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Date: Tue, 18 Apr 2017 15:22:58 -0600
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Logan Gunthorpe <logang@deltatee.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Bjorn Helgaas <helgaas@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Sagi Grimberg <sagi@grimberg.me>,
	"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
	Steve Wise <swise@opengridcomputing.com>,
	Stephen Bates <sbates@raithlin.com>,
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	linux-nvdimm <linux-nvdimm@ml01.01.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Jerome Glisse <jglisse@redhat.com>
Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory
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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