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

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Date:	Wed, 8 Jun 2016 22:47:47 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Daniel Borkmann <daniel@...earbox.net>,
	Matt Evans <matt@...abs.org>, Alexei Starovoitov <ast@...com>,
	netdev@...r.kernel.org, Denis Kirjanov <kda@...ux-powerpc.org>,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	linuxppc-dev@...ts.ozlabs.org,
	"David S. Miller" <davem@...emloft.net>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Subject: Re: [PATCH 6/6] ppc: ebpf/jit: Implement JIT compiler for extended
 BPF

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@...abs.org>
> > Cc: Denis Kirjanov <kda@...ux-powerpc.org>
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Alexei Starovoitov <ast@...com>
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> > ---
> >  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@...nel.org>

Thanks, Alexei!


Regards,
Naveen