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From: "H. Peter Anvin" <hpa@zytor.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
	linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
	x86@kernel.org, mingo@elte.hu, tglx@linutronix.de,
	len.brown@intel.com, fenghua.yu@intel.com, vgoyal@redhat.com,
	grant.likely@secretlab.ca, rob.herring@calxeda.com
Subject: Re: [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP
Date: Mon, 22 Oct 2012 13:47:12 -0700	[thread overview]
Message-ID: <5085B0D0.9020508@zytor.com> (raw)
In-Reply-To: <87a9vedyqe.fsf@xmission.com>

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


WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: len.brown@intel.com, fenghua.yu@intel.com, x86@kernel.org,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	rob.herring@calxeda.com, grant.likely@secretlab.ca,
	HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
	tglx@linutronix.de, mingo@elte.hu, vgoyal@redhat.com
Subject: Re: [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP
Date: Mon, 22 Oct 2012 13:47:12 -0700	[thread overview]
Message-ID: <5085B0D0.9020508@zytor.com> (raw)
In-Reply-To: <87a9vedyqe.fsf@xmission.com>

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


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  reply	other threads:[~2012-10-22 20:47 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-16  4:35 [PATCH v1 0/2] x86, apic: Disable BSP if boot cpu is AP HATAYAMA Daisuke
2012-10-16  4:35 ` HATAYAMA Daisuke
2012-10-16  4:35 ` [PATCH v1 1/2] x86, apic: Introduce boot_cpu_is_bsp indicating whether boot cpu is BSP or not HATAYAMA Daisuke
2012-10-16  4:35   ` HATAYAMA Daisuke
2012-10-16  4:35 ` [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP HATAYAMA Daisuke
2012-10-16  4:35   ` HATAYAMA Daisuke
2012-10-22 20:04   ` Eric W. Biederman
2012-10-22 20:04     ` Eric W. Biederman
2012-10-22 20:16     ` H. Peter Anvin
2012-10-22 20:16       ` H. Peter Anvin
2012-10-22 20:31       ` Eric W. Biederman
2012-10-22 20:31         ` Eric W. Biederman
2012-10-22 20:33         ` H. Peter Anvin
2012-10-22 20:33           ` H. Peter Anvin
2012-10-22 20:38           ` H. Peter Anvin
2012-10-22 20:38             ` H. Peter Anvin
2012-10-22 20:43           ` Eric W. Biederman
2012-10-22 20:43             ` Eric W. Biederman
2012-10-22 20:47             ` H. Peter Anvin [this message]
2012-10-22 20:47               ` H. Peter Anvin
2012-10-22 21:29               ` Eric W. Biederman
2012-10-22 21:29                 ` Eric W. Biederman
2012-10-23  0:35                 ` H. Peter Anvin
2012-10-23  0:35                   ` H. Peter Anvin
2012-10-26  3:24                   ` HATAYAMA Daisuke
2012-10-26  3:24                     ` HATAYAMA Daisuke
2012-10-26  4:13                     ` Eric W. Biederman
2012-10-26  4:13                       ` Eric W. Biederman
2013-03-11  1:07                       ` HATAYAMA Daisuke
2013-03-11  1:07                         ` HATAYAMA Daisuke
2013-03-11  2:13                         ` HATAYAMA Daisuke
2013-03-11  2:13                           ` HATAYAMA Daisuke
2013-03-11  4:11                           ` H. Peter Anvin
2013-03-11  4:11                             ` H. Peter Anvin
2012-10-16  4:51 ` [PATCH v1 0/2] " Yu, Fenghua
2012-10-16  4:51   ` Yu, Fenghua
2012-10-16  5:03   ` HATAYAMA Daisuke
2012-10-16  5:03     ` HATAYAMA Daisuke
2012-10-16  5:14     ` Yu, Fenghua
2012-10-16  5:14       ` Yu, Fenghua
2012-10-16  6:38       ` HATAYAMA Daisuke
2012-10-16  6:38         ` HATAYAMA Daisuke
2012-10-22 16:02         ` H. Peter Anvin
2012-10-22 16:02           ` H. Peter Anvin
2012-10-16  5:15     ` HATAYAMA Daisuke
2012-10-16  5:15       ` HATAYAMA Daisuke
2012-10-17 14:12 ` Vivek Goyal
2012-10-17 14:12   ` Vivek Goyal
2012-10-18  3:08   ` HATAYAMA Daisuke
2012-10-18  3:08     ` HATAYAMA Daisuke
2012-10-18 14:14     ` Vivek Goyal
2012-10-18 14:14       ` Vivek Goyal
2012-10-19  3:20       ` HATAYAMA Daisuke
2012-10-19  3:20         ` HATAYAMA Daisuke
2012-10-19 15:17         ` Vivek Goyal
2012-10-19 15:17           ` Vivek Goyal
2012-10-22  6:32           ` HATAYAMA Daisuke
2012-10-22  6:32             ` HATAYAMA Daisuke
2012-10-22 18:37             ` Vivek Goyal
2012-10-22 18:37               ` Vivek Goyal
2012-10-22 17:10           ` Michael Holzheu
2012-10-22 17:10             ` Michael Holzheu

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