On Mon, 21 Oct 2019 at 15:37, Björn Töpel <bjorn.to...@gmail.com> wrote: > > On Mon, 21 Oct 2019 at 14:19, Toke Høiland-Jørgensen <t...@redhat.com> wrote: > > > > Björn Töpel <bjorn.to...@gmail.com> writes: > > > [...] > > > > > > bpf_redirect_map() returns a 32-bit signed int, so the upper 32-bit > > > will need to be cleared. Having an explicit AND is one instruction > > > less than two shifts. So, it's an optimization (every instruction is > > > sacred). > > > > OIC. Well, a comment explaining that might be nice (since you're doing > > per-instruction comments anyway)? :) > > > > Sure, I can do a v3 with a comment, unless someone has a better idea > avoiding both shifts and AND. > > Thanks for taking a look! >
Now wait, there are the JMP32 instructions that Jiong added. So, shifts/AND can be avoided. Now, regarding backward compat... JMP32 is pretty new. I need to think a bit how to approach this. I mean, I'd like to be able to use new BPF instructions. Björn > > Björn > > > > -Toke > >
