Re: [PATCH 6/6] ppc: ebpf/jit: Implement JIT compiler for extended BPF

[Naveen N. Rao]

On 2016/06/07 03:56PM, Alexei Starovoitov wrote:
> On Tue, Jun 07, 2016 at 07:02:23PM +0530, Naveen N. Rao wrote:
> > PPC64 eBPF JIT compiler.
> > 
> > Enable with:
> > echo 1 > /proc/sys/net/core/bpf_jit_enable
> > or
> > echo 2 > /proc/sys/net/core/bpf_jit_enable
> > 
> > ... to see the generated JIT code. This can further be processed with
> > tools/net/bpf_jit_disasm.
> > 
> > With CONFIG_TEST_BPF=m and 'modprobe test_bpf':
> > test_bpf: Summary: 305 PASSED, 0 FAILED, [297/297 JIT'ed]
> > 
> > ... on both ppc64 BE and LE.
> 
> Nice. That's even better than on x64 which cannot jit one test:
> test_bpf: #262 BPF_MAXINSNS: Jump, gap, jump, ... jited:0 168 PASS
> which was designed specifically to hit x64 jit pass limit.
> ppc jit has predicatble number of passes and doesn't have this problem
> as expected. Great.

Yes, that's thanks to the clever handling of conditional branches by 
Matt -- we always emit 2 instructions for this reason (encoded in 
PPC_BCC() macro).

> 
> > The details of the approach are documented through various comments in
> > the code.
> > 
> > Cc: Matt Evans <matt@xxxxxxxxxx>
> > Cc: Denis Kirjanov <kda@xxxxxxxxxxxxxxxxx>
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Alexei Starovoitov <ast@xxxxxx>
> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> > ---
> >  arch/powerpc/Kconfig                  |   3 +-
> >  arch/powerpc/include/asm/asm-compat.h |   2 +
> >  arch/powerpc/include/asm/ppc-opcode.h |  20 +-
> >  arch/powerpc/net/Makefile             |   4 +
> >  arch/powerpc/net/bpf_jit.h            |  53 +-
> >  arch/powerpc/net/bpf_jit64.h          | 102 ++++
> >  arch/powerpc/net/bpf_jit_asm64.S      | 180 +++++++
> >  arch/powerpc/net/bpf_jit_comp64.c     | 956 ++++++++++++++++++++++++++++++++++
> >  8 files changed, 1317 insertions(+), 3 deletions(-)
> >  create mode 100644 arch/powerpc/net/bpf_jit64.h
> >  create mode 100644 arch/powerpc/net/bpf_jit_asm64.S
> >  create mode 100644 arch/powerpc/net/bpf_jit_comp64.c
> 
> don't see any issues with the code.
> Thank you for working on this.
> 
> Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>

Thanks, Alexei!


Regards,
Naveen