As suggested by Suresh Siddha and Yinghai Lu:

For x2apic pre-enabled systems, apic driver is set already early
through early_acpi_boot_init()/early_acpi_process_madt()/
acpi_parse_madt()/default_acpi_madt_oem_check() path so that
apic_id_valid() checking will be sufficient during MADT and SRAT
parsing.

For non-x2apic pre-enabled systems, all apic ids should be less
than 255.

This allows us to substitute the checks in
arch/x86/kernel/acpi/boot.c::acpi_parse_x2apic() and
arch/x86/mm/srat.c::acpi_numa_x2apic_affinity_init() with
apic->apic_id_valid().

In addition we can avoid feigning the x2apic cpu feature in the
NumaChip apic code.

The following apic drivers have separate apic_id_valid()
functions which will accept x2apic type IDs :

 x2apic_phys
 x2apic_cluster
 x2apic_uv_x
 apic_numachip
Signed-off-by: NSteffen Persvold <sp@numascale.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Daniel J Blueman <daniel@numascale-asia.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Jack Steiner <steiner@sgi.com>
Link: http://lkml.kernel.org/r/1331925935-13372-1-git-send-email-sp@numascale.comSigned-off-by: NIngo Molnar <mingo@kernel.org>