On Tue, Mar 02, 2021 at 10:13:21AM +0100, Daniel Borkmann wrote:
> On 3/2/21 9:05 AM, Björn Töpel wrote:
> > On 2021-03-01 17:10, Toke Høiland-Jørgensen wrote:
> > > Björn Töpel <bjorn.to...@gmail.com> writes:
> > > > From: Björn Töpel <bjorn.to...@intel.com>
> > > >
> > > > Now that the AF_XDP rings have load-acquire/store-release semantics,
> > > > move libbpf to that as well.
> > > >
> > > > The library-internal libbpf_smp_{load_acquire,store_release} are only
> > > > valid for 32-bit words on ARM64.
> > > >
> > > > Also, remove the barriers that are no longer in use.
> > >
> > > So what happens if an updated libbpf is paired with an older kernel (or
> > > vice versa)?
> >
> > "This is fine." ;-) This was briefly discussed in [1], outlined by the
> > previous commit!
> >
> > ...even on POWER.
>
> Could you put a summary or quote of that discussion on 'why it is okay and
> does not
> cause /forward or backward/ compat issues with user space' directly into
> patch 1's
> commit message?
>
> I feel just referring to a link is probably less suitable in this case as it
> should
> rather be part of the commit message that contains the justification on why
> it is
> waterproof - at least it feels that specific area may be a bit
> under-documented, so
> having it as direct part certainly doesn't hurt.
>
> Would also be great to get Will's ACK on that when you have a v2. :)
Please stick me on CC for that and I'll take a look as I've forgotten pretty
much everything about this since last time :)
Will
