From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932791AbbLGUAd (ORCPT ); Mon, 7 Dec 2015 15:00:33 -0500 Received: from mail.skyhub.de ([78.46.96.112]:45581 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932542AbbLGUAc (ORCPT ); Mon, 7 Dec 2015 15:00:32 -0500 Date: Mon, 7 Dec 2015 21:00:19 +0100 From: Borislav Petkov To: Ashok Raj Cc: linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, Tony Luck Subject: Re: [Patch V2] x86, mce: Ensure offline CPU's don't participate in mce rendezvous process. Message-ID: <20151207200019.GH22248@pd.tnic> References: <20151205002930.GA24005@otc-brkl-03.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20151205002930.GA24005@otc-brkl-03.jf.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 04, 2015 at 07:29:36PM -0500, Ashok Raj wrote: > Linux has logical cpu offline capability. That can be triggered by: > > # echo 0 > /sys/devices/system/cpu/cpuX/online > > In Intel Architecture, MCE's are broadcasted to all CPUs in the system. > > This includes the CPUs marked offline by Linux. Unless the CPU's were removed > via an ACPI notification, in which case the cpu's are removed from the > cpu_present_map. > > This patch ensures offline CPU's don't participate in MCE rendezvous, but > simply perform clearing some status bits to ensure a second MCE wont cause > automatic shutdown. > > Without the patch, mce_start will increment mce_callin, but mce_start would > only wait for all online_cpus. So offline cpu's should avoid participating > in the rendezvous process. > > Reviewed-by: Tony Luck > Cc: stable@vger.kernel.org > Signed-off-by: Ashok Raj > --- > arch/x86/kernel/cpu/mcheck/mce.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) Tested on a box here, massaged commit message and queued for 4.4, thanks. --- From: Ashok Raj Date: Thu, 3 Dec 2015 19:16:10 -0500 Subject: [PATCH] x86/mce: Ensure offline CPUs don't participate in rendezvous process Intel's MCA implementation broadcasts MCEs to all CPUs on the node. This poses a problem for offlined CPUs which cannot participate in the rendezvous process: Kernel panic - not syncing: Timeout: Not all CPUs entered broadcast exception handler Kernel Offset: disabled Rebooting in 100 seconds.. More specifically, Linux does a soft offline of a CPU when writing a 0 to /sys/devices/system/cpu/cpuX/online, which doesn't prevent the #MC exception from being broadcasted to that CPU. Ensure that offline CPUs don't participate in the MCE rendezvous and clear the RIP valid status bit so that a second MCE won't cause a shutdown. Without the patch, mce_start() will increment mce_callin and wait for all CPUs. Offlined CPUs should avoid participating in the rendezvous process altogether. Reviewed-by: Tony Luck Signed-off-by: Ashok Raj Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: linux-edac Cc: stable@vger.kernel.org Cc: Thomas Gleixner Cc: x86-ml Link: http://lkml.kernel.org/r/1449188170-3909-1-git-send-email-ashok.raj@intel.com [ Massage commit message. ] Signed-off-by: Borislav Petkov --- arch/x86/kernel/cpu/mcheck/mce.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 3865e95cc5ec..a006f4cd792b 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1002,6 +1002,17 @@ void do_machine_check(struct pt_regs *regs, long error_code) int flags = MF_ACTION_REQUIRED; int lmce = 0; + /* If this CPU is offline, just bail out. */ + if (cpu_is_offline(smp_processor_id())) { + u64 mcgstatus; + + mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); + if (mcgstatus & MCG_STATUS_RIPV) { + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); + return; + } + } + ist_enter(regs); this_cpu_inc(mce_exception_count); -- 2.3.5 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.