On Fri, May 19, 2017 at 08:21:47PM -0700, Jakub Kicinski wrote: > On Fri, 19 May 2017 20:07:52 -0700, Alexei Starovoitov wrote: > > How about exposing 'struct mlx5_cqe64 *' to XDP programs as-is? > > We can make sure that XDP program does read only access into it and > > it will see cqe->rss_hash_result, cqe->rss_hash_type and everything else > > in there, but this will not be uapi and it will be pretty obvious > > to program authors that their programs are vendor specific. > > 'not uapi' here means that mellanox is free to change their HW descriptor > > and its contents as they wish. > > Hm.. Would that mean we have to teach the verifier about all possible > drivers and their metadata structures (i.e. sizes thereof). And add an > UAPI enum of known drivers?
why? no uapi other than a pointer to this hw rx descriptor. Different sizeof(hw_rx_descriptor) is not a problem. We deal with it already in tracing. All tracepoints have different sizeof(*ctx), yet the safety is preserved. > Other idea I floated in early days was to standardize the fields but > let the driver "JIT" the accesses to look at the right offset of the > right structure. Admittedly that would be a lot more work. 'standardize the fields' sounds nice, but failed here already. As far as I can see the meaning of packet 'hash' is quite different across the drivers and 'hash' is just a beginning. I hope we can standardize on 'csum' field and make it checksum_complete, but so far out of 10+G nics only mlx5 and nfp do it in hw. We need it at least for mlx4, but it can only fake it via expensive math.
