Bug#591093: Grub2 needs manual configuration to boot Xen and LVM2

[Stuart Chalmers]

Package: grub-common
Version: 1.98+20100710-1 (amd64)

(dom0) System is set up with a single disk with both /boot and / (root) 
contained within an LVM2 physical volume.

When Xen (xen-hypervisor-4.0-amd64 4.0.1~rc3-1 and linux-image-2.6.32-5-amd64 
2.6.32-15) and Grub are installed
the following is automatically placed in/boot/grub/grub.cfg for the Xen menu 
entries:

--
    echo    'Loading Linux 2.6.32-5-xen-amd64 ...'
    multiboot    /boot/xen-4.0-amd64.gz placeholder
    module    /boot/vmlinuz-2.6.32-5-xen-amd64 placeholder root=UUID=<UUID of 
what seems to be the root device - (/dev/disk/by-uuid/<UUID> -> /dev/dm-0 
(root))> ro  quiet
--

Note that this contrasts with the non-Xen entries:

--
    echo    'Loading Linux 2.6.32-5-xen-amd64 ...'
    linux    /boot/vmlinuz-2.6.32-5-xen-amd64 root=/dev/mapper/<LVM2 volume 
group>-<LVM2 logical volume for root> ro  quiet
--

Furthermore, the system has an ATI Radeon graphics card installed which seems to 
use Kernel Mode Setting (KMS) by
default and this causes further issues when starting the X server in the system 
with Xen (in fact, firmware-linux-nonfree-0.26
had to be installed in order to get an X session regardless of Xen being started 
or not).

Working around is fairly straightforward - manually update the Xen entry in 
grub.cfg as follows:

--
    multiboot    /boot/xen-4.0-amd64.gz placeholder  
    module    /boot/vmlinuz-2.6.32-5-xen-amd64 placeholder 
root=/dev/mapper/<LVM2 volume group>-<LVM2 logical volume for root> ro  quiet 
nomodeset
--

However, I think that it would be useful to make this all a bit more user 
friendly.  Note that I'm intending to contact the Debian
Xen maintainers to see if KMS can be accommodated within the Xen packages, so 
the 'nomodeset' entry may not be required.

N.B. It appears that the Xen menu entry is generated by /etc/grub.d/20_linux_xen 
hence filing this bug to grub-common

Kernel: Linux 2.6.32-5-amd64
Libc6: 2.11.2-2 (amd64)

Thanks in advance for looking at this.