Xen / Grub2 - Domain 0 allocation causes boot panic

Question

Current setup / versions :

• Ubuntu Desktop 12.04
• Linux 3.2.0-32
• Xen 4.1-amd64
• Grub2

After following the documentation to set up xen-hypervisor-amd64 and configuring grub2, when I reboot I get the below error:

(XEN) ********************
(XEN) Panic on CPU 0:
(XEN) Domain 0 allocation is too small for kernel image.
(XEN) ********************

My current /etc/default/grub

GRUB_DEFAULT="Xen 4.1-amd64"
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX=""
GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=1024M"

Which results in the following menuentry after update-grub

submenu "Xen 4.1-amd64" {
menuentry 'Ubuntu GNU/Linux, with Xen 4.1-amd64 and Linux 3.2.0-32-generic' --class ubuntu --class gnu-linux --class gnu --class os --class xen {
        insmod part_gpt
        insmod ext2
        set root='(hd0,gpt3)'
        search --no-floppy --fs-uuid --set=root dfeb1395-8583-4bed-bc97-8f2317a7e9dd
        echo    'Loading Xen 4.1-amd64 ...'
        multiboot       /boot/xen-4.1-amd64.gz placeholder  dom0_mem=1024M
        echo    'Loading Linux 3.2.0-32-generic ...'
        module  /boot/vmlinuz-3.2.0-32-generic placeholder root=UUID=dfeb1395-8583-4bed-bc97-8f2317a7e9dd ro  
        echo    'Loading initial ramdisk ...'
        module  /boot/initrd.img-3.2.0-32-generic
}

I have tried just about every possible dom0_mem= value that I can think of including but not limited to: dom0_mem=2097152, dom0_mem=min:1024M,max:1024M, moving the entry to the vmlinuz module, and including it in the follow-up linux menuentry.

I don't know what to try next. Any help is greatly appreciated.

---

With the addition of dom0_max_vcpus=2

multiboot /boot/xen-4.1-amd64.gz placeholder dom0_mem=1024M dom0_max_vcpus=2

I get the same boot panic. But interestingly in the info displayed at boot it continues to display "Brought up 4 CPUs".

Thanks again for any help!

Answer 1

I don't think it's the dom0_mem that's an issue here. I think we're talking about space needed to load the kernel and initrd in memory into special area reserved by Xen.

Could it be that the initrd and/or vmlinuz are abnormally large. You could also try to reduce the number of CPUs available to dom0 (dom0_max_vcpus=2 for instance).