Commit 75d9228982f2 for kernel

commit 75d9228982f23d68066ca0b7d87014c3eb8ddc85
Author: Larysa Zaremba <larysa.zaremba@intel.com>
Date:   Thu Mar 5 12:12:48 2026 +0100

    libeth, idpf: use truesize as XDP RxQ info frag_size

    The only user of frag_size field in XDP RxQ info is
    bpf_xdp_frags_increase_tail(). It clearly expects whole buffer size instead
    of DMA write size. Different assumptions in idpf driver configuration lead
    to negative tailroom.

    To make it worse, buffer sizes are not actually uniform in idpf when
    splitq is enabled, as there are several buffer queues, so rxq->rx_buf_size
    is meaningless in this case.

    Use truesize of the first bufq in AF_XDP ZC, as there is only one. Disable
    growing tail for regular splitq.

    Fixes: ac8a861f632e ("idpf: prepare structures to support XDP")
    Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
    Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
    Link: https://patch.msgid.link/20260305111253.2317394-8-larysa.zaremba@intel.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/intel/idpf/xdp.c b/drivers/net/ethernet/intel/idpf/xdp.c
index 6ac9c6624c2a..cbccd4546768 100644
--- a/drivers/net/ethernet/intel/idpf/xdp.c
+++ b/drivers/net/ethernet/intel/idpf/xdp.c
@@ -47,12 +47,16 @@ static int __idpf_xdp_rxq_info_init(struct idpf_rx_queue *rxq, void *arg)
 {
 	const struct idpf_vport *vport = rxq->q_vector->vport;
 	const struct idpf_q_vec_rsrc *rsrc;
+	u32 frag_size = 0;
 	bool split;
 	int err;

+	if (idpf_queue_has(XSK, rxq))
+		frag_size = rxq->bufq_sets[0].bufq.truesize;
+
 	err = __xdp_rxq_info_reg(&rxq->xdp_rxq, vport->netdev, rxq->idx,
 				 rxq->q_vector->napi.napi_id,
-				 rxq->rx_buf_size);
+				 frag_size);
 	if (err)
 		return err;

diff --git a/drivers/net/ethernet/intel/idpf/xsk.c b/drivers/net/ethernet/intel/idpf/xsk.c
index 676cbd80774d..d95d3efdfd36 100644
--- a/drivers/net/ethernet/intel/idpf/xsk.c
+++ b/drivers/net/ethernet/intel/idpf/xsk.c
@@ -403,6 +403,7 @@ int idpf_xskfq_init(struct idpf_buf_queue *bufq)
 	bufq->pending = fq.pending;
 	bufq->thresh = fq.thresh;
 	bufq->rx_buf_size = fq.buf_len;
+	bufq->truesize = fq.truesize;

 	if (!idpf_xskfq_refill(bufq))
 		netdev_err(bufq->pool->netdev,
diff --git a/drivers/net/ethernet/intel/libeth/xsk.c b/drivers/net/ethernet/intel/libeth/xsk.c
index 846e902e31b6..4882951d5c9c 100644
--- a/drivers/net/ethernet/intel/libeth/xsk.c
+++ b/drivers/net/ethernet/intel/libeth/xsk.c
@@ -167,6 +167,7 @@ int libeth_xskfq_create(struct libeth_xskfq *fq)
 	fq->pending = fq->count;
 	fq->thresh = libeth_xdp_queue_threshold(fq->count);
 	fq->buf_len = xsk_pool_get_rx_frame_size(fq->pool);
+	fq->truesize = xsk_pool_get_rx_frag_step(fq->pool);

 	return 0;
 }
diff --git a/include/net/libeth/xsk.h b/include/net/libeth/xsk.h
index 481a7b28e6f2..82b5d21aae87 100644
--- a/include/net/libeth/xsk.h
+++ b/include/net/libeth/xsk.h
@@ -597,6 +597,7 @@ __libeth_xsk_run_pass(struct libeth_xdp_buff *xdp,
  * @pending: current number of XSkFQEs to refill
  * @thresh: threshold below which the queue is refilled
  * @buf_len: HW-writeable length per each buffer
+ * @truesize: step between consecutive buffers, 0 if none exists
  * @nid: ID of the closest NUMA node with memory
  */
 struct libeth_xskfq {
@@ -614,6 +615,8 @@ struct libeth_xskfq {
 	u32			thresh;

 	u32			buf_len;
+	u32			truesize;
+
 	int			nid;
 };