Building with the attached random configuration file,

arch/x86/xen/grant-table.c: In function ‘xen_pvh_gnttab_setup’:
arch/x86/xen/grant-table.c:181:2: error: implicit declaration of
function ‘xen_pvh_domain’ [-Werror=implicit-function-declaration]
  if (!xen_pvh_domain())
  ^
cc1: some warnings being treated as errors
make[2]: *** [arch/x86/xen/grant-table.o] Error 1