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net: stmmac: preserve real_num_tx_queues on mqprio setup failure

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With the FPE preemption-class mapping error now propagated from
stmmac_fpe_map_preemption_class(), tc_setup_dwmac510_mqprio() can fail
on the mapping step. The error path used to call stmmac_reset_tc_mqprio(),
which resets the number of real TX queues to priv->plat->tx_queues_to_use
(the platform maximum), overwriting the value that was active before the
offload was attempted (for example a lower count left over from a previous
mqprio configuration).

The issue can be triggered using the following configuration:

  # First mqprio config lowers the hw queue count below the platform
  # default (e.g. 8 TX queues).
  $tc qdisc add dev eth0 root handle 1: mqprio queues 2@0 2@2

  # Replace mqprio configuration with a second one that fails FPE
  # preemption-class mapping. stmmac driver resets the real_num_tx_queues
  # to the platform maximum, losing the previous configuration.
  $tc qdisc replace dev eth0 root handle 2: mqprio queues 2@0 2@2 fp E P

Save ndev->real_num_tx_queues before lowering it and restore it,
together with the TC-to-queue and priority-to-TC mappings, when the FPE
preemption-class mapping fails, instead of resetting the queue count to
the platform maximum.

Note that a failed setup makes the qdisc layer run mqprio_destroy() on
the new qdisc. Because priv->hw_offload is only assigned after
ndo_setup_tc() succeeds, mqprio_destroy() calls netdev_set_num_tc(dev, 0),
so dev->num_tc ends up 0 regardless of the driver-side restore and the
previous qdisc is not reactivated. The restore is still needed to keep
real_num_tx_queues and to avoid leaving the failed configuration's
TC-to-queue and priority-to-TC mappings in place.

Fixes: 195e4f409a ("net: stmmac: support fp parameter of tc-mqprio")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
Link: https://patch.msgid.link/20260911-stmmac-tc_setup_dwmac510_mqprio-error-path-v3-2-a76b1e2547c1@oss.qualcomm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Lorenzo Bianconi 2026-09-11 10:58:30 +02:00 committed by Jakub Kicinski
parent 90e4b849df
commit 02fffd1939
1 changed files with 61 additions and 19 deletions
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80
drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
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@ -1237,6 +1237,30 @@ static int tc_query_caps(struct stmmac_priv *priv,
}
}
static int stmmac_set_ndev_tcs(struct net_device *ndev, u8 ntc,
struct netdev_tc_txq *tc_to_txq)
{
int i, err;
netdev_reset_tc(ndev);
if (!ntc)
return 0;
err = netdev_set_num_tc(ndev, ntc);
if (err)
return err;
for (i = 0; i < ntc; i++) {
u16 count, offset;
count = tc_to_txq[i].count;
offset = tc_to_txq[i].offset;
netdev_set_tc_queue(ndev, i, count, offset);
}
return 0;
}
static int stmmac_reset_tc_mqprio(struct net_device *ndev,
struct netlink_ext_ack *extack)
{
@ -1251,43 +1275,61 @@ static int stmmac_reset_tc_mqprio(struct net_device *ndev,
static int tc_setup_dwmac510_mqprio(struct stmmac_priv *priv,
struct tc_mqprio_qopt_offload *mqprio)
{
unsigned int ndev_num_tx_queues, num_tx_queues = 0;
struct netdev_tc_txq ndev_tc_to_txq[TC_MAX_QUEUE];
struct netdev_tc_txq tc_to_txq[TC_MAX_QUEUE] = {};
struct netlink_ext_ack *extack = mqprio->extack;
struct tc_mqprio_qopt *qopt = &mqprio->qopt;
u32 offset, count, num_stack_tx_queues = 0;
struct net_device *ndev = priv->dev;
u32 num_tc = qopt->num_tc;
int err;
u8 ndev_prio_tc_map[TC_BITMASK + 1];
int i, err, ndev_ntc;
if (!num_tc)
if (!qopt->num_tc)
return stmmac_reset_tc_mqprio(ndev, extack);
err = netdev_set_num_tc(ndev, num_tc);
if (err)
return err;
if (qopt->num_tc > ARRAY_SIZE(tc_to_txq))
return -EINVAL;
for (u32 tc = 0; tc < num_tc; tc++) {
offset = qopt->offset[tc];
count = qopt->count[tc];
num_stack_tx_queues += count;
/* save current tc values for reset */
ndev_ntc = netdev_get_num_tc(ndev);
for (i = 0; i < ARRAY_SIZE(ndev->tc_to_txq); i++)
ndev_tc_to_txq[i].combined =
READ_ONCE(ndev->tc_to_txq[i].combined);
for (i = 0; i < ARRAY_SIZE(ndev_prio_tc_map); i++)
ndev_prio_tc_map[i] = READ_ONCE(ndev->prio_tc_map[i]);
err = netdev_set_tc_queue(ndev, tc, count, offset);
if (err)
goto err_reset_tc;
for (i = 0; i < qopt->num_tc; i++) {
tc_to_txq[i] = (struct netdev_tc_txq) {
.count = qopt->count[i],
.offset = qopt->offset[i],
};
num_tx_queues += qopt->count[i];
}
err = netif_set_real_num_tx_queues(ndev, num_stack_tx_queues);
err = stmmac_set_ndev_tcs(ndev, qopt->num_tc, tc_to_txq);
if (err)
goto err_reset_tc;
goto error_reset_tc;
ndev_num_tx_queues = ndev->real_num_tx_queues;
err = netif_set_real_num_tx_queues(ndev, num_tx_queues);
if (err)
goto error_reset_tc;
err = stmmac_fpe_map_preemption_class(priv, ndev, extack,
mqprio->preemptible_tcs);
if (err)
goto err_reset_tc;
goto error_reset_num_tx_queues;
return 0;
err_reset_tc:
stmmac_reset_tc_mqprio(ndev, extack);
error_reset_num_tx_queues:
if (netif_set_real_num_tx_queues(ndev, ndev_num_tx_queues))
netdev_warn(ndev, "Failed to restore %u TX queues\n",
ndev_num_tx_queues);
error_reset_tc:
stmmac_set_ndev_tcs(ndev, ndev_ntc, ndev_tc_to_txq);
for (i = 0; i < ARRAY_SIZE(ndev_prio_tc_map); i++)
netdev_set_prio_tc_map(ndev, i, ndev_prio_tc_map[i]);
return err;
}