powerpc/mm: Add a _PAGE_PTE bit

For a pte entry we will have _PAGE_PTE set. Our pte page
address have a minimum alignment requirement of HUGEPD_SHIFT_MASK + 1.
We use the lower 7 bits to indicate hugepd. ie.

For pmd and pgd we can find:
1) _PAGE_PTE set pte -> indicate PTE
2) bits [2..6] non zero -> indicate hugepd.
   They also encode the size. We skip bit 1 (_PAGE_PRESENT).
3) othewise pointer to next table.

Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

3 files changed, 7 insertions, 8 deletions

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index bc72e542a83e..61b8b7ccea4f 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -894,8 +894,8 @@ void flush_dcache_icache_hugepage(struct page *page)
  * We have 4 cases for pgds and pmds:
  * (1) invalid (all zeroes)
  * (2) pointer to next table, as normal; bottom 6 bits == 0
- * (3) leaf pte for huge page, bottom two bits != 00
- * (4) hugepd pointer, bottom two bits == 00, next 4 bits indicate size of table
+ * (3) leaf pte for huge page _PAGE_PTE set
+ * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table
  *
  * So long as we atomically load page table pointers we are safe against teardown,
  * we can follow the address down to the the page and take a ref on it.
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 83dfcb55ffef..83dfd7925c72 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -179,6 +179,10 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 	 */
 	VM_WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) ==
 		(_PAGE_PRESENT | _PAGE_USER));
+	/*
+	 * Add the pte bit when tryint set a pte
+	 */
+	pte = __pte(pte_val(pte) | _PAGE_PTE);
 
 	/* Note: mm->context.id might not yet have been assigned as
 	 * this context might not have been activated yet when this
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index d42dd289abfe..ea6bc31debb0 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -765,13 +765,8 @@ static pmd_t pmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
 pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
 {
 	unsigned long pmdv;
-	/*
-	 * For a valid pte, we would have _PAGE_PRESENT always
-	 * set. We use this to check THP page at pmd level.
-	 * leaf pte for huge page, bottom two bits != 00
-	 */
+
 	pmdv = pfn << PTE_RPN_SHIFT;
-	pmdv |= _PAGE_THP_HUGE;
 	return pmd_set_protbits(__pmd(pmdv), pgprot);
 }