Re: [dpdk-dev] [PATCH 2/3] arm64: acl: add neon based acl implementation

[Jan Viktorin <viktorin@rehivetech.com>]

On Tue, 3 Nov 2015 10:23:55 +0000
"Ananyev, Konstantin" <konstantin.ananyev@intel.com> wrote:

> > Hi Konstantin,  
> > >
> > > On ARM, is there any specific cpu flag that you can use to determine is NEON
> > > isa is supported or not?  
> > 
> > Yes, on armv7(RTE_CPUFLAG_NEON). On armv8-a NEON is mandatory.
> >   
> > > It would be good to avoid extra conditional compilation here if possible.  
> > neon acl is verified/ported only on armv8. While adding the armv7 support the
> > check can be extended for cpuflag based on RTE_CPUFLAG_NEON on armv7  
> 
> Ok, and is there a flag that allows to distinguish between armv7 and arm8 then at runtime?
> It is probably ok like that, but with all that conditional compilations it gets too messy.
> Another thing - if you can distinguish between armv7 and armv8 at runtime, then you probably
> can set alg = RTE_ACL_CLASSIFY_DEFAULT for armv7 and alg = RTE_ACL_CLASSIFY_NEON for arm8?
> Konstantin

The ARMv7 provides "v7l" in the AT_PLATFORM and the ARMv8 gives
"aarach64". However, I am afraid, as these are two distinct platforms
(with distinct cpuflags), we cannot use the cpuflags easily for this.

Is there an API in DPDK which allows to ask globally: "what platform am
I running on?"?

Jan

> 
> >   
> > > Another question - did I get it right that NEON isa is supported on all
> > > possible RTE_ARCH_ARM64 cpu models you plan to support?  
> > 
> > Yes


-- 
  Jan Viktorin                E-mail: Viktorin@RehiveTech.com
  System Architect            Web:    www.RehiveTech.com
  RehiveTech
  Brno, Czech Republic