x86/apic/32: Sanitize logical APIC ID handling

x86/apic/32: Sanitize logical APIC ID handling

apic::x86_32_early_logical_apicid() is yet another historical joke.

It is used to preset the x86_cpu_to_logical_apicid per CPU variable during
APIC enumeration with:

  - 1 shifted left by the CPU number
  - the physical APIC ID in case of bigsmp

The latter is hillarious because bigsmp uses physical destination mode
which never can use the logical APIC ID.

It gets even worse. As bigsmp can be enforced late in the boot process the
probe function overwrites the per CPU variable which is never used for this
APIC type once again.

Remove that gunk and store 1 << cpunr unconditionally if and only if the
CPU number is less than 8, because the default logical destination mode
only allows up to 8 CPUs.

This is just an intermediate step before removing the per CPU insanity
completely. Stay tuned.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Juergen Gross <jgross@suse.com> # Xen PV (dom0 and unpriv. guest)