[PATCH v3 4/9] mm: convert PTE table entries in ptep_get()

[Muhammad Usama Anjum <usama.anjum@arm.com>]

ptep_get() now accepts a pointer to hw_pte_t storage but must continue to
return a software PTE value. Add __pte_from_hw for both generic hw_pte_t
definitions. Read the hw_pte_t table element atomically before converting
it to pte_t.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
---
Changes since v1:
- Use software PTE value terminology.

Changes since RFC v1:
- Define __pte_from_hw for the opted-in generic wrapper.
- Apply READ_ONCE() to hw_pte_t before converting it to pte_t.
---
 include/linux/pgtable.h       | 2 +-
 include/linux/pgtable_types.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 19098e302b75a..41337da0d65aa 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -493,7 +493,7 @@ static inline int pudp_set_access_flags(struct vm_area_struct *vma,
 #ifndef ptep_get
 static inline pte_t ptep_get(hw_pte_t *ptep)
 {
-	return READ_ONCE(*ptep);
+	return __pte_from_hw(READ_ONCE(*ptep));
 }
 #endif
 
diff --git a/include/linux/pgtable_types.h b/include/linux/pgtable_types.h
index 07da05d375c2c..d6c5a7548550b 100644
--- a/include/linux/pgtable_types.h
+++ b/include/linux/pgtable_types.h
@@ -8,8 +8,10 @@
 
 #ifdef CONFIG_ARCH_HAS_HW_PTE_T
 typedef struct __hw_pte_t { pte_t __pte; } hw_pte_t;
+#define __pte_from_hw(pte)	((pte).__pte)
 #else
 #define hw_pte_t pte_t
+#define __pte_from_hw(pte)	(pte)
 #endif
 
 #endif /* !__ASSEMBLY__ */

-- 
2.47.3