[PATCH net-next v3 04/15] ibmveth: Refactor buffer pool management for per-queue MQ RX

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

This is the key memory-model change for MQ RX.

Legacy ibmveth uses five adapter-level RX buffer pools (512 B
through 64 KiB slots). pool_active[] enables the standard-MTU pools by
default; larger pools activate when MTU requires them. With single-queue
RX that set is shared on one completion path.

MQ requires the same pool model per queue: buffers post with
H_ADD_LOGICAL_LAN_BUFFERS_QUEUE against a queue handle and completions
return on that queue. Sharing pools across queues would mix ownership and
break queue-local replenish/drain/teardown.

Refactor around queue-local pools with static geometry (still defined at
probe on queue 0, copied to queues 1..N at alloc time):

  rx_buff_pool[queue][pool]
  ibmveth_alloc_queue_buffer_pools()
  ibmveth_free_queue_buffer_pools()
  ibmveth_alloc_buffer_pools() / ibmveth_free_buffer_pools()

Queue 0 remains the template for pool geometry (size, buff_size,
threshold, active). For queues 1..N we copy metadata from queue 0, then
allocate actual backing arrays/skbs per queue.

At the default 1500-byte MTU, pool 4 (64 KiB buffers) is not needed and
costs guest memory when allocated per queue in MQ mode. Clear
pool_active[4] so open() skips it; ibmveth_change_mtu() still enables
larger pools when MTU warrants jumbo frames.

Error handling is also made queue-safe:

  - if allocation fails in one pool, unwind only what was allocated for
    that queue, then unwind prior queues in the caller
  - free paths release pools based on real allocations
    (free_map/dma_addr/skbuff), not only pool->active

That allocation-based free check is intentional: later resize and failure
paths can leave memory allocated even when active was already cleared.
Freeing by allocation state avoids leaks and double-free corner cases.

This split keeps the per-queue pool design isolated and reviewable ahead
of the MQ datapath enable commit later in the series.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 127 +++++++++++++++++++++++++++++
 drivers/net/ethernet/ibm/ibmveth.h |   2 +-
 2 files changed, 128 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index b8adc9935471..95068fb20dba 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -611,6 +611,133 @@ static void ibmveth_free_buffer_pool(struct ibmveth_adapter *adapter,
 	}
 }
 
+/**
+ * ibmveth_alloc_queue_buffer_pools - Allocate buffer pools for a single queue
+ * @adapter: ibmveth adapter structure
+ * @queue: queue index
+ *
+ * Allocates all active buffer pools for the specified queue.
+ * Pool metadata must be initialized before calling this function.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int ibmveth_alloc_queue_buffer_pools(struct ibmveth_adapter *adapter,
+					    int queue)
+{
+	struct net_device *netdev = adapter->netdev;
+	int i;
+
+	for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) {
+		if (!adapter->rx_buff_pool[queue][i].active)
+			continue;
+
+		if (ibmveth_alloc_buffer_pool(&adapter->rx_buff_pool[queue][i])) {
+			netdev_err(netdev,
+				   "unable to allocate buffer pool %d for queue %d (size=%u, count=%u)\n",
+				   i, queue,
+				   adapter->rx_buff_pool[queue][i].buff_size,
+				   adapter->rx_buff_pool[queue][i].size);
+			adapter->rx_buff_pool[queue][i].active = 0;
+
+			/* Free pools allocated so far for this queue */
+			while (--i >= 0) {
+				if (adapter->rx_buff_pool[queue][i].active)
+					ibmveth_free_buffer_pool(adapter,
+								 &adapter->rx_buff_pool[queue][i]);
+			}
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * ibmveth_free_queue_buffer_pools - Free buffer pools for a single queue
+ * @adapter: ibmveth adapter structure
+ * @queue: queue index
+ *
+ * Frees all active buffer pools for the specified queue.
+ */
+static void ibmveth_free_queue_buffer_pools(struct ibmveth_adapter *adapter,
+					    int queue)
+{
+	int i;
+
+	for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) {
+		struct ibmveth_buff_pool *pool = &adapter->rx_buff_pool[queue][i];
+
+		/* Free pool if it has allocated memory, regardless of active flag.
+		 * Pools may have memory allocated but not marked active during
+		 * queue scale-up, so we must check for actual allocations.
+		 */
+		if (pool->free_map || pool->dma_addr || pool->skbuff)
+			ibmveth_free_buffer_pool(adapter, pool);
+	}
+}
+
+/**
+ * ibmveth_alloc_buffer_pools - Allocate buffer pools for all queues
+ * @adapter: ibmveth adapter structure
+ *
+ * Initializes pool metadata for queues 1-N from queue 0 settings,
+ * then allocates buffer pools for all queues using the helper function.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int __maybe_unused ibmveth_alloc_buffer_pools(struct ibmveth_adapter *adapter)
+{
+	struct net_device *netdev = adapter->netdev;
+	int i, q, rc;
+
+	/* Initialize pool metadata for queues 1-15 from queue 0 settings */
+	for (q = 1; q < adapter->num_rx_queues; q++) {
+		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[q][i];
+
+			dst->size = src->size;
+			dst->index = src->index;
+			dst->buff_size = src->buff_size;
+			dst->threshold = src->threshold;
+			dst->active = src->active;
+		}
+	}
+
+	/* Allocate actual buffers for all queues */
+	for (q = 0; q < adapter->num_rx_queues; q++) {
+		rc = ibmveth_alloc_queue_buffer_pools(adapter, q);
+		if (rc) {
+			/* Free pools for all previous queues */
+			while (--q >= 0)
+				ibmveth_free_queue_buffer_pools(adapter, q);
+			return rc;
+		}
+	}
+
+	netdev_dbg(netdev, "allocated buffer pools for %d queue(s)\n",
+		   adapter->num_rx_queues);
+	return 0;
+}
+
+/**
+ * ibmveth_free_buffer_pools - Free buffer pools for all queues
+ * @adapter: ibmveth adapter structure
+ *
+ * Frees buffer pools for all queues using the helper function.
+ */
+static void __maybe_unused ibmveth_free_buffer_pools(struct ibmveth_adapter *adapter)
+{
+	int q;
+
+	/* Free buffer pools for all queues */
+	for (q = 0; q < adapter->num_rx_queues; q++)
+		ibmveth_free_queue_buffer_pools(adapter, q);
+
+	netdev_dbg(adapter->netdev, "freed buffer pools for %d queue(s)\n",
+		   adapter->num_rx_queues);
+}
+
 /**
  * ibmveth_remove_buffer_from_pool - remove a buffer from a pool
  * @adapter: adapter instance
diff --git a/drivers/net/ethernet/ibm/ibmveth.h b/drivers/net/ethernet/ibm/ibmveth.h
index f0dffe42e8fe..d2ceeccd5fbd 100644
--- a/drivers/net/ethernet/ibm/ibmveth.h
+++ b/drivers/net/ethernet/ibm/ibmveth.h
@@ -286,7 +286,7 @@ static inline long h_illan_attributes(unsigned long unit_address,
 static int pool_size[] = { 512, 1024 * 2, 1024 * 16, 1024 * 32, 1024 * 64 };
 static int pool_count[] = { 256, 512, 256, 256, 256 };
 static int pool_count_cmo[] = { 256, 512, 256, 256, 64 };
-static int pool_active[] = { 1, 1, 0, 0, 1};
+static int pool_active[] = { 1, 1, 0, 0, 0};
 
 #define IBM_VETH_INVALID_MAP ((u16)0xffff)
 
-- 
2.39.3 (Apple Git-146)