Re: [dpdk-dev] [PATCH v6 2/2] net/hns3: refactor SVE code compile method

[fengchengwen <fengchengwen@huawei.com>]

On 2021/5/19 23:02, Ferruh Yigit wrote:
> On 5/19/2021 2:25 PM, Chengwen Feng wrote:
>> Currently, the SVE code is compiled only when -march supports SVE
>> (e.g. '-march=armv8.2a+sve'), there maybe some problem[1] with this
>> approach.
>>
>> The solution:
>> a. If the minimum instruction set support SVE then compiles it.
>> b. Else if the compiler support SVE then compiles it.
>> c. Otherwise don't compile it.
>>
>> [1] https://mails.dpdk.org/archives/dev/2021-April/208189.html
>>
>> Fixes: 8c25b02b082a ("net/hns3: fix enabling SVE Rx/Tx")
>> Fixes: 952ebacce4f2 ("net/hns3: support SVE Rx")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> 
> The patch passes the CI build [1], but in that test sve file is not compiled at
> all because of missing header file [2].
> 

Yes, it was designed as it.
In hns3 meson.build we call cc.check_header('arm_sve.h'), and gcc9 don't have this headerfile.

> I wonder if the warning caused by conflicting switch [3] is still valid, we need
> a platform that sve file is compiled to verify this. Do you have this
> environment, that sets '-mcpu=armv8.1-a'.
> 

It already fix by filterout '-march' '-mcpu' '-mtune' in hns3 meson.build of this patch
If don't add the above filtout logic:
  a) Test result with gcc8.3 and crossfile thunder2:
    cc1: warning: switch ‘-mcpu=thunderx2t99’ conflicts with ‘-march=armv8.2-a+sve’ switch
  b) Test result with gcc9.2 and crossfile thunder2:
    cc1: warning: switch ‘-mcpu=armv8.1-a’ conflicts with ‘-march=armv8.2-a’ switch

Note: the gcc8.3/9.2 version detail:
  ./aarch64-linux-gnu-gcc --version
  aarch64-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 8.3-2019.03 (arm-rel-8.36)) 8.3.0
  ./aarch64-none-linux-gnu-gcc --version
  aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025

> 
> Btw, CI reports unit test failure, I don't think it is related with this patch
> but can you please double check?
> 

Agree, it is atomic_autotest and malloc_autotest failed, it hasn't run any hns3 driver's code.

> 
> 
> [1]
> https://lab.dpdk.org/results/dashboard/patchsets/17135/
> 
> [2]
> Check usable header "arm_sve.h" : NO
> 
> [3]
> error: switch ‘-mcpu=armv8.1-a’ conflicts with ‘-march=armv8.2-a’ switch [-Werror]
> 
>> ---
>>  drivers/net/hns3/hns3_rxtx.c |  2 +-
>>  drivers/net/hns3/meson.build | 21 ++++++++++++++++++++-
>>  2 files changed, 21 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/hns3/hns3_rxtx.c b/drivers/net/hns3/hns3_rxtx.c
>> index 1d7a769..4ef20c6 100644
>> --- a/drivers/net/hns3/hns3_rxtx.c
>> +++ b/drivers/net/hns3/hns3_rxtx.c
>> @@ -2808,7 +2808,7 @@ hns3_get_default_vec_support(void)
>>  static bool
>>  hns3_get_sve_support(void)
>>  {
>> -#if defined(RTE_ARCH_ARM64) && defined(__ARM_FEATURE_SVE)
>> +#if defined(CC_SVE_SUPPORT)
>>  	if (rte_vect_get_max_simd_bitwidth() < RTE_VECT_SIMD_256)
>>  		return false;
>>  	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SVE))
>> diff --git a/drivers/net/hns3/meson.build b/drivers/net/hns3/meson.build
>> index 53c7df7..5f9af9b 100644
>> --- a/drivers/net/hns3/meson.build
>> +++ b/drivers/net/hns3/meson.build
>> @@ -35,7 +35,26 @@ deps += ['hash']
>>  
>>  if arch_subdir == 'arm' and dpdk_conf.get('RTE_ARCH_64')
>>      sources += files('hns3_rxtx_vec.c')
>> -    if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != ''
>> +
>> +    # compile SVE when:
>> +    # a. support SVE in minimum instruction set baseline
>> +    # b. it's not minimum instruction set, but compiler support
>> +    if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != '' and cc.check_header('arm_sve.h')
>> +        cflags += ['-DCC_SVE_SUPPORT']
>>          sources += files('hns3_rxtx_vec_sve.c')
>> +    elif cc.has_argument('-march=armv8.2-a+sve') and cc.check_header('arm_sve.h')
>> +        sve_cflags = ['-DCC_SVE_SUPPORT']
>> +        foreach flag: cflags
>> +            # filterout -march -mcpu -mtune
>> +            if not (flag.startswith('-march=') or flag.startswith('-mcpu=') or flag.startswith('-mtune='))
>> +                sve_cflags += flag
>> +            endif
>> +        endforeach
>> +        hns3_sve_lib = static_library('hns3_sve_lib',
>> +                        'hns3_rxtx_vec_sve.c',
>> +                        dependencies: [static_rte_ethdev],
>> +                        include_directories: includes,
>> +                        c_args: [sve_cflags, '-march=armv8.2-a+sve'])
>> +        objs += hns3_sve_lib.extract_objects('hns3_rxtx_vec_sve.c')
>>      endif
>>  endif
>>
> 
> 
> .
>