linux-kernel - [PATCH net-next v10 8/9] net: check for driver support in netmem TX

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Message-ID: <20250423031117.907681-9-almasrymina@google.com>
Date: Wed, 23 Apr 2025 03:11:15 +0000
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, io-uring@...r.kernel.org, 
	virtualization@...ts.linux.dev, kvm@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Cc: Mina Almasry <almasrymina@...gle.com>, Donald Hunter <donald.hunter@...il.com>, 
	Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Jeroen de Borst <jeroendb@...gle.com>, Harshitha Ramamurthy <hramamurthy@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, Willem de Bruijn <willemb@...gle.com>, Jens Axboe <axboe@...nel.dk>, 
	Pavel Begunkov <asml.silence@...il.com>, David Ahern <dsahern@...nel.org>, 
	Neal Cardwell <ncardwell@...gle.com>, Stefan Hajnoczi <stefanha@...hat.com>, 
	Stefano Garzarella <sgarzare@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	"Eugenio Pérez" <eperezma@...hat.com>, Shuah Khan <shuah@...nel.org>, sdf@...ichev.me, dw@...idwei.uk, 
	Jamal Hadi Salim <jhs@...atatu.com>, Victor Nogueira <victor@...atatu.com>, 
	Pedro Tammela <pctammela@...atatu.com>, Samiullah Khawaja <skhawaja@...gle.com>
Subject: [PATCH net-next v10 8/9] net: check for driver support in netmem TX

We should not enable netmem TX for drivers that don't declare support.

Check for driver netmem TX support during devmem TX binding and fail if
the driver does not have the functionality.

Check for driver support in validate_xmit_skb as well.

Signed-off-by: Mina Almasry <almasrymina@...gle.com>
Acked-by: Stanislav Fomichev <sdf@...ichev.me>

---

v8:
- Rebase on latest net-next and resolve conflict.
- Remove likely (Paolo)

v5: https://lore.kernel.org/netdev/20250227041209.2031104-8-almasrymina@google.com/
- Check that the dmabuf mappings belongs to the specific device the TX
  is being sent from (Jakub)

v4:
- New patch

---
 net/core/dev.c         | 34 ++++++++++++++++++++++++++++++++--
 net/core/devmem.h      |  6 ++++++
 net/core/netdev-genl.c |  7 +++++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index d1a8cad0c99c4..66f0c122de80e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3896,12 +3896,42 @@ int skb_csum_hwoffload_help(struct sk_buff *skb,
 }
 EXPORT_SYMBOL(skb_csum_hwoffload_help);
 
+static struct sk_buff *validate_xmit_unreadable_skb(struct sk_buff *skb,
+						    struct net_device *dev)
+{
+	struct skb_shared_info *shinfo;
+	struct net_iov *niov;
+
+	if (likely(skb_frags_readable(skb)))
+		goto out;
+
+	if (!dev->netmem_tx)
+		goto out_free;
+
+	shinfo = skb_shinfo(skb);
+
+	if (shinfo->nr_frags > 0) {
+		niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0]));
+		if (net_is_devmem_iov(niov) &&
+		    net_devmem_iov_binding(niov)->dev != dev)
+			goto out_free;
+	}
+
+out:
+	return skb;
+
+out_free:
+	kfree_skb(skb);
+	return NULL;
+}
+
 static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device *dev, bool *again)
 {
 	netdev_features_t features;
 
-	if (!skb_frags_readable(skb))
-		goto out_kfree_skb;
+	skb = validate_xmit_unreadable_skb(skb, dev);
+	if (unlikely(!skb))
+		goto out_null;
 
 	features = netif_skb_features(skb);
 	skb = validate_xmit_vlan(skb, features);
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 67168aae5e5b3..919e6ed28fdcd 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -229,6 +229,12 @@ net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding, size_t addr,
 {
 	return NULL;
 }
+
+static inline struct net_devmem_dmabuf_binding *
+net_devmem_iov_binding(const struct net_iov *niov)
+{
+	return NULL;
+}
 #endif
 
 #endif /* _NET_DEVMEM_H */
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 292606df834de..84c033574eb16 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -979,6 +979,13 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
 		goto err_unlock_netdev;
 	}
 
+	if (!netdev->netmem_tx) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Driver does not support netmem TX");
+		goto err_unlock_netdev;
+	}
+
 	binding = net_devmem_bind_dmabuf(netdev, DMA_TO_DEVICE, dmabuf_fd,
 					 info->extack);
 	if (IS_ERR(binding)) {
-- 
2.49.0.805.g082f7c87e0-goog