RE: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync_core() when available

[Luck, Tony]

> For a really overenginered solution, but which might perform unnecessary poorly on existing hardware:
>
> asm volatile("1: .byte 0xf, 0x1, 0xe8; 2:"
>                        _ASM_EXTABLE(1b,2b));

You win the prize for the smallest code.  Might need (the already large) comment to double
in size to explain the subtleties!

-Tony