Re: [dpdk-dev] [PATCH] mk: fix application compilation with lmnl and mlx5

["Nélio Laranjeiro" <nelio.laranjeiro@6wind.com>]

On Tue, Jul 24, 2018 at 11:21:52AM +0000, Shahaf Shuler wrote:
> Tuesday, July 24, 2018 12:29 PM, Nelio Laranjeiro:
> > Subject: [PATCH] mk: fix application compilation with lmnl and mlx5
> > 
> > When Mellanox MLX5 PMD is compiled with
> > CONFIG_RTE_LIBRTE_MLX5_DLOPEN_DEPS=y, the external dependency on
> > libmln is missing.
> > 
> > Fixes: 4d5cce06231a ("net/mlx5: lay groundwork for switch offloads")
> > Cc: adrien.mazarguil@6wind.com
> > 
> > Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
> > ---
> >  mk/rte.app.mk | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mk/rte.app.mk b/mk/rte.app.mk index f4d28c2da..ff39d37aa
> > 100644
> > --- a/mk/rte.app.mk
> > +++ b/mk/rte.app.mk
> > @@ -149,7 +149,7 @@ else
> >  _LDLIBS-$(CONFIG_RTE_LIBRTE_MLX4_PMD)       += -lrte_pmd_mlx4 -
> > libverbs -lmlx4
> >  endif
> >  ifeq ($(CONFIG_RTE_LIBRTE_MLX5_DLOPEN_DEPS),y)
> > -_LDLIBS-$(CONFIG_RTE_LIBRTE_MLX5_PMD)       += -lrte_pmd_mlx5 -ldl
> > +_LDLIBS-$(CONFIG_RTE_LIBRTE_MLX5_PMD)       += -lrte_pmd_mlx5 -ldl -
> > lmnl
> 
> This issue raise some more basic question. 
> The DLOPEN mode was introduced to run in systems which don't have
> verbs/mlx5 libs installed, because those were the only dependencies
> for the PMD back then.
> Now we have the libmnl, which is external dependency just like
> rdma-core, and following your fix, hard linked also in case of DLOPEN
> option.
> It means the whole DPDK binary/lib will be depended on libmnl and this
> is not what we want with DLOPEN.
> 
> Can we consider different options:
> 1. always statically link libmnl

This will force users to re-compile their application to have the missing
features disabled because some calls are not available, see the list of
HAVE_RDMA_NLDEV_* elements in the MLX5 makefile due to the issues this
Netlink stuff brings.

> 2. dlopen libmnl just like we do for verbs/mlx5

You want another glue library.  It won't be for this release in this
case, I don't have time to write such glue.

> >  else
> >  _LDLIBS-$(CONFIG_RTE_LIBRTE_MLX5_PMD)       += -lrte_pmd_mlx5 -
> > libverbs -lmlx5 -lmnl
> >  endif
> > --
> > 2.18.0
> 

[1] https://mails.dpdk.org/archives/dev/2018-March/092876.html

-- 
Nélio Laranjeiro
6WIND