make: Entering directory `/usr/src/linux-2.6.31.5'
  CC [M]  /usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6/platform-pci/platform-pci.o
<command-line>: warning: "__XEN_INTERFACE_VERSION__" redefined
<command-line>: warning: this is the location of the previous definition
In file included from <command-line>:0:
./include/linux/autoconf.h:200:1: warning: "CONFIG_XEN_COMPAT" redefined
<command-line>: warning: this is the location of the previous definition
/usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6/platform-pci/platform-pci.c: In function ‘set_callback_via’:
/usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6/platform-pci/platform-pci.c:251: error: implicit declaration of function ‘HYPERVISOR_hvm_op’
make[2]: *** [/usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6/platform-pci/platform-pci.o] Error 1
make[1]: *** [/usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6/platform-pci] Error 2
make: *** [_module_/usr/src/hg/xen-unstable.hg/unmodified_drivers/linux-2.6] Error 2
make: Leaving directory `/usr/src/linux-2.6.31.5'