From: Wenzhuo Lu Date: Wed, 1 Nov 2017 02:45:28 +0000 (+0800) Subject: doc: add clarification for i40e 16 byte desc X-Git-Tag: spdx-start~963 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=8c22b59a173f1b53fe522ba4182947dd3ebb4d42;p=dpdk.git doc: add clarification for i40e 16 byte desc The description of i40e 16 byte descriptor is not clear enough. Add more details. Signed-off-by: Wenzhuo Lu Acked-by: Bruce Richardson --- diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index a0946e6d5d..05c1875bcb 100644 --- a/doc/guides/nics/i40e.rst +++ b/doc/guides/nics/i40e.rst @@ -398,13 +398,24 @@ 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 -16 Byte Descriptor cannot be used on DPDK VF -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +16 Byte RX Descriptor setting on DPDK VF +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -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. +Currently the VF's RX descriptor mode is decided by PF. There's no PF-VF +interface for VF to request the RX descriptor mode, also no interface to notify +VF its own RX descriptor mode. +For all available versions of the i40e driver, these drivers don't support 16 +byte RX descriptor. 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. The reason is that the RX descriptor is already set to 32 byte by +the i40e kernel driver. That is to say, user should keep +``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file. +In the future, if the Linux i40e driver supports 16 byte RX descriptor, user +should make sure the DPDK VF uses the same RX descriptor mode, 16 byte or 32 +byte, 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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~