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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6A30C7EE23 for ; Mon, 12 Jun 2023 13:18:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235307AbjFLNSW convert rfc822-to-8bit (ORCPT ); Mon, 12 Jun 2023 09:18:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51164 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234182AbjFLNSU (ORCPT ); Mon, 12 Jun 2023 09:18:20 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63400E51 for ; Mon, 12 Jun 2023 06:18:18 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-173-0FOEeq_-OMq-Pc0lsQH2SA-1; Mon, 12 Jun 2023 14:18:14 +0100 X-MC-Unique: 0FOEeq_-OMq-Pc0lsQH2SA-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Mon, 12 Jun 2023 14:18:01 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Mon, 12 Jun 2023 14:18:01 +0100 From: David Laight To: "'kirill.shutemov@linux.intel.com'" , "Huang, Kai" CC: "kvm@vger.kernel.org" , "Hansen, Dave" , "david@redhat.com" , "bagasdotme@gmail.com" , "ak@linux.intel.com" , "Wysocki, Rafael J" , "Luck, Tony" , "Chatre, Reinette" , "Christopherson,, Sean" , "pbonzini@redhat.com" , "tglx@linutronix.de" , "Yamahata, Isaku" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "Shahar, Sagi" , "peterz@infradead.org" , "imammedo@redhat.com" , "Gao, Chao" , "Brown, Len" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "Huang, Ying" , "Williams, Dan J" Subject: RE: [PATCH v11 18/20] x86: Handle TDX erratum to reset TDX private memory during kexec() and reboot Thread-Topic: [PATCH v11 18/20] x86: Handle TDX erratum to reset TDX private memory during kexec() and reboot Thread-Index: AQHZnSRWXDaSmJ22okO690LL2Ubsg6+HJc9w Date: Mon, 12 Jun 2023 13:18:01 +0000 Message-ID: References: <5aa7506d4fedbf625e3fe8ceeb88af3be1ce97ea.1685887183.git.kai.huang@intel.com> <20230609132301.uvvp27yr5kpenl6f@box.shutemov.name> <58f34b4b81b6d6b37d3386dec0f073e6eb7a97ff.camel@intel.com> <20230612075830.jbrdd6ysz4qq7wdf@box.shutemov.name> <4c7effc3abe71aa1cbee41f3bd46b97aed40be26.camel@intel.com> <20230612114843.n7vvoh7m2rk4la56@box.shutemov.name> In-Reply-To: <20230612114843.n7vvoh7m2rk4la56@box.shutemov.name> Accept-Language: en-GB, 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-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: kirill.shutemov@linux.intel.com > Sent: 12 June 2023 12:49 > > On Mon, Jun 12, 2023 at 10:27:44AM +0000, Huang, Kai wrote: > > Does it make sense? > > I understand your logic. AFAICS, it is correct (smp_mb() instead of __mb() > would be better), but it is not justified from complexity PoV. Given that x86 performs writes pretty much in code order. Do you need anything more than a compile barrier? > This lockless exercise gave me a pause to understand. > > Lockless doesn't buy you anything here, only increases complexity. > Just take a lock. Indeed... David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)