[PATCH v2 iwl-net] i40e: keep q_vectors array in sync with channel count changes

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

For the main VSI, i40e_set_num_rings_in_vsi() always derives
num_q_vectors from pf->num_lan_msix. At the same time, ethtool -L stores
the user requested channel count in vsi->req_queue_pairs and the queue
setup path uses that value for the effective number of queue pairs.

This leaves queue and vector counts out of sync after shrinking channel
count via ethtool -L. The active queue configuration is reduced, but the
VSI still keeps the full PF-sized q_vector topology.

That mismatch breaks reconfiguration flows which rely on vector/NAPI
state matching the effective channel configuration. In particular,
toggling /sys/class/net/<dev>/threaded after reducing the channel count
can hang, and later channel-count changes can fail because VSI reinit
does not rebuild q_vectors to match the new vector count.

Fix this by making the main VSI num_q_vectors follow the effective
requested channel count, capped by the available MSI-X vectors. Update
i40e_vsi_reinit_setup() to rebuild q_vectors during VSI reinit so the
vector topology is refreshed together with the ring arrays when channel
count changes.

Keep alloc_queue_pairs unchanged and based on pf->num_lan_qps so the VSI
retains its full queue capacity.

Selftest napi_threaded.py was originally used when Jakub reported hang
on /sys/class/net/<dev>/threaded toggle. In order to make it pass on
i40e, use persistent NAPI configuration for q_vector NAPIs so NAPI
identity and threaded settings survive q_vector reallocation across
channel-count changes. This is achieved by using netif_napi_add_config()
when configuring q_vectors.

$ export NETIF=ens259f1np1
$ sudo -E env PATH="$PATH" ./tools/testing/selftests/drivers/net/napi_threaded.py
TAP version 13
1..3
ok 1 napi_threaded.napi_init
ok 2 napi_threaded.change_num_queues
ok 3 napi_threaded.enable_dev_threaded_disable_napi_threaded
Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0

Reported-by: Jakub Kicinski <kuba@kernel.org>
Closes: https://lore.kernel.org/intel-wired-lan/20260316133100.6054a11f@kernel.org/
Fixes: d2a69fefd756 ("i40e: Fix changing previously set num_queue_pairs for PFs")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
v2:
- NULL vsi->tx_rings in i40e_vsi_alloc_arrays() (Sashiko)
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 35 +++++++++++++++++----
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 926d001b2150..1d2a4181966f 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -11403,10 +11403,14 @@ static void i40e_service_timer(struct timer_list *t)
 static int i40e_set_num_rings_in_vsi(struct i40e_vsi *vsi)
 {
 	struct i40e_pf *pf = vsi->back;
+	u16 qps;
 
 	switch (vsi->type) {
 	case I40E_VSI_MAIN:
 		vsi->alloc_queue_pairs = pf->num_lan_qps;
+		qps = vsi->req_queue_pairs ?
+		      min_t(u16, vsi->req_queue_pairs, pf->num_lan_qps) :
+		      pf->num_lan_qps;
 		if (!vsi->num_tx_desc)
 			vsi->num_tx_desc = ALIGN(I40E_DEFAULT_NUM_DESCRIPTORS,
 						 I40E_REQ_DESCRIPTOR_MULTIPLE);
@@ -11414,7 +11418,8 @@ static int i40e_set_num_rings_in_vsi(struct i40e_vsi *vsi)
 			vsi->num_rx_desc = ALIGN(I40E_DEFAULT_NUM_DESCRIPTORS,
 						 I40E_REQ_DESCRIPTOR_MULTIPLE);
 		if (test_bit(I40E_FLAG_MSIX_ENA, pf->flags))
-			vsi->num_q_vectors = pf->num_lan_msix;
+			vsi->num_q_vectors = max_t(int, 1,
+						   min_t(int, qps, pf->num_lan_msix));
 		else
 			vsi->num_q_vectors = 1;
 
@@ -11503,6 +11508,7 @@ static int i40e_vsi_alloc_arrays(struct i40e_vsi *vsi, bool alloc_qvectors)
 
 err_vectors:
 	kfree(vsi->tx_rings);
+	vsi->tx_rings = NULL;
 	return ret;
 }
 
@@ -12043,7 +12049,8 @@ static int i40e_vsi_alloc_q_vector(struct i40e_vsi *vsi, int v_idx)
 	cpumask_copy(&q_vector->affinity_mask, cpu_possible_mask);
 
 	if (vsi->netdev)
-		netif_napi_add(vsi->netdev, &q_vector->napi, i40e_napi_poll);
+		netif_napi_add_config(vsi->netdev, &q_vector->napi,
+				      i40e_napi_poll, v_idx);
 
 	/* tie q_vector and vsi together */
 	vsi->q_vectors[v_idx] = q_vector;
@@ -14265,12 +14272,27 @@ static struct i40e_vsi *i40e_vsi_reinit_setup(struct i40e_vsi *vsi)
 
 	pf = vsi->back;
 
+	if (test_bit(I40E_FLAG_MSIX_ENA, pf->flags)) {
+		i40e_put_lump(pf->irq_pile, vsi->base_vector, vsi->idx);
+		vsi->base_vector = 0;
+	}
+
 	i40e_put_lump(pf->qp_pile, vsi->base_queue, vsi->idx);
 	i40e_vsi_clear_rings(vsi);
 
-	i40e_vsi_free_arrays(vsi, false);
+	i40e_vsi_free_q_vectors(vsi);
+	i40e_vsi_free_arrays(vsi, true);
 	i40e_set_num_rings_in_vsi(vsi);
-	ret = i40e_vsi_alloc_arrays(vsi, false);
+
+	ret = i40e_vsi_alloc_arrays(vsi, true);
+	if (ret)
+		goto err_vsi;
+
+	/* Rebuild q_vectors during VSI reinit because the effective channel
+	 * count may change num_q_vectors. Keep vector topology aligned with the
+	 * queue configuration after ethtool's .set_channels() callback.
+	 */
+	ret = i40e_vsi_setup_vectors(vsi);
 	if (ret)
 		goto err_vsi;
 
@@ -14282,7 +14304,7 @@ static struct i40e_vsi *i40e_vsi_reinit_setup(struct i40e_vsi *vsi)
 		dev_info(&pf->pdev->dev,
 			 "failed to get tracking for %d queues for VSI %d err %d\n",
 			 alloc_queue_pairs, vsi->seid, ret);
-		goto err_vsi;
+		goto err_lump;
 	}
 	vsi->base_queue = ret;
 
@@ -14306,7 +14328,6 @@ static struct i40e_vsi *i40e_vsi_reinit_setup(struct i40e_vsi *vsi)
 	return vsi;
 
 err_rings:
-	i40e_vsi_free_q_vectors(vsi);
 	if (vsi->netdev_registered) {
 		vsi->netdev_registered = false;
 		unregister_netdev(vsi->netdev);
@@ -14316,6 +14337,8 @@ static struct i40e_vsi *i40e_vsi_reinit_setup(struct i40e_vsi *vsi)
 	if (vsi->type == I40E_VSI_MAIN)
 		i40e_devlink_destroy_port(pf);
 	i40e_aq_delete_element(&pf->hw, vsi->seid, NULL);
+err_lump:
+	i40e_vsi_free_q_vectors(vsi);
 err_vsi:
 	i40e_vsi_clear(vsi);
 	return NULL;
-- 
2.43.0