linux-kernel - Re: Enabling peer to peer device transactions for PCIe devices

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Date:   Mon, 28 Nov 2016 14:36:49 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Serguei Sagalovitch <serguei.sagalovitch@....com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Haggai Eran <haggaie@...lanox.com>
Cc:     Christian König <christian.koenig@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...1.01.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "Kuehling, Felix" <Felix.Kuehling@....com>,
        "Bridgman, John" <John.Bridgman@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Sander, Ben" <ben.sander@....com>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        "Blinzer, Paul" <Paul.Blinzer@....com>,
        "Linux-media@...r.kernel.org" <Linux-media@...r.kernel.org>,
        Max Gurtovoy <maxg@...lanox.com>
Subject: Re: Enabling peer to peer device transactions for PCIe devices


On 28/11/16 12:35 PM, Serguei Sagalovitch wrote:
> As soon as PeerDirect mapping is called then GPU must not "move" the
> such memory.  It is by PeerDirect design. It is similar how it is works
> with system memory and RDMA MR: when "get_user_pages" is called then the
> memory is pinned.

We haven't touch this in a long time and perhaps it changed, but there
definitely was a call back in the PeerDirect API to allow the GPU to
invalidate the mapping. That's what we don't want.

Logan