On 12/7/20 1:52 PM, John Fastabend wrote: >> >> I think we need to keep XDP_TX action separate, because I think that >> there are use-cases where the we want to disable XDP_TX due to end-user >> policy or hardware limitations. > > How about we discover this at load time though. Meaning if the program > doesn't use XDP_TX then the hardware can skip resource allocations for > it. I think we could have verifier or extra pass discover the use of > XDP_TX and then pass a bit down to driver to enable/disable TX caps. >
This was discussed in the context of virtio_net some months back - it is hard to impossible to know a program will not return XDP_TX (e.g., value comes from a map). Flipping that around, what if the program attach indicates whether XDP_TX could be returned. If so, driver manages the resource needs. If not, no resource needed and if the program violates that and returns XDP_TX the packet is dropped.
