[PATCH v4 6/6] net/netvsc: support runtime queue count reconfiguration

Long Li
2026-03-03T20:55:02Z

Add support for changing the number of RX/TX queues at runtime
via port stop/configure/start. When the queue count changes,
perform a full NVS/RNDIS teardown and reinit to allocate fresh
VMBus subchannels matching the new queue count, then reconfigure
RSS indirection table accordingly.

Key changes:
- hn_dev_configure: detect queue count changes and perform full
NVS session reinit with subchannel teardown/recreation
- hn_dev_stop: drain pending TX completions (up to 1s) to prevent
stale completions from corrupting queue state after reconfig
- hn_vf_tx/rx_queue_release: use write lock when nulling VF queue
pointers to prevent use-after-free with concurrent fast-path
readers

Signed-off-by: Long Li <longli@microsoft.com>
---
v4: No changes.
v3: Fix subchan_cleanup to call hn_rndis_conf_offload. Fix recovery
path to set hv->primary->chan and call hn_chim_init.
v2: Split subchannel leak fix to separate patch. Fix reinit_failed
recovery to re-map before chan_open. Move hn_rndis_conf_offload
after reinit block. Use write lock in VF queue release. Reset
RSS table in subchan_cleanup error path.
---
drivers/net/netvsc/hn_ethdev.c | 194 +++++++++++++++++++++++++++++++--
drivers/net/netvsc/hn_vf.c | 16 ++-
2 files changed, 194 insertions(+), 16 deletions(-)

diff --git a/drivers/net/netvsc/hn_ethdev.c b/drivers/net/netvsc/hn_ethdev.c
index 23114a7c22..0b3eeb23cc 100644
--- a/drivers/net/netvsc/hn_ethdev.c
+++ b/drivers/net/netvsc/hn_ethdev.c
@@ -745,6 +745,9 @@ netvsc_hotadd_callback(const char *device_name, enum rte_dev_event_type type,
}
}

+static void hn_detach(struct hn_data *hv);
+static int hn_attach(struct hn_data *hv, unsigned int mtu);
+
static int hn_dev_configure(struct rte_eth_dev *dev)
{
struct rte_eth_conf *dev_conf = &dev->data->dev_conf;
@@ -754,6 +757,8 @@ static int hn_dev_configure(struct rte_eth_dev *dev)
struct hn_data *hv = dev->data->dev_private;
uint64_t unsupported;
int i, err, subchan;
+ uint32_t old_subchans = 0;
+ bool device_unmapped = false;

PMD_INIT_FUNC_TRACE();

@@ -778,36 +783,111 @@ static int hn_dev_configure(struct rte_eth_dev *dev)

hv->vlan_strip = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_VLAN_STRIP);

- err = hn_rndis_conf_offload(hv, txmode->offloads,
- rxmode->offloads);
- if (err) {
- PMD_DRV_LOG(NOTICE,
- "offload configure failed");
- return err;
- }
+ /* If queue count unchanged, skip subchannel teardown/reinit */
+ if (RTE_MAX(dev->data->nb_rx_queues,
+ dev->data->nb_tx_queues) == hv->num_queues)
+ goto skip_reinit;

hv->num_queues = RTE_MAX(dev->data->nb_rx_queues,
dev->data->nb_tx_queues);

+ /* Close all existing subchannels */
+ for (i = 1; i < HN_MAX_CHANNELS; i++) {
+ if (hv->channels[i] != NULL) {
+ rte_vmbus_chan_close(hv->channels[i]);
+ hv->channels[i] = NULL;
+ old_subchans++;
+ }
+ }
+
+ /*
+ * If subchannels existed, do a full NVS/RNDIS teardown
+ * and vmbus re-init to ensure a clean NVS session.
+ * Cannot re-send NVS subchannel request on the same
+ * session without invalidating the data path.
+ */
+ if (old_subchans > 0) {
+ PMD_DRV_LOG(NOTICE,
+ "reinit NVS (had %u subchannels)",
+ old_subchans);
+
+ hn_chim_uninit(dev);
+ rte_free(hv->primary->rxbuf_info);
+ hv->primary->rxbuf_info = NULL;
+ hn_detach(hv);
+
+ rte_vmbus_chan_close(hv->channels[0]);
+ rte_free(hv->channels[0]);
+ hv->channels[0] = NULL;
+
+ rte_vmbus_unmap_device(hv->vmbus);
+ device_unmapped = true;
+ err = rte_vmbus_map_device(hv->vmbus);
+ if (err) {
+ PMD_DRV_LOG(ERR,
+ "Could not re-map vmbus device!");
+ goto reinit_failed;
+ }
+ device_unmapped = false;
+
+ hv->rxbuf_res = hv->vmbus->resource[HV_RECV_BUF_MAP];
+ hv->chim_res = hv->vmbus->resource[HV_SEND_BUF_MAP];
+
+ err = rte_vmbus_chan_open(hv->vmbus, &hv->channels[0]);
+ if (err) {
+ PMD_DRV_LOG(ERR,
+ "Could not re-open vmbus channel!");
+ goto reinit_failed;
+ }
+
+ hv->primary->chan = hv->channels[0];
+
+ rte_vmbus_set_latency(hv->vmbus, hv->channels[0],
+ hv->latency);
+
+ err = hn_attach(hv, dev->data->mtu);
+ if (err) {
+ rte_vmbus_chan_close(hv->channels[0]);
+ rte_free(hv->channels[0]);
+ hv->channels[0] = NULL;
+ PMD_DRV_LOG(ERR,
+ "NVS reinit failed: %d", err);
+ goto reinit_failed;
+ }
+
+ err = hn_chim_init(dev);
+ if (err) {
+ hn_detach(hv);
+ rte_vmbus_chan_close(hv->channels[0]);
+ rte_free(hv->channels[0]);
+ hv->channels[0] = NULL;
+ PMD_DRV_LOG(ERR,
+ "chim reinit failed: %d", err);
+ goto reinit_failed;
+ }
+ }
+
for (i = 0; i < NDIS_HASH_INDCNT; i++)
hv->rss_ind[i] = i % dev->data->nb_rx_queues;

hn_rss_hash_init(hv, rss_conf);

subchan = hv->num_queues - 1;
+
+ /* Allocate fresh subchannels and configure RSS */
if (subchan > 0) {
err = hn_subchan_configure(hv, subchan);
if (err) {
PMD_DRV_LOG(NOTICE,
"subchannel configuration failed");
- return err;
+ goto subchan_cleanup;
}

err = hn_rndis_conf_rss(hv, NDIS_RSS_FLAG_DISABLE);
if (err) {
PMD_DRV_LOG(NOTICE,
"rss disable failed");
- return err;
+ goto subchan_cleanup;
}

if (rss_conf->rss_hf != 0) {
@@ -815,12 +895,82 @@ static int hn_dev_configure(struct rte_eth_dev *dev)
if (err) {
PMD_DRV_LOG(NOTICE,
"initial RSS config failed");
- return err;
+ goto subchan_cleanup;
}
}
}

+skip_reinit:
+ /* Apply offload config after reinit so it targets the final RNDIS session */
+ err = hn_rndis_conf_offload(hv, txmode->offloads,
+ rxmode->offloads);
+ if (err) {
+ PMD_DRV_LOG(NOTICE,
+ "offload configure failed");
+ return err;
+ }
+
return hn_vf_configure_locked(dev, dev_conf);
+
+subchan_cleanup:
+ for (i = 1; i < HN_MAX_CHANNELS; i++) {
+ if (hv->channels[i] != NULL) {
+ rte_vmbus_chan_close(hv->channels[i]);
+ hv->channels[i] = NULL;
+ }
+ }
+ hv->num_queues = 1;
+ for (i = 0; i < NDIS_HASH_INDCNT; i++)
+ hv->rss_ind[i] = 0;
+
+ /* Apply offload config so device is usable on primary queue */
+ hn_rndis_conf_offload(hv, txmode->offloads, rxmode->offloads);
+ return err;
+
+reinit_failed:
+ /*
+ * Device is in a broken state after failed reinit.
+ * Try to re-establish minimal connectivity.
+ */
+ PMD_DRV_LOG(ERR,
+ "reinit failed (err %d), attempting recovery", err);
+ if (hv->channels[0] == NULL) {
+ if (device_unmapped) {
+ if (rte_vmbus_map_device(hv->vmbus)) {
+ hv->num_queues = 0;
+ PMD_DRV_LOG(ERR,
+ "recovery failed, could not re-map device");
+ return err;
+ }
+ hv->rxbuf_res = hv->vmbus->resource[HV_RECV_BUF_MAP];
+ hv->chim_res = hv->vmbus->resource[HV_SEND_BUF_MAP];
+ }
+ if (rte_vmbus_chan_open(hv->vmbus, &hv->channels[0]) == 0) {
+ if (hn_attach(hv, dev->data->mtu) == 0) {
+ hv->primary->chan = hv->channels[0];
+ if (hn_chim_init(dev) != 0)
+ PMD_DRV_LOG(WARNING,
+ "chim reinit failed during recovery");
+ hv->num_queues = 1;
+ PMD_DRV_LOG(NOTICE,
+ "recovery successful on primary channel");
+ } else {
+ rte_vmbus_chan_close(hv->channels[0]);
+ rte_free(hv->channels[0]);
+ hv->channels[0] = NULL;
+ hv->num_queues = 0;
+ PMD_DRV_LOG(ERR,
+ "recovery failed, device unusable");
+ }
+ } else {
+ hv->num_queues = 0;
+ PMD_DRV_LOG(ERR,
+ "recovery failed, device unusable");
+ }
+ } else {
+ hv->num_queues = 1;
+ }
+ return err;
}

static int hn_dev_stats_get(struct rte_eth_dev *dev,
@@ -1073,6 +1223,7 @@ hn_dev_stop(struct rte_eth_dev *dev)
{
struct hn_data *hv = dev->data->dev_private;
int i, ret;
+ unsigned int retry;

PMD_INIT_FUNC_TRACE();
dev->data->dev_started = 0;
@@ -1081,6 +1232,29 @@ hn_dev_stop(struct rte_eth_dev *dev)
hn_rndis_set_rxfilter(hv, 0);
ret = hn_vf_stop(dev);

+ /*
+ * Drain pending TX completions to prevent stale completions
+ * from corrupting queue state after port reconfiguration.
+ */
+ for (retry = 0; retry < 100; retry++) {
+ uint32_t pending = 0;
+
+ for (i = 0; i < hv->num_queues; i++) {
+ struct hn_tx_queue *txq = dev->data->tx_queues[i];
+
+ if (txq == NULL)
+ continue;
+ hn_process_events(hv, i, 0);
+ pending += rte_mempool_in_use_count(txq->txdesc_pool);
+ }
+ if (pending == 0)
+ break;
+ rte_delay_ms(10);
+ }
+ if (retry >= 100)
+ PMD_DRV_LOG(WARNING,
+ "Failed to drain all TX completions");
+
for (i = 0; i < hv->num_queues; i++) {
dev->data->tx_queue_state[i] = RTE_ETH_QUEUE_STATE_STOPPED;
dev->data->rx_queue_state[i] = RTE_ETH_QUEUE_STATE_STOPPED;
diff --git a/drivers/net/netvsc/hn_vf.c b/drivers/net/netvsc/hn_vf.c
index 0ecfaf54ea..e77232bfb3 100644
--- a/drivers/net/netvsc/hn_vf.c
+++ b/drivers/net/netvsc/hn_vf.c
@@ -637,12 +637,14 @@ void hn_vf_tx_queue_release(struct hn_data *hv, uint16_t queue_id)
{
struct rte_eth_dev *vf_dev;

- rte_rwlock_read_lock(&hv->vf_lock);
+ rte_rwlock_write_lock(&hv->vf_lock);
vf_dev = hn_get_vf_dev(hv);
- if (vf_dev && vf_dev->dev_ops->tx_queue_release)
+ if (vf_dev && vf_dev->dev_ops->tx_queue_release) {
(*vf_dev->dev_ops->tx_queue_release)(vf_dev, queue_id);
+ vf_dev->data->tx_queues[queue_id] = NULL;
+ }

- rte_rwlock_read_unlock(&hv->vf_lock);
+ rte_rwlock_write_unlock(&hv->vf_lock);
}

int hn_vf_rx_queue_setup(struct rte_eth_dev *dev,
@@ -669,11 +671,13 @@ void hn_vf_rx_queue_release(struct hn_data *hv, uint16_t queue_id)
{
struct rte_eth_dev *vf_dev;

- rte_rwlock_read_lock(&hv->vf_lock);
+ rte_rwlock_write_lock(&hv->vf_lock);
vf_dev = hn_get_vf_dev(hv);
- if (vf_dev && vf_dev->dev_ops->rx_queue_release)
+ if (vf_dev && vf_dev->dev_ops->rx_queue_release) {
(*vf_dev->dev_ops->rx_queue_release)(vf_dev, queue_id);
- rte_rwlock_read_unlock(&hv->vf_lock);
+ vf_dev->data->rx_queues[queue_id] = NULL;
+ }
+ rte_rwlock_write_unlock(&hv->vf_lock);
}

int hn_vf_stats_get(struct rte_eth_dev *dev,
--
2.43.0