From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [Patch v2] lapic need be checked if available when initialize acpi processor id Date: Wed, 30 Apr 2014 22:13:57 +0200 Message-ID: <20009828.4TTRJo9T7a@vostro.rjw.lan> References: <1397519754-10205-1-git-send-email-bhe@redhat.com> <20140430055503.GD4774@dhcp-16-105.nay.redhat.com> <20140430060303.GE4774@dhcp-16-105.nay.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: Received: from v094114.home.net.pl ([79.96.170.134]:56181 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752432AbaD3T50 (ORCPT ); Wed, 30 Apr 2014 15:57:26 -0400 In-Reply-To: <20140430060303.GE4774@dhcp-16-105.nay.redhat.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Baoquan He Cc: linux-kernel@vger.kernel.org, lenb@kernel.org, linux-acpi@vger.kernel.org, jiang.liu@linux.intel.com, vgoyal@redhat.com On Wednesday, April 30, 2014 02:03:03 PM Baoquan He wrote: > Hi Rafael, Hi, > Thanks for previous review for v1. Later on I thought acpi_lapic is > more suitable for checking whether LAPIC in MADT is available, and it can > hanlde both the UP system running SMP kernel with no LAPIC in MADT and kdump > kernel after multiple CPUs system crashed on non-1st CPU. > > I tested the 1st case by addding "disableapic nr_cpus=1" into cmdline > of SMP kenrel, and it works. For 2nd case, it works too, below warning > message is not printed any more. > > acpi LNXCPU:0a: BIOS reported wrong ACPI id 0 for the processor > > Do you like this idea? Well, I don't hate it, but you need to make the code build in all configurations (including ia64). Thanks! > On 04/30/14 at 01:55pm, Baoquan He wrote: > > In acpi_processor_get_info(), acpi processor info is initialized including > > id, namely cpu index. Currently, if on UP system running SMP kerenl with > > no LAPIC in MADT, cpu0_initialized is checked if acpi processor id is > > initialized. > > > > However this check maybe is not correct for kdump kernel. Most of time > > only 1 CPU is supported because of known problems. So in 1st kernel > > multiple CPUs are present, then crash happened in one specific CPU, > > say 2nd CPU. Then it jump into kdump kernel with "nr_cpus=1" specified > > in cmdline. In this situation, since kdump kernel is warm reset, it will > > reuse the ACPI resource passed from crashed kernel directly, namely 1st > > kernel. It means in MADT all LAPIC is enabled while only 1 CPU is > > present in running system. The kdump kernel usually is the same as the > > crashed 1st kernel. So now in kdump kernel, x86_cpu_to_apicid stored the > > apicid and its related cpu id. If only check cpu0_initialized, it will > > assign 0 to the acpi processor id of 1st CPU, it's not correct. > > > > So in this patch, check acpi_lapic too. If acpi_lapic is 0, then LAPIC in > > MADT is not available, assigne 0 to the handling acpi processor. If > > acpi_lapic is 1, then LAPIC in MADT is available, let's get apic processor > > id from x86_cpu_to_apicid. > > > > Signed-off-by: Baoquan He > > --- > > drivers/acpi/acpi_processor.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c > > index c29c2c3..33f934d 100644 > > --- a/drivers/acpi/acpi_processor.c > > +++ b/drivers/acpi/acpi_processor.c > > @@ -267,7 +267,7 @@ static int acpi_processor_get_info(struct acpi_device *device) > > pr->apic_id = apic_id; > > > > cpu_index = acpi_map_cpuid(pr->apic_id, pr->acpi_id); > > - if (!cpu0_initialized) { > > + if (!cpu0_initialized && !acpi_lapic) { > > cpu0_initialized = 1; > > /* Handle UP system running SMP kernel, with no LAPIC in MADT */ > > if ((cpu_index == -1) && (num_online_cpus() == 1)) > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.