x86/mm: Convert trivial cases of page table walk to 5-level paging

This patch only covers simple cases. Less trivial cases will be
converted with separate patches.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170313143309.16020-3-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 2b4b53e..5ed3c14 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -67,6 +67,7 @@
  */
 static pmd_t * __init one_md_table_init(pgd_t *pgd)
 {
+	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd_table;
 
@@ -75,13 +76,15 @@
 		pmd_table = (pmd_t *)alloc_low_page();
 		paravirt_alloc_pmd(&init_mm, __pa(pmd_table) >> PAGE_SHIFT);
 		set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
-		pud = pud_offset(pgd, 0);
+		p4d = p4d_offset(pgd, 0);
+		pud = pud_offset(p4d, 0);
 		BUG_ON(pmd_table != pmd_offset(pud, 0));
 
 		return pmd_table;
 	}
 #endif
-	pud = pud_offset(pgd, 0);
+	p4d = p4d_offset(pgd, 0);
+	pud = pud_offset(p4d, 0);
 	pmd_table = pmd_offset(pud, 0);
 
 	return pmd_table;
@@ -390,8 +393,11 @@
 
 static inline pte_t *kmap_get_fixmap_pte(unsigned long vaddr)
 {
-	return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
-			vaddr), vaddr), vaddr);
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	p4d_t *p4d = p4d_offset(pgd, vaddr);
+	pud_t *pud = pud_offset(p4d, vaddr);
+	pmd_t *pmd = pmd_offset(pud, vaddr);
+	return pte_offset_kernel(pmd, vaddr);
 }
 
 static void __init kmap_init(void)
@@ -410,6 +416,7 @@
 {
 	unsigned long vaddr;
 	pgd_t *pgd;
+	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
@@ -418,7 +425,8 @@
 	page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);
 
 	pgd = swapper_pg_dir + pgd_index(vaddr);
-	pud = pud_offset(pgd, vaddr);
+	p4d = p4d_offset(pgd, vaddr);
+	pud = pud_offset(p4d, vaddr);
 	pmd = pmd_offset(pud, vaddr);
 	pte = pte_offset_kernel(pmd, vaddr);
 	pkmap_page_table = pte;
@@ -450,6 +458,7 @@
 {
 	unsigned long pfn, va;
 	pgd_t *pgd, *base = swapper_pg_dir;
+	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
@@ -469,7 +478,8 @@
 		if (!pgd_present(*pgd))
 			break;
 
-		pud = pud_offset(pgd, va);
+		p4d = p4d_offset(pgd, va);
+		pud = pud_offset(p4d, va);
 		pmd = pmd_offset(pud, va);
 		if (!pmd_present(*pmd))
 			break;