nios2: add support for folded p4d page tables

Implement primitives necessary for the 4th level folding, add walks of p4d
level where appropriate and remove usage of __ARCH_USE_5LEVEL_HACK.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: James Morse <james.morse@arm.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20200414153455.21744-7-rppt@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/nios2/include/asm/pgtable.h

@@ -22,7 +22,6 @@
 #include <asm/tlbflush.h>
 
 #include <asm/pgtable-bits.h>
-#define __ARCH_USE_5LEVEL_HACK
 #include <asm-generic/pgtable-nopmd.h>
 
 #define FIRST_USER_ADDRESS	0UL
@@ -100,7 +99,7 @@ extern pte_t invalid_pte_table[PAGE_SIZE/sizeof(pte_t)];
  */
 static inline void set_pmd(pmd_t *pmdptr, pmd_t pmdval)
 {
-	pmdptr->pud.pgd.pgd = pmdval.pud.pgd.pgd;
+	*pmdptr = pmdval;
 }
 
 /* to find an entry in a page-table-directory */

arch/nios2/mm/fault.c

@@ -242,6 +242,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 		 */
 		int offset = pgd_index(address);
 		pgd_t *pgd, *pgd_k;
+		p4d_t *p4d, *p4d_k;
 		pud_t *pud, *pud_k;
 		pmd_t *pmd, *pmd_k;
 		pte_t *pte_k;
@@ -253,8 +254,12 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 			goto no_context;
 		set_pgd(pgd, *pgd_k);
 
-		pud = pud_offset(pgd, address);
-		pud_k = pud_offset(pgd_k, address);
+		p4d = p4d_offset(pgd, address);
+		p4d_k = p4d_offset(pgd_k, address);
+		if (!p4d_present(*p4d_k))
+			goto no_context;
+		pud = pud_offset(p4d, address);
+		pud_k = pud_offset(p4d_k, address);
 		if (!pud_present(*pud_k))
 			goto no_context;
 		pmd = pmd_offset(pud, address);

arch/nios2/mm/ioremap.c

@@ -86,11 +86,15 @@ static int remap_area_pages(unsigned long address, unsigned long phys_addr,
 	if (address >= end)
 		BUG();
 	do {
+		p4d_t *p4d;
 		pud_t *pud;
 		pmd_t *pmd;
 
 		error = -ENOMEM;
-		pud = pud_alloc(&init_mm, dir, address);
+		p4d = p4d_alloc(&init_mm, dir, address);
+		if (!p4d)
+			break;
+		pud = pud_alloc(&init_mm, p4d, address);
 		if (!pud)
 			break;
 		pmd = pmd_alloc(&init_mm, pud, address);