netdev - [Intel-wired-lan][PATCH iwl-net] idpf: cap maximum Rx buffer size

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Message-Id: <20251103212036.2788093-1-joshua.a.hay@intel.com>
Date: Mon,  3 Nov 2025 13:20:36 -0800
From: Joshua Hay <joshua.a.hay@...el.com>
To: intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org,
	Joshua Hay <joshua.a.hay@...el.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Madhu Chittim <madhu.chittim@...el.com>
Subject: [Intel-wired-lan][PATCH iwl-net] idpf: cap maximum Rx buffer size

The HW only supports a maximum Rx buffer size of 16K-128. On systems
using large pages, the libeth logic can configure the buffer size to be
larger than this. The upper bound is PAGE_SIZE while the lower bound is
MTU rounded up to the nearest power of 2. For example, ARM systems with
a 64K page size and an mtu of 9000 will set the Rx buffer size to 16K,
which will cause the config Rx queues message to fail.

Initialize the bufq/fill queue buf_len field to the maximum supported
size. This will trigger the libeth logic to cap the maximum Rx buffer
size by reducing the upper bound.

Fixes: 74d1412ac8f37 ("idpf: use libeth Rx buffer management for payload buffer")
Signed-off-by: Joshua Hay <joshua.a.hay@...el.com>
Acked-by: Alexander Lobakin <aleksander.lobakin@...el.com>
Reviewed-by: Madhu Chittim <madhu.chittim@...el.com>
---
 drivers/net/ethernet/intel/idpf/idpf_txrx.c | 8 +++++---
 drivers/net/ethernet/intel/idpf/idpf_txrx.h | 1 +
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
index 828f7c444d30..dcdd4fef1c7a 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
@@ -695,9 +695,10 @@ static int idpf_rx_buf_alloc_singleq(struct idpf_rx_queue *rxq)
 static int idpf_rx_bufs_init_singleq(struct idpf_rx_queue *rxq)
 {
 	struct libeth_fq fq = {
-		.count	= rxq->desc_count,
-		.type	= LIBETH_FQE_MTU,
-		.nid	= idpf_q_vector_to_mem(rxq->q_vector),
+		.count		= rxq->desc_count,
+		.type		= LIBETH_FQE_MTU,
+		.buf_len	= IDPF_RX_MAX_BUF_SZ,
+		.nid		= idpf_q_vector_to_mem(rxq->q_vector),
 	};
 	int ret;
 
@@ -754,6 +755,7 @@ static int idpf_rx_bufs_init(struct idpf_buf_queue *bufq,
 		.truesize	= bufq->truesize,
 		.count		= bufq->desc_count,
 		.type		= type,
+		.buf_len	= IDPF_RX_MAX_BUF_SZ,
 		.hsplit		= idpf_queue_has(HSPLIT_EN, bufq),
 		.xdp		= idpf_xdp_enabled(bufq->q_vector->vport),
 		.nid		= idpf_q_vector_to_mem(bufq->q_vector),
diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.h b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
index 75b977094741..a1255099656f 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.h
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.h
@@ -101,6 +101,7 @@ do {								\
 		idx = 0;					\
 } while (0)
 
+#define IDPF_RX_MAX_BUF_SZ			(16384 - 128)
 #define IDPF_RX_BUF_STRIDE			32
 #define IDPF_RX_BUF_POST_STRIDE			16
 #define IDPF_LOW_WATERMARK			64
-- 
2.39.2