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Message-ID: <PH0PR11MB583042FF9988C2B445B7B06FD89B9@PH0PR11MB5830.namprd11.prod.outlook.com>
Date: Wed, 12 Apr 2023 01:31:19 +0000
From: "Song, Yoong Siang" <yoong.siang.song@...el.com>
To: Stanislav Fomichev <sdf@...gle.com>
CC: Giuseppe Cavallaro <peppe.cavallaro@...com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Jose Abreu <joabreu@...opsys.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
"Jakub Kicinski" <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
"Daniel Borkmann" <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Alexander Duyck <alexanderduyck@...com>,
"Ong, Boon Leong" <boon.leong.ong@...el.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-stm32@...md-mailman.stormreply.com"
<linux-stm32@...md-mailman.stormreply.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"xdp-hints@...-project.net" <xdp-hints@...-project.net>
Subject: RE: [PATCH net-next 3/4] net: stmmac: add Rx HWTS metadata to XDP
receive pkt
On Tuesday, April 11, 2023 12:25 AM, Stanislav Fomichev <sdf@...gle.com> wrote:
>On 04/10, Song Yoong Siang wrote:
>> Add receive hardware timestamp metadata support via kfunc to XDP
>> receive packets.
>>
>> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
>> ---
>> drivers/net/ethernet/stmicro/stmmac/stmmac.h | 1 +
>> .../net/ethernet/stmicro/stmmac/stmmac_main.c | 24 +++++++++++++++++--
>> 2 files changed, 23 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> index ac8ccf851708..760445275da8 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> @@ -94,6 +94,7 @@ struct stmmac_rx_buffer {
>>
>> struct stmmac_xdp_buff {
>> struct xdp_buff xdp;
>> + ktime_t rx_hwts;
>> };
>>
>> struct stmmac_rx_queue {
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index f7bbdf04d20c..ca183fbfde85 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -5307,6 +5307,8 @@ static int stmmac_rx(struct stmmac_priv *priv, int
>limit, u32 queue)
>> }
>> }
>>
>
>[..]
>
>> + stmmac_get_rx_hwtstamp(priv, p, np, &ctx.rx_hwts);
>
>Do we want to pay this cost for every packet?
>
>The preferred alternative is to store enough state in the stmmac_xdp_buff so we
>can get to this data from stmmac_xdp_rx_timestamp.
>
>I haven't read this code, but tentatively:
>- move priv, p, np into stmmac_xdp_buff, assign them here instead of
> calling stmmac_get_rx_hwtstamp
>- call stmmac_get_rx_hwtstamp from stmmac_xdp_rx_timestamp with the
> stored priv, p, np
>
>That would ensure that we won't waste the cycles pulling out the rx timestamp
>for every packet if the higher levels / users don't care.
>
>Would something like this work?
Hi Stanislav Fomichev,
Thanks for your comments.
Original stmmac_rx() function is already calling stmmac_get_rx_hwtstamp() for
every packet. This patch move the calling of stmmac_get_rx_hwtstamp() earlier
so that rx timestamp is available before running bpf_prog_run_xdp(). So, i
think no additional cost introduced here. Any other thoughts?
Furthermore, stmmac_get_rx_hwtstamp() will check whether hw timestamp is
enabled in driver and available in the descriptor before getting the hw timestamp.
>
>> +
>> if (!skb) {
>> unsigned int pre_len, sync_len;
>>
>> @@ -5315,7 +5317,7 @@ static int stmmac_rx(struct stmmac_priv *priv,
>> int limit, u32 queue)
>>
>> xdp_init_buff(&ctx.xdp, buf_sz, &rx_q->xdp_rxq);
>> xdp_prepare_buff(&ctx.xdp, page_address(buf->page),
>> - buf->page_offset, buf1_len, false);
>> + buf->page_offset, buf1_len, true);
>>
>> pre_len = ctx.xdp.data_end - ctx.xdp.data_hard_start -
>> buf->page_offset;
>> @@ -5411,7 +5413,7 @@ static int stmmac_rx(struct stmmac_priv *priv,
>> int limit, u32 queue)
>>
>> shhwtstamp = skb_hwtstamps(skb);
>> memset(shhwtstamp, 0, sizeof(struct skb_shared_hwtstamps));
>> - stmmac_get_rx_hwtstamp(priv, p, np, &shhwtstamp->hwtstamp);
Original stmmac_get_rx_hwtstamp() function is called here.
Thanks & Regards
Siang
>> + shhwtstamp->hwtstamp = ctx.rx_hwts;
>>
>> stmmac_rx_vlan(priv->dev, skb);
>> skb->protocol = eth_type_trans(skb, priv->dev); @@ -7071,6
>+7073,22
>> @@ void stmmac_fpe_handshake(struct stmmac_priv *priv, bool enable)
>> }
>> }
>>
>> +static int stmmac_xdp_rx_timestamp(const struct xdp_md *_ctx, u64
>> +*timestamp) {
>> + const struct stmmac_xdp_buff *ctx = (void *)_ctx;
>> +
>> + if (ctx->rx_hwts) {
>> + *timestamp = ctx->rx_hwts;
>> + return 0;
>> + }
>> +
>> + return -ENODATA;
>> +}
>> +
>> +const struct xdp_metadata_ops stmmac_xdp_metadata_ops = {
>> + .xmo_rx_timestamp = stmmac_xdp_rx_timestamp,
>> +};
>> +
>> /**
>> * stmmac_dvr_probe
>> * @device: device pointer
>> @@ -7178,6 +7196,8 @@ int stmmac_dvr_probe(struct device *device,
>>
>> ndev->netdev_ops = &stmmac_netdev_ops;
>>
>> + ndev->xdp_metadata_ops = &stmmac_xdp_metadata_ops;
>> +
>> ndev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM |
>NETIF_F_IPV6_CSUM |
>> NETIF_F_RXCSUM;
>> ndev->xdp_features = NETDEV_XDP_ACT_BASIC |
>NETDEV_XDP_ACT_REDIRECT
>> |
>> --
>> 2.34.1
>>
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