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

["Kinsella, Ray" <ray.kinsella@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Saturday 25 April 2020 17:04
> To: Kinsella, Ray <ray.kinsella@intel.com>; nhorman@tuxdriver.com;
> Laatz, Kevin <kevin.laatz@intel.com>
> Cc: dev@dpdk.org; Richardson, Bruce <bruce.richardson@intel.com>; Van
> Haaren, Harry <harry.van.haaren@intel.com>; david.marchand@redhat.com
> Subject: Re: [dpdk-dev] [PATCH v4] eal/cpuflags: add x86 based cpu
> flags
> 
> 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?

> 
> 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?