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

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Date:   Mon, 28 Nov 2016 16:55:23 -0500
From:   Serguei Sagalovitch <serguei.sagalovitch@....com>
To:     Logan Gunthorpe <logang@...tatee.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 2016-11-28 04:36 PM, Logan Gunthorpe wrote:
> 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.
I assume that you are talking about "invalidate_peer_memory()' callback?
I was told that it is the "last resort" because HCA (and driver) is not
able to handle  it in the safe manner so it is basically "abort" 
everything.