[PATCH v1 16/18] ibmveth: Implement incremental MQ RX queue resize

[Mingming Cao <mmc@linux.ibm.com>]

Add ibmveth_resize_rx_queues_incremental() to grow or shrink
adapter->num_rx_queues while the netdev stays up.

Scale-up, per new queue index:
  alloc RX resources and per-queue pools
  register subordinate queue with PHYP
  request_irq(), then ibmveth_enable_irq(), then napi_enable
  update num_rx_queues, replenish new queues
  netif_set_real_num_rx_queues()

Scale-down disables NAPI on excess queues, drains pending buffers,
disables PHYP IRQ delivery and waits for in-flight handlers with
synchronize_irq() before lowering num_rx_queues, then tears down
IRQ/PHYP/memory.

Reject out-of-range new_count. On scale-down netif failure, re-enable
NAPI on queues not yet torn down. Refresh VIO CMO entitlement after a
successful resize when FW_FEATURE_CMO is enabled.

Scale-up rollback mirrors scale-down: drain posted buffers and wait for
in-flight handlers before deregistering with PHYP.

In replenish_task(), skip queues with queue_index >= num_rx_queues and
require pool->free_map before replenishing so in-flight handlers avoid
queues being torn down without clearing probe-time pool->active on free.

Queue 0 is never removed here. Scale-up failure unwinds only queues
added in this call. ethtool -L wiring is next.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 183 ++++++++++++++++++++++++++++-
 1 file changed, 178 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index cd0acd1715da..ac4d89a66a8d 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -945,18 +945,22 @@ static void ibmveth_replenish_task(struct ibmveth_adapter *adapter,
 	unsigned long flags;
 	int i;
 
-	if (queue_index >= adapter->num_rx_queues)
-		return;
-
 	adapter->replenish_task_cycles++;
 
+	if (queue_index >= adapter->num_rx_queues) {
+		netdev_dbg(adapter->netdev,
+			   "Skipping replenish for freed queue %d (num_queues=%d)\n",
+			   queue_index, adapter->num_rx_queues);
+		return;
+	}
+
 	spin_lock_irqsave(&rxq->replenish_lock, flags);
 
 	for (i = (IBMVETH_NUM_BUFF_POOLS - 1); i >= 0; i--) {
 		struct ibmveth_buff_pool *pool =
 			&adapter->rx_buff_pool[queue_index][i];
 
-		if (pool->active &&
+		if (pool->active && pool->free_map &&
 		    (atomic_read(&pool->available) < pool->threshold))
 			ibmveth_replenish_buffer_pool(adapter, pool,
 						      queue_index);
@@ -1682,7 +1686,7 @@ ibmveth_register_single_rx_queue(struct ibmveth_adapter *adapter,
  * the IRQ mapping for subordinate queues. Queue 0 is freed only through
  * ibmveth_free_all_queues() (H_FREE_LOGICAL_LAN).
  */
-static void __maybe_unused
+static void
 ibmveth_deregister_single_rx_queue(struct ibmveth_adapter *adapter,
 				   int queue_idx)
 {
@@ -1714,6 +1718,175 @@ ibmveth_deregister_single_rx_queue(struct ibmveth_adapter *adapter,
 	netdev_dbg(adapter->netdev, "Deregistered queue %d\n", queue_idx);
 }
 
+/**
+ * ibmveth_resize_rx_queues_incremental - Resize RX queue count incrementally
+ * @adapter: ibmveth adapter structure
+ * @new_count: Target number of RX queues
+ * @rxq_entries: Number of entries per RX queue
+ *
+ * Adds or removes RX queues without tearing down the entire adapter.
+ * Active queues continue receiving during scale-up; scale-down drains
+ * excess queues before deregistering them with the hypervisor.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int
+ibmveth_resize_rx_queues_incremental(struct ibmveth_adapter *adapter,
+				     int new_count, int rxq_entries)
+{
+	struct net_device *netdev = adapter->netdev;
+	u64 mac_address = ether_addr_to_u64(netdev->dev_addr);
+	int old_count = adapter->num_rx_queues;
+	int failed_queue;
+	int rc, i;
+
+	if (old_count == new_count) {
+		netdev_dbg(netdev, "RX queue count unchanged (%d), nothing to do\n",
+			   old_count);
+		return 0;
+	}
+
+	if (new_count < 1 || new_count > IBMVETH_MAX_RX_QUEUES) {
+		netdev_err(netdev, "Invalid RX queue count %d (must be 1-%d)\n",
+			   new_count, IBMVETH_MAX_RX_QUEUES);
+		return -EINVAL;
+	}
+
+	netdev_info(netdev, "Incrementally resizing RX queues: %d to %d\n",
+		    old_count, new_count);
+
+	if (new_count > old_count) {
+		netdev_dbg(netdev, "Scale-up: adding queues %d-%d\n",
+			   old_count, new_count - 1);
+
+		for (i = old_count; i < new_count; i++) {
+			rc = ibmveth_alloc_single_rx_queue(adapter, i, rxq_entries);
+			if (rc) {
+				netdev_err(netdev, "Failed to allocate queue %d: %d\n",
+					   i, rc);
+				goto cleanup_new_queues;
+			}
+
+			rc = ibmveth_register_single_rx_queue(adapter, i,
+							      mac_address);
+			if (rc) {
+				netdev_err(netdev, "Failed to register queue %d: %d\n",
+					   i, rc);
+				ibmveth_free_single_rx_queue(adapter, i);
+				goto cleanup_new_queues;
+			}
+
+			rc = ibmveth_setup_single_rx_interrupt(adapter, i);
+			if (rc) {
+				netdev_err(netdev,
+					   "Failed to setup IRQ for queue %d: %d\n",
+					   i, rc);
+				ibmveth_deregister_single_rx_queue(adapter, i);
+				ibmveth_free_single_rx_queue(adapter, i);
+				goto cleanup_new_queues;
+			}
+
+			rc = ibmveth_enable_irq(adapter, i);
+			if (rc) {
+				netdev_err(netdev,
+					   "Failed to enable IRQ for queue %d: %d\n",
+					   i, rc);
+				ibmveth_cleanup_single_rx_interrupt(adapter, i);
+				ibmveth_deregister_single_rx_queue(adapter, i);
+				ibmveth_free_single_rx_queue(adapter, i);
+				goto cleanup_new_queues;
+			}
+
+			napi_enable(&adapter->napi[i]);
+		}
+
+		adapter->num_rx_queues = new_count;
+
+		for (i = old_count; i < new_count; i++)
+			ibmveth_replenish_task(adapter, i);
+
+		rc = netif_set_real_num_rx_queues(netdev, new_count);
+		if (rc) {
+			netdev_err(netdev, "Failed to set real RX queues to %d: %d\n",
+				   new_count, rc);
+			goto cleanup_new_queues;
+		}
+	} else {
+		netdev_dbg(netdev, "Scale-down: removing queues %d-%d\n",
+			   new_count, old_count - 1);
+
+		for (i = new_count; i < old_count; i++)
+			napi_disable(&adapter->napi[i]);
+
+		for (i = new_count; i < old_count; i++)
+			ibmveth_drain_rx_queue(adapter, i);
+
+		synchronize_net();
+
+		rc = netif_set_real_num_rx_queues(netdev, new_count);
+		if (rc) {
+			netdev_err(netdev, "Failed to set real RX queues to %d: %d\n",
+				   new_count, rc);
+			for (i = new_count; i < old_count; i++)
+				napi_enable(&adapter->napi[i]);
+			return rc;
+		}
+
+		/* Disable hypervisor interrupts and wait for handlers to complete
+		 * before updating num_rx_queues.
+		 */
+		for (i = new_count; i < old_count; i++) {
+			ibmveth_disable_irq(adapter, i);
+			synchronize_irq(adapter->queue_irq[i]);
+		}
+
+		adapter->num_rx_queues = new_count;
+
+		for (i = new_count; i < old_count; i++) {
+			ibmveth_cleanup_single_rx_interrupt(adapter, i);
+			ibmveth_deregister_single_rx_queue(adapter, i);
+			ibmveth_free_single_rx_queue(adapter, i);
+		}
+	}
+
+	netdev_info(netdev, "Successfully resized to %d RX queues (incremental)\n",
+		    adapter->num_rx_queues);
+
+	if (firmware_has_feature(FW_FEATURE_CMO))
+		vio_cmo_set_dev_desired(adapter->vdev,
+					ibmveth_get_desired_dma(adapter->vdev));
+
+	return 0;
+
+cleanup_new_queues:
+	failed_queue = i;
+	netdev_err(netdev,
+		   "Scale-up failed at queue %d, cleaning up queues %d-%d\n",
+		   failed_queue, old_count, failed_queue - 1);
+	for (i = old_count; i < failed_queue; i++)
+		napi_disable(&adapter->napi[i]);
+
+	for (i = old_count; i < failed_queue; i++)
+		ibmveth_drain_rx_queue(adapter, i);
+
+	synchronize_net();
+
+	for (i = old_count; i < failed_queue; i++) {
+		ibmveth_disable_irq(adapter, i);
+		synchronize_irq(adapter->queue_irq[i]);
+	}
+
+	for (i = old_count; i < failed_queue; i++) {
+		ibmveth_cleanup_single_rx_interrupt(adapter, i);
+		ibmveth_deregister_single_rx_queue(adapter, i);
+		ibmveth_free_single_rx_queue(adapter, i);
+	}
+	adapter->num_rx_queues = old_count;
+	netdev_warn(netdev, "Keeping %d queues after scale-up failure\n",
+		    old_count);
+	return rc;
+}
+
 /**
  * ibmveth_free_all_queues - Free all RX queues at once
  * @adapter: ibmveth adapter structure
-- 
2.39.3 (Apple Git-146)