linux-kernel - Re: [PATCH net-next 12/16] idpf: implement XDP_SETUP_PROG in ndo

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Message-ID: <Z9rvaVu460sZkUXD@boxer>
Date: Wed, 19 Mar 2025 17:23:05 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, Michal Kubiak
	<michal.kubiak@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, "Przemek
 Kitszel" <przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, Simon Horman <horms@...nel.org>,
	<bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 12/16] idpf: implement XDP_SETUP_PROG in ndo_bpf
 for splitq

On Mon, Mar 17, 2025 at 03:58:12PM +0100, Alexander Lobakin wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Date: Fri, 7 Mar 2025 15:16:48 +0100
> 
> > On Wed, Mar 05, 2025 at 05:21:28PM +0100, Alexander Lobakin wrote:
> >> From: Michal Kubiak <michal.kubiak@...el.com>
> >>
> >> Implement loading/removing XDP program using .ndo_bpf callback
> >> in the split queue mode. Reconfigure and restart the queues if needed
> >> (!!old_prog != !!new_prog), otherwise, just update the pointers.
> >>
> >> Signed-off-by: Michal Kubiak <michal.kubiak@...el.com>
> >> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> >> ---
> >>  drivers/net/ethernet/intel/idpf/idpf_txrx.h |   4 +-
> >>  drivers/net/ethernet/intel/idpf/xdp.h       |   7 ++
> >>  drivers/net/ethernet/intel/idpf/idpf_lib.c  |   1 +
> >>  drivers/net/ethernet/intel/idpf/idpf_txrx.c |   4 +
> >>  drivers/net/ethernet/intel/idpf/xdp.c       | 114 ++++++++++++++++++++
> >>  5 files changed, 129 insertions(+), 1 deletion(-)
> >>
> > 
> > (...)
> > 
> >> +
> >> +/**
> >> + * idpf_xdp_setup_prog - handle XDP program install/remove requests
> >> + * @vport: vport to configure
> >> + * @xdp: request data (program, extack)
> >> + *
> >> + * Return: 0 on success, -errno on failure.
> >> + */
> >> +static int
> >> +idpf_xdp_setup_prog(struct idpf_vport *vport, const struct netdev_bpf *xdp)
> >> +{
> >> +	const struct idpf_netdev_priv *np = netdev_priv(vport->netdev);
> >> +	struct bpf_prog *old, *prog = xdp->prog;
> >> +	struct idpf_vport_config *cfg;
> >> +	int ret;
> >> +
> >> +	cfg = vport->adapter->vport_config[vport->idx];
> >> +	if (!vport->num_xdp_txq && vport->num_txq == cfg->max_q.max_txq) {
> >> +		NL_SET_ERR_MSG_MOD(xdp->extack,
> >> +				   "No Tx queues available for XDP, please decrease the number of regular SQs");
> >> +		return -ENOSPC;
> >> +	}
> >> +
> >> +	if (test_bit(IDPF_REMOVE_IN_PROG, vport->adapter->flags) ||
> > 
> > IN_PROG is a bit unfortunate here as it mixes with 'prog' :P
> 
> Authentic idpf dictionary ¯\_(ツ)_/¯
> 
> > 
> >> +	    !!vport->xdp_prog == !!prog) {
> >> +		if (np->state == __IDPF_VPORT_UP)
> >> +			idpf_copy_xdp_prog_to_qs(vport, prog);
> >> +
> >> +		old = xchg(&vport->xdp_prog, prog);
> >> +		if (old)
> >> +			bpf_prog_put(old);
> >> +
> >> +		cfg->user_config.xdp_prog = prog;
> >> +
> >> +		return 0;
> >> +	}
> >> +
> >> +	old = cfg->user_config.xdp_prog;
> >> +	cfg->user_config.xdp_prog = prog;
> >> +
> >> +	ret = idpf_initiate_soft_reset(vport, IDPF_SR_Q_CHANGE);
> >> +	if (ret) {
> >> +		NL_SET_ERR_MSG_MOD(xdp->extack,
> >> +				   "Could not reopen the vport after XDP setup");
> >> +
> >> +		if (prog)
> >> +			bpf_prog_put(prog);
> > 
> > aren't you missing this for prog->NULL conversion? you have this for
> > hot-swap case (prog->prog).
> 
> This path (soft_reset) handles NULL => prog and prog => NULL. This
> branch in particular handles errors during the soft reset, when we need
> to restore the original prog and put the new one.
> 
> What you probably meant is that I don't have bpf_prog_put(old) in case
> everything went well below? Breh =\

yes, best to check with bpftool if there are dangling bpf progs on system
after using few xdp samples, for example.

> 
> > 
> >> +
> >> +		cfg->user_config.xdp_prog = old;
> >> +	}
> >> +
> >> +	return ret;
> >> +}
> 
> Thanks,
> Olek