netdev - Re: [PATCH v3 iwl-next] ice: allow hot-swapping XDP programs

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Date: Fri, 16 Jun 2023 16:05:13 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
	<anthony.l.nguyen@...el.com>, <magnus.karlsson@...el.com>,
	<fred@...udflare.com>, <toke@...nel.org>
Subject: Re: [PATCH v3 iwl-next] ice: allow hot-swapping XDP programs

From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Date: Thu, 15 Jun 2023 13:33:26 +0200

> Currently ice driver's .ndo_bpf callback brings interface down and up
> independently of XDP resources' presence. This is only needed when
> either these resources have to be configured or removed. It means that
> if one is switching XDP programs on-the-fly with running traffic,
> packets will be dropped.
> 
> To avoid this, compare early on ice_xdp_setup_prog() state of incoming
> bpf_prog pointer vs the bpf_prog pointer that is already assigned to
> VSI. Do the swap in case VSI has bpf_prog and incoming one are non-NULL.
> 
> Lastly, while at it, put old bpf_prog *after* the update of Rx ring's
> bpf_prog pointer. In theory previous code could expose us to a state
> where Rx ring's bpf_prog would still be referring to old_prog that got
> released with earlier bpf_prog_put().
> 
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>

Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>

Good stuff, much missing previously.

[...]

Thanks,
Olek