Re: [dpdk-dev] [PATCH v10 1/1] net/af_xdp: introduce AF XDP PMD driver

[Luca Boccassi <bluca@debian.org>]

On Thu, 2019-04-04 at 13:55 +0800, Ye Xiaolong wrote:
> Hi, Luca
> 
> On 04/03, Luca Boccassi wrote:
> > On Wed, 2019-04-03 at 18:44 +0100, Ferruh Yigit wrote:
> > > On 4/3/2019 5:59 PM, Xiaolong Ye wrote:
> > > > Add a new PMD driver for AF_XDP which is a proposed faster
> > > > version
> > > > of
> > > > AF_PACKET interface in Linux. More info about AF_XDP, please
> > > > refer
> > > > to [1]
> > > > [2].
> > > > 
> > > > This is the vanilla version PMD which just uses a raw buffer
> > > > registered as
> > > > the umem.
> > > > 
> > > > [1] 
> > > > https://fosdem.org/2018/schedule/event/af_xdp/
> > > > 
> > > > 
> > > > [2] 
> > > > https://lwn.net/Articles/745934/
> > > > 
> > > > 
> > > > 
> > > > Signed-off-by: Xiaolong Ye <
> > > > xiaolong.ye@intel.com
> > > > 
> > > 
> > > I am not able to test functionality but code looks good to me, I
> > > can
> > > compile via
> > > Makefile (with suggested steps in doc) but not able to build with
> > > meson, can you
> > > please check below comments?
> > > 
> > > <...>
> > > 
> > > > @@ -0,0 +1,21 @@
> > > > +# SPDX-License-Identifier: BSD-3-Clause
> > > > +# Copyright(c) 2019 Intel Corporation
> > > > +
> > > > +if host_machine.system() != 'linux'
> > > > +	build = false
> > > > +endif
> > > 
> > > After this point, if build is false it shouldn't continue to
> > > below
> > > checks I think.
> > > 
> > > > +
> > > > +bpf_dep = dependency('libbpf', required: false)
> > > 
> > > My library is in '/usr/local/lib64/libbpf.so' but this line can't
> > > find it. Where
> > > does 'dependency()' checks for libraries?
> > 
> > dependency() uses only pkg-config (or cmake or embedded specific
> > tools,
> > neither of which applies to bpf), so if you haven't built from bpf-
> > next 
> > you won't have the pkg-config file installed, and it will fall back
> > to
> > the next block.
> > 
> > Side note, there's an issue open upstream in Meson to merge
> > dependency() and find_library(), with some traction but it's not
> > done
> > yet.
> > 
> > For me building from bpf-next it works fine:
> > 
> > $ PKG_CONFIG_PATH=/tmp/bpf/lib64/pkgconfig/ ninja -C build-gcc-
> > shared
> > ...
> > Dependency libbpf found: YES 0.0.2
> > ...
> > $ lddtree build-gcc-shared/drivers/librte_pmd_af_xdp.so.1.1 
> > librte_pmd_af_xdp.so.1.1 => build-gcc-
> > shared/drivers/librte_pmd_af_xdp.so.1.1 (interpreter => none)
> >    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6
> >    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2
> >    libnuma.so.1 => /lib/x86_64-linux-gnu/libnuma.so.1
> >    librte_ethdev.so.12 => build-gcc-
> > shared/drivers/../lib/librte_ethdev.so.12
> >    librte_eal.so.10 => build-gcc-
> > shared/drivers/../lib/librte_eal.so.10
> >    librte_kvargs.so.1 => build-gcc-
> > shared/drivers/../lib/librte_kvargs.so.1
> >    librte_net.so.1 => build-gcc-
> > shared/drivers/../lib/librte_net.so.1
> >    librte_mbuf.so.5 => build-gcc-
> > shared/drivers/../lib/librte_mbuf.so.5
> >    librte_mempool.so.5 => build-gcc-
> > shared/drivers/../lib/librte_mempool.so.5
> >    librte_ring.so.2 => build-gcc-
> > shared/drivers/../lib/librte_ring.so.2
> >    librte_cmdline.so.2 => build-gcc-
> > shared/drivers/../lib/librte_cmdline.so.2
> >    librte_meter.so.2 => build-gcc-
> > shared/drivers/../lib/librte_meter.so.2
> >    librte_bus_pci.so.2 => not found
> >    librte_pci.so.1 => build-gcc-
> > shared/drivers/../lib/librte_pci.so.1
> >    librte_bus_vdev.so.2 => not found
> >    libbsd.so.0 => /lib/x86_64-linux-gnu/libbsd.so.0
> >        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1
> >    libbpf.so.0 => /tmp/bpf/lib64/libbpf.so.0
> >        libelf.so.1 => /lib/x86_64-linux-gnu/libelf.so.1
> >            libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1
> >    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
> >    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6
> >    ld-linux-x86-64.so.2 => /lib/x86_64-linux-gnu/ld-linux-x86-
> > 64.so.2
> > 
> > > > +if bpf_dep.found()
> > > > +	build = true
> > > > +else
> > > > +	bpf_dep = cc.find_library('libbpf', required: false)
> > > 
> > > Also this line can't find it, in log it says "(tried pkgconfig
> > > and
> > > cmake)" and
> > > yes there is no pkgconfig for it, any idea how 'cmake' used?
> > 
> > The issue here is that it should be cc.find_library('bpf' - not
> > 'libbpf'. I missed this when reviewing, good catch.
> > 
> > That's because find_library just does a compilation test passing
> > the
> > value to the compiler as a linker flag - so right now it's passing
> > -llibbpf. Fixing this line and the header line below makes it work
> > without pkg-config:
> > 
> > $ CPPFLAGS=-I/tmp/bpf/include LDFLAGS=-L/tmp/bpf/lib64 meson testt
> > ...
> > Dependency libbpf found: NO (tried pkgconfig and cmake)
> > Library bpf found: YES
> 
> After apply the fix in af_xdp pmd's meson.build, now I was able to
> build
> library for af_xdp pmd.
> 
> $ ls drivers/ |grep xdp
> a715181@@rte_pmd_af_xdp@sha
> a715181@@rte_pmd_af_xdp@sta
> a715181@@tmp_rte_pmd_af_xdp@sta
> librte_pmd_af_xdp.a
> librte_pmd_af_xdp.so
> librte_pmd_af_xdp.so.1
> librte_pmd_af_xdp.so.1.1
> libtmp_rte_pmd_af_xdp.a
> rte_pmd_af_xdp.pmd.c
> 
> But I found that if I install libbpf to /usr/local/lib64 by default,
> application
> built by meson build will fail to run:
> 
> $ ./dpdk-testpmd
> ./dpdk-testpmd: error while loading shared libraries: libbpf.so.0:
> cannot open shared object file: No such file or directory
> 
> While install libbpf to /usr/lib doesn't have this issue (I was
> testing on ubuntu system).
> Is it a expected behavior? Do we need any fix for it?

Hi,

That is expected and distro specific: if your distro doesn't add
/usr/local/lib* to the compiler path, it also won't be in the
LD_LIBRARY_PATH.

So if you do:

LD_LIBRARY_PATH=/usr/local/lib64 ./dpdk-testpmd

It should then work. It's not related to the build system, but just to
what the default paths are in the distro.

-- 
Kind regards,
Luca Boccassi