Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754397AbcJERPD (ORCPT ); Wed, 5 Oct 2016 13:15:03 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:25183 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752829AbcJERPC (ORCPT ); Wed, 5 Oct 2016 13:15:02 -0400 From: Boris Ostrovsky To: david.vrabel@citrix.com, jgross@suse.com Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, andrew.cooper3@citrix.com, Boris Ostrovsky , stable@vger.kernel.org Subject: [PATCH] xen/x86: Update topology map for PV VCPUs Date: Wed, 5 Oct 2016 13:09:33 -0400 Message-Id: <1475687373-14589-1-git-send-email-boris.ostrovsky@oracle.com> X-Mailer: git-send-email 1.8.3.1 X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1563 Lines: 48 Early during boot topology_update_package_map() computes logical_pkg_ids for all present processors. Later, when processors are brought up, identify_cpu() updates these values based on phys_pkg_id which is a function of initial_apicid. On PV guests the latter may point to a non-existing node, causing logical_pkg_ids to be set to -1. Intel's RAPL uses logical_pkg_id (as topology_logical_package_id()) to index its arrays and therefore in this case will point to index 65535 (since logical_pkg_id is a u16). This could lead to either a crash or may actually access random memory location. As a workaround, we recompute topology during CPU bringup to reset logical_pkg_id to a valid value. (The reason for initial_apicid being bogus is because it is initial_apicid of the processor from which the guest is launched. This value is CPUID(1).EBX[31:24]) Signed-off-by: Boris Ostrovsky Cc: stable@vger.kernel.org --- Copying Andrew for the CPUID part. arch/x86/xen/smp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 311acad..9fa27ce 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -87,6 +87,12 @@ static void cpu_bringup(void) cpu_data(cpu).x86_max_cores = 1; set_cpu_sibling_map(cpu); + /* + * identify_cpu() may have set logical_pkg_id to -1 due + * to incorrect phys_proc_id. Let's re-comupte it. + */ + topology_update_package_map(apic->cpu_present_to_apicid(cpu), cpu); + xen_setup_cpu_clockevents(); notify_cpu_starting(cpu); -- 1.8.3.1