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From:   Albert Huang <huangjie.albert@bytedance.com>
To:     davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com
Cc:     Albert Huang <huangjie.albert@bytedance.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@kernel.org>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Pavel Begunkov <asml.silence@gmail.com>,
        Yunsheng Lin <linyunsheng@huawei.com>,
        Kees Cook <keescook@chromium.org>,
        Richard Gobert <richardbgobert@gmail.com>,
        "open list:NETWORKING DRIVERS" <netdev@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:XDP (eXpress Data Path)" <bpf@vger.kernel.org>
Subject: [RFC v3 Optimizing veth xsk performance 2/9] xsk: add dma_check_skip for skipping dma check
Date:   Tue,  8 Aug 2023 11:19:06 +0800
Message-Id: <20230808031913.46965-3-huangjie.albert@bytedance.com>
In-Reply-To: <20230808031913.46965-1-huangjie.albert@bytedance.com>
References: <20230808031913.46965-1-huangjie.albert@bytedance.com>
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for the virtual net device such as veth, there is
no need to do dma check if we support zero copy.

add this flag after unaligned. beacause there is 4 bytes hole
pahole -V ./net/xdp/xsk_buff_pool.o:
-----------
...
	/* --- cacheline 3 boundary (192 bytes) --- */
	u32                        chunk_size;           /*   192     4 */
	u32                        frame_len;            /*   196     4 */
	u8                         cached_need_wakeup;   /*   200     1 */
	bool                       uses_need_wakeup;     /*   201     1 */
	bool                       dma_need_sync;        /*   202     1 */
	bool                       unaligned;            /*   203     1 */

	/* XXX 4 bytes hole, try to pack */

	void *                     addrs;                /*   208     8 */
	spinlock_t                 cq_lock;              /*   216     4 */
...
-----------

Signed-off-by: Albert Huang <huangjie.albert@bytedance.com>
---
 include/net/xsk_buff_pool.h | 1 +
 net/xdp/xsk_buff_pool.c     | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index b0bdff26fc88..fe31097dc11b 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -81,6 +81,7 @@ struct xsk_buff_pool {
 	bool uses_need_wakeup;
 	bool dma_need_sync;
 	bool unaligned;
+	bool dma_check_skip;
 	void *addrs;
 	/* Mutual exclusion of the completion ring in the SKB mode. Two cases to protect:
 	 * NAPI TX thread and sendmsg error paths in the SKB destructor callback and when
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index b3f7b310811e..ed251b8e8773 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -85,6 +85,7 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 		XDP_PACKET_HEADROOM;
 	pool->umem = umem;
 	pool->addrs = umem->addrs;
+	pool->dma_check_skip = false;
 	INIT_LIST_HEAD(&pool->free_list);
 	INIT_LIST_HEAD(&pool->xskb_list);
 	INIT_LIST_HEAD(&pool->xsk_tx_list);
@@ -202,7 +203,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 	if (err)
 		goto err_unreg_pool;
 
-	if (!pool->dma_pages) {
+	if (!pool->dma_pages && !pool->dma_check_skip) {
 		WARN(1, "Driver did not DMA map zero-copy buffers");
 		err = -EINVAL;
 		goto err_unreg_xsk;
-- 
2.20.1