linux-kernel - [RFC PATCH 0/2] EFA dmabuf memory regions

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Date:   Thu, 7 Oct 2021 13:42:58 +0300
From:   Gal Pressman <galpress@...zon.com>
To:     Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
CC:     <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        Oded Gabbay <ogabbay@...ana.ai>,
        Tomer Tayar <ttayar@...ana.ai>,
        Yossi Leybovich <sleybo@...zon.com>,
        Alexander Matushevsky <matua@...zon.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Jianxin Xiong <jianxin.xiong@...el.com>,
        Firas Jahjah <firasj@...zon.com>,
        Gal Pressman <galpress@...zon.com>
Subject: [RFC PATCH 0/2] EFA dmabuf memory regions

Hey all,

This is a followup to my previous RFC [1], which now makes use of the
dynamic attachment API implemented in the RDMA subsystem, but calls
dma_buf_pin() in order to make sure that the move_notify callback will
not be used, as suggested by Christian.
As explained in the previous RFC, move_notify requires the RDMA device
to support on-demand-paging (ODP) which is not common on most devices
(only supported by mlx5).

While the dynamic requirement makes sense for certain GPUs, some devices
(such as habanalabs) have device memory that is always "pinned" and do
not need/use the move_notify operation.

The first patch changes the dmabuf documentation to make it clear that
pinning does not necessarily mean the memory must be moved to system
memory, it is up to the exporter to decide.

The motivation of this RFC is to use habanalabs as the dmabuf exporter,
and EFA as the importer to allow for peer2peer access through libibverbs.

[1] https://lore.kernel.org/linux-rdma/20210818074352.29950-1-galpress@amazon.com/

Thanks

Gal Pressman (2):
  dma-buf: Fix pin callback comment
  RDMA/efa: Add support for dmabuf memory regions

 drivers/infiniband/hw/efa/efa.h       |   4 +
 drivers/infiniband/hw/efa/efa_main.c  |   1 +
 drivers/infiniband/hw/efa/efa_verbs.c | 166 +++++++++++++++++++++-----
 include/linux/dma-buf.h               |   4 +-
 4 files changed, 142 insertions(+), 33 deletions(-)

-- 
2.33.0