From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Date: Tue, 18 Apr 2017 15:22:58 -0600 Message-ID: <20170418212258.GA26838@obsidianresearch.com> References: <1492381396.25766.43.camel@kernel.crashing.org> <20170418164557.GA7181@obsidianresearch.com> <20170418190138.GH7181@obsidianresearch.com> <20170418210339.GA24257@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Dan Williams Cc: Jens Axboe , "James E.J. Bottomley" , "Martin K. Petersen" , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Benjamin Herrenschmidt , Steve Wise , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Keith Busch , Jerome Glisse , Bjorn Helgaas , linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvdimm , Max Gurtovoy , linux-scsi , Christoph Hellwig List-Id: linux-rdma@vger.kernel.org On Tue, Apr 18, 2017 at 02:11:33PM -0700, Dan Williams wrote: > > I think this opens an even bigger can of worms.. > > No, I don't think it does. You'd only shim when the target page is > backed by a device, not host memory, and you can figure this out by a > is_zone_device_page()-style lookup. The bigger can of worms is how do you meaningfully stack dma_ops. What does the p2p provider do when it detects a p2p page? Jason