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[Tim Gardner <tim.gardner@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Xenial)
   Importance: Medium
       Status: Confirmed

** Changed in: linux (Ubuntu Xenial)
       Status: Confirmed => Fix Committed

** Changed in: linux (Ubuntu Xenial)
     Assignee: (unassigned) => Tim Gardner (timg-tpi)

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https://bugs.launchpad.net/bugs/1552632

Title:
  mlx4_core Set UAR page size to 4KB regardless of system page size

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  problem description:

      The current code sets UAR page size equal to system page size.
      The ConnectX-3 and ConnectX-3 Pro HWs require minimum 128 UAR pages.
      The mlx4 kernel drivers are not loaded if there is less than 128 UAR pages.

      solution:

      Always set UAR page to 4KB. This allows more UAR pages if the OS
      has PAGE_SIZE larger than 4KB. For example, PowerPC kernel use 64KB
      system page size, with 4MB uar region, there are 4MB/2/64KB = 32
      uars (half for uar, half for blueflame). This does not meet minimum 128
      UAR pages requirement. With 4KB UAR page, there are 4MB/2/4KB = 512 uars
      which meet the minimum requirement.

      Note that only codes in mlx4_core that deal with firmware know that uar
      page size is 4KB. Codes that deal with usr page in cq and qp context
      (mlx4_ib, mlx4_en and part of mlx4_core) still have the same assumption
      that uar page size equals to system page size.

      Note that with this implementation, on 64KB system page size kernel, there
      are 16 uars per system page but only one uars is used. The other 15
      uars are ignored because of the above assumption.

      Regarding SR-IOV, mlx4_core in hypervisor will set the uar page size
      to 4KB and mlx4_core code in virtual OS will obtain the uar page size from
      firmware.

      Regarding backward compatibility in SR-IOV, if hypervisor has this new code,
      the virtual OS must be updated. If hypervisor has old code, and the virtual
      OS has this new code, the new code will be backward compatible with the
      old code. If the uar size is big enough, this new code in VF continues to
      work with 64 KB uar page size (on PowerPc kernel). If the uar size does not
      meet 128 uars requirement, this new code not loaded in VF and print the same
      error message as the old code in Hypervisor.

  
  below is the upstream commit id 
  85743f1eb34548ba4b056d2f184a3d107a3b8917

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