Re: [PATCH] doc: add known issue about legacy intr mode for ixgbe

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: Li, Xiaoyun
> Sent: Thursday, September 27, 2018 5:17 PM
> To: Xing, Beilei <beilei.xing@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>;
> dev@dpdk.org; Lu, Wenzhuo <wenzhuo.lu@intel.com>; Wu, Jingjing
> <jingjing.wu@intel.com>
> Cc: Li, Xiaoyun <xiaoyun.li@intel.com>
> Subject: [PATCH] doc: add known issue about legacy intr mode for ixgbe
> 
> When using uio_pci_generic module or using legacy interrupt mode of igb_uio
> or vfio, X550 cannot get interrupts. Because the Interrupt Status bit is not
> implemented, then the irq cannot be handled correctly and cannot report the
> event fd to DPDK apps.
> 
> Add this hw limitation and details into ixgbe known issue.
> 
> Signed-off-by: Xiaoyun Li <xiaoyun.li@intel.com>
> ---
>  doc/guides/nics/ixgbe.rst | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/doc/guides/nics/ixgbe.rst b/doc/guides/nics/ixgbe.rst index
> 16d6390..4f89a6d 100644
> --- a/doc/guides/nics/ixgbe.rst
> +++ b/doc/guides/nics/ixgbe.rst
> @@ -200,6 +200,32 @@ There is no RTE API to add a VF's MAC address from
> the PF. On ixgbe, the  ``rte_eth_dev_mac_addr_add()`` function can be used
> to add a VF's MAC address,  as a workaround.
> 
> +legacy interrupt mode and uio pci generic module cannot be used in X550
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~

the reason we can't use uio_pci_generic, is it also because uio_pci_generic require legacy mode?
If it is, can we simplified the title as " x550 does not support legacy interrupt mode"

> +
> +Desccription
> +^^^^^^^^^^^^
> +X550 cannot get interrupts if using ``uio_pci_generic`` module or using
> +legacy interrupt mode of ``igb_uio`` or ``vfio``. Because the errata of
> +X550 states that the Interrupt Status bit is not implemented. The
> +errata is the item #22 from `X550 spec update
> +<https://www.intel.com/content/dam/www/public/us/en/documents/datas
> heet
> +s/ethernet-x550-spec-update.pdf>`_

Seems the url here is not correct, there is no errata item #22

Regards
Qi

> +
> +Implication
> +^^^^^^^^^^^
> +When using ``uio_pci_generic`` module or using legacy interrupt mode of
> +``igb_uio`` or ``vfio``, the Interrupt Status bit would be checked if
> +the interrupt is comming. Since the bit is not implemented in X550, the
> +irq cannot be handled correctly and cannot report the event fd to DPDK
> +apps. Then apps cannot get interrupts and ``dmesg`` will show messages
> +like ``irq #No.: `` ``nobody cared.``
> +
> +Workaround
> +^^^^^^^^^^
> +Do not bind the ``uio_pci_generic`` module in X550 NICs.
> +Do not bind ``igb_uio`` with legacy mode in X550 NICs.
> +Before using ``vfio`` with legacy mode in X550 NICs, using ``modprobe
> +vfio `` ``nointxmask=1`` to bind ``vfio``.
> 
>  Inline crypto processing support
>  --------------------------------
> --
> 2.7.4