x86/espfix: Add support for 5-level paging

We don't need extra virtual address space for ESPFIX, so it stays within
one PUD page table for both 4- and 5-level paging.

Redefining ESPFIX_BASE_ADDR using P4D_SHIFT instead of PGDIR_SHIFT would
make it stay in the same place regarding of paging mode.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
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: 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/20170330080731.65421-8-kirill.shutemov@linux.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/pgtable_64_types.h

@@ -98,7 +98,7 @@ typedef struct { pteval_t pte; } pte_t;
 #define MODULES_END   __fix_to_virt(__end_of_fixed_addresses + 1)
 #define MODULES_LEN   (MODULES_END - MODULES_VADDR)
 #define ESPFIX_PGD_ENTRY _AC(-2, UL)
-#define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << PGDIR_SHIFT)
+#define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << P4D_SHIFT)
 #define EFI_VA_START	 ( -4 * (_AC(1, UL) << 30))
 #define EFI_VA_END	 (-68 * (_AC(1, UL) << 30))
 

arch/x86/kernel/espfix_64.c

@@ -50,11 +50,11 @@
 #define ESPFIX_STACKS_PER_PAGE	(PAGE_SIZE/ESPFIX_STACK_SIZE)
 
 /* There is address space for how many espfix pages? */
-#define ESPFIX_PAGE_SPACE	(1UL << (PGDIR_SHIFT-PAGE_SHIFT-16))
+#define ESPFIX_PAGE_SPACE	(1UL << (P4D_SHIFT-PAGE_SHIFT-16))
 
 #define ESPFIX_MAX_CPUS		(ESPFIX_STACKS_PER_PAGE * ESPFIX_PAGE_SPACE)
 #if CONFIG_NR_CPUS > ESPFIX_MAX_CPUS
-# error "Need more than one PGD for the ESPFIX hack"
+# error "Need more virtual address space for the ESPFIX hack"
 #endif
 
 #define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO)
@@ -121,11 +121,13 @@ static void init_espfix_random(void)
 
 void __init init_espfix_bsp(void)
 {
-	pgd_t *pgd_p;
+	pgd_t *pgd;
+	p4d_t *p4d;
 
 	/* Install the espfix pud into the kernel page directory */
-	pgd_p = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)];
-	pgd_populate(&init_mm, pgd_p, (pud_t *)espfix_pud_page);
+	pgd = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)];
+	p4d = p4d_alloc(&init_mm, pgd, ESPFIX_BASE_ADDR);
+	p4d_populate(&init_mm, p4d, espfix_pud_page);
 
 	/* Randomize the locations */
 	init_espfix_random();