[PATCH bpf-next v3 08/11] xsk: Add cb area to struct xdp_buff_xsk

From: Stanislav Fomichev <sdf@google.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
	john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"David Ahern" <dsahern@gmail.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Willem de Bruijn" <willemb@google.com>,
	"Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Anatoly Burakov" <anatoly.burakov@intel.com>,
	"Alexander Lobakin" <alexandr.lobakin@intel.com>,
	"Magnus Karlsson" <magnus.karlsson@gmail.com>,
	"Maryam Tahhan" <mtahhan@redhat.com>,
	xdp-hints@xdp-project.net, netdev@vger.kernel.org
Subject: [PATCH bpf-next v3 08/11] xsk: Add cb area to struct xdp_buff_xsk
Date: Tue, 29 Nov 2022 11:34:49 -0800	[thread overview]
Message-ID: <20221129193452.3448944-9-sdf@google.com> (raw)
In-Reply-To: <20221129193452.3448944-1-sdf@google.com>

From: Toke Høiland-Jørgensen <toke@redhat.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@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Anatoly Burakov <anatoly.burakov@intel.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
Cc: Maryam Tahhan <mtahhan@redhat.com>
Cc: xdp-hints@xdp-project.net
Cc: netdev@vger.kernel.org
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.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;
-- 
2.38.1.584.g0f3c55d4c2-goog

