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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 CA38DC432C0 for ; Thu, 21 Nov 2019 21:51:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6EF32068E for ; Thu, 21 Nov 2019 21:51:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726921AbfKUVv1 (ORCPT ); Thu, 21 Nov 2019 16:51:27 -0500 Received: from mga05.intel.com ([192.55.52.43]:33229 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726329AbfKUVv1 (ORCPT ); Thu, 21 Nov 2019 16:51:27 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Nov 2019 13:51:26 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,227,1571727600"; d="scan'208";a="210049893" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.68]) by orsmga003.jf.intel.com with ESMTP; 21 Nov 2019 13:51:26 -0800 Date: Thu, 21 Nov 2019 13:51:26 -0800 From: "Luck, Tony" To: Peter Zijlstra Cc: Ingo Molnar , Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Ashok Raj , Ravi V Shankar , linux-kernel , x86 Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Message-ID: <20191121215126.GA9075@agluck-desk2.amr.corp.intel.com> References: <1574297603-198156-1-git-send-email-fenghua.yu@intel.com> <1574297603-198156-7-git-send-email-fenghua.yu@intel.com> <20191121060444.GA55272@gmail.com> <20191121130153.GS4097@hirez.programming.kicks-ass.net> <20191121131522.GX5671@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191121131522.GX5671@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 21, 2019 at 02:15:22PM +0100, Peter Zijlstra wrote: > Also, just to remind everyone why we really want this. Split lock is a > potent, unprivileged, DoS vector. So how much do we "really want this"? It's been 543 days since the first version of this patch was posted. We've made exactly zero progress. Current cut down patch series is the foundation to move one small step towards getting this done. Almost all of what's in this set will be required in whatever final solution we want to end up with. Out of this: Documentation/admin-guide/kernel-parameters.txt | 10 +++ arch/x86/include/asm/cpu.h | 5 + arch/x86/include/asm/cpufeatures.h | 2 arch/x86/include/asm/msr-index.h | 8 ++ arch/x86/include/asm/traps.h | 3 + arch/x86/kernel/cpu/common.c | 2 arch/x86/kernel/cpu/intel.c | 72 ++++++++++++++++++++++++ arch/x86/kernel/traps.c | 22 +++++++ 8 files changed, 123 insertions(+), 1 deletion(-) the only substantive thing that will *change* is to make the default be "on" rather than "off". Everything else we want to do is *additions* to this base. We could wait until we have those done and maybe see if we can stall out this series to an even thousand days. Or, we can take the imperfect base and build incrementally on it. You've expressed concern about firmware ... with a simple kernel command line switch to flip, LUV (https://01.org/linux-uefi-validation) could begin testing to make sure that firmware is ready for the big day when we throw the switch from "off" to "on". -Tony