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[142.68.57.212]) by smtp.gmail.com with ESMTPSA id l4sm297388qkc.26.2020.03.16.11.17.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 16 Mar 2020 11:17:08 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jDuIV-0005TT-IP; Mon, 16 Mar 2020 15:17:07 -0300 Date: Mon, 16 Mar 2020 15:17:07 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Dan Williams , Bharata B Rao , Christian =?utf-8?B?S8O2bmln?= , Ben Skeggs , Jerome Glisse , kvm-ppc@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org Subject: Re: [PATCH 1/2] mm: handle multiple owners of device private pages in migrate_vma Message-ID: <20200316181707.GJ20941@ziepe.ca> References: <20200316175259.908713-1-hch@lst.de> <20200316175259.908713-2-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200316175259.908713-2-hch@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Mar 16, 2020 at 06:52:58PM +0100, Christoph Hellwig wrote: > Add a new opaque owner field to struct dev_pagemap, which will allow > the hmm and migrate_vma code to identify who owns ZONE_DEVICE memory, > and refuse to work on mappings not owned by the calling entity. Using a pointer seems like a good solution to me. Is this a bug fix? What is the downside for migrate on pages it doesn't work? I'm not up to speed on migrate.. Jason