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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E8DF8C2D0DB for ; Sat, 25 Jan 2020 21:42:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0F332071E for ; Sat, 25 Jan 2020 21:42:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728901AbgAYVme (ORCPT ); Sat, 25 Jan 2020 16:42:34 -0500 Received: from mga17.intel.com ([192.55.52.151]:41904 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726937AbgAYVme (ORCPT ); Sat, 25 Jan 2020 16:42:34 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jan 2020 13:42:34 -0800 X-IronPort-AV: E=Sophos;i="5.70,363,1574150400"; d="scan'208";a="222914741" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.68]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jan 2020 13:42:34 -0800 Date: Sat, 25 Jan 2020 13:42:32 -0800 From: "Luck, Tony" To: Borislav Petkov Cc: Peter Zijlstra , Thomas Gleixner , Arvind Sankar , "Christopherson, Sean J" , Ingo Molnar , "Yu, Fenghua" , Ingo Molnar , H Peter Anvin , "Raj, Ashok" , "Shankar, Ravi V" , linux-kernel , x86 Subject: Re: [PATCH v15] x86/split_lock: Enable split lock detection by kernel Message-ID: <20200125214232.GA17914@agluck-desk2.amr.corp.intel.com> References: <20200123004507.GA2403906@rani.riverdale.lan> <20200123035359.GA23659@agluck-desk2.amr.corp.intel.com> <20200123044514.GA2453000@rani.riverdale.lan> <20200123231652.GA4457@agluck-desk2.amr.corp.intel.com> <87h80kmta4.fsf@nanos.tec.linutronix.de> <20200125024727.GA32483@agluck-desk2.amr.corp.intel.com> <20200125104419.GA16136@zn.tnic> <20200125195513.GA15834@agluck-desk2.amr.corp.intel.com> <20200125201221.GZ11457@worktop.programming.kicks-ass.net> <20200125203312.GE4369@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200125203312.GE4369@zn.tnic> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 25, 2020 at 09:33:12PM +0100, Borislav Petkov wrote: > On Sat, Jan 25, 2020 at 09:12:21PM +0100, Peter Zijlstra wrote: > > My thinking was Virt, virt likes to mess up all msr expectations. > > My only worry is to have it written down why we're doing this so that it > can be changed/removed later, when we've forgotten all about split lock. > Because pretty often we look at a comment-less chunk of code and wonder, > "why the hell did we add this in the first place." Ok. I added a comment: * Use the "safe" versions of rdmsr/wrmsr here because although code * checks CPUID and MSR bits to make sure the TEST_CTRL MSR should * exist, there may be glitches in virtualization that leave a guest * with an incorrect view of real h/w capabilities. -Tony