netdev - Re: [PATCH v2 bpf-next 13/22] xsk: report ZC multi-buffer capability via xdp

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Date: Wed, 31 May 2023 15:20:09 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Magnus Karlsson <magnus.karlsson@...il.com>
CC: <bpf@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
	<andrii@...nel.org>, <netdev@...r.kernel.org>, <magnus.karlsson@...el.com>,
	<bjorn@...nel.org>, <tirthendu.sarkar@...el.com>
Subject: Re: [PATCH v2 bpf-next 13/22] xsk: report ZC multi-buffer capability
 via xdp_features

On Wed, May 31, 2023 at 12:16:13PM +0200, Magnus Karlsson wrote:
> On Mon, 29 May 2023 at 17:57, Maciej Fijalkowski
> <maciej.fijalkowski@...el.com> wrote:
> >
> > Introduce new xdp_feature NETDEV_XDP_ACT_NDO_ZC_SG that will be used to
> > find out if user space that wants to do ZC multi-buffer will be able to
> > do so against underlying ZC driver.
> >
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > ---
> >  include/uapi/linux/netdev.h | 4 ++--
> >  net/xdp/xsk_buff_pool.c     | 6 ++++++
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
> > index 639524b59930..bfca07224f7b 100644
> > --- a/include/uapi/linux/netdev.h
> > +++ b/include/uapi/linux/netdev.h
> > @@ -33,8 +33,8 @@ enum netdev_xdp_act {
> >         NETDEV_XDP_ACT_HW_OFFLOAD = 16,
> >         NETDEV_XDP_ACT_RX_SG = 32,
> >         NETDEV_XDP_ACT_NDO_XMIT_SG = 64,
> > -
> > -       NETDEV_XDP_ACT_MASK = 127,
> > +       NETDEV_XDP_ACT_NDO_ZC_SG = 128,
> 
> Since this flag has nothing to do with an NDO, I would prefer the
> simpler NETDEV_XDP_ACT_ZC_SG. What do you think?

+1, brain fart with that "NDO" on my side.

> 
> > +       NETDEV_XDP_ACT_MASK = 255,
> >  };
> >
> >  enum {
> > diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> > index 0a9f8ea68de3..43cca5fa90cf 100644
> > --- a/net/xdp/xsk_buff_pool.c
> > +++ b/net/xdp/xsk_buff_pool.c
> > @@ -189,6 +189,12 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
> >                 goto err_unreg_pool;
> >         }
> >
> > +       if (!(netdev->xdp_features & NETDEV_XDP_ACT_NDO_ZC_SG) &&
> > +           flags & XDP_USE_SG) {
> > +               err = -EOPNOTSUPP;
> > +               goto err_unreg_pool;
> > +       }
> > +
> >         bpf.command = XDP_SETUP_XSK_POOL;
> >         bpf.xsk.pool = pool;
> >         bpf.xsk.queue_id = queue_id;
> > --
> > 2.35.3
> >
> >
>