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=-7.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 DE371C433E0 for ; Thu, 30 Jul 2020 16:22:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B817320842 for ; Thu, 30 Jul 2020 16:22:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730006AbgG3QWm convert rfc822-to-8bit (ORCPT ); Thu, 30 Jul 2020 12:22:42 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:57305 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728415AbgG3QWm (ORCPT ); Thu, 30 Jul 2020 12:22:42 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-168-pSkYNQ8ZO5WTrpGnSW1Ncw-1; Thu, 30 Jul 2020 17:22:38 +0100 X-MC-Unique: pSkYNQ8ZO5WTrpGnSW1Ncw-1 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 Jul 2020 17:22:38 +0100 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 Jul 2020 17:22:38 +0100 From: David Laight To: 'Joerg Roedel' , Paolo Bonzini CC: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Tom Lendacky , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Borislav Petkov , Joerg Roedel Subject: RE: [PATCH v2 4/4] KVM: SVM: Use __packed shorthand Thread-Topic: [PATCH v2 4/4] KVM: SVM: Use __packed shorthand Thread-Index: AQHWZohC3H9k40HxxUaQvBycA7RPyakgTMJw Date: Thu, 30 Jul 2020 16:22:38 +0000 Message-ID: <230e4cc785ff49a38c028474dcfc9c36@AcuMS.aculab.com> References: <20200730154340.14021-1-joro@8bytes.org> <20200730154340.14021-5-joro@8bytes.org> In-Reply-To: <20200730154340.14021-5-joro@8bytes.org> 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com 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: Joerg Roedel > Sent: 30 July 2020 16:44 > > From: Borislav Petkov > > Use the shorthand to make it more readable. ... > diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h > index 8744817358bf..6b4b43f68f4b 100644 > --- a/arch/x86/include/asm/svm.h > +++ b/arch/x86/include/asm/svm.h > @@ -150,14 +150,14 @@ struct __attribute__ ((__packed__)) vmcb_control_area { > #define SVM_NESTED_CTL_NP_ENABLE BIT(0) > #define SVM_NESTED_CTL_SEV_ENABLE BIT(1) > > -struct __attribute__ ((__packed__)) vmcb_seg { > +struct vmcb_seg { > u16 selector; > u16 attrib; > u32 limit; > u64 base; > -}; > +} __packed; Why are they marked 'packed' at all? The above has no holes. So it would only need to be 'packed' if it might exist at an unaligned address. That only tends to happed for network messages and compatibility with old hardware definitions. While you might want an attribute for 'error if has holes' if definitely isn't __packed. For larger structures in can be worth adding a compile-time assert that the structure is the size of the associated hardware registers/structure. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)