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[73.158.218.242]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-771ecfd76f3sm2396987b3a.63.2025.08.25.17.12.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Aug 2025 17:12:13 -0700 (PDT) Date: Mon, 25 Aug 2025 17:12:13 -0700 From: Stanislav Fomichev To: Jakub Kicinski Cc: Amery Hung , bpf@vger.kernel.org, netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org, mohsin.bashr@gmail.com, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, maciej.fijalkowski@intel.com, kernel-team@meta.com Subject: Re: [RFC bpf-next v1 3/7] bpf: Support pulling non-linear xdp data Message-ID: References: <20250825193918.3445531-1-ameryhung@gmail.com> <20250825193918.3445531-4-ameryhung@gmail.com> <20250825155813.763d2a59@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250825155813.763d2a59@kernel.org> On 08/25, Jakub Kicinski wrote: > On Mon, 25 Aug 2025 15:46:02 -0700 Stanislav Fomichev wrote: > > > > skb_frag_address can return NULL for unreadable frags. > > > > > > Is it safe to assume that drivers will ensure frags to be readable? It > > > seems at least mlx5 does. > > > > > > I did a quick check and found other xdp kfuncs using > > > skb_frag_address() without checking the return. > > > > The unreadable frags will always be unredabale to the host. This is TCP > > device memory, the memory on the accelerators that is not mapped onto > > the CPU. Any attempts to read that memory should gracefully error out. > > > > Can you also pls fix that other one? (not as part of the series should > > be ok) > > But we don't support mixing XDP with unreadable mem today. > Is the concern just for future proofing? Good point. I though we did add that proofing during the initial rx patch series, but I don't see any. Ignore me!