On Fri, Apr 26, 2024 at 05:41:22PM +0200, Larysa Zaremba wrote:
> Unlike ice, idpf does not check, if user has requested at least 1 combined
> channel. Instead, it relies on a check in the core code. Unfortunately, the
> check does not trigger for us because of the hacky .set_channels()
> interpretation logic that is not consistent with the core code.
>
> This naturally leads to user being able to trigger a crash with an invalid
> input. This is how:
>
> 1. ethtool -l <IFNAME> -> combined: 40
> 2. ethtool -L <IFNAME> rx 0 tx 0
> combined number is not specified, so command becomes {rx_count = 0,
> tx_count = 0, combined_count = 40}.
> 3. ethnl_set_channels checks, if there is at least 1 RX and 1 TX channel,
> comparing (combined_count + rx_count) and (combined_count + tx_count)
> to zero. Obviously, (40 + 0) is greater than zero, so the core code
> deems the input OK.
> 4. idpf interprets `rx 0 tx 0` as 0 channels and tries to proceed with such
> configuration.
>
> The issue has to be solved fundamentally, as current logic is also known to
> cause AF_XDP problems in ice [0].
>
> Interpret the command in a way that is more consistent with ethtool
> manual [1] (--show-channels and --set-channels) and new ice logic.
>
> Considering that in the idpf driver only the difference between RX and TX
> queues forms dedicated channels, change the correct way to set number of
> channels to:
>
> ethtool -L <IFNAME> combined 10 /* For symmetric queues */
> ethtool -L <IFNAME> combined 8 tx 2 rx 0 /* For asymmetric queues */
>
> [0]
> https://lore.kernel.org/netdev/20240418095857.2827-1-larysa.zare...@intel.com/
> [1] https://man7.org/linux/man-pages/man8/ethtool.8.html
>
> Fixes: 02cbfba1add5 ("idpf: add ethtool callbacks")
> Reviewed-by: Przemek Kitszel <przemyslaw.kits...@intel.com>
> Reviewed-by: Igor Bagnucki <igor.bagnu...@intel.com>
> Signed-off-by: Larysa Zaremba <larysa.zare...@intel.com>
Reviewed-by: Simon Horman <ho...@kernel.org>
