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,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 0E49CC10DCE for ; Wed, 25 Mar 2020 00:43:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AB44206F8 for ; Wed, 25 Mar 2020 00:43:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727239AbgCYAnH (ORCPT ); Tue, 24 Mar 2020 20:43:07 -0400 Received: from mga02.intel.com ([134.134.136.20]:50926 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727110AbgCYAnH (ORCPT ); Tue, 24 Mar 2020 20:43:07 -0400 IronPort-SDR: alN7Zp/saue5gOkOyX1Ba3Tg524duSalNTbPCMbr8bPqTl8Twum4p2HOGF0palRj/DLbtLWssV yvVnrKVlB3Bg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 17:43:06 -0700 IronPort-SDR: 5x9pluvj3vih6iam46DUyNlA84aL25H7zFoleAvJSJQXRW2uzeJq6xIWhww3X5E7Nr8FaVNC95 PuubS928RoYg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,302,1580803200"; d="scan'208";a="446454348" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.249.170.28]) ([10.249.170.28]) by fmsmga005.fm.intel.com with ESMTP; 24 Mar 2020 17:43:02 -0700 Subject: Re: [PATCH v5 3/9] x86/split_lock: Re-define the kernel param option for split_lock_detect 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> <20200315050517.127446-4-xiaoyao.li@intel.com> <87r1xjov3a.fsf@nanos.tec.linutronix.de> <87r1xidoj1.fsf@nanos.tec.linutronix.de> From: Xiaoyao Li Message-ID: <54b2b9b5-2307-b5da-6b63-319e9626bcc1@intel.com> Date: Wed, 25 Mar 2020 08:43:01 +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: <87r1xidoj1.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 6:40 PM, Thomas Gleixner wrote: > Xiaoyao Li writes: >> On 3/24/2020 1:10 AM, Thomas Gleixner wrote: >>> Xiaoyao Li writes: >>> >>>> Change sld_off to sld_disable, which means disabling feature split lock >>>> detection and it cannot be used in kernel nor can kvm expose it guest. >>>> Of course, the X86_FEATURE_SPLIT_LOCK_DETECT is not set. >>>> >>>> Add a new optioin sld_kvm_only, which means kernel turns split lock >>>> detection off, but kvm can expose it to guest. >>> >>> What's the point of this? If the host is not clean, then you better fix >>> the host first before trying to expose it to guests. >> >> It's not about whether or not host is clean. It's for the cases that >> users just don't want it enabled on host, to not break the applications >> or drivers that do have split lock issue. > > It's very much about whether the host is split lock clean. > > If your host kernel is not, then this wants to be fixed first. If your > host application is broken, then either fix it or use "warn". > My thought is for CSPs that they might not turn on SLD on their product environment. Any split lock in kernel or drivers may break their service for tenants.