netdev - [PATCH bpf-next v4 12/15] xsk: Add cb area to struct xdp_buff

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Date:   Mon, 12 Dec 2022 18:36:02 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org,
        "Toke Høiland-Jørgensen" <toke@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: [PATCH bpf-next v4 12/15] xsk: Add cb area to struct xdp_buff_xsk

From: Toke Høiland-Jørgensen <toke@...hat.com>

Add an area after the xdp_buff in struct xdp_buff_xsk that drivers can use
to stash extra information to use in metadata kfuncs. The maximum size of
24 bytes means the full xdp_buff_xsk structure will take up exactly two
cache lines (with the cb field spanning both). Also add a macro drivers can
use to check their own wrapping structs against the available size.

Cc: John Fastabend <john.fastabend@...il.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: Anatoly Burakov <anatoly.burakov@...el.com>
Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
Cc: Magnus Karlsson <magnus.karlsson@...il.com>
Cc: Maryam Tahhan <mtahhan@...hat.com>
Cc: xdp-hints@...-project.net
Cc: netdev@...r.kernel.org
Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
 include/net/xsk_buff_pool.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index f787c3f524b0..3e952e569418 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -19,8 +19,11 @@ struct xdp_sock;
 struct device;
 struct page;
 
+#define XSK_PRIV_MAX 24
+
 struct xdp_buff_xsk {
 	struct xdp_buff xdp;
+	u8 cb[XSK_PRIV_MAX];
 	dma_addr_t dma;
 	dma_addr_t frame_dma;
 	struct xsk_buff_pool *pool;
@@ -28,6 +31,8 @@ struct xdp_buff_xsk {
 	struct list_head free_list_node;
 };
 
+#define XSK_CHECK_PRIV_TYPE(t) BUILD_BUG_ON(sizeof(t) > offsetofend(struct xdp_buff_xsk, cb))
+
 struct xsk_dma_map {
 	dma_addr_t *dma_pages;
 	struct device *dev;
-- 
2.39.0.rc1.256.g54fd8350bd-goog