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[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

The issue manifests itself with any x86 server with their  in-
development PCIe 10GBe LiquidIO NIC.

The card is enabled with a  driver that is currently in active
development.

The issue does not happen in 12.04 LTS nor Centos 7. The  coincidence
there may be that both do not use VFIO but instead the PCI stub driver
to virtualize PCIe NICs.

It seems the issue is related to VFIO, which is the method used  in
14.04 LTS.

The problem manifests itself during card initialization,   specifically,
when setting up the rings.

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https://bugs.launchpad.net/bugs/1563375

Title:
  A a single PCI read or write appears twice on the PCIe bus. This
  happens when using the SR-IOV feature with  Cavium's liquidIO card

Status in linux package in Ubuntu:
  In Progress

Bug description:
  Cavium engineers are testing  SR-IOV feature with  Cavium's new
  liquidIO card (based on OCTEON processor running as an intelligent
  NIC) on x86 Dell servers and ran into the issue described below.

  They are *not* seeing this issue on  Intel 82599 NIC.

  So far, they have seen this on multiple Dell servers - T5810  & Dell
  T630 (x86 - Ubuntu certified).

  We are testing a Cavium OCTEON device in EP mode with SRIOV.  With a CentOS7 VM running on the Ubuntu 14.04.2 host (using VFIO) we see that a single PCI read or write transaction targeting the device’s BAR0 issued from the VM appears twice on the PCIe bus. The same accesses work fine when the VF is accessed directly from the Ubuntu 14.04.2 host. These BAR0 PCI accesses do not require a driver on the VM side. We can reproduce the problem using a simple user-space application to access the VF’s BAR0 registers.
   
  We do not see this problem when the VM runs within a CentOS 7 host or under a Ubuntu 12.04 host. This appears specific to Ubuntu 14.04 release. Appreciate your help in any clues or pointers to this behavior.

  This issue is also not happening with 16.04 beta.

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