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,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 7D0B4C433B4 for ; Wed, 19 May 2021 12:21:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 576186135B for ; Wed, 19 May 2021 12:21:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349957AbhESMWg (ORCPT ); Wed, 19 May 2021 08:22:36 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33131 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347770AbhESMWb (ORCPT ); Wed, 19 May 2021 08:22:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621426871; 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: in-reply-to:in-reply-to:references:references; bh=iT4YtjBsBt0s/M51Kj84dkt6amzmmMXBn/lNki8qQn0=; b=ZefcU8PzDyCvDFwxwj6QzsO4ystN8p7Rbz1oSSuV7uas2fzqrp6WVZfgPW6Ir854umfZhy paqU0opFyPlOAVELm69pkVbh9sT8IY092TTvnukKVUIBQ442mscH2qYAOZCeLTg7inZ3L/ c85b4iFwLo7kN8EVMmBRrZVafAv+InU= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-161-l3ulf3dKPz2S-nmiunzhHQ-1; Wed, 19 May 2021 08:21:10 -0400 X-MC-Unique: l3ulf3dKPz2S-nmiunzhHQ-1 Received: by mail-qv1-f70.google.com with SMTP id l19-20020a0ce0930000b02901efdf1c21ecso7389165qvk.10 for ; Wed, 19 May 2021 05:21:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=iT4YtjBsBt0s/M51Kj84dkt6amzmmMXBn/lNki8qQn0=; b=Rd2/qS70sG4WCjqRW4UNauG3niu5g6IrUtExKnNCIDE2xgTd8aFgbc37sur2g6TLYs pBExaEp7s73i3oIkHhHsw15mxB2FP5OXl1yk7avkJldynydUk1sh97YCJrWouXJkRstH 4CKcw8w80ga/zy4hUEwTYFD3mkxQ2f/n2JCLrJ63ihZZ5jh8inxu9KNzPp5ZX+NdGKRn g6cL4xW1RmfvXj41NnAHWDIjc8zf2v3CiZeWibzPBkq0GbkRkeWbWcyObpC2BjQZORKP szgvJ9uphF6XEQ0Ey/Z0L2gT5MOPE5Ubgmsssc/qo5VFTW33rtuORSGBXBO2QqQnCXSU k+GA== X-Gm-Message-State: AOAM531sbInb7Xa3ysGhGypp57LL6SSIPxg5L9sOuSGVW+ryufC4yZkJ lM3qy28Nr8t/d4RvcZ3Zt+aWHhwKW0yoFaFz42BM6TJppV7UcfwxbGMIJ9r+Udnlp9k9nKUqsfl 3/bTv5CWK/mz/toDOgzNiqSrj X-Received: by 2002:a05:620a:818:: with SMTP id s24mr7432103qks.425.1621426869766; Wed, 19 May 2021 05:21:09 -0700 (PDT) X-Google-Smtp-Source: ABdhPJym25A+8CZrSnha27nfGC/bkh618yND6m6b6Lo8EgcNF6Oma7UyN8ZK+yut+/9S1ILrFjJgwA== X-Received: by 2002:a05:620a:818:: with SMTP id s24mr7432081qks.425.1621426869529; Wed, 19 May 2021 05:21:09 -0700 (PDT) Received: from t490s (bras-base-toroon474qw-grc-72-184-145-4-219.dsl.bell.ca. [184.145.4.219]) by smtp.gmail.com with ESMTPSA id o10sm15018668qki.72.2021.05.19.05.21.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 May 2021 05:21:09 -0700 (PDT) Date: Wed, 19 May 2021 08:21:08 -0400 From: Peter Xu To: Alistair Popple Cc: 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, jgg@nvidia.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: References: <20210407084238.20443-1-apopple@nvidia.com> <47694715.suB6H4Uo8R@nvdebian> <2217153.lfGrokb94b@nvdebian> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2217153.lfGrokb94b@nvdebian> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 19, 2021 at 09:35:10PM +1000, Alistair Popple wrote: > I think the approach you are describing is similar to what > migrate_vma_collect()/migrate_vma_unamp() does now and I think it could be > made to work. I ended up going with the GUP+unmap approach in part because > Christoph suggested it but primarily because it required less code especially > given we needed to call something to fault the page in/break COW anyway (or > extend what was there to call handle_mm_fault(), etc.). I see, thank. Would you mind add a short paragraph in the commit message talking about these two solutions and why we choose the GUP way? -- Peter Xu