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 75288C2D0DB for ; Sun, 26 Jan 2020 20:01:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44571206F0 for ; Sun, 26 Jan 2020 20:01:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726545AbgAZUBw (ORCPT ); Sun, 26 Jan 2020 15:01:52 -0500 Received: from mga09.intel.com ([134.134.136.24]:51976 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726144AbgAZUBw (ORCPT ); Sun, 26 Jan 2020 15:01:52 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Jan 2020 12:01:26 -0800 X-IronPort-AV: E=Sophos;i="5.70,366,1574150400"; d="scan'208";a="217101369" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.68]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Jan 2020 12:01:25 -0800 Date: Sun, 26 Jan 2020 12:01:24 -0800 From: "Luck, Tony" To: Andy Lutomirski Cc: Thomas Gleixner , Arvind Sankar , "Christopherson, Sean J" , Peter Zijlstra , Ingo Molnar , "Yu, Fenghua" , Ingo Molnar , Borislav Petkov , H Peter Anvin , "Raj, Ashok" , "Shankar, Ravi V" , linux-kernel , x86 , Andrew Cooper Subject: Re: [PATCH v16] x86/split_lock: Enable split lock detection by kernel Message-ID: <20200126200124.GA30377@agluck-desk2.amr.corp.intel.com> References: <3908561D78D1C84285E8C5FCA982C28F7F54887A@ORSMSX114.amr.corp.intel.com> <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> <875zgzmz5e.fsf@nanos.tec.linutronix.de> <20200125220706.GA18290@agluck-desk2.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 04:34:29PM -0800, Andy Lutomirski wrote: > Although I suppose the pile of wrmsrl_safes() in the existing patch > might be sufficient. > > All this being said, the current code appears wrong if a CPU is in the > list but does have X86_FEATURE_CORE_CAPABILITIES. Are there such > CPUs? I think either the logic should be changed or a comment should > be added. Is it really wrong? Code check the CPUID & CORE_CAPABILTIES first and believes what they say. Otherwise falls back to the x86_match_cpu() list. I don't believe we put a CPU on that list that currently says it supports CORE_CAPABILITIES. That could theoretically change with a microcode update. I doubt we'd waste microcode space to do that, but if we did, I assume we'd include the split lock bit in the newly present MSR. So behavior would not change. -Tony