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 51446C33C9E for ; Thu, 30 Jan 2020 12:31:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D71920702 for ; Thu, 30 Jan 2020 12:31:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727110AbgA3Mbv convert rfc822-to-8bit (ORCPT ); Thu, 30 Jan 2020 07:31:51 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:35122 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727001AbgA3Mbu (ORCPT ); Thu, 30 Jan 2020 07:31:50 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-78-nO0nl3ftMxusiiUxHSydGw-1; Thu, 30 Jan 2020 12:31:47 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 30 Jan 2020 12:31:44 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Thu, 30 Jan 2020 12:31:44 +0000 From: David Laight To: 'Xiaoyao Li' , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Paolo Bonzini , "Sean Christopherson" CC: "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" Subject: RE: [PATCH 1/2] KVM: x86: Emulate split-lock access as a write Thread-Topic: [PATCH 1/2] KVM: x86: Emulate split-lock access as a write Thread-Index: AQHV12hLFMkYqgCTIEO98IqgYw6YoagDIpWg Date: Thu, 30 Jan 2020 12:31:44 +0000 Message-ID: References: <20200130121939.22383-1-xiaoyao.li@intel.com> <20200130121939.22383-2-xiaoyao.li@intel.com> In-Reply-To: <20200130121939.22383-2-xiaoyao.li@intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: nO0nl3ftMxusiiUxHSydGw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xiaoyao Li > Sent: 30 January 2020 12:20 > If split lock detect is enabled (warn/fatal), #AC handler calls die() > when split lock happens in kernel. > > 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. That doesn't seem right if, for example, the locked access is addx. ISTM it would be better to force an immediate fatal error of some kind than just corrupt the guest memory. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)