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

[Rout, ChandanX]

>-----Original Message-----
>From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
>Zaremba, Larysa
>Sent: Thursday, April 18, 2024 3:29 PM
>To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; intel-wired-
>lan@xxxxxxxxxxxxxxxx; 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: Chandan Kumar Rout <chandanx.rout@xxxxxxxxx> (A Contingent Worker at Intel)