From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CWXP265CU009.outbound.protection.outlook.com (mail-ukwestazon11021115.outbound.protection.outlook.com [52.101.100.115]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4B3137417D; Fri, 27 Mar 2026 12:19:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.100.115 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774613995; cv=fail; b=YC/y84igVWy5nXRmUC0IyG8Sd+nwFqx20WCjreZChZ1vGN55a1Vb/y9Lwxhz8DQOuP+2FXJ397oF8cEO1QtQs2ExgjymjthnZB6HnxFfk0qMliShXkAdtvehK+VYU3H09i6U1xXft25N9O2/ts+mwu1S88ciKtaG4cnn9d4csjs= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774613995; c=relaxed/simple; bh=O9w2vv1cO8UWioSWz2SfjhInPw0VLLcyyZBJOgWhjOA=; h=Content-Type:Date:Message-Id:Cc:Subject:From:To:References: In-Reply-To:MIME-Version; b=CbGq1HQAbzqEIyynhVQQAG0UVFtT9j4TgtCFwpLQkm6+IvN6CCPtLCtxU/+ufXR2uW8cts2vjXYvX7N37x66/glr5HXhwPWyH+QJ6edowOmwUuS0Pl8MN/odBEIxOHoyoU7XgUzz7G87bFL6kLAHPBwwrPkDHcqno/BhYnTPJiI= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net; spf=pass smtp.mailfrom=garyguo.net; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b=viCS229L; arc=fail smtp.client-ip=52.101.100.115 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=garyguo.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b="viCS229L" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=q7paV+kMoy8IKHTXLwlnqNJsrD2WTCTKiftbYbVkDDRaED/kukPOx6Ujx6MdXNekUWXV/BIcZqrKu4qfpypCdJ8SjjB9nAzOg5QOH1v/3Fcu9UuatEQS7Vk7itp41makmcpEK4PNjMLwzK4GXy9axvB9ukIc4JDsH1Qf4C6AuiI/MJPzCTY6GB82HkxmI5drHR/jcT7f9IXzePCv8G+ypTZBZ+zhHboGJzaSkJd8MuqDNsnkgPHJZslr8JKfEp/Cfye3F4+Tf4QORpn/+fFAiQsEJMNylgIl/QMi1J7lsJa9YRVyCsE5MTJlfslq8uJisH50avMkgppN9RnVUHFHwA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=rxCD3NtjYZ5S//WV5seCOEwTI/dZySB5LMNUiowrw0M=; b=SxwmxqAldYo8cBIFJ7P7HS9NaE9GsjWDO7n5AVUhnwDPAnVxVpPwv0H37pT4YAFOEfwIsBnQUY+mDtJ2XsoOBVIQXQyw1QrkwKg9i5lhvUkxhE5kTKFVL2RWlD8oL69qNekW9IJkMp6xmnz9Pb63rJpnbtoZ+O6Z+3hcgPIYdJ8eqIyZvzSyB8fRQp9PxQNM69FCGqfMPogOeKlHMmxmDVegksZljJ5zcorGLYuN3307fdAVC+5adC1vbb88+dx6fxOAN8DzDB+XUDC4rbChhnPWbm+IzahQjqIi/ggl2z3wxaLItdpnDxiPvg1x6ykUm6O8Zm2CqxEPzHy4ElrCiA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=garyguo.net; dmarc=pass action=none header.from=garyguo.net; dkim=pass header.d=garyguo.net; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=garyguo.net; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=rxCD3NtjYZ5S//WV5seCOEwTI/dZySB5LMNUiowrw0M=; b=viCS229LEyoB9E7mbarBHSj64jhs0p+3e7ft61o4HYnvvPlENN6Ffen922wBxeIN/g1RVzGS+QsUmL3HEyjapluyhzfedyuM0jC8M1x2FKVTNMnvYR9gQFdkOguDVRy4W7VYhZ2LPL5uPfoINDQr1/uNBZs4lsj8NcNNIL8GSxs= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=garyguo.net; Received: from LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:488::16) by CW1P265MB7552.GBRP265.PROD.OUTLOOK.COM (2603:10a6:400:216::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9745.23; Fri, 27 Mar 2026 12:19:50 +0000 Received: from LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM ([fe80::1c3:ceba:21b4:9986]) by LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM ([fe80::1c3:ceba:21b4:9986%5]) with mapi id 15.20.9745.022; Fri, 27 Mar 2026 12:19:49 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 27 Mar 2026 12:19:49 +0000 Message-Id: Cc: , , , Subject: Re: [PATCH 6/8] rust: io: add `read_val` and `write_val` function on I/O view From: "Gary Guo" To: "Andreas Hindborg" , "Gary Guo" , "Miguel Ojeda" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Alice Ryhl" , "Trevor Gross" , "Danilo Krummrich" , "Abdiel Janulgue" , "Daniel Almeida" , "Robin Murphy" , "Nathan Chancellor" , "Nick Desaulniers" , "Bill Wendling" , "Justin Stitt" X-Mailer: aerc 0.21.0 References: <20260323153807.1360705-1-gary@kernel.org> <20260323153807.1360705-7-gary@kernel.org> <877bqxy96y.fsf@t14s.mail-host-address-is-not-set> In-Reply-To: <877bqxy96y.fsf@t14s.mail-host-address-is-not-set> X-ClientProxiedBy: LO2P265CA0397.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:f::25) To LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:488::16) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LOVP265MB8871:EE_|CW1P265MB7552:EE_ X-MS-Office365-Filtering-Correlation-Id: b58f0b60-16d7-4b39-0679-08de8bfb2465 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|10070799003|1800799024|56012099003|22082099003|18002099003|921020; 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:LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(366016)(10070799003)(1800799024)(56012099003)(22082099003)(18002099003)(921020);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?MnVDTVAzVXN6ZDdYZWdRUzNhdjNETXp0VUhBSW5tQVV0c2Nnb1RnRitSbWpm?= =?utf-8?B?SkhmM1pCUDFkM1NwVUc4U01obk1LczFDcTNSVnRYamgxK2Z3YWRoUUVkM0Uw?= =?utf-8?B?aDVQbXgyUFJEaGV2Rytoem8xQnNrcnN0ZWhqVXhUT2hjc0lHL1draW94Z2Rh?= =?utf-8?B?WTJIY1pZeWFHRTYwYWgxcG9tZUplNzJheFlFM2kyNGN2L2lObVdsc3hTVkw3?= =?utf-8?B?TEhZcjRpWHdaUnBtV3ZPMlFCOEpNUWhnS0tNMHZuTUdjQnJOcUVvNDZjWFU5?= =?utf-8?B?Q0FJRWdsd0t2QjBrL2N2NU5hWi9DQjhoQlMzbG4wSWEwVVRERmxhMHEvTkEw?= =?utf-8?B?Tm5IOWhmUnBINHZKamdXbGllcXBQVHdVZW9qdUpEcU1zNHZDOFZBQTFydldl?= =?utf-8?B?YWFVMldmUVorYmdxSjFsOXFzZzlMYXMwMWlJTXkzUjhGSnNxOERPS3pCTEFG?= =?utf-8?B?K2VZblhkWDdmdjVpSUQ2ZFdwU3BVRWV0QU1LcHN2WFYwRi9oR2NqdVQycndy?= =?utf-8?B?YUFOb2NDQUZGNFVBL3MxN2VwYTVXZHNCbGM2QndSaWU1dzdCS0llODl3ZHVQ?= =?utf-8?B?ZENUVVlqNitVOHdCbEZESzVoekZkU3dUWDR3Z2Z0NXFaUHV3MStiN09ncDI2?= =?utf-8?B?Y0puYU5Ya3hwQWxyaEU4Wk4rWWVHOW1LTHgwRVJGNDRIUXpuemJSeTNYU2JR?= =?utf-8?B?cUtaekM3VmlkUW9WSERoQTlOSWZ1d0lTbjFSaVBlZUJkZmZxVGw0cG1DZ0dB?= =?utf-8?B?eGQ3bGNqWGJwQ25vRSt0V3lTTXFrL2R1YXBzQlZvNkYvNTExUDlremFLdDhu?= =?utf-8?B?dEVwbmpHK2dRcFd5Rm1qdWNuWTc3RTg5emlhbGYvRnFndFRSUkFoWExEOTVZ?= =?utf-8?B?cWM5Q2lKcjFRYTY2ckEwVFJvK1lyNGdjTVBPeHpLZVVoc2VQU1JkOVZzSVBL?= =?utf-8?B?bGlnaERzQ1Q5cEZIMGMremJmSnlZdDQxV1ZHU1JiaVBqdGJXaEEyODU1UE1O?= =?utf-8?B?cWNqcWpUUnlpOFpEL0c3N0ptbEpsOXllTHFzYTNSWFB3ZUhmNHptdTh6ZWJm?= =?utf-8?B?MnBWTTluZ1d6UllEVDVCRmxZcWo3aUNhOFd6b2E4RnplcXQzUFU1ejBvM1BD?= =?utf-8?B?NjY1TEpPWmF3cC9UeTBEY2lMVTR5UEpQbUpBWXZ0L2FQZEdJL2FXYmY5cGNO?= =?utf-8?B?N0ZGM2hsUGhPNkQ4WjJhRVlLL1F6dHRZQkhsa1BzU0lDaTlsUWRpZHdVMzl6?= =?utf-8?B?NTRKYnlKRkFlUkpPODhVUm5lSW5KZm9Za24wZ3VDd0xYN0o4VE1IWnRGUmla?= =?utf-8?B?am5HTFZwOTB6TFBiOVJOcTdrQlJIOTkzRTgyVGwvNDN4aXJYcDl3eXRxVmVv?= =?utf-8?B?UzJEbHdsMFkwa2tXZWV0blFmektaZzc1eEtqSCt0VVhOMGdWS20vVlRqenBJ?= =?utf-8?B?VHJEWndSamtyMjlWOVNwT3U5QnlTWEFjYUhkWHZwd1dEakk3VFpWTjBuaVBR?= =?utf-8?B?dm5MNVArNlR2Zmo3Z0tSZVU4c0RRQUVFMzg1MDlYOHR2T1ZkSTd5aHRUMCtF?= =?utf-8?B?L1B1QlRyQVVYSUhIcWhxNVB3NXJIZkZjV2wvcVN2bVVoajZWK0R6UG90VWpl?= =?utf-8?B?ZmhIczlVdXRGVVR0dStyMm41UHhEMmtMSzkrUk1ZUjZVMnYreEE4bWs5cTNh?= =?utf-8?B?akQvNXJaUys4QTVXVW05dXdLNW12TFYreFJ6TW1TbWZoWG9JZ1YyaHNVMFlx?= =?utf-8?B?dWVyNVVsNUtsWHQ1VEx0TzZsWXMwSW5KWldlQjlsd0QyMlJPS0s3OG4xVWVU?= =?utf-8?B?c0xkT2FmL2FXVCtJaTQwTU8xMTJoU0JFYzNzVjZ5SFREWWlnaTMrL01sTFZj?= =?utf-8?B?ZDdmcURkVmJuT3N6d29FU1NqL2VEc0wxUFllT1FuTUFCY0FxSUV0U1ozZUV4?= =?utf-8?B?VzQzWHR2VEJ0aG0xWkMyN3VLWmkxOG0yYmozMUp1VGZQQ2RJa3A0ZVJpUG9M?= =?utf-8?B?VHRJMkRsK013cFBFL0JNUjNFbWt0Ny9wbEtkbzNpT1RrRjZuekN6SGx3ZE4v?= =?utf-8?B?SSttaE8rcDBNTm1SQVFXdjJvVXVqckxzbUxPWHFyeFVtY05mQ3pnMXdtcms0?= =?utf-8?B?eFpxMDZyeVVaZUJWRldJa25IdkpqWUhiUkQvMTdCeDlPK2RwdEV5akhCU0ZT?= =?utf-8?B?VDk0VWZuTlZHN1VSb3ViYTJlbWFLMUR4dHZxVytRRm1RaGhtLzlXVExSRU12?= =?utf-8?B?NnRCNnlpdi92eU54bWpXaE1GZmU2WHZka1phSHhFMEZuTkNSTGtsSmJMK3JJ?= =?utf-8?B?WmFRcVlXdWFvR0J5OVhpVEV4emJ5ai94RjlYNHZEdW0yYmg2dXdUZz09?= X-OriginatorOrg: garyguo.net X-MS-Exchange-CrossTenant-Network-Message-Id: b58f0b60-16d7-4b39-0679-08de8bfb2465 X-MS-Exchange-CrossTenant-AuthSource: LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Mar 2026 12:19:49.8133 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: mUYI2ZsADYsvO2KjAapcU/p4RRdQqXlL1zjQd9YkU2sTiB6Rsd93Ksb+2RQK3TyprshPnVUXyGOxSMAdrSH2cA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CW1P265MB7552 On Fri Mar 27, 2026 at 8:21 AM GMT, Andreas Hindborg wrote: > "Gary Guo" writes: > >> From: Gary Guo >> >> When a view is narrowed to just a primitive, these functions provide a w= ay >> to access them using the `IoCapable` trait. This is used to provide >> `io_read!` and `io_write!` macros, which are generalized version of curr= ent >> `dma_read!` and `dma_write!` macro (that works on `Coherent` only, but n= ot >> subview of them, or other I/O backends). >> >> For DMA coherent objects, `IoCapable` is only implemented for atomically >> accessible primitives; this is because `read_volatile`/`write_volatile` = can >> behave undesirably for aggregates; LLVM may turn them to multiple >> instructions to access parts and assemble, or could combine them to a >> single instruction. >> >> The ability to read/write aggregates (when atomicity is of no concern), >> could be implemented with copying primitives (e.g. memcpy_{from,to}io) i= n >> the future. >> >> Signed-off-by: Gary Guo >> --- >> rust/kernel/dma.rs | 40 +++++++++++++++++++ >> rust/kernel/io.rs | 95 ++++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 135 insertions(+) >> >> diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs >> index ae2939abc166..fcdf85f5ed50 100644 >> --- a/rust/kernel/dma.rs >> +++ b/rust/kernel/dma.rs >> @@ -877,6 +877,46 @@ fn as_ptr(&self) -> *mut Self::Type { >> } >> } >> >> +/// Implements [`IoCapable`] on `Coherent` for `$ty` using `read_volati= le` and `write_volatile`. >> +macro_rules! impl_coherent_io_capable { >> + ($(#[$attr:meta])* $ty:ty) =3D> { >> + $(#[$attr])* >> + impl IoCapable<$ty> for Coherent { >> + #[inline] >> + unsafe fn io_read(&self, address: *mut $ty) -> $ty { >> + // SAFETY: >> + // - By the safety precondition, the address is within = bounds of the allocation and >> + // aligned. >> + // - Using read_volatile() here so that race with hardw= are is well-defined. >> + // - Using read_volatile() here is not sound if it race= s with other CPU per Rust >> + // rules, but this is allowed per LKMM. > > You are not covering how we satisfy "Reading from src must produce a > properly initialized value of type T." I assume you need a bound on `T: F= romBytes`? The macro is only used for primitives. I'll add a line explaining that next= version. Best, Gary