From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752337Ab3LBO52 (ORCPT ); Mon, 2 Dec 2013 09:57:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44845 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751898Ab3LBO5Y (ORCPT ); Mon, 2 Dec 2013 09:57:24 -0500 Date: Mon, 2 Dec 2013 09:56:41 -0500 From: Vivek Goyal To: HATAYAMA Daisuke Cc: "H. Peter Anvin" , "Eric W. Biederman" , Andrew Morton , Fengguang Wu , Borislav Petkov , "kexec@lists.infradead.org" , Linux Kernel Mailing List , Jingbai Ma Subject: Re: [PATCH v8] x86, apic, kexec, Documentation: Add disable_cpu_apic kernel parameter Message-ID: <20131202145641.GB18642@redhat.com> References: <52969DA3.5070000@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52969DA3.5070000@jp.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 28, 2013 at 10:34:27AM +0900, HATAYAMA Daisuke wrote: [..] > int generic_processor_info(int apicid, int version) > { > int cpu, max = nr_cpu_ids; > - bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid, > + /* > + * boot_cpu_physical_apicid is designed to have the apicid > + * returned by read_apic_id(), i.e, the apicid of the > + * currently booting-up processor. However, on some platforms, > + * it is temporarilly modified by the apicid reported as BSP > + * through MP table. Concretely: > + * > + * - arch/x86/kernel/mpparse.c: MP_processor_info() > + * - arch/x86/mm/amdtopology.c: amd_numa_init() > + * - arch/x86/platform/visws/visws_quirks.c: MP_processor_info() > + * > + * This function is executed with the modified > + * boot_cpu_physical_apicid. So, disabled_cpu_apicid kernel > + * parameter doesn't work to disable APs on kdump 2nd kernel. > + * > + * Since fixing handling of boot_cpu_physical_apicid requires > + * another discussion and tests on each platform, we leave it > + * for now and here we use read_apic_id() directly in this > + * function, generic_processor_info(). > + */ > + bool boot_cpu_detected = physid_isset(read_apic_id(), > phys_cpu_present_map); > > + if (disabled_cpu_apicid != BAD_APICID && > + disabled_cpu_apicid != read_apic_id() && > + disabled_cpu_apicid == apicid) { > + int thiscpu = num_processors + disabled_cpus; > + > + pr_warning("ACPI: Disabling requested cpu." > + " Processor %d/0x%x ignored.\n", > + thiscpu, apicid); > + > + disabled_cpus++; > + return -ENODEV; > + } > + > /* > * If boot cpu has not been detected yet, then only allow upto > * nr_cpu_ids - 1 processors and keep one slot free for boot cpu > */ > if (!boot_cpu_detected && num_processors >= nr_cpu_ids - 1 && > - apicid != boot_cpu_physical_apicid) { > + apicid != read_apic_id()) { I thought of using read_apic_id() only for disabled_cpu_apicid case. Existing code seems to be working fine with boot_cpu_physical_apicid. Instead of converting rest of the code to read_apic_id() we should fix notion of boot_cpu_physical_id in a separate cleanup patch series. IOW, can we please use read_apic_id() only for the case of disabled_cpu_apicid and leave rest of the code untouched. And handle all the cleanup in separate patch series. Thanks Vivek