Received-SPF: pass (google.com: domain of linux-kernel+bounces-180762-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Thu, 16 May 2024 09:27:33 +0100
From: Simon Horman <horms@kernel.org>
To: Larysa Zaremba <larysa.zaremba@intel.com>
Cc: intel-wired-lan@lists.osuosl.org,
	Jacob Keller <jacob.e.keller@intel.com>,
	maciej.fijalkowski@intel.com,
	Magnus Karlsson <magnus.karlsson@gmail.com>,
	Przemek Kitszel <przemyslaw.kitszel@intel.com>,
	igor.bagnucki@intel.com, "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH iwl-net 2/3] ice: add flag to distinguish reset from
 .ndo_bpf in XDP rings config
Message-ID: <20240516082733.GD179178@kernel.org>
References: <20240515160246.5181-1-larysa.zaremba@intel.com>
 <20240515160246.5181-3-larysa.zaremba@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240515160246.5181-3-larysa.zaremba@intel.com>

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@intel.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>

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