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[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 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 In-Reply-To: <2217153.lfGrokb94b@nvdebian> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rcampbell@nvidia.com, willy@infradead.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, bsingharora@gmail.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, hch@infradead.org, linux-mm@kvack.org, jglisse@redhat.com, bskeggs@redhat.com, jgg@nvidia.com, jhubbard@nvidia.com, akpm@linux-foundation.org, Christoph Hellwig Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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