On Wed, 16 Jul 2025 13:17:53 +0200 Lorenzo Bianconi wrote: > > > I can't see what the non-redirected use-case could be. Can you please provide > > > more details? > > > Moreover, can it be solved without storing the rx_hash (or the other > > > hw-metadata) in a non-driver specific format? > > > > Having setters feels more generic than narrowly solving only the redirect, > > but I don't have a good use-case in mind. > > > > > Storing the hw-metadata in some of hw-specific format in xdp_frame will not > > > allow to consume them directly building the skb and we will require to decode > > > them again. What is the upside/use-case of this approach? (not considering the > > > orthogonality with the get method). > > > > If we add the store kfuncs to regular drivers, the metadata won't be stored > > in the xdp_frame; it will go into the rx descriptors so regular path that > > builds skbs will use it. > > IIUC, the described use-case would be to modify the hw metadata via a > 'setter' kfunc executed by an eBPF program bounded to the NIC and to store > the new metadata in the DMA descriptor in order to be consumed by the driver > codebase building the skb, right? > If so: > - we can get the same result just storing (running a kfunc) the modified hw > metadata in the xdp_buff struct using a well-known/generic layout and > consume it in the driver codebase (e.g. if the bounded eBPF program > returns XDP_PASS) using a generic xdp utility routine. This part is not in > the current series. > - Using this approach we are still not preserving the hw metadata if we pass > the xdp_frame to a remote CPU returning XDP_REDIRCT (we need to add more > code) > - I am not completely sure if can always modify the DMA descriptor directly > since it is DMA mapped. > > What do you think? FWIW I commented on an earlier revision to similar effect as Stanislav. To me the main concern is that we're adding another adhoc scheme, and are making xdp_frame grow into a para-skb. We added XDP to make raw packet access fast, now we're making drivers convert metadata twice :/
