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Mon, 4 Jan 2021 16:38:41 +0000 To: linux-mm@kvack.org, majordomo@kvack.org Cc: Andrew Morton From: Andrey Grodzovsky Subject: Question regarding page fault handlers in kernel mappings Message-ID: Date: Mon, 4 Jan 2021 11:38:38 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [2607:fea8:3edf:49b0:4465:d1cb:357e:d8b0] X-ClientProxiedBy: YT1PR01CA0072.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2d::11) To SN6PR12MB4623.namprd12.prod.outlook.com (2603:10b6:805:e9::17) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2607:fea8:3edf:49b0:4465:d1cb:357e:d8b0] (2607:fea8:3edf:49b0:4465:d1cb:357e:d8b0) by YT1PR01CA0072.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2d::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3721.19 via Frontend Transport; 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One issue I am facing is how to avoid accesses to physical addresses both in RAM and MMIO from user mode and kernel after device is gone. For user accesses (mmap) I use the page fault handler to route all RW accesses to dummy zero page. I would like to do the same for kernel side mappings both form RAM (kmap) and device IO (ioremap) but it looks like there is no same mechanism of page fault handlers for kernel side mappings. Am I correct in my understanding ? Thanks, Andrey