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 3BD14FDEE3F for ; Thu, 23 Apr 2026 19:25:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 631296B0088; Thu, 23 Apr 2026 15:25:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 607E56B008A; Thu, 23 Apr 2026 15:25:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 51E576B008C; Thu, 23 Apr 2026 15:25:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 4212E6B0088 for ; Thu, 23 Apr 2026 15:25:41 -0400 (EDT) Received: from smtpin23.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay03.hostedemail.com (Postfix) with ESMTP id CFDEEA035B for ; Thu, 23 Apr 2026 19:25:40 +0000 (UTC) X-FDA: 84690800040.23.B34C01E Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf04.hostedemail.com (Postfix) with ESMTP id EE16640017 for ; Thu, 23 Apr 2026 19:25:38 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=FVX7LR5V; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776972339; a=rsa-sha256; cv=none; b=yT9JoLA/wCYW1Pvw5jo8b+UVMqKvPJEHLaOaHhkqsBQ0Mo8o6zTmWaWUMOWkfM0iGKRysH vOcUqOv/EWAV0bv7S10bcePlxeBnhPSPo+HgXWo5SWh4wn9hzruXvvwky2D8bAUFRWA6P0 QM5z1Yv80dtE285ObQh9KEEjSR+Gji8= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=FVX7LR5V; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776972339; 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=enbskP1Wr8MSKLZfmzCeLIVxZaEVj7jBjVJ+H2o3mm0=; b=V+4muwjSRonD2Ha5MbzaMUEOWIVE7GjX4qjqhlzEeNofsIvMtMuoEG/nZYRCWWC0/NzIZN L+9xulOwrPGTIHZZdW8Ey781w2SL4C0FVRtvYTsAoZlDGRbpJcFzWN1LvgpYYTemb2Ywdz 3CUC1Y4MtuELTtLoCgYxA+sTtFNAzR0= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id C68AB4347B; Thu, 23 Apr 2026 19:25:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE4E7C2BCAF; Thu, 23 Apr 2026 19:25:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776972337; bh=mEhSNzw438eFSo2SttGbiPSYg2mHMQZBVE1dKmzNCRM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FVX7LR5VfT9r+KDdUIYNaKW4g1qbwcNTMrf1WWtlqrxX2N6+4OFX2vTsYp1PuTRpn mveZ91DqGnBIL7zSKFKil5s5fMsAEY5uHjZ+eXPw5qMGJyxWJbHz6fJXEK0E5czucz O2wxGgqwuGJnt88RUqCa5l4hRyybxiGh0U+sxVJpxmLvatbj0FwdWzl3o2KZYl0OVj JhRVlG9Xr6AMize3o3Bbpikvp+LKEg5E1NQHZykdlqvZ509ULoXZ/H85A5eYVLRt+I r0AOAmna18dl5Es84/sYgSuoBB8GoR7vPYRr7NvfgjlQbhkdk2GNqhrPQQNgY6vTgh ctogcTdfyfZZg== Message-ID: <17b0dc02-eee3-46d6-9afb-5f81a3a20216@kernel.org> Date: Thu, 23 Apr 2026 21:25:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC, PATCH 00/12] userfaultfd: working set tracking for VM guest memory To: Peter Xu , Kiryl Shutsemau Cc: Andrew Morton , Lorenzo Stoakes , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , "Liam R . Howlett" , Zi Yan , Jonathan Corbet , Shuah Khan , Sean Christopherson , Paolo Bonzini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org References: <4c635703-3d8d-4cfa-bb98-7f6f5fcbe547@kernel.org> <34f75083-29a3-4860-8a6e-94551d37ac6a@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: EE16640017 X-Rspamd-Server: rspam12 X-Stat-Signature: bomud8jt39xy7o13sz6yuwk5ag1urja8 X-Rspam-User: X-HE-Tag: 1776972338-60800 X-HE-Meta: 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 3CfZWNiZ tPsGTBL2RBeO7sc2FgRVAVhYFxI0zKt369+0QsieOzSVYQCbk94QHIzN3B4n8BAAU0JOPI9Vo0THP/iAuiDyCybT00qul2Ecgj3kMeEAlz6ideLAxfZ8w0t/3u6Bg/ed2qlMJtNBtfT/+qsOSv/1dv1+cxVHFH0nD3DTED+A6u1Hr8WAAjqHn+CPtYx8QRCfpUZvtzXM/hsrZeNwMvwqtRTLsSTL8n/ZpqsNmdmTt8TOLS8eVni/VtAEAR91HuCevxP2GIZws3zA/1CRlPsSgnrwvMk06Z0m8DZtl Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > The other thing is, as I mentioned in the other email, I still don't know > how the current RW protection would work for anonymous. I don't yet think > the user swapper can read the anon page with RW-protected pgtables. So far > my understanding is maybe you only care about shmem so it's fine, but it'll > always be great to confirm with you. I wonder if uffdio_move could be used for a swapper implementation instead? If we ever have to read from a protnone page, maybe we could teach ptrace access to do it, or have something that can read from prot_none areas -- like uffdio_copy, which can write to prot-none areas. -- Cheers, David