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

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Message-ID: <5f5b7989-84f5-737e-47c8-831f752d6280@deltatee.com>
Date:   Wed, 30 Nov 2016 11:01:09 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Haggai Eran <haggaie@...lanox.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-nvdimm@...1.01.org" <linux-nvdimm@...1.01.org>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "Suravee.Suthikulpanit@....com" <Suravee.Suthikulpanit@....com>,
        "John.Bridgman@....com" <John.Bridgman@....com>,
        "Alexander.Deucher@....com" <Alexander.Deucher@....com>,
        "Linux-media@...r.kernel.org" <Linux-media@...r.kernel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Max Gurtovoy <maxg@...lanox.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "serguei.sagalovitch@....com" <serguei.sagalovitch@....com>,
        "Paul.Blinzer@....com" <Paul.Blinzer@....com>,
        "Felix.Kuehling@....com" <Felix.Kuehling@....com>,
        "ben.sander@....com" <ben.sander@....com>
Subject: Re: Enabling peer to peer device transactions for PCIe devices



On 30/11/16 09:23 AM, Jason Gunthorpe wrote:
>> Two cases I can think of are RDMA access to an NVMe device's controller
>> memory buffer,
> 
> I'm not sure on the use model there..

The NVMe fabrics stuff could probably make use of this. It's an
in-kernel system to allow remote access to an NVMe device over RDMA. So
they ought to be able to optimize their transfers by DMAing directly to
the NVMe's CMB -- no userspace interface would be required but there
would need some kernel infrastructure.

Logan