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Message-ID: <Z7d-7P8kPthyr3bG@mini-arch>
Date: Thu, 20 Feb 2025 11:13:48 -0800
From: Stanislav Fomichev <stfomichev@...il.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, virtualization@...ts.linux.dev,
kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>,
Donald Hunter <donald.hunter@...il.com>,
Jonathan Corbet <corbet@....net>,
Andrew Lunn <andrew+netdev@...n.ch>,
Jeroen de Borst <jeroendb@...gle.com>,
Praveen Kaligineedi <pkaligineedi@...gle.com>,
Shailend Chand <shailend@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>,
Willem de Bruijn <willemb@...gle.com>,
David Ahern <dsahern@...nel.org>,
Neal Cardwell <ncardwell@...gle.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
Eugenio Pérez <eperezma@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>,
Stefano Garzarella <sgarzare@...hat.com>,
Shuah Khan <shuah@...nel.org>, sdf@...ichev.me,
asml.silence@...il.com, 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: Re: [PATCH net-next v4 6/9] net: enable driver support for netmem TX
On 02/20, Mina Almasry wrote:
> 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 <almasrymina@...gle.com>
>
> ---
>
> 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.
Not all drivers use dma_unmap_addr_xxx APIs (looking at mlx5). Might
be worth mentioning that for the drivers managing the mappings
differently, care might be taken to not unmap 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);
>
[..]
> +#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)
Any reason not do to static inline instaed?
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