Re: [PATCH bpf-next] bpf: Allow to use kfunc XDP hints and frags together

[Larysa Zaremba <larysa.zaremba@intel.com>]

On Thu, Sep 14, 2023 at 06:38:15PM +0200, Maciej Fijalkowski wrote:
> On Thu, Sep 14, 2023 at 10:37:11AM +0200, Larysa Zaremba wrote:
> > There is no fundamental reason, why multi-buffer XDP and XDP kfunc RX hints
> > cannot coexist in a single program.
> > 
> > Allow those features to be used together by modifying the flags conditions.
> > 
> > Suggested-by: Stanislav Fomichev <sdf@google.com>
> > Link: https://lore.kernel.org/bpf/CAKH8qBuzgtJj=OKMdsxEkyML36VsAuZpcrsXcyqjdKXSJCBq=Q@mail.gmail.com/
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> 
> Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> 
> Though it would be worth spelling out something in the commit msg about
> additional check you're adding (frags flag can't go without dev bound)
>

Ok, I'll add to the commit message the below:

Frags are allowed only if program is dev-bound-only, but not if it is requesting 
bpf offload.

> > ---
> >  kernel/bpf/offload.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> > index ee35f33a96d1..43aded96c79b 100644
> > --- a/kernel/bpf/offload.c
> > +++ b/kernel/bpf/offload.c
> > @@ -232,7 +232,11 @@ int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
> >  	    attr->prog_type != BPF_PROG_TYPE_XDP)
> >  		return -EINVAL;
> >  
> > -	if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
> > +	if (attr->prog_flags & ~(BPF_F_XDP_DEV_BOUND_ONLY | BPF_F_XDP_HAS_FRAGS))
> > +		return -EINVAL;
> > +
> > +	if (attr->prog_flags & BPF_F_XDP_HAS_FRAGS &&
> > +	    !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY))
> >  		return -EINVAL;
> >  
> >  	if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&
> > -- 
> > 2.41.0
> > 
> >