linux-kernel - Re: [PATCH] bpf: Update sysctl documentation to list all supported architectures

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Message-ID: <5993FFC9.8010206@iogearbox.net>
Date:   Wed, 16 Aug 2017 10:18:17 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Michael Ellerman <mpe@...erman.id.au>, ast@...nel.org
CC:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: Update sysctl documentation to list all supported
 architectures

Hi Michael,

On 08/16/2017 07:15 AM, Michael Ellerman wrote:
> The sysctl documentation states that the JIT is only available on
> x86_64, which is no longer correct.
>
> Update the list to include all architectures that enable HAVE_CBPF_JIT
> or HAVE_EBPF_JIT under some configuration.
>
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>

Thanks for the patch!

>   Documentation/sysctl/net.txt | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
> index 14db18c970b1..f68356024d09 100644
> --- a/Documentation/sysctl/net.txt
> +++ b/Documentation/sysctl/net.txt
> @@ -36,8 +36,9 @@ bpf_jit_enable
>   --------------
>
>   This enables Berkeley Packet Filter Just in Time compiler.
> -Currently supported on x86_64 architecture, bpf_jit provides a framework
> -to speed packet filtering, the one used by tcpdump/libpcap for example.
> +Currently supported on arm, arm64, mips, powerpc, s390, sparc and x86_64
> +architectures, bpf_jit provides a framework to speed packet filtering, the one
> +used by tcpdump/libpcap for example.

Good point, could we actually make that as a bullet list and
differentiate between cBPF and eBPF JITs, so that a user doesn't
need to run git grep HAVE_{E,C}BPF_JIT to figure it out what the
switch enables on the arch used? That would be great.

So for eBPF JITs, we have covered:

  * x86_64
  * arm64
  * ppc64
  * sparc64
  * mips64

For old cBPF, there is:

  * arm
  * mips
  * ppc
  * sparc

Thanks,
Daniel

>   Values :
>   	0 - disable the JIT (default value)
>   	1 - enable the JIT
>