Merge branch 'intel-interpret-set_channels-input-differently'

Jacob Keller says:

====================
intel: Interpret .set_channels() input differently

The ice and idpf drivers can trigger a crash with AF_XDP due to incorrect
interpretation of the asymmetric Tx and Rx parameters in their
.set_channels() implementations:

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. the driver interprets `rx 15 tx 15` as 15 combined channels and deletes
   the queue that AF_XDP is attached to.

This is fundamentally a problem with interpreting a request for asymmetric
queues as symmetric combined queues.

Fix the ice and idpf drivers to stop interpreting such requests as a
request for combined queues. Due to current driver design for both ice and
idpf, it is not possible to support requests of the same count of Tx and Rx
queues with independent interrupts, (i.e. ethtool -L <IFNAME> rx 15 tx 15)
so such requests are now rejected.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
====================

Link: https://lore.kernel.org/r/20240521-iwl-net-2024-05-14-set-channels-fixes-v2-0-7aa39e2e99f1@intel.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

2 files changed, 8 insertions, 32 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
index 78b833b3e1d7..62c8205fceba 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 +3614,8 @@ static int ice_set_channels(struct net_device *dev, struct ethtool_channels *ch)
 		return -EOPNOTSUPP;
 	}
 
-	curr_combined = ice_get_combined_cnt(vsi);
-
-	/* 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;
 	}
 
diff --git a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
index 6972d728431c..1885ba618981 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
@@ -222,14 +222,19 @@ static int idpf_set_channels(struct net_device *netdev,
 			     struct ethtool_channels *ch)
 {
 	struct idpf_vport_config *vport_config;
-	u16 combined, num_txq, num_rxq;
 	unsigned int num_req_tx_q;
 	unsigned int num_req_rx_q;
 	struct idpf_vport *vport;
+	u16 num_txq, num_rxq;
 	struct device *dev;
 	int err = 0;
 	u16 idx;
 
+	if (ch->rx_count && ch->tx_count) {
+		netdev_err(netdev, "Dedicated RX or TX channels cannot be used simultaneously\n");
+		return -EINVAL;
+	}
+
 	idpf_vport_ctrl_lock(netdev);
 	vport = idpf_netdev_to_vport(netdev);
 
@@ -239,20 +244,6 @@ static int idpf_set_channels(struct net_device *netdev,
 	num_txq = vport_config->user_config.num_req_tx_qs;
 	num_rxq = vport_config->user_config.num_req_rx_qs;
 
-	combined = min(num_txq, num_rxq);
-
-	/* 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->combined_count == combined)
-		ch->combined_count = 0;
-	if (ch->combined_count && ch->rx_count == num_rxq - combined)
-		ch->rx_count = 0;
-	if (ch->combined_count && ch->tx_count == num_txq - combined)
-		ch->tx_count = 0;
-
 	num_req_tx_q = ch->combined_count + ch->tx_count;
 	num_req_rx_q = ch->combined_count + ch->rx_count;