With the advent of kdump, the assumption that the boot CPU when running
an UP kernel is always the CPU with a hardware ID of 0 (usually referred
to as BSP on some architectures) does not hold true anymore. The reason
being that the dump capture kernel boots on the crashed CPU (the CPU
that invoked crash_kexec).

As a consequence, the hardcoding of hard_smp_processor_id() to 0 on UP
systems (see "linux/smp.h") is not correct.

This patch-set does the following:

1- Remove hardcoding of hard_smp_processor_id on UP systems.

2- Ask the hardware when possible to obtain the hardware processor id on
i386, x86_64, and ia64, independently of whether CONFIG_SMP is set or
not.

3- Move definition of hard_smp_processor_id for the UP case to asm/smp.h
on alpha, m32r, powerpc, s390, sparc, sparc64, and um architectures. I
guess that hardware features could be used to implement
hard_smp_processor_id even in the UP case, but since I am not an expert
in this architectures I just move the definition.

The patches have been tested on i386, x86_64, and ia64.

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