netdev - [PATCH bpf-next 4/6] xsk: carry a copy of xdp_zc_max_segs within xsk_buff

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Message-Id: <20241002155441.253956-5-maciej.fijalkowski@intel.com>
Date: Wed,  2 Oct 2024 17:54:39 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: bpf@...r.kernel.org,
	ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org
Cc: netdev@...r.kernel.org,
	magnus.karlsson@...el.com,
	bjorn@...nel.org,
	maciej.fijalkowski@...el.com
Subject: [PATCH bpf-next 4/6] xsk: carry a copy of xdp_zc_max_segs within xsk_buff_pool

This so we avoid dereferencing struct net_device within hot path.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 include/net/xsk_buff_pool.h | 1 +
 net/xdp/xsk_buff_pool.c     | 1 +
 net/xdp/xsk_queue.h         | 2 +-
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index 468a23b1b4c5..8223581d95f8 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -77,6 +77,7 @@ struct xsk_buff_pool {
 	u32 chunk_shift;
 	u32 frame_len;
 	u8 tx_metadata_len; /* inherited from umem */
+	u32 xdp_zc_max_segs;
 	u8 cached_need_wakeup;
 	bool uses_need_wakeup;
 	bool unaligned;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 7ecd4ccd2473..e946ba4a5ccf 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -229,6 +229,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 		goto err_unreg_xsk;
 	}
 	pool->umem->zc = true;
+	pool->xdp_zc_max_segs = netdev->xdp_zc_max_segs;
 	return 0;
 
 err_unreg_xsk:
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 406b20dfee8d..46d87e961ad6 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -260,7 +260,7 @@ u32 xskq_cons_read_desc_batch(struct xsk_queue *q, struct xsk_buff_pool *pool,
 			nr_frags = 0;
 		} else {
 			nr_frags++;
-			if (nr_frags == pool->netdev->xdp_zc_max_segs) {
+			if (nr_frags == pool->xdp_zc_max_segs) {
 				nr_frags = 0;
 				break;
 			}
-- 
2.34.1