On Mon, Jun 08, 2020 at 06:51:12PM +0200, Jesper Dangaard Brouer wrote: > Make it easier to handle UAPI/kABI extensions by avoid BPF using/returning > file descriptor value zero. Use this in recent devmap extension to keep > older applications compatible with newer kernels. > > For special type maps (e.g. devmap and cpumap) the map-value data-layout is > a configuration interface. This is a kernel Application Binary Interface > (kABI) that can only be tail extended. Thus, new members (and thus features) > can only be added to the end of this structure, and the kernel uses the > map->value_size from userspace to determine feature set 'version'. please drop these kabi references. As far as I know kabi is a redhat invention and I'm not even sure what exactly it means. 'struct bpf_devmap_val' is uapi. No need to invent new names for existing concept. > The recent extension of devmap with a bpf_prog.fd requires end-user to > supply the file-descriptor value minus-1 to communicate that the features > isn't used. This isn't compatible with the described kABI extension model. non-zero prog_fd requirement exists already in bpf syscall. It's not recent. So I don't think patch 1 is appropriate at this point. Certainly not for bpf tree. We can argue about it usefulness when bpf-next reopens. For now I think patches 2 and 3 are good to go. Don't delete 'enum sk_action' in patch 2 though. The rest looks good to me. Thanks!
