x86: add PG_LEVEL enum

this way PG_LEVEL_1GB will be an easy change.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/mm/pageattr-test.c

@@ -16,14 +16,12 @@
 
 enum {
 	NTEST			= 400,
+	LOWEST_LEVEL		= PG_LEVEL_4K,
 #ifdef CONFIG_X86_64
-	LOWEST_LEVEL		= 4,
 	LPS			= (1 << PMD_SHIFT),
 #elif defined(CONFIG_X86_PAE)
-	LOWEST_LEVEL		= 4,
 	LPS			= (1 << PMD_SHIFT),
 #else
-	LOWEST_LEVEL		= 4, /* lookup_address lies here */
 	LPS			= (1 << 22),
 #endif
 	GPS			= (1<<30)

arch/x86/mm/pageattr.c

@@ -28,6 +28,8 @@ pte_t *lookup_address(unsigned long address, int *level)
 	pud_t *pud;
 	pmd_t *pmd;
 
+	*level = PG_LEVEL_NONE;
+
 	if (pgd_none(*pgd))
 		return NULL;
 	pud = pud_offset(pgd, address);
@@ -36,11 +38,12 @@ pte_t *lookup_address(unsigned long address, int *level)
 	pmd = pmd_offset(pud, address);
 	if (pmd_none(*pmd))
 		return NULL;
-	*level = 3;
+
+	*level = PG_LEVEL_2M;
 	if (pmd_large(*pmd))
 		return (pte_t *)pmd;
-	*level = 4;
 
+	*level = PG_LEVEL_4K;
 	return pte_offset_kernel(pmd, address);
 }
 
@@ -145,7 +148,7 @@ __change_page_attr(unsigned long address, struct page *page, pgprot_t prot)
 		address < (unsigned long)&_etext &&
 	       (pgprot_val(prot) & _PAGE_NX));
 
-	if (level == 4) {
+	if (level == PG_LEVEL_4K) {
 		set_pte_atomic(kpte, mk_pte(page, canon_pgprot(prot)));
 	} else {
 		err = split_large_page(kpte, address);

include/asm-x86/pgtable.h

@@ -234,6 +234,12 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 
 #ifndef __ASSEMBLY__
 
+enum {
+	PG_LEVEL_NONE,
+	PG_LEVEL_4K,
+	PG_LEVEL_2M,
+};
+
 /*
  * Helper function that returns the kernel pagetable entry controlling
  * the virtual address 'address'. NULL means no pagetable entry present.