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

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Message-ID: <428cc7b6-fc80-4028-a9bb-ce65646005f5@intel.com>
Date: Mon, 17 Mar 2025 15:58:12 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...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

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 =\

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

Thanks,
Olek