I was trying to run a XEN kernel on VirtualBox (mainly because other physical machines were not available) and I got the following error a few seconds after booting the kernel:

(XEN) Xen is keeping VGA console.
(XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch input to Xen)
(XEN) Freed 96kB init memory.
(XEN) ----[ Xen-3.2.1-rc1-pre x86_32p debug=n Not tainted ]----
(XEN) CPU: 0
(XEN) EIP: e008:[<ff184366>] handle_exception+0x6/0xa7
(XEN) EFLAGS: 00000087
(XEN) CR3: 00000000
(XEN) eax: 89d14900 ebx: 0000e008 ecx: 00000087 edx: c0003fb4
(XEN) esi: 0000e010 edi: 00000000 ebp: c00000cc esp: c0000000
(XEN) ds: e010 es: e010 fs: e010 gs: e020 ss: e010
(XEN) ****************************************
(XEN) Panic on CPU -1:
(XEN) DOUBLE FAULT -- system shutdown
(XEN) ****************************************
(XEN) Reboot in five seconds...

I was doing a pxe boot and these were the parameters given in pxelinux.cfg/default:

label mboot
kernel mboot.c32
append xen-3.2.gz dom0_mem=262144 com1=115200,8n1 console=com1,vga vga=current,keep pciback.hide=(02:04.0)(02:09.0) root=/dev/nfs nfsroot= --- vmlinuz-2.6.24-25-xen --- initrd.img-2.6.24-25-xen