From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from terminus.zytor.com ([2001:1868:205::10] helo=mail.zytor.com) by casper.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TQOR4-0003kE-UC for kexec@lists.infradead.org; Mon, 22 Oct 2012 20:17:22 +0000 Message-ID: <5085A9A8.5020004@zytor.com> Date: Mon, 22 Oct 2012 13:16:40 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH v1 2/2] x86, apic: Disable BSP if boot cpu is AP References: <20121016043357.20003.5885.stgit@localhost6.localdomain6> <20121016043528.20003.601.stgit@localhost6.localdomain6> <873916i88t.fsf@xmission.com> In-Reply-To: <873916i88t.fsf@xmission.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Eric W. Biederman" 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 , tglx@linutronix.de, mingo@elte.hu, vgoyal@redhat.com On 10/22/2012 01:04 PM, Eric W. Biederman wrote: > HATAYAMA Daisuke 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 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec