Re: [dpdk-dev] [PATCH v2] vhost: Fix linkage of vhost PMD

[Tetsuya Mukawa <mukawa@igel.co.jp>]

On 2016/04/26 18:35, Panu Matilainen wrote:
> On 04/26/2016 08:39 AM, Tetsuya Mukawa wrote:
>> Currently, vhost PMD doesn't have linkage for librte_vhost, even though
>> it depends on librte_vhost APIs. This causes a linkage error if below
>> conditions are fulfilled.
>>
>>  - DPDK libraries are compiled as shared libraries.
>>  - DPDK application doesn't link librte_vhost.
>>  - Above application tries to link vhost PMD using '-d' DPDK option.
>>
>> The patch adds linkage for librte_vhost to vhost PMD not to cause an
>> above error.
>>
>> Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
>> Acked-by: Panu Matilainen <pmatilai@redhat.com>
>> ---
>>  drivers/net/vhost/Makefile | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/vhost/Makefile b/drivers/net/vhost/Makefile
>> index f49a69b..30b91a0 100644
>> --- a/drivers/net/vhost/Makefile
>> +++ b/drivers/net/vhost/Makefile
>> @@ -38,6 +38,7 @@ LIB = librte_pmd_vhost.a
>>
>>  CFLAGS += -O3
>>  CFLAGS += $(WERROR_FLAGS)
>> +LDLIBS += -lrte_vhost
>>
>>  EXPORT_MAP := rte_pmd_vhost_version.map
>>
>>
>
> Hmm, turns out this isn't quite enough, simply because its the first
> of its kind (first internal dependency between libraries), at least
> I'm getting:
>
> == Build drivers/net/vhost
> gcc -m64
> -Wl,--version-script=/srv/work/dist/dpdk/dpdk-16.04/drivers/net/vhost/rte_pmd_vhost_version.map
>  -shared rte_eth_vhost.o -lrte_vhost -Wl,-soname,librte_pmd_vhost.so.1
> -o librte_pmd_vhost.so.1
> /usr/bin/ld: cannot find -lrte_vhost
> collect2: error: ld returned 1 exit status
> /srv/work/dist/dpdk/dpdk-16.04/mk/rte.lib.mk:127: recipe for target
> 'librte_pmd_vhost.so.1' failed
>
> So it'll need something like this as a pre-requisite to add the
> internal libraries to the linker path:
>
> diff --git a/mk/rte.lib.mk b/mk/rte.lib.mk
> index 8f7e021..f5d7b04 100644
> --- a/mk/rte.lib.mk
> +++ b/mk/rte.lib.mk
> @@ -86,7 +86,7 @@ O_TO_A_DO = @set -e; \
>         $(O_TO_A) && \
>         echo $(O_TO_A_CMD) > $(call exe2cmd,$(@))
>
> -O_TO_S = $(LD) $(_CPU_LDFLAGS) $(EXTRA_LDFLAGS) -shared $(OBJS-y)
> $(LDLIBS) \
> +O_TO_S = $(LD) -L$(RTE_OUTPUT)/lib $(_CPU_LDFLAGS) $(EXTRA_LDFLAGS)
> -shared $(OBJS-y) $(LDLIBS) \
>          -Wl,-soname,$(LIB) -o $(LIB)
>  O_TO_S_STR = $(subst ','\'',$(O_TO_S)) #'# fix syntax highlight
>  O_TO_S_DISP = $(if $(V),"$(O_TO_S_STR)","  LD $(@)")
>
>
> I can submit an official patch for this later but I'm not exactly
> feeling like the sharpest knife in the drawer today so if somebody
> beats me to it, feel free.
>
>     - Panu -

Thanks for catching it.
It seems I've already installed DPDK libraries in /usr/local/lib/. Then
, I could not catch this error.
I've confirmed your solution works fine.

Thanks,
Tetsuya