netdev - [PATCH bpf-next] xsk: add multi-buffer support for sockets sharing umem

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Date: Thu,  7 Sep 2023 09:20:32 +0530
From: Tirthendu Sarkar <tirthendu.sarkar@...el.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	bjorn@...nel.org,
	magnus.karlsson@...el.com,
	maciej.fijalkowski@...el.com,
	jonathan.lemon@...il.com,
	davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	ast@...nel.org,
	daniel@...earbox.net
Subject: [PATCH bpf-next] xsk: add multi-buffer support for sockets sharing umem

Userspace applications indicate their multi-buffer capability to xsk
using XSK_USE_SG socket bind flag. For sockets using shared umem the
bind flag may contain XSK_USE_SG only for the first socket. For any
subsequent socket the only option supported is XDP_SHARED_UMEM.

Add option XDP_UMEM_SG_FLAG in umem config flags to store the
multi-buffer handling capability when indicated by XSK_USE_SG option in
bing flag by the first socket. Use this to derive multi-buffer capability
for subsequent sockets in xsk core.

Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@...el.com>
Fixes: 81470b5c3c66 ("xsk: introduce XSK_USE_SG bind flag for xsk socket")
---
 include/net/xdp_sock.h  | 2 ++
 net/xdp/xsk.c           | 2 +-
 net/xdp/xsk_buff_pool.c | 3 +++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 1617af380162..69b472604b86 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -14,6 +14,8 @@
 #include <linux/mm.h>
 #include <net/sock.h>
 
+#define XDP_UMEM_SG_FLAG (1 << 1)
+
 struct net_device;
 struct xsk_queue;
 struct xdp_buff;
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 55f8b9b0e06d..7482d0aca504 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -1228,7 +1228,7 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 
 	xs->dev = dev;
 	xs->zc = xs->umem->zc;
-	xs->sg = !!(flags & XDP_USE_SG);
+	xs->sg = !!(xs->umem->flags & XDP_UMEM_SG_FLAG);
 	xs->queue_id = qid;
 	xp_add_xsk(xs->pool, xs);
 
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index b3f7b310811e..49cb9f9a09be 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -170,6 +170,9 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 	if (err)
 		return err;
 
+	if (flags & XDP_USE_SG)
+		pool->umem->flags |= XDP_UMEM_SG_FLAG;
+
 	if (flags & XDP_USE_NEED_WAKEUP)
 		pool->uses_need_wakeup = true;
 	/* Tx needs to be explicitly woken up the first time.  Also
-- 
2.34.1