I rebuilt the Xen installation on my desktop PC today. One minor change is that Xen is no longer its own arch.

So instead of running:

 make-kpkg --revision skx1 \
   --append-to-version .6-xen \ 
   --arch xen
   kernel_image

We now use:

 make-kpkg --revision skx1 \
   --append-to-version .6-xen \ 
   --arch i386
   kernel_image

It might be possible to use higher than i386, but I've not bothered experimenting yet.

Here are the two scripts I use to do a rebuild:

prepare.sh

This prepares the original source code:

#!/bin/sh

#
#  Remove the directory.
#
if [ -d /home/xen/tmp/linux-2.6.12 ]; then
    echo "Directory exists - removing"
    rm -rf /home/xen/tmp/linux-2.6.12 
fi

#
#  get the source if it is missing.
#
cd /home/xen/tmp
if [ ! -e linux-2.6.12.tar.bz2 ] ; then
    echo "Kernel source missing.  Fetching"
    wget ftp://ftp.kernel.org/pub/linux/kernel/v2.6/linux-2.6.12.tar.bz2
fi

#
# Unpack the source
#
echo "Unpacking source"
tar -jxf linux-2.6.12.tar.bz2

#
# patch it.
#
cd /home/xen/tmp/linux-2.6.12
/usr/src/kernel-patches/i386/apply/xen

#
# Configure the source
#
make ARCH=xen menuconfig

make-package.sh

This builds the package:

#!/bin/sh

if [ ! -d /home/xen/tmp/linux-2.6.12 ] ; then
    echo "Source directory not found"
    exit;
fi

cd /home/xen/tmp/linux-2.6.12

#
#  Build the package
#
make-kpkg --arch=i386 --revision skx5 --append-to-version .6-xen kernel_image

#
#  Initrd generation
#
if [ -d /lib/tls ]; then
  mv /lib/tls /lib/tls.disabled
fi

mkinitrd -o /boot/xen-modules-2.6.12.6-xen 2.6.12.6-xen

Both these scripts work well if you use the same naming convention as I do, and have /home/xen/tmp to play with. (I use this location since all the domains I use under Xen are stored in /home/xen/domains.)