KVM guests freeze under upstream kernel

[joserz at linux.vnet.ibm.com]

Hello!

We're not able to boot any KVM guest using upstream kernel (cb8c65ccff7f77d0285f1b126c72d37b2572c865 - 4.13.0-rc1+).
After reaching the SLOF initial counting, the guest simply freezes:

SLOF
**********************************************************************
QEMU Starting
 Build Date = Mar  3 2017 13:29:19
  FW Version = git-66d250ef0fd06bb8
   Press "s" to enter Open Firmware.

   C0360

After bisecting I found the commit:

https://github.com/torvalds/linux/commit/ebd3119

    powerpc/mm: Add devmap support for ppc64

    Add support for the devmap bit on PTEs and PMDs for PPC64 Book3S.  This
    is used to differentiate device backed memory from transparent huge
    pages since they are handled in more or less the same manner by the core
    mm code.

Reverting the commit and rebuilding 4.13.0-rc1+ was enough to make a workaround.
But I'll need some help from you guys in order to solve it.

Thanks!

Jose Ziviani