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(+)
  

> -----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
  

Hi

> -----Original Message-----
> From: Zhang, Qi Z
> Sent: Sunday, September 30, 2018 10:25
> To: Li, Xiaoyun <xiaoyun.li@intel.com>; Xing, Beilei <beilei.xing@intel.com>;
> dev@dpdk.org; Lu, Wenzhuo <wenzhuo.lu@intel.com>; Wu, Jingjing
> <jingjing.wu@intel.com>
> Subject: RE: [PATCH] doc: add known issue about legacy intr mode for ixgbe
> 
> 
> 
> > -----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"

Sure.

> 
> > +
> > +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/dat
> as
> > heet
> > +s/ethernet-x550-spec-update.pdf>`_
> 
> Seems the url here is not correct, there is no errata item #22
Yes. Will correct it.
Thanks.

> 
> 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