RE: [Intel-wired-lan] [PATCH RESEND iwl-net] ice: Interpret .set_channels() input differently

[Pucha, HimasekharX Reddy]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of Larysa Zaremba
> Sent: Thursday, April 18, 2024 3:29 PM
> To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; intel-wired-lan@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Cc: Fijalkowski, Maciej <maciej.fijalkowski@xxxxxxxxx>; Tantilov, Emil S <emil.s.tantilov@xxxxxxxxx>; Zaremba, Larysa <larysa.zaremba@xxxxxxxxx>; Czapnik, Lukasz <lukasz.czapnik@xxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Brady, Alan <alan.brady@xxxxxxxxx>; Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>
> Subject: [Intel-wired-lan] [PATCH RESEND iwl-net] ice: Interpret .set_channels() input differently
>
> A bug occurs because a safety check guarding AF_XDP-related queues in ethnl_set_channels(), does not trigger. This happens, because kernel and ice driver interpret the ethtool command differently.
>
> How the bug occurs:
> 1. ethtool -l <IFNAME> -> combined: 40
> 2. Attach AF_XDP to queue 30
> 3. ethtool -L <IFNAME> rx 15 tx 15
>    combined number is not specified, so command becomes {rx_count = 15,
>    tx_count = 15, combined_count = 40}.
> 4. ethnl_set_channels checks, if there are any AF_XDP of queues from the
>    new (combined_count + rx_count) to the old one, so from 55 to 40, check
>    does not trigger.
> 5. ice interprets `rx 15 tx 15` as 15 combined channels and deletes the
>    queue that AF_XDP is attached to.
>
> Interpret the command in a way that is more consistent with ethtool manual [0] (--show-channels and --set-channels).
>
> Considering that in the ice 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://man7.org/linux/man-pages/man8/ethtool.8.html
>
> Fixes: 87324e747fde ("ice: Implement ethtool ops for channels")
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@xxxxxxxxx>
> ---
>  drivers/net/ethernet/intel/ice/ice_ethtool.c | 22 ++++++--------------
>  1 file changed, 6 insertions(+), 16 deletions(-)
>

Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@xxxxxxxxx> (A Contingent worker at Intel)