On Tue, Apr 16, 2024 at 02:58:54PM +0200, Larysa Zaremba wrote:
> 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 */
Makes sense for usage above:
Acked-by: Maciej Fijalkowski <[email protected]>
Nonetheless I still think core should not allow user to shoot himself to
foot, but let's keep it as a separate thing.
Thanks!
>
> [0] https://man7.org/linux/man-pages/man8/ethtool.8.html
>
> Fixes: 87324e747fde ("ice: Implement ethtool ops for channels")
> Reviewed-by: Michal Swiatkowski <[email protected]>
> Signed-off-by: Larysa Zaremba <[email protected]>
> ---
> drivers/net/ethernet/intel/ice/ice_ethtool.c | 22 ++++++--------------
> 1 file changed, 6 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c
> b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> index 78b833b3e1d7..d91f41f61bce 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> @@ -3593,7 +3593,6 @@ static int ice_set_channels(struct net_device *dev,
> struct ethtool_channels *ch)
> struct ice_pf *pf = vsi->back;
> int new_rx = 0, new_tx = 0;
> bool locked = false;
> - u32 curr_combined;
> int ret = 0;
>
> /* do not support changing channels in Safe Mode */
> @@ -3615,22 +3614,13 @@ static int ice_set_channels(struct net_device *dev,
> struct ethtool_channels *ch)
> return -EOPNOTSUPP;
> }
>
> - curr_combined = ice_get_combined_cnt(vsi);
> + if (!ch->combined_count) {
> + netdev_err(dev, "Please specify at least 1 combined channel\n");
> + return -EINVAL;
> + }
>
> - /* these checks are for cases where user didn't specify a particular
> - * value on cmd line but we get non-zero value anyway via
> - * get_channels(); look at ethtool.c in ethtool repository (the user
> - * space part), particularly, do_schannels() routine
> - */
> - if (ch->rx_count == vsi->num_rxq - curr_combined)
> - ch->rx_count = 0;
> - if (ch->tx_count == vsi->num_txq - curr_combined)
> - ch->tx_count = 0;
> - if (ch->combined_count == curr_combined)
> - ch->combined_count = 0;
> -
> - if (!(ch->combined_count || (ch->rx_count && ch->tx_count))) {
> - netdev_err(dev, "Please specify at least 1 Rx and 1 Tx
> channel\n");
> + if (ch->rx_count && ch->tx_count) {
> + netdev_err(dev, "Dedicated RX or TX channels cannot be used
> simultaneously\n");
> return -EINVAL;
> }
>
> --
> 2.43.0
>
