From: Ferruh Yigit <ferruh.yigit@intel.com>
To: "Roger B. Melton" <rmelton@cisco.com>, wenzhuo.lu@intel.com
Cc: dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2] net/e1000: correct VLAN tag byte order for i35x LB packets
Date: Wed, 25 Oct 2017 11:11:08 -0700 [thread overview]
Message-ID: <c080b8e0-8ffd-e203-79b3-0ab545461afb@intel.com> (raw)
In-Reply-To: <3b4d34fa-309e-10d4-e992-3d82034e4c41@cisco.com>
On 10/23/2017 10:42 AM, Roger B. Melton wrote:
> On 10/20/17 3:04 PM, Ferruh Yigit wrote:
>> On 10/12/2017 10:24 AM, Roger B Melton wrote:
>>> When copying VLAN tags from the RX descriptor to the vlan_tci field
>>> in the mbuf header, igb_rxtx.c:eth_igb_recv_pkts() and
>>> eth_igb_recv_scattered_pkts() both assume that the VLAN tag is always
>>> little endian. While i350, i354 and /i350vf VLAN non-loopback
>>> packets are stored little endian, VLAN tags in loopback packets for
>>> those devices are big endian.
>>>
>>> For i350, i354 and i350vf VLAN loopback packets, swap the tag when
>>> copying from the RX descriptor to the mbuf header. This will ensure
>>> that the mbuf vlan_tci is always little endian.
>>>
>>> Signed-off-by: Roger B Melton <rmelton@cisco.com>
>> <...>
>>
>>> @@ -946,9 +954,16 @@ eth_igb_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>>>
>>> rxm->hash.rss = rxd.wb.lower.hi_dword.rss;
>>> hlen_type_rss = rte_le_to_cpu_32(rxd.wb.lower.lo_dword.data);
>>> - /* Only valid if PKT_RX_VLAN_PKT set in pkt_flags */
>>> - rxm->vlan_tci = rte_le_to_cpu_16(rxd.wb.upper.vlan);
>>> -
>>> + /*
>>> + * The vlan_tci field is only valid when PKT_RX_VLAN_PKT is
>>> + * set in the pkt_flags field and must be in CPU byte order.
>>> + */
>>> + if ((staterr & rte_cpu_to_le_32(E1000_RXDEXT_STATERR_LB)) &&
>>> + (rxq->flags & IGB_RXQ_FLAG_LB_BSWAP_VLAN)) {
>> This is adding more condition checks into Rx path.
>> What is the performance cost of this addition?
>
> I have not measured the performance cost, but I can collect data. What
> specifically are you looking for?
>
> To be clear the current implementation incorrect as it does not
> normalize the vlan tag to CPU byte order before copying it into mbuf and
> applications have no visibility to determine if the tag in the mbuf is
> big or little endian.
>
> Do you have any suggestions for an alternative approach to avoid rx
> patch checks?
No suggestion indeed. And correctness matters.
But this add a cost and I wonder how much it is, based on that result it may be
possible to do more investigation for alternate solutions or trade-offs.
Konstantin, Bruce, Wenzhuo,
What do you think, do you have any comment?
Thanks,
ferruh
>
> Thanks,
> Roger
>
>
>>
>>> + rxm->vlan_tci = rte_be_to_cpu_16(rxd.wb.upper.vlan);
>>> + } else {
>>> + rxm->vlan_tci = rte_le_to_cpu_16(rxd.wb.upper.vlan);
>>> + }
>>> pkt_flags = rx_desc_hlen_type_rss_to_pkt_flags(rxq, hlen_type_rss);
>>> pkt_flags = pkt_flags | rx_desc_status_to_pkt_flags(staterr);
>>> pkt_flags = pkt_flags | rx_desc_error_to_pkt_flags(staterr);
>> <...>
>> .
>>
>
>
next prev parent reply other threads:[~2017-10-25 18:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 17:24 Roger B Melton
2017-10-16 0:43 ` Lu, Wenzhuo
2017-10-25 21:37 ` Ferruh Yigit
2017-10-20 19:04 ` Ferruh Yigit
2017-10-23 17:42 ` Roger B. Melton
2017-10-25 18:11 ` Ferruh Yigit [this message]
2017-10-25 20:16 ` Bruce Richardson
2017-10-25 20:22 ` Ferruh Yigit
2017-10-25 20:45 ` Roger B. Melton
2017-10-25 20:48 ` Richardson, Bruce
2017-10-25 21:11 ` Ferruh Yigit
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