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Wed, 19 May 2021 13:28:44 +0000 Received: from DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::ddb4:2cbb:4589:f039]) by DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::ddb4:2cbb:4589:f039%4]) with mapi id 15.20.4129.033; Wed, 19 May 2021 13:28:44 +0000 Date: Wed, 19 May 2021 10:28:42 -0300 From: Jason Gunthorpe To: Peter Xu Cc: Alistair Popple , linux-mm@kvack.org, nouveau@lists.freedesktop.org, bskeggs@redhat.com, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com, hch@infradead.org, daniel@ffwll.ch, willy@infradead.org, bsingharora@gmail.com, Christoph Hellwig Subject: Re: [PATCH v8 5/8] mm: Device exclusive memory access Message-ID: <20210519132842.GJ1002214@nvidia.com> References: <20210407084238.20443-6-apopple@nvidia.com> <47694715.suB6H4Uo8R@nvdebian> <20210518173334.GE1002214@nvidia.com> <20210518194509.GF1002214@nvidia.com> <20210518230327.GG1002214@nvidia.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?ShX1+RtbSmyhnUT/Thz17PmmI5w2jnNyQ5gokaWj/tfM5uehd+vuKS5yDsSG?= =?us-ascii?Q?OiIj0j/oj0ojbSylpCyNWUcqDI5fAr9F3XxcVPD3pa9fXDlierKy5AwnDeUA?= =?us-ascii?Q?oRXtzqy+xRnAQplEBsm08yMmm9zAW7n3l6nDUsqeb4ongYaKN+O/6yPcrKvs?= =?us-ascii?Q?iDsTQjW9BnvpmiRBX5NPZLfrc/VWMOyXRQEMb8T/Mpw/+gdb1ECYOfl3dYw3?= =?us-ascii?Q?r7oSQzEmWSo/Zw4WszUaC0PaHFFhII/MZ9/FIeBwnanUfcec4pYDr60DpGHY?= =?us-ascii?Q?byVj5cbWKJpaXi1U5/rqP54Q7yQB9jyTC/1BTUOHFP1I2l4zoLP/dTuQk/pb?= =?us-ascii?Q?RBOEUiyEbin8Q6TsYR12lmclD2s6bhanj8UCXMsI9Ov+ZkYJDV+iNg30kQ9a?= =?us-ascii?Q?2MEl86RtH9jgWtcdhhuHA0TRUl7382Cn/XpYnMuvNRBW+vwBoriJRkmCjuQK?= =?us-ascii?Q?bNn2kgkG2WWTq94o/9bN8i2PiRjnbVKlGo+J5yEKEMXK8tYC8girSvCGWt3k?= =?us-ascii?Q?sf9qKSkigbj3ENnKJBKOK92tAOVB+8T/qeXSt2h1wycHLR3HvSj1KuHsKsN9?= =?us-ascii?Q?d+WC/hcs3udO85yaBOAHWYx5TfV7EDGXgFzoS9OVg2v98XpBks0s1C5uXMzC?= =?us-ascii?Q?amt0zVEgYpIBzczbo7Y5SCMhTQJsuJuaTIHqvV4eo4CTVOFCRidtKM4OvCJl?= =?us-ascii?Q?jweTSibwdypfdCHndNfYOcxt6oKQhaN/t96i3viFKgoUdx1YpyQITvWXfHhu?= =?us-ascii?Q?cR8NKpTxOHUhUUooZ1i0Q6Ck6QoG/AlWHW7HniJbrGBcn7aLB7updiTZi5UY?= =?us-ascii?Q?W+TKXwSSYJfw6ZGr6CfNs841K9Q90NHfXbuWVRGMc8em2AJhOUoM8e9txvQy?= =?us-ascii?Q?9kaaFf8RMgRO54XDt495wfPFxxfBFmuRzB8m1vRC4aVEoBJ3PLFp7nGWbMTQ?= =?us-ascii?Q?nn9VrW1p5TyIhepNPEvm8XCM2YR6vC4KaQIyEHVZpALufAGCJxROb8ddx+QO?= =?us-ascii?Q?yRe5g7oH2unlzWSxf0IlzsV/EveXs9/PbMkssfNhkLPuUie+qfiwMswKaFCy?= =?us-ascii?Q?CBXiQJqKIVuRYp6l5Mj3OImdldGAfpZ5X6/umTyj2EanB6S0fJLCxY1Mb17y?= =?us-ascii?Q?fVbyyCD0CGA8UBL4tbbY6bgf9DLW2PvF4veB7i8jPCU7Vs2NoQZKLNMWroYd?= =?us-ascii?Q?gogrgGz0wX4NlrLR2nGfpgoAeflfY9sMk5imzVK7Po4nsIcal26Z2tDD+VC2?= =?us-ascii?Q?GHV60/mAiei38bt24d8WH/Ml4umTm3v0CYW3MyXMnKfsUK4JHyRasPDd621N?= =?us-ascii?Q?Cl20lHabUfv/w05A06HZd//H?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 51402c4a-818c-42d9-7ebc-08d91aca0614 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3834.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2021 13:28:43.9397 (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: BWUJnu65MOFz8vJg7aBCytyzxzKCp7KP1onUZ+J9OPS9POvPEpZ0CsErjHlafNVQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4009 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 18, 2021 at 07:45:05PM -0400, Peter Xu wrote: > On Tue, May 18, 2021 at 08:03:27PM -0300, Jason Gunthorpe wrote: > > Logically during fork all these device exclusive pages should be > > reverted back to their CPU pages, write protected and the CPU page PTE > > copied to the fork. > > > > We should not copy the device exclusive page PTE to the fork. I think > > I pointed to this on an earlier rev.. > > Agreed. Though please see the question I posted in the other thread: now I am > not very sure whether we'll be able to mark a page as device exclusive if that > page has mapcount>1. IMHO it is similar to write protect done by filesystems on shared mappings - all VMAs with a copy of the CPU page have to get switched to the device exclusive PTE. This is why the rmap stuff is involved in the migration helpers 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 X-Spam-Level: X-Spam-Status: No, score=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 515FEC43461 for ; Wed, 19 May 2021 13:28:50 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1AE6460E08 for ; Wed, 19 May 2021 13:28:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1AE6460E08 Authentication-Results: mail.kernel.org; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: nouveau-bounces@lists.freedesktop.org Sender: "Nouveau" On Tue, May 18, 2021 at 07:45:05PM -0400, Peter Xu wrote: > On Tue, May 18, 2021 at 08:03:27PM -0300, Jason Gunthorpe wrote: > > Logically during fork all these device exclusive pages should be > > reverted back to their CPU pages, write protected and the CPU page PTE > > copied to the fork. > > > > We should not copy the device exclusive page PTE to the fork. I think > > I pointed to this on an earlier rev.. > > Agreed. Though please see the question I posted in the other thread: now I am > not very sure whether we'll be able to mark a page as device exclusive if that > page has mapcount>1. IMHO it is similar to write protect done by filesystems on shared mappings - all VMAs with a copy of the CPU page have to get switched to the device exclusive PTE. This is why the rmap stuff is involved in the migration helpers Jason _______________________________________________ Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau 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 X-Spam-Level: X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1A99C433B4 for ; Wed, 19 May 2021 13:28:48 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 974FE613BB for ; 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DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?ShX1+RtbSmyhnUT/Thz17PmmI5w2jnNyQ5gokaWj/tfM5uehd+vuKS5yDsSG?= =?us-ascii?Q?OiIj0j/oj0ojbSylpCyNWUcqDI5fAr9F3XxcVPD3pa9fXDlierKy5AwnDeUA?= =?us-ascii?Q?oRXtzqy+xRnAQplEBsm08yMmm9zAW7n3l6nDUsqeb4ongYaKN+O/6yPcrKvs?= =?us-ascii?Q?iDsTQjW9BnvpmiRBX5NPZLfrc/VWMOyXRQEMb8T/Mpw/+gdb1ECYOfl3dYw3?= =?us-ascii?Q?r7oSQzEmWSo/Zw4WszUaC0PaHFFhII/MZ9/FIeBwnanUfcec4pYDr60DpGHY?= =?us-ascii?Q?byVj5cbWKJpaXi1U5/rqP54Q7yQB9jyTC/1BTUOHFP1I2l4zoLP/dTuQk/pb?= =?us-ascii?Q?RBOEUiyEbin8Q6TsYR12lmclD2s6bhanj8UCXMsI9Ov+ZkYJDV+iNg30kQ9a?= =?us-ascii?Q?2MEl86RtH9jgWtcdhhuHA0TRUl7382Cn/XpYnMuvNRBW+vwBoriJRkmCjuQK?= =?us-ascii?Q?bNn2kgkG2WWTq94o/9bN8i2PiRjnbVKlGo+J5yEKEMXK8tYC8girSvCGWt3k?= =?us-ascii?Q?sf9qKSkigbj3ENnKJBKOK92tAOVB+8T/qeXSt2h1wycHLR3HvSj1KuHsKsN9?= =?us-ascii?Q?d+WC/hcs3udO85yaBOAHWYx5TfV7EDGXgFzoS9OVg2v98XpBks0s1C5uXMzC?= =?us-ascii?Q?amt0zVEgYpIBzczbo7Y5SCMhTQJsuJuaTIHqvV4eo4CTVOFCRidtKM4OvCJl?= =?us-ascii?Q?jweTSibwdypfdCHndNfYOcxt6oKQhaN/t96i3viFKgoUdx1YpyQITvWXfHhu?= =?us-ascii?Q?cR8NKpTxOHUhUUooZ1i0Q6Ck6QoG/AlWHW7HniJbrGBcn7aLB7updiTZi5UY?= =?us-ascii?Q?W+TKXwSSYJfw6ZGr6CfNs841K9Q90NHfXbuWVRGMc8em2AJhOUoM8e9txvQy?= =?us-ascii?Q?9kaaFf8RMgRO54XDt495wfPFxxfBFmuRzB8m1vRC4aVEoBJ3PLFp7nGWbMTQ?= =?us-ascii?Q?nn9VrW1p5TyIhepNPEvm8XCM2YR6vC4KaQIyEHVZpALufAGCJxROb8ddx+QO?= =?us-ascii?Q?yRe5g7oH2unlzWSxf0IlzsV/EveXs9/PbMkssfNhkLPuUie+qfiwMswKaFCy?= =?us-ascii?Q?CBXiQJqKIVuRYp6l5Mj3OImdldGAfpZ5X6/umTyj2EanB6S0fJLCxY1Mb17y?= =?us-ascii?Q?fVbyyCD0CGA8UBL4tbbY6bgf9DLW2PvF4veB7i8jPCU7Vs2NoQZKLNMWroYd?= =?us-ascii?Q?gogrgGz0wX4NlrLR2nGfpgoAeflfY9sMk5imzVK7Po4nsIcal26Z2tDD+VC2?= =?us-ascii?Q?GHV60/mAiei38bt24d8WH/Ml4umTm3v0CYW3MyXMnKfsUK4JHyRasPDd621N?= =?us-ascii?Q?Cl20lHabUfv/w05A06HZd//H?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 51402c4a-818c-42d9-7ebc-08d91aca0614 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3834.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2021 13:28:43.9397 (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: BWUJnu65MOFz8vJg7aBCytyzxzKCp7KP1onUZ+J9OPS9POvPEpZ0CsErjHlafNVQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4009 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rcampbell@nvidia.com, willy@infradead.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, bsingharora@gmail.com, Alistair Popple , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, hch@infradead.org, linux-mm@kvack.org, jglisse@redhat.com, bskeggs@redhat.com, jhubbard@nvidia.com, akpm@linux-foundation.org, Christoph Hellwig Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, May 18, 2021 at 07:45:05PM -0400, Peter Xu wrote: > On Tue, May 18, 2021 at 08:03:27PM -0300, Jason Gunthorpe wrote: > > Logically during fork all these device exclusive pages should be > > reverted back to their CPU pages, write protected and the CPU page PTE > > copied to the fork. > > > > We should not copy the device exclusive page PTE to the fork. I think > > I pointed to this on an earlier rev.. > > Agreed. Though please see the question I posted in the other thread: now I am > not very sure whether we'll be able to mark a page as device exclusive if that > page has mapcount>1. IMHO it is similar to write protect done by filesystems on shared mappings - all VMAs with a copy of the CPU page have to get switched to the device exclusive PTE. This is why the rmap stuff is involved in the migration helpers Jason