netdev - Re: [PATCH bpf] Revert "xdp: add NULL pointer check in __xdp

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Message-ID: <20180810092625.1ad1cce4@cakuba.netronome.com>
Date:   Fri, 10 Aug 2018 09:26:25 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...com>,
        Netdev <netdev@...r.kernel.org>, Taehee Yoo <ap420073@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>, kafai@...com
Subject: Re: [PATCH bpf] Revert "xdp: add NULL pointer check in
 __xdp_return()"

On Fri, 10 Aug 2018 17:16:45 +0200, Björn Töpel wrote:
> Den fre 10 aug. 2018 kl 16:10 skrev Daniel Borkmann <daniel@...earbox.net>:
> >
> > On 08/10/2018 11:28 AM, Björn Töpel wrote:  
> > > From: Björn Töpel <bjorn.topel@...el.com>
> > >
> > > This reverts commit 36e0f12bbfd3016f495904b35e41c5711707509f.
> > >
> > > The reverted commit adds a WARN to check against NULL entries in the
> > > mem_id_ht rhashtable. Any kernel path implementing the XDP (generic or
> > > driver) fast path is required to make a paired
> > > xdp_rxq_info_reg/xdp_rxq_info_unreg call for proper function. In
> > > addition, a driver using a different allocation scheme than the
> > > default MEM_TYPE_PAGE_SHARED is required to additionally call
> > > xdp_rxq_info_reg_mem_model.
> > >
> > > For MEM_TYPE_ZERO_COPY, an xdp_rxq_info_reg_mem_model call ensures
> > > that the mem_id_ht rhashtable has a properly inserted allocator id. If
> > > not, this would be a driver bug. A NULL pointer kernel OOPS is
> > > preferred to the WARN.
> > >
> > > Suggested-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > > Signed-off-by: Björn Töpel <bjorn.topel@...el.com>  
> >
> > Given the last bpf pr went out yesterday night, I've applied this to
> > bpf-next (worst case we can just route it via stable), thanks!  
> 
> Ah, right! Thanks!
> 
> bpf-next is OK. (Since this path is currently not used yet by any driver... :-()

Wasn't this dead code, anyway?  The frame return path is for redirects,
and one can't convert_to_xdp_frame presently?