Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756859AbbLDXIX (ORCPT ); Fri, 4 Dec 2015 18:08:23 -0500 Received: from mga14.intel.com ([192.55.52.115]:52851 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755114AbbLDXIW (ORCPT ); Fri, 4 Dec 2015 18:08:22 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,382,1444719600"; d="scan'208";a="700521685" Date: Fri, 4 Dec 2015 19:08:21 -0500 From: "Raj, Ashok" To: Andy Lutomirski Cc: "Luck, Tony" , Borislav Petkov , "linux-kernel@vger.kernel.org" , "linux-edac@vger.kernel.org" Subject: Re: [Patch V0] x86, mce: Ensure offline CPU's don't participate in mce rendezvous process. Message-ID: <20151205000821.GA13059@otc-brkl-03.jf.intel.com> References: <1449188170-3909-1-git-send-email-ashok.raj@intel.com> <20151204143404.GF21177@pd.tnic> <20151204171419.GA4870@otc-brkl-03.jf.intel.com> <20151204165112.GI21177@pd.tnic> <3908561D78D1C84285E8C5FCA982C28F39F78AD9@ORSMSX114.amr.corp.intel.com> <20151204173633.GK21177@pd.tnic> <3908561D78D1C84285E8C5FCA982C28F39F78D9F@ORSMSX114.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 1434 Lines: 30 On Fri, Dec 04, 2015 at 02:34:52PM -0800, Andy Lutomirski wrote: > On Fri, Dec 4, 2015 at 9:53 AM, Luck, Tony wrote: > > ist_enter() is black magic to me. Andy? Would you be worried about executing > > ist_{enter,exit}() on a cpu that was once online, but is currently marked offline > > by Linux? > > Offline CPUs are black magic to me. But as long as the CPU works the > way that the normal specs say it should, then ist_enter is fair game. > In any event, if context tracking blows up on an offline CPU, I'd > argue that's a context tracking bug and needs to be fixed. > > But maybe offlined CPUs are supposed to have all interrupts off > (including MCE?) and the argument goes the other way? Dunno. MCE's are broadcast by the hardware and cannot be blocked. Offline is only a Linux specific state. Now if the offline was a result of an ACPI event (eject) that triggered the CPU removal (offline in Linux, as it would have in a platform that supports true hotplug) then the platform would remove this cpu from the broadcast list. if kernel were to set CR4.MCE=0 that would cause system shutdown when an MCE is broadcast and hits this cpu. Cheers, Ashok -- 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/