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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D273DE7DEF8 for ; Mon, 2 Feb 2026 15:50:59 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1218723.1527566 (Exim 4.92) (envelope-from ) id 1vmwCK-0001oJ-Bc; Mon, 02 Feb 2026 15:50:44 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1218723.1527566; Mon, 02 Feb 2026 15:50:44 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1vmwCK-0001oC-7A; Mon, 02 Feb 2026 15:50:44 +0000 Received: by outflank-mailman (input) for mailman id 1218723; Mon, 02 Feb 2026 15:50:43 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1vmwCI-0001o6-V7 for xen-devel@lists.xenproject.org; Mon, 02 Feb 2026 15:50:42 +0000 Received: from PH0PR06CU001.outbound.protection.outlook.com (mail-westus3azlp170110003.outbound.protection.outlook.com [2a01:111:f403:c107::3]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id ecd9ff95-004e-11f1-b161-2bf370ae4941; Mon, 02 Feb 2026 16:50:41 +0100 (CET) Received: from CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) by CH2PR03MB5253.namprd03.prod.outlook.com (2603:10b6:610:97::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9564.15; Mon, 2 Feb 2026 15:50:38 +0000 Received: from CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343]) by CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343%4]) with mapi id 15.20.9564.016; Mon, 2 Feb 2026 15:50:38 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: ecd9ff95-004e-11f1-b161-2bf370ae4941 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=C6mgCZu5bGPBqIa9ALF4mmiLPODJ2/bSTHliSIYEcG+0qyPd2A9BYR4h0T3cWxEH1XDiys04azBbWEF5uAOxiSiAtXcuzSr6rKI7sXFf10mGACJ5mcLjbC5O92hEx5ivj4OvfC9k20breSzA5YnsJeQmPkU8rtLzC1oHFs+uXbAkHm7FsA7/f00USwmQm55fr3Yctgxv1QwY+MDx7gd5EhrPFuUWREyjaVDptpkzExlVnAV6j0Df32fNipH2z0qcTARkWef76z/FauaR5PXmqkGLd8wJloaP0PNuPghsNLd58Fn0T2hWuNrUU9naFgwhtl673AICAfMKPx19W7qUqA== 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=v+RRRC0MOrEnYrxIii09KIC60Ite75AJyfTqgG+qhec=; b=RaGQSUuWFdo3cJnb57ydR5bqGXZ4ZsZr/9ZsHktIkYWw2kk0j0NT1nna1YOs+wfJlLz6vskJWiaxMgNVk3GlYs3WHIl90QM48koJMbU0ntVH5hT6ROQjnkfDnGOBiAhrqt9z//DZnVMUQCsvaxbzLeHfZG0GFeUXDIEkcf7c4dLXdtXWMfYBepl1DH5EsAzKrhv9C5rATxwj7gB/RNksaVhmY2OS9haAKW+atBINe7sYeqqh5BIJfoZOjEcFo+a4tRtZWKrNvdOETcwBaGe/DbPt9TaDE5K4fh6IIwiTRwmW1PjJS0e9oe9QOX05HAAVQsL/1Ll69XmPLgHwXF8b8g== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=v+RRRC0MOrEnYrxIii09KIC60Ite75AJyfTqgG+qhec=; b=tYcJma2werApM5lh33g15QEzOeuSH8yzKsC19secqJX6+7pU8mlhqqqIug60kjq+sEJgkq7/ebndyd2Fxxm5f3ZAfUqiwRn8b7lf/35RM7K3AGciNTygGy/XF4XwBwHDHm3k0aInmcYXO24MuBxQAHI/p95TiZYopHvTBnKk3OM= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Mon, 2 Feb 2026 16:50:34 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper , Julien Grall , Stefano Stabellini , Anthony PERARD , Michal Orzel Subject: Re: [PATCH] CPU: abstract read-mostly-ness for per-CPU cpumask_var_t variables Message-ID: References: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: MR1P264CA0007.FRAP264.PROD.OUTLOOK.COM (2603:10a6:501:2e::12) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|CH2PR03MB5253:EE_ X-MS-Office365-Filtering-Correlation-Id: 0533687a-d0cc-4f6e-55d5-08de6272cf51 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|7053199007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Zys4NWROdkpRYUVES1ZYN01abk8vbXRtSDAwQ05uK2djV3pYZldFUXIzaXJG?= =?utf-8?B?NTc1WmV1NFBMQUNpallrQVU0MVBYV3U1SXY0c3lHVjczSHV2VDFiNXpIMHJN?= =?utf-8?B?OG5kOXdaZkVjbnVtRk5Sek5GTXduc0RNZmhXeHkxT2NWMlo0VEZoTVRVaThv?= =?utf-8?B?UmI5N3lqOUJUM0xwTkFyQnc3L3FTY3Fkc1IwU00wK1FGSGlnRDV0dlRORmVa?= =?utf-8?B?VWZHbzJhSGlIc2pMTmV0RmhHTnljUWpncStGVmlqd2NPYkNUd09nTFZHZVE4?= =?utf-8?B?a3BJdWVtOElUL0F5SHJYR1dpZEd5TkFDb0g2SDlNMWxWSXBqSVdEeDdPdHB4?= =?utf-8?B?SXZuUzJpSmV1NUl0OUlMaTFXUmo4ZjUwQmJHc2VBOUp4SWVkSUU3WkZmQUs0?= =?utf-8?B?UXNJZ2JjeFFmZHNrNXdOODM3azZYODZiZ0NNMWlzNTgyOW5NM3VvOEcvTzdD?= =?utf-8?B?b1p4VGVFZmVoVEtwYnljTTRWT0d6aEJ2dnlVL2N0K0xDbVVzU2UrS1RKcDho?= =?utf-8?B?bzNTak03OCs1eHNuRHpHT1VrbG1uUHRaNlVZUDB3OWVHOWRua2NtTktHV1JQ?= =?utf-8?B?aUVhdGwrenNXN1E2T0c5VGpnYXVJaitmMGJvNUw1WUU0SThPVGcxaWRkUk8z?= =?utf-8?B?b2s0QytCTWx5aFljM3VzT0pyclk5cm03QmhXUmRTRnJWSGFwVCtSOG9rTGlz?= =?utf-8?B?bTdZMy9OYnlJNHk1S0lURzI3ZTFUazBOWHRUalAyNGZzNWFWdWFoMlZUdHlK?= =?utf-8?B?Yk5xaGV6anVOQ0hnQWw3eFBGRFp4T0RKMFNLYzBNNk4ydU1YdmVZUmV2TW1u?= =?utf-8?B?a0FEajMzYlZJaGp5S1ZOL3J4eDVKeHpCS0QrMnF6ZXkvazZWTVdJTFo5S0xC?= =?utf-8?B?TitMQktQTXFQamkrL21kTUI0S3RmbWhhdlhNTXhkMjBuQUQ0Y3FaZ0wvQzU3?= =?utf-8?B?SHBJd3I1akc1Z1hYYU00bDMrMisrZGtvajFFYVdMN3Y2ZzU1WEhLZm9laGQr?= =?utf-8?B?YmFLSEN6Nm91eWM4K1JtamRURmhqRTZuc3FIK2tMNUVTZ1ZJVEcwTGdYRU0r?= =?utf-8?B?U2o5bXhjU1NvVnp6a21aeUhmbHhiNDV6M0szNWpFL1FDRGdMUHliU2JuVjF6?= =?utf-8?B?QWxxcGo5NTNISWJ2RkdUM0pSS1IreUFEL2ljL3VBT09JeU1VcHNQbzJiTEZD?= =?utf-8?B?a2FTZ2lydjhNRzM3UG01Mm5FbzB6ZW1uMiszSWc1L0pYblZiU1FVcTk3UmZh?= =?utf-8?B?UkNTL1lYcnVIUzNIUnE3OVV2ajdNdkhsbG9OTC9jcEZFbGpibkpHYXhxWFAv?= =?utf-8?B?S1V2N3BmYnpjV2V4NXlEbXZQUC85UCtzZ2tSc09YVlp0aDJQbVdmMUNHR1ow?= =?utf-8?B?YkpvQmxJVXNPTDM0cnYyVlNxczNsNkZaOUJZZXUwaHpGVlg2UHlHTW1ROTdn?= =?utf-8?B?SVloZWt5NUkwTFBHRkYxMG5lNTBpSkhUWmZNUEtyZzZnZXQrTk5iTmJ6QzR6?= =?utf-8?B?a01oalVKbzB0OHhFL090VGxEUVRsR0lvZE1jYnc4Z25CR01DZ3lyM29LMXhr?= =?utf-8?B?NXpEOGw0NFNqOVF0Z2sxWHFaSjJyY20wck1MbEo2eldnRVJyRWYrR1dPSmh3?= =?utf-8?B?U00wSi9Pd1QwcXJzN0RlaEFQNzF5bkxrZmI1UVZONThUc0JEV3RWdjA5S28z?= =?utf-8?B?S3Z4Q3FoZEtFSlRKVUlSRnV4Tmg2M1gyeUlYZnc1NmxvTEVvSzdaV0Q4QkFE?= =?utf-8?B?NndRV09leW5sRDVsaXpmSnAwU2VCUHA5eVZDUWN0M096Y3hiNWEzQndRL3Jm?= =?utf-8?B?QjMxSE85d3QyRGlhL2llbjV6TURPZ3hBcEQvU3JabUREMHZvVjYxMDZmb3Zy?= =?utf-8?B?cHNXNHRQTHdPeDMzQWtBVFlzR2w0Z0dWNHRVRkdBNXBEazhNcUFiWDFwV2I5?= =?utf-8?B?aEpCZThKVUVwM1g4QU50VUlSMDFPU2hWYUJ6dS9ndk5MRzZNa05Ia2xIOEdO?= =?utf-8?B?RVpGaHRrOVJpYzJxeFRGTnZzS0dHcXhWdy9vTmQ0UHFJNmdFMExCM1NjVUJB?= =?utf-8?B?Q1E5UFZzMTZzZTFyQzZRTVFveWhPb3VtZUh5dDcwMkZHSWUycldUZTdiN01s?= =?utf-8?Q?G2Xw=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(376014)(366016)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?VVpaVnFTVHJ5ZXl6dzRMcnp0YWpodFcrS1VWb09GaVJOVGFENkRhVnd4RjU2?= =?utf-8?B?Tmo3UlNnekFVYXl2a1VxTGhBczdMMjBEZTVBSmFJRWZWbHVKbnJlYW1uUDdX?= =?utf-8?B?cGZKVTZScE1NQzNmQlJQbVlkTHVTVzQ2WGxUY0x1UHNuVjE4ZVg3ZkNIdVZS?= =?utf-8?B?YVg4OHRyQjNiVFExRTYzTGxENHBPMW9SZTBvYzUyanhKbXpHWlgwQjdqYjBh?= =?utf-8?B?REROdFhpSFJEKzdhYzQvaFFCS3JLRlFwS2grS3lKK01MODRlakxwd1pIR1Y4?= =?utf-8?B?TUUxSUVkZldCcWk0M2hrVnVhMjl1NDlaVmRPc0ZmSEFMc3N6MGJLSHJvUXBK?= =?utf-8?B?SkdTY0pGa1pydHBTclJtdkk0ZVF1L1ppSWlySWY5Z2lDaHo0eTZScjZDZEhi?= =?utf-8?B?NHJIcFR5S090WHZuOXFGUkZWdC84SzdDdDFObTVzRHBsYmFOYlFsVHU5UkVX?= =?utf-8?B?R01iTG5xSTY5cUdTUHJTa21xUzdGVDBQM3lMRFlncG1Bd3NrRzFFRUFkUUZW?= =?utf-8?B?ckdLTjN4YmhXWDd4eDhPYW91RTYrc1owQnhIVDRsRkw0QTBWaGpJY0NSNWZU?= =?utf-8?B?bUhEejBRa0xkazdxTkRYdFhmNGl3RzF4QzMxTTV6b2JKYlV3UFNjQlJZT3I4?= =?utf-8?B?OGw0K3diVmRIOC9mNTAwWC9semlydVdGVXg4U3VWU2Y3VlRqRU8yazhtYXZD?= =?utf-8?B?RUVXTlJJMG0zWXJxYnY4Qnl0UU1yR3F6YmxiQ2JGeVVxVndPYThvdnhXMk5Y?= =?utf-8?B?dXY5SUVERXArZ3BZUy9OUEt1cU9Kb3dNYnNjUjVQUXd4clpFMnkwWVVXdm5t?= =?utf-8?B?bnVGVWttYkdsbWtlc25adStpZXNmQU1KTHJ1U2FNUVBTd1E2V1VPTWZ2aDZE?= =?utf-8?B?ckw1cFozcUJxTGhxdWN0cWF5OTUrYVBWOThOZmFwSmFXeEVVajNFTlJzckxR?= =?utf-8?B?VVE2TUJGOGQxMGVUMXZKK0p5MTM1OUtyY09aR252dHBZaVQwYmphbEh4T28w?= =?utf-8?B?SVVNRFhpaktVZUpWYlJ6aWdKWXBqMkZWZDJoL3NXUlUyWVdhclFlOUY3Mk9V?= =?utf-8?B?cmVQRHFQWFlhRGZWSldvcXJ6eERpK2pVMTFLem9TSDB1Tkl2OE9ydi9uWVlI?= =?utf-8?B?aGJONkFtUzAxdmZhanNNbXFlUE5YVFhuYlY4MzUyc0Z3cDdOMXJTVnlZY2FB?= =?utf-8?B?MzhNZlZNTWZ4bitwY21ROUE3NEZpNVI3NkVvVSsvQ2xYZ3daRzJaNHlEN0xq?= =?utf-8?B?a29helRJSHFNZlB0T2JRVkNKcm5ycXNPbU9rWTBCdFdvSjdqYnllSmJRVmZl?= =?utf-8?B?WlUza2ljUlI3bk9hamY0VVFsb0Jsd053aW8yMHFMQmVrQi80YXV0RkFCb211?= =?utf-8?B?azZJOVpYUHdUVkN1c2liaGFlUVA4UnJiQ0Ezc0RSTGxUM2Q0UjhPNGoxaFBF?= =?utf-8?B?VzFrNWJjWWRIQ3BVMVdBbnE2ODRaYzNMQURFM3BXNU1pdFc5cVNNSFVkUUxS?= =?utf-8?B?aG5MUHUxN1BPa3pMa3dIZGJ4MkNMR3ozTnVTUEFSYXNYRDlpdkVtQ0xKTGJ5?= =?utf-8?B?SEE1VFlKY05GWEgzdGk2dWpJdEdDendDbHhZenBKclVVa1JyVnZvNHpjc0lH?= =?utf-8?B?V2JtclZpT2MwcU9HbmlRb1Avc3F1M0dacFBmOVkvUXZpbEkvK2tHRlJYSXAx?= =?utf-8?B?U1pSWVZHNVBPR1RFK0J4TmYzVHFHdVRMS0NHdzUzUUhpNSt1ZmpVSWw0d0Rp?= =?utf-8?B?bitNZHJTQXBKb1F6VVQwemx5amtURUhzQVQ2b0NWS0Z1UzkvS3c0WFRqT2RE?= =?utf-8?B?dUtlWVBIeGZHWU92TTBGSFZ3R1hnVTZHOEphZk9qTjV6REdNZGpoU1NhUFEx?= =?utf-8?B?ZWhnYWwzQ0FBOHVWd3ptcEk3TVR5MnA5bEdCd0g4UEhLSHhPTGxwZ0ZHdmtu?= =?utf-8?B?Tlc1V01RQmJ3MkVFb1VEMEJKNjY0ei9vTDF2Q0oybDIzVkV1ZXFVQWJPeWQv?= =?utf-8?B?YTluSzZIWC9TMTBNZWxDY2ZHeEMraDlaOUY3MlNnNzBDdEZPT1RjdUlxRVhY?= =?utf-8?B?ditNT09yQUkvRU40UVNYV3VpOFprWnAzNGU1YWQxUkEreXBwTHQvQ2JaeFJq?= =?utf-8?B?U0FFVy9lV3BOa3ZaU215aVB3Tk00Nk9tRW9xQ3pETVVHR21zQS9MWEdHWS84?= =?utf-8?B?VnFud0IyMXpxZXR6TS9kVjUzbm4vNHZ5V2Z3eURUdjgwNnBHSFBZdDV4ZGc3?= =?utf-8?B?VzgwTjdITzhSczRZN1RWc3hVaVd3Yi9lYW5SNm1QeUFRR09CZlpkbU5XcExp?= =?utf-8?B?RFYxT2pxVngwTkZhTGFNalpNWTkwdTVWeDJOK2xsemJ3OHozWUUyUT09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0533687a-d0cc-4f6e-55d5-08de6272cf51 X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Feb 2026 15:50:37.9869 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: kN2BeTL3dC+mnSVEY9YEsUAzv4vsnTYPFOVOHL58GmZDSyJLn0ehdcZI2Af4C8mPuDyaadCQpes0D1PmHpCR+A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR03MB5253 On Wed, Nov 12, 2025 at 04:53:27PM +0100, Jan Beulich wrote: > cpumask_var_t can resolve to a pointer or to an array. While the pointer > typically is allocated once for a CPU and then only read (i.e. wants to be > marked read-mostly), the same isn't necessarily true for the array case. > There things depend on how the variable is actually used. cpu_core_mask > and cpu_sibling_mask (which all architectures have inherited from x86, > which in turn is possibly wrong) are altered only as CPUs are brought up > or down, so may remain uniformly read-mostly. Other (x86-only) instances > want to change, to avoid disturbing adjacent read-mostly data. > > While doing the x86 adjustment, also do one in the opposite direction, > i.e. where there was no read-mostly annotation when it is applicable in > the "pointer" case. > > Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné > --- > Really in the pointer case it would be nice if the allocations could then > also come from "read-mostly" space. Hm, I guess for some of them yes, it would make sense to come from __read_mostly space, but would require passing an extra parameter to the DEFINE_ helper? Or introduce another variant. Thanks, Roger.