powerpc/mm: move setting pte specific flags to pfn_pte

powerpc used to set the pte specific flags in set_pte_at().  This is
different from other architectures.  To be consistent with other
architecture update pfn_pte to set _PAGE_PTE on ppc64.  Also, drop now
unused pte_mkpte.

We add a VM_WARN_ON() to catch the usage of calling set_pte_at() without
setting _PAGE_PTE bit.  We will remove that after a few releases.

With respect to huge pmd entries, pmd_mkhuge() takes care of adding the
_PAGE_PTE bit.

[akpm@linux-foundation.org: whitespace fix, per Christophe]
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lkml.kernel.org/r/20200902114222.181353-3-aneesh.kumar@linux.ibm.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -615,7 +615,7 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t pgprot)
 	VM_BUG_ON(pfn >> (64 - PAGE_SHIFT));
 	VM_BUG_ON((pfn << PAGE_SHIFT) & ~PTE_RPN_MASK);
 
-	return __pte(((pte_basic_t)pfn << PAGE_SHIFT) | pgprot_val(pgprot));
+	return __pte(((pte_basic_t)pfn << PAGE_SHIFT) | pgprot_val(pgprot) | _PAGE_PTE);
 }
 
 static inline unsigned long pte_pfn(pte_t pte)
@@ -651,11 +651,6 @@ static inline pte_t pte_mkexec(pte_t pte)
 	return __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_EXEC));
 }
 
-static inline pte_t pte_mkpte(pte_t pte)
-{
-	return __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PTE));
-}
-
 static inline pte_t pte_mkwrite(pte_t pte)
 {
 	/*
@@ -819,6 +814,14 @@ static inline int pte_none(pte_t pte)
 static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, int percpu)
 {
+
+	VM_WARN_ON(!(pte_raw(pte) & cpu_to_be64(_PAGE_PTE)));
+	/*
+	 * Keep the _PAGE_PTE added till we are sure we handle _PAGE_PTE
+	 * in all the callers.
+	 */
+	pte = __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PTE));
+
 	if (radix_enabled())
 		return radix__set_pte_at(mm, addr, ptep, pte, percpu);
 	return hash__set_pte_at(mm, addr, ptep, pte, percpu);

arch/powerpc/include/asm/nohash/pgtable.h

@@ -140,11 +140,6 @@ static inline pte_t pte_mkold(pte_t pte)
 	return __pte(pte_val(pte) & ~_PAGE_ACCESSED);
 }
 
-static inline pte_t pte_mkpte(pte_t pte)
-{
-	return pte;
-}
-
 static inline pte_t pte_mkspecial(pte_t pte)
 {
 	return __pte(pte_val(pte) | _PAGE_SPECIAL);

arch/powerpc/mm/pgtable.c

@@ -184,9 +184,6 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 	 */
 	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
 
-	/* Add the pte bit when trying to set a pte */
-	pte = pte_mkpte(pte);
-
 	/* Note: mm->context.id might not yet have been assigned as
 	 * this context might not have been activated yet when this
 	 * is called.
@@ -275,8 +272,6 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_
 	 */
 	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
 
-	pte = pte_mkpte(pte);
-
 	pte = set_pte_filter(pte);
 
 	val = pte_val(pte);