RE: XDP multi-buffer and AF_XDP

> -----Original Message-----
> From: Jesper Dangaard Brouer <[email protected]>
> Sent: Friday, April 1, 2022 3:13 PM
> To: Toke Høiland-Jørgensen <[email protected]>; Kal Cutter Conley
> <[email protected]>; Xdp <[email protected]>
> Cc: Brouer, Jesper <[email protected]>; Lorenzo Bianconi
> <[email protected]>; Karlsson, Magnus
> <[email protected]>; [email protected]
> Subject: Re: XDP multi-buffer and AF_XDP
> 
> 
> On 01/04/2022 13.39, Toke Høiland-Jørgensen wrote:
> > Kal Cutter Conley <[email protected]> writes:
> >
> >>>
> >>> Hi,
> >>> We are very interested in receiving jumbo frames (> 8000 bytes) over
> >>> AF_XDP. Does XDP multi-buffer support XDP_REDIRECT with AF_XDP?
> What
> >>> about in zero-copy mode?
> >>>
> >>> Cheers,
> >>> Kal
> >>
> >> Looking into this more I found this comment in the mlx5 driver:
> >>
> >> /* Don't enable multi buffer on XDP_REDIRECT SQ, as it's not yet
> >> * supported by upstream, and there is no defined trigger to allow
> >> * transmitting redirected multi-buffer frames.
> >> */
> >>
> >> So at least mlx5 does not yet support XDP multi-buffer with
> >> XDP_REDIRECT. What "upstream" support is required to get
> XDP_REDIRECT
> >> to work with XSKs?
> >
> > Well, the initial patch set for multibuf explicitly blocked
> > XDP_REDIRECT between interfaces, which is what that comment is
> > referring to (the TX side).
> >
> > For AF_XDP we'd also need to define the UAPI, and maybe add a socket
> > flag so the userspace program can signal to the kernel that it
> > understands it? Not sure about the details.
> >
> > You're definitely not the only person who wants this, though; adding
> > in some people who may have a better idea of the exact steps needed.
> 
> Cc. Eric Sage, as he also expressed interest in implementing this...

Adding Tirtha that has patches for the AF_XDP support of multi-buffer. Though, he is currently integrating his i40e multi-buffer driver support with Lorenzo's TX-patches that he sent as an RFC. Latest I heard is that Tirtha is planning on submitting this in a couple of weeks as a proper patch to the mailing list. And after that, the focus is to brush up the AF_XDP and ZC support patches as we stopped trying to track Lorenzo's multi-buffer patches at version 13 out of 23 ;-). We just could not keep up.

> --Jesper