netdev - [PATCH net-next v3 1/8] xsk: XDP_SETUP_XSK_POOL support option check

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Date:   Wed, 31 Mar 2021 15:11:32 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     netdev@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org,
        Dust Li <dust.li@...ux.alibaba.com>
Subject: [PATCH net-next v3 1/8] xsk: XDP_SETUP_XSK_POOL support option check_dma

The check_dma option is added to the bpf command. Because virtio-net
does not complete the dma initialization in advance. Instead, vring does
the dma operation every time data is sent.

Of course, in theory, it would be better to complete the dma
initialization in advance. But the modification vring may be more
troublesome, so here is an option to notify xsk dma whether the
initialization is complete. In this way, xsk will not report an error
because dma has not been initialized.

Of course, I still hope that virtio-net can support the completion of
dma operations in advance.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Reviewed-by: Dust Li <dust.li@...ux.alibaba.com>
---
 include/linux/netdevice.h | 1 +
 net/xdp/xsk_buff_pool.c   | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f57b70fc251f..47666b5d2dff 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -979,6 +979,7 @@ struct netdev_bpf {
 		struct {
 			struct xsk_buff_pool *pool;
 			u16 queue_id;
+			bool check_dma;
 		} xsk;
 	};
 };
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 8de01aaac4a0..4d3aed73ee3e 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -166,12 +166,13 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 	bpf.command = XDP_SETUP_XSK_POOL;
 	bpf.xsk.pool = pool;
 	bpf.xsk.queue_id = queue_id;
+	bpf.xsk.check_dma = true;
 
 	err = netdev->netdev_ops->ndo_bpf(netdev, &bpf);
 	if (err)
 		goto err_unreg_pool;
 
-	if (!pool->dma_pages) {
+	if (bpf.xsk.check_dma && !pool->dma_pages) {
 		WARN(1, "Driver did not DMA map zero-copy buffers");
 		err = -EINVAL;
 		goto err_unreg_xsk;
-- 
2.31.0