Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230406130205.49996-1-kal.conley@dectris.com>
 <20230406130205.49996-2-kal.conley@dectris.com> <87sfdckgaa.fsf@toke.dk>
 <ZDBEng1KEEG5lOA6@boxer> <CAHApi-nuD7iSY7fGPeMYiNf8YX3dG27tJx1=n8b_i=ZQdZGZbw@mail.gmail.com>
 <875ya12phx.fsf@toke.dk> <CAHApi-=rMHt7uR8Sw1Vw+MHDrtkyt=jSvTvwz8XKV7SEb01CmQ@mail.gmail.com>
 <87ile011kz.fsf@toke.dk>
In-Reply-To: <87ile011kz.fsf@toke.dk>
From:   Kal Cutter Conley <kal.conley@dectris.com>
Date:   Fri, 14 Apr 2023 18:36:04 +0200
Message-ID: <CAHApi-=ODe-WtJ=m6bycQhKoQxb+kk2Yk9Fx5SgBsWUuWT_u-A@mail.gmail.com>
Subject: Re: [PATCH bpf-next v3 1/3] xsk: Support UMEM chunk_size > PAGE_SIZE
To:     =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke@redhat.com>
Cc:     Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <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
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> 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?