linux-kernel - Re: [PATCH net-next V2] ARM: net: support BPF_ALU

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Message-ID: <20151002152519.GA1619@Alexeis-MBP.westell.com>
Date:	Fri, 2 Oct 2015 08:25:20 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Nicolas Schichan <nschichan@...ebox.fr>
Cc:	Russell King <linux@....linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Mircea Gherzan <mgherzan@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next V2] ARM: net: support BPF_ALU | BPF_MOD
 instructions in the BPF JIT.

On Fri, Oct 02, 2015 at 05:06:47PM +0200, Nicolas Schichan wrote:
> For ARMv7 with UDIV instruction support, generate an UDIV instruction
> followed by an MLS instruction.
> 
> For other ARM variants, generate code calling a C wrapper similar to
> the jit_udiv() function used for BPF_ALU | BPF_DIV instructions.
> 
> Some performance numbers reported by the test_bpf module (the duration
> per filter run is reported in nanoseconds, between "jitted:<x>" and
> "PASS":
> 
> ARMv7 QEMU nojit:	test_bpf: #3 DIV_MOD_KX jited:0 2196 PASS
> ARMv7 QEMU jit:		test_bpf: #3 DIV_MOD_KX jited:1 104 PASS
> ARMv5 QEMU nojit:	test_bpf: #3 DIV_MOD_KX jited:0 2176 PASS
> ARMv5 QEMU jit:		test_bpf: #3 DIV_MOD_KX jited:1 1104 PASS
> ARMv5 kirkwood nojit:	test_bpf: #3 DIV_MOD_KX jited:0 1103 PASS
> ARMv5 kirkwood jit:	test_bpf: #3 DIV_MOD_KX jited:1 311 PASS
> 
> Signed-off-by: Nicolas Schichan <nschichan@...ebox.fr>

run-time check for zero is there, so looks good to me
Acked-by: Alexei Starovoitov <ast@...nel.org>

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