From: "Lu, Wenzhuo" <wenzhuo.lu@intel.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc
Date: Tue, 31 Oct 2017 01:53:29 +0000 [thread overview]
Message-ID: <6A0DE07E22DDAD4C9103DF62FEBC09093B6DAF73@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <20171025083635.GA13488@bricha3-MOBL3.ger.corp.intel.com>
Hi Bruce,
> -----Original Message-----
> From: Richardson, Bruce
> Sent: Wednesday, October 25, 2017 4:37 PM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc
>
> On Wed, Oct 25, 2017 at 10:54:53AM +0800, Wenzhuo Lu wrote:
> > The description of i40e 16 bytes descriptor is not clear enough. Add
> > more details.
> >
> > Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> > ---
>
> Good idea to document this better.
>
> > doc/guides/nics/i40e.rst | 11 +++++++++--
> > 1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index
> > a0946e6..e0237a8 100644
> > --- a/doc/guides/nics/i40e.rst
> > +++ b/doc/guides/nics/i40e.rst
> > @@ -398,13 +398,20 @@ used to classify MPLS packet by using a command
> in testpmd like:
> > testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
> > 0x8847 fwd queue <M>
> >
> > -16 Byte Descriptor cannot be used on DPDK VF
> > -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +16 Bytes Descriptor setting on DPDK VF
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > +Until 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.
>
> I assume that 2.1.26 is referring to the i40e driver version, not the linux
> kernel version. This should be made clearer, as it also could be read as a very
> old kernel version.
OK, I'll change it to i40e 2.1.26.
>
> > If the Linux i40e kernel driver is used as host driver, while DPDK
> > i40e PMD is used as the VF driver, DPDK cannot choose 16 byte receive
> > descriptor. That is to say, user should keep
> > ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file.
>
> Can you explain - either on-list here, or actually in the docs - why there is
> this restriction? Is it HW or SW? A reference to the section in the datasheet
> for it would also be good. For example Table 8-10 in the datasheet lists no
> restriction on the Dsize bit in the queue context.
It's not a HW limitation. To my opinion, it's SW design and implementation limitation.
I'll add more details.
>
> > +In the future, if the Linux i40e driver supports 16 bytes RX
> > +descriptor, user should make sure the DPDK VF uses the same RX
> > +descriptor mode, 16 bytes or 32 bytes, as the PF driver.
> > +
> > +The same rule for DPDK PF + DPDK VF. The PF and VF should use the
> > +same RX descriptor mode. Or the VF RX will not work.
> >
> > Receive packets with Ethertype 0x88A8
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > --
> > 1.9.3
> >
>
>
> Regards,
> /Bruce
next prev parent reply other threads:[~2017-10-31 1:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-25 2:54 Wenzhuo Lu
2017-10-25 8:36 ` Bruce Richardson
2017-10-31 1:53 ` Lu, Wenzhuo [this message]
2017-10-31 3:40 ` [dpdk-dev] [PATCH v2] " Wenzhuo Lu
2017-10-31 10:04 ` Bruce Richardson
2017-11-01 2:03 ` Lu, Wenzhuo
2017-11-01 2:45 ` [dpdk-dev] [PATCH v3] doc: more clarification for i40e 16 byte desc Wenzhuo Lu
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