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s390/qeth: allow configuration of TX queues for IQD devices

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Similar to the support for z/VM NICs, but we need to take extra care
about the dedicated mcast queue:

1. netdev_pick_tx() is unaware of this limitation and might select the
   mcast txq. Catch this.
2. require at least _two_ TX queues - one for ucast, one for mcast.
3. when reducing the number of TX queues, there's a potential race
   where netdev_cap_txqueue() over-rules the selected txq index and
   falls back to index 0. This would place ucast traffic on the mcast
   queue, and result in TX errors.
   So for IQD, reject a reduction while the interface is running.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Julian Wiedmann 2020-03-18 13:54:49 +01:00 committed by David S. Miller
parent fcc2df8b87
commit 66cddf1019
2 changed files with 21 additions and 4 deletions
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6
drivers/s390/net/qeth_core_main.c
View File

@ -6644,9 +6644,13 @@ EXPORT_SYMBOL_GPL(qeth_get_stats64);
u16 qeth_iqd_select_queue(struct net_device *dev, struct sk_buff *skb,
u8 cast_type, struct net_device *sb_dev)
{
u16 txq;
if (cast_type != RTN_UNICAST)
return QETH_IQD_MCAST_TXQ;
return QETH_IQD_MIN_UCAST_TXQ;
txq = netdev_pick_tx(dev, skb, sb_dev);
return (txq == QETH_IQD_MCAST_TXQ) ? QETH_IQD_MIN_UCAST_TXQ : txq;
}
EXPORT_SYMBOL_GPL(qeth_iqd_select_queue);

19
drivers/s390/net/qeth_ethtool.c
View File

@ -180,14 +180,27 @@ static int qeth_set_channels(struct net_device *dev,
{
struct qeth_card *card = dev->ml_priv;
if (IS_IQD(card) || !IS_VM_NIC(card))
return -EOPNOTSUPP;
if (channels->rx_count == 0 || channels->tx_count == 0)
return -EINVAL;
if (channels->tx_count > card->qdio.no_out_queues)
return -EINVAL;
if (IS_IQD(card)) {
if (channels->tx_count < QETH_IQD_MIN_TXQ)
return -EINVAL;
/* Reject downgrade while running. It could push displaced
* ucast flows onto txq0, which is reserved for mcast.
*/
if (netif_running(dev) &&
channels->tx_count < dev->real_num_tx_queues)
return -EPERM;
} else {
/* OSA still uses the legacy prio-queue mechanism: */
if (!IS_VM_NIC(card))
return -EOPNOTSUPP;
}
return netif_set_real_num_tx_queues(dev, channels->tx_count);
}