Re: [PATCH for-next] RDMA/efa: Add CQ with external memory support

["Margolin, Michael" <mrgolin@amazon.com>]

On 5/20/2025 12:16 PM, Leon Romanovsky wrote:
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> On Sun, May 18, 2025 at 11:56:56AM +0300, Margolin, Michael wrote:
>> On 5/18/2025 9:42 AM, Leon Romanovsky wrote:
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>>> On Thu, May 15, 2025 at 02:50:40PM +0000, Michael Margolin wrote:
>>>> Add an option to create CQ using external memory instead of allocating
>>>> in the driver. The memory can be passed from userspace by dmabuf fd and
>>>> an offset.
>>> EFA is unique here. This patch is missing description of why it is
>>> needed, and why existing solutions if any exist, can't be used.
>>>
>>> Thanks
>> I probably should have explained more, the purpose is creating CQs that
>> reside in GPU HBM enabling low latency polling directly by the GPU. EFA
>> isn't unique in receiving pre-allocated memory from userspace, the extension
>> here is the use of dmabuf for that purpose as a general mechanism that
>> allows using memory independent of its source. I will add more info in the
>> commit message.
> I think that this functionality is worth to have as general verb and not DV.
> mlx5 has something similar and now EFA needs it too.
>
> Let's wait for Jason's response before rushing to implement it.
>
> Thanks

Jason, any thoughts on this?

We can probably add optional attributes to create CQ command, but most 
of the handling will remain vendor specific. I'm not convinced it's 
beneficial enough.

Michael