[PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP

[H. Peter Anvin]

On 10/22/2012 01:43 PM, Eric W. Biederman wrote:
> 
> The reason the BIOSen go wonky is the INIT cause the cpu to go to the
> reset vector at 4G-16 bytes.  So it is very much expected that the
> BIOSen start acting like you just came out of reset.
> 
> If you can clear bit 8 of IA32_APIC_BASE_MSR and inform the cpu to not
> send the cpu to 4G-16 bytes and instead send the cpu into it's magic
> startup-ipi-wait mode then the BIOSen will not be involved on that path.
> 
> It is a simple question of does the cpu support clearing bit 8
> meaningfully.
> 
> If the cpu allows bit 8 to be cleared and sends the cpu to the reset
> vector on receipt of the INIT IPI I would call that a deviation from the
> x86 cpu specification.
> 
> So clearing bit 8 is not a question about BIOSen it is a question of can
> we avoid the BIOSen, by using an obscure under-documented cpu feature.
> 

As I said, I thought Fenghua tried that but it didn't work, experimentally.

	-hpa