Re: [dpdk-stable] [PATCH 20.11] config/arm: replace native machine args

[Luca Boccassi <bluca@debian.org>]

On Fri, 2021-02-19 at 11:06 +0000, Juraj Linkeš wrote:
> > -----Original Message-----
> > From: luca.boccassi@gmail.com <luca.boccassi@gmail.com>
> > Sent: Friday, February 19, 2021 11:58 AM
> > To: stable@dpdk.org
> > Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>; jerinj@marvell.com;
> > ruifeng.wang@arm.com; david.marchand@redhat.com
> > Subject: [PATCH 20.11] config/arm: replace native machine args
> > 
> > From: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > 
> > [ backported from upstream commit
> > 9186e5a07f35ae74a1f7fa2d89671b5f77eae407 ]
> > 
> > There are compiler issues when building with -mcpu=native with popular
> > compilers, such as GCC-8.4:
> > In file included from ../lib/librte_eal/arm/include/rte_vect.h:11,
> >                  from ../lib/librte_net/net_crc_neon.c:10:
> > ../lib/librte_net/net_crc_neon.c: In function ‘crcr32_folding_round’:
> > /usr/lib/gcc/aarch64-linux-gnu/8/include/arm_neon.h:26094:1: error:
> > inlining failed in call to always_inline ‘vmull_p64’:
> > target specific option mismatch
> >  vmull_p64 (poly64_t a, poly64_t b)
> > ../lib/librte_net/net_crc_neon.c:50:20: note: called from here
> >   uint64x2_t tmp1 = vreinterpretq_u64_p128(vmull_p64(
> >     vgetq_lane_p64(vreinterpretq_p64_u64(fold), 0),
> >     vgetq_lane_p64(vreinterpretq_p64_u64(precomp), 1)));
> > 
> > and clang:
> > gcc -E -dM -mcpu="native" - < /dev/null | grep __ARM_FEATURE_ATOMICS
> > clang-9 -E -dM -mcpu="native" - < /dev/null | grep __ARM_FEATURE_ATOMICS
> > <no output> # no clang support
> > 
> > Fix this by always specifying the proper machine args and never using the native
> > flags.
> > 
> > Fixes: 78ac8eac7e8a ("config/arm: use native machine build arguments")
> > 
> > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > Signed-off-by: Luca Boccassi <luca.boccassi@microsoft.com>
> > ---
> > This is a crude backport, but it fixes the build for arm64. It's a release blocker for
> > 20.11.1, so I would appreciate a quick review.
> > Thanks!
> 
> What does this fix? With or without the below change, the native machine args are not used. The patch shoudn't actually change the configuration of the build at all, so I'm a bit confused.

It fixes the build on some build workers with thunderx hardware -
without this I get failures like:

arm_neon.h:26647:1: error: inlining failed in call to 'always_inline'
'vmull_p64': target specific option mismatch

-- 
Kind regards,
Luca Boccassi