netdev - Re: [PATCH bpf-next 6/7] bpf: devmap: check XDP features in bpf_map_update_elem and __xdp

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Message-ID: <Y88YQzh1WCjFTmGl@lore-desk>
Date:   Tue, 24 Jan 2023 00:29:07 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Martin KaFai Lau <martin.lau@...ux.dev>, netdev@...r.kernel.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        davem@...emloft.net, hawk@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, toke@...hat.com, memxor@...il.com,
        alardam@...il.com, saeedm@...dia.com, anthony.l.nguyen@...el.com,
        gospo@...adcom.com, vladimir.oltean@....com, nbd@....name,
        john@...ozen.org, leon@...nel.org, simon.horman@...igine.com,
        aelior@...vell.com, christophe.jaillet@...adoo.fr,
        ecree.xilinx@...il.com, mst@...hat.com, bjorn@...nel.org,
        magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
        intel-wired-lan@...ts.osuosl.org, lorenzo.bianconi@...hat.com,
        niklas.soderlund@...igine.com, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next 6/7] bpf: devmap: check XDP features in
 bpf_map_update_elem and __xdp_enqueue

On Jan 23, Jakub Kicinski wrote:
> On Sun, 22 Jan 2023 13:13:41 +0100 Lorenzo Bianconi wrote:
> > > > diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> > > > index d01e4c55b376..69ceecc792df 100644
> > > > --- a/kernel/bpf/devmap.c
> > > > +++ b/kernel/bpf/devmap.c
> > > > @@ -474,7 +474,11 @@ static inline int __xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
> > > >   {
> > > >   	int err;
> > > > -	if (!dev->netdev_ops->ndo_xdp_xmit)
> > > > +	if (!(dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT))  
> > > 
> > > The current "dev->netdev_ops->ndo_xdp_xmit" check is self explaining.
> > > Any plan to put some document for the NETDEV_XDP_ACT_* values?
> > >   
> > 
> > I am not a yaml description expert but I guess we can xdp features description
> > in Documentation/netlink/specs/netdev.yaml.
> > 
> > @Jakub: what do you think?
> 
> I've added the ability to document enums recently, so you may need
> to rebase. But it should work and render the documentation as kdoc 
> in the uAPI header (hopefully in a not-too-ugly way).
> 
> Example of YAML:
> https://github.com/kuba-moo/ynl/blob/dpll/Documentation/netlink/specs/dpll.yaml#L27-L46

ack, it works properly I guess, I got the following kdoc in the uAPI:

/**
 * enum netdev_xdp_act
 * @NETDEV_XDP_ACT_BASIC: XDP feautues set supported by all drivers
 *   (XDP_ABORTED, XDP_DROP, XDP_PASS, XDP_TX)
 * @NETDEV_XDP_ACT_REDIRECT: The netdev supports XDP_REDIRECT
 * @NETDEV_XDP_ACT_NDO_XMIT: This feature informs if netdev implements
 *   ndo_xdp_xmit callback.
 * @NETDEV_XDP_ACT_XSK_ZEROCOPY: This feature informs if netdev supports AF_XDP
 *   in zero copy mode.
 * @NETDEV_XDP_ACT_HW_OFFLOAD: This feature informs if netdev supports XDP hw
 *   oflloading.
 * @NETDEV_XDP_ACT_RX_SG: This feature informs if netdev implements non-linear
 *   XDP buffer support in the driver napi callback.
 * @NETDEV_XDP_ACT_NDO_XMIT_SG: This feature informs if netdev implements
 *   non-linear XDP buffer support in ndo_xdp_xmit callback.
 */
enum netdev_xdp_act {
        NETDEV_XDP_ACT_BASIC,
        NETDEV_XDP_ACT_REDIRECT,
        NETDEV_XDP_ACT_NDO_XMIT,
        NETDEV_XDP_ACT_XSK_ZEROCOPY,
        NETDEV_XDP_ACT_HW_OFFLOAD,
        NETDEV_XDP_ACT_RX_SG,
        NETDEV_XDP_ACT_NDO_XMIT_SG,
};

Regards,
Lorenzo

> 
> I've also talked to the iproute2-py maintainer about generating
> documentation directly from YAML to Sphinx/htmldocs, hopefully 
> that will happen, too. It would be good to have a few families 
> to work with before we start that work, tho.

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