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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?H8a118EZulG665EjGKET8lrljgLqGdjROFfrlG14wAQzAZ/cqx63siD3b8uN?= =?us-ascii?Q?yZsor5AJedRB9QOFUmQ9vwNy2k4gC3Ng3nBvdAfaGnvF99DtSq2R5FJa/APg?= =?us-ascii?Q?YbMVb8j2gv4/mZ+NrjJxcvqcOyn31jMZyKMoAhu6nPO+dGndbizDtLHdVOBz?= =?us-ascii?Q?Gdl7wBmCsrcjtSquXa5fZr+tkARlpC8YrlQsSFfQy2qi0Ag09JQv6rvDbALQ?= =?us-ascii?Q?XNVdxIL+JpBsy1EC59l9OnNlwA4hDzZ0P/13WcdbdRDktoG0tmaUzitvY6Ce?= =?us-ascii?Q?1XIIzxsTCeX1wfyGbb3fG25oYf9SVbl2SoRrk1LNLwy/j3eFDz/g+7XSeG96?= =?us-ascii?Q?jPb607C6i8eHdOFVWK+c7ar9ErBS/QFrUF4I0yFnuKBzZSk23MFKVubMSwVb?= =?us-ascii?Q?ArppKr6PvOtQ4k2OtWEJ8zCh/+sDOwg3t1L0PsjrmrQ+LkXatlliyYInrTJM?= =?us-ascii?Q?6ATS6ue1aoJBPaXThU43AhPevWuiDZyhlh9Ds83XpdXGjTkE0Gd/C2XhwS0S?= =?us-ascii?Q?WiYpYA74Wj5lVIMRIjyf3IHYkYHa1vi/bwhTRihOKyT+5+ZpC9Znz4frE/3Z?= =?us-ascii?Q?ROv63INTuEs66AbLWWmvsrdAKWbjAWUBArX0kyGZq/ZiMJ4XeDVd61gt69qi?= =?us-ascii?Q?4noIpMftvgSW7hgQXzKoDuyBM9mxPVlNSnFrgX9MMxLxPllx/ob8bgZyTjHF?= =?us-ascii?Q?xSakHago7geXhJK77xlSnIh/GqCQqnoVHBbVSbGVh/tnZQM/Hg0Sal68IPzp?= =?us-ascii?Q?Mr0rNX/zkhgwnqhazJXARI5PKNyEzdccslllWG03nRriKG1H1N9hJ0v9X0jm?= =?us-ascii?Q?sRIIwRFdQf0S3W1WKM2lLQISe3dt6aUmQ/jebOVWk7Btwh7l3N5jGhSko53K?= =?us-ascii?Q?qvuHa+iE7QA4J1EqceH4rSkt+aJpNVMNYTRmi2ppxhn/r7qMjvmIBQb9GTFs?= =?us-ascii?Q?jJbE4jsBdcE2MG3ruPoitpxg9SB5xmHsPa3yWD5XlAOp8CB+Jj95zhhEpu5+?= =?us-ascii?Q?vqontdw/m72VKsoG6GFqcQ9qW76evLgPQzcN+STZ5hNVwcN7PwwNWLeSHwR2?= =?us-ascii?Q?uMYx1gjHZuv4U7M0t36jBJpkir2qi60+zibDlwoOfelUomEQf8VzmKcQ17re?= =?us-ascii?Q?TlLyAba2PF4VTSUnOetGjkHis6iiA/Uhppt8p9QOUA+jEMebM4aQqm3zKGgq?= =?us-ascii?Q?BT5XrtqybJFqvtxVsAZJhIxpRFYAQSmjdsWwgtxYTEancGDsv4I/RaSt2Ugb?= =?us-ascii?Q?ZAcOevzcctvzsa11PRCH8GWVWTWVz3u8qU8Ft3JpaMSaye+YjMIocxlWTzR5?= =?us-ascii?Q?HZS9XG3HHQSEfHQAfhai/xtmNOWekDRRcFBjwS0JJqxeTluXcejAXcenlpx+?= =?us-ascii?Q?+++07jklvqOyDaZgr9NF7LuKqJ03sabpStPbHjmWa9UOkjK2d3TPoA6lUKgK?= =?us-ascii?Q?0XEPXc4ujm99RNo0FKP0emgjEP4+bOMRIS0EgMrcdStmDCoMsHr84oNS522R?= =?us-ascii?Q?9jHZIyIArcSGHKcsIuSRvvpG5gOCj8tcXVAbvxQrHOcKRb1e78wLw1EaT705?= =?us-ascii?Q?VOahJ8MebC+dt0pyx9o=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: e4178ea1-0505-4e46-715c-08db5f0df2a3 X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 May 2023 23:56:11.5172 (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: xS6d4zE1ctTU9ls1A4G56OD5Q5FC/+vTszLplnASE5VYnWq0UXsoacUZVOF8P1cV X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB6692 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 23, 2023 at 07:20:31PM -0700, John Hubbard wrote: > On 5/23/23 18:47, Alistair Popple wrote: > > The .invalidate_range() callback is called by > > mmu_notifier_invalidate_range() which is often called while holding > > the ptl spin-lock. Therefore any implementations of this callback must > > not sleep. This was originally documented when the call back was added > > in commit 0f0a327fa12c ("mmu_notifier: add the callback for > > mmu_notifier_invalidate_range()") but appears to have been > > Thanks for digging into this. I expect that you're on the right > track, I'm just wondering about something still: > > > inadvertently removed by commit 5ff7091f5a2c ("mm, mmu_notifier: > > annotate mmu notifiers with blockable invalidate callbacks"). > > Was it really inadvertent, though? The initial patch proposed said this: > > "Also remove a bogus comment about invalidate_range() always being called > under the ptl spinlock." [1] Right, it is not always called under PTL spinlocks and the implementation cannot assume it, but that doesn't mean the implementation is allowed to block. That was one of the main motivating reasons to have both the invalidate_start/end and invalidate_range variations, start/end are allowed to block and range is not. invalidate_range really only exists for the iommu drivers to use it for SVA designs, there are a few other weird users, but iommu was the motivation to create it in the first place. So the comment should just clarify that it is not allowed to sleep and can't assume anything about its locking environment. Jason 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 A2E59C77B7C for ; Sat, 27 May 2023 23:56:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Cdz9/W99aC4UarpbLzhsOmSPF4dBxnf+5lQ4fWbc3cI=; b=AId2+Jzot8t/lP jdvDkGq99ShVmab1R8E5VvqI2HMcvNjwPPOUBFyLeax0OUuCGSx5oBDbxVJayZ+lp+bROGZUaj/w4 gWORJBzQ2/pFEvz9EKqdtTOmIplKyzY6FU5ViNhiaFEPIZDghfrBEgsF2xfaHaKAhkPyt47huarZY mq74EhZuI882iDGtOpGQzIY90oYlVkkBUDuX87axKheQ7Zgpusyiu2DpQmaecVDeMD2DyokcE6WyG oI4OVHcnDlHImN/3XAYoHZjGGOihK8evOiyBqBGUkaZwgkJjQe84GE1MM50HTOWdmdgyVouvzYeN6 cq9H3SR8v/T3BibdgHeA==; 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Received: from LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) by SN7PR12MB6692.namprd12.prod.outlook.com (2603:10b6:806:270::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6433.15; Sat, 27 May 2023 23:56:11 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::f7a7:a561:87e9:5fab]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::f7a7:a561:87e9:5fab%6]) with mapi id 15.20.6433.017; Sat, 27 May 2023 23:56:11 +0000 Date: Sat, 27 May 2023 20:56:08 -0300 From: Jason Gunthorpe To: John Hubbard Cc: Alistair Popple , Andrew Morton , will@kernel.org, catalin.marinas@arm.com, David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, robin.murphy@arm.com, nicolinc@nvidia.com, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, zhi.wang.linux@gmail.com, Sean Christopherson Subject: Re: [PATCH 1/2] mmu_notifiers: Restore documentation for .invalidate_range() Message-ID: References: <3cece716fc09724793aa832e755abfc9d70a8bb3.1684892404.git-series.apopple@nvidia.com> Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: BL1PR13CA0145.namprd13.prod.outlook.com (2603:10b6:208:2bb::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_|SN7PR12MB6692:EE_ X-MS-Office365-Filtering-Correlation-Id: e4178ea1-0505-4e46-715c-08db5f0df2a3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 23, 2023 at 07:20:31PM -0700, John Hubbard wrote: > On 5/23/23 18:47, Alistair Popple wrote: > > The .invalidate_range() callback is called by > > mmu_notifier_invalidate_range() which is often called while holding > > the ptl spin-lock. Therefore any implementations of this callback must > > not sleep. This was originally documented when the call back was added > > in commit 0f0a327fa12c ("mmu_notifier: add the callback for > > mmu_notifier_invalidate_range()") but appears to have been > > Thanks for digging into this. I expect that you're on the right > track, I'm just wondering about something still: > > > inadvertently removed by commit 5ff7091f5a2c ("mm, mmu_notifier: > > annotate mmu notifiers with blockable invalidate callbacks"). > > Was it really inadvertent, though? The initial patch proposed said this: > > "Also remove a bogus comment about invalidate_range() always being called > under the ptl spinlock." [1] Right, it is not always called under PTL spinlocks and the implementation cannot assume it, but that doesn't mean the implementation is allowed to block. That was one of the main motivating reasons to have both the invalidate_start/end and invalidate_range variations, start/end are allowed to block and range is not. invalidate_range really only exists for the iommu drivers to use it for SVA designs, there are a few other weird users, but iommu was the motivation to create it in the first place. So the comment should just clarify that it is not allowed to sleep and can't assume anything about its locking environment. Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel