[PATCH V2] arm64: optimized copy_to_user and copy_from_user assembly code

On 3 December 2014 at 20:01, Craig Magina [off-list ref] wrote:
[...]

Could you provide the steps you used to reproduce this issue? I have
already submitted an SRU to revert this patch, but would like to have
the method you used to reproduce it for testing. Thanks for reporting
this.

--
Craig Magina

Hi Craig,
It's not easy to reproduce as the problem occurs when the kernel is
copying memory to userspace and experiences a page fault.

I have come across it whilst running "perf record -a" on a system that
is swapping.

Also, building source code under memory pressure (i.e. kernel compile
just after the system has swapped out pages), gave me this problem
too.

Cheers,
--
Steve