Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753505AbbLJKMp (ORCPT ); Thu, 10 Dec 2015 05:12:45 -0500 Received: from mail.skyhub.de ([78.46.96.112]:36874 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753340AbbLJKMm (ORCPT ); Thu, 10 Dec 2015 05:12:42 -0500 From: Borislav Petkov To: Ingo Molnar Cc: LKML Subject: [PATCH] x86/mce: Ensure offline CPUs don't participate in rendezvous process Date: Thu, 10 Dec 2015 11:12:26 +0100 Message-Id: <1449742346-21470-2-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.3.5 In-Reply-To: <1449742346-21470-1-git-send-email-bp@alien8.de> References: <1449742346-21470-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2296 Lines: 67 From: Ashok Raj 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: 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 c5b0d562dbf5..7e8a736d09db 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -999,6 +999,17 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/