From: Bobby Eshleman <[email protected]> Some virtual devices like netkit (or ifb) never DMA and never touch frag contents, they just forward the skb to another device. They are unable to forward unreadable skbs, however, because they fail to pass TX validation checks on dev->netmem_tx. The existing two-state NETMEM_TX_NONE / NETMEM_TX_DMA doesn't give the TX validator enough information to differentiate devices that will attempt DMA on the unreadable skb from those that will simply route it untouched.
Add a third mode to the enum so drivers can indicate 1) if they have netmem TX support, and 2) if they do, whether they are DMA-capable: NETMEM_TX_NO_DMA - pass-through, device never DMAs Widen dev->netmem_tx from a 1-bit field to 2 bits to fit the new value, and declare netkit as NETMEM_TX_NO_DMA. Devmem TX support over these devices comes in a follow-up patch. Signed-off-by: Bobby Eshleman <[email protected]> --- Changes in v3: - net_cachelines/net_device.rst: align the netmem_tx row's type column with the rest of the table by using "unsigned_long:2" instead of "unsigned long:2" - Split this into a distinct patch (Jakub) --- Documentation/networking/net_cachelines/net_device.rst | 2 +- Documentation/networking/netmem.rst | 3 +++ Documentation/translations/zh_CN/networking/netmem.rst | 3 +++ drivers/net/netkit.c | 1 + include/linux/netdevice.h | 7 ++++--- 5 files changed, 12 insertions(+), 4 deletions(-) diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst index 1c19bb7705df..7b3392553fd6 100644 --- a/Documentation/networking/net_cachelines/net_device.rst +++ b/Documentation/networking/net_cachelines/net_device.rst @@ -10,7 +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 +unsigned_long:2 netmem_tx:2; read_mostly char name[16] struct netdev_name_node* name_node struct dev_ifalias* ifalias diff --git a/Documentation/networking/netmem.rst b/Documentation/networking/netmem.rst index 5ccadba4f373..217869d1108d 100644 --- a/Documentation/networking/netmem.rst +++ b/Documentation/networking/netmem.rst @@ -99,3 +99,6 @@ Driver TX Requirements appropriate mode: - `NETMEM_TX_DMA`: for physical devices that perform DMA. + + - `NETMEM_TX_NO_DMA`: for virtual or passthrough devices that do + not DMA, but still support handling of netmem-backed skbs. diff --git a/Documentation/translations/zh_CN/networking/netmem.rst b/Documentation/translations/zh_CN/networking/netmem.rst index 9c84423b7528..320f3eacf51b 100644 --- a/Documentation/translations/zh_CN/networking/netmem.rst +++ b/Documentation/translations/zh_CN/networking/netmem.rst @@ -92,3 +92,6 @@ dma-mapping API 去处理。 2. 驱动程序应将 `netdev->netmem_tx` 设置为适当的模式： - `NETMEM_TX_DMA`：适用于执行 DMA 的物理设备。 + + - `NETMEM_TX_NO_DMA`：适用于不执行 DMA 的虚拟或透传设备，但仍支持 + 处理 netmem 支持的 skb。 diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c index 5e2eecc3165d..0ad6a806d7d5 100644 --- a/drivers/net/netkit.c +++ b/drivers/net/netkit.c @@ -466,6 +466,7 @@ static void netkit_setup(struct net_device *dev) dev->priv_flags |= IFF_NO_QUEUE; dev->priv_flags |= IFF_DISABLE_NETPOLL; dev->lltx = true; + dev->netmem_tx = NETMEM_TX_NO_DMA; dev->netdev_ops = &netkit_netdev_ops; dev->ethtool_ops = &netkit_ethtool_ops; diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 580bccb118a0..11d68e75eb4f 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1791,6 +1791,7 @@ enum netdev_stat_type { enum netmem_tx_mode { NETMEM_TX_NONE, /* no netmem TX support */ NETMEM_TX_DMA, /* DMA-capable netmem TX (real HW) */ + NETMEM_TX_NO_DMA, /* no DMA, e.g. passthrough for virtual devs */ }; enum netdev_reg_state { @@ -1814,8 +1815,8 @@ 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 netmem TX mode (NETMEM_TX_NONE or - * NETMEM_TX_DMA). + * @netmem_tx: device netmem TX mode (NETMEM_TX_NONE, NETMEM_TX_DMA, + * or NETMEM_TX_NO_DMA). * * @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 @@ -2138,7 +2139,7 @@ struct net_device { struct_group(priv_flags_fast, unsigned long priv_flags:32; unsigned long lltx:1; - unsigned long netmem_tx:1; + unsigned long netmem_tx:2; ); const struct net_device_ops *netdev_ops; const struct header_ops *header_ops; -- 2.53.0-Meta
