Re: [dpdk-dev] [PATCH v4] eal/cpuflags: add x86 based cpu flags

[Ray Kinsella <mdr@ashroe.eu>]

On 27/04/2020 10:31, Laatz, Kevin wrote:
>  
>> (replying this time to the list)
>>
>> On 25/04/2020 17:04, Thomas Monjalon wrote:
>>> 16/04/2020 13:00, Kevin Laatz:
>>>> This patch adds CPU flags which will enable the detection of ISA
>>>> features available on more recent x86 based CPUs.
>>> [...]
>>>> --- a/devtools/libabigail.abignore
>>>> +++ b/devtools/libabigail.abignore
>>>> +; Ignore this enum update as it should not be allocated by the
>>>> +application [suppress_type]
>>>> +	type_kind = enum
>>>> +	name = rte_cpu_flag_t
>>>> +	changed_enumerators = RTE_CPUFLAG_NUMFLAGS
>>>
>>> The justification is not correct.
>>> The application is allowed to use RTE_CPUFLAG_NUMFLAGS in array
>> allocation.
>>> But no API is returning a CPU flag, so the new flags will remain
>>> unknown to the application.
>>>
>>> However, there is a behaviour change:
>>> The functions rte_cpu_get_flag_name() and rte_cpu_get_flag_enabled()
>>> will now accept new values, which were previously considered as an error.
>>> Is it an ABI breakage? I would say no.
>>
>> We saw something similar with the Cryptodev's rte_crypto_sym_xform_type
>> also.
>> Libabigail appears to be particularly sensitive to changes to enumerations.
>> Leaving it to the user to decide if there is a problem.
>>
>> I am seeing a bit of weirdness though between versions of libabigail.
>> 1.7.1 seems to fine with the change, however 1.2 is reporting an issue.
>>
>> Kevin - what version are you using?
> 
> I'm using version 1.6.0

right you are either on Fedora 31 or some Ubuntu v19.xx, right?

> 
>>
>>>
>>> PS: Who is REALLY maintaining the ABI?
>>> We really miss someone who carefully check all these things, and take
>>> care of the doc and tooling.
>>>
>>>
>>
>> I would say that I am missing these changes to libabigail.ignore, which would
>> be useful.
>> Should we consolidate the ABI Policy and ABI Versioning sections of the
>> MAINTAINERS file?
>