diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index 8eceaa80b686..4f5fd5b99154 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst
@@ -76,6 +76,7 @@ unsigned_short dev_id
unsigned_short dev_port
spinlock_t addr_list_lock
int irq
+u32 netmem_tx_max_frag_size
struct netdev_hw_addr_list uc
struct netdev_hw_addr_list mc
struct netdev_hw_addr_list dev_addrs
diff --git a/Documentation/networking/netmem.rst b/Documentation/networking/netmem.rst
index 6871dcdd700c..04861c60cfa1 100644
--- a/Documentation/networking/netmem.rst
+++ b/Documentation/networking/netmem.rst
@@ -155,3 +155,9 @@ Driver TX Requirements
- `NETMEM_TX_NO_DMA`: for virtual or passthrough devices that do
not DMA, but still support handling of netmem-backed skbs.
+
+3. Drivers which limit the size of a single TX buffer should set
+ `netdev->netmem_tx_max_frag_size` to that limit. Devmem TX frags are
+ capped at it, otherwise a frag can span a whole net_iov, which may be
+ much larger than a page. The default is U32_MAX, the value is read when
+ the dmabuf binding is created.diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c0ae442c4344..4453b80bf7ea 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1845,6 +1845,7 @@ enum netdev_reg_state {
* drivers. Mainly used by logical interfaces, such as
* bonding and tunnels
* @netmem_tx: device netmem TX mode
+ * @netmem_tx_max_frag_size: max size of a netmem TX frag
* @pacing_offload: enable EDT pacing offload.
*
* @name: This is the first field of the "visible" part of this structure@@ -2342,6 +2343,7 @@ struct net_device {
unsigned short dev_port;
int irq;
u32 priv_len;
+ u32 netmem_tx_max_frag_size;
spinlock_t addr_list_lock;
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 489d92fe6dae..a8d3f87d38c5 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -734,6 +734,7 @@ zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from,
size = min_t(size_t, size, length);
size = min_t(size_t, size, iter_iov_len(from));
+ size = min_t(size_t, size, binding->tx_max_frag_size);
netmem_inc_ref(net_iov_to_netmem(niov));
skb_add_rx_frag_netmem(skb, i, net_iov_to_netmem(niov), off,
diff --git a/net/core/dev.c b/net/core/dev.c
index 3ac700d37e59..ba2f887dcd39 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -12350,6 +12350,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev->gro_ipv4_max_size = GRO_LEGACY_MAX_SIZE;
dev->tso_max_size = TSO_LEGACY_MAX_SIZE;
dev->tso_max_segs = TSO_MAX_SEGS;
+ dev->netmem_tx_max_frag_size = U32_MAX;
dev->upper_level = 1;
dev->lower_level = 1;
#ifdef CONFIG_LOCKDEP
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 6339f221bc82..19c039ed2cb2 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -218,6 +218,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
binding->dev = dev;
binding->vdev = vdev;
+ binding->tx_max_frag_size = dev->netmem_tx_max_frag_size;
write_pnet(&binding->net, sock_net(nl_sk));
binding->uid = sk_uid(nl_sk);
binding->niov_shift = niov_shift;
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 8fa089776610..97ff1f13fb84 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -79,6 +79,7 @@ struct net_devmem_dmabuf_binding {
struct net_iov **tx_vec;
unsigned int niov_shift;
+ u32 tx_max_frag_size;
struct work_struct unbind_w;
};--
2.53.0-Meta