Commit 383faec0 authored by Mina Almasry's avatar Mina Almasry Committed by Paolo Abeni
Browse files

net: enable driver support for netmem TX 



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: default avatarMina Almasry <almasrymina@google.com>
Acked-by: default avatarStanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-7-almasrymina@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 17af8cc0

Documentation/networking/net_cachelines/net_device.rst

+1 −0
Original line number Diff line number Diff line
@@ -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

Documentation/networking/netdev-features.rst

+5 −0
Original line number Diff line number Diff line
@@ -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

Documentation/networking/netmem.rst

+21 −2
Original line number Diff line number Diff line
@@ -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 +77,22 @@ 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. The Driver must not pass the netmem dma_addr to any of the dma-mapping APIs

   directly. This is because netmem dma_addrs may come from a source like

   dma-buf that is not compatible with the dma-mapping APIs.



   Helpers like netmem_dma_unmap_page_attrs() & netmem_dma_unmap_addr_set()

   should be used in lieu of dma_unmap_page[_attrs](), dma_unmap_addr_set().

   The netmem variants will handle netmem dma_addrs correctly regardless of the

   source, delegating to the dma-mapping APIs when appropriate.



   Not all dma-mapping APIs have netmem equivalents at the moment. If your

   driver relies on a missing netmem API, feel free to add and propose to

   netdev@, or reach out to the maintainers and/or almasrymina@google.com for

   help adding the netmem API.



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

include/linux/netdevice.h

+2 −0
Original line number Diff line number Diff line
@@ -1772,6 +1772,7 @@ 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
@@ -2087,6 +2088,7 @@ 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;

include/net/netmem.h

+20 −0
Original line number Diff line number Diff line
@@ -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>
@@ -276,4 +277,23 @@ static inline unsigned long netmem_get_dma_addr(netmem_ref netmem) 
void get_netmem(netmem_ref netmem);

void put_netmem(netmem_ref netmem);



#define netmem_dma_unmap_addr_set(NETMEM, PTR, ADDR_NAME, VAL)   \

	do {                                                     \

		if (!netmem_is_net_iov(NETMEM))                  \

			dma_unmap_addr_set(PTR, ADDR_NAME, VAL); \

		else                                             \

			dma_unmap_addr_set(PTR, ADDR_NAME, 0);   \

	} while (0)



static inline void netmem_dma_unmap_page_attrs(struct device *dev,

					       dma_addr_t addr, size_t size,

					       enum dma_data_direction dir,

					       unsigned long attrs)

{

	if (!addr)

		return;



	dma_unmap_page_attrs(dev, addr, size, dir, attrs);

}



#endif /* _NET_NETMEM_H */