Re: [dpdk-dev] [PATCH v5 2/2] build: add support for detecting march on ARM

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Jan 22, 2018 at 05:16:49PM +0530, Pavan Nikhilesh wrote:
> Added support for detecting march and mcpu by reading midr_el1 register.
> The implementer, primary part number values read can be used to figure
> out the underlying arm cpu.
> 
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> ---
>  app/test-pmd/meson.build    |  2 +-
>  config/arm/armv8_machine.py | 18 +++++++++
>  config/arm/meson.build      | 95 +++++++++++++++++++++++++++++++++++++++++----
>  config/meson.build          | 19 ++++-----
>  drivers/meson.build         |  2 +-
>  examples/meson.build        |  2 +-
>  lib/meson.build             |  2 +-
>  meson.build                 |  2 +-
>  test/test/meson.build       |  2 +-
>  9 files changed, 121 insertions(+), 23 deletions(-)
>  create mode 100755 config/arm/armv8_machine.py
> 
> diff --git a/app/test-pmd/meson.build b/app/test-pmd/meson.build
> index e819677a5..2a3f0ba1f 100644
> --- a/app/test-pmd/meson.build
> +++ b/app/test-pmd/meson.build
> @@ -45,7 +45,7 @@ endif
>  
>  executable('dpdk-testpmd',
>  	sources,
> -	c_args: machine_arg,
> +	c_args: machine_args,
>  	link_whole: link_libs,
>  	dependencies: dep_objs,
>  	install_rpath: join_paths(get_option('prefix'), driver_install_path),
> diff --git a/config/arm/armv8_machine.py b/config/arm/armv8_machine.py
> new file mode 100755
> index 000000000..404866d2f
> --- /dev/null
> +++ b/config/arm/armv8_machine.py
> @@ -0,0 +1,18 @@
> +#!/usr/bin/python
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2017 Cavium, Inc
> +
> +ident = []
> +fname = '/sys/devices/system/cpu/cpu0/regs/identification/midr_el1'
> +with open(fname) as f:
> +    content = f.read()
> +
> +midr_el1 = (int(content.rstrip('\n'), 16))
> +
> +ident.append(hex((midr_el1 >> 24) & 0xFF))  # Implementer
> +ident.append(hex((midr_el1 >> 20) & 0xF))   # Variant
> +ident.append(hex((midr_el1 >> 16) & 0XF))   # Architecture
> +ident.append(hex((midr_el1 >> 4) & 0xFFF))  # Primary Part number
> +ident.append(hex(midr_el1 & 0xF))           # Revision
> +
> +print(' '.join(ident))
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index f05de4c2c..212b94499 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -5,28 +5,107 @@
>  # for checking defines we need to use the correct compiler flags
>  march_opt = '-march=@0@'.format(machine)
>  
> -dpdk_conf.set('RTE_FORCE_INTRINSICS', 1)
> -if cc.sizeof('void *') == 8
> -	dpdk_conf.set('RTE_CACHE_LINE_SIZE', 128)
> -	dpdk_conf.set('RTE_ARCH_ARM64', 1)
> -	dpdk_conf.set('RTE_ARCH_64', 1)
> +machine_args_generic = [
> +	['default', ['-march=armv8-a+crc+crypto']]]
> +machine_args_cavium = [
> +	['default', ['-march=armv8-a+crc+crypto','-mcpu=thunderx']],
> +	['0xa1', ['-mcpu=thunderxt88']],
> +	['0xa2', ['-mcpu=thunderxt81']],
> +	['0xa3', ['-mcpu=thunderxt83']]]
> +
> +flags_generic = [[]]
> +flags_cavium = [
> +	['RTE_MACHINE', '"thunderx"'],
> +	['RTE_CACHE_LINE_SIZE', 128],
> +	['RTE_MAX_NUMA_NODES', 2],
> +	['RTE_MAX_LCORE', 96],
> +	['RTE_MAX_VFIO_GROUPS', 128],
> +	['RTE_RING_USE_C11_MEM_MODEL', false]]
> +
> +impl_generic = ['Generic armv8', flags_generic, machine_args_generic]
> +impl_0x43 = ['Cavium', flags_cavium, machine_args_cavium]
> +
> +if cc.get_define('__clang__') != ''
> +	dpdk_conf.set_quoted('RTE_TOOLCHAIN', 'clang')
> +	dpdk_conf.set('RTE_TOOLCHAIN_CLANG', 1)
>  else
> +	dpdk_conf.set_quoted('RTE_TOOLCHAIN', 'gcc')
> +	dpdk_conf.set('RTE_TOOLCHAIN_GCC', 1)
> +endif
> +
> +dpdk_conf.set('RTE_FORCE_INTRINSICS', 1)
> +
> +if cc.sizeof('void *') != 8
>  	dpdk_conf.set('RTE_CACHE_LINE_SIZE', 64)
>  	dpdk_conf.set('RTE_ARCH_ARM', 1)
>  	dpdk_conf.set('RTE_ARCH_ARMv7', 1)
> +else
> +	dpdk_conf.set('RTE_CACHE_LINE_SIZE', 128)
> +	dpdk_conf.set('RTE_ARCH_ARM64', 1)
> +	dpdk_conf.set('RTE_ARCH_64', 1)
> +
> +	machine = []
> +	cmd_generic = ['generic', '', '', 'default', '']
> +	cmd_output = cmd_generic # Set generic by default
> +	machine_args = [] # Clear previous machine args
> +	if 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().strip().split(' ')
> +		endif
> +		# Set to generic if variable is not found
> +		machine = get_variable('impl_' + cmd_output[0], 'generic')
> +	endif
> +
> +	if machine == 'generic'
> +		machine = impl_generic
> +		cmd_output = cmd_generic
> +	endif
> +
> +	message('Implementer : ' + machine[0])

When cross-compiling for arm I get an error at this line:

  Meson encountered an error in file config/arm/meson.build, line 69, column 1:
  Index 0 out of bounds of array of size 0.

Regards,
/Bruce