From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53C8DC43142 for ; Thu, 21 Jun 2018 22:43:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A0F6224EA for ; Thu, 21 Jun 2018 22:43:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0A0F6224EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934196AbeFUWng (ORCPT ); Thu, 21 Jun 2018 18:43:36 -0400 Received: from mga02.intel.com ([134.134.136.20]:33494 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934071AbeFUWmd (ORCPT ); Thu, 21 Jun 2018 18:42:33 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jun 2018 15:42:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,253,1526367600"; d="scan'208";a="59935162" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga002.fm.intel.com with ESMTP; 21 Jun 2018 15:42:32 -0700 Date: Thu, 21 Jun 2018 15:42:03 -0700 From: Fenghua Yu To: Dave Hansen Cc: Peter Zijlstra , Fenghua Yu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Ashok Raj , Rafael Wysocki , Tony Luck , Alan Cox , Ravi V Shankar , Arjan van de Ven , linux-kernel , x86 Subject: Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses Message-ID: <20180621224203.GA18979@romley-ivt3.sc.intel.com> References: <1527435965-202085-1-git-send-email-fenghua.yu@intel.com> <20180621193738.GA13636@worktop.programming.kicks-ass.net> <20180621201851.GC114883@romley-ivt3.sc.intel.com> <20180621220003.GD114883@romley-ivt3.sc.intel.com> <20180621220844.GB2494@hirez.programming.kicks-ass.net> <6fbff2df-96c9-db51-371b-a23d1a84d070@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6fbff2df-96c9-db51-371b-a23d1a84d070@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 21, 2018 at 03:18:19PM -0700, Dave Hansen wrote: > On 06/21/2018 03:08 PM, Peter Zijlstra wrote: > > On Thu, Jun 21, 2018 at 03:00:03PM -0700, Fenghua Yu wrote: > >> The control knob for kernel is to choose re-executing the faulting > >> instruction (default) or kernel panic. Kernel panic may be useful in hard > >> real time which has less tolerant to bad performance. > > The kernel should never trigger this, ever. Any #AC is a plain bug and > > should be fixed. So unconditional WARN+disable is suffient. > > It sounds like we need to start with that functionality and then if > Fenghua wants to do more, we have add-on patches that can be evaluated > by themselves. For split lock in kernel, by default, I just do warning, disable feature in #AC handler, continue to execute the faulting instruction, and re-enable #AC for split lock after a delay. This is the default behavior in the current patches. By "WAR+disable", you mean I just do this default behavior and remove the control knob? Thanks. -Fenghua