mm: introduce ARCH_HAS_PTE_DEVMAP

ARCH_HAS_ZONE_DEVICE is somewhat meaningless in itself, and combined
with the long-out-of-date comment can lead to the impression than an
architecture may just enable it (since __add_pages() now "comprehends
device memory" for itself) and expect things to work.

In practice, however, ZONE_DEVICE users have little chance of
functioning correctly without __HAVE_ARCH_PTE_DEVMAP, so let's clean
that up the same way as ARCH_HAS_PTE_SPECIAL and make it the proper
dependency so the real situation is clearer.

Link: http://lkml.kernel.org/r/87554aa78478a02a63f2c4cf60a847279ae3eb3b.1558547956.git.robin.murphy@arm.com
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 4 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 495d7368ced8..56cec636a1fc 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -649,8 +649,7 @@ config IDLE_PAGE_TRACKING
           See Documentation/admin-guide/mm/idle_page_tracking.rst for
           more details.
 
-# arch_add_memory() comprehends device memory
-config ARCH_HAS_ZONE_DEVICE
+config ARCH_HAS_PTE_DEVMAP
         bool
 
 config ZONE_DEVICE
@@ -658,7 +657,7 @@ config ZONE_DEVICE
         depends on MEMORY_HOTPLUG
         depends on MEMORY_HOTREMOVE
         depends on SPARSEMEM_VMEMMAP
-        depends on ARCH_HAS_ZONE_DEVICE
+        depends on ARCH_HAS_PTE_DEVMAP
         select XARRAY_MULTI
 
         help
diff --git a/mm/gup.c b/mm/gup.c
index 8bbaa5523116..98f13ab37bac 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1895,7 +1895,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 }
 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
-#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
+#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
                 unsigned long end, struct page **pages, int *nr)
 {