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[24.227.213.164]) by smtp.gmail.com with ESMTPSA id 127sm312690oid.36.2018.12.12.19.26.37 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 12 Dec 2018 19:26:38 -0800 (PST) Received: from jgg by jggl.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gXHe1-0000rp-2w; Wed, 12 Dec 2018 20:26:37 -0700 Date: Wed, 12 Dec 2018 20:26:37 -0700 From: Jason Gunthorpe To: Jerome Glisse Cc: Dan Williams , Jan Kara , John Hubbard , Matthew Wilcox , John Hubbard , Andrew Morton , Linux MM , tom@talpey.com, Al Viro , benve@cisco.com, Christoph Hellwig , Christopher Lameter , "Dalessandro, Dennis" , Doug Ledford , Michal Hocko , Mike Marciniszyn , rcampbell@nvidia.com, Linux Kernel Mailing List , linux-fsdevel , "Weiny, Ira" Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions Message-ID: <20181213032637.GB3204@ziepe.ca> References: <20181210102846.GC29289@quack2.suse.cz> <20181212150319.GA3432@redhat.com> <20181212213005.GE5037@redhat.com> <20181212215348.GF5037@redhat.com> <20181212233703.GB2947@ziepe.ca> <20181213000109.GK5037@redhat.com> <20181213004437.GL5037@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181213004437.GL5037@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 12, 2018 at 07:44:37PM -0500, Jerome Glisse wrote: > On many GPUs you can do that, it is hardware dependant and you have > steps to take but it is something you can do (and GPU can do > continuous DMA traffic have they have threads running that can > do continuous memory access). So i assume that other hardware > can do it too. RDMA has no generic way to modify a MR and then guarntee the HW sees the modifications. Some HW can do this (ie the same HW that can do ODP, because ODP needs this capability), other HW is an unknown as this has never been asked for as a driver API. Jason