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 42E0CECAAD4 for ; Mon, 29 Aug 2022 20:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230032AbiH2U2L (ORCPT ); Mon, 29 Aug 2022 16:28:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229475AbiH2U2I (ORCPT ); Mon, 29 Aug 2022 16:28:08 -0400 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF6B485A95; Mon, 29 Aug 2022 13:28:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661804886; x=1693340886; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Hq7IoHFqicjLWVzrN2IrsHJfSlIydp8W3SDB2gI7EXc=; b=deDZkS3LnbDHDO9b6XO9/pU7TzBYZOu1XBM3aTJgfmJtGuyvjB7zg1v9 HP+nryRgOE7PwoDbjm3QUuyFnEGqN287qTQThiseKQNHZBUQ2c2+T1Djj 66/EuWy1CenXJT9hAw84lJqQIzya43CCPkErQiRJykBj0LgJejigx/xDa mnKnfVvuFs/vFr4jZ0d2X8d4flOHW2ee86D+gnccuCmJVF2eOYIOqitaT bMf3v/2ypQ/29MyKP0sWNc7/KrHVzqKxpQ/PjRNCYCTX4d+yzdc/NtA/n qXXsWbFBSQgdZSpml9HigED0OG4uPv4D8C7Svu3FnOD/CS3ft+hMf+VW/ A==; X-IronPort-AV: E=McAfee;i="6500,9779,10454"; a="296268439" X-IronPort-AV: E=Sophos;i="5.93,273,1654585200"; d="scan'208";a="296268439" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 13:28:06 -0700 X-IronPort-AV: E=Sophos;i="5.93,273,1654585200"; d="scan'208";a="611432873" Received: from rlacadex-mobl.amr.corp.intel.com (HELO [10.209.116.122]) ([10.209.116.122]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 13:28:05 -0700 Message-ID: <12ab0a8a-a286-4f21-3b44-a506a6c2d008@intel.com> Date: Mon, 29 Aug 2022 13:28:05 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v11 1/3] x86/tdx: Add TDX Guest attestation interface driver Content-Language: en-US To: Sathyanarayanan Kuppuswamy , Greg Kroah-Hartman Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Shuah Khan , "H . Peter Anvin" , "Kirill A . Shutemov" , Tony Luck , Andi Kleen , Kai Huang , Wander Lairson Costa , Isaku Yamahata , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org References: <20220826150638.2397576-1-sathyanarayanan.kuppuswamy@linux.intel.com> <73b375c3-97a7-5f25-5abf-48d9ec6be2db@linux.intel.com> From: Dave Hansen In-Reply-To: <73b375c3-97a7-5f25-5abf-48d9ec6be2db@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/29/22 13:09, Sathyanarayanan Kuppuswamy wrote: > With the changed format, we avoided the holes, but it still adds 7 bytes of padding. > > Total size of struct is 32 bytes. > > struct tdx_report_req { > __u64 reportdata; /* 0 8 */ > __u64 tdreport; /* 8 8 */ > __u32 rpd_len; /* 16 4 */ > __u32 tdr_len; /* 20 4 */ > __u8 subtype; /* 24 1 */ > > /* size: 32, cachelines: 1, members: 5 */ > /* padding: 7 */ > /* last cacheline: 32 bytes */ > }; Might as well make some use of the padding and add: u8 reserved[7]; That will ensure that the entire structure is explicitly sized *AND* leave you room to add flags or other fun in the future without a new ABI.