x86/mm/vmalloc: Add 5-level paging support

Modify vmalloc_fault() to handle additional page table level.

With 4-level paging, copying happens on p4d level, as we have pgd_none()
always false if p4d_t is folded.

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/20170313143309.16020-6-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 605fd5e8e048d012a7ea507a5baff83f5bf96350..8ad91a01cbc88ff9e53d79ef9a2fd299b8558995 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -435,6 +435,7 @@ void vmalloc_sync_all(void)
 static noinline int vmalloc_fault(unsigned long address)
 {
        pgd_t *pgd, *pgd_ref;
+       p4d_t *p4d, *p4d_ref;
        pud_t *pud, *pud_ref;
        pmd_t *pmd, *pmd_ref;
        pte_t *pte, *pte_ref;
@@ -458,17 +459,37 @@ static noinline int vmalloc_fault(unsigned long address)
        if (pgd_none(*pgd)) {
                set_pgd(pgd, *pgd_ref);
                arch_flush_lazy_mmu_mode();
-       } else {
+       } else if (CONFIG_PGTABLE_LEVELS > 4) {
+               /*
+                * With folded p4d, pgd_none() is always false, so the pgd may
+                * point to an empty page table entry and pgd_page_vaddr()
+                * will return garbage.
+                *
+                * We will do the correct sanity check on the p4d level.
+                */
                BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
        }
 
+       /* With 4-level paging, copying happens on the p4d level. */
+       p4d = p4d_offset(pgd, address);
+       p4d_ref = p4d_offset(pgd_ref, address);
+       if (p4d_none(*p4d_ref))
+               return -1;
+
+       if (p4d_none(*p4d)) {
+               set_p4d(p4d, *p4d_ref);
+               arch_flush_lazy_mmu_mode();
+       } else {
+               BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_ref));
+       }
+
        /*
         * Below here mismatches are bugs because these lower tables
         * are shared:
         */
 
-       pud = pud_offset(pgd, address);
-       pud_ref = pud_offset(pgd_ref, address);
+       pud = pud_offset(p4d, address);
+       pud_ref = pud_offset(p4d_ref, address);
        if (pud_none(*pud_ref))
                return -1;