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

["Li, Xiaoyun" <xiaoyun.li@intel.com>]

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