[PATCH v5 4/7] mm/x86: Make pud_leaf() only care about PSE bit

[Peter Xu <peterx@redhat.com>]

When working on mprotect() on 1G dax entries, I hit an zap bad pud
error when zapping a huge pud that is with PROT_NONE permission.

Here the problem is x86's pud_leaf() requires both PRESENT and PSE bits
set to report a pud entry as a leaf, but that doesn't look right, as
it's not following the pXd_leaf() definition that we stick with so far,
where PROT_NONE entries should be reported as leaves.

To fix it, change x86's pud_leaf() implementation to only check against
PSE bit to report a leaf, irrelevant of whether PRESENT bit is set.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/x86/include/asm/pgtable.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index e39311a89bf4..a2a3bd4c1bda 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1078,8 +1078,7 @@ static inline pmd_t *pud_pgtable(pud_t pud)
 #define pud_leaf pud_leaf
 static inline bool pud_leaf(pud_t pud)
 {
-	return (pud_val(pud) & (_PAGE_PSE | _PAGE_PRESENT)) ==
-		(_PAGE_PSE | _PAGE_PRESENT);
+	return pud_val(pud) & _PAGE_PSE;
 }
 
 static inline int pud_bad(pud_t pud)
-- 
2.45.0