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[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Trusty)
   Importance: Undecided => High

** Changed in: linux (Ubuntu Trusty)
       Status: New => In Progress

** Changed in: linux (Ubuntu Trusty)
     Assignee: (unassigned) => Guilherme G. Piccoli (gpiccoli)

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https://bugs.launchpad.net/bugs/1836760

Title:
  ixgbe{vf} - Physical Function gets IRQ when VF checks link state

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  In Progress
Status in linux source package in Xenial:
  Fix Released
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Won't Fix
Status in linux source package in Disco:
  Fix Released
Status in linux source package in Eoan:
  Fix Released
Status in linux source package in FF-Series:
  Fix Released

Bug description:
  [Impact]

  * Intel NICs that are SR-IOV capable and are managed by ixgbe driver presents a potentially harmful behavior when the ixgbevf-managed VFs (Virtual Functions) perform an ethtool link check. The ixgbevf driver issues a mailbox command in the ethtool link state handler, which induces one IRQ in the PF (Physical Function) per link check.
   
  * This was reported as a sort of "denial-of-service" from a guest; due to some link check loop running inside a guest with PCI-PT of a ixgbevf-managed VF, the host received a huge amount of IRQs causing soft-lockups.
   
  * The patch proposed in this SRU request fix this behavior by relying in the saved link state (obtained in the ixgbevf's watchdog routine) instead of issuing a mailbox command to the PF in every link state check request. The commit is available on Linus tree: 1e1b0c658d9b ("ixgbevf: Use cached link state instead of re-reading the value for ethtool")
  http://git.kernel.org/linus/1e1b0c658d9b

  [Test case]

  Reproducing the behavior is pretty simple; having a machine with an
  Intel NIC managed by ixgbe, proceed with the following steps:

  a) Create one or more VFs
  (echo 1 > /sys/class/net/<PF iface>/device/sriov_numvfs)

  b) In a different terminal, monitor the non-TxRx PF IRQs:
  (watch -n1 "cat /proc/interrupts | grep <PF iface> | grep -v Tx")

  c) Run "ethtool <VF iface>" in a loop

  Without the hereby proposed patch, the PF IRQs will increase.

  [Regression potential]

  The patch scope is restricted to ixgbevf ethtool link-check procedure,
  and was developed by the vendor itself. Being a self-contained patch
  affecting only this driver's ethtool handler, the worst potential
  regression would be a wrong link state report.

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