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From: Tiwei Bie <tiwei.bie@intel.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>,
	Zhihong Wang <zhihong.wang@intel.com>,
	dev@dpdk.org, Dilshod Urazov <Dilshod.Urazov@oktetlabs.ru>,
	stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] net/virtio: add Tx preparation
Date: Wed, 5 Jun 2019 17:37:29 +0800
Message-ID: <20190605093729.GA16974@___> (raw)
In-Reply-To: <8fb39bf5-2bd2-7faa-9ab7-551e234d77c5@solarflare.com>

On Wed, Jun 05, 2019 at 10:28:14AM +0300, Andrew Rybchenko wrote:
> Hi,
> 
> On 6/5/19 4:41 AM, Tiwei Bie wrote:
> 
>     Hi,
> 
>     Thanks for the patch!
> 
> 
> More will follow. At least Tx checksum offload is broken when used together
> with VLAN insertion since the later prepend to mbuf, but do nothing with
> l2_len/outer_l2_len. We'll send a patch to move rte_vlan_insert()
> to Tx prepare and suggest separate patch to update l2_len or outer_l2_len
> when software VLAN insertion is done.
> 

Thanks :)

> 
>     On Mon, Jun 03, 2019 at 07:50:05PM +0100, Andrew Rybchenko wrote:
>     [...]
> 
>          uint16_t
>         +virtio_xmit_pkts_prepare(void *tx_queue __rte_unused, struct rte_mbuf **tx_pkts,
>         +                       uint16_t nb_pkts)
>         +{
>         +       uint16_t nb_tx;
>         +       int error;
>         +
>         +       for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
>         +               struct rte_mbuf *m = tx_pkts[nb_tx];
>         +
>         +#ifdef RTE_LIBRTE_ETHDEV_DEBUG
>         +               error = rte_validate_tx_offload(m);
>         +               if (unlikely(error)) {
>         +                       rte_errno = -error;
>         +                       break;
>         +               }
>         +#endif
>         +
>         +               error = rte_net_intel_cksum_prepare(m);
>         +               if (unlikely(error)) {
>         +                       rte_errno = -error;
> 
>     It's a bit confusing here.
>     Based on the API doc of rte_eth_tx_prepare():
> 
>     https://github.com/DPDK/dpdk/blob/7f9f46d6cef5b03681a3935b9a18378e08ca6f62/lib/librte_ethdev/rte_ethdev.h#L4360-L4362
> 
>     It should set negative value to rte_errno when error happens,
> 
> 
> I'm pretty sure that it is a bug in documentation. rte_errno must be positive.

Yeah. Negative rte_errno looks confusing.

> I'll send a patch to fix it.
> Even the code just below sets positive rte_errno. Simple cases are very easy to
> find:
> $ git grep 'rte_errno = E' | wc -l
> 557
> $ git grep 'rte_errno = -E' | wc -l
> 50
> 
> A bit more complex cases which require careful review:
> $ git grep -e 'rte_errno = -[a-z]' | wc -l                                     
> 37
> $ git grep -e 'rte_errno = [a-z]' | wc -l
> 150
> 
> Cases which look right from the first sight overweight wrong 3 times.
> But it is still too many cases which are potentially wrong.
> 
> Andrew.

Thanks,
Tiwei

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-03 18:50 Andrew Rybchenko
2019-06-05  1:41 ` Tiwei Bie
2019-06-05  7:28   ` Andrew Rybchenko
2019-06-05  9:37     ` Tiwei Bie [this message]
2019-06-16 10:17 ` [dpdk-dev] [PATCH v3 1/2] " Andrew Rybchenko
2019-06-16 10:17   ` [dpdk-dev] [PATCH v3 2/2] net/virtio: move VLAN tag insertion to Tx prepare Andrew Rybchenko
2019-06-17  8:54     ` Tiwei Bie
2019-06-17 11:35       ` Andrew Rybchenko
2019-06-17  8:52   ` [dpdk-dev] [PATCH v3 1/2] net/virtio: add Tx preparation Tiwei Bie
2019-06-17 11:31 ` [dpdk-dev] [PATCH v4 " Andrew Rybchenko
2019-06-17 11:31   ` [dpdk-dev] [PATCH v4 2/2] net/virtio: move VLAN tag insertion to Tx prepare Andrew Rybchenko
2019-06-18  4:42     ` Tiwei Bie
2019-06-20  9:58     ` Maxime Coquelin
2019-06-20  9:58   ` [dpdk-dev] [PATCH v4 1/2] net/virtio: add Tx preparation Maxime Coquelin

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