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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 F01DBC433DF for ; Sat, 27 Jun 2020 11:54:22 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C5F2221473 for ; Sat, 27 Jun 2020 11:54:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C5F2221473 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jp9P4-00004r-Dp; Sat, 27 Jun 2020 11:53:50 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jp9P3-0008WS-UF for xen-devel@lists.xenproject.org; Sat, 27 Jun 2020 11:53:49 +0000 X-Inumbo-ID: dce82144-b86c-11ea-8369-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id dce82144-b86c-11ea-8369-12813bfff9fa; Sat, 27 Jun 2020 11:53:49 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7AA93AF34; Sat, 27 Jun 2020 11:53:48 +0000 (UTC) Subject: Re: [PATCH v4 for-4.14 2/2] pvcalls: Document correctly and explicitely the padding for all arches To: Julien Grall , xen-devel@lists.xenproject.org References: <20200627095533.14145-1-julien@xen.org> <20200627095533.14145-3-julien@xen.org> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <82c445c0-f7fc-176f-fdac-386228cc17f5@suse.com> Date: Sat, 27 Jun 2020 13:53:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200627095533.14145-3-julien@xen.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Wei Liu , paul@xen.org, Andrew Cooper , Julien Grall , Ian Jackson , George Dunlap , Jan Beulich Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 27.06.20 11:55, Julien Grall wrote: > From: Julien Grall > > The specification of pvcalls suggests there is padding for 32-bit x86 > at the end of most the structure. However, they are not described in > in the public header. > > Because of that all the structures would be 32-bit aligned and not > 64-bit aligned for 32-bit x86. > > For all the other architectures supported (Arm and 64-bit x86), the > structure are aligned to 64-bit because they contain uint64_t field. > Therefore all the structures contain implicit padding. > > Given the specification is authoriitative, the padding will the same for s/authoriitative/authoritative/ > the all architectures. The potential breakage of compatibility is ought s/the// > to be fine as pvcalls is still a tech preview. > > As an aside, the padding sadly cannot be mandated to be 0 as they are > already present. So it is not going to be possible to use the padding > for extending a command in the future. > > Signed-off-by: Julien Grall With above fixed: Reviewed-by: Juergen Gross Juergen