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

[Daniel Borkmann]

On 08/16/2017 01:10 PM, Michael Ellerman wrote:
> Daniel Borkmann <daniel@xxxxxxxxxxxxx> writes:
> > 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@xxxxxxxxxxxxxx>
> >
> > 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.
>
> 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.