Having no more ideas at the moment, here is a tarball of 13 patches of commits touching entry_64.S up to 4.0.0-rc1.
x0001.patch is the latest, x0015.patch is the oldest. Patches 0003 and 0008 are not there since 0003 is empty merge patch and 0008 does some PCI fixup. If this breakage is recent, it ought to be one of these. Most of them do some non-trivial surgery. Even though I did not spot anything suspicious in them, entry.S is notorious for subtle breakage. Try reverting them in sequence starting from x0001.patch and see reverting which one makes crash disappear.
revert_me_13.tar.gz
Description: GNU Zip compressed data
