Re: [PATCH 2/2] build: establish an invariant machine type

[Luca Boccassi <bluca@debian.org>]

On Wed, 2018-11-14 at 11:52 +0000, Bruce Richardson wrote:
> On Wed, Nov 14, 2018 at 11:40:11AM +0000, Luca Boccassi wrote:
> > On Wed, 2018-11-14 at 12:34 +0100, Christian Ehrhardt wrote:
> > > Add the machine definition 'baseline' which is special compared
> > > to 'native' (most optimized for current system) or any explicit
> > > type (external entity has to decide on the type).
> > > 
> > > It defaults to the per arch agreed common minimal baseline
> > > needed for DPDK to reasonable work.
> > > 
> > > That might not be the most optimized, but the most portable
> > > version while still being able to support the CPU features
> > > required for DPDK.
> > > 
> > > Going forward this can be bumped up by the DPDK project, but it
> > > can never be an invariant like 'native'.
> > > 
> > > Distributions and other needing portable code are expected to
> > > define the machine as 'baseline'.
> > > 
> > > Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.c
> > > om>
> > > ---
> > >  config/meson.build | 21 +++++++++++++++++++++
> > >  1 file changed, 21 insertions(+)
> > > 
> > > diff --git a/config/meson.build b/config/meson.build
> > > index 1af305f46..23f612457 100644
> > > --- a/config/meson.build
> > > +++ b/config/meson.build
> > > @@ -7,6 +7,27 @@ if meson.is_cross_build()
> > >  else
> > >  	machine = get_option('machine')
> > >  endif
> > > +
> > > +# machine type 'baseline' is special, it defaults to the per
> > > arch
> > > agreed common
> > > +# minimal baseline needed for DPDK.
> > > +# That might not be the most optimized, but the most portable
> > > version while
> > > +# still being able to support the CPU features required for
> > > DPDK.
> > > +# This can be bumped up by the DPDK project, but it can never be
> > > an
> > > +# invariant like 'native'
> > > +if machine == 'baseline'
> > > +	if host_machine.cpu_family().startswith('x86')
> > > +		# matches the old pre-meson build systems
> > > default
> > > +		machine = 'corei7'
> > > +	elif host_machine.cpu_family().startswith('arm')
> > > +		machine = 'armv7a'
> > > +	elif host_machine.cpu_family().startswith('aarch')
> > > +		# arm64 manages defaults in
> > > config/arm/meson.build
> > > +		machine = 'default'
> > > +	elif host_machine.cpu_family().startswith('ppc')
> > > +		machine = 'power8'
> > > +	endif
> > > +endif
> > > +
> > >  dpdk_conf.set('RTE_MACHINE', machine)
> > >  machine_args = []
> > 
> > Acked-by: Luca Boccassi <bluca@debian.org>
> > 
> 
> No objection in principle, but, for alignment with make build system,
> do we
> want to call this "default" instead? Given a clean slate, "baseline"
> is more
> descriptive, but make already uses "default" for this. Perhaps
> support
> both?
> 
> /Bruce

I'm fine with both - but if make already has default, it makes sense to
keep it consistent.

-- 
Kind regards,
Luca Boccassi