[PATCH mm-unstable RFC v4 3/7] powerpc/mm: use PTE-level pgprot for huge PFN helpers

[Yin Tirui]

Make the powerpc PMD PFN helper use PTE-level pgprot_t as the basic
format.

pmd_pgprot() currently derives pgprot_t from the PMD entry through
pte_pgprot(). Some PMD leaf entries can carry H_PAGE_THP_HUGE, which is
specific to huge PMDs and should not be propagated into PTE-level
pgprot_t.

Mask H_PAGE_THP_HUGE out in pmd_pgprot().

Signed-off-by: Yin Tirui <yintirui@xxxxxxxxxx>
---
 arch/powerpc/include/asm/pgtable.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index d20ff2ae02f5..0f368ea64b1f 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -67,7 +67,16 @@ static inline pgprot_t pte_pgprot(pte_t pte)
 #define pmd_pgprot pmd_pgprot
 static inline pgprot_t pmd_pgprot(pmd_t pmd)
 {
-	return pte_pgprot(pmd_pte(pmd));
+	pgprot_t prot = pte_pgprot(pmd_pte(pmd));
+
+	/*
+	 * pmd_pgprot() returns PTE-level pgprot_t. H_PAGE_THP_HUGE is specific
+	 * to huge PMDs.
+	 */
+#ifdef H_PAGE_THP_HUGE
+	prot = __pgprot(pgprot_val(prot) & ~H_PAGE_THP_HUGE);
+#endif
+	return prot;
 }
 
 #define pud_pgprot pud_pgprot
-- 
2.43.0