From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: "Jiri Olsa" <jolsa@redhat.com>,
"Björn Töpel" <bjorn.topel@gmail.com>,
"Magnus Karlsson" <magnus.karlsson@gmail.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Network Development" <netdev@vger.kernel.org>,
"Jonathan Lemon" <jonathan.lemon@gmail.com>,
bpf <bpf@vger.kernel.org>,
degeneloy@gmail.com, "John Fastabend" <john.fastabend@gmail.com>
Subject: Re: [PATCH bpf-next v3] libbpf: fix compatibility for kernels without need_wakeup
Date: Fri, 1 Nov 2019 13:41:23 -0700 [thread overview]
Message-ID: <CAADnVQJJcx8NszLBMSN0wiR43UEgGki38u0etnWvpMVG=8+ngg@mail.gmail.com> (raw)
In-Reply-To: <87bltvmlsr.fsf@toke.dk>
On Fri, Nov 1, 2019 at 12:36 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> > On Fri, Nov 1, 2019 at 12:27 AM Jiri Olsa <jolsa@redhat.com> wrote:
> >>
> >> On Thu, Oct 31, 2019 at 01:39:12PM -0700, Alexei Starovoitov wrote:
> >> > On Thu, Oct 31, 2019 at 12:18 PM Jiri Olsa <jolsa@redhat.com> wrote:
> >> > > >
> >> > > > yes. older vmlinux and newer installed libbpf.so
> >> > > > or any version of libbpf.a that is statically linked into apps
> >> > > > is something that libbpf code has to support.
> >> > > > The server can be rebooted into older than libbpf kernel and
> >> > > > into newer than libbpf kernel. libbpf has to recognize all these
> >> > > > combinations and work appropriately.
> >> > > > That's what backward and forward compatibility is.
> >> > > > That's what makes libbpf so difficult to test, develop and code review.
> >> > > > What that particular server has in /usr/include is irrelevant.
> >> > >
> >> > > sure, anyway we can't compile following:
> >> > >
> >> > > tredaell@aldebaran ~ $ echo "#include <bpf/xsk.h>" | gcc -x c -
> >> > > In file included from <stdin>:1:
> >> > > /usr/include/bpf/xsk.h: In function ‘xsk_ring_prod__needs_wakeup’:
> >> > > /usr/include/bpf/xsk.h:82:21: error: ‘XDP_RING_NEED_WAKEUP’ undeclared (first use in this function)
> >> > > 82 | return *r->flags & XDP_RING_NEED_WAKEUP;
> >> > > ...
> >> > >
> >> > > XDP_RING_NEED_WAKEUP is defined in kernel v5.4-rc1 (77cd0d7b3f257fd0e3096b4fdcff1a7d38e99e10).
> >> > > XSK_UNALIGNED_BUF_ADDR_MASK and XSK_UNALIGNED_BUF_OFFSET_SHIFT are defined in kernel v5.4-rc1 (c05cd3645814724bdeb32a2b4d953b12bdea5f8c).
> >> > >
> >> > > with:
> >> > > kernel-headers-5.3.6-300.fc31.x86_64
> >> > > libbpf-0.0.5-1.fc31.x86_64
> >> > >
> >> > > if you're saying this is not supported, I guess we could be postponing
> >> > > libbpf rpm releases until we have the related fedora kernel released
> >> >
> >> > why? github/libbpf is the source of truth for building packages
> >> > and afaik it builds fine.
> >>
> >> because we will get issues like above if there's no kernel
> >> avilable that we could compile libbpf against
> >
> > what is the issue again?
> > bpf-next builds fine. github/libbpf builds fine.
> > If distro is doing something else it's distro's mistake.
>
> With that you're saying that distros should always keep their kernel
> headers and libbpf version in sync. Which is fine in itself; they can
> certainly do that.
No. I'm not suggesting that.
distro is free to package whatever /usr/include headers.
kernel version is often != /usr/include headers
> The only concern with this is that without a flow of bugfixes into the
> 'bpf' tree (and stable), users may end up with buggy versions of libbpf.
> Which is in no one's interest. So how do we avoid that?
As I explained earlier. There is no 'bpf' tree for libbpf. It always
moves forward.
next prev parent reply other threads:[~2019-11-01 20:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 9:17 [PATCH bpf-next v3] libbpf: fix compatibility for kernels without need_wakeup Magnus Karlsson
2019-10-25 19:30 ` Jonathan Lemon
2019-10-29 3:27 ` Alexei Starovoitov
2019-10-30 13:33 ` Toke Høiland-Jørgensen
2019-10-31 7:17 ` Magnus Karlsson
2019-10-31 8:02 ` Björn Töpel
2019-10-31 8:17 ` Magnus Karlsson
2019-10-31 9:50 ` Toke Høiland-Jørgensen
2019-10-31 14:00 ` Alexei Starovoitov
2019-10-31 14:13 ` Toke Høiland-Jørgensen
2019-10-31 14:17 ` Alexei Starovoitov
2019-10-31 14:26 ` Toke Høiland-Jørgensen
2019-10-31 14:44 ` Alexei Starovoitov
2019-10-31 14:52 ` Toke Høiland-Jørgensen
2019-10-31 15:17 ` Alexei Starovoitov
2019-10-31 17:42 ` Jiri Olsa
2019-10-31 18:19 ` Alexei Starovoitov
2019-10-31 19:18 ` Jiri Olsa
2019-10-31 20:39 ` Alexei Starovoitov
2019-11-01 7:27 ` Jiri Olsa
2019-11-01 15:51 ` Alexei Starovoitov
2019-11-01 19:36 ` Toke Høiland-Jørgensen
2019-11-01 20:41 ` Alexei Starovoitov [this message]
2019-11-01 21:41 ` Toke Høiland-Jørgensen
2019-11-01 22:08 ` Alexei Starovoitov
2019-11-01 9:16 ` Toke Høiland-Jørgensen
2019-11-01 14:51 ` John Fastabend
2019-10-31 20:23 ` Andrii Nakryiko
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