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[213.95.11.211]) by mx.google.com with ESMTPS id p1si1459449wra.274.2019.01.30.09.26.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Jan 2019 09:26:54 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id A292768CEC; Wed, 30 Jan 2019 18:26:53 +0100 (CET) Date: Wed, 30 Jan 2019 18:26:53 +0100 From: Christoph Hellwig To: Jerome Glisse Cc: "Koenig, Christian" , Christoph Hellwig , Jason Gunthorpe , Logan Gunthorpe , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman , "Rafael J . Wysocki" , Bjorn Helgaas , "Kuehling, Felix" , "linux-pci@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Marek Szyprowski , Robin Murphy , Joerg Roedel , "iommu@lists.linux-foundation.org" Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma Message-ID: <20190130172653.GA6707@lst.de> References: <20190129174728.6430-1-jglisse@redhat.com> <20190129174728.6430-4-jglisse@redhat.com> <20190129191120.GE3176@redhat.com> <20190129193250.GK10108@mellanox.com> <99c228c6-ef96-7594-cb43-78931966c75d@deltatee.com> <20190129205827.GM10108@mellanox.com> <20190130080208.GC29665@lst.de> <4e0637ba-0d7c-66a5-d3de-bc1e7dc7c0ef@amd.com> <20190130155543.GC3177@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190130155543.GC3177@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Wed, Jan 30, 2019 at 10:55:43AM -0500, Jerome Glisse wrote: > Even outside GPU driver, device driver like RDMA just want to share their > doorbell to other device and they do not want to see those doorbell page > use in direct I/O or anything similar AFAICT. At least Mellanox HCA support and inline data feature where you can copy data directly into the BAR. For something like a usrspace NVMe target it might be very useful to do direct I/O straight into the BAR for that.