Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP checksum definition

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Mon, 8 Oct 2018 13:13:31 +0100
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> CC: Thomas Monjalon <thomas@monjalon.net>, "Ananyev, Konstantin"
>  <konstantin.ananyev@intel.com>, Andrew Rybchenko
>  <arybchenko@solarflare.com>, "Lu, Wenzhuo" <wenzhuo.lu@intel.com>, "Wu,
>  Jingjing" <jingjing.wu@intel.com>, "Iremonger, Bernard"
>  <bernard.iremonger@intel.com>, "Mcnamara, John" <john.mcnamara@intel.com>,
>  "Kovacevic, Marko" <marko.kovacevic@intel.com>, Olivier Matz
>  <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>,
>  "shahafs@mellanox.com" <shahafs@mellanox.com>, "didier.pallard@6wind.com"
>  <didier.pallard@6wind.com>
> Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
>  checksum definition
> User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
>  Thunderbird/52.9.1
> 
> On 10/8/2018 12:55 PM, Jerin Jacob wrote:
> > -----Original Message-----
> >> Date: Mon, 8 Oct 2018 11:53:01 +0100
> >> From: Ferruh Yigit <ferruh.yigit@intel.com>
> >> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, Thomas Monjalon
> >>  <thomas@monjalon.net>
> >> CC: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>, Andrew Rybchenko
> >>  <arybchenko@solarflare.com>, "Lu, Wenzhuo" <wenzhuo.lu@intel.com>, "Wu,
> >>  Jingjing" <jingjing.wu@intel.com>, "Iremonger, Bernard"
> >>  <bernard.iremonger@intel.com>, "Mcnamara, John" <john.mcnamara@intel.com>,
> >>  "Kovacevic, Marko" <marko.kovacevic@intel.com>, Olivier Matz
> >>  <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>,
> >>  "shahafs@mellanox.com" <shahafs@mellanox.com>, "didier.pallard@6wind.com"
> >>  <didier.pallard@6wind.com>
> >> Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
> >>  checksum definition
> >> User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
> >>  Thunderbird/52.9.1
> >>
> >> On 10/8/2018 10:37 AM, Jerin Jacob wrote:
> >>> -----Original Message-----
> >>>> Date: Mon, 08 Oct 2018 11:04:51 +0200
> >>>> From: Thomas Monjalon <thomas@monjalon.net>
> >>>> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, Ferruh Yigit
> >>>>  <ferruh.yigit@intel.com>, "Ananyev, Konstantin"
> >>>>  <konstantin.ananyev@intel.com>
> >>>> Cc: Andrew Rybchenko <arybchenko@solarflare.com>, "Lu, Wenzhuo"
> >>>>  <wenzhuo.lu@intel.com>, "Wu, Jingjing" <jingjing.wu@intel.com>,
> >>>>  "Iremonger, Bernard" <bernard.iremonger@intel.com>, "Mcnamara, John"
> >>>>  <john.mcnamara@intel.com>, "Kovacevic, Marko" <marko.kovacevic@intel.com>,
> >>>>  Olivier Matz <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>,
> >>>>  "shahafs@mellanox.com" <shahafs@mellanox.com>, "didier.pallard@6wind.com"
> >>>>  <didier.pallard@6wind.com>
> >>>> Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
> >>>>  checksum definition
> >>>>
> >>>> 08/10/2018 10:24, Jerin Jacob:
> >>>>> From: Ferruh Yigit <ferruh.yigit@intel.com>
> >>>>>> On 10/6/2018 1:18 PM, Ananyev, Konstantin wrote:
> >>>>>>> From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
> >>>>>>>> From: Thomas Monjalon <thomas@monjalon.net>
> >>>>>>>>> However, we should re-visit the flag PKT_RX_EIP_CKSUM_BAD.
> >>>>>>>>
> >>>>>>>> Do we need to block this patch due to the exiting PKT_RX_EIP_CKSUM_BAD
> >>>>>>>> definition?
> >>>>>>>>
> >>>>>>>> I already added the author of the PKT_RX_EIP_CKSUM_BAD flag and ethdev and mbuf
> >>>>>>>> maintainers in this list. So what else I need make forward progress
> >>>>>>>> on this patch?
> >>>>>>>>
> >>>>>>>> I think, the definition of PKT_RX_EIP_CKSUM_BAD based on HW capability. It
> >>>>>>>> is safe to assume that ALL HW can support CKSUM BAD if the feature is
> >>>>>>>> available and hence it is more portable.
> >>>>>>>
> >>>>>>> Yes, as I remember PKT_RX_EIP_CKSUM_BAD is based on DEV_RX_OFFLOAD_OUTER_IPV4_CKSUM.
> >>>>>>
> >>>>>> Switching to two bit won't reduce the portability, HW supports only reporting
> >>>>>> CKSUM_BAD can set BAD || UNKNOWN.
> >>>>>
> >>>>> UNKNOWN is not a bit. It is represented as 0. It spec has 2 bit, then
> >>>>> driver need to report GOOD as well.
> >>>>>
> >>>>> Same applies for PKT_RX_EL4_CKSUM as well.
> >>>>>
> >>>>>>
> >>>>>> And I think patch is not blocked by PKT_RX_EIP_CKSUM_BAD, it can be changed
> >>>>>> separately, for this patch question is can we represent PKT_RX_EL4_CKSUM_* with
> >>>>>> two bits, to have BAD/GOOD/UNKNOWN?
> >>>>
> >>>> Yes, exact.
> >>>>
> >>>> PKT_RX_EIP_CKSUM_BAD must be left aside.
> >>>> We should just avoid taking it as a reference.
> >>>> And we can reconsider its definition later.
> >>>
> >>> OK.
> >>>
> >>> IMO, Using 2 bit scheme for tunneled checksum has following performance
> >>> issue from driver side.
> >>>
> >>> Driver need to mark the packet as GOOD. All the HW can support
> >>> detection of BAD. That not necessary mean GOOD in case of tunnel packet,
> >>> so driver has to detect the packet is tunneled and packet is not BAD
> >>> then mark GOOD.
> >>
> >> Yes UNKNOWN is not a bit, but a state, why don't use it? Why driver has to check
> >> it is GOOD?
> >
> > The application is going to check is it GOOD or not. Not the driver,
> > Right? My concern was, If application starts dropping the packet instead checking the BAD, if
> > it checks == !GOOD.
> 
> Got it, but when 2 bits state introduced, app should check if check == BAD for
> drop decision, because it is not GOOD || BAD anymore.

Got it.

> 
> >
> >>
> >> 0x0 => UNKNOWN
> >> 0x1 => BAD
> >> 0x2 => GOOD
> >> 0x3 => ? (invalid perhaps)
> >>
> >> HW that supports detecting good packets can set BAD || GOOD state, HW can detect
> >> only BAD packet can set BAD || UNKNOWN state.
> >>
> >> If BAD is not set, there is an ambiguity of state, lets clarify it in lower
> >> level, if it is UNKNOWN, let application know it is UNKNOWN.
> >
> > OK.
> >
> > How about the following then?
> >
> > /**
> >  * Mask of bits used to determine the status of outer RX L4 checksum.
> >  * - PKT_RX_EL4_CKSUM_UNKNOWN: no information about the outer RX L4 checksum
> >  * - PKT_RX_EL4_CKSUM_BAD: the outer L4 checksum in the packet is wrong
> >  * - PKT_RX_EL4_CKSUM_GOOD: the outer L4 checksum in the packet is valid
> >  * - PKT_RX_EL4_CKSUM_INVALID: invalid outer L4 checksum state.
> >  *
> >  * The detection of PKT_RX_EL4_CKSUM_GOOD shall be based on the given
> >  * HW capability, At minimum, the PMD should support
> >  * PKT_RX_EL4_CKSUM_UNKNOWN  and PKT_RX_EL4_CKSUM_BAD states
> >  * if the offload is available.
> >  */
> > #define PKT_RX_EL4_CKSUM_MASK   ((1ULL << 21) | (1ULL << 22))
> >
> > #define PKT_RX_IP_CKSUM_UNKNOWN 0
> > #define PKT_RX_IP_CKSUM_BAD     (1ULL << 21)
> > #define PKT_RX_IP_CKSUM_GOOD    (1ULL << 22)
> > #define PKT_RX_IP_CKSUM_INVALID ((1ULL << 21) | (1ULL << 22))
> 
> Looks good to me.

If there is no objection with above flag definition, I will send the v3 with that.

> 
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