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

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Message-ID: <87lgmibi44.fsf@concordia.ellerman.id.au>
Date:   Thu, 17 Aug 2017 20:31:39 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Daniel Borkmann <daniel@...earbox.net>, 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

Daniel Borkmann <daniel@...earbox.net> writes:
> On 08/16/2017 01:10 PM, Michael Ellerman wrote:
>> Daniel Borkmann <daniel@...earbox.net> writes:
>>> On 08/16/2017 07:15 AM, Michael Ellerman wrote:
>>>> 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.
>>
>> We could.
>>
>> Does a user of the sysctl want/need to know the difference though? Or do
>> they just want to turn on "the JIT"?
>
> They would just turn it on, but I think it would be nice to inform
> them which archs support eBPF (which is a superset of cBPF in term
> of what can be jited), so in case they have some native eBPF programs
> they would see whether these can also be jited.

OK. v2 just sent.

The text could probably use some more tweaking to mention the other
things BPF is used for these days, but I didn't really feel qualified to
do that.

cheers