From: Gal Pressman <galpress@amazon.com>
To: "Christian König" <christian.koenig@amd.com>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Doug Ledford" <dledford@redhat.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>
Cc: <linux-media@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
<linux-kernel@vger.kernel.org>, <linux-rdma@vger.kernel.org>,
Oded Gabbay <ogabbay@habana.ai>, Tomer Tayar <ttayar@habana.ai>,
Yossi Leybovich <sleybo@amazon.com>,
Alexander Matushevsky <matua@amazon.com>,
Leon Romanovsky <leonro@nvidia.com>,
Jianxin Xiong <jianxin.xiong@intel.com>
Subject: Re: [RFC] Make use of non-dynamic dmabuf in RDMA
Date: Wed, 18 Aug 2021 11:37:31 +0300 [thread overview]
Message-ID: <01573693-cf7a-a160-2f60-5049dfba1ecd@amazon.com> (raw)
In-Reply-To: <3abaef49-2733-8b5e-3eaa-662a2a57b96e@amd.com>
On 18/08/2021 11:00, Christian König wrote:
> Am 18.08.21 um 09:43 schrieb Gal Pressman:
>> Hey all,
>>
>> Currently, the RDMA subsystem can only work with dynamic dmabuf
>> attachments, which 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 motivation of this RFC is to use habanalabs as the dmabuf exporter,
>> and EFA as the importer to allow for peer2peer access through libibverbs.
>>
>> This draft patch changes the dmabuf driver to differentiate between
>> static/dynamic attachments by looking at the move_notify op instead of
>> the importer_ops struct, and allowing the peer2peer flag to be enabled
>> in case of a static exporter.
>
> Well NAK to the general approach, this can be solved much easier.
>
> If you can't support dynamic moves while using the buffer then just pin all
> buffers during import/export.
>
> This avoids the move notification and the framework/exporter can still correctly
> account for pinned buffers.
>
> But please note that at least amdgpu never uses P2P support for pinned buffers
> since we want to avoid that unmoveable buffers clutter video memory and create
> conflicts with V4L and scanout.
>
> If you don't have such concerns in habanalabs then you can implement the pinning
> there while keeping P2P still enabled.
Thanks Christian!
Are you suggesting to pass an empty move_notify callback instead of passing NULL?
Also, doesn't the pin operation move the memory from the device to host memory?
next prev parent reply other threads:[~2021-08-18 8:38 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 7:43 [RFC] Make use of non-dynamic dmabuf in RDMA Gal Pressman
2021-08-18 8:00 ` Christian König
2021-08-18 8:37 ` Gal Pressman [this message]
2021-08-18 9:34 ` Daniel Vetter
2021-08-19 23:06 ` Jason Gunthorpe
2021-08-20 7:25 ` Daniel Vetter
2021-08-20 12:33 ` Jason Gunthorpe
2021-08-20 12:58 ` Gal Pressman
2021-08-20 14:32 ` Jason Gunthorpe
2021-08-21 9:16 ` Gal Pressman
2021-08-23 10:43 ` Christian König
2021-08-24 9:06 ` Gal Pressman
2021-08-24 9:32 ` Christian König
2021-08-24 17:27 ` John Hubbard
2021-08-24 17:32 ` Jason Gunthorpe
2021-08-24 17:35 ` John Hubbard
2021-08-24 19:15 ` Dave Airlie
2021-08-24 19:30 ` Jason Gunthorpe
2021-08-24 19:43 ` Alex Deucher
2021-08-24 20:00 ` Xiong, Jianxin
2021-08-25 6:17 ` Christian König
2021-08-25 6:47 ` John Hubbard
2021-08-25 12:18 ` Jason Gunthorpe
2021-08-25 12:27 ` Christian König
2021-08-25 12:38 ` Jason Gunthorpe
2021-08-25 13:51 ` Christian König
2021-08-25 14:47 ` Jason Gunthorpe
2021-08-25 15:14 ` Christian König
2021-08-25 15:49 ` Jason Gunthorpe
2021-08-25 16:02 ` Oded Gabbay
2021-09-01 11:20 ` Gal Pressman
2021-09-01 11:24 ` Christian König
2021-09-02 6:56 ` Gal Pressman
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