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

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Date:	Mon, 22 Oct 2012 13:38:54 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	x86@...nel.org, mingo@...e.hu, tglx@...utronix.de,
	len.brown@...el.com, fenghua.yu@...el.com, vgoyal@...hat.com,
	grant.likely@...retlab.ca, rob.herring@...xeda.com
Subject: Re: [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP

On 10/22/2012 01:33 PM, H. Peter Anvin wrote:
> On 10/22/2012 01:31 PM, Eric W. Biederman wrote:
>>>
>>> IIRC Fenghua experimented with that and it didn't work.  Not all BIOSes
>>> use that bit to determine BSP-ness.
>>
>> What does a BIOS have to do with anything?
>>
>> The practical issue here is does an INIT IPI cause the cpu to go into
>> startup-ipi-wait or to start booting at 4G-16 bytes.
>>
>> For dealing with BIOSen we may still need to use the bootstrap processor
>> for firmware calls, cpu suspend, and other firmware weirdness, but that
>> should all be completely orthogonal to the behavior to what happens
>> when an INIT IPI is sent to the cpu.
>>
>> The only firmware problem I can imagine having is cpu virtualization
>> bug.
>>
> 
> The whole problem is that some BIOSes go wonky after receiving an INIT
> (as in INIT-SIPI-SIPI) to the BSP.
> 

(I presume the failure is SMM-related, but Fenghua might have more
details...)

	-hpa

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