Re: [dpdk-dev] [PATCH] build: enable to build on power10 or newer for ppc

[Thinh Tran <thinhtr@linux.vnet.ibm.com>]

Thanks David for reviewing.
I'll fix the patch with cross compilation in mind.

Regards,
Thinh Tran


On 7/22/2021 3:20 PM, David Marchand wrote:
> On Wed, Jul 21, 2021 at 11:14 PM Thinh Tran <thinhtr@linux.vnet.ibm.com> wrote:
>>
>> A older version of complier would fail to generate code for new Power
> 
> compiler
> 
>> CPUs when it uses "-mcpu=native" argument.
>> This patch will test if the compiler supports the current Power CPU type
>> then proceeds with "-mcpu=native" argument, else it tries with older type.
>> Limit to two older CPU type levels.
> 
> Such a change seems a bit late for 21.08, and is broken (see below).
> In any case, I would need a review from ppc maintainer.
> 
> 
>>
>> Signed-off-by: Thinh Tran <thinhtr@linux.vnet.ibm.com>
>> ---
>>   config/ppc/check_cpu_platform.sh |  2 ++
>>   config/ppc/meson.build           | 40 +++++++++++++++++++++++++-------
>>   2 files changed, 34 insertions(+), 8 deletions(-)
>>   create mode 100644 config/ppc/check_cpu_platform.sh
>>
>> diff --git a/config/ppc/check_cpu_platform.sh b/config/ppc/check_cpu_platform.sh
>> new file mode 100644
>> index 0000000000..cdea24561b
>> --- /dev/null
>> +++ b/config/ppc/check_cpu_platform.sh
>> @@ -0,0 +1,2 @@
>> +#! /bin/sh
>> +LD_SHOW_AUXV=1 /bin/true | awk '/AT_PLATFORM/ {print $2}'|sed  's/\power//'
>> diff --git a/config/ppc/meson.build b/config/ppc/meson.build
>> index adf49e1f42..05aa860cfd 100644
>> --- a/config/ppc/meson.build
>> +++ b/config/ppc/meson.build
>> @@ -7,16 +7,40 @@ endif
>>   dpdk_conf.set('RTE_ARCH', 'ppc_64')
>>   dpdk_conf.set('RTE_ARCH_PPC_64', 1)
>>
>> -# RHEL 7.x uses gcc 4.8.X which doesn't generate code for Power 9 CPUs,
>> -# though it will detect a Power 9 CPU when the "-mcpu=native" argument
>> -# is used, resulting in a build failure.
>> -power9_supported = cc.has_argument('-mcpu=power9')
>> -if not power9_supported
>> -    cpu_instruction_set = 'power8'
>> -    machine_args = ['-mcpu=power8', '-mtune=power8']
>> -    dpdk_conf.set('RTE_MACHINE','power8')
>> +# Checking compiler for supporting Power CPU platform
>> +# For newer Power(N) System that current gcc may not supoort it yet,
>> +# it falls back and try  N-1 and N-2
> 
> double space unneeded.
> Plus, wording reads odd to me.
> 
>> +check_cpu = find_program(join_paths(meson.current_source_dir(),
>> +                 'check_cpu_platform.sh'))
> 
> Why do you need a separate script?
> The value it returns is constant on a given system.
> 
> 
> Looking at the script itself, this breaks cross compilation.
> 
> Compiler for C supports arguments -Wno-missing-field-initializers
> -Wmissing-field-initializers: YES (cached)
> Program /home/dmarchan/dpdk/config/ppc/check_cpu_platform.sh found: YES
> 
> ../../dpdk/config/ppc/meson.build:18:0: ERROR: String 'x86_64' cannot
> be converted to int
> 
> A full log can be found at
> /home/dmarchan/builds/build-ppc64le-power8/meson-logs/meson-log.txt
> FAILED: build.ninja
> /usr/bin/meson --internal regenerate /home/dmarchan/dpdk
> /home/dmarchan/builds/build-ppc64le-power8 --backend ninja
> ninja: error: rebuilding 'build.ninja': subcommand failed
> 
> 
> 
>> +
>> +target_cpu = run_command(check_cpu.path()).stdout().strip()
>> +
>> +cpu_int = target_cpu.to_int()
>> +cpu_flag = '-mcpu=power@0@'
>> +tune_flag = '-mtune=power@0@'
>> +machine_type = 'power@0@'
>> +debug = 'configure the compiler to build DPDK for POWER@0@ platform'
>> +
>> +if cc.has_argument(cpu_flag.format(cpu_int))
>> +
>> +  # target system cpu is supported by the compiler, use '-mcpu=native'
>> +  message(debug.format(target_cpu+'_native'))
>> +  machine_args = ['-mcpu=native']
>> +  dpdk_conf.set('RTE_MACHINE',machine_type.format(cpu_int))
>> +elif cc.has_argument(cpu_flag.format(cpu_int-1))
>> +  message(debug.format(cpu_int-1))
>> +  machine_args = [cpu_flag.format(cpu_int-1),tune_flag.format(cpu_int-1)]
>> +  dpdk_conf.set('RTE_MACHINE',machine_type.format(cpu_int-1))
>> +elif cc.has_argument(cpu_flag.format(cpu_int-2))
>> +  message(debug.format(cpu_int-2))
>> +  machine_args = [cpu_flag.format(cpu_int-2),tune_flag.format(cpu_int-2)]
>> +  dpdk_conf.set('RTE_MACHINE',machine_type.format(cpu_int-2))
>> +else
>> +  error('The compiler does not support POWER@0@ platform' .format(cpu_int))
>>   endif
>>
>> +
>> +
> 
> One line is enough.
> 
> 
> 
>>   # Certain POWER9 systems can scale as high as 1536 LCORES, but setting such a
>>   # high value can waste memory, cause timeouts in time limited autotests, and is
>>   # unlikely to be used in many production situations.  Similarly, keeping the
>> --
>> 2.17.1
>>
> 
>