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 A129CC3DA6F for ; Thu, 17 Aug 2023 18:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354184AbjHQSB7 (ORCPT ); Thu, 17 Aug 2023 14:01:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354171AbjHQSBf (ORCPT ); Thu, 17 Aug 2023 14:01:35 -0400 Received: from NAM12-DM6-obe.outbound.protection.outlook.com (mail-dm6nam12on2088.outbound.protection.outlook.com [40.107.243.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 36908FD; Thu, 17 Aug 2023 11:01:33 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=T1D7J676WTK/mIbUPoMtoboFJ06CftFnVPAX7vzJbC+o8IFA2kGbP8KIVaUgM+asVhbfTNjRXHWs4yc5TopBFxb0b17HFIh4SWjrC2ZaujJ+7R9/ZRQw4uWuRPO2BTu/RPgJr6B+kcRCiqHKdRRpU54wkaJWnpgA70nXGMM3utJpJuAnrPMLHIdkwczjHH0SDzDKnYgZgUMk7uwcd8WeDu6cl766VhAEJY1el8SA2YdiK6jUCfZj6t9WztDRjLWoK5eh6Lvuz5i4QHnZIU0jumhJcL0AUSjylflMw0wG1pzn47cZpW2E6cdqawiqFkgIsR5wa0hb072nOj7Q0kCB6w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=ezh92LY7oJW8E5AHPSH8zKa8X0jwZ35+w5/6xX/Hi8Y=; b=fcEll3soF8KAtxe6m+YsalOKCAikbQ4Ilp/QFZz0ccOrWHwfPv8HZ5/Jc2Bqgc6vcrPVxL9SO5Ojhn37iMyBcl+qdf6oZzHGg+lb++3bgacEE3Xj3OhnEP8l76sf9DXlDS6bR9B0x3mznEFrtiYDIYHnX8Tjl4z46XQMTBd6HrUjxKDDN5kFVJAO404ZZu5utmsCFzlyTQwH86MieR8/RfnqFf8l95OJU1KKNuWet88juuabeshcQw7dyKMRDMkxtb7/50Gug7EEKQvbWS8wWY4xItnfxQ9+9xvSpMtceQaCzs6uZAiRv4vJtnxzF6UdGaJ+5h1dRn5xzVWHO+/flA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=ezh92LY7oJW8E5AHPSH8zKa8X0jwZ35+w5/6xX/Hi8Y=; b=M/dKqlr8eKWJLZXBDs0ExWElajJQhnOq2ZFQ6gPKP2ipqdepP8Oz9sJXsX4iYEIoczTkZRyB3ozba+dRQ17Jl9afNdivOIvMkwn1ycr6ViZDfuX0xVSg36IXG3LmVCOh4HiDszNunhP6SXUkQ5sOf+JDTGIt3xz/jSChn7Eb3kz/Mu0BLOVoTRWCRNjWjbvZfztHBwueIIeo67X9HKQfhLx1jlLXH/tpDNrfzrNaSvfyHa9xjKkuffCFRirPwwQlSIwQjhvL2tTPub1nk4nXmEK2/H3jMeT6souPbJ5+pIKogID45zwJTleWrAK4+7dRA+UTrU1UQpQJHf8SKGWQ2w== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) by DM6PR12MB4220.namprd12.prod.outlook.com (2603:10b6:5:21d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6678.31; Thu, 17 Aug 2023 18:01:31 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::5111:16e8:5afe:1da1]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::5111:16e8:5afe:1da1%6]) with mapi id 15.20.6678.031; Thu, 17 Aug 2023 18:01:31 +0000 Date: Thu, 17 Aug 2023 15:01:30 -0300 From: Jason Gunthorpe To: Stefan Hajnoczi Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Alex Williamson Subject: Re: [PATCH v3] vfio: align capability structures Message-ID: References: <20230809203144.2880050-1-stefanha@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230809203144.2880050-1-stefanha@redhat.com> X-ClientProxiedBy: BL0PR02CA0125.namprd02.prod.outlook.com (2603:10b6:208:35::30) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|DM6PR12MB4220:EE_ X-MS-Office365-Filtering-Correlation-Id: d75f8875-49ae-437c-928e-08db9f4bfc6f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(39860400002)(136003)(376002)(366004)(346002)(396003)(1800799009)(451199024)(186009)(83380400001)(66556008)(38100700002)(66476007)(6916009)(66946007)(316002)(478600001)(2906002)(41300700001)(8676002)(4326008)(8936002)(5660300002)(6512007)(6506007)(6486002)(26005)(2616005)(86362001)(36756003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?IotqXTc+3cCayhGYcXhtoovD4BYVQbEy7dl8NsmvDZhK7dwnuRqTkATr4DkR?= =?us-ascii?Q?5nSNsSP7slarpeYswIRo/axUXBOkef6cBHnKwwJRVrUj0lyzEwgh1grfXB7K?= =?us-ascii?Q?oiBfGNmKu2+zNcUnZrB84rWtjr05PTSHpiVVL6188V7zgBWnGmvzcCYHdqOm?= =?us-ascii?Q?0AyhLgRM6uECHOa5AHJfKzRtEDxwdMjz68pQrNseH5D9lUkGmrSsh6qUKIzi?= =?us-ascii?Q?CXQMhMPogx7Amr8uGMxFa7lAbascsCt/gjpmlMUWv+2k8M6+ziz6jD+pkCXI?= =?us-ascii?Q?OTtZyQGDZTYpYcbp4kefsulF2NSPJTl0USYKiZyiKyFuE+NoYByDyqZSCm22?= =?us-ascii?Q?xdpDzuDAcsiyW9c5+e+eOqwuYC5sRLDFmeFWgJYcOBhhQKb2bVmjEntxSquz?= =?us-ascii?Q?XcLBqCmJ+izYjAbK3iCEvhFMwO1vUkhG3GRZh8rA5Yr/pGqY/DZlMWCmJRFk?= =?us-ascii?Q?bncik2liXvwH2VYRX7rIpmw6GAs9Sj22KIVojc01LOYvMRjexBRNNF4U/Iwz?= =?us-ascii?Q?EaPBpDFlA65cIkkkdg4+Wx13y8bEXx++5Jdfha7yAjclGcGyMpeE80zY2qDe?= =?us-ascii?Q?GeKoNi8NYkH8dvwxg+eXrrDOqWOln3leWlmxXZj71Df72xsHdq9wtAbRvsJ+?= =?us-ascii?Q?0KVXQnjvO/Yy0JxsVWwqiDP5Gh/ovLSh9ETFPpa3apCpGp0g6QM0ovxnqiBB?= =?us-ascii?Q?Iy3P8akDT6CHbcrDF1v0UczWzc6zeNj2FXvJjg1Ls5sycrT/tyewy/sjsgWj?= =?us-ascii?Q?QOa3wLIdbqSxDlCAmNTqhbPfeEvJ6H/IY2qZVgTp4r+8nuvxWhtd/jQMmiGv?= =?us-ascii?Q?Td+wqz9Gqgo8MoMsjnFfZPJJZJKzxUwY29LizhqAQWc5xh37ufYT64yWGMXU?= =?us-ascii?Q?uYCopYDQi6XSKEkupq49DJp+fhEyaRrOtAe95pCgFdLfot+DTtQmo99++wqu?= =?us-ascii?Q?B4JZxv9hnR92TDMx3APDPVdif/IVM/xInJgrODgdljBVDlsTTueXrDkecYOb?= =?us-ascii?Q?Sm/g39HmLRH/frHoxv2DfNQcpmiXzIlWPGvUsHAMyj1YS4PR5n3hmbUD1Y1g?= =?us-ascii?Q?jWIfDVEpN5Ne3Gr35vJxLqHP0VcFFxTAYtmeNX/HLn46iaEkEJRvcLBVm+RN?= =?us-ascii?Q?N24DUi44kn4YXIbeg70hTI+wtNJ6zLibMChbH0TFtKgv9d4oyQUdtVwlW1p2?= =?us-ascii?Q?yt6kh1Sbt8rAuNNku4KrVBpiQxL+vamYUFOEMvmsNTIq5Io3aIpQQKt6h8zS?= =?us-ascii?Q?/vZS+XnvELyPZNuhAAbrkZVcdSXWe2Jtr10r+rcCBo8l8XXJSQoR3GZIulsm?= =?us-ascii?Q?MrjRItqlpiB7GuURRyBOV8j5HfjO2vgdT7Juzk+ahQ4xPtQ75JJ5b5AzoXuv?= =?us-ascii?Q?Ucx58zPW26wIpg4Y4BCgPVSbhgDOR4LNDqaZ+rg1uxw1nI3YfwIfF13qj1Aa?= =?us-ascii?Q?RjlyGwgr56C9+Jf7DWwhNebVOpYZDXtTiFWo6hn9+k3y0KuwpMX1gWekJIYt?= =?us-ascii?Q?SOt0JgPlq9/NgwTTzfsNzZYYLicJXjH8SUFTfoLDKXSWtMTYZmPsImnxfBJp?= =?us-ascii?Q?PLEt+fiiSNhmMVZNeQ920+biZM7zELzjXfiFzu3w?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d75f8875-49ae-437c-928e-08db9f4bfc6f X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Aug 2023 18:01:31.3087 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: hv4YyTsAlkfTl3Jb/rc+ykf5q+xb5ZTkWLvVQZKfPGh7R4AFVqn+9gPhBfaa+8i/ X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4220 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Aug 09, 2023 at 04:31:44PM -0400, Stefan Hajnoczi wrote: > The VFIO_DEVICE_GET_INFO, VFIO_DEVICE_GET_REGION_INFO, and > VFIO_IOMMU_GET_INFO ioctls fill in an info struct followed by capability > structs: > > +------+---------+---------+-----+ > | info | caps[0] | caps[1] | ... | > +------+---------+---------+-----+ > > Both the info and capability struct sizes are not always multiples of > sizeof(u64), leaving u64 fields in later capability structs misaligned. > > Userspace applications currently need to handle misalignment manually in > order to support CPU architectures and programming languages with strict > alignment requirements. > > Make life easier for userspace by ensuring alignment in the kernel. This > is done by padding info struct definitions and by copying out zeroes > after capability structs that are not aligned. > > The new layout is as follows: > > +------+---------+---+---------+-----+ > | info | caps[0] | 0 | caps[1] | ... | > +------+---------+---+---------+-----+ > > In this example caps[0] has a size that is not multiples of sizeof(u64), > so zero padding is added to align the subsequent structure. > > Adding zero padding between structs does not break the uapi. The memory > layout is specified by the info.cap_offset and caps[i].next fields > filled in by the kernel. Applications use these field values to locate > structs and are therefore unaffected by the addition of zero padding. > > Note that code that copies out info structs with padding is updated to > always zero the struct and copy out as many bytes as userspace > requested. This makes the code shorter and avoids potential information > leaks by ensuring padding is initialized. > > Originally-by: Alex Williamson > Signed-off-by: Stefan Hajnoczi > --- > v3: > - Also align capability structs in drivers/iommu/iommufd/vfio_compat.c > [Jason] > > include/uapi/linux/vfio.h | 2 ++ > drivers/iommu/iommufd/vfio_compat.c | 2 ++ > drivers/vfio/pci/vfio_pci_core.c | 11 ++--------- > drivers/vfio/vfio_iommu_type1.c | 11 ++--------- > drivers/vfio/vfio_main.c | 6 ++++++ > 5 files changed, 14 insertions(+), 18 deletions(-) Acked-by: Jason Gunthorpe Jason