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 13:16:40 -0700 [thread overview]
Message-ID: <5085A9A8.5020004@zytor.com> (raw)
In-Reply-To: <873916i88t.fsf@xmission.com>
On 10/22/2012 01:04 PM, Eric W. Biederman wrote:
> HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com> writes:
>
>> We disable BSP if boot cpu is AP.
>>
>> INIT-INIT-SIPI sequence, a protocal to initiate AP, cannot be used for
>> BSP since it causes BSP jump to BIOS init code; typical visible
>> behaviour is hang or immediate reset, depending on the BIOS init code.
>>
>> INIT can be used to reset AP in a fatal system error state as
>> described in MP spec 3.7.3 Processor-specific INIT. In contrast, there
>> is no processor-specific INIT for BSP to initilize from a fatal system
>> error. It might be possible to do so by NMI plus any hand-crafted
>> reset code that is carefully designed, but at least I have no idea in
>> this direction now.
>
> Has anyone looked at clearing bit 8 of the IA32_APIC_BASE_MSR (0x1B) on
> the bootstrap processor? Bit 8 being the bit that indicates we are a
> bootstrap processor.
>
> If we can clear that bit INIT will always place the processor in
> wait-for-startup-ipi mode and we won't have this problem.
>
> That would also solve the hotunplug the bootstrap processor without
> using an NMI as well.
>
IIRC Fenghua experimented with that and it didn't work. Not all BIOSes
use that bit to determine BSP-ness.
-hpa
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next prev parent reply other threads:[~2012-10-22 20:17 UTC|newest]
Thread overview: 31+ 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 ` [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 ` [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP HATAYAMA Daisuke
2012-10-22 20:04 ` Eric W. Biederman
2012-10-22 20:16 ` H. Peter Anvin [this message]
2012-10-22 20:31 ` Eric W. Biederman
2012-10-22 20:33 ` H. Peter Anvin
2012-10-22 20:38 ` H. Peter Anvin
2012-10-22 20:43 ` Eric W. Biederman
2012-10-22 20:47 ` H. Peter Anvin
2012-10-22 21:29 ` Eric W. Biederman
2012-10-23 0:35 ` H. Peter Anvin
2012-10-26 3:24 ` HATAYAMA Daisuke
2012-10-26 4:13 ` Eric W. Biederman
2013-03-11 1:07 ` HATAYAMA Daisuke
2013-03-11 2:13 ` HATAYAMA Daisuke
2013-03-11 4:11 ` H. Peter Anvin
2012-10-16 4:51 ` [PATCH v1 0/2] " Yu, Fenghua
2012-10-16 5:03 ` HATAYAMA Daisuke
2012-10-16 5:14 ` Yu, Fenghua
2012-10-16 6:38 ` HATAYAMA Daisuke
2012-10-22 16:02 ` H. Peter Anvin
2012-10-16 5:15 ` HATAYAMA Daisuke
2012-10-17 14:12 ` Vivek Goyal
2012-10-18 3:08 ` HATAYAMA Daisuke
2012-10-18 14:14 ` Vivek Goyal
2012-10-19 3:20 ` HATAYAMA Daisuke
2012-10-19 15:17 ` Vivek Goyal
2012-10-22 6:32 ` HATAYAMA Daisuke
2012-10-22 18:37 ` Vivek Goyal
2012-10-22 17:10 ` Michael Holzheu
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