From 6ce2bb048055ee599c0f35f1a90ff5db29ba5d65 Mon Sep 17 00:00:00 2001 From: Bobby Eshleman Date: Thu, 14 May 2026 10:22:29 -0700 Subject: net: netkit: declare NETMEM_TX_NO_DMA mode 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. Acked-by: Stanislav Fomichev Signed-off-by: Bobby Eshleman Link: https://patch.msgid.link/20260514-tcp-dm-netkit-v5-2-408c59b91e66@meta.com Signed-off-by: Jakub Kicinski --- drivers/net/netkit.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers') 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; -- cgit v1.2.3