Re: P2PDMA support status for the sappire rapids+

[Lukas Wunner <lukas@wunner.de>]

On Tue, Apr 08, 2025 at 05:48:16PM +0300, Damir Chanyshev wrote:
> I have a question regarding p2pdma support, I am not an expert in the
> kernel subsystems, please pardon my stupidity.
> While investigating performance opportunities, I stumbled with dma
> between cpu root complex and pcie switch root complex. And found white
> list for the Intel platforms [1]
> 
> Typical topology looks like this rdma nic<>cpu<>pcie switch<>gpu/xpu,
> for each socket.
> Questions:
> List not updated because new hardware doesn't support this feature?
> (For example abandoned for the CXL3+ )
> Or just not tested for the new platforms?

Basically just lack of resources to do proper testing and amend the list
on a regular basis.

Feel free to submit a patch amending the list for newer platforms if
you got p2pdma working on them.

> Pardon my tone, if it sounds harsh, don't mind it, unfortunately
> English is my third language.

That's fine but it would help us if you could clarify whether you're
associated with an OFAC sanctioned entity.  Unfortunately we're now
forced to perform background checks on contributors before interacting
with them:

https://www.linuxfoundation.org/blog/navigating-global-regulations-and-open-source-us-ofac-sanctions

I note that there's a developer with your name based in Serbia.
If that's you, you're probably not associated with a sanctioned entity:

https://rs.linkedin.com/in/damir-chanyshev

However there is another person based in Saint Petersberg and the
situation is less clear in their case:

https://ru.linkedin.com/in/chanyshv
https://github.com/chanyshv

I am very sorry it has come to this.

Thanks,

Lukas