Xen guest domain or not[1].

As described at [2] this behaviour has been broken by the latest kernels
which due to the paravirt_ops (CONFIG_PARAVIRT) framework which means
that these kernels are now bootable both native and as a Xen guest
domain.

Robert asked me to bring the issue here and to ask the question of
whether or not this behaviour would be welcomed as a patch to grub 2.

Personally I am not a fan of this behaviour since it causes the wrong
thing to occur in several circumstances, i.e. installing into a chroot
or switching back and forth between fully- and para-virtualised
operation and as time moves on CONFIG_PARAVIRT will become the norm and
the behaviour less necessary in general. What is the opinion of the grub
2 devs?

Cheers,
Ian.
[0] For those not familiar with Xen the classical Xen kernels cannot be
run on bare metal so there is an argument that it makes little sense to
include them in the menu for the control domain, conversely including a
native kernel in the menu for a guest domain is not terribly useful
either. CONFIG_PARAVIRT (2.6.22+) changes this and such kernel is now
bootable on native and under Xen.
[1]
http://svn.debian.org/viewsvn/pkg-grub/grub/trunk/debian/update-grub?view=auto
[2]
http://lists.alioth.debian.org/pipermail/pkg-grub-devel/2008-April/004701.html 
http://lists.alioth.debian.org/pipermail/pkg-grub-devel/2008-May/004821.html


-- 
Ian Campbell

Waste not fresh tears over old griefs.
                -- Euripides

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