Re: [dpdk-dev] [PATCH v8 2/4] meson: add infra to support machine specific flags

[Thomas Monjalon <thomas@monjalon.net>]

10/04/2019 18:13, jerinjacobk@gmail.com:
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> 
> Currently, RTE_* flags are set based on the implementer ID but there might
> be some micro arch specific differences from the same vendor
> eg. CACHE_LINESIZE. Add support to set micro arch specific flags.

I don't like how flags are set in config/arm/meson.build.
It is a real mess to find which flag applies to which machine.
Adding the flags_*_extra in the machine_args_* is adding more mess.

[...]
>  flags_common_default = [
>  	# Accelarate rte_memcpy. Be sure to run unit test (memcpy_perf_autotest)
>  	# to determine the best threshold in code. Refer to notes in source file
> @@ -52,12 +33,10 @@ flags_generic = [
>  	['RTE_USE_C11_MEM_MODEL', true],
>  	['RTE_CACHE_LINE_SIZE', 128]]
>  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_USE_C11_MEM_MODEL', false]]
> +	['RTE_MAX_VFIO_GROUPS', 128]]
>  flags_dpaa = [
>  	['RTE_MACHINE', '"dpaa"'],
>  	['RTE_USE_C11_MEM_MODEL', true],
> @@ -71,6 +50,27 @@ flags_dpaa2 = [
>  	['RTE_MAX_NUMA_NODES', 1],
>  	['RTE_MAX_LCORE', 16],
>  	['RTE_LIBRTE_DPAA2_USE_PHYS_IOVA', false]]
> +flags_default_extra = []
> +flags_thunderx_extra = [
> +	['RTE_MACHINE', '"thunderx"'],
> +	['RTE_USE_C11_MEM_MODEL', false]]
> +
> +machine_args_generic = [
> +	['default', ['-march=armv8-a+crc+crypto']],
> +	['native', ['-march=native']],
> +	['0xd03', ['-mcpu=cortex-a53']],
> +	['0xd04', ['-mcpu=cortex-a35']],
> +	['0xd07', ['-mcpu=cortex-a57']],
> +	['0xd08', ['-mcpu=cortex-a72']],
> +	['0xd09', ['-mcpu=cortex-a73']],
> +	['0xd0a', ['-mcpu=cortex-a75']]]
> +
> +machine_args_cavium = [
> +	['default', ['-march=armv8-a+crc+crypto','-mcpu=thunderx']],
> +	['native', ['-march=native']],
> +	['0xa1', ['-mcpu=thunderxt88'], flags_thunderx_extra],
> +	['0xa2', ['-mcpu=thunderxt81'], flags_thunderx_extra],
> +	['0xa3', ['-mcpu=thunderxt83'], flags_thunderx_extra]]

I think we should have a simpler model.
We need only to know the machine name and get all the related machine config.
In native compilation, machine name is guessed from implementor id and pn
(from config/arm/armv8_machine.py). We can directly output the machine name
from this script and leave the naming logic in this script.
In the cross-compilation config files (config/arm/*),
we can just specify the machine name.
Then every machine config (machine_args and dpdk_conf) would be specified
in some arrays based on the machine name.
Of course, we can keep some common default values.

Thoughts?