From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082AbdAZSN2 (ORCPT ); Thu, 26 Jan 2017 13:13:28 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:27056 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753405AbdAZSNU (ORCPT ); Thu, 26 Jan 2017 13:13:20 -0500 From: Mohit Gambhir Organization: Oracle Corporation To: Boris Ostrovsky , jgross@suse.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/xen: Fix APIC id mismatch warning on Intel Message-ID: Date: Thu, 26 Jan 2017 13:12:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch fixes the following warning message seen when booting the kernel as Dom0 with Xen on Intel machines. [0.003000] [Firmware Bug]: CPU1: APIC id mismatch. Firmware: 0 APIC: 1] The code generating the warning in validate_apic_and_package_id() matches cpu_data(cpu).apicid (initialized in init_intel()-> detect_extended_topology() using cpuid) against the apicid returned from xen_apic_read(). Now, xen_apic_read() makes a hypercall to retrieve apicid for the boot cpu but returns 0 otherwise. Hence the warning gets thrown for all but the boot cpu. The idea behind xen_apic_read() returning 0 for apicid is that the guests (even Dom0) should not need to know what physical processor their vcpus are running on. This is because we currently do not have topology information in Xen and also because xen allows more vcpus than physical processors. However, boot cpu's apicid is required for loading xen-acpi-processor driver on AMD machines. Look at following patch for details: commit 558daa289a40 ("xen/apic: Return the APIC ID (and version) for CPU 0.") So to get rid of the warning, this patch modifies xen_cpu_present_to_apicid() to return cpu_data(cpu).apicid instead of calling xen_apic_read(). The warning is not seen on AMD machines because init_amd() populates cpu_data(cpu).apicid by calling hard_smp_processor_id()->xen_apic_read() as opposed to using apicid from cpuid as is done on Intel machines. Signed-off-by: Mohit Gambhir --- arch/x86/xen/apic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c index 44c88ad..bcea81f 100644 --- a/arch/x86/xen/apic.c +++ b/arch/x86/xen/apic.c @@ -145,7 +145,7 @@ static void xen_silent_inquire(int apicid) static int xen_cpu_present_to_apicid(int cpu) { if (cpu_present(cpu)) - return xen_get_apic_id(xen_apic_read(APIC_ID)); + return cpu_data(cpu).apicid; else return BAD_APICID; } -- 2.9.3