On Mon, 8 Jun 2020 18:34:10 -0700 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > 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. Sure I can call it UAPI. I was alluding to the difference between API and ABI, but it doesn't matter. For the record, Red Hat didn't invent ABI (Application Binary Interface): https://en.wikipedia.org/wiki/Application_binary_interface > > 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. Great. > Don't delete 'enum sk_action' in patch 2 though. Sorry, yes, that was a mistake. > The rest looks good to me. Thanks! -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
