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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C15DDC982FA for ; Wed, 23 Sep 2026 10:31:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A0A7D6B008C; Wed, 23 Sep 2026 06:31:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9BB6C6B0092; Wed, 23 Sep 2026 06:31:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A93D6B0095; Wed, 23 Sep 2026 06:31:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 625B36B008C for ; Wed, 23 Sep 2026 06:31:36 -0400 (EDT) Received: from smtpin22.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id D203A1C345B for ; Wed, 23 Sep 2026 10:31:35 +0000 (UTC) X-FDA: 85244660550.22.616123C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf02.hostedemail.com (Postfix) with ESMTP id 11E1280005 for ; Wed, 23 Sep 2026 10:31:33 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j35rH4u7; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790159494; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=aF1MzpU61XRmUHcDP/fvbQ0mXhibmF/LWQ0namfOZ8U=; b=evHs4s5/wt92HH9nyGSkTAw79XBuTTsmBXV5Zd+Ch87CgH9c/6MgFyCaoeHN6OZmlRjYvK oPFPeY4lgyJr9Wr6JxXuMOiaDBUdZKWoC/dK5HQs1Iy58ou3BvicwASjjua6W5cFBoVT+0 GJ5pJLrKfmi/1nALTdm0QOSNC04A3uo= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j35rH4u7; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790159494; b=FubiFA/xEZGju4v6pYJs0qufMypx4hTqNk07qj4bwNMInVjrODEZG9UCmrsxg7y52n+GcD 2gQcXUwMdf6JD6AlieHE+S3TFnPa8nN0EVXz9zwh4TDmkDMI47WqKi4F+nz+xkWrerTFOR uoMcpA3s6ngTwtkwnSbC+EOOnJEyMGc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 8A912600AA; Wed, 23 Sep 2026 10:31:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8271A1F000FF; Wed, 23 Sep 2026 10:31:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790159493; bh=aF1MzpU61XRmUHcDP/fvbQ0mXhibmF/LWQ0namfOZ8U=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=j35rH4u7WV13DsI7KZ4JrOlt1/NTCQO5zUuJnhXsK3azEtUNgmnX59lKPmMfjDbqL Fwqe8wTPPPEo4297dLRg9aCSd9xpep8/RXoK1N1AHdEpiamQgo7zuQO/WC+8VWA9sy u6XdogA3R/SrEmjk3/ffko7jtDTgCzSBCpRQ9ruCfYu2ycm4tOrU8gqh4q6sD2pvaK RZX2znjko45SxPIZ9lGTG4v+DXBdne6J5DWcUpX/3H254Ur4VgR/UbBlo8nnzwPnl0 Wmh2/efj9MGLgcFXE5euNPTX6V1vm8LLCaCO+xMIJxghSoX6v/6h57QTv/ffZNdzRH +DgjaGBeBMM9Q== Message-ID: Date: Wed, 23 Sep 2026 12:31:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/5] hibernation, KFENCE: explicitly map/unmap KFENCE pages To: "Mike Rapoport (Microsoft)" , Andrew Morton , Alexander Potapenko , Marco Elver , "Rafael J. Wysocki" Cc: Dmitry Vyukov , Len Brown , Pavel Machek , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org References: <20260917-hibernation-v1-0-7f7dfae3dbe0@kernel.org> <20260917-hibernation-v1-4-7f7dfae3dbe0@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260917-hibernation-v1-4-7f7dfae3dbe0@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: grjumt8d3oznxweormdirderheuqhdeu X-Rspamd-Queue-Id: 11E1280005 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790159493-78514 X-HE-Meta: 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 FSX2PVG2 lnfZDzS8gwQ2g55GO2bLgo2KXhBOBQIcQQ2AmRi2A1C6tFGZtXx03fs8DL3fc4s0RCjKWweeQSIKyXrf6WbbzirH38ZH4LCU4lrubos6mfyC59aqTf2RgsbnB2Qp6vh5tvOjV+74QgvWkQLg5vy1X9dqORzFXfTKA95QewKWoyH2j8Z627LQvE4uevSB8vJlhZA7qwGIR2BqrQufglNrMxLNpEGHLdj+B/o02hBpFXrgTtFc6HK7UO1uHZ5hR0M3uYnvelQcUQ1Q4tqCdfPSkVpWTYA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/17/26 08:07, Mike Rapoport (Microsoft) wrote: > The pages protected by KFENCE are removed from the direct map. > > safe_copy_page() temporarily maps and unmaps them using set_direct_map > APIs, or, when the stars align, even using debug_pagealloc_map_pages(). > > Neither of these APIs cares whether it is a KFENCE page and both blindly > perform the update of the kernel page table for any non-present page. Agreed, we should route this through the actual mechanism that modified the directmap in the first place. > > Ability to use debug_pagealloc_map_pages() to remap KFENCE pages when both > KFENCE and debug_pagealloc are enabled is an amusing coincidence. > > But with increasing appetite for using set_direct_map for hardening > purposes, it becomes too big of a hammer to enable saving any non-present > page in the hibernation image. > > Another gotcha is that loongarch that does not have a direct map at all > advertises ARCH_HAS_SET_DIRECT_MAP to allow coexistence of KFENCE and > hibernation. > > Extend KFENCE with a bitmap that tracks which pages are protected and > provide kfence_force_mapping() and kfence_restore_mapping() APIs that allow > forced mapping and unmapping of KFENCE pages. > > Use these APIs in hibernate_{map,unmap}_pages() for KFENCE pages. > > Signed-off-by: Mike Rapoport (Microsoft) > --- > include/linux/kfence.h | 29 +++++++++++++++++++++++++++ > kernel/power/snapshot.c | 7 +++++++ > mm/kfence/core.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++-- > 3 files changed, 86 insertions(+), 2 deletions(-) > > diff --git a/include/linux/kfence.h b/include/linux/kfence.h > index e5822f6e7f279..33a126cb6d1b7 100644 > --- a/include/linux/kfence.h > +++ b/include/linux/kfence.h > @@ -222,6 +222,32 @@ struct kmem_obj_info; > bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab); > #endif > > +/** > + * kfence_force_mapping() - make sure a KFENCE page is mapped > + * @page: page to map > + * > + * Check whether @page is protected and map it if needed. > + * > + * Requires: is_kfence_address(page_address(page)) > + * > + * Return: > + * * false - failed to map @page > + * * true - @page is mapped > + */ > +bool kfence_force_mapping(struct page *page); > + > +/** > + * kfence_restore_mapping() - restore mapping of a KFENCE page The name is misleading. You are actually restoring that the page is unmapped/protected? kfence_force_mapping vs. kfence_restore_mapping is confusing. Can we find a better pair of function names that describe what is actually happening? Maybe something along the lines of kfence_prepare_copy_page kfence_finish_copy_page That rather expresses what the caller intends to do. -- Cheers, David