From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753469AbZDLSMy (ORCPT ); Sun, 12 Apr 2009 14:12:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752062AbZDLSMo (ORCPT ); Sun, 12 Apr 2009 14:12:44 -0400 Received: from fg-out-1718.google.com ([72.14.220.153]:53888 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751901AbZDLSMo (ORCPT ); Sun, 12 Apr 2009 14:12:44 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=py142Cn5o4RnxdZerFdZj14lxjWcTi2wVkt3IQBl14vW0BZlp2qlA+eXeXTeuYHi96 Bp4DRNy7d/ASCzkljml8Aiyk/YFTrSzB29tFXkGJhZw33tuFz38zvK8STgKI60WfBGk/ w4Y+OcvYS5Va6rlWhZNxfz9u/UO8hVwEDBDeQ= Date: Sun, 12 Apr 2009 22:12:39 +0400 From: Cyrill Gorcunov To: Ingo Molnar Cc: hpa@zytor.com, tglx@linutronix.de, xemul@openvz.org, yhlu.kernel@gmail.com, linux-kernel@vger.kernel.org, macro@linux-mips.org, andi@firstfloor.org Subject: Re: [rfc 0/4] x86 - apic dummy ops with cleanups Message-ID: <20090412181239.GE6942@lenovo> References: <20090412164738.967602112@openvz.org> <20090412172431.GA26459@elte.hu> <20090412180014.GD6942@lenovo> <20090412180239.GA3489@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090412180239.GA3489@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Ingo Molnar - Sun, Apr 12, 2009 at 08:02:39PM +0200] | | * Cyrill Gorcunov wrote: | | > Thanks, Ingo! | > | > Actually I found one a bit suspicious thing (not sure if it was | > initially designed to behave like that). | > | > Suppose we have SMP compiled kernel and even supported on HW level | > but then we disable apic thru kernel option. And then when system | > startup it should be working fine since we go to uniprocessor | > mode. Then the machine going for reboot and we have: | > | > Starting from arch/x86/kernel/reboot.c | > | > native_machine_shutdown | > smp_send_stop | > smp_ops.smp_send_stop | > native_smp_send_stop | > disable_local_APIC | > apic_write(APIC_SPIV, value); | > | > Since we have reserved APIC memory mapped area (in _anycase_) it | > doesn't cause any problems but was it initially supposed? | | i dont think that was supposed so. If the APIC wasnt even enabled | then we shouldnt try to disable it. Note that there are a few | unusual paths to APIC enablement: for example by twiddling the | nmi_watchdog knob in /proc/sys - or in theory through a CPU hotplug | event. | | Ingo | Ugh... I expected something like "No, look at that code! You've missed this snippet!". Which would make me happy :-) I'll take a look. Cyrill