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...@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. > 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. > +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
