netdev - Re: [PATCH bpf-next] bpf: introduce BPF_JIT_ALWAYS

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Date:   Mon, 8 Jan 2018 16:02:25 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Alexei Starovoitov <ast@...nel.org>, davem@...emloft.net,
        torvalds@...ux-foundation.org, jannh@...gle.com,
        alan@...ux.intel.com, netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next] bpf: introduce BPF_JIT_ALWAYS_ON config

On Mon, 8 Jan 2018 22:59:04 +0100, Daniel Borkmann wrote:
> > @@ -1453,6 +1457,11 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
> >  	 */
> >  	*err = bpf_check_tail_call(fp);
> >  
> > +#ifdef CONFIG_BPF_JIT_ALWAYS_ON
> > +	if (!fp->jited)
> > +		*err = -ENOTSUPP;
> > +#endif  

I think programs JITed for offload won't have fp->jited set, but
those are pretty safe from CPU bugs.  Should we set fp->jited = 1; in
bpf_prog_offload_compile()?  Just throwing "&& !bpf_prog_is_dev_bound()"
in here seems cleaner to me.

FWIW if you have netdevsim compiled and recent iproute2, this will
work to check:

# ip link add type netdevsim
# ip link set netdevsim0 xdpoffload obj ~/xdp/pass.o