From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
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
Subject: Re: [PATCH v7 net-next 5/5] net: ethernet: ti: cpsw: add XDP support
Date: Fri, 5 Jul 2019 13:13:54 +0200 [thread overview]
Message-ID: <20190705131354.15a9313c@carbon> (raw)
In-Reply-To: <20190704231406.27083-6-ivan.khoronzhuk@linaro.org>
On Fri, 5 Jul 2019 02:14:06 +0300
Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> 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
next prev parent reply other threads:[~2019-07-05 11:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-04 23:14 [PATCH v7 net-next 0/5] net: ethernet: ti: cpsw: Add XDP support Ivan Khoronzhuk
2019-07-04 23:14 ` [PATCH v7 net-next 1/5] net: core: page_pool: add user refcnt and reintroduce page_pool_destroy Ivan Khoronzhuk
2019-07-05 7:43 ` Jesper Dangaard Brouer
2019-07-05 16:19 ` Saeed Mahameed
2019-07-04 23:14 ` [PATCH v7 net-next 2/5] net: ethernet: ti: davinci_cpdma: add dma mapped submit Ivan Khoronzhuk
2019-07-04 23:14 ` [PATCH v7 net-next 3/5] net: ethernet: ti: davinci_cpdma: allow desc split while down Ivan Khoronzhuk
2019-07-04 23:14 ` [PATCH v7 net-next 4/5] net: ethernet: ti: cpsw_ethtool: allow res " Ivan Khoronzhuk
2019-07-04 23:14 ` [PATCH v7 net-next 5/5] net: ethernet: ti: cpsw: add XDP support Ivan Khoronzhuk
2019-07-05 8:36 ` Jesper Dangaard Brouer
2019-07-05 11:13 ` Jesper Dangaard Brouer [this message]
2019-07-05 12:01 ` Ivan Khoronzhuk
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