[ovs-dev] [PATCH v1 branch-2.14 2/2] acinclude: Strip out -mno-avx512f provided by DPDK.

Ilya Maximets i.maximets at ovn.org
Fri Jan 15 18:13:53 UTC 2021


On 1/15/21 6:38 PM, Ian Stokes wrote:
> DPDK forces '-mno-avx512f' flag for the application if the toolchain
> used to build DPDK had broken AVX512 support.
> 
> DPDK forces '-mno-avx512f' flag for the application if the toolchain
> used to build DPDK had broken AVX512 support.  But OVS could be built
> with a completely different or fixed toolchain with correct avx512
> support.
> 
> Fix that by stripping out `-mno-avx512f` as we already do for '-march'.
> This will allow the OVS to decide if the AVX512 can be used.
> 
> Reordering of CFLAGS (i.e. adding DPDK flags before OVS ones) is not an
> option since autotools might reorder them back later and it's very
> unpredictable.
> 
> Reported-at: openvswitch/ovs-issues#201

Same here.
I think, it's better to have a URL here.  Could be changed on commit.
Otherwise, LGTM.

> Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
> Co-authored-by: Ilya Maximets <i.maximets at ovn.org>
> Signed-off-by: Ian Stokes <ian.stokes at intel.com>
> ---
>  acinclude.m4 | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/acinclude.m4 b/acinclude.m4
> index 14fe4218a..5710f5da8 100644
> --- a/acinclude.m4
> +++ b/acinclude.m4
> @@ -438,7 +438,13 @@ AC_DEFUN([OVS_CHECK_DPDK], [
>      fi
>      # Force in pkg-config since this could override user-specified options.
>      # It's enough to have -mssse3 to build with DPDK headers.
> -    DPDK_INCLUDE=$(echo "$DPDK_INCLUDE" | sed 's/-march=[[^ ]]*//g')
> +    DPDK_INCLUDE=$(echo "$DPDK_INCLUDE" | sed 's/-march=[[^ ]]*//g'
> +    # Also stripping out '-mno-avx512f'.  Support for AVX512 will be disabled
> +    # if OVS will detect that it's broken.  OVS could be built with a
> +    # completely different toolchain that correctly supports AVX512, flags
> +    # forced by DPDK only breaks our feature detection mechanism and leads to
> +    # build failures: https://github.com/openvswitch/ovs-issues/issues/201
> +    DPDK_INCLUDE=$(echo "$DPDK_INCLUDE" | sed 's/-mno-avx512f//g'))
>      OVS_CFLAGS="$OVS_CFLAGS $DPDK_INCLUDE"
>      OVS_ENABLE_OPTION([-mssse3])
>  
> 



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