[RFC,v2] build: add platform meson option

The current meson option 'machine' should only specify the ISA, which is
not sufficient for Arm, where setting ISA implies other setting as well.
Add a new meson option, 'platform', which differentiates the type of the
build (native/generic) and sets machine accordingly, unless the user
chooses to override it.
The 'machine' option also doesn't describe very well what it sets, so
introduce a new option 'cpu_instruction_set', but keep 'machine' for
backward compatibility.
These two new variables, taken together, achieve what 'machine' was
setting per architecture - setting the ISA in x86 build and setting
native/default 'build type' in aarch64 build - is now properly being set
for all architectures in a uniform manner.

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
---
 config/arm/meson.build        |  4 +--
 config/meson.build            | 47 +++++++++++++++++++++++++----------
 devtools/test-meson-builds.sh |  9 ++++---
 meson_options.txt             |  8 ++++--
 4 files changed, 47 insertions(+), 21 deletions(-)

Apologies, I meant to add David as well.

> -----Original Message-----
> From: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Sent: Monday, January 4, 2021 12:52 PM
> To: thomas@monjalon.net; bruce.richardson@intel.com;
> Honnappa.Nagarahalli@arm.com
> Cc: dev@dpdk.org; Juraj Linkeš <juraj.linkes@pantheon.tech>
> Subject: [RFC PATCH v2] build: add platform meson option
> 
> The current meson option 'machine' should only specify the ISA, which is not
> sufficient for Arm, where setting ISA implies other setting as well.
> Add a new meson option, 'platform', which differentiates the type of the build
> (native/generic) and sets machine accordingly, unless the user chooses to
> override it.
> The 'machine' option also doesn't describe very well what it sets, so introduce a
> new option 'cpu_instruction_set', but keep 'machine' for backward
> compatibility.
> These two new variables, taken together, achieve what 'machine' was setting
> per architecture - setting the ISA in x86 build and setting native/default 'build
> type' in aarch64 build - is now properly being set for all architectures in a
> uniform manner.
> 
> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> ---
>  config/arm/meson.build        |  4 +--
>  config/meson.build            | 47 +++++++++++++++++++++++++----------
>  devtools/test-meson-builds.sh |  9 ++++---
>  meson_options.txt             |  8 ++++--
>  4 files changed, 47 insertions(+), 21 deletions(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> 42b4e43c7..6b09a74a7 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -3,10 +3,10 @@
>  # Copyright(c) 2017 Cavium, Inc
> 
>  # for checking defines we need to use the correct compiler flags -march_opt = '-
> march=@0@'.format(machine)
> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> 
>  arm_force_native_march = false
> -arm_force_default_march = (machine == 'default')
> +arm_force_default_march = (platform == 'generic')
> 
>  flags_common_default = [
>  	# Accelarate rte_memcpy. Be sure to run unit test
> (memcpy_perf_autotest) diff --git a/config/meson.build b/config/meson.build
> index a3154e29c..647116513 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -63,42 +63,63 @@ if not is_windows
>  			pmd_subdir_opt)
>  endif
> 
> -# set the machine type and cflags for it
> +platform = get_option('platform')
> +
> +# set the cpu_instruction_set type and cflags for it
>  if meson.is_cross_build()
> -	machine = host_machine.cpu()
> +	cpu_instruction_set = host_machine.cpu()
>  else
> -	machine = get_option('machine')
> +	cpu_instruction_set = get_option('cpu_instruction_set')
> +	if get_option('machine') != 'auto'
> +		warning('The "machine" option is deprecated. ' +
> +		        'Please use "cpu_instruction_set" instead.')
> +		if cpu_instruction_set != 'auto'
> +			error('Setting both "machine" and ' +
> +			      '"cpu_instruction_set" is unsupported.')
> +		endif
> +		cpu_instruction_set = get_option('machine')
> +	endif
> +endif
> +
> +if platform == 'native'
> +	if cpu_instruction_set == 'auto'
> +		cpu_instruction_set = 'native'
> +	endif
> +elif platform == 'generic'
> +	if cpu_instruction_set == 'auto'
> +		cpu_instruction_set = 'default'
> +	endif
>  endif
> 
> -# machine type 'default' is special, it defaults to the per arch agreed common
> +if cpu_instruction_set == 'default'
> +# cpu_instruction_set type 'default' 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 == 'default'
>  	if host_machine.cpu_family().startswith('x86')
>  		# matches the old pre-meson build systems default
> -		machine = 'corei7'
> +		cpu_instruction_set = 'corei7'
>  	elif host_machine.cpu_family().startswith('arm')
> -		machine = 'armv7-a'
> +		cpu_instruction_set = 'armv7-a'
>  	elif host_machine.cpu_family().startswith('aarch')
>  		# arm64 manages defaults in config/arm/meson.build
> -		machine = 'default'
> +		cpu_instruction_set = 'default'
>  	elif host_machine.cpu_family().startswith('ppc')
> -		machine = 'power8'
> +		cpu_instruction_set = 'power8'
>  	endif
>  endif
> 
> -dpdk_conf.set('RTE_MACHINE', machine)
> +dpdk_conf.set('RTE_MACHINE', cpu_instruction_set)
>  machine_args = []
> 
>  # ppc64 does not support -march= at all, use -mcpu and -mtune for that  if
> host_machine.cpu_family().startswith('ppc')
> -	machine_args += '-mcpu=' + machine
> -	machine_args += '-mtune=' + machine
> +	machine_args += '-mcpu=' + cpu_instruction_set
> +	machine_args += '-mtune=' + cpu_instruction_set
>  else
> -	machine_args += '-march=' + machine
> +	machine_args += '-march=' + cpu_instruction_set
>  endif
> 
>  toolchain = cc.get_id()
> diff --git a/devtools/test-meson-builds.sh b/devtools/test-meson-builds.sh index
> 7280b7a93..33845d998 100755
> --- a/devtools/test-meson-builds.sh
> +++ b/devtools/test-meson-builds.sh
> @@ -211,11 +211,12 @@ done
>  # test compilation with minimal x86 instruction set  # Set the install path for
> libraries to "lib" explicitly to prevent problems  # with pkg-config prefixes if
> installed in "lib/x86_64-linux-gnu" later.
> -default_machine='nehalem'
> -if ! check_cc_flags "-march=$default_machine" ; then
> -	default_machine='corei7'
> +default_isa='nehalem'
> +if ! check_cc_flags "-march=$default_isa" ; then
> +	default_isa='corei7'
>  fi
> -build build-x86-default cc -Dlibdir=lib -Dmachine=$default_machine
> $use_shared
> +build build-x86-default cc -Dlibdir=lib -Dcpu_instruction_set=$default_isa \
> +      $use_shared
> 
>  # 32-bit with default compiler
>  if check_cc_flags '-m32' ; then
> diff --git a/meson_options.txt b/meson_options.txt index
> e384e6dbb..9db03a87d 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -1,5 +1,7 @@
>  # Please keep these options sorted alphabetically.
> 
> +option('cpu_instruction_set', type: 'string', value: 'auto',
> +	description: 'Set the target machine ISA (instruction set
> +architecture)/')
>  option('disable_drivers', type: 'string', value: '',
>  	description: 'Comma-separated list of drivers to explicitly disable.')
> option('drivers_install_subdir', type: 'string', value: 'dpdk/pmds-<VERSION>',
> @@ -20,14 +22,16 @@ option('kernel_dir', type: 'string', value: '',
>  	description: 'Path to the kernel for building kernel modules. Headers
> must be in $kernel_dir/build. Modules will be installed in
> $DEST_DIR/$kernel_dir/extra/dpdk.')
>  option('lib_musdk_dir', type: 'string', value: '',
>  	description: 'path to the MUSDK library installation directory') -
> option('machine', type: 'string', value: 'native',
> -	description: 'set the target machine type')
> +option('machine', type: 'string', value: 'auto',
> +	description: 'set the target machine type/ISA')
>  option('max_ethports', type: 'integer', value: 32,
>  	description: 'maximum number of Ethernet devices')
> option('max_lcores', type: 'integer', value: 128,
>  	description: 'maximum number of cores/threads supported by EAL')
> option('max_numa_nodes', type: 'integer', value: 4,
>  	description: 'maximum number of NUMA nodes supported by EAL')
> +option('platform', type: 'string', value: 'generic',
> +	description: 'Platform to build for, either "native" or "generic".')
>  option('enable_trace_fp', type: 'boolean', value: false,
>  	description: 'enable fast path trace points.')  option('tests', type:
> 'boolean', value: true,
> --
> 2.20.1

>> The current meson option 'machine' should only specify the ISA, which is not
>> sufficient for Arm, where setting ISA implies other setting as well.
>> Add a new meson option, 'platform', which differentiates the type of the build
>> (native/generic) and sets machine accordingly, unless the user chooses to
>> override it.
>> The 'machine' option also doesn't describe very well what it sets, so introduce a
>> new option 'cpu_instruction_set', but keep 'machine' for backward
>> compatibility.
>> These two new variables, taken together, achieve what 'machine' was setting
>> per architecture - setting the ISA in x86 build and setting native/default 'build
>> type' in aarch64 build - is now properly being set for all architectures in a
>> uniform manner.
>>
>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
>> ---
>>   config/arm/meson.build        |  4 +--
>>   config/meson.build            | 47 +++++++++++++++++++++++++----------
>>   devtools/test-meson-builds.sh |  9 ++++---
>>   meson_options.txt             |  8 ++++--
>>   4 files changed, 47 insertions(+), 21 deletions(-)
>>
>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
>> 42b4e43c7..6b09a74a7 100644
>> --- a/config/arm/meson.build
>> +++ b/config/arm/meson.build
>> @@ -3,10 +3,10 @@
>>   # Copyright(c) 2017 Cavium, Inc
>>
>>   # for checking defines we need to use the correct compiler flags -march_opt = '-
>> march=@0@'.format(machine)
>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
>>
>>   arm_force_native_march = false
>> -arm_force_default_march = (machine == 'default')
>> +arm_force_default_march = (platform == 'generic')
>>
>>   flags_common_default = [
>>   	# Accelarate rte_memcpy. Be sure to run unit test
>> (memcpy_perf_autotest) diff --git a/config/meson.build b/config/meson.build
>> index a3154e29c..647116513 100644
>> --- a/config/meson.build
>> +++ b/config/meson.build
>> @@ -63,42 +63,63 @@ if not is_windows
>>   			pmd_subdir_opt)
>>   endif
>>
>> -# set the machine type and cflags for it
>> +platform = get_option('platform')
>> +
>> +# set the cpu_instruction_set type and cflags for it
>>   if meson.is_cross_build()
>> -	machine = host_machine.cpu()
>> +	cpu_instruction_set = host_machine.cpu()
>>   else
>> -	machine = get_option('machine')
>> +	cpu_instruction_set = get_option('cpu_instruction_set')
>> +	if get_option('machine') != 'auto'
>> +		warning('The "machine" option is deprecated. ' +
>> +		        'Please use "cpu_instruction_set" instead.')
>> +		if cpu_instruction_set != 'auto'
>> +			error('Setting both "machine" and ' +
>> +			      '"cpu_instruction_set" is unsupported.')
>> +		endif
>> +		cpu_instruction_set = get_option('machine')
>> +	endif
>> +endif
>> +
>> +if platform == 'native'
>> +	if cpu_instruction_set == 'auto'
>> +		cpu_instruction_set = 'native'
>> +	endif
>> +elif platform == 'generic'
>> +	if cpu_instruction_set == 'auto'
>> +		cpu_instruction_set = 'default'
>> +	endif
>>   endif
>>
>> -# machine type 'default' is special, it defaults to the per arch agreed common
>> +if cpu_instruction_set == 'default'
>> +# cpu_instruction_set type 'default' 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 == 'default'
>>   	if host_machine.cpu_family().startswith('x86')
>>   		# matches the old pre-meson build systems default
>> -		machine = 'corei7'
>> +		cpu_instruction_set = 'corei7'
>>   	elif host_machine.cpu_family().startswith('arm')
>> -		machine = 'armv7-a'
>> +		cpu_instruction_set = 'armv7-a'
>>   	elif host_machine.cpu_family().startswith('aarch')
>>   		# arm64 manages defaults in config/arm/meson.build
>> -		machine = 'default'
>> +		cpu_instruction_set = 'default'
>>   	elif host_machine.cpu_family().startswith('ppc')
>> -		machine = 'power8'
>> +		cpu_instruction_set = 'power8'
>>   	endif
>>   endif

This change forces the build on a P9 system to use the P8 instruction 
set.  Prior to this change the "native" machine type was used which 
resulted in P9 instructions when built on a P9 system.  How do I force 
the build to use the power9 instruction set in this case?

Dave

On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > > The current meson option 'machine' should only specify the ISA, which is not
> > > sufficient for Arm, where setting ISA implies other setting as well.
> > > Add a new meson option, 'platform', which differentiates the type of the build
> > > (native/generic) and sets machine accordingly, unless the user chooses to
> > > override it.
> > > The 'machine' option also doesn't describe very well what it sets, so introduce a
> > > new option 'cpu_instruction_set', but keep 'machine' for backward
> > > compatibility.
> > > These two new variables, taken together, achieve what 'machine' was setting
> > > per architecture - setting the ISA in x86 build and setting native/default 'build
> > > type' in aarch64 build - is now properly being set for all architectures in a
> > > uniform manner.
> > > 
> > > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > ---
> > >   config/arm/meson.build        |  4 +--
> > >   config/meson.build            | 47 +++++++++++++++++++++++++----------
> > >   devtools/test-meson-builds.sh |  9 ++++---
> > >   meson_options.txt             |  8 ++++--
> > >   4 files changed, 47 insertions(+), 21 deletions(-)
> > > 
> > > diff --git a/config/arm/meson.build b/config/arm/meson.build index
> > > 42b4e43c7..6b09a74a7 100644
> > > --- a/config/arm/meson.build
> > > +++ b/config/arm/meson.build
> > > @@ -3,10 +3,10 @@
> > >   # Copyright(c) 2017 Cavium, Inc
> > > 
> > >   # for checking defines we need to use the correct compiler flags -march_opt = '-
> > > march=@0@'.format(machine)
> > > +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > > 
> > >   arm_force_native_march = false
> > > -arm_force_default_march = (machine == 'default')
> > > +arm_force_default_march = (platform == 'generic')
> > > 
> > >   flags_common_default = [
> > >   	# Accelarate rte_memcpy. Be sure to run unit test
> > > (memcpy_perf_autotest) diff --git a/config/meson.build b/config/meson.build
> > > index a3154e29c..647116513 100644
> > > --- a/config/meson.build
> > > +++ b/config/meson.build
> > > @@ -63,42 +63,63 @@ if not is_windows
> > >   			pmd_subdir_opt)
> > >   endif
> > > 
> > > -# set the machine type and cflags for it
> > > +platform = get_option('platform')
> > > +
> > > +# set the cpu_instruction_set type and cflags for it
> > >   if meson.is_cross_build()
> > > -	machine = host_machine.cpu()
> > > +	cpu_instruction_set = host_machine.cpu()
> > >   else
> > > -	machine = get_option('machine')
> > > +	cpu_instruction_set = get_option('cpu_instruction_set')
> > > +	if get_option('machine') != 'auto'
> > > +		warning('The "machine" option is deprecated. ' +
> > > +		        'Please use "cpu_instruction_set" instead.')
> > > +		if cpu_instruction_set != 'auto'
> > > +			error('Setting both "machine" and ' +
> > > +			      '"cpu_instruction_set" is unsupported.')
> > > +		endif
> > > +		cpu_instruction_set = get_option('machine')
> > > +	endif
> > > +endif
> > > +
> > > +if platform == 'native'
> > > +	if cpu_instruction_set == 'auto'
> > > +		cpu_instruction_set = 'native'
> > > +	endif
> > > +elif platform == 'generic'
> > > +	if cpu_instruction_set == 'auto'
> > > +		cpu_instruction_set = 'default'
> > > +	endif
> > >   endif
> > > 
> > > -# machine type 'default' is special, it defaults to the per arch agreed common
> > > +if cpu_instruction_set == 'default'
> > > +# cpu_instruction_set type 'default' 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 == 'default'
> > >   	if host_machine.cpu_family().startswith('x86')
> > >   		# matches the old pre-meson build systems default
> > > -		machine = 'corei7'
> > > +		cpu_instruction_set = 'corei7'
> > >   	elif host_machine.cpu_family().startswith('arm')
> > > -		machine = 'armv7-a'
> > > +		cpu_instruction_set = 'armv7-a'
> > >   	elif host_machine.cpu_family().startswith('aarch')
> > >   		# arm64 manages defaults in config/arm/meson.build
> > > -		machine = 'default'
> > > +		cpu_instruction_set = 'default'
> > >   	elif host_machine.cpu_family().startswith('ppc')
> > > -		machine = 'power8'
> > > +		cpu_instruction_set = 'power8'
> > >   	endif
> > >   endif
> 
> This change forces the build on a P9 system to use the P8 instruction set.
> Prior to this change the "native" machine type was used which resulted in P9
> instructions when built on a P9 system.  How do I force the build to use the
> power9 instruction set in this case?
> 
> Dave

From looking at the patch, setting the "platform" to "native", or the
instruction_set to "native" should do this.
While I consider generic builds a good thing, I wonder if there is an
expectation that "native" is always the default build type for DPDK builds?

/Bruce

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Wednesday, January 6, 2021 3:43 PM
> To: David Christensen <drc@linux.vnet.ibm.com>
> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>; thomas@monjalon.net;
> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> Subject: Re: [RFC PATCH v2] build: add platform meson option
> 
> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > > > The current meson option 'machine' should only specify the ISA,
> > > > which is not sufficient for Arm, where setting ISA implies other setting as
> well.
> > > > Add a new meson option, 'platform', which differentiates the type
> > > > of the build
> > > > (native/generic) and sets machine accordingly, unless the user
> > > > chooses to override it.
> > > > The 'machine' option also doesn't describe very well what it sets,
> > > > so introduce a new option 'cpu_instruction_set', but keep
> > > > 'machine' for backward compatibility.
> > > > These two new variables, taken together, achieve what 'machine'
> > > > was setting per architecture - setting the ISA in x86 build and
> > > > setting native/default 'build type' in aarch64 build - is now
> > > > properly being set for all architectures in a uniform manner.
> > > >
> > > > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > > ---
> > > >   config/arm/meson.build        |  4 +--
> > > >   config/meson.build            | 47 +++++++++++++++++++++++++----------
> > > >   devtools/test-meson-builds.sh |  9 ++++---
> > > >   meson_options.txt             |  8 ++++--
> > > >   4 files changed, 47 insertions(+), 21 deletions(-)
> > > >
> > > > diff --git a/config/arm/meson.build b/config/arm/meson.build index
> > > > 42b4e43c7..6b09a74a7 100644
> > > > --- a/config/arm/meson.build
> > > > +++ b/config/arm/meson.build
> > > > @@ -3,10 +3,10 @@
> > > >   # Copyright(c) 2017 Cavium, Inc
> > > >
> > > >   # for checking defines we need to use the correct compiler flags
> > > > -march_opt = '-
> > > > march=@0@'.format(machine)
> > > > +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > > >
> > > >   arm_force_native_march = false
> > > > -arm_force_default_march = (machine == 'default')
> > > > +arm_force_default_march = (platform == 'generic')
> > > >
> > > >   flags_common_default = [
> > > >   	# Accelarate rte_memcpy. Be sure to run unit test
> > > > (memcpy_perf_autotest) diff --git a/config/meson.build
> > > > b/config/meson.build index a3154e29c..647116513 100644
> > > > --- a/config/meson.build
> > > > +++ b/config/meson.build
> > > > @@ -63,42 +63,63 @@ if not is_windows
> > > >   			pmd_subdir_opt)
> > > >   endif
> > > >
> > > > -# set the machine type and cflags for it
> > > > +platform = get_option('platform')
> > > > +
> > > > +# set the cpu_instruction_set type and cflags for it
> > > >   if meson.is_cross_build()
> > > > -	machine = host_machine.cpu()
> > > > +	cpu_instruction_set = host_machine.cpu()
> > > >   else
> > > > -	machine = get_option('machine')
> > > > +	cpu_instruction_set = get_option('cpu_instruction_set')
> > > > +	if get_option('machine') != 'auto'
> > > > +		warning('The "machine" option is deprecated. ' +
> > > > +		        'Please use "cpu_instruction_set" instead.')
> > > > +		if cpu_instruction_set != 'auto'
> > > > +			error('Setting both "machine" and ' +
> > > > +			      '"cpu_instruction_set" is unsupported.')
> > > > +		endif
> > > > +		cpu_instruction_set = get_option('machine')
> > > > +	endif
> > > > +endif
> > > > +
> > > > +if platform == 'native'
> > > > +	if cpu_instruction_set == 'auto'
> > > > +		cpu_instruction_set = 'native'
> > > > +	endif
> > > > +elif platform == 'generic'
> > > > +	if cpu_instruction_set == 'auto'
> > > > +		cpu_instruction_set = 'default'
> > > > +	endif
> > > >   endif
> > > >
> > > > -# machine type 'default' is special, it defaults to the per arch
> > > > agreed common
> > > > +if cpu_instruction_set == 'default'
> > > > +# cpu_instruction_set type 'default' 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 == 'default'
> > > >   	if host_machine.cpu_family().startswith('x86')
> > > >   		# matches the old pre-meson build systems default
> > > > -		machine = 'corei7'
> > > > +		cpu_instruction_set = 'corei7'
> > > >   	elif host_machine.cpu_family().startswith('arm')
> > > > -		machine = 'armv7-a'
> > > > +		cpu_instruction_set = 'armv7-a'
> > > >   	elif host_machine.cpu_family().startswith('aarch')
> > > >   		# arm64 manages defaults in config/arm/meson.build
> > > > -		machine = 'default'
> > > > +		cpu_instruction_set = 'default'
> > > >   	elif host_machine.cpu_family().startswith('ppc')
> > > > -		machine = 'power8'
> > > > +		cpu_instruction_set = 'power8'
> > > >   	endif
> > > >   endif
> >
> > This change forces the build on a P9 system to use the P8 instruction set.
> > Prior to this change the "native" machine type was used which resulted
> > in P9 instructions when built on a P9 system.  How do I force the
> > build to use the
> > power9 instruction set in this case?
> >
> > Dave
> 
> From looking at the patch, setting the "platform" to "native", or the
> instruction_set to "native" should do this.
> While I consider generic builds a good thing, I wonder if there is an expectation
> that "native" is always the default build type for DPDK builds?
> 
> /Bruce

I left this patch alone so that people could chime in, but noone did, so let's try to find some agreeable solution.

My current thoughts are as such:
The platform parameter specifies a set of DPDK options that will be used. This is what arm uses for its builds, x86 and ppc don't use this.
The cpu_instruction_set sets just one configuration among the "platform" configuration set.
We want the build to work on most machines of the machine architecture. That implies platform=generic (as in use config options that will work on everything of that architecture) and cpu_instruction_set=generic (as in use ISA that will work on all cpus of the build machine architecture).
Setting cpu_instruction_set=generic changes the build without cmdline options for ppc. Thus, the expectation may be that cpu_instruction_set should be native by default.

For arm, cpu_instruction_set is ignored (and thus the value doen't matter), since we can't use that without other config options (e.g. DPDK config for an SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an invalid cpu_instuction_set). That means the only relevant parameter for Arm is platform and if we want to have a build usable on most machines of the build type, we have to use platform=generic.

For x86 and ppc, there's no difference between native and generic platform (as it's a new argument, the purpose of which is to differentiate DPDK config across platforms, which doesn't exist for x86 and ppc - DPDK config is the same (correct me if I'm wrong)).

So it basically boils down to what should be the default value of cpu_instruction_set when platform=generic (for platform=native, it's obviously native):
1. cpu_instruction_set=native, this would preserve the current behavior, but we won't use the 'auto' default. I think we can fall back to this if we don't agree on anything better.
2. cpu_instruction_set=auto, the same as cpu_instruction_set=generic,
3. cpu_instruction_set=generic, this changes behavior for ppc builds, but we may be able to remedy this:
Similarly to arm (arm is using platform for this, but the idea is the same), if cpu_instruction_set is generic, we can do some discovery for pcc and set the ISA accordingly (either power8 or power9). If I understand it correctly, power8 is a different architecture from power9 (I could be wrong on this), so this is desirable. There's some logic in config/ppc/meson.build, but it doesn't seem sufficient as a discovery mechanism between power8/power9.

I like 3 if we can find a way to discover power8/power9 ppc (that way we would be able to use cpu_instruction_set=auto), if not, we should probably go with 1 (in which case we can't use cpu_instruction_set=auto).

Or maybe we're overthingking this and we really should go with 1. What's (or should be) the difference between cpu_instruction_set=generic and cpu_instruction_set=native for x86 and ppc?

On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> 
> 
>> -----Original Message-----
>> From: Bruce Richardson <bruce.richardson@intel.com>
>> Sent: Wednesday, January 6, 2021 3:43 PM
>> To: David Christensen <drc@linux.vnet.ibm.com>
>> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>; thomas@monjalon.net;
>> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
>> Subject: Re: [RFC PATCH v2] build: add platform meson option
>>
>> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
>>>>> The current meson option 'machine' should only specify the ISA,
>>>>> which is not sufficient for Arm, where setting ISA implies other setting as
>> well.
>>>>> Add a new meson option, 'platform', which differentiates the type
>>>>> of the build
>>>>> (native/generic) and sets machine accordingly, unless the user
>>>>> chooses to override it.
>>>>> The 'machine' option also doesn't describe very well what it sets,
>>>>> so introduce a new option 'cpu_instruction_set', but keep
>>>>> 'machine' for backward compatibility.
>>>>> These two new variables, taken together, achieve what 'machine'
>>>>> was setting per architecture - setting the ISA in x86 build and
>>>>> setting native/default 'build type' in aarch64 build - is now
>>>>> properly being set for all architectures in a uniform manner.
>>>>>
>>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
>>>>> ---
>>>>>    config/arm/meson.build        |  4 +--
>>>>>    config/meson.build            | 47 +++++++++++++++++++++++++----------
>>>>>    devtools/test-meson-builds.sh |  9 ++++---
>>>>>    meson_options.txt             |  8 ++++--
>>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
>>>>>
>>>>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
>>>>> 42b4e43c7..6b09a74a7 100644
>>>>> --- a/config/arm/meson.build
>>>>> +++ b/config/arm/meson.build
>>>>> @@ -3,10 +3,10 @@
>>>>>    # Copyright(c) 2017 Cavium, Inc
>>>>>
>>>>>    # for checking defines we need to use the correct compiler flags
>>>>> -march_opt = '-
>>>>> march=@0@'.format(machine)
>>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
>>>>>
>>>>>    arm_force_native_march = false
>>>>> -arm_force_default_march = (machine == 'default')
>>>>> +arm_force_default_march = (platform == 'generic')
>>>>>
>>>>>    flags_common_default = [
>>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
>>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
>>>>> b/config/meson.build index a3154e29c..647116513 100644
>>>>> --- a/config/meson.build
>>>>> +++ b/config/meson.build
>>>>> @@ -63,42 +63,63 @@ if not is_windows
>>>>>    			pmd_subdir_opt)
>>>>>    endif
>>>>>
>>>>> -# set the machine type and cflags for it
>>>>> +platform = get_option('platform')
>>>>> +
>>>>> +# set the cpu_instruction_set type and cflags for it
>>>>>    if meson.is_cross_build()
>>>>> -	machine = host_machine.cpu()
>>>>> +	cpu_instruction_set = host_machine.cpu()
>>>>>    else
>>>>> -	machine = get_option('machine')
>>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
>>>>> +	if get_option('machine') != 'auto'
>>>>> +		warning('The "machine" option is deprecated. ' +
>>>>> +		        'Please use "cpu_instruction_set" instead.')
>>>>> +		if cpu_instruction_set != 'auto'
>>>>> +			error('Setting both "machine" and ' +
>>>>> +			      '"cpu_instruction_set" is unsupported.')
>>>>> +		endif
>>>>> +		cpu_instruction_set = get_option('machine')
>>>>> +	endif
>>>>> +endif
>>>>> +
>>>>> +if platform == 'native'
>>>>> +	if cpu_instruction_set == 'auto'
>>>>> +		cpu_instruction_set = 'native'
>>>>> +	endif
>>>>> +elif platform == 'generic'
>>>>> +	if cpu_instruction_set == 'auto'
>>>>> +		cpu_instruction_set = 'default'
>>>>> +	endif
>>>>>    endif
>>>>>
>>>>> -# machine type 'default' is special, it defaults to the per arch
>>>>> agreed common
>>>>> +if cpu_instruction_set == 'default'
>>>>> +# cpu_instruction_set type 'default' 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 == 'default'
>>>>>    	if host_machine.cpu_family().startswith('x86')
>>>>>    		# matches the old pre-meson build systems default
>>>>> -		machine = 'corei7'
>>>>> +		cpu_instruction_set = 'corei7'
>>>>>    	elif host_machine.cpu_family().startswith('arm')
>>>>> -		machine = 'armv7-a'
>>>>> +		cpu_instruction_set = 'armv7-a'
>>>>>    	elif host_machine.cpu_family().startswith('aarch')
>>>>>    		# arm64 manages defaults in config/arm/meson.build
>>>>> -		machine = 'default'
>>>>> +		cpu_instruction_set = 'default'
>>>>>    	elif host_machine.cpu_family().startswith('ppc')
>>>>> -		machine = 'power8'
>>>>> +		cpu_instruction_set = 'power8'
>>>>>    	endif
>>>>>    endif
>>>
>>> This change forces the build on a P9 system to use the P8 instruction set.
>>> Prior to this change the "native" machine type was used which resulted
>>> in P9 instructions when built on a P9 system.  How do I force the
>>> build to use the
>>> power9 instruction set in this case?
>>>
>>> Dave
>>
>>  From looking at the patch, setting the "platform" to "native", or the
>> instruction_set to "native" should do this.
>> While I consider generic builds a good thing, I wonder if there is an expectation
>> that "native" is always the default build type for DPDK builds?
>>
>> /Bruce
> 
> I left this patch alone so that people could chime in, but noone did, so let's try to find some agreeable solution.
> 
> My current thoughts are as such:
> The platform parameter specifies a set of DPDK options that will be used. This is what arm uses for its builds, x86 and ppc don't use this.
> The cpu_instruction_set sets just one configuration among the "platform" configuration set.
> We want the build to work on most machines of the machine architecture. That implies platform=generic (as in use config options that will work on everything of that architecture) and cpu_instruction_set=generic (as in use ISA that will work on all cpus of the build machine architecture).
> Setting cpu_instruction_set=generic changes the build without cmdline options for ppc. Thus, the expectation may be that cpu_instruction_set should be native by default.
> 
> For arm, cpu_instruction_set is ignored (and thus the value doen't matter), since we can't use that without other config options (e.g. DPDK config for an SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an invalid cpu_instuction_set). That means the only relevant parameter for Arm is platform and if we want to have a build usable on most machines of the build type, we have to use platform=generic.
> 
> For x86 and ppc, there's no difference between native and generic platform (as it's a new argument, the purpose of which is to differentiate DPDK config across platforms, which doesn't exist for x86 and ppc - DPDK config is the same (correct me if I'm wrong)).
> 
> So it basically boils down to what should be the default value of cpu_instruction_set when platform=generic (for platform=native, it's obviously native):
> 1. cpu_instruction_set=native, this would preserve the current behavior, but we won't use the 'auto' default. I think we can fall back to this if we don't agree on anything better.
> 2. cpu_instruction_set=auto, the same as cpu_instruction_set=generic,
> 3. cpu_instruction_set=generic, this changes behavior for ppc builds, but we may be able to remedy this:
> Similarly to arm (arm is using platform for this, but the idea is the same), if cpu_instruction_set is generic, we can do some discovery for pcc and set the ISA accordingly (either power8 or power9). If I understand it correctly, power8 is a different architecture from power9 (I could be wrong on this), so this is desirable. There's some logic in config/ppc/meson.build, but it doesn't seem sufficient as a discovery mechanism between power8/power9.

POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA v3.0), so 
setting cpu_instruction_set to GENERIC is a reasonable option. POWER10 
CPUs (Power ISA v3.1) are around the corner so I want to make sure 
developers can tune the application for the platform as easily as 
possible.  I'm fine with supporting GENERIC, just need clear 
instructions on how to build for a particular ISA.

Dave

> -----Original Message-----
> From: David Christensen <drc@linux.vnet.ibm.com>
> Sent: Monday, February 22, 2021 10:25 PM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>; Bruce Richardson
> <bruce.richardson@intel.com>
> Cc: thomas@monjalon.net; Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> Subject: Re: [RFC PATCH v2] build: add platform meson option
> 
> 
> 
> On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> >
> >
> >> -----Original Message-----
> >> From: Bruce Richardson <bruce.richardson@intel.com>
> >> Sent: Wednesday, January 6, 2021 3:43 PM
> >> To: David Christensen <drc@linux.vnet.ibm.com>
> >> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>; thomas@monjalon.net;
> >> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> >> Subject: Re: [RFC PATCH v2] build: add platform meson option
> >>
> >> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> >>>>> The current meson option 'machine' should only specify the ISA,
> >>>>> which is not sufficient for Arm, where setting ISA implies other
> >>>>> setting as
> >> well.
> >>>>> Add a new meson option, 'platform', which differentiates the type
> >>>>> of the build
> >>>>> (native/generic) and sets machine accordingly, unless the user
> >>>>> chooses to override it.
> >>>>> The 'machine' option also doesn't describe very well what it sets,
> >>>>> so introduce a new option 'cpu_instruction_set', but keep
> >>>>> 'machine' for backward compatibility.
> >>>>> These two new variables, taken together, achieve what 'machine'
> >>>>> was setting per architecture - setting the ISA in x86 build and
> >>>>> setting native/default 'build type' in aarch64 build - is now
> >>>>> properly being set for all architectures in a uniform manner.
> >>>>>
> >>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> >>>>> ---
> >>>>>    config/arm/meson.build        |  4 +--
> >>>>>    config/meson.build            | 47 +++++++++++++++++++++++++----------
> >>>>>    devtools/test-meson-builds.sh |  9 ++++---
> >>>>>    meson_options.txt             |  8 ++++--
> >>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
> >>>>>
> >>>>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> >>>>> 42b4e43c7..6b09a74a7 100644
> >>>>> --- a/config/arm/meson.build
> >>>>> +++ b/config/arm/meson.build
> >>>>> @@ -3,10 +3,10 @@
> >>>>>    # Copyright(c) 2017 Cavium, Inc
> >>>>>
> >>>>>    # for checking defines we need to use the correct compiler
> >>>>> flags -march_opt = '-
> >>>>> march=@0@'.format(machine)
> >>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> >>>>>
> >>>>>    arm_force_native_march = false
> >>>>> -arm_force_default_march = (machine == 'default')
> >>>>> +arm_force_default_march = (platform == 'generic')
> >>>>>
> >>>>>    flags_common_default = [
> >>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
> >>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
> >>>>> b/config/meson.build index a3154e29c..647116513 100644
> >>>>> --- a/config/meson.build
> >>>>> +++ b/config/meson.build
> >>>>> @@ -63,42 +63,63 @@ if not is_windows
> >>>>>    			pmd_subdir_opt)
> >>>>>    endif
> >>>>>
> >>>>> -# set the machine type and cflags for it
> >>>>> +platform = get_option('platform')
> >>>>> +
> >>>>> +# set the cpu_instruction_set type and cflags for it
> >>>>>    if meson.is_cross_build()
> >>>>> -	machine = host_machine.cpu()
> >>>>> +	cpu_instruction_set = host_machine.cpu()
> >>>>>    else
> >>>>> -	machine = get_option('machine')
> >>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
> >>>>> +	if get_option('machine') != 'auto'
> >>>>> +		warning('The "machine" option is deprecated. ' +
> >>>>> +		        'Please use "cpu_instruction_set" instead.')
> >>>>> +		if cpu_instruction_set != 'auto'
> >>>>> +			error('Setting both "machine" and ' +
> >>>>> +			      '"cpu_instruction_set" is unsupported.')
> >>>>> +		endif
> >>>>> +		cpu_instruction_set = get_option('machine')
> >>>>> +	endif
> >>>>> +endif
> >>>>> +
> >>>>> +if platform == 'native'
> >>>>> +	if cpu_instruction_set == 'auto'
> >>>>> +		cpu_instruction_set = 'native'
> >>>>> +	endif
> >>>>> +elif platform == 'generic'
> >>>>> +	if cpu_instruction_set == 'auto'
> >>>>> +		cpu_instruction_set = 'default'
> >>>>> +	endif
> >>>>>    endif
> >>>>>
> >>>>> -# machine type 'default' is special, it defaults to the per arch
> >>>>> agreed common
> >>>>> +if cpu_instruction_set == 'default'
> >>>>> +# cpu_instruction_set type 'default' 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 == 'default'
> >>>>>    	if host_machine.cpu_family().startswith('x86')
> >>>>>    		# matches the old pre-meson build systems default
> >>>>> -		machine = 'corei7'
> >>>>> +		cpu_instruction_set = 'corei7'
> >>>>>    	elif host_machine.cpu_family().startswith('arm')
> >>>>> -		machine = 'armv7-a'
> >>>>> +		cpu_instruction_set = 'armv7-a'
> >>>>>    	elif host_machine.cpu_family().startswith('aarch')
> >>>>>    		# arm64 manages defaults in config/arm/meson.build
> >>>>> -		machine = 'default'
> >>>>> +		cpu_instruction_set = 'default'
> >>>>>    	elif host_machine.cpu_family().startswith('ppc')
> >>>>> -		machine = 'power8'
> >>>>> +		cpu_instruction_set = 'power8'
> >>>>>    	endif
> >>>>>    endif
> >>>
> >>> This change forces the build on a P9 system to use the P8 instruction set.
> >>> Prior to this change the "native" machine type was used which
> >>> resulted in P9 instructions when built on a P9 system.  How do I
> >>> force the build to use the
> >>> power9 instruction set in this case?
> >>>
> >>> Dave
> >>
> >>  From looking at the patch, setting the "platform" to "native", or
> >> the instruction_set to "native" should do this.
> >> While I consider generic builds a good thing, I wonder if there is an
> >> expectation that "native" is always the default build type for DPDK builds?
> >>
> >> /Bruce
> >
> > I left this patch alone so that people could chime in, but noone did, so let's try
> to find some agreeable solution.
> >
> > My current thoughts are as such:
> > The platform parameter specifies a set of DPDK options that will be used. This
> is what arm uses for its builds, x86 and ppc don't use this.
> > The cpu_instruction_set sets just one configuration among the "platform"
> configuration set.
> > We want the build to work on most machines of the machine architecture.
> That implies platform=generic (as in use config options that will work on
> everything of that architecture) and cpu_instruction_set=generic (as in use ISA
> that will work on all cpus of the build machine architecture).
> > Setting cpu_instruction_set=generic changes the build without cmdline options
> for ppc. Thus, the expectation may be that cpu_instruction_set should be native
> by default.
> >
> > For arm, cpu_instruction_set is ignored (and thus the value doen't matter),
> since we can't use that without other config options (e.g. DPDK config for an
> SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an invalid
> cpu_instuction_set). That means the only relevant parameter for Arm is platform
> and if we want to have a build usable on most machines of the build type, we
> have to use platform=generic.
> >
> > For x86 and ppc, there's no difference between native and generic platform (as
> it's a new argument, the purpose of which is to differentiate DPDK config across
> platforms, which doesn't exist for x86 and ppc - DPDK config is the same (correct
> me if I'm wrong)).
> >
> > So it basically boils down to what should be the default value of
> cpu_instruction_set when platform=generic (for platform=native, it's obviously
> native):
> > 1. cpu_instruction_set=native, this would preserve the current behavior, but
> we won't use the 'auto' default. I think we can fall back to this if we don't agree
> on anything better.
> > 2. cpu_instruction_set=auto, the same as cpu_instruction_set=generic,
> > 3. cpu_instruction_set=generic, this changes behavior for ppc builds, but we
> may be able to remedy this:
> > Similarly to arm (arm is using platform for this, but the idea is the same), if
> cpu_instruction_set is generic, we can do some discovery for pcc and set the ISA
> accordingly (either power8 or power9). If I understand it correctly, power8 is a
> different architecture from power9 (I could be wrong on this), so this is
> desirable. There's some logic in config/ppc/meson.build, but it doesn't seem
> sufficient as a discovery mechanism between power8/power9.
> 
> POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA v3.0), so
> setting cpu_instruction_set to GENERIC is a reasonable option. POWER10 CPUs
> (Power ISA v3.1) are around the corner so I want to make sure developers can
> tune the application for the platform as easily as possible.  I'm fine with
> supporting GENERIC, just need clear instructions on how to build for a particular
> ISA.
> 

That's good to hear. Setting cpu_instruction_set will set the ISA.

We'll need to document the behavior properly, but I'm not sure where - Bruce? Seems like meson_options.txt doesn't have enough room for that.

The default bahavior is the ISA will be set according to the platform parameter. If cpu_instruction_set is specified, that value will be used.

> Dave

On Tue, Feb 23, 2021 at 08:45:09AM +0000, Juraj Linkeš wrote:
> 
> 
> > -----Original Message-----
> > From: David Christensen <drc@linux.vnet.ibm.com>
> > Sent: Monday, February 22, 2021 10:25 PM
> > To: Juraj Linkeš <juraj.linkes@pantheon.tech>; Bruce Richardson
> > <bruce.richardson@intel.com>
> > Cc: thomas@monjalon.net; Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > 
> > 
> > 
> > On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> > >
> > >
> > >> -----Original Message-----
> > >> From: Bruce Richardson <bruce.richardson@intel.com>
> > >> Sent: Wednesday, January 6, 2021 3:43 PM
> > >> To: David Christensen <drc@linux.vnet.ibm.com>
> > >> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>; thomas@monjalon.net;
> > >> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > >> Subject: Re: [RFC PATCH v2] build: add platform meson option
> > >>
> > >> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > >>>>> The current meson option 'machine' should only specify the ISA,
> > >>>>> which is not sufficient for Arm, where setting ISA implies other
> > >>>>> setting as
> > >> well.
> > >>>>> Add a new meson option, 'platform', which differentiates the type
> > >>>>> of the build
> > >>>>> (native/generic) and sets machine accordingly, unless the user
> > >>>>> chooses to override it.
> > >>>>> The 'machine' option also doesn't describe very well what it sets,
> > >>>>> so introduce a new option 'cpu_instruction_set', but keep
> > >>>>> 'machine' for backward compatibility.
> > >>>>> These two new variables, taken together, achieve what 'machine'
> > >>>>> was setting per architecture - setting the ISA in x86 build and
> > >>>>> setting native/default 'build type' in aarch64 build - is now
> > >>>>> properly being set for all architectures in a uniform manner.
> > >>>>>
> > >>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > >>>>> ---
> > >>>>>    config/arm/meson.build        |  4 +--
> > >>>>>    config/meson.build            | 47 +++++++++++++++++++++++++----------
> > >>>>>    devtools/test-meson-builds.sh |  9 ++++---
> > >>>>>    meson_options.txt             |  8 ++++--
> > >>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
> > >>>>>
> > >>>>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> > >>>>> 42b4e43c7..6b09a74a7 100644
> > >>>>> --- a/config/arm/meson.build
> > >>>>> +++ b/config/arm/meson.build
> > >>>>> @@ -3,10 +3,10 @@
> > >>>>>    # Copyright(c) 2017 Cavium, Inc
> > >>>>>
> > >>>>>    # for checking defines we need to use the correct compiler
> > >>>>> flags -march_opt = '-
> > >>>>> march=@0@'.format(machine)
> > >>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > >>>>>
> > >>>>>    arm_force_native_march = false
> > >>>>> -arm_force_default_march = (machine == 'default')
> > >>>>> +arm_force_default_march = (platform == 'generic')
> > >>>>>
> > >>>>>    flags_common_default = [
> > >>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
> > >>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
> > >>>>> b/config/meson.build index a3154e29c..647116513 100644
> > >>>>> --- a/config/meson.build
> > >>>>> +++ b/config/meson.build
> > >>>>> @@ -63,42 +63,63 @@ if not is_windows
> > >>>>>    			pmd_subdir_opt)
> > >>>>>    endif
> > >>>>>
> > >>>>> -# set the machine type and cflags for it
> > >>>>> +platform = get_option('platform')
> > >>>>> +
> > >>>>> +# set the cpu_instruction_set type and cflags for it
> > >>>>>    if meson.is_cross_build()
> > >>>>> -	machine = host_machine.cpu()
> > >>>>> +	cpu_instruction_set = host_machine.cpu()
> > >>>>>    else
> > >>>>> -	machine = get_option('machine')
> > >>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
> > >>>>> +	if get_option('machine') != 'auto'
> > >>>>> +		warning('The "machine" option is deprecated. ' +
> > >>>>> +		        'Please use "cpu_instruction_set" instead.')
> > >>>>> +		if cpu_instruction_set != 'auto'
> > >>>>> +			error('Setting both "machine" and ' +
> > >>>>> +			      '"cpu_instruction_set" is unsupported.')
> > >>>>> +		endif
> > >>>>> +		cpu_instruction_set = get_option('machine')
> > >>>>> +	endif
> > >>>>> +endif
> > >>>>> +
> > >>>>> +if platform == 'native'
> > >>>>> +	if cpu_instruction_set == 'auto'
> > >>>>> +		cpu_instruction_set = 'native'
> > >>>>> +	endif
> > >>>>> +elif platform == 'generic'
> > >>>>> +	if cpu_instruction_set == 'auto'
> > >>>>> +		cpu_instruction_set = 'default'
> > >>>>> +	endif
> > >>>>>    endif
> > >>>>>
> > >>>>> -# machine type 'default' is special, it defaults to the per arch
> > >>>>> agreed common
> > >>>>> +if cpu_instruction_set == 'default'
> > >>>>> +# cpu_instruction_set type 'default' 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 == 'default'
> > >>>>>    	if host_machine.cpu_family().startswith('x86')
> > >>>>>    		# matches the old pre-meson build systems default
> > >>>>> -		machine = 'corei7'
> > >>>>> +		cpu_instruction_set = 'corei7'
> > >>>>>    	elif host_machine.cpu_family().startswith('arm')
> > >>>>> -		machine = 'armv7-a'
> > >>>>> +		cpu_instruction_set = 'armv7-a'
> > >>>>>    	elif host_machine.cpu_family().startswith('aarch')
> > >>>>>    		# arm64 manages defaults in config/arm/meson.build
> > >>>>> -		machine = 'default'
> > >>>>> +		cpu_instruction_set = 'default'
> > >>>>>    	elif host_machine.cpu_family().startswith('ppc')
> > >>>>> -		machine = 'power8'
> > >>>>> +		cpu_instruction_set = 'power8'
> > >>>>>    	endif
> > >>>>>    endif
> > >>>
> > >>> This change forces the build on a P9 system to use the P8 instruction set.
> > >>> Prior to this change the "native" machine type was used which
> > >>> resulted in P9 instructions when built on a P9 system.  How do I
> > >>> force the build to use the
> > >>> power9 instruction set in this case?
> > >>>
> > >>> Dave
> > >>
> > >>  From looking at the patch, setting the "platform" to "native", or
> > >> the instruction_set to "native" should do this.
> > >> While I consider generic builds a good thing, I wonder if there is an
> > >> expectation that "native" is always the default build type for DPDK builds?
> > >>
> > >> /Bruce
> > >
> > > I left this patch alone so that people could chime in, but noone did, so let's try
> > to find some agreeable solution.
> > >
> > > My current thoughts are as such:
> > > The platform parameter specifies a set of DPDK options that will be used. This
> > is what arm uses for its builds, x86 and ppc don't use this.
> > > The cpu_instruction_set sets just one configuration among the "platform"
> > configuration set.
> > > We want the build to work on most machines of the machine architecture.
> > That implies platform=generic (as in use config options that will work on
> > everything of that architecture) and cpu_instruction_set=generic (as in use ISA
> > that will work on all cpus of the build machine architecture).
> > > Setting cpu_instruction_set=generic changes the build without cmdline options
> > for ppc. Thus, the expectation may be that cpu_instruction_set should be native
> > by default.
> > >
> > > For arm, cpu_instruction_set is ignored (and thus the value doen't matter),
> > since we can't use that without other config options (e.g. DPDK config for an
> > SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an invalid
> > cpu_instuction_set). That means the only relevant parameter for Arm is platform
> > and if we want to have a build usable on most machines of the build type, we
> > have to use platform=generic.
> > >
> > > For x86 and ppc, there's no difference between native and generic platform (as
> > it's a new argument, the purpose of which is to differentiate DPDK config across
> > platforms, which doesn't exist for x86 and ppc - DPDK config is the same (correct
> > me if I'm wrong)).
> > >
> > > So it basically boils down to what should be the default value of
> > cpu_instruction_set when platform=generic (for platform=native, it's obviously
> > native):
> > > 1. cpu_instruction_set=native, this would preserve the current behavior, but
> > we won't use the 'auto' default. I think we can fall back to this if we don't agree
> > on anything better.
> > > 2. cpu_instruction_set=auto, the same as cpu_instruction_set=generic,
> > > 3. cpu_instruction_set=generic, this changes behavior for ppc builds, but we
> > may be able to remedy this:
> > > Similarly to arm (arm is using platform for this, but the idea is the same), if
> > cpu_instruction_set is generic, we can do some discovery for pcc and set the ISA
> > accordingly (either power8 or power9). If I understand it correctly, power8 is a
> > different architecture from power9 (I could be wrong on this), so this is
> > desirable. There's some logic in config/ppc/meson.build, but it doesn't seem
> > sufficient as a discovery mechanism between power8/power9.
> > 
> > POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA v3.0), so
> > setting cpu_instruction_set to GENERIC is a reasonable option. POWER10 CPUs
> > (Power ISA v3.1) are around the corner so I want to make sure developers can
> > tune the application for the platform as easily as possible.  I'm fine with
> > supporting GENERIC, just need clear instructions on how to build for a particular
> > ISA.
> > 
> 
> That's good to hear. Setting cpu_instruction_set will set the ISA.
> 
> We'll need to document the behavior properly, but I'm not sure where - Bruce? Seems like meson_options.txt doesn't have enough room for that.
> 

Yes, agreed. I suggest putting in the option help text a link to the
documentation where we explain the options more fully.

/Bruce

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Tuesday, February 23, 2021 10:43 AM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: David Christensen <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> Subject: Re: [RFC PATCH v2] build: add platform meson option
> 
> On Tue, Feb 23, 2021 at 08:45:09AM +0000, Juraj Linkeš wrote:
> >
> >
> > > -----Original Message-----
> > > From: David Christensen <drc@linux.vnet.ibm.com>
> > > Sent: Monday, February 22, 2021 10:25 PM
> > > To: Juraj Linkeš <juraj.linkes@pantheon.tech>; Bruce Richardson
> > > <bruce.richardson@intel.com>
> > > Cc: thomas@monjalon.net; Honnappa.Nagarahalli@arm.com;
> dev@dpdk.org
> > > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > >
> > >
> > >
> > > On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> > > >
> > > >
> > > >> -----Original Message-----
> > > >> From: Bruce Richardson <bruce.richardson@intel.com>
> > > >> Sent: Wednesday, January 6, 2021 3:43 PM
> > > >> To: David Christensen <drc@linux.vnet.ibm.com>
> > > >> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>;
> > > >> thomas@monjalon.net; Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > > >> Subject: Re: [RFC PATCH v2] build: add platform meson option
> > > >>
> > > >> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > > >>>>> The current meson option 'machine' should only specify the
> > > >>>>> ISA, which is not sufficient for Arm, where setting ISA
> > > >>>>> implies other setting as
> > > >> well.
> > > >>>>> Add a new meson option, 'platform', which differentiates the
> > > >>>>> type of the build
> > > >>>>> (native/generic) and sets machine accordingly, unless the user
> > > >>>>> chooses to override it.
> > > >>>>> The 'machine' option also doesn't describe very well what it
> > > >>>>> sets, so introduce a new option 'cpu_instruction_set', but
> > > >>>>> keep 'machine' for backward compatibility.
> > > >>>>> These two new variables, taken together, achieve what 'machine'
> > > >>>>> was setting per architecture - setting the ISA in x86 build
> > > >>>>> and setting native/default 'build type' in aarch64 build - is
> > > >>>>> now properly being set for all architectures in a uniform manner.
> > > >>>>>
> > > >>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > >>>>> ---
> > > >>>>>    config/arm/meson.build        |  4 +--
> > > >>>>>    config/meson.build            | 47 +++++++++++++++++++++++++--------
> --
> > > >>>>>    devtools/test-meson-builds.sh |  9 ++++---
> > > >>>>>    meson_options.txt             |  8 ++++--
> > > >>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
> > > >>>>>
> > > >>>>> diff --git a/config/arm/meson.build b/config/arm/meson.build
> > > >>>>> index
> > > >>>>> 42b4e43c7..6b09a74a7 100644
> > > >>>>> --- a/config/arm/meson.build
> > > >>>>> +++ b/config/arm/meson.build
> > > >>>>> @@ -3,10 +3,10 @@
> > > >>>>>    # Copyright(c) 2017 Cavium, Inc
> > > >>>>>
> > > >>>>>    # for checking defines we need to use the correct compiler
> > > >>>>> flags -march_opt = '-
> > > >>>>> march=@0@'.format(machine)
> > > >>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > > >>>>>
> > > >>>>>    arm_force_native_march = false -arm_force_default_march =
> > > >>>>> (machine == 'default')
> > > >>>>> +arm_force_default_march = (platform == 'generic')
> > > >>>>>
> > > >>>>>    flags_common_default = [
> > > >>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
> > > >>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
> > > >>>>> b/config/meson.build index a3154e29c..647116513 100644
> > > >>>>> --- a/config/meson.build
> > > >>>>> +++ b/config/meson.build
> > > >>>>> @@ -63,42 +63,63 @@ if not is_windows
> > > >>>>>    			pmd_subdir_opt)
> > > >>>>>    endif
> > > >>>>>
> > > >>>>> -# set the machine type and cflags for it
> > > >>>>> +platform = get_option('platform')
> > > >>>>> +
> > > >>>>> +# set the cpu_instruction_set type and cflags for it
> > > >>>>>    if meson.is_cross_build()
> > > >>>>> -	machine = host_machine.cpu()
> > > >>>>> +	cpu_instruction_set = host_machine.cpu()
> > > >>>>>    else
> > > >>>>> -	machine = get_option('machine')
> > > >>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
> > > >>>>> +	if get_option('machine') != 'auto'
> > > >>>>> +		warning('The "machine" option is deprecated. ' +
> > > >>>>> +		        'Please use "cpu_instruction_set" instead.')
> > > >>>>> +		if cpu_instruction_set != 'auto'
> > > >>>>> +			error('Setting both "machine" and ' +
> > > >>>>> +			      '"cpu_instruction_set" is unsupported.')
> > > >>>>> +		endif
> > > >>>>> +		cpu_instruction_set = get_option('machine')
> > > >>>>> +	endif
> > > >>>>> +endif
> > > >>>>> +
> > > >>>>> +if platform == 'native'
> > > >>>>> +	if cpu_instruction_set == 'auto'
> > > >>>>> +		cpu_instruction_set = 'native'
> > > >>>>> +	endif
> > > >>>>> +elif platform == 'generic'
> > > >>>>> +	if cpu_instruction_set == 'auto'
> > > >>>>> +		cpu_instruction_set = 'default'
> > > >>>>> +	endif
> > > >>>>>    endif
> > > >>>>>
> > > >>>>> -# machine type 'default' is special, it defaults to the per
> > > >>>>> arch agreed common
> > > >>>>> +if cpu_instruction_set == 'default'
> > > >>>>> +# cpu_instruction_set type 'default' 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 == 'default'
> > > >>>>>    	if host_machine.cpu_family().startswith('x86')
> > > >>>>>    		# matches the old pre-meson build systems default
> > > >>>>> -		machine = 'corei7'
> > > >>>>> +		cpu_instruction_set = 'corei7'
> > > >>>>>    	elif host_machine.cpu_family().startswith('arm')
> > > >>>>> -		machine = 'armv7-a'
> > > >>>>> +		cpu_instruction_set = 'armv7-a'
> > > >>>>>    	elif host_machine.cpu_family().startswith('aarch')
> > > >>>>>    		# arm64 manages defaults in config/arm/meson.build
> > > >>>>> -		machine = 'default'
> > > >>>>> +		cpu_instruction_set = 'default'
> > > >>>>>    	elif host_machine.cpu_family().startswith('ppc')
> > > >>>>> -		machine = 'power8'
> > > >>>>> +		cpu_instruction_set = 'power8'
> > > >>>>>    	endif
> > > >>>>>    endif
> > > >>>
> > > >>> This change forces the build on a P9 system to use the P8 instruction set.
> > > >>> Prior to this change the "native" machine type was used which
> > > >>> resulted in P9 instructions when built on a P9 system.  How do I
> > > >>> force the build to use the
> > > >>> power9 instruction set in this case?
> > > >>>
> > > >>> Dave
> > > >>
> > > >>  From looking at the patch, setting the "platform" to "native",
> > > >> or the instruction_set to "native" should do this.
> > > >> While I consider generic builds a good thing, I wonder if there
> > > >> is an expectation that "native" is always the default build type for DPDK
> builds?
> > > >>
> > > >> /Bruce
> > > >
> > > > I left this patch alone so that people could chime in, but noone
> > > > did, so let's try
> > > to find some agreeable solution.
> > > >
> > > > My current thoughts are as such:
> > > > The platform parameter specifies a set of DPDK options that will
> > > > be used. This
> > > is what arm uses for its builds, x86 and ppc don't use this.
> > > > The cpu_instruction_set sets just one configuration among the "platform"
> > > configuration set.
> > > > We want the build to work on most machines of the machine architecture.
> > > That implies platform=generic (as in use config options that will
> > > work on everything of that architecture) and
> > > cpu_instruction_set=generic (as in use ISA that will work on all cpus of the
> build machine architecture).
> > > > Setting cpu_instruction_set=generic changes the build without
> > > > cmdline options
> > > for ppc. Thus, the expectation may be that cpu_instruction_set
> > > should be native by default.
> > > >
> > > > For arm, cpu_instruction_set is ignored (and thus the value doen't
> > > > matter),
> > > since we can't use that without other config options (e.g. DPDK
> > > config for an SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an
> > > invalid cpu_instuction_set). That means the only relevant parameter
> > > for Arm is platform and if we want to have a build usable on most
> > > machines of the build type, we have to use platform=generic.
> > > >
> > > > For x86 and ppc, there's no difference between native and generic
> > > > platform (as
> > > it's a new argument, the purpose of which is to differentiate DPDK
> > > config across platforms, which doesn't exist for x86 and ppc - DPDK
> > > config is the same (correct me if I'm wrong)).
> > > >
> > > > So it basically boils down to what should be the default value of
> > > cpu_instruction_set when platform=generic (for platform=native, it's
> > > obviously
> > > native):
> > > > 1. cpu_instruction_set=native, this would preserve the current
> > > > behavior, but
> > > we won't use the 'auto' default. I think we can fall back to this if
> > > we don't agree on anything better.
> > > > 2. cpu_instruction_set=auto, the same as
> > > > cpu_instruction_set=generic, 3. cpu_instruction_set=generic, this
> > > > changes behavior for ppc builds, but we
> > > may be able to remedy this:
> > > > Similarly to arm (arm is using platform for this, but the idea is
> > > > the same), if
> > > cpu_instruction_set is generic, we can do some discovery for pcc and
> > > set the ISA accordingly (either power8 or power9). If I understand
> > > it correctly, power8 is a different architecture from power9 (I
> > > could be wrong on this), so this is desirable. There's some logic in
> > > config/ppc/meson.build, but it doesn't seem sufficient as a discovery
> mechanism between power8/power9.
> > >
> > > POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA v3.0),
> > > so setting cpu_instruction_set to GENERIC is a reasonable option.
> > > POWER10 CPUs (Power ISA v3.1) are around the corner so I want to
> > > make sure developers can tune the application for the platform as
> > > easily as possible.  I'm fine with supporting GENERIC, just need
> > > clear instructions on how to build for a particular ISA.
> > >
> >
> > That's good to hear. Setting cpu_instruction_set will set the ISA.
> >
> > We'll need to document the behavior properly, but I'm not sure where - Bruce?
> Seems like meson_options.txt doesn't have enough room for that.
> >
> 
> Yes, agreed. I suggest putting in the option help text a link to the documentation
> where we explain the options more fully.
> 
> /Bruce

You mentioned in the kni cross compile patch that we should do a separate patch where we explain the option in docs and I believe this would go into that patch. Before we do that, let's figure out the best description without the link. I currently have:
option('cpu_instruction_set', type: 'string', value: 'auto',
	description: 'Set the target machine ISA (instruction set architecture). Will be set according to the platform option by default.')
option('platform', type: 'string', value: 'generic',
	description: 'Platform to build, either "native" or "generic".')

What do you think? Should we expand the platform description a bit?

On Thu, Feb 25, 2021 at 12:51:57PM +0000, Juraj Linkeš wrote:
> 
> 
> > -----Original Message-----
> > From: Bruce Richardson <bruce.richardson@intel.com>
> > Sent: Tuesday, February 23, 2021 10:43 AM
> > To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > Cc: David Christensen <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> > Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > 
> > On Tue, Feb 23, 2021 at 08:45:09AM +0000, Juraj Linkeš wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: David Christensen <drc@linux.vnet.ibm.com>
> > > > Sent: Monday, February 22, 2021 10:25 PM
> > > > To: Juraj Linkeš <juraj.linkes@pantheon.tech>; Bruce Richardson
> > > > <bruce.richardson@intel.com>
> > > > Cc: thomas@monjalon.net; Honnappa.Nagarahalli@arm.com;
> > dev@dpdk.org
> > > > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > > >
> > > >
> > > >
> > > > On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> > > > >
> > > > >
> > > > >> -----Original Message-----
> > > > >> From: Bruce Richardson <bruce.richardson@intel.com>
> > > > >> Sent: Wednesday, January 6, 2021 3:43 PM
> > > > >> To: David Christensen <drc@linux.vnet.ibm.com>
> > > > >> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>;
> > > > >> thomas@monjalon.net; Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > > > >> Subject: Re: [RFC PATCH v2] build: add platform meson option
> > > > >>
> > > > >> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > > > >>>>> The current meson option 'machine' should only specify the
> > > > >>>>> ISA, which is not sufficient for Arm, where setting ISA
> > > > >>>>> implies other setting as
> > > > >> well.
> > > > >>>>> Add a new meson option, 'platform', which differentiates the
> > > > >>>>> type of the build
> > > > >>>>> (native/generic) and sets machine accordingly, unless the user
> > > > >>>>> chooses to override it.
> > > > >>>>> The 'machine' option also doesn't describe very well what it
> > > > >>>>> sets, so introduce a new option 'cpu_instruction_set', but
> > > > >>>>> keep 'machine' for backward compatibility.
> > > > >>>>> These two new variables, taken together, achieve what 'machine'
> > > > >>>>> was setting per architecture - setting the ISA in x86 build
> > > > >>>>> and setting native/default 'build type' in aarch64 build - is
> > > > >>>>> now properly being set for all architectures in a uniform manner.
> > > > >>>>>
> > > > >>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > > >>>>> ---
> > > > >>>>>    config/arm/meson.build        |  4 +--
> > > > >>>>>    config/meson.build            | 47 +++++++++++++++++++++++++--------
> > --
> > > > >>>>>    devtools/test-meson-builds.sh |  9 ++++---
> > > > >>>>>    meson_options.txt             |  8 ++++--
> > > > >>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
> > > > >>>>>
> > > > >>>>> diff --git a/config/arm/meson.build b/config/arm/meson.build
> > > > >>>>> index
> > > > >>>>> 42b4e43c7..6b09a74a7 100644
> > > > >>>>> --- a/config/arm/meson.build
> > > > >>>>> +++ b/config/arm/meson.build
> > > > >>>>> @@ -3,10 +3,10 @@
> > > > >>>>>    # Copyright(c) 2017 Cavium, Inc
> > > > >>>>>
> > > > >>>>>    # for checking defines we need to use the correct compiler
> > > > >>>>> flags -march_opt = '-
> > > > >>>>> march=@0@'.format(machine)
> > > > >>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > > > >>>>>
> > > > >>>>>    arm_force_native_march = false -arm_force_default_march =
> > > > >>>>> (machine == 'default')
> > > > >>>>> +arm_force_default_march = (platform == 'generic')
> > > > >>>>>
> > > > >>>>>    flags_common_default = [
> > > > >>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
> > > > >>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
> > > > >>>>> b/config/meson.build index a3154e29c..647116513 100644
> > > > >>>>> --- a/config/meson.build
> > > > >>>>> +++ b/config/meson.build
> > > > >>>>> @@ -63,42 +63,63 @@ if not is_windows
> > > > >>>>>    			pmd_subdir_opt)
> > > > >>>>>    endif
> > > > >>>>>
> > > > >>>>> -# set the machine type and cflags for it
> > > > >>>>> +platform = get_option('platform')
> > > > >>>>> +
> > > > >>>>> +# set the cpu_instruction_set type and cflags for it
> > > > >>>>>    if meson.is_cross_build()
> > > > >>>>> -	machine = host_machine.cpu()
> > > > >>>>> +	cpu_instruction_set = host_machine.cpu()
> > > > >>>>>    else
> > > > >>>>> -	machine = get_option('machine')
> > > > >>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
> > > > >>>>> +	if get_option('machine') != 'auto'
> > > > >>>>> +		warning('The "machine" option is deprecated. ' +
> > > > >>>>> +		        'Please use "cpu_instruction_set" instead.')
> > > > >>>>> +		if cpu_instruction_set != 'auto'
> > > > >>>>> +			error('Setting both "machine" and ' +
> > > > >>>>> +			      '"cpu_instruction_set" is unsupported.')
> > > > >>>>> +		endif
> > > > >>>>> +		cpu_instruction_set = get_option('machine')
> > > > >>>>> +	endif
> > > > >>>>> +endif
> > > > >>>>> +
> > > > >>>>> +if platform == 'native'
> > > > >>>>> +	if cpu_instruction_set == 'auto'
> > > > >>>>> +		cpu_instruction_set = 'native'
> > > > >>>>> +	endif
> > > > >>>>> +elif platform == 'generic'
> > > > >>>>> +	if cpu_instruction_set == 'auto'
> > > > >>>>> +		cpu_instruction_set = 'default'
> > > > >>>>> +	endif
> > > > >>>>>    endif
> > > > >>>>>
> > > > >>>>> -# machine type 'default' is special, it defaults to the per
> > > > >>>>> arch agreed common
> > > > >>>>> +if cpu_instruction_set == 'default'
> > > > >>>>> +# cpu_instruction_set type 'default' 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 == 'default'
> > > > >>>>>    	if host_machine.cpu_family().startswith('x86')
> > > > >>>>>    		# matches the old pre-meson build systems default
> > > > >>>>> -		machine = 'corei7'
> > > > >>>>> +		cpu_instruction_set = 'corei7'
> > > > >>>>>    	elif host_machine.cpu_family().startswith('arm')
> > > > >>>>> -		machine = 'armv7-a'
> > > > >>>>> +		cpu_instruction_set = 'armv7-a'
> > > > >>>>>    	elif host_machine.cpu_family().startswith('aarch')
> > > > >>>>>    		# arm64 manages defaults in config/arm/meson.build
> > > > >>>>> -		machine = 'default'
> > > > >>>>> +		cpu_instruction_set = 'default'
> > > > >>>>>    	elif host_machine.cpu_family().startswith('ppc')
> > > > >>>>> -		machine = 'power8'
> > > > >>>>> +		cpu_instruction_set = 'power8'
> > > > >>>>>    	endif
> > > > >>>>>    endif
> > > > >>>
> > > > >>> This change forces the build on a P9 system to use the P8 instruction set.
> > > > >>> Prior to this change the "native" machine type was used which
> > > > >>> resulted in P9 instructions when built on a P9 system.  How do I
> > > > >>> force the build to use the
> > > > >>> power9 instruction set in this case?
> > > > >>>
> > > > >>> Dave
> > > > >>
> > > > >>  From looking at the patch, setting the "platform" to "native",
> > > > >> or the instruction_set to "native" should do this.
> > > > >> While I consider generic builds a good thing, I wonder if there
> > > > >> is an expectation that "native" is always the default build type for DPDK
> > builds?
> > > > >>
> > > > >> /Bruce
> > > > >
> > > > > I left this patch alone so that people could chime in, but noone
> > > > > did, so let's try
> > > > to find some agreeable solution.
> > > > >
> > > > > My current thoughts are as such:
> > > > > The platform parameter specifies a set of DPDK options that will
> > > > > be used. This
> > > > is what arm uses for its builds, x86 and ppc don't use this.
> > > > > The cpu_instruction_set sets just one configuration among the "platform"
> > > > configuration set.
> > > > > We want the build to work on most machines of the machine architecture.
> > > > That implies platform=generic (as in use config options that will
> > > > work on everything of that architecture) and
> > > > cpu_instruction_set=generic (as in use ISA that will work on all cpus of the
> > build machine architecture).
> > > > > Setting cpu_instruction_set=generic changes the build without
> > > > > cmdline options
> > > > for ppc. Thus, the expectation may be that cpu_instruction_set
> > > > should be native by default.
> > > > >
> > > > > For arm, cpu_instruction_set is ignored (and thus the value doen't
> > > > > matter),
> > > > since we can't use that without other config options (e.g. DPDK
> > > > config for an SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an
> > > > invalid cpu_instuction_set). That means the only relevant parameter
> > > > for Arm is platform and if we want to have a build usable on most
> > > > machines of the build type, we have to use platform=generic.
> > > > >
> > > > > For x86 and ppc, there's no difference between native and generic
> > > > > platform (as
> > > > it's a new argument, the purpose of which is to differentiate DPDK
> > > > config across platforms, which doesn't exist for x86 and ppc - DPDK
> > > > config is the same (correct me if I'm wrong)).
> > > > >
> > > > > So it basically boils down to what should be the default value of
> > > > cpu_instruction_set when platform=generic (for platform=native, it's
> > > > obviously
> > > > native):
> > > > > 1. cpu_instruction_set=native, this would preserve the current
> > > > > behavior, but
> > > > we won't use the 'auto' default. I think we can fall back to this if
> > > > we don't agree on anything better.
> > > > > 2. cpu_instruction_set=auto, the same as
> > > > > cpu_instruction_set=generic, 3. cpu_instruction_set=generic, this
> > > > > changes behavior for ppc builds, but we
> > > > may be able to remedy this:
> > > > > Similarly to arm (arm is using platform for this, but the idea is
> > > > > the same), if
> > > > cpu_instruction_set is generic, we can do some discovery for pcc and
> > > > set the ISA accordingly (either power8 or power9). If I understand
> > > > it correctly, power8 is a different architecture from power9 (I
> > > > could be wrong on this), so this is desirable. There's some logic in
> > > > config/ppc/meson.build, but it doesn't seem sufficient as a discovery
> > mechanism between power8/power9.
> > > >
> > > > POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA v3.0),
> > > > so setting cpu_instruction_set to GENERIC is a reasonable option.
> > > > POWER10 CPUs (Power ISA v3.1) are around the corner so I want to
> > > > make sure developers can tune the application for the platform as
> > > > easily as possible.  I'm fine with supporting GENERIC, just need
> > > > clear instructions on how to build for a particular ISA.
> > > >
> > >
> > > That's good to hear. Setting cpu_instruction_set will set the ISA.
> > >
> > > We'll need to document the behavior properly, but I'm not sure where - Bruce?
> > Seems like meson_options.txt doesn't have enough room for that.
> > >
> > 
> > Yes, agreed. I suggest putting in the option help text a link to the documentation
> > where we explain the options more fully.
> > 
> > /Bruce
> 
> You mentioned in the kni cross compile patch that we should do a separate patch where we explain the option in docs and I believe this would go into that patch. Before we do that, let's figure out the best description without the link. I currently have:
> option('cpu_instruction_set', type: 'string', value: 'auto',
> 	description: 'Set the target machine ISA (instruction set architecture). Will be set according to the platform option by default.')
> option('platform', type: 'string', value: 'generic',
> 	description: 'Platform to build, either "native" or "generic".')
> 
> What do you think? Should we expand the platform description a bit?

Are there not more platform options than just those two?

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Thursday, February 25, 2021 1:54 PM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: David Christensen <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> Subject: Re: [RFC PATCH v2] build: add platform meson option
> 
> On Thu, Feb 25, 2021 at 12:51:57PM +0000, Juraj Linkeš wrote:
> >
> >
> > > -----Original Message-----
> > > From: Bruce Richardson <bruce.richardson@intel.com>
> > > Sent: Tuesday, February 23, 2021 10:43 AM
> > > To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > Cc: David Christensen <drc@linux.vnet.ibm.com>; thomas@monjalon.net;
> > > Honnappa.Nagarahalli@arm.com; dev@dpdk.org
> > > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > >
> > > On Tue, Feb 23, 2021 at 08:45:09AM +0000, Juraj Linkeš wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: David Christensen <drc@linux.vnet.ibm.com>
> > > > > Sent: Monday, February 22, 2021 10:25 PM
> > > > > To: Juraj Linkeš <juraj.linkes@pantheon.tech>; Bruce Richardson
> > > > > <bruce.richardson@intel.com>
> > > > > Cc: thomas@monjalon.net; Honnappa.Nagarahalli@arm.com;
> > > dev@dpdk.org
> > > > > Subject: Re: [RFC PATCH v2] build: add platform meson option
> > > > >
> > > > >
> > > > >
> > > > > On 2/19/21 1:11 AM, Juraj Linkeš wrote:
> > > > > >
> > > > > >
> > > > > >> -----Original Message-----
> > > > > >> From: Bruce Richardson <bruce.richardson@intel.com>
> > > > > >> Sent: Wednesday, January 6, 2021 3:43 PM
> > > > > >> To: David Christensen <drc@linux.vnet.ibm.com>
> > > > > >> Cc: Juraj Linkeš <juraj.linkes@pantheon.tech>;
> > > > > >> thomas@monjalon.net; Honnappa.Nagarahalli@arm.com;
> > > > > >> dev@dpdk.org
> > > > > >> Subject: Re: [RFC PATCH v2] build: add platform meson option
> > > > > >>
> > > > > >> On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:
> > > > > >>>>> The current meson option 'machine' should only specify the
> > > > > >>>>> ISA, which is not sufficient for Arm, where setting ISA
> > > > > >>>>> implies other setting as
> > > > > >> well.
> > > > > >>>>> Add a new meson option, 'platform', which differentiates
> > > > > >>>>> the type of the build
> > > > > >>>>> (native/generic) and sets machine accordingly, unless the
> > > > > >>>>> user chooses to override it.
> > > > > >>>>> The 'machine' option also doesn't describe very well what
> > > > > >>>>> it sets, so introduce a new option 'cpu_instruction_set',
> > > > > >>>>> but keep 'machine' for backward compatibility.
> > > > > >>>>> These two new variables, taken together, achieve what 'machine'
> > > > > >>>>> was setting per architecture - setting the ISA in x86
> > > > > >>>>> build and setting native/default 'build type' in aarch64
> > > > > >>>>> build - is now properly being set for all architectures in a uniform
> manner.
> > > > > >>>>>
> > > > > >>>>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > > > > >>>>> ---
> > > > > >>>>>    config/arm/meson.build        |  4 +--
> > > > > >>>>>    config/meson.build            | 47 +++++++++++++++++++++++++----
> ----
> > > --
> > > > > >>>>>    devtools/test-meson-builds.sh |  9 ++++---
> > > > > >>>>>    meson_options.txt             |  8 ++++--
> > > > > >>>>>    4 files changed, 47 insertions(+), 21 deletions(-)
> > > > > >>>>>
> > > > > >>>>> diff --git a/config/arm/meson.build
> > > > > >>>>> b/config/arm/meson.build index
> > > > > >>>>> 42b4e43c7..6b09a74a7 100644
> > > > > >>>>> --- a/config/arm/meson.build
> > > > > >>>>> +++ b/config/arm/meson.build
> > > > > >>>>> @@ -3,10 +3,10 @@
> > > > > >>>>>    # Copyright(c) 2017 Cavium, Inc
> > > > > >>>>>
> > > > > >>>>>    # for checking defines we need to use the correct
> > > > > >>>>> compiler flags -march_opt = '-
> > > > > >>>>> march=@0@'.format(machine)
> > > > > >>>>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
> > > > > >>>>>
> > > > > >>>>>    arm_force_native_march = false -arm_force_default_march
> > > > > >>>>> = (machine == 'default')
> > > > > >>>>> +arm_force_default_march = (platform == 'generic')
> > > > > >>>>>
> > > > > >>>>>    flags_common_default = [
> > > > > >>>>>    	# Accelarate rte_memcpy. Be sure to run unit test
> > > > > >>>>> (memcpy_perf_autotest) diff --git a/config/meson.build
> > > > > >>>>> b/config/meson.build index a3154e29c..647116513 100644
> > > > > >>>>> --- a/config/meson.build
> > > > > >>>>> +++ b/config/meson.build
> > > > > >>>>> @@ -63,42 +63,63 @@ if not is_windows
> > > > > >>>>>    			pmd_subdir_opt)
> > > > > >>>>>    endif
> > > > > >>>>>
> > > > > >>>>> -# set the machine type and cflags for it
> > > > > >>>>> +platform = get_option('platform')
> > > > > >>>>> +
> > > > > >>>>> +# set the cpu_instruction_set type and cflags for it
> > > > > >>>>>    if meson.is_cross_build()
> > > > > >>>>> -	machine = host_machine.cpu()
> > > > > >>>>> +	cpu_instruction_set = host_machine.cpu()
> > > > > >>>>>    else
> > > > > >>>>> -	machine = get_option('machine')
> > > > > >>>>> +	cpu_instruction_set = get_option('cpu_instruction_set')
> > > > > >>>>> +	if get_option('machine') != 'auto'
> > > > > >>>>> +		warning('The "machine" option is deprecated. ' +
> > > > > >>>>> +		        'Please use "cpu_instruction_set" instead.')
> > > > > >>>>> +		if cpu_instruction_set != 'auto'
> > > > > >>>>> +			error('Setting both "machine" and ' +
> > > > > >>>>> +			      '"cpu_instruction_set" is unsupported.')
> > > > > >>>>> +		endif
> > > > > >>>>> +		cpu_instruction_set = get_option('machine')
> > > > > >>>>> +	endif
> > > > > >>>>> +endif
> > > > > >>>>> +
> > > > > >>>>> +if platform == 'native'
> > > > > >>>>> +	if cpu_instruction_set == 'auto'
> > > > > >>>>> +		cpu_instruction_set = 'native'
> > > > > >>>>> +	endif
> > > > > >>>>> +elif platform == 'generic'
> > > > > >>>>> +	if cpu_instruction_set == 'auto'
> > > > > >>>>> +		cpu_instruction_set = 'default'
> > > > > >>>>> +	endif
> > > > > >>>>>    endif
> > > > > >>>>>
> > > > > >>>>> -# machine type 'default' is special, it defaults to the
> > > > > >>>>> per arch agreed common
> > > > > >>>>> +if cpu_instruction_set == 'default'
> > > > > >>>>> +# cpu_instruction_set type 'default' 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 == 'default'
> > > > > >>>>>    	if host_machine.cpu_family().startswith('x86')
> > > > > >>>>>    		# matches the old pre-meson build systems default
> > > > > >>>>> -		machine = 'corei7'
> > > > > >>>>> +		cpu_instruction_set = 'corei7'
> > > > > >>>>>    	elif host_machine.cpu_family().startswith('arm')
> > > > > >>>>> -		machine = 'armv7-a'
> > > > > >>>>> +		cpu_instruction_set = 'armv7-a'
> > > > > >>>>>    	elif host_machine.cpu_family().startswith('aarch')
> > > > > >>>>>    		# arm64 manages defaults in config/arm/meson.build
> > > > > >>>>> -		machine = 'default'
> > > > > >>>>> +		cpu_instruction_set = 'default'
> > > > > >>>>>    	elif host_machine.cpu_family().startswith('ppc')
> > > > > >>>>> -		machine = 'power8'
> > > > > >>>>> +		cpu_instruction_set = 'power8'
> > > > > >>>>>    	endif
> > > > > >>>>>    endif
> > > > > >>>
> > > > > >>> This change forces the build on a P9 system to use the P8 instruction
> set.
> > > > > >>> Prior to this change the "native" machine type was used
> > > > > >>> which resulted in P9 instructions when built on a P9 system.
> > > > > >>> How do I force the build to use the
> > > > > >>> power9 instruction set in this case?
> > > > > >>>
> > > > > >>> Dave
> > > > > >>
> > > > > >>  From looking at the patch, setting the "platform" to
> > > > > >> "native", or the instruction_set to "native" should do this.
> > > > > >> While I consider generic builds a good thing, I wonder if
> > > > > >> there is an expectation that "native" is always the default
> > > > > >> build type for DPDK
> > > builds?
> > > > > >>
> > > > > >> /Bruce
> > > > > >
> > > > > > I left this patch alone so that people could chime in, but
> > > > > > noone did, so let's try
> > > > > to find some agreeable solution.
> > > > > >
> > > > > > My current thoughts are as such:
> > > > > > The platform parameter specifies a set of DPDK options that
> > > > > > will be used. This
> > > > > is what arm uses for its builds, x86 and ppc don't use this.
> > > > > > The cpu_instruction_set sets just one configuration among the
> "platform"
> > > > > configuration set.
> > > > > > We want the build to work on most machines of the machine
> architecture.
> > > > > That implies platform=generic (as in use config options that
> > > > > will work on everything of that architecture) and
> > > > > cpu_instruction_set=generic (as in use ISA that will work on all
> > > > > cpus of the
> > > build machine architecture).
> > > > > > Setting cpu_instruction_set=generic changes the build without
> > > > > > cmdline options
> > > > > for ppc. Thus, the expectation may be that cpu_instruction_set
> > > > > should be native by default.
> > > > > >
> > > > > > For arm, cpu_instruction_set is ignored (and thus the value
> > > > > > doen't matter),
> > > > > since we can't use that without other config options (e.g. DPDK
> > > > > config for an SoC (such as RTE_ARM_FEATURE_ATOMICS) used with an
> > > > > invalid cpu_instuction_set). That means the only relevant
> > > > > parameter for Arm is platform and if we want to have a build
> > > > > usable on most machines of the build type, we have to use
> platform=generic.
> > > > > >
> > > > > > For x86 and ppc, there's no difference between native and
> > > > > > generic platform (as
> > > > > it's a new argument, the purpose of which is to differentiate
> > > > > DPDK config across platforms, which doesn't exist for x86 and
> > > > > ppc - DPDK config is the same (correct me if I'm wrong)).
> > > > > >
> > > > > > So it basically boils down to what should be the default value
> > > > > > of
> > > > > cpu_instruction_set when platform=generic (for platform=native,
> > > > > it's obviously
> > > > > native):
> > > > > > 1. cpu_instruction_set=native, this would preserve the current
> > > > > > behavior, but
> > > > > we won't use the 'auto' default. I think we can fall back to
> > > > > this if we don't agree on anything better.
> > > > > > 2. cpu_instruction_set=auto, the same as
> > > > > > cpu_instruction_set=generic, 3. cpu_instruction_set=generic,
> > > > > > this changes behavior for ppc builds, but we
> > > > > may be able to remedy this:
> > > > > > Similarly to arm (arm is using platform for this, but the idea
> > > > > > is the same), if
> > > > > cpu_instruction_set is generic, we can do some discovery for pcc
> > > > > and set the ISA accordingly (either power8 or power9). If I
> > > > > understand it correctly, power8 is a different architecture from
> > > > > power9 (I could be wrong on this), so this is desirable. There's
> > > > > some logic in config/ppc/meson.build, but it doesn't seem
> > > > > sufficient as a discovery
> > > mechanism between power8/power9.
> > > > >
> > > > > POWER8 code (Power ISA v2.07) runs on POWER9 CPUs (Power ISA
> > > > > v3.0), so setting cpu_instruction_set to GENERIC is a reasonable option.
> > > > > POWER10 CPUs (Power ISA v3.1) are around the corner so I want to
> > > > > make sure developers can tune the application for the platform
> > > > > as easily as possible.  I'm fine with supporting GENERIC, just
> > > > > need clear instructions on how to build for a particular ISA.
> > > > >
> > > >
> > > > That's good to hear. Setting cpu_instruction_set will set the ISA.
> > > >
> > > > We'll need to document the behavior properly, but I'm not sure where -
> Bruce?
> > > Seems like meson_options.txt doesn't have enough room for that.
> > > >
> > >
> > > Yes, agreed. I suggest putting in the option help text a link to the
> > > documentation where we explain the options more fully.
> > >
> > > /Bruce
> >
> > You mentioned in the kni cross compile patch that we should do a separate
> patch where we explain the option in docs and I believe this would go into that
> patch. Before we do that, let's figure out the best description without the link. I
> currently have:
> > option('cpu_instruction_set', type: 'string', value: 'auto',
> > 	description: 'Set the target machine ISA (instruction set
> > architecture). Will be set according to the platform option by default.')
> option('platform', type: 'string', value: 'generic',
> > 	description: 'Platform to build, either "native" or "generic".')
> >
> > What do you think? Should we expand the platform description a bit?
> 
> Are there not more platform options than just those two?

We're adding more in http://patches.dpdk.org/project/dpdk/patch/1612361037-12746-3-git-send-email-juraj.linkes@pantheon.tech/. I don't think there are more than two without that.