From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759272AbcIRSjN (ORCPT ); Sun, 18 Sep 2016 14:39:13 -0400 Received: from mail.skyhub.de ([78.46.96.112]:46430 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758832AbcIRSjE (ORCPT ); Sun, 18 Sep 2016 14:39:04 -0400 Date: Sun, 18 Sep 2016 20:39:05 +0200 From: Borislav Petkov To: "Luck, Tony" Cc: Yinghai Lu , the arch/x86 maintainers , Linux Kernel Mailing List , "linux-edac@vger.kernel.org" , Yinghai Lu Subject: Re: [RFC PATCH] x86: Do not panic if mce=2 is passed Message-ID: <20160918183905.GB331@nazgul.tnic> References: <20160916202325.4972-1-yinghai@kernel.org> <3908561D78D1C84285E8C5FCA982C28F3A1DE102@ORSMSX114.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <3908561D78D1C84285E8C5FCA982C28F3A1DE102@ORSMSX114.amr.corp.intel.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 16, 2016 at 08:28:44PM +0000, Luck, Tony wrote: > > For UE recovery support, current we need mce=2 in command line > > and also disable panic_on_oops with sysctl. > > Please explain. I've never given mce=2 on command line, and have > had my kernel recover from thousands of (injected) UE memory errors. So frankly, that panic_on_oops doesn't make a whole lotta sense to me. It is promoting MCEs with severity MCE_UC_SEVERITY and higher to a panic. So let's look at those: MCE_UC_SEVERITY, - we don't do anything special in the kernel for those so just as well. MCE_AR_SEVERITY, - those end up in the memory failure code if they're memory errors MCE_PANIC_SEVERITY, - causes panic so if anything, panic_on_oops shouldn't control the panicking behavior as tolerant does that already: * Tolerant levels: * 0: always panic on uncorrected errors, log corrected errors * 1: panic or SIGBUS on uncorrected errors, log corrected errors * 2: SIGBUS or log uncorrected errors (if possible), log corr. errors * 3: never panic or SIGBUS, log all errors (for testing only) IOW, I think that patch makes sense but please doublecheck my logic above first. Thanks. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --