Drivers need to make sure not to pass netmem dma-addrs to the
dma-mapping API in order to support netmem TX.

Add helpers and netmem_dma_*() helpers that enables special handling of
netmem dma-addrs that drivers can use.

Document in netmem.rst what drivers need to do to support netmem TX.

Signed-off-by: Mina Almasry <redacted>

---

v4:
- New patch
---
 .../networking/net_cachelines/net_device.rst  |  1 +
 Documentation/networking/netdev-features.rst  |  5 +++++
 Documentation/networking/netmem.rst           | 14 +++++++++++--
 include/linux/netdevice.h                     |  2 ++
 include/net/netmem.h                          | 20 +++++++++++++++++++
 5 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index 15e31ece675f..e3043b033647 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst

@@ -10,6 +10,7 @@ Type                                Name                        fastpath_tx_acce
 =================================== =========================== =================== =================== ===================================================================================
 unsigned_long:32                    priv_flags                  read_mostly                             __dev_queue_xmit(tx)
 unsigned_long:1                     lltx                        read_mostly                             HARD_TX_LOCK,HARD_TX_TRYLOCK,HARD_TX_UNLOCK(tx)
+unsigned long:1			    netmem_tx:1;	        read_mostly
 char                                name[16]
 struct netdev_name_node*            name_node
 struct dev_ifalias*                 ifalias

diff --git a/Documentation/networking/netdev-features.rst b/Documentation/networking/netdev-features.rst
index 5014f7cc1398..02bd7536fc0c 100644
--- a/Documentation/networking/netdev-features.rst
+++ b/Documentation/networking/netdev-features.rst

@@ -188,3 +188,8 @@ Redundancy) frames from one port to another in hardware.
 This should be set for devices which duplicate outgoing HSR (High-availability
 Seamless Redundancy) or PRP (Parallel Redundancy Protocol) tags automatically
 frames in hardware.
+
+* netmem-tx
+
+This should be set for devices which support netmem TX. See
+Documentation/networking/netmem.rst

diff --git a/Documentation/networking/netmem.rst b/Documentation/networking/netmem.rst
index 7de21ddb5412..43054d44c407 100644
--- a/Documentation/networking/netmem.rst
+++ b/Documentation/networking/netmem.rst

@@ -19,8 +19,8 @@ Benefits of Netmem :
 * Simplified Development: Drivers interact with a consistent API,
   regardless of the underlying memory implementation.
 
-Driver Requirements
-===================
+Driver RX Requirements
+======================
 
 1. The driver must support page_pool.
 

@@ -77,3 +77,13 @@ Driver Requirements
    that purpose, but be mindful that some netmem types might have longer
    circulation times, such as when userspace holds a reference in zerocopy
    scenarios.
+
+Driver TX Requirements
+======================
+
+1. Driver should use netmem_dma_unmap_page_attrs() in lieu of
+   dma_unmap_page[_attrs](), and netmem_dma_unmap_addr_set() in lieu of
+   dma_unmap_addr_set(). The netmem variants will handle netmems that should
+   not be dma-unmapped by the driver, such as dma-buf netmems.

+2. Driver should declare support by setting `netdev->netmem_tx = true`

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fccc03cd2164..d8cfd5d69ddf 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h

@@ -1753,6 +1753,7 @@ enum netdev_reg_state {
  *	@lltx:		device supports lockless Tx. Deprecated for real HW
  *			drivers. Mainly used by logical interfaces, such as
  *			bonding and tunnels
+ *	@netmem_tx:	device support netmem_tx.
  *
  *	@name:	This is the first field of the "visible" part of this structure
  *		(i.e. as seen by users in the "Space.c" file).  It is the name

@@ -2061,6 +2062,7 @@ struct net_device {
 	struct_group(priv_flags_fast,
 		unsigned long		priv_flags:32;
 		unsigned long		lltx:1;
+		unsigned long		netmem_tx:1;
 	);
 	const struct net_device_ops *netdev_ops;
 	const struct header_ops *header_ops;

diff --git a/include/net/netmem.h b/include/net/netmem.h
index a2148ffb203d..1fb39ad63290 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h

@@ -8,6 +8,7 @@
 #ifndef _NET_NETMEM_H
 #define _NET_NETMEM_H
 
+#include <linux/dma-mapping.h>
 #include <linux/mm.h>
 #include <net/net_debug.h>
 

@@ -267,4 +268,23 @@ static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
 void get_netmem(netmem_ref netmem);
 void put_netmem(netmem_ref netmem);