<snip>
> Subject: Re: [dpdk-dev] [PATCH v5 2/4] build: add arm32 meson build flags
>
> On Mon, Jul 6, 2020 at 1:59 PM Juraj Linkeš <juraj.lin...@pantheon.tech>
> wrote:
> >
> > Base the flags on config/defconfig_arm-armv7a-linuxapp-gcc.
> > Omit driver flags which can be built on arm32.
> >
> > Signed-off-by: Juraj Linkeš <juraj.lin...@pantheon.tech>
>
> Hi Juraj,
>
> Not strictly specific to this patch. Just to understand, How armv7 support has
> been used?
I do not know how armv7 support is being used. I have not heard of anything so
far.
In this patch arm32 is actually referring to aarch32.
> - Is it for Running arm32 program on arm64 machines?
I am not sure if anyone would run armv7 binaries on arm64 machines. I would
think they will at least go through a re-compilation (to aarch32) and test
phase.
> - Is it for Native DPDK support from arm32. If so, What kind of PMD supports
> native arm32 DPDK?
Yes, this is for DPDK on aarch32 support. We do not have any plans to enable
any PMD for aarch32. The current goal is to make sure that the code compiles
for aarch32. Internally, we have validated few test cases for the libraries.
>
> Or some other use case?
>
> I would like to understand the arm32 use case, so we can review it at that
> angle.
I believe armv7a compilation is not supported in meson. Do you have any
thoughts? Do you plan to maintain the support for armv7a?
>
> > ---
> > config/arm/meson.build | 135
> > ++++++++++++++++++++++-------------------
> > 1 file changed, 74 insertions(+), 61 deletions(-)
> >
> > diff --git a/config/arm/meson.build b/config/arm/meson.build index
> > 8728051d5..b02fc95d9 100644
> > --- a/config/arm/meson.build
> > +++ b/config/arm/meson.build
> > @@ -34,6 +34,11 @@ flags_generic = [
> > ['RTE_MAX_LCORE', 256],
> > ['RTE_USE_C11_MEM_MODEL', true],
> > ['RTE_CACHE_LINE_SIZE', 128]]
> > +flags_generic_arm32 = [
> > + ['RTE_MACHINE', '"armv7a"'],
> > + ['RTE_MAX_LCORE', 128],
> > + ['RTE_USE_C11_MEM_MODEL', false],
> > + ['RTE_CACHE_LINE_SIZE', 64]]
> > flags_arm = [
> > ['RTE_MACHINE', '"armv8a"'],
> > ['RTE_MAX_LCORE', 16],
> > @@ -63,6 +68,10 @@ flags_armada = [
> > ['RTE_MAX_LCORE', 16]]
> >
> > flags_default_extra = []
> > +flags_default_arm32_extra = [
> > + ['RTE_ARCH_ARM_NEON_MEMCPY', false],
> > + ['RTE_ARCH_STRICT_ALIGN', true],
> > + ['RTE_EAL_NUMA_AWARE_HUGEPAGES', false]]
> > flags_n1sdp_extra = [
> > ['RTE_MACHINE', '"n1sdp"'],
> > ['RTE_MAX_NUMA_NODES', 1],
> > @@ -99,6 +108,9 @@ machine_args_generic = [
> > ['0xd0b', ['-mcpu=cortex-a76']],
> > ['0xd0c', ['-march=armv8.2-a+crc+crypto',
> > '-mcpu=neoverse-n1'], flags_n1sdp_extra]]
> >
> > +machine_args_generic_arm32 = [
> > + ['default_arm32', ['-march=armv7-a', '-mtune=cortex-a9',
> > +'-mfpu=neon'], flags_default_arm32_extra]]
> > +
> > machine_args_cavium = [
> > ['default', ['-march=armv8-a+crc+crypto','-mcpu=thunderx']],
> > ['native', ['-march=native']], @@ -114,6 +126,7 @@
> > machine_args_emag = [
> >
> > ## Arm implementer ID (ARM DDI 0487C.a, Section G7.2.106, Page
> > G7-5321) impl_generic = ['Generic armv8', flags_generic,
> > machine_args_generic]
> > +impl_generic_arm32 = ['Generic armv7', flags_generic_arm32,
> > +machine_args_generic_arm32]
> > impl_0x41 = ['Arm', flags_arm, machine_args_generic]
> > impl_0x42 = ['Broadcom', flags_generic, machine_args_generic]
> > impl_0x43 = ['Cavium', flags_cavium, machine_args_cavium] @@ -136,74
> > +149,74 @@ if not dpdk_conf.get('RTE_ARCH_64')
> > dpdk_conf.set('RTE_ARCH_ARMv7', 1)
> > # the minimum architecture supported, armv7-a, needs the following,
> > # mk/machine/armv7a/rte.vars.mk sets it too
> > - machine_args += '-mfpu=neon'
> > else
> > dpdk_conf.set('RTE_CACHE_LINE_SIZE', 128)
> > dpdk_conf.set('RTE_ARCH_ARM64', 1)
> > +endif
> >
> > - machine = []
> > - cmd_generic = ['generic', '', '', 'default', '']
> > - cmd_output = cmd_generic # Set generic by default
> > - machine_args = [] # Clear previous machine args
> > - if arm_force_default_march and not meson.is_cross_build()
> > +machine = []
> > +machine_args = [] # Clear previous machine args cmd_generic =
> > +['generic', '', '', 'default', ''] cmd_output = cmd_generic # Set
> > +generic by default if arm_force_default_march and not
> > +meson.is_cross_build()
> > + machine = impl_generic
> > + impl_pn = 'default'
> > +elif not meson.is_cross_build()
> > + # The script returns ['Implementer', 'Variant', 'Architecture',
> > + # 'Primary Part number', 'Revision']
> > + detect_vendor = find_program(join_paths(
> > + meson.current_source_dir(), 'armv8_machine.py'))
> > + cmd = run_command(detect_vendor.path())
> > + if cmd.returncode() == 0
> > + cmd_output = cmd.stdout().to_lower().strip().split(' ')
> > + endif
> > + # Set to generic if variable is not found
> > + machine = get_variable('impl_' + cmd_output[0], ['generic'])
> > + if machine[0] == 'generic'
> > machine = impl_generic
> > - impl_pn = 'default'
> > - elif not meson.is_cross_build()
> > - # The script returns ['Implementer', 'Variant',
> > 'Architecture',
> > - # 'Primary Part number', 'Revision']
> > - detect_vendor = find_program(join_paths(
> > - meson.current_source_dir(),
> > 'armv8_machine.py'))
> > - cmd = run_command(detect_vendor.path())
> > - if cmd.returncode() == 0
> > - cmd_output =
> > cmd.stdout().to_lower().strip().split(' ')
> > - endif
> > - # Set to generic if variable is not found
> > - machine = get_variable('impl_' + cmd_output[0], ['generic'])
> > - if machine[0] == 'generic'
> > - machine = impl_generic
> > - cmd_output = cmd_generic
> > - endif
> > - impl_pn = cmd_output[3]
> > - if arm_force_native_march == true
> > - impl_pn = 'native'
> > - endif
> > - else
> > - impl_id = meson.get_cross_property('implementor_id',
> > 'generic')
> > - impl_pn = meson.get_cross_property('implementor_pn',
> > 'default')
> > - machine = get_variable('impl_' + impl_id)
> > + cmd_output = cmd_generic
> > endif
> > -
> > - # Apply Common Defaults. These settings may be overwritten by
> machine
> > - # settings later.
> > - foreach flag: flags_common_default
> > - if flag.length() > 0
> > - dpdk_conf.set(flag[0], flag[1])
> > - endif
> > - endforeach
> > -
> > - message('Implementer : ' + machine[0])
> > - foreach flag: machine[1]
> > - if flag.length() > 0
> > - dpdk_conf.set(flag[0], flag[1])
> > - endif
> > - endforeach
> > -
> > - foreach marg: machine[2]
> > - if marg[0] == impl_pn
> > - foreach flag: marg[1]
> > - if cc.has_argument(flag)
> > - machine_args += flag
> > - endif
> > - endforeach
> > - # Apply any extra machine specific flags.
> > - foreach flag: marg.get(2, flags_default_extra)
> > - if flag.length() > 0
> > - dpdk_conf.set(flag[0], flag[1])
> > - endif
> > - endforeach
> > - endif
> > - endforeach
> > + impl_pn = cmd_output[3]
> > + if arm_force_native_march == true
> > + impl_pn = 'native'
> > + endif
> > +else
> > + impl_id = meson.get_cross_property('implementor_id', 'generic')
> > + impl_pn = meson.get_cross_property('implementor_pn', 'default')
> > + machine = get_variable('impl_' + impl_id)
> > endif
> > +
> > +# Apply Common Defaults. These settings may be overwritten by machine
> > +# settings later.
> > +foreach flag: flags_common_default
> > + if flag.length() > 0
> > + dpdk_conf.set(flag[0], flag[1])
> > + endif
> > +endforeach
> > +
> > +message('Implementer : ' + machine[0]) foreach flag: machine[1]
> > + if flag.length() > 0
> > + dpdk_conf.set(flag[0], flag[1])
> > + endif
> > +endforeach
> > +
> > +foreach marg: machine[2]
> > + if marg[0] == impl_pn
> > + foreach flag: marg[1]
> > + if cc.has_argument(flag)
> > + machine_args += flag
> > + endif
> > + endforeach
> > + # Apply any extra machine specific flags.
> > + foreach flag: marg.get(2, flags_default_extra)
> > + if flag.length() > 0
> > + dpdk_conf.set(flag[0], flag[1])
> > + message('Setting flag: @0@:
> > @1@'.format(flag[0],
> flag[1]))
> > + endif
> > + endforeach
> > + endif
> > +endforeach
> > message(machine_args)
> >
> > if (cc.get_define('__ARM_NEON', args: machine_args) != '' or
> > --
> > 2.20.1
> >
