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,URIBL_BLOCKED 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 9A63BC18E5B for ; Wed, 25 Mar 2020 01:14:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78D252074D for ; Wed, 25 Mar 2020 01:14:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727339AbgCYBOD (ORCPT ); Tue, 24 Mar 2020 21:14:03 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:46700 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727298AbgCYBOC (ORCPT ); Tue, 24 Mar 2020 21:14:02 -0400 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jGuSb-0000rB-FO; Wed, 25 Mar 2020 02:03:57 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id E240E100C51; Wed, 25 Mar 2020 02:03:56 +0100 (CET) From: Thomas Gleixner To: Xiaoyao Li , 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 Subject: Re: [PATCH v5 3/9] x86/split_lock: Re-define the kernel param option for split_lock_detect In-Reply-To: <54b2b9b5-2307-b5da-6b63-319e9626bcc1@intel.com> 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> <54b2b9b5-2307-b5da-6b63-319e9626bcc1@intel.com> Date: Wed, 25 Mar 2020 02:03:56 +0100 Message-ID: <878sjpz1mr.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Xiaoyao Li writes: > 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. Again you are proliferating crap and making excuses for Common Sense violating Purposes (CSP). Thanks, tglx