From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
To: Jesper Dangaard Brouer <brouer@redhat.com>
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
Subject: Re: [PATCH v7 net-next 5/5] net: ethernet: ti: cpsw: add XDP support
Date: Fri, 5 Jul 2019 15:01:16 +0300 [thread overview]
Message-ID: <20190705120114.GA3587@khorivan> (raw)
In-Reply-To: <20190705131354.15a9313c@carbon>
On Fri, Jul 05, 2019 at 01:13:54PM +0200, Jesper Dangaard Brouer wrote:
>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.
My assumption was based on:
struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
{
...
xdp_frame = xdp->data_hard_start;
...
xdp_frame->headroom = headroom - sizeof(*xdp_frame);
...
}
But agree, it doesn't contradict the reason in question.
So, better use proposed variant. Will check and do this in v8 a little later:
dma += xdpf->headroom + sizeof(struct xdp_frame);
>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
--
Regards,
Ivan Khoronzhuk
prev parent reply other threads:[~2019-07-05 12:01 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
2019-07-05 12:01 ` Ivan Khoronzhuk [this message]
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