[PATCH net-next v4 12/14] ibmveth: Implement incremental MQ RX queue resize

@@ -651,6 +651,58 @@ ibmveth_cleanup_rx_interrupts(struct ibmveth_adapter *adapter)
 	/* Queue 0 uses netdev->irq; leave queue_irq[0] for next open. */
 }
 
+/**
+ * ibmveth_setup_single_rx_interrupt - Setup interrupt for a single RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_idx: Queue index to setup
+ *
+ * Registers the IRQ handler for one queue. Used during incremental
+ * scale-up when adding new RX queues. The caller publishes the queue,
+ * replenishes buffers, enables NAPI, then unmasks PHYP delivery.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int
+ibmveth_setup_single_rx_interrupt(struct ibmveth_adapter *adapter,
+				  int queue_idx)
+{
+	struct net_device *netdev = adapter->netdev;
+	int rc;
+
+	rc = request_irq(adapter->queue_irq[queue_idx], ibmveth_interrupt,
+			 0, netdev->name, &adapter->napi[queue_idx]);
+	if (rc) {
+		netdev_err(netdev, "request_irq() failed for queue %d: %d\n",
+			   queue_idx, rc);
+		return rc;
+	}
+
+	netdev_dbg(netdev, "Setup IRQ %d for queue %d\n",
+		   adapter->queue_irq[queue_idx], queue_idx);
+	return 0;
+}
+
+/**
+ * ibmveth_cleanup_single_rx_interrupt - Cleanup interrupt for a single RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_idx: Queue index to cleanup
+ *
+ * Frees the IRQ handler for one queue and releases the subordinate virq
+ * mapping. Used during incremental scale-down.
+ */
+static void
+ibmveth_cleanup_single_rx_interrupt(struct ibmveth_adapter *adapter,
+				    int queue_idx)
+{
+	if (adapter->queue_irq[queue_idx]) {
+		free_irq(adapter->queue_irq[queue_idx],
+			 &adapter->napi[queue_idx]);
+		ibmveth_dispose_subordinate_irq_mapping(adapter, queue_idx);
+		netdev_dbg(adapter->netdev,
+			   "Freed IRQ for queue %d\n", queue_idx);
+	}
+}
+
 /**
  * ibmveth_schedule_rx_queue - Mask PHYP IRQ and schedule NAPI for one RX queue
  * @adapter: ibmveth adapter structure

@@ -1189,6 +1241,141 @@ ibmveth_free_buffer_pools(struct ibmveth_adapter *adapter)
 		   adapter->num_rx_queues);
 }
 
+/**
+ * ibmveth_alloc_single_rx_queue - Allocate resources for a single RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_idx: Queue index to allocate
+ * @rxq_entries: Number of RX queue entries
+ *
+ * Allocates buffer list, RX queue, and per-queue buffer pools for one queue.
+ * Used during incremental scale-up without affecting existing queues.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int
+ibmveth_alloc_single_rx_queue(struct ibmveth_adapter *adapter, int queue_idx,
+			      int rxq_entries)
+{
+	struct device *dev = &adapter->vdev->dev;
+	struct net_device *netdev = adapter->netdev;
+	int i, rc = -ENOMEM;
+
+	adapter->buffer_list_addr[queue_idx] =
+		(void *)get_zeroed_page(GFP_KERNEL);
+	if (!adapter->buffer_list_addr[queue_idx]) {
+		netdev_err(netdev, "unable to allocate buffer list for queue %d\n",
+			   queue_idx);
+		return -ENOMEM;
+	}
+
+	adapter->rx_queue[queue_idx].queue_len =
+		sizeof(struct ibmveth_rx_q_entry) * rxq_entries;
+	adapter->rx_queue[queue_idx].queue_addr =
+		dma_alloc_coherent(dev, adapter->rx_queue[queue_idx].queue_len,
+				   &adapter->rx_queue[queue_idx].queue_dma,
+				   GFP_KERNEL);
+	if (!adapter->rx_queue[queue_idx].queue_addr) {
+		netdev_err(netdev, "unable to allocate RX queue for queue %d\n",
+			   queue_idx);
+		goto out_free_buflist;
+	}
+
+	adapter->buffer_list_dma[queue_idx] =
+		dma_map_single(dev, adapter->buffer_list_addr[queue_idx],
+			       4096, DMA_BIDIRECTIONAL);
+	if (dma_mapping_error(dev, adapter->buffer_list_dma[queue_idx])) {
+		netdev_err(netdev, "unable to map buffer list for queue %d\n",
+			   queue_idx);
+		goto out_free_rxq;
+	}
+
+	for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) {
+		struct ibmveth_buff_pool *src =
+			&adapter->rx_buff_pool[0][i];
+		struct ibmveth_buff_pool *dst =
+			&adapter->rx_buff_pool[queue_idx][i];
+
+		dst->size = src->size;
+		dst->index = src->index;
+		dst->buff_size = src->buff_size;
+		dst->threshold = src->threshold;
+		dst->active = src->active;
+	}
+
+	rc = ibmveth_alloc_queue_buffer_pools(adapter, queue_idx);
+	if (rc) {
+		netdev_err(netdev,
+			   "Failed to allocate buffer pools for queue %d\n",
+			   queue_idx);
+		goto out_unmap_buflist;
+	}
+
+	adapter->rx_queue[queue_idx].index = 0;
+	adapter->rx_queue[queue_idx].num_slots = rxq_entries;
+	adapter->rx_queue[queue_idx].toggle = 1;
+	spin_lock_init(&adapter->rx_queue[queue_idx].replenish_lock);
+
+	netdev_dbg(netdev,
+		   "Allocated queue %d: buffer_list @ %p (DMA: 0x%llx), rx_queue @ %p (DMA: 0x%llx), %d entries\n",
+		   queue_idx, adapter->buffer_list_addr[queue_idx],
+		   (unsigned long long)adapter->buffer_list_dma[queue_idx],
+		   adapter->rx_queue[queue_idx].queue_addr,
+		   (unsigned long long)adapter->rx_queue[queue_idx].queue_dma,
+		   rxq_entries);
+
+	return 0;
+
+out_unmap_buflist:
+	dma_unmap_single(dev, adapter->buffer_list_dma[queue_idx],
+			 4096, DMA_BIDIRECTIONAL);
+	adapter->buffer_list_dma[queue_idx] = 0;
+out_free_rxq:
+	dma_free_coherent(dev, adapter->rx_queue[queue_idx].queue_len,
+			  adapter->rx_queue[queue_idx].queue_addr,
+			  adapter->rx_queue[queue_idx].queue_dma);
+	adapter->rx_queue[queue_idx].queue_addr = NULL;
+out_free_buflist:
+	free_page((unsigned long)adapter->buffer_list_addr[queue_idx]);
+	adapter->buffer_list_addr[queue_idx] = NULL;
+	return rc;
+}
+
+/**
+ * ibmveth_free_single_rx_queue - Free resources for a single RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_idx: Queue index to free
+ *
+ * Frees buffer list, RX queue, and per-queue buffer pools for one queue.
+ * Used during incremental scale-down without affecting remaining queues.
+ */
+static void
+ibmveth_free_single_rx_queue(struct ibmveth_adapter *adapter, int queue_idx)
+{
+	struct device *dev = &adapter->vdev->dev;
+
+	ibmveth_free_queue_buffer_pools(adapter, queue_idx);
+
+	if (adapter->buffer_list_dma[queue_idx]) {
+		dma_unmap_single(dev, adapter->buffer_list_dma[queue_idx],
+				 4096, DMA_BIDIRECTIONAL);
+		adapter->buffer_list_dma[queue_idx] = 0;
+	}
+
+	if (adapter->rx_queue[queue_idx].queue_addr) {
+		dma_free_coherent(dev, adapter->rx_queue[queue_idx].queue_len,
+				  adapter->rx_queue[queue_idx].queue_addr,
+				  adapter->rx_queue[queue_idx].queue_dma);
+		adapter->rx_queue[queue_idx].queue_addr = NULL;
+	}
+
+	if (adapter->buffer_list_addr[queue_idx]) {
+		free_page((unsigned long)adapter->buffer_list_addr[queue_idx]);
+		adapter->buffer_list_addr[queue_idx] = NULL;
+	}
+
+	netdev_dbg(adapter->netdev, "Freed queue %d resources\n", queue_idx);
+}
+
 /**
  * ibmveth_remove_buffer_from_pool - remove a buffer from a pool
  * @adapter: adapter instance

@@ -1307,6 +1494,51 @@ static int ibmveth_rxq_harvest_buffer(struct ibmveth_adapter *adapter,
 	return 0;
 }
 
+/**
+ * ibmveth_drain_rx_queue - Drain pending buffers from an RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_index: Queue index to drain
+ *
+ * Recycles all pending buffers back to the per-queue buffer pools.
+ * Must be called with NAPI disabled for this queue.
+ *
+ * Return: Number of buffers drained
+ */
+static int
+ibmveth_drain_rx_queue(struct ibmveth_adapter *adapter, int queue_index)
+{
+	struct net_device *netdev = adapter->netdev;
+	int drained = 0;
+	int limit = adapter->rx_queue[queue_index].num_slots;
+	int rc;
+
+	netdev_dbg(netdev, "Draining RX queue %d (limit: %d slots)\n",
+		   queue_index, limit);
+
+	while (drained < limit &&
+	       ibmveth_rxq_pending_buffer(adapter, queue_index)) {
+		/* Match poll-side order before harvesting completion state. */
+		smp_rmb();
+		rc = ibmveth_rxq_harvest_buffer(adapter, queue_index, true);
+		if (rc) {
+			netdev_err(netdev,
+				   "Failed to harvest buffer from queue %d during drain: %d\n",
+				   queue_index, rc);
+			break;
+		}
+		drained++;
+	}
+
+	if (drained > 0)
+		netdev_dbg(netdev, "Drained %d buffer(s) from RX queue %d\n",
+			   drained, queue_index);
+	else
+		netdev_dbg(netdev, "No buffers to drain from RX queue %d\n",
+			   queue_index);
+
+	return drained;
+}
+
 static void ibmveth_free_tx_ltb(struct ibmveth_adapter *adapter, int idx)
 {
 	if (!adapter->tx_ltb_ptr[idx])

@@ -1562,6 +1794,227 @@ ibmveth_register_single_rx_queue(struct ibmveth_adapter *adapter,
 	return 0;
 }
 
+/**
+ * ibmveth_deregister_single_rx_queue - Deregister one subordinate RX queue
+ * @adapter: ibmveth adapter structure
+ * @queue_idx: Queue index to deregister (1..N)
+ *
+ * Deregisters a single queue via H_FREE_LOGICAL_LAN_QUEUE. Linux IRQ handler
+ * teardown and subordinate virq mapping disposal are owned by interrupt
+ * cleanup helpers; queue 0 is freed only through ibmveth_free_all_queues()
+ * (H_FREE_LOGICAL_LAN).
+ */
+static void
+ibmveth_deregister_single_rx_queue(struct ibmveth_adapter *adapter,
+				   int queue_idx)
+{
+	unsigned long lpar_rc;
+	unsigned long ua = adapter->vdev->unit_address;
+	unsigned long qh = adapter->queue_handle[queue_idx];
+
+	if (!qh)
+		return;
+
+	do {
+		lpar_rc = h_free_logical_lan_queue(ua, qh);
+	} while (H_IS_LONG_BUSY(lpar_rc) || (lpar_rc == H_BUSY));
+
+	adapter->hcall_stats.free_lan_queue++;
+
+	if (lpar_rc != H_SUCCESS) {
+		netdev_err(adapter->netdev,
+			   "h_free_logical_lan_queue failed for queue %d: rc=0x%lx\n",
+			   queue_idx, lpar_rc);
+	}
+
+	adapter->queue_handle[queue_idx] = 0;
+
+	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);
+				/* request_irq failed: mapped but no handler */
+				ibmveth_dispose_subordinate_irq_mapping(adapter,
+									i);
+				ibmveth_deregister_single_rx_queue(adapter, i);
+				ibmveth_free_single_rx_queue(adapter, i);
+				goto cleanup_new_queues;
+			}
+
+			/*
+			 * Fully ready before PHYP delivery, matching open():
+			 * publish -> replenish -> napi_enable -> enable_irq.
+			 * That way ibmveth_interrupt() cannot run on an
+			 * unpublished, empty, or NAPI-disabled queue.
+			 */
+			adapter->num_rx_queues = i + 1;
+			ibmveth_replenish_task(adapter, i);
+			napi_enable(&adapter->napi[i]);
+
+			rc = ibmveth_enable_irq(adapter, i);
+			if (rc) {
+				netdev_err(netdev,
+					   "Failed to enable IRQ for queue %d: %d\n",
+					   i, rc);
+				adapter->num_rx_queues = i;
+				napi_disable(&adapter->napi[i]);
+				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;
+			}
+		}
+
+		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);
+
+		/*
+		 * Mask PHYP delivery before napi_disable/drain. Otherwise
+		 * ibmveth_interrupt returns IRQ_HANDLED without masking when
+		 * NAPI is disabled, and the HV can storm during drain.
+		 */
+		for (i = new_count; i < old_count; i++) {
+			ibmveth_disable_irq(adapter, i);
+			synchronize_irq(adapter->queue_irq[i]);
+		}
+
+		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++) {
+				ibmveth_replenish_task(adapter, i);
+				napi_enable(&adapter->napi[i]);
+				ibmveth_enable_irq(adapter, i);
+			}
+			return rc;
+		}
+
+		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++) {
+		ibmveth_disable_irq(adapter, i);
+		synchronize_irq(adapter->queue_irq[i]);
+	}
+
+	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_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

@@ -2217,12 +2670,62 @@ static void ibmveth_get_channels(struct net_device *netdev,
 	channels->rx_count = adapter->num_rx_queues;
 }
 
+/**
+ * ibmveth_resize_rx_channels - Validate and apply a new RX queue count
+ * @adapter: ibmveth adapter structure
+ * @goal_rx: desired RX queue count
+ *
+ * When the interface is up, resize live queues via
+ * ibmveth_resize_rx_queues_incremental(). When down, only stash
+ * adapter->num_rx_queues for the next open().
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int ibmveth_resize_rx_channels(struct ibmveth_adapter *adapter,
+				      unsigned int goal_rx)
+{
+	struct net_device *netdev = adapter->netdev;
+	unsigned int old_rx = adapter->num_rx_queues;
+	int rxq_entries;
+	int rc;
+
+	if (goal_rx > 1 && !adapter->multi_queue) {
+		netdev_err(netdev,
+			   "Cannot resize to %u RX queues: multi-queue mode not supported by firmware\n",
+			   goal_rx);
+		return -EOPNOTSUPP;
+	}
+
+	if (goal_rx < 1 || goal_rx > IBMVETH_MAX_RX_QUEUES) {
+		netdev_err(netdev,
+			   "Invalid RX queue count %u (must be 1-%d)\n",
+			   goal_rx, IBMVETH_MAX_RX_QUEUES);
+		return -EINVAL;
+	}
+
+	if (goal_rx == old_rx)
+		return 0;
+
+	if (!(netdev->flags & IFF_UP)) {
+		adapter->num_rx_queues = goal_rx;
+		return 0;
+	}
+
+	rxq_entries = adapter->rx_queue[0].num_slots;
+	rc = ibmveth_resize_rx_queues_incremental(adapter, goal_rx,
+						  rxq_entries);
+	if (rc)
+		netdev_err(netdev, "Failed to resize RX queues: %d\n", rc);
+	return rc;
+}
+
 static int ibmveth_set_channels(struct net_device *netdev,
 				struct ethtool_channels *channels)
 {
 	struct ibmveth_adapter *adapter = netdev_priv(netdev);
 	unsigned int old = netdev->real_num_tx_queues,
 		     goal = channels->tx_count;
+	unsigned int goal_rx = channels->rx_count;
 	int rc, i;
 
 	/* If ndo_open has not been called yet then don't allocate, just set

@@ -2231,6 +2734,13 @@ static int ibmveth_set_channels(struct net_device *netdev,
 	if (!(netdev->flags & IFF_UP))
 		return netif_set_real_num_tx_queues(netdev, goal);
 
+	/* Resize RX first while UP so ibmveth_resize_rx_channels() is used
+	 * in this patch. !IFF_UP RX stash ordering lands next.
+	 */
+	rc = ibmveth_resize_rx_channels(adapter, goal_rx);
+	if (rc)
+		return rc;
+
 	/* We have IBMVETH_MAX_QUEUES netdev_queue's allocated
 	 * but we may need to alloc/free the ltb's.
 	 */

@@ -2245,7 +2755,6 @@ static int ibmveth_set_channels(struct net_device *netdev,
 		if (!rc)
 			continue;
 
-		/* if something goes wrong, free everything we just allocated */
 		netdev_err(netdev, "Failed to allocate more tx queues, returning to %d queues\n",
 			   old);
 		goal = old;

@@ -2259,7 +2768,6 @@ static int ibmveth_set_channels(struct net_device *netdev,
 		goal = old;
 		old = i;
 	}
-	/* Free any that are no longer needed */
 	for (i = old; i > goal; i--) {
 		if (adapter->tx_ltb_ptr[i - 1])
 			ibmveth_free_tx_ltb(adapter, i - 1);