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 6EAEBC9830E for ; Fri, 25 Sep 2026 10:24:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 680506B0088; Fri, 25 Sep 2026 06:24:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 657D36B008A; Fri, 25 Sep 2026 06:24:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5466E6B0095; Fri, 25 Sep 2026 06:24:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2CBCE6B0088 for ; Fri, 25 Sep 2026 06:24:01 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id A7A7012025F for ; Fri, 25 Sep 2026 10:24:00 +0000 (UTC) X-FDA: 85251899040.26.AE7DAB6 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf08.hostedemail.com (Postfix) with ESMTP id 41CCC160008 for ; Fri, 25 Sep 2026 10:23:58 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=fObPrYxJ; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf08.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790331838; 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=nqSQfDrdpDYW051eAGtg8LkmO5WsRJfyGEnYEAE/NaQ=; b=aSyLIrtDFmNu6pKZCb0t9oPmlbHu9ry3JOeuGYq7eeZNul5u5gNeHc/BFaY11lQPTfgml4 fMgnsuER83SLcnxKv5BSL5cGByO1z8E/gL8G/37n/EpHOIMUe+u+wxMGzoWOovmrdu5C7C XYWH8uQlCNxbRWp6R2ALPrTsDU1lkd8= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=fObPrYxJ; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf08.hostedemail.com: domain of mpenttil@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=mpenttil@redhat.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790331838; b=kzBhftWJL9XOflFcU1xQoWGTjlaZVPhMY/87Wcg4LRnU2m6OlXz/HWE9Qjb4yJrx6sEYjT +JfIJKBed3HYyElwqCDQC6CfgPl24PN0glL5+BLZeZkkv7pxRsFw0fr9Ec5LVjF3nB4Y83 IZHxbvy6XvX7nMLmqZ6i889JktNFiZ0= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1790331837; h=from:from: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; bh=nqSQfDrdpDYW051eAGtg8LkmO5WsRJfyGEnYEAE/NaQ=; b=fObPrYxJ+0WIQLTXTaX/fg0HO5AlpBJJ2bsjD4a1KlQhmqaQn3V11dZDY4od1NiQVnTpZ2 X2zzKP2beBnt/+ei4136WJcV0EC63mzlcEeirKQPUvJAtcAMoI7vjSBN1n31gPNzsY76Pa gbjY0plYyXnUTFHOSGKNN8Or2HvKUII= Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-119-xDxgcQ0MNPmsVH8efpNUAw-1; Fri, 25 Sep 2026 06:23:56 -0400 X-MC-Unique: xDxgcQ0MNPmsVH8efpNUAw-1 X-Mimecast-MFC-AGG-ID: xDxgcQ0MNPmsVH8efpNUAw_1790331835 Received: by mail-lj1-f199.google.com with SMTP id 38308e7fff4ca-3a3546bd99fso3348861fa.2 for ; Fri, 25 Sep 2026 03:23:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790331835; x=1790936635; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=nqSQfDrdpDYW051eAGtg8LkmO5WsRJfyGEnYEAE/NaQ=; b=ZhP/BkG7JzTcensTI2Iyr6cSd+pAXGOnzaKgfxlazaJwmef1JJ4BXguF4r2pXE6qPQ x9kWaXdIvnsSF/y0ojrS0Tdm5pSJ7yw494tsHf/Zb4PxJXfee1eNstjLjbbY25vVZtGA L0K8Aj9DjupR3vkyigChCs8KWPpTnsPzsZOBOn/3Eu9MDcVEy+KZuCnuBRPxKBiYYpW2 +05OXEA2uGTuX39T3dcSu+OOuxdUvqz1Bxf3eHTlM+BPlqcLggwN8507wTKht5dvWiza lKGusWCen2x2ABJzKzERpRhut77N+shSYOuTNY+0qhdCQ6k7tDuInhwYBqvQ/btYjQpN HtkQ== X-Gm-Message-State: AFuF++lN+ty9H7E/JMUdpFkSUGH8YhlaED/UWa6vG3K5QgStigQvxc5S mIW0uigwWVzPI92och3naI/86R9sVoLFGhZO/2UUq20mBKuZGmDi5MChnM82fANIv+MBHRlejA2 8hXkqMUZPkdJrblmCL9BC1lPe+alS7r+R/FkSjRpJHSVCg3AQdR0= X-Gm-Gg: AYBFou0aNPtYHERBTrcCjgUwiw4uWd2ea71NqxtfKp+TTq348XFBKX/95RCOmKJef5B mCqFb1a6DZYvrbLpN4vzW8itvvNa1orHlVm6KtdEIr86hCe7lkofK6tjGmPFhcpUowaR0aJz1t3 AoS7yKcW6UEoQq2UtJ/VNyZgPA1nnT8GjwnU7HSND74gSQRtWQDiCiWXjnwZz1q2EpYNkSFgcP2 RIsJKirM629FqPKdKrBYo6L8kbvMFLPgebVJhu1+o7Q3VJuxVzQGqQ3ZxLYfS9+VZ8/SmkL7e7r qBtEJKEWQmQBKZfXxdOOqMxpopRczXDa+V7fVvSJLG4H7IJhdxFzVXi6mh79EZ1fyKHFGB86GAm iQJ58fYJdbJsaX7xZ+0nehf4FNUWPHbE= X-Received: by 2002:a05:651c:b0a:b0:3a5:dfd3:41b6 with SMTP id 38308e7fff4ca-3a63bdbaf2amr14482561fa.0.1790331835012; Fri, 25 Sep 2026 03:23:55 -0700 (PDT) X-Received: by 2002:a05:651c:b0a:b0:3a5:dfd3:41b6 with SMTP id 38308e7fff4ca-3a63bdbaf2amr14482331fa.0.1790331834509; Fri, 25 Sep 2026 03:23:54 -0700 (PDT) Received: from [192.168.1.86] (89-27-86-246.bb.dnainternet.fi. [89.27.86.246]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-3a64c2ea5d2sm4507651fa.18.2026.09.25.03.23.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Sep 2026 03:23:53 -0700 (PDT) Message-ID: <65c5c412-56a7-46a9-b22b-22077a8e9727@redhat.com> Date: Fri, 25 Sep 2026 13:23:52 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v15 00/11] migrate on fault for device pages To: Christoph Hellwig Cc: linux-mm@kvack.org, dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-kernel@vger.kernel.org, David Hildenbrand , Jason Gunthorpe , Leon Romanovsky , Alistair Popple , Balbir Singh , Zi Yan , Matthew Brost , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko References: <20260924065313.899730-1-mpenttil@redhat.com> From: =?UTF-8?Q?Mika_Penttil=C3=A4?= In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 3kdx1WyL5LYlYFnfEAeyzdulpoy9Sgg038I6nlegihc_1790331835 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: kdq5u5n3tiqorxiebgj8nj7gki1sd5zo X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 41CCC160008 X-HE-Tag: 1790331838-604324 X-HE-Meta: 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 o9hmAv8u SFRYvScu4cJEqVHAznBaSHATw87s1ZEwKJB3qPmZvoU4maM/ag55Yu60uPFtNfTNzmN7i+ZFiR6owJWKxNJGhugXxK2YEZerHc767CZEPBjwBSwmqN0LqfWsMB+ve3H7QlrlsJXs2rJ3SyMqRH94pljazEzZ892wa35XBsHFNcKDGQvAzMd6x0mO69HL9bIPv/8LEewf/oHCOuMVcvF59JnY5wOV/1qtjjNhQDrdZ407/lXGCS4Q434NEtgNMJ7HUj9pMZraWGTg768cmZJwarpjl7AnwMrFm4J5Gdjbn8GGjchZcbhwCpjAKKu1SzpAAACv7QKnEihmJXTE44taY8A74TATFl5ojd+8dKJfCqnAK148dw+HCwbV7i+OYKCSoBaz1LGIekWyMpoZevN9mW9WCoekBTQvEAeDKFwwLyg7MNux5Ll7tlxvy0qrZ8iYb4TvzwBGdorvBwR4HEA4vXFAnHQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/25/26 12:07, Christoph Hellwig wrote: > Who is going to use this? The series seems to lack an actual user for it. Two users: For one, existing migrate_vma_setup() callers, unchanged. The series reworks migrate_vma_setup() to collect via hmm_range_fault() internally (it sets HMM_PFN_REQ_MIGRATE and calls migrate_hmm_range_setup(), mm/migrate_device.c). So every in-tree migrate_vma consumer — nouveau, amdgpu/amdkfd, drm/xe via drm_pagemap, lib/test_hmm — runs on the new path. Second, the point is to fault-in and migrate in a single page-table walk instead of the 2–3 walks drivers do today . It can be driven by hmm_range_fault() directly instead of ping-ponging between hmm fault and migrate_vma interfaces, and lib/test_hmm exercises it. migrate.vma is also populated now for free on fault path. These are aimed at SVM like migrate-on-fault, and is motivated by Alistair Popple's experiments with  current interfaces, where the redundant-walk overhead showed up clearly in perf traces. The unified page table walker also avoids some limitations in current collecting interfaces that can crash when raced with unmap. So this is a building block for migrate-on-fault but delivers immediate in-tree effects by unifying, refactoring and more robust collecting. --Mika