commit 73b20c84d42de14673a987816dd4d132c7b1f801 upstream.

In order for things like get_user_pages() to work on ZONE_DEVICE memory,
we need a software PTE bit to identify device-backed PFNs.  Hook this up
along with the relevant helpers to join in with ARCH_HAS_PTE_DEVMAP.

[robin.murphy@arm.com: build fixes]
  Link: http://lkml.kernel.org/r/13026c4e64abc17133bbfa07d7731ec6691c0bcd.1559050949.git.robin.murphy@arm.com
Link: http://lkml.kernel.org/r/817d92886fc3b33bcbf6e105ee83a74babb3a5aa.1558547956.git.robin.murphy@arm.comSigned-off-by: NRobin Murphy <robin.murphy@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NShannon Zhao <shannon.zhao@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>