From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BL0PR03CU003.outbound.protection.outlook.com (mail-eastusazon11012064.outbound.protection.outlook.com [52.101.53.64]) (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 6C54B377A92; Sat, 26 Sep 2026 21:59:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.53.64 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790459999; cv=fail; b=p0b2bSLdftr4n2pCnZhk12AFxjjlgEQ8k25QkM+XaKtMtp9mcuGdjueSMKh+0E7TcAXOLQsUlVB3kLfRWX9dg69o/hlM4uqbI277AgtwedLedPqh/bIgM7Au7mVFG3JXmI7MjU7MPk5dNhlXTiItEvu54JHgF2TTRFtDZcOag0Q= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790459999; c=relaxed/simple; bh=ka+onTMj1FAv6+9GWOtLFebO75B7wmJULDsg9xOXYBo=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=gF72vsOcUCks2B5igjmL08z4BQKRHVFMBhoHjAO9XKdG9N7w31CmGELv66sxwjkVq4zt0yDo7R2V1H1jhsQL502M47tzAky5ELL9EoIihOYOUL5P1BIKLVMT72npKWoFq+mkp7l2KzRFw5bAOczum6oaj1Lb46V+mjIC1ZICiu0= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=InR/1BVX; arc=fail smtp.client-ip=52.101.53.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="InR/1BVX" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=tB8bODIGjTg44YS3uXCGvIYtYKAjLvGiM2rXVntJIOiTMTHoJKKZuN/IoMBvhrOXRlhOmURBnfViVpe2INwwGMr7sFKM4d0qD6qTjHE+SvOBwHmIY3HxUcryD9M8/bXuVxsd3s5V6tt8GX5G46OjGxA5ocusWC4d6FUDbu8MJfe6XpC7nOCmfgaJZh6XIo4R+6Z6eKNJ2ozF4NhP0TKeEyYGLy3w0MEcEPZOJefbCul3hi67XUEOn+KINBAgVosQjJzp3wVfctU2mixMLR5MOdDkaICK9br0rC64MuIABmaaB5YnenRcny3WQaY2K4pvd+u1gzlbq2jVHaokbJbXjQ== 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=dU4hRNAhUZQalFVqpZnwQ3K/8Fy0vUZ+kzJTfqIhKVo=; b=KgVZNGzlQcb3iqeTxAgQd0Cd4/aN9nBQ1FVO6QRUm2JNXRUh4U3g18xqtskOzx6DRD4S16Ppfiik/K0WBMOflm2xMyDL64DIlryq7ctJsTvxYCs1y6lBCu7yilIc4AEA1x23s6k6uiqBLCTGUHamPpONagSrojSlVGMOX+kuh0rLf9U7/8hb960hZAU4OiUJFmMc7olIugOZ+UNU03UupTRlgoXUp3oLL5RjWhZG89b1poPV7P07LHTfwZA9g7o87YiorFp8Fig5U0+8UFTZ/3pY4Y98olNMsqNLZ2H0QEmdpMgmz3uTNZ/zpi2Mu4ks+841vajwrvbMng7NJ0kBwA== 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=dU4hRNAhUZQalFVqpZnwQ3K/8Fy0vUZ+kzJTfqIhKVo=; b=InR/1BVX++ru8EuiMVEGbZlmAnGwr2+RKNo0C7eydFqRQ3mR2RGUKUMMF3yu6aQaMWDwG1sHlOZvDzh92QrD2evP0k92S6y2W3yW1TTLWsXWpIABq0GXOAT7TgAIkThWU0PP3JLnNVJztrsvoPLyx79uP5kFuun/Q/nHF4B4H5Frl7TwKjoUXvU4xu06fKF+0rmGADGSAeK9J5zzhmC1d8j5w11IIFdQhPCE/pJ8A3DsBsevGooiUlJgP2L6Wosh3mWQkG2ME/6HO/T9U43biBrzG+1dWmElD2tbRzC5XfezlQ6rbxLGnCt/eg6n34NKvDYJbM6dubZh03GHJUJt9w== Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DM6PR12MB4827.namprd12.prod.outlook.com (2603:10b6:5:1d6::14) by DM4PR12MB6470.namprd12.prod.outlook.com (2603:10b6:8:b8::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.451.18; Sat, 26 Sep 2026 21:59:54 +0000 Received: from DM6PR12MB4827.namprd12.prod.outlook.com ([fe80::6261:3040:864b:159c]) by DM6PR12MB4827.namprd12.prod.outlook.com ([fe80::6261:3040:864b:159c%3]) with mapi id 15.21.0451.014; Sat, 26 Sep 2026 21:59:54 +0000 Date: Sat, 26 Sep 2026 23:59:45 +0200 From: Andrea Righi To: sashiko-reviews@lists.linux.dev Cc: sched-ext@lists.linux.dev Subject: Re: [PATCH v2 sched_ext/for-7.4] sched_ext: cid: Represent clusters explicitly Message-ID: References: <20260926212017.3351797-1-arighi@nvidia.com> <20260926213437.5FAC91F000FF@smtp.kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260926213437.5FAC91F000FF@smtp.kernel.org> X-ClientProxiedBy: MI1P293CA0006.ITAP293.PROD.OUTLOOK.COM (2603:10a6:290:2::16) To DM6PR12MB4827.namprd12.prod.outlook.com (2603:10b6:5:1d6::14) Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6PR12MB4827:EE_|DM4PR12MB6470:EE_ X-MS-Office365-Filtering-Correlation-Id: 6c10ccba-c781-41f4-75a8-08df1c197ee5 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|366016|376014|1800799024|11063799006|10067099003|56012099006|4143699003|18002099003|22082099003; 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:DM6PR12MB4827.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(23010399003)(366016)(376014)(1800799024)(11063799006)(10067099003)(56012099006)(4143699003)(18002099003)(22082099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?B2QtO0fu0ozxhy56c+cY0arkooyaxV5wtw2wysv4onFDQuxzXlTn+/CUj+qI?= =?us-ascii?Q?dc6hpUkhBMvV5v3AZ2KMIe6FHIfaHbTKd9xDHJdwMu+NyDGQEsqo8Xsta+1N?= =?us-ascii?Q?ivfCMs/8fcsh/nqKjCqnfQVWrbeJ03yCwSzGHP3rTxlJOL3YstQoY88feoyO?= =?us-ascii?Q?+jxnGQF5+257NPsoMdYXlOMNYYtUl3bAWRiMndIFUhK9bfnlMmFBWvOqYWP8?= =?us-ascii?Q?5YBTJIJQyf/jMaXYaWWb6NeDOtrxYBAJ9U0p2GKnMD9WhCzWURiYO5ibZ6KU?= =?us-ascii?Q?MCwN+PU8k+BE8eTo0miKxUGo9KJWZXpL9FJLe+bJM7o2I9J82r5eJceCcZ/+?= =?us-ascii?Q?jo7vp/poljvA6o0Zp4bQzJlTXp8krBola6ZcfR7jDg8hNk9pkK98oLWXfBqh?= =?us-ascii?Q?48Ijaafq4vK1IvvfOhxChnwEnKFtNHcXzmNpjNC2VajJw1Xn2AmbwdJccqfG?= =?us-ascii?Q?B/Z+ehmO4jNX0t5VMWJdWPtattlt3rxCI2//2WemPF1yYrBlR71v6dzMufn8?= =?us-ascii?Q?yhttV8+N1J3TiLFOsIIaqxmZvi062wlJmXLuGund9j6db/8xAWjFN7qQ/a4s?= =?us-ascii?Q?ZrYf4jjlKBwzHAHvxdpkcD2Q8v+V9up9h36LHNtrTZ+YqraVPh7OFa/wj0Jd?= =?us-ascii?Q?m210UGiigxUdNk1tR5lUX1Ns6C7QC4OfphfwEe1fzqMHFuPsGWExHVG9bcip?= =?us-ascii?Q?gGzmQIQi0xgmwgO/IXApSil0IRyBTHUVbIUizvA7ODpv22mTyUutCCU1RIjk?= =?us-ascii?Q?+rY9ZnHuym5lVih20MoCe3kRK2OiU032g8rpIh9ZdM2z9JrEiLOwqyVW0icN?= =?us-ascii?Q?KlV7YCxenpDV8Ok5P8raAc47NVoI0GtI5vv441JbjHzqe9TXGxFKnNWr8aLo?= =?us-ascii?Q?KKv5sf49cIK/lG7g73AE9shXRq0Um+q3McAhkY4tpyYfibBIrpPZ/pHEhRxd?= =?us-ascii?Q?TsGtS3mH2OwdzLSO3/5pBLdWD47tj2xrEgRCXbEU0FZGPshM8GWBuIlhFuBo?= =?us-ascii?Q?o7Zuzkb7SxnrJ6MH0SamJHyBh3hAfQskVfq+g8FWMxRUOdGuN2btc//QoQKu?= =?us-ascii?Q?G3TmvA25s2Tusfd4+oVp9oIncGDScbSXkrLNA/HHc2Kg/ZLFbPCo//LNyosx?= =?us-ascii?Q?rK7hM9xM/VtR0F7wOeL3Bailz9d9rgH+qvfKP/mVaa/21Ms502jKHZzbMHhx?= =?us-ascii?Q?7C5Te4tIg9Ze1pR76lT5BtP3dochhplIhKco1mNgbXIrOuOnQmyviUXDEs6S?= =?us-ascii?Q?48WktGlrgcsXUP7no3+NBkgNZcd/SJacNn1977nU76hPhU4YGz81dAkP5Hju?= =?us-ascii?Q?Y9N+IbD32xzn3d4vTFkB+3BfPVDqPkYNCrYV5v4oWitOI4H1FGGB4sc2YpQn?= =?us-ascii?Q?NtiLX34eghEHlFbdAMAL3H81ZmtvCCVXpK/Oj3slHrEXtMr6XGwQ+ZKdyXbP?= =?us-ascii?Q?tZL8x8E22ENTZfb8aNTYl80jwFTPbnk407oCzmFVjmGoC7SqR5J/A3/bCNEY?= =?us-ascii?Q?BIE+gSOJuyzjChxO7Z714WoRRmvxLB4E5gxrc5ZfuFWCBxIj+XPc46G0FKwC?= =?us-ascii?Q?VAblrUAEmHhPGbsgWO+X6xqzy3Tmat8XpT1+mplsKeqxkOLGv6U3C/GQFX4p?= =?us-ascii?Q?zVTDhDoyTr1PQE9MTYoqNDs22uk9MKtpjfvHBNFVqIl7mNaZ5qkbZZ8y4gPD?= =?us-ascii?Q?R81UQJ6ypswkEOHA5W9NUEBT5komGU3KEItQogU2HQEPD8miQODX8XUUnGsP?= =?us-ascii?Q?IudKNXvGkA=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6c10ccba-c781-41f4-75a8-08df1c197ee5 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB4827.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Sep 2026 21:59:54.0230 (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: jlCJkabIUb1dvoRHkZm1rUXYwkFBLP8mYonUUQ6cF4aeOwVGtwVU9PrvtDojePmEb1yaNhSAjFuoCJ0uTmjslQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6470 On Sat, Sep 26, 2026 at 09:34:37PM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Critical] bpf: scx_bpf_cid_topo UAPI break due to struct scx_cid_topo size change > -- > > commit fb59a730e3e34d8a0c1fda134fb4459d8183c802 > Author: Andrea Righi > > sched_ext: cid: Represent clusters explicitly > > This commit adds explicit cluster representation to the sched_ext CID > topology. It modifies the cid calculation logic and updates > struct scx_cid_topo to include cluster_cid and cluster_idx. > > Link: https://lore.kernel.org/r/20260926152306.3190774-1-arighi@nvidia.com > > > diff --git a/kernel/sched/ext/types.h b/kernel/sched/ext/types.h > > index 943d8d429a2c9..765d7b9208144 100644 > > --- a/kernel/sched/ext/types.h > > +++ b/kernel/sched/ext/types.h > > [ ... ] > > > @@ -88,6 +95,8 @@ struct scx_cid_topo { > > s32 node_idx; > > s32 shard_cid; > > s32 shard_idx; > > + s32 cluster_cid; > > + s32 cluster_idx; > > }; > > [Severity: Critical] > Will adding cluster_cid and cluster_idx break existing BPF schedulers that > call scx_bpf_cid_topo()? > > By increasing the size of struct scx_cid_topo from 32 to 40 bytes, the > expected argument size for the kfunc changes. Since scx_bpf_cid_topo() > lacks a size-aware __sz parameter or compatibility wrapper: > > kernel/sched/ext/cid.c:scx_bpf_cid_topo() { > ... > *out__uninit = topo[cid]; > } > > Could the BPF verifier strictly reject older BPF schedulers passing a > 32-byte allocation because out__uninit demands the current kernel's BTF size? > > Furthermore, if the check were somehow bypassed, would the assignment cause > an 8-byte out-of-bounds write into BPF stack or map memory? > > Does this constitute a hard ABI break for existing userspace binaries since > they lack a deprecation path or versioning wrapper? For the records, as specified in the changelog of the patch, this is fixed by: https://lore.kernel.org/r/fa6479d36b528573565ca22914451317@kernel.org. -Andrea