Re: [PATCH RFC net-next v2 5/6] net: devmem: Implement TX path
From: Simon Horman <horms@kernel.org>
Date: 2025-01-31 09:09:35
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On Thu, Jan 30, 2025 at 09:15:38PM +0000, Mina Almasry wrote:
Augment dmabuf binding to be able to handle TX. Additional to all the RX binding, we also create tx_vec needed for the TX path. Provide API for sendmsg to be able to send dmabufs bound to this device: - Provide a new dmabuf_tx_cmsg which includes the dmabuf to send from. - MSG_ZEROCOPY with SCM_DEVMEM_DMABUF cmsg indicates send from dma-buf. Devmem is uncopyable, so piggyback off the existing MSG_ZEROCOPY implementation, while disabling instances where MSG_ZEROCOPY falls back to copying. We additionally pipe the binding down to the new zerocopy_fill_skb_from_devmem which fills a TX skb with net_iov netmems instead of the traditional page netmems. We also special case skb_frag_dma_map to return the dma-address of these dmabuf net_iovs instead of attempting to map pages. Based on work by Stanislav Fomichev [off-list ref]. A lot of the meat of the implementation came from devmem TCP RFC v1[1], which included the TX path, but Stan did all the rebasing on top of netmem/net_iov. Cc: Stanislav Fomichev <sdf@fomichev.me> Signed-off-by: Kaiyuan Zhang <redacted> Signed-off-by: Mina Almasry <redacted>
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quoted hunk ↗ jump to hunk
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
quoted hunk ↗ jump to hunk
index 0e41699df419..9ba6994e2a05 100644--- a/net/core/netdev-genl.c +++ b/net/core/netdev-genl.c
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quoted hunk ↗ jump to hunk
@@ -911,10 +912,68 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info) return err; } -/* stub */ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info) { - return 0; + struct net_devmem_dmabuf_binding *binding; + struct list_head *sock_binding_list; + struct net_device *netdev; + u32 ifindex, dmabuf_fd; + struct sk_buff *rsp; + int err = 0; + void *hdr; + + if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_DEV_IFINDEX) || + GENL_REQ_ATTR_CHECK(info, NETDEV_A_DMABUF_FD)) + return -EINVAL; + + ifindex = nla_get_u32(info->attrs[NETDEV_A_DEV_IFINDEX]); + dmabuf_fd = nla_get_u32(info->attrs[NETDEV_A_DMABUF_FD]); + + sock_binding_list = + genl_sk_priv_get(&netdev_nl_family, NETLINK_CB(skb).sk); + if (IS_ERR(sock_binding_list)) + return PTR_ERR(sock_binding_list); + + rsp = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL); + if (!rsp) + return -ENOMEM; + + hdr = genlmsg_iput(rsp, info); + if (!hdr) { + err = -EMSGSIZE; + goto err_genlmsg_free; + } + + rtnl_lock(); + + netdev = __dev_get_by_index(genl_info_net(info), ifindex); + if (!netdev || !netif_device_present(netdev)) { + err = -ENODEV; + goto err_unlock; + } + + binding = net_devmem_bind_dmabuf(netdev, DMA_TO_DEVICE, dmabuf_fd, + info->extack); + if (IS_ERR(binding)) { + err = PTR_ERR(binding); + goto err_unlock; + } + + list_add(&binding->list, sock_binding_list); + + nla_put_u32(rsp, NETDEV_A_DMABUF_ID, binding->id); + genlmsg_end(rsp, hdr); + + rtnl_unlock(); + + return genlmsg_reply(rsp, info); + + net_devmem_unbind_dmabuf(binding);
Hi Mina, It appears that the line above is unreachable. I guess it was part of an unwind that is no-longer needed and thus can now be removed. Flagged by Smatch.
+err_unlock: + rtnl_unlock(); +err_genlmsg_free: + nlmsg_free(rsp); + return err; }
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