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.

Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/powerpc/mm/pgtable-hash64.c b/arch/powerpc/mm/pgtable-hash64.c
index 16877f60fb87..a0facee58811 100644
--- a/arch/powerpc/mm/pgtable-hash64.c
+++ b/arch/powerpc/mm/pgtable-hash64.c
@@ -184,7 +184,7 @@ unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr
         unsigned long old;
 
 #ifdef CONFIG_DEBUG_VM
-        WARN_ON(!pmd_trans_huge(*pmdp));
+        WARN_ON(!hash__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
         assert_spin_locked(&mm->page_table_lock);
 #endif
 
@@ -216,6 +216,7 @@ pmd_t hash__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long addres
 
         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
         VM_BUG_ON(pmd_trans_huge(*pmdp));
+        VM_BUG_ON(pmd_devmap(*pmdp));
 
         pmd = *pmdp;
         pmd_clear(pmdp);
@@ -296,6 +297,7 @@ void hash__pmdp_huge_split_prepare(struct vm_area_struct *vma,
 {
         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
         VM_BUG_ON(REGION_ID(address) != USER_REGION_ID);
+        VM_BUG_ON(pmd_devmap(*pmdp));
 
         /*
          * We can't mark the pmd none here, because that will cause a race