Randconfig build by Fengguang's robot army reported:

   drivers/built-in.o: In function `extlog_print':
   >> acpi_extlog.c:(.text+0xcc719): undefined reference to `boot_cpu_physical_apicid'

The config had CONFIG_SMP=n so we picked up this definition from:

  <asm/cpu.h>: #define cpu_physical_id(cpu) boot_cpu_physical_apicid

But boot_cpu_physical_apicid is defined in arch/x86/kernel/apic/apic.c
which is only built if CONFIG_X86_LOCAL_APIC=y.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: Chen Gong <gong.chen@linux.intel.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Link: http://lkml.kernel.org/r/6be3afdcad7968f7fb7c0b681e547b3e872e44dd.1383947368.git.tony.luck@intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>