Re: [PATCH net-next 2/2] net: stmmac: disable TX checksum offload for jumbo frames on bugged cores

[Jisheng Zhang <jszhang@kernel.org>]

On Tue, Oct 20, 2026 at 02:28:26PM +0200, Andrew Lunn wrote:
> > > Here I want to query a generic rule from netdev maintainers:
> > > can XDP frame enable HW checksum on dwmac IP? Per my understanding, the
> > > dwmac can only do HW checksum for normal particular packets layouts, such as
> > > TCP, UDP. What about if XDP transmits a non-IP frame?
> > 
> > or a generic XDP guide from netdev maintainers:
> > Since XDP can tranmist arbitrary Eth frames, so how does the eth driver cope
> > with HW checksum if the HW checksum is intended for supported IP packet
> > layouts rather than arbitrary layer2 frames?
> > 
> > choices:
> > c1. Simply disabled HW checksum by default. Then XDP prog must provide
> > checksums themselves, lost the HW offload cap for IP packets.
> > 
> > c2. detect the frame in eth driver's xdp code path, then enable/disable
> > HW checksum accordingly. Then how? Any example in exisiting eth drivers
> > is appreciated.
> 
> Why is this specific to XDP? Cannot the network stack transmit
> arbitrary layer2 frames? Isn't this a generic problem?
> 

network stack normal tx supplies the skb->ip_summed metadata, and
dwmac driver specifically can decide to enable/disable HW csum
by checking the protocol which is extraced from skb, example
stmmac_has_ip_ethertype()
But XDP path doesn't have the necessary metadata, and I'm not sure
whether stmmac_has_ip_ethertype xdb version can be implemented or
not. That's the reason I request generic XDP guidence from netdev
maintainers.

correct me if I misunderstood something.

Thanks