From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH v7 net-next 5/5] net: ethernet: ti: cpsw: add XDP support Date: Fri, 5 Jul 2019 13:13:54 +0200 Message-ID: <20190705131354.15a9313c@carbon> References: <20190704231406.27083-1-ivan.khoronzhuk@linaro.org> <20190704231406.27083-6-ivan.khoronzhuk@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190704231406.27083-6-ivan.khoronzhuk@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Ivan Khoronzhuk Cc: grygorii.strashko@ti.com, davem@davemloft.net, ast@kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, ilias.apalodimas@linaro.org, netdev@vger.kernel.org, daniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com, brouer@redhat.com List-Id: linux-omap@vger.kernel.org On Fri, 5 Jul 2019 02:14:06 +0300 Ivan Khoronzhuk wrote: > +static int cpsw_xdp_tx_frame(struct cpsw_priv *priv, struct xdp_frame *xdpf, > + struct page *page) > +{ > + struct cpsw_common *cpsw = priv->cpsw; > + struct cpsw_meta_xdp *xmeta; > + struct cpdma_chan *txch; > + dma_addr_t dma; > + int ret, port; > + > + xmeta = (void *)xdpf + CPSW_XMETA_OFFSET; > + xmeta->ndev = priv->ndev; > + xmeta->ch = 0; > + txch = cpsw->txv[0].ch; > + > + port = priv->emac_port + cpsw->data.dual_emac; > + if (page) { > + dma = page_pool_get_dma_addr(page); > + dma += xdpf->data - (void *)xdpf; This code is only okay because this only happens for XDP_TX, where you know this head-room calculation will be true. The "correct" calculation of the head-room would be: dma += xdpf->headroom + sizeof(struct xdp_frame); The reason behind not using xdpf pointer itself as "data_hard_start", is to allow struct xdp_frame to be located in another memory area. This will be useful for e.g. AF_XDP transmit, or other zero-copy transmit to go through ndo_xdp_xmit() (as we don't want userspace to be-able to e.g. "race" change xdpf->len during transmit/DMA-completion). > + ret = cpdma_chan_submit_mapped(txch, cpsw_xdpf_to_handle(xdpf), > + dma, xdpf->len, port); > + } else { > + if (sizeof(*xmeta) > xdpf->headroom) { > + xdp_return_frame_rx_napi(xdpf); > + return -EINVAL; > + } > + > + ret = cpdma_chan_submit(txch, cpsw_xdpf_to_handle(xdpf), > + xdpf->data, xdpf->len, port); > + } -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer