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

[Luca Boccassi]

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 at 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

> > +	if bpf_dep.found() and cc.has_header('xsk.h', dependencies:
> > bpf_dep) and cc.has_header('linux/if_xdp.h')
> 
> Should this be 'lib/xsk.h' now?

Yes, this should be 'bpf/xsk.h'

-- 
Kind regards,
Luca Boccassi