Description of problem:
Hi,
  There's a KVM+THP corruption in 4.5 (and current 4.6) kernels that i've triggered on Fedora while testing the QEMU Postcopy feature.  There's a chance it might trigger with the use of the more common Balloon feature as well, so it's probably worth fixing since the symptom is a random guest memory corruption

Fixed by Andrea Arcangeli's patch:
[PATCH 1/1] mm: thp: kvm: fix memory corruption in KVM with THP enabled
  currently being discussed on lkml/linux-mm/qemu-devel

Version-Release number of selected component (if applicable):
4.5, 4.6 kernels

How reproducible:
ah well, that's rather complicated;  I can reproduce it 100% in a nest, and about 1/1000 runs of my test suite on a real host.  It disappears if you turn THP off or include the patch noted.

Steps to Reproduce:
I've seen reports that migrating a busy guest using postcopy will hang on 4.5;
but I'm about to post tests/postcopy-test for qemu.  I run it repeatedly and it fails the first time on a VM but randomly on hardware.

Actual results:
A migrated VM whose contents aren't quite the same as the source.

Expected results:
A nice happy migrated VM

Additional info: