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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Kal Cutter Conley <kal.conley@dectris.com>
Cc:     Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        =?utf-8?B?QmrDtnJu?= =?utf-8?B?IFTDtnBlbA==?= <bjorn@kernel.org>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        netdev@vger.kernel.org, bpf@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v3 1/3] xsk: Support UMEM chunk_size > PAGE_SIZE
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Date:   Tue, 18 Apr 2023 12:16:58 +0200
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Kal Cutter Conley <kal.conley@dectris.com> writes:

>> In addition, presumably when using this mode, the other XDP actions
>> (XDP_PASS, XDP_REDIRECT to other targets) would stop working unless we
>> add special handling for that in the kernel? We'll definitely need to
>> handle that somehow...
>
> I am not familiar with all the details here. Do you know a reason why
> these cases would stop working / why special handling would be needed?
> For example, if I have a UMEM that uses hugepages and XDP_PASS is
> returned, then the data is just copied into an SKB right? SKBs can
> also be created directly from hugepages AFAIK. So I don't understand
> what the issue would be. Can someone explain this concern?

Well, I was asking :) It may well be that the SKB path just works; did
you test this? Pretty sure XDP_REDIRECT to another device won't, though?

-Toke