boot_cpu_data should contain the common capabilities of all cpus in the
system. identify_cpu [arch/i386/kernel/cpu/common.c] tries to enforce
that. But right now, the SMP trampoline code [arch/i386/kernel/head.S]
overwrites boot_cpu_data when the secondary cpus are started, i.e.
boot_cpu_data contains the capabilities from the last cpu that booted :-(

The attached patch adds a new, __initdata variable for the asm code.