net: add helper to pre-check if PP for an Rx queue will be unreadable

mlx5 pokes into the rxq state to check if the queue has a memory
provider, and therefore whether it may produce unreadable mem.
Add a helper for doing this in the page pool API. fbnic will want
a similar thing (tho, for a slightly different reason).

Reviewed-by: Mina Almasry <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

···
 	bitmap_free(rq->mpwqe.shampo->bitmap);
 }
 
-static bool mlx5_rq_needs_separate_hd_pool(struct mlx5e_rq *rq)
-{
-	struct netdev_rx_queue *rxq = __netif_get_rx_queue(rq->netdev, rq->ix);
-
-	return !!rxq->mp_params.mp_ops;
-}
-
 static int mlx5_rq_shampo_alloc(struct mlx5_core_dev *mdev,
 				struct mlx5e_params *params,
 				struct mlx5e_rq_param *rqp,
···
 	hd_pool_size = (rq->mpwqe.shampo->hd_per_wqe * wq_size) /
 		MLX5E_SHAMPO_WQ_HEADER_PER_PAGE;
 
-	if (mlx5_rq_needs_separate_hd_pool(rq)) {
+	if (netif_rxq_has_unreadable_mp(rq->netdev, rq->ix)) {
 		/* Separate page pool for shampo headers */
 		struct page_pool_params pp_params = { };
 

include/net/netdev_queues.h

···
 							 int idx);
 };
 
+bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx);
+
 /**
  * DOC: Lockless queue stopping / waking helpers.
  *

include/net/page_pool/helpers.h

···
 		page_pool_update_nid(pool, new_nid);
 }
 
+/**
+ * page_pool_is_unreadable() - will allocated buffers be unreadable for the CPU
+ * @pool: queried page pool
+ *
+ * Check if page pool will return buffers which are unreadable to the CPU /
+ * kernel. This will only be the case if user space bound a memory provider (mp)
+ * which returns unreadable memory to the queue served by the page pool.
+ * If %PP_FLAG_ALLOW_UNREADABLE_NETMEM was set but there is no mp bound
+ * this helper will return false. See also netif_rxq_has_unreadable_mp().
+ *
+ * Return: true if memory allocated by the page pool may be unreadable
+ */
 static inline bool page_pool_is_unreadable(struct page_pool *pool)
 {
 	return !!pool->mp_ops;

net/core/netdev_rx_queue.c

···
 
 #include "page_pool_priv.h"
 
+/* See also page_pool_is_unreadable() */
+bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx)
+{
+	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, idx);
+
+	return !!rxq->mp_params.mp_ops;
+}
+EXPORT_SYMBOL(netif_rxq_has_unreadable_mp);
+
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
 	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);