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 F3921C352A3 for ; Tue, 11 Feb 2020 14:34:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0723206D7 for ; Tue, 11 Feb 2020 14:34:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730197AbgBKOeQ convert rfc822-to-8bit (ORCPT ); Tue, 11 Feb 2020 09:34:16 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:20942 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727818AbgBKOeP (ORCPT ); Tue, 11 Feb 2020 09:34:15 -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-54-dctIXTQ8O5OXh04oyb3tqA-1; Tue, 11 Feb 2020 14:34:11 +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; Tue, 11 Feb 2020 14:34:11 +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; Tue, 11 Feb 2020 14:34:11 +0000 From: David Laight To: 'Xiaoyao Li' , Paolo Bonzini , Thomas Gleixner , Sean Christopherson , Ingo Molnar , "Borislav Petkov" , Andy Lutomirski CC: "x86@kernel.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write Thread-Topic: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write Thread-Index: AQHV4OP68X/A1Fe8pUKXUjVj7zr1z6gWDhjw Date: Tue, 11 Feb 2020 14:34:11 +0000 Message-ID: <973e772012ce4f0f9a689fe33608236a@AcuMS.aculab.com> References: <20200203151608.28053-1-xiaoyao.li@intel.com> <20200203151608.28053-4-xiaoyao.li@intel.com> <95d29a81-62d5-f5b6-0eb6-9d002c0bba23@redhat.com> <878sl945tj.fsf@nanos.tec.linutronix.de> In-Reply-To: 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: dctIXTQ8O5OXh04oyb3tqA-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: 11 February 2020 14:03 ... > Alright, I don't know the history of TEST_CTRL, there is a bit 31 in it > which means "Disable LOCK# assertion for split locked access" when set. > Bit 31 exists for a long period, but linux seems not use it so I guess > it may be a testing purpose bit. My brain remembers something about some system just ignoring locked accesses for misaligned transfers. Trouble is it was probably nearly 30 years ago and there are no details coming out of 'long term storage'. It might be that some systems I had either set this bit or acted as if it was set. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)