Hello, all. pvgrub2 has just became part of upstream grub as ports i386-xen and x86_64-xen.
http://git.savannah.gnu.org/cgit/grub.git

Documentation on its usage is missing for now but in short:
ARCH=x86_64
./autogen.sh
./configure --target=$ARCH --with-platform=xen
make
mkdir -p boot/grub/
cat > boot/grub/grub.cfg <<EOF
search -s root -f /boot/grub/grub.cfg
configfile /boot/grub/grub.cfg
EOF
./grub-mkstandalone --grub-mkimage=./grub-mkimage -o grub.xen -O $ARCH-xen -d grub-core/ boot/grub/grub.cfg