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.
[...]
--
WBR,
Yauheni Kaliuta
