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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Alex Shi , Yanteng Si , Dongliang Mu , Michael Chan , Pavan Chebbi , Joshua Washington , Harshitha Ramamurthy , Saeed Mahameed , Tariq Toukan , Mark Bloch , Leon Romanovsky , Alexander Duyck , kernel-team@meta.com, Daniel Borkmann , Nikolay Aleksandrov , Shuah Khan , netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Stanislav Fomichev , Mina Almasry , Bobby Eshleman Subject: Re: [PATCH net-next 07/11] net: devmem: support TX over NETMEM_TX_NO_DMA devices Message-ID: References: <20260428-tcp-dm-netkit-v1-0-719280eba4d2@meta.com> <20260428-tcp-dm-netkit-v1-7-719280eba4d2@meta.com> <20260430175724.0c134a0d@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260430175724.0c134a0d@kernel.org> On Thu, Apr 30, 2026 at 05:57:24PM -0700, Jakub Kicinski wrote: > On Tue, 28 Apr 2026 15:42:04 -0700 Bobby Eshleman wrote: > > shinfo = skb_shinfo(skb); > > + if (shinfo->nr_frags == 0) > > + goto out; > > Feels tempting to cover the NETMEM_TX_NO_DMA / NETMEM_TX_NONE > cases here before we even look at the frags? That sounds good to me (had considered it, but opted out cause I felt it might look odd with the switch-case that follows). And I'll address the bug(s) the model called out here/elsewhere too. Thanks, Bobby > > > - if (shinfo->nr_frags > 0) { > > - niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0])); > > - if (net_is_devmem_iov(niov) && > > - READ_ONCE(net_devmem_iov_binding(niov)->dev) != dev) > > + niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0])); > > + if (!net_is_devmem_iov(niov)) > > + goto out; > > + > > + binding = net_devmem_iov_binding(niov); > > + > > + switch (dev->netmem_tx) { > > + case NETMEM_TX_DMA: > > + if (READ_ONCE(binding->dev) != dev) > > goto out_free; > > + break; > > + case NETMEM_TX_NO_DMA: > > + break; > > + default: /* NETMEM_TX_NONE */ > > + goto out_free; > > }