[dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Bruce Richardson]

Traditionally any apps built using DPDK had to support the same
instruction sets as supported when the DPDK SDK itself was built, since
that was "leaked" through to the end-app and DPDK headers via
RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
for app build correctness the "-march=" flag was included in the
pkg-config cflags output.

However, since the DPDK-specific CPU flags are now obsolete, and we
instead check directly for compiler-defined flags, we should no longer
need to force the exact same architecture match in all cases. To
faciliate such flexibility, a new pkg_config_machine_args array - which
defaults to the existing machine_args array has been defined. The
individual architectures - x86, arm and ppc - can choose if and how to
override this value themselves.

For x86, since SSE4.2 is the minimum instruction-set level needed to run
DPDK, and since some header files assume that minimum level of
instruction set support, we override the "-march=" value with "-msse4"
for the pkg-config file. This allows end applications to set their own
"march" value while still ensuring valid DPDK compilation.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---

CC: Jerin Jacob <jerinj@marvell.com>
CC: Ruifeng Wang <ruifeng.wang@arm.com>
CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
CC: David Christensen <drc@linux.vnet.ibm.com>
Feedback requested from ARM and PPC maintainers as to this change
and what flags, if any, need to be in the .pc file for DPDK on such
platforms. For example - is setting 'pkg_config_machine_args' to
'machine_args' by default necessary behaviour?

---
 buildtools/pkg-config/meson.build | 2 +-
 config/meson.build                | 1 +
 config/x86/meson.build            | 3 +++
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/buildtools/pkg-config/meson.build b/buildtools/pkg-config/meson.build
index 5f1930428..8e2e24681 100644
--- a/buildtools/pkg-config/meson.build
+++ b/buildtools/pkg-config/meson.build
@@ -2,7 +2,7 @@
 # Copyright(c) 2020 Intel Corporation

 pkg = import('pkgconfig')
-pkg_extra_cflags = ['-include', 'rte_config.h'] + machine_args
+pkg_extra_cflags = ['-include', 'rte_config.h'] + pkg_config_machine_args
 if is_freebsd
 	pkg_extra_cflags += ['-D__BSD_VISIBLE']
 endif
diff --git a/config/meson.build b/config/meson.build
index 3ddcc3539..d58ff781d 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -100,6 +100,7 @@ if host_machine.cpu_family().startswith('ppc')
 else
 	machine_args += '-march=' + machine
 endif
+pkg_config_machine_args = machine_args # may be overriden late per arch

 toolchain = cc.get_id()
 dpdk_conf.set_quoted('RTE_TOOLCHAIN', toolchain)
diff --git a/config/x86/meson.build b/config/x86/meson.build
index 31bfa63b1..fcd75502e 100644
--- a/config/x86/meson.build
+++ b/config/x86/meson.build
@@ -16,6 +16,9 @@ if cc.get_define('__SSE4_2__', args: machine_args) == ''
 	machine_args += '-msse4'
 endif

+# require SSE4.2 in pkg-config file - don't use -march
+pkg_config_machine_args = ['-msse4']
+
 base_flags = ['SSE', 'SSE2', 'SSE3','SSSE3', 'SSE4_1', 'SSE4_2']
 foreach f:base_flags
 	compile_time_cpuflags += ['RTE_CPUFLAG_' + f]
--
2.27.0

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[David Christensen]

On 12/11/20 7:51 AM, Bruce Richardson wrote:
> Traditionally any apps built using DPDK had to support the same
> instruction sets as supported when the DPDK SDK itself was built, since
> that was "leaked" through to the end-app and DPDK headers via
> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
> for app build correctness the "-march=" flag was included in the
> pkg-config cflags output.
> 
> However, since the DPDK-specific CPU flags are now obsolete, and we
> instead check directly for compiler-defined flags, we should no longer
> need to force the exact same architecture match in all cases. To
> faciliate such flexibility, a new pkg_config_machine_args array - which
> defaults to the existing machine_args array has been defined. The
> individual architectures - x86, arm and ppc - can choose if and how to
> override this value themselves.
> 
> For x86, since SSE4.2 is the minimum instruction-set level needed to run
> DPDK, and since some header files assume that minimum level of
> instruction set support, we override the "-march=" value with "-msse4"
> for the pkg-config file. This allows end applications to set their own
> "march" value while still ensuring valid DPDK compilation.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
> 
> CC: Jerin Jacob <jerinj@marvell.com>
> CC: Ruifeng Wang <ruifeng.wang@arm.com>
> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> CC: David Christensen <drc@linux.vnet.ibm.com>
> Feedback requested from ARM and PPC maintainers as to this change
> and what flags, if any, need to be in the .pc file for DPDK on such
> platforms. For example - is setting 'pkg_config_machine_args' to
> 'machine_args' by default necessary behaviour?

Support for Altivec would be the equivalent here for PPC and I'm not 
aware of any additional flags required for supported POWER CPUs on DPDK. 
  I can't speak to P10 requirements yet but the proposed change is a 
don't care for me.

Dave

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Bruce Richardson]

On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote:
> Traditionally any apps built using DPDK had to support the same
> instruction sets as supported when the DPDK SDK itself was built, since
> that was "leaked" through to the end-app and DPDK headers via
> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
> for app build correctness the "-march=" flag was included in the
> pkg-config cflags output.
> 
> However, since the DPDK-specific CPU flags are now obsolete, and we
> instead check directly for compiler-defined flags, we should no longer
> need to force the exact same architecture match in all cases. To
> faciliate such flexibility, a new pkg_config_machine_args array - which
> defaults to the existing machine_args array has been defined. The
> individual architectures - x86, arm and ppc - can choose if and how to
> override this value themselves.
> 
> For x86, since SSE4.2 is the minimum instruction-set level needed to run
> DPDK, and since some header files assume that minimum level of
> instruction set support, we override the "-march=" value with "-msse4"
> for the pkg-config file. This allows end applications to set their own
> "march" value while still ensuring valid DPDK compilation.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
> 
> CC: Jerin Jacob <jerinj@marvell.com>
> CC: Ruifeng Wang <ruifeng.wang@arm.com>
> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> CC: David Christensen <drc@linux.vnet.ibm.com>
> Feedback requested from ARM and PPC maintainers as to this change
> and what flags, if any, need to be in the .pc file for DPDK on such
> platforms. For example - is setting 'pkg_config_machine_args' to
> 'machine_args' by default necessary behaviour?
> 

Ping for further thoughts or input on this patch.

/Bruce

> ---
>  buildtools/pkg-config/meson.build | 2 +-
>  config/meson.build                | 1 +
>  config/x86/meson.build            | 3 +++
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/buildtools/pkg-config/meson.build b/buildtools/pkg-config/meson.build
> index 5f1930428..8e2e24681 100644
> --- a/buildtools/pkg-config/meson.build
> +++ b/buildtools/pkg-config/meson.build
> @@ -2,7 +2,7 @@
>  # Copyright(c) 2020 Intel Corporation
> 
>  pkg = import('pkgconfig')
> -pkg_extra_cflags = ['-include', 'rte_config.h'] + machine_args
> +pkg_extra_cflags = ['-include', 'rte_config.h'] + pkg_config_machine_args
>  if is_freebsd
>  	pkg_extra_cflags += ['-D__BSD_VISIBLE']
>  endif
> diff --git a/config/meson.build b/config/meson.build
> index 3ddcc3539..d58ff781d 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -100,6 +100,7 @@ if host_machine.cpu_family().startswith('ppc')
>  else
>  	machine_args += '-march=' + machine
>  endif
> +pkg_config_machine_args = machine_args # may be overriden late per arch
> 
>  toolchain = cc.get_id()
>  dpdk_conf.set_quoted('RTE_TOOLCHAIN', toolchain)
> diff --git a/config/x86/meson.build b/config/x86/meson.build
> index 31bfa63b1..fcd75502e 100644
> --- a/config/x86/meson.build
> +++ b/config/x86/meson.build
> @@ -16,6 +16,9 @@ if cc.get_define('__SSE4_2__', args: machine_args) == ''
>  	machine_args += '-msse4'
>  endif
> 
> +# require SSE4.2 in pkg-config file - don't use -march
> +pkg_config_machine_args = ['-msse4']
> +
>  base_flags = ['SSE', 'SSE2', 'SSE3','SSSE3', 'SSE4_1', 'SSE4_2']
>  foreach f:base_flags
>  	compile_time_cpuflags += ['RTE_CPUFLAG_' + f]
> --
> 2.27.0
> 

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[David Christensen]

On 9/15/21 9:28 AM, Bruce Richardson wrote:
> On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote:
>> Traditionally any apps built using DPDK had to support the same
>> instruction sets as supported when the DPDK SDK itself was built, since
>> that was "leaked" through to the end-app and DPDK headers via
>> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
>> for app build correctness the "-march=" flag was included in the
>> pkg-config cflags output.
>>
>> However, since the DPDK-specific CPU flags are now obsolete, and we
>> instead check directly for compiler-defined flags, we should no longer
>> need to force the exact same architecture match in all cases. To
>> faciliate such flexibility, a new pkg_config_machine_args array - which
>> defaults to the existing machine_args array has been defined. The
>> individual architectures - x86, arm and ppc - can choose if and how to
>> override this value themselves.
>>
>> For x86, since SSE4.2 is the minimum instruction-set level needed to run
>> DPDK, and since some header files assume that minimum level of
>> instruction set support, we override the "-march=" value with "-msse4"
>> for the pkg-config file. This allows end applications to set their own
>> "march" value while still ensuring valid DPDK compilation.
>>
>> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
>> ---
>>
>> CC: Jerin Jacob <jerinj@marvell.com>
>> CC: Ruifeng Wang <ruifeng.wang@arm.com>
>> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
>> CC: David Christensen <drc@linux.vnet.ibm.com> for 
>> Feedback requested from ARM and PPC maintainers as to this change
>> and what flags, if any, need to be in the .pc file for DPDK on such
>> platforms. For example - is setting 'pkg_config_machine_args' to
>> 'machine_args' by default necessary behaviour?
>>
> 
> Ping for further thoughts or input on this patch.

On initial inspection I don't see any additional value for PPC systems. 
  Selection of a CPU through -mcpu implies a full ISA for that CPU, 
including things like vector extensions, at least with respect to the 
minimum supported POWER8 CPU (ISA 2.07) and later ISAs.  The values of 
machine_args and pkg_config_machine_args should be identical in all 
cases I can think of.

If a third party OpenPOWER CPU comes along some time in the future then 
the requirements may change.

Dave

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Jerin Jacob]

On Thu, Sep 16, 2021 at 2:53 AM David Christensen
<drc@linux.vnet.ibm.com> wrote:
>
>
>
> On 9/15/21 9:28 AM, Bruce Richardson wrote:
> > On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote:
> >> Traditionally any apps built using DPDK had to support the same
> >> instruction sets as supported when the DPDK SDK itself was built, since
> >> that was "leaked" through to the end-app and DPDK headers via
> >> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
> >> for app build correctness the "-march=" flag was included in the
> >> pkg-config cflags output.
> >>
> >> However, since the DPDK-specific CPU flags are now obsolete, and we
> >> instead check directly for compiler-defined flags, we should no longer
> >> need to force the exact same architecture match in all cases. To
> >> faciliate such flexibility, a new pkg_config_machine_args array - which
> >> defaults to the existing machine_args array has been defined. The
> >> individual architectures - x86, arm and ppc - can choose if and how to
> >> override this value themselves.
> >>
> >> For x86, since SSE4.2 is the minimum instruction-set level needed to run
> >> DPDK, and since some header files assume that minimum level of
> >> instruction set support, we override the "-march=" value with "-msse4"
> >> for the pkg-config file. This allows end applications to set their own
> >> "march" value while still ensuring valid DPDK compilation.
> >>
> >> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> >> ---
> >>
> >> CC: Jerin Jacob <jerinj@marvell.com>
> >> CC: Ruifeng Wang <ruifeng.wang@arm.com>
> >> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> >> CC: David Christensen <drc@linux.vnet.ibm.com> for
> >> Feedback requested from ARM and PPC maintainers as to this change
> >> and what flags, if any, need to be in the .pc file for DPDK on such
> >> platforms. For example - is setting 'pkg_config_machine_args' to
> >> 'machine_args' by default necessary behaviour?
> >>
> >
> > Ping for further thoughts or input on this patch.

Armv8 has dedicated config(taken least cpu flags which supports all
armv8) for this purpose config/arm/arm64_armv8_linux_gcc.
So this change looks good to me. @Ruifeng Wang (Arm Technology China)
Any comments?


>
> On initial inspection I don't see any additional value for PPC systems.
>   Selection of a CPU through -mcpu implies a full ISA for that CPU,
> including things like vector extensions, at least with respect to the
> minimum supported POWER8 CPU (ISA 2.07) and later ISAs.  The values of
> machine_args and pkg_config_machine_args should be identical in all
> cases I can think of.
>
> If a third party OpenPOWER CPU comes along some time in the future then
> the requirements may change.




>
> Dave

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Ruifeng Wang]

> -----Original Message-----
> From: Jerin Jacob <jerinjacobk@gmail.com>
> Sent: Thursday, September 16, 2021 11:43 AM
> To: David Christensen <drc@linux.vnet.ibm.com>
> Cc: Bruce Richardson <bruce.richardson@intel.com>; dpdk-dev
> <dev@dpdk.org>; Luca Boccassi <bluca@debian.org>; David Marchand
> <david.marchand@redhat.com>; ian.stokes@intel.com; Ilya Maximets
> <i.maximets@ovn.org>; jerinj@marvell.com; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; Ferruh Yigit <ferruh.yigit@intel.com>
> Subject: Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch
> flag
> 
> On Thu, Sep 16, 2021 at 2:53 AM David Christensen <drc@linux.vnet.ibm.com>
> wrote:
> >
> >
> >
> > On 9/15/21 9:28 AM, Bruce Richardson wrote:
> > > On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote:
> > >> Traditionally any apps built using DPDK had to support the same
> > >> instruction sets as supported when the DPDK SDK itself was built,
> > >> since that was "leaked" through to the end-app and DPDK headers via
> > >> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to
> > >> meson for app build correctness the "-march=" flag was included in
> > >> the pkg-config cflags output.
> > >>
> > >> However, since the DPDK-specific CPU flags are now obsolete, and we
> > >> instead check directly for compiler-defined flags, we should no
> > >> longer need to force the exact same architecture match in all
> > >> cases. To faciliate such flexibility, a new pkg_config_machine_args
> > >> array - which defaults to the existing machine_args array has been
> > >> defined. The individual architectures - x86, arm and ppc - can
> > >> choose if and how to override this value themselves.
> > >>
> > >> For x86, since SSE4.2 is the minimum instruction-set level needed
> > >> to run DPDK, and since some header files assume that minimum level
> > >> of instruction set support, we override the "-march=" value with "-
> msse4"
> > >> for the pkg-config file. This allows end applications to set their
> > >> own "march" value while still ensuring valid DPDK compilation.
> > >>
> > >> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > >> ---
> > >>
> > >> CC: Jerin Jacob <jerinj@marvell.com>
> > >> CC: Ruifeng Wang <ruifeng.wang@arm.com>
> > >> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > >> CC: David Christensen <drc@linux.vnet.ibm.com> for Feedback
> > >> requested from ARM and PPC maintainers as to this change and what
> > >> flags, if any, need to be in the .pc file for DPDK on such
> > >> platforms. For example - is setting 'pkg_config_machine_args' to
> > >> 'machine_args' by default necessary behaviour?
> > >>
> > >
> > > Ping for further thoughts or input on this patch.
> 
> Armv8 has dedicated config(taken least cpu flags which supports all
> armv8) for this purpose config/arm/arm64_armv8_linux_gcc.
> So this change looks good to me. @Ruifeng Wang (Arm Technology China)
> Any comments?
> 

Agree. For distro build, only armv8-a is requested. The change looks fine.

Thanks,
Ruifeng
> 
> >
> > On initial inspection I don't see any additional value for PPC systems.
> >   Selection of a CPU through -mcpu implies a full ISA for that CPU,
> > including things like vector extensions, at least with respect to the
> > minimum supported POWER8 CPU (ISA 2.07) and later ISAs.  The values of
> > machine_args and pkg_config_machine_args should be identical in all
> > cases I can think of.
> >
> > If a third party OpenPOWER CPU comes along some time in the future
> > then the requirements may change.
> 
> 
> 
> 
> >
> > Dave

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Ruifeng Wang]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Ruifeng Wang
> Sent: Thursday, September 16, 2021 6:17 PM
> To: Jerin Jacob <jerinjacobk@gmail.com>; David Christensen
> <drc@linux.vnet.ibm.com>
> Cc: Bruce Richardson <bruce.richardson@intel.com>; dpdk-dev
> <dev@dpdk.org>; Luca Boccassi <bluca@debian.org>; David Marchand
> <david.marchand@redhat.com>; ian.stokes@intel.com; Ilya Maximets
> <i.maximets@ovn.org>; jerinj@marvell.com; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; Ferruh Yigit <ferruh.yigit@intel.com>; nd
> <nd@arm.com>
> Subject: Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch
> flag
> 
> > -----Original Message-----
> > From: Jerin Jacob <jerinjacobk@gmail.com>
> > Sent: Thursday, September 16, 2021 11:43 AM
> > To: David Christensen <drc@linux.vnet.ibm.com>
> > Cc: Bruce Richardson <bruce.richardson@intel.com>; dpdk-dev
> > <dev@dpdk.org>; Luca Boccassi <bluca@debian.org>; David Marchand
> > <david.marchand@redhat.com>; ian.stokes@intel.com; Ilya Maximets
> > <i.maximets@ovn.org>; jerinj@marvell.com; Ruifeng Wang
> > <Ruifeng.Wang@arm.com>; Honnappa Nagarahalli
> > <Honnappa.Nagarahalli@arm.com>; Ananyev, Konstantin
> > <konstantin.ananyev@intel.com>; Ferruh Yigit <ferruh.yigit@intel.com>
> > Subject: Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine
> > arch flag
> >
> > On Thu, Sep 16, 2021 at 2:53 AM David Christensen
> > <drc@linux.vnet.ibm.com>
> > wrote:
> > >
> > >
> > >
> > > On 9/15/21 9:28 AM, Bruce Richardson wrote:
> > > > On Fri, Dec 11, 2020 at 03:51:11PM +0000, Bruce Richardson wrote:
> > > >> Traditionally any apps built using DPDK had to support the same
> > > >> instruction sets as supported when the DPDK SDK itself was built,
> > > >> since that was "leaked" through to the end-app and DPDK headers
> > > >> via
> > > >> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over
> to
> > > >> meson for app build correctness the "-march=" flag was included
> > > >> in the pkg-config cflags output.
> > > >>
> > > >> However, since the DPDK-specific CPU flags are now obsolete, and
> > > >> we instead check directly for compiler-defined flags, we should
> > > >> no longer need to force the exact same architecture match in all
> > > >> cases. To faciliate such flexibility, a new
> > > >> pkg_config_machine_args array - which defaults to the existing
> > > >> machine_args array has been defined. The individual architectures
> > > >> - x86, arm and ppc - can choose if and how to override this value
> themselves.
> > > >>
> > > >> For x86, since SSE4.2 is the minimum instruction-set level needed
> > > >> to run DPDK, and since some header files assume that minimum
> > > >> level of instruction set support, we override the "-march=" value
> > > >> with "-
> > msse4"
> > > >> for the pkg-config file. This allows end applications to set
> > > >> their own "march" value while still ensuring valid DPDK compilation.
> > > >>
> > > >> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > > >> ---
> > > >>
> > > >> CC: Jerin Jacob <jerinj@marvell.com>
> > > >> CC: Ruifeng Wang <ruifeng.wang@arm.com>
> > > >> CC: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > > >> CC: David Christensen <drc@linux.vnet.ibm.com> for Feedback
> > > >> requested from ARM and PPC maintainers as to this change and what
> > > >> flags, if any, need to be in the .pc file for DPDK on such
> > > >> platforms. For example - is setting 'pkg_config_machine_args' to
> > > >> 'machine_args' by default necessary behaviour?
> > > >>
> > > >
> > > > Ping for further thoughts or input on this patch.
> >
> > Armv8 has dedicated config(taken least cpu flags which supports all
> > armv8) for this purpose config/arm/arm64_armv8_linux_gcc.
> > So this change looks good to me. @Ruifeng Wang (Arm Technology China)
> > Any comments?
> >
> 
> Agree. For distro build, only armv8-a is requested. The change looks fine.

This is fine if "cross-file" is provided when doing distro build. 
However, when "-Dmachine=default"/"-Dplatform=default" is used instead of "cross-file" to do distro build, current change in config/meson.build
will lead to " pkg_config_machine_args = -march=generic". This is because generic build is handled by subsequent arch specific config on Arm.

I think moving the change in config/meson.build down below line #307 subdir(arch_subdir) will address aforementioned issue. As by the time,
machine_args has been updated with proper value.

> 
> Thanks,
> Ruifeng
> >
> > >
> > > On initial inspection I don't see any additional value for PPC systems.
> > >   Selection of a CPU through -mcpu implies a full ISA for that CPU,
> > > including things like vector extensions, at least with respect to
> > > the minimum supported POWER8 CPU (ISA 2.07) and later ISAs.  The
> > > values of machine_args and pkg_config_machine_args should be
> > > identical in all cases I can think of.
> > >
> > > If a third party OpenPOWER CPU comes along some time in the future
> > > then the requirements may change.
> >
> >
> >
> >
> > >
> > > Dave

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Stephen Hemminger]

On Fri, 11 Dec 2020 15:51:11 +0000
Bruce Richardson <bruce.richardson@intel.com> wrote:

> Traditionally any apps built using DPDK had to support the same
> instruction sets as supported when the DPDK SDK itself was built, since
> that was "leaked" through to the end-app and DPDK headers via
> RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
> for app build correctness the "-march=" flag was included in the
> pkg-config cflags output.
> 
> However, since the DPDK-specific CPU flags are now obsolete, and we
> instead check directly for compiler-defined flags, we should no longer
> need to force the exact same architecture match in all cases. To
> faciliate such flexibility, a new pkg_config_machine_args array - which
> defaults to the existing machine_args array has been defined. The
> individual architectures - x86, arm and ppc - can choose if and how to
> override this value themselves.
> 
> For x86, since SSE4.2 is the minimum instruction-set level needed to run
> DPDK, and since some header files assume that minimum level of
> instruction set support, we override the "-march=" value with "-msse4"
> for the pkg-config file. This allows end applications to set their own
> "march" value while still ensuring valid DPDK compilation.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

This looks fine, and can see no negatives in the comments.
Could you rebase and resubmit a new version if still relevant?

Re: [dpdk-dev] [RFC PATCH] build/pkg-config: remove machine arch flag

[Bruce Richardson]

On Wed, Jun 14, 2023 at 12:33:10PM -0700, Stephen Hemminger wrote:
> On Fri, 11 Dec 2020 15:51:11 +0000
> Bruce Richardson <bruce.richardson@intel.com> wrote:
> 
> > Traditionally any apps built using DPDK had to support the same
> > instruction sets as supported when the DPDK SDK itself was built, since
> > that was "leaked" through to the end-app and DPDK headers via
> > RTE_MACHINE_CPUFLAG_* values. Therefore, when converting over to meson
> > for app build correctness the "-march=" flag was included in the
> > pkg-config cflags output.
> > 
> > However, since the DPDK-specific CPU flags are now obsolete, and we
> > instead check directly for compiler-defined flags, we should no longer
> > need to force the exact same architecture match in all cases. To
> > faciliate such flexibility, a new pkg_config_machine_args array - which
> > defaults to the existing machine_args array has been defined. The
> > individual architectures - x86, arm and ppc - can choose if and how to
> > override this value themselves.
> > 
> > For x86, since SSE4.2 is the minimum instruction-set level needed to run
> > DPDK, and since some header files assume that minimum level of
> > instruction set support, we override the "-march=" value with "-msse4"
> > for the pkg-config file. This allows end applications to set their own
> > "march" value while still ensuring valid DPDK compilation.
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> 
> This looks fine, and can see no negatives in the comments.
> Could you rebase and resubmit a new version if still relevant?
> 
There seemed to be a general lack of interest in it, sadly, so not sure
I'll resubmit.