netdev - Re: [PATCH v2 net-next 8/9] bpf: nfp: Report bpf_prog ID during XDP_QUERY

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Date:   Tue, 13 Jun 2017 20:19:53 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: Re: [PATCH v2 net-next 8/9] bpf: nfp: Report bpf_prog ID during
 XDP_QUERY_PROG

On Tue, Jun 13, 2017 at 07:19:50PM -0700, Jakub Kicinski wrote:
> On Tue, 13 Jun 2017 17:37:50 -0700, Martin KaFai Lau wrote:
> > On Tue, Jun 13, 2017 at 04:52:32PM -0700, Jakub Kicinski wrote:
> > > On Tue, 13 Jun 2017 14:08:40 -0700, Martin KaFai Lau wrote:
> > > > -	case XDP_QUERY_PROG:
> > > > -		xdp->prog_attached = !!nn->dp.xdp_prog;
> > > > +	case XDP_QUERY_PROG: {
> > > > +		const struct bpf_prog *xdp_prog;
> > > > +
> > > > +		xdp_prog = nn->dp.xdp_prog;
> > > > +		if (xdp_prog) {
> > > > +			xdp->prog_id = xdp_prog->aux->id;
> > > > +			xdp->prog_attached = true;
> > > > +		} else {
> > > > +			xdp->prog_id = 0;
> > > > +			xdp->prog_attached = false;
> > > > +		}
> > > >  		return 0;
> > > > +	}
> > >
> > > I'm sorry to nit pick but it could be done on a single line:
> > >
> > > 	case XDP_QUERY_PROG:
> > > 		xdp->prog_attached = !!nn->dp.xdp_prog;
> > > +		xdp->prog_id = nn->dp.xdp_prog ? nn->dp.xdp_prog->aux->id : 0;
> > >  		return 0;
> > >  	default:
> > >  		return -EINVAL;
> > OK...
> >
> > >
> > >
> > > What would be even cooler is a helper like this:
> > >
> > > static inline u32 bpf_prog_id(struct bpf_prog *prog)
> > > {
> > > 	if (!prog)
> > > 		return 0;
> > > 	return prog->aux->id;
> > > }
> > >
> > > in linux/bpf.h.
> > Good idea.
>
> You may actually have to add that into a source file, because bpf.h
> does not know the definition of struct bpf_prog :(
Yeah. filter.h seems not working well either.
It looks good to me at the first thought.  After a second thought,
in the future, I am not so sure having a getter for every fields
in bpf_prog.

I can put bpf_prog_id() in nfp_net_common.c only.
or do 'xdp->prog_id = nn->dp.xdp_prog ? nn->dp.xdp_prog->aux->id : 0;'
as you suggested earlier also.
I am fine either way.  Your call ;)

>
> > I had been thinking I may not need to change all the
> > drivers now.  I did that in v1 because I wanted to remove
> > prog_attached which is redundant.  With prog_attached reserved,
> > prog_id is optional.
> >
> > Considering I don't have all the hardwares to test it,  I think
> > it may make more sense for me to only change the HW that I have?
>
> Coccinelle to the rescue?
>
> @@
> expression ex;
> @@
> 		xdp->prog_attached = !!(ex);
> +		xdp->prog_id = bpf_prog_id(ex);
Good to know Coccinelle.  First hit in my browser ;)

Changing it is fine.  I meant I cannot test it without the HW but
they are at least compiler tested now.

Regardless, I think I will give it one more try in v3.