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[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

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

** Tags added: kernel-da-key

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https://bugs.launchpad.net/bugs/1400349

Title:
  [SRU] new arm64 optimized copy_to_user and copy_from_user assembly
  code

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  [Impact]
  The copy_{to,from}_user implementations in the Ubuntu kernel are suboptimal. Optimized implementations have been submitted upstream and have shown a significant improvement in network performance.

  [Test Case]
  Generate traffic from one node to another using iperf.

  [Regression Risk]
  These functions are obviously used heavily throughout the kernel, so a defect here could have significant impact. This risk is mitigated by using an implementation heavily based on the linaro string libraries (which are used in other places already, e.g. glibc), and through active testing of this patch on real hardware using a trusty-kernel base. The new patch will also undergo regression testing to ensure the memory corruption issue of the previous patch does not exist.

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