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=-1.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 00822C43331 for ; Tue, 24 Mar 2020 11:51:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C59BB20870 for ; Tue, 24 Mar 2020 11:51:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727337AbgCXLv0 (ORCPT ); Tue, 24 Mar 2020 07:51:26 -0400 Received: from mga03.intel.com ([134.134.136.65]:2897 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727066AbgCXLvZ (ORCPT ); Tue, 24 Mar 2020 07:51:25 -0400 IronPort-SDR: IM2lJRtS7FizZg8tbY0NNQIKsCDxTL6/j5HutJV1zPzm7wMSSJ7gcy3bnSuczrCe/k/Qr4bjhw BSFFuWCmidPw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 04:51:25 -0700 IronPort-SDR: 4NeQXEQVZQq9wxOWEzgjsdjrdaWE32X2663rhZruOpKxRR7PERlSHOxJ+3KSFASTMRzbv/GXtK 0Hq3GY9QNxkg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,300,1580803200"; d="scan'208";a="270356888" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.255.31.120]) ([10.255.31.120]) by fmsmga004.fm.intel.com with ESMTP; 24 Mar 2020 04:51:20 -0700 Subject: Re: [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of split lock detection To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , hpa@zytor.com, Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Peter Zijlstra , Arvind Sankar , Fenghua Yu , Tony Luck , Vitaly Kuznetsov , Jim Mattson References: <20200315050517.127446-1-xiaoyao.li@intel.com> <20200315050517.127446-2-xiaoyao.li@intel.com> <87zhc7ovhj.fsf@nanos.tec.linutronix.de> From: Xiaoyao Li Message-ID: <95093fb0-df88-0543-c7eb-32b94ac4f99e@intel.com> Date: Tue, 24 Mar 2020 19:51:19 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <87zhc7ovhj.fsf@nanos.tec.linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/24/2020 1:02 AM, Thomas Gleixner wrote: > Xiaoyao Li writes: > >> Current initialization flow of split lock detection has following issues: >> 1. It assumes the initial value of MSR_TEST_CTRL.SPLIT_LOCK_DETECT to be >> zero. However, it's possible that BIOS/firmware has set it. > > Ok. > >> 2. X86_FEATURE_SPLIT_LOCK_DETECT flag is unconditionally set even if >> there is a virtualization flaw that FMS indicates the existence while >> it's actually not supported. >> >> 3. Because of #2, KVM cannot rely on X86_FEATURE_SPLIT_LOCK_DETECT flag >> to check verify if feature does exist, so cannot expose it to >> guest. > > Sorry this does not make anny sense. KVM is the hypervisor, so it better > can rely on the detect flag. Unless you talk about nested virt and a > broken L1 hypervisor. > Yeah. It is for the nested virt on a broken L1 hypervisor.