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 15457C352A3 for ; Tue, 11 Feb 2020 13:22:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA17520675 for ; Tue, 11 Feb 2020 13:22:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728998AbgBKNW3 (ORCPT ); Tue, 11 Feb 2020 08:22:29 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:46228 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727778AbgBKNW2 (ORCPT ); Tue, 11 Feb 2020 08:22:28 -0500 Received: from [5.158.153.52] (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 1j1VUW-0000Dj-SZ; Tue, 11 Feb 2020 14:22:16 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 7124D1013B2; Tue, 11 Feb 2020 14:22:16 +0100 (CET) From: Thomas Gleixner To: Paolo Bonzini , Xiaoyao Li , Sean Christopherson , Ingo Molnar , Borislav Petkov , Andy Lutomirski Cc: x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Laight Subject: Re: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write In-Reply-To: <95d29a81-62d5-f5b6-0eb6-9d002c0bba23@redhat.com> References: <20200203151608.28053-1-xiaoyao.li@intel.com> <20200203151608.28053-4-xiaoyao.li@intel.com> <95d29a81-62d5-f5b6-0eb6-9d002c0bba23@redhat.com> Date: Tue, 11 Feb 2020 14:22:16 +0100 Message-ID: <878sl945tj.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini writes: > On 03/02/20 16:16, Xiaoyao Li wrote: >> A sane guest should never tigger emulation on a split-lock access, but >> it cannot prevent malicous guest from doing this. So just emulating the >> access as a write if it's a split-lock access to avoid malicous guest >> polluting the kernel log. > > Saying that anything doing a split lock access is malicious makes little > sense. Correct, but we also have to accept, that split lock access can be used in a malicious way, aka. DoS. > Split lock detection is essentially a debugging feature, there's a > reason why the MSR is called "TEST_CTL". So you don't want to make the The fact that it ended up in MSR_TEST_CTL does not say anything. That's where they it ended up to be as it was hastily cobbled together for whatever reason. Thanks, tglx