Re: XDP multi-buffer and AF_XDP

On Fri, Apr 01, 2022 at 01:26:12PM +0000, Karlsson, Magnus wrote:
> 
> 
> > -----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.

Ah, if there is anything I can do to help please let me know. My company needs this
feature so I can work on it full time. I would love to help out however I can.

Thanks,
Eric Sage
> 
> > --Jesper
>