On Wed, Sep 4, 2019 at 2:19 PM Yauheni Kaliuta
<yauheni.kaliuta@xxxxxxxxxx> wrote:
>
> Hi, Magnus!
>
> >>>>> On Wed, 4 Sep 2019 12:25:13 +0200, Magnus Karlsson wrote:
> > On Wed, Sep 4, 2019 at 8:56 AM Yauheni Kaliuta
> > <yauheni.kaliuta@xxxxxxxxxx> wrote:
> >>
> >> Hi, Magnus!
> >>
> >> >>>>> On Wed, 4 Sep 2019 08:39:24 +0200, Magnus Karlsson wrote:
> >>
> >> > On Wed, Sep 4, 2019 at 7:32 AM Yauheni Kaliuta
> >> > <yauheni.kaliuta@xxxxxxxxxx> wrote:
> >> >>
> >> >> Hi, Magnus!
> >> >>
> >> >> >>>>> On Tue, 9 Apr 2019 08:44:13 +0200, Magnus Karlsson wrote:
> >> >>
> >> >> > The use of smp_rmb() and smp_wmb() creates a Linux header dependency
> >> >> > on barrier.h that is uneccessary in most parts. This patch implements
> >> >> > the two small defines that are needed from barrier.h. As a bonus, the
> >> >> > new implementations are faster than the default ones as they default
> >> >> > to sfence and lfence for x86, while we only need a compiler barrier in
> >> >> > our case. Just as it is when the same ring access code is compiled in
> >> >> > the kernel.
> >> >>
> >> >> > Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
> >> >> > Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> >> >> > ---
> >> >> > tools/lib/bpf/xsk.h | 19 +++++++++++++++++--
> >> >> > 1 file changed, 17 insertions(+), 2 deletions(-)
> >> >>
> >> >> > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> >> >> > index 3638147..317b44f 100644
> >> >> > --- a/tools/lib/bpf/xsk.h
> >> >> > +++ b/tools/lib/bpf/xsk.h
> >> >> > @@ -39,6 +39,21 @@ DEFINE_XSK_RING(xsk_ring_cons);
> >> >> > struct xsk_umem;
> >> >> > struct xsk_socket;
> >> >>
> >> >> > +#if !defined bpf_smp_rmb && !defined bpf_smp_wmb
> >> >> > +# if defined(__i386__) || defined(__x86_64__)
> >> >> > +# define bpf_smp_rmb() asm volatile("" : : : "memory")
> >> >> > +# define bpf_smp_wmb() asm volatile("" : : : "memory")
> >> >> > +# elif defined(__aarch64__)
> >> >> > +# define bpf_smp_rmb() asm volatile("dmb ishld" : : : "memory")
> >> >> > +# define bpf_smp_wmb() asm volatile("dmb ishst" : : : "memory")
> >> >> > +# elif defined(__arm__)
> >> >> > +# define bpf_smp_rmb() asm volatile("dmb ish" : : : "memory")
> >> >> > +# define bpf_smp_wmb() asm volatile("dmb ishst" : : : "memory")
> >> >> > +# else
> >> >> > +# error Architecture not supported by the XDP socket code in libbpf.
> >> >> > +# endif
> >> >> > +#endif
> >> >> > +
> >> >>
> >> >> What about other architectures then?
> >>
> >> > AF_XDP has not been tested on anything else, as far as I
> >> > know. But contributions that extend it to more archs are
> >> > very welcome.
> >>
> >> Well, I'll may be try to fetch something from barrier.h's
> >> (since I cannot consider myself as a specialist in the area),
> >> but at the moment the patch breaks the build on that arches.
>
> > Do you have a specific architecture in mind and do you have
> > some board/server (of that architecture) you could test AF_XDP
> > on?
>
> I do care about s390 and ppc64 and I can run tests for them.
Perfect!. Thanks.
/Magnus
>
> [...]
>
> --
> WBR,
> Yauheni Kaliuta
