netdev - [PATCH net-next v2 10/14] net: add helper to pre-check if PP for an Rx queue will be unreadable

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Message-ID: <20250829012304.4146195-11-kuba@kernel.org>
Date: Thu, 28 Aug 2025 18:23:00 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	horms@...nel.org,
	almasrymina@...gle.com,
	tariqt@...dia.com,
	dtatulea@...dia.com,
	hawk@...nel.org,
	ilias.apalodimas@...aro.org,
	alexanderduyck@...com,
	sdf@...ichev.me,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next v2 10/14] 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).

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
v2:
 - make the helper an rxq helper rather than PP helper
v1: https://lore.kernel.org/20250820025704.166248-12-kuba@kernel.org
---
 include/net/netdev_queues.h                       |  2 ++
 include/net/page_pool/helpers.h                   | 12 ++++++++++++
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c |  9 +--------
 net/core/netdev_rx_queue.c                        |  9 +++++++++
 4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
index b9d02bc65c97..cd00e0406cf4 100644
--- a/include/net/netdev_queues.h
+++ b/include/net/netdev_queues.h
@@ -151,6 +151,8 @@ struct netdev_queue_mgmt_ops {
 							 int idx);
 };
 
+bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx);
+
 /**
  * DOC: Lockless queue stopping / waking helpers.
  *
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index aa3719f28216..3247026e096a 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -505,6 +505,18 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
 		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;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 0e48065a46eb..0633fe413e56 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -777,13 +777,6 @@ static void mlx5e_rq_shampo_hd_info_free(struct mlx5e_rq *rq)
 	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,
@@ -822,7 +815,7 @@ static int mlx5_rq_shampo_alloc(struct mlx5_core_dev *mdev,
 	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 = { };
 
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index 3bf1151d8061..c7d9341b7630 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -9,6 +9,15 @@
 
 #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);
-- 
2.51.0