eBPF on powerpc

[Naveen N. Rao]

Hi Christophe,

Christophe Leroy wrote:
> Hi Naveen,
> 
> Few years ago, you implemented eBPF on PPC64.
> 
> Is there any reason for implementing it for PPC64 only ?

I focused on ppc64 since eBPF is a 64-bit VM and it was more 
straight-forward to target.

> Is there something that makes it impossible to have eBPF for PPC32 as 
> well ?

No, I just wasn't sure if it would be performant enough to warrant it.  
Since then however, there have been arm32 and riscv 32-bit JIT 
implementations and atleast the arm32 JIT seems to be showing ~50% 
better performance compared to the interpreter (*). So, it would be 
worthwhile to add support for ppc32.

Note that there might be a few instructions which would be difficult to 
support on 32-bit, but those can fallback to the interpreter, while 
allowing other programs to be JIT'ed.


- Naveen

(*) 
http://lkml.kernel.org/r/CAGXu5jLYunVCJGCfHPebKDaoQ71hdMGq4HhdDxTYpBQw_HXUYQ@mail.gmail.com
(*) http://lkml.kernel.org/r/b63fae4b-cb74-1928-b210-80914f3c8995@fb.com
(*) http://lkml.kernel.org/r/20200305050207.4159-1-luke.r.nels@gmail.com