linux-kernel - Re: [PATCH iwl-net 2/3] ice: add flag to distinguish reset from .ndo

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Date: Thu, 16 May 2024 09:27:33 +0100
From: Simon Horman <horms@...nel.org>
To: Larysa Zaremba <larysa.zaremba@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org,
	Jacob Keller <jacob.e.keller@...el.com>,
	maciej.fijalkowski@...el.com,
	Magnus Karlsson <magnus.karlsson@...il.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	igor.bagnucki@...el.com, "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>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH iwl-net 2/3] ice: add flag to distinguish reset from
 .ndo_bpf in XDP rings config

On Wed, May 15, 2024 at 06:02:15PM +0200, Larysa Zaremba wrote:
> Commit 6624e780a577 ("ice: split ice_vsi_setup into smaller functions")
> has placed ice_vsi_free_q_vectors() after ice_destroy_xdp_rings() in
> the rebuild process. The behaviour of the XDP rings config functions is
> context-dependent, so the change of order has led to
> ice_destroy_xdp_rings() doing additional work and removing XDP prog, when
> it was supposed to be preserved.
> 
> Also, dependency on the PF state reset flags creates an additional,
> fortunately less common problem:
> 
> * PFR is requested e.g. by tx_timeout handler
> * .ndo_bpf() is asked to delete the program, calls ice_destroy_xdp_rings(),
>   but reset flag is set, so rings are destroyed without deleting the
>   program
> * ice_vsi_rebuild tries to delete non-existent XDP rings, because the
>   program is still on the VSI
> * system crashes
> 
> With a similar race, when requested to attach a program,
> ice_prepare_xdp_rings() can actually skip setting the program in the VSI
> and nevertheless report success.
> 
> Instead of reverting to the old order of function calls, add an enum
> argument to both ice_prepare_xdp_rings() and ice_destroy_xdp_rings() in
> order to distinguish between calls from rebuild and .ndo_bpf().
> 
> Fixes: efc2214b6047 ("ice: Add support for XDP")
> Reviewed-by: Igor Bagnucki <igor.bagnucki@...el.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>

Reviewed-by: Simon Horman <horms@...nel.org>