x86/mm: Fold p4d page table layer at runtime

Change page table helpers to fold p4d at runtime.
The logic is the same as in <asm-generic/pgtable-nop4d.h>.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
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-mm@kvack.org
Link: http://lkml.kernel.org/r/20180214182542.69302-8-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 20 insertions, 6 deletions

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 892df375b615..3fbaad238a94 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -569,14 +569,16 @@ static inline p4dval_t p4d_val(p4d_t p4d)
 
 static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
 {
-        pgdval_t val = native_pgd_val(pgd);
-
-        PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, val);
+        if (pgtable_l5_enabled)
+                PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, native_pgd_val(pgd));
+        else
+                set_p4d((p4d_t *)(pgdp), (p4d_t) { pgd.pgd });
 }
 
 static inline void pgd_clear(pgd_t *pgdp)
 {
-        set_pgd(pgdp, __pgd(0));
+        if (pgtable_l5_enabled)
+                set_pgd(pgdp, __pgd(0));
 }
 
 #endif  /* CONFIG_PGTABLE_LEVELS == 5 */
diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h
index aff42e1da6ee..263c142a6a6c 100644
--- a/arch/x86/include/asm/pgalloc.h
+++ b/arch/x86/include/asm/pgalloc.h
@@ -167,6 +167,8 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
 #if CONFIG_PGTABLE_LEVELS > 4
 static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d)
 {
+        if (!pgtable_l5_enabled)
+                return;
         paravirt_alloc_p4d(mm, __pa(p4d) >> PAGE_SHIFT);
         set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(p4d)));
 }
@@ -191,7 +193,8 @@ extern void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d);
 static inline void __p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d,
                                   unsigned long address)
 {
-        ___p4d_free_tlb(tlb, p4d);
+        if (pgtable_l5_enabled)
+                ___p4d_free_tlb(tlb, p4d);
 }
 
 #endif  /* CONFIG_PGTABLE_LEVELS > 4 */
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 63c2552b6b65..c8baa7f12d1b 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -65,7 +65,7 @@ extern pmdval_t early_pmd_flags;
 
 #ifndef __PAGETABLE_P4D_FOLDED
 #define set_pgd(pgdp, pgd)              native_set_pgd(pgdp, pgd)
-#define pgd_clear(pgd)                  native_pgd_clear(pgd)
+#define pgd_clear(pgd)                  (pgtable_l5_enabled ? native_pgd_clear(pgd) : 0)
 #endif
 
 #ifndef set_p4d
@@ -859,6 +859,8 @@ static inline unsigned long p4d_index(unsigned long address)
 #if CONFIG_PGTABLE_LEVELS > 4
 static inline int pgd_present(pgd_t pgd)
 {
+        if (!pgtable_l5_enabled)
+                return 1;
         return pgd_flags(pgd) & _PAGE_PRESENT;
 }
 
@@ -876,6 +878,8 @@ static inline unsigned long pgd_page_vaddr(pgd_t pgd)
 /* to find an entry in a page-table-directory. */
 static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)
 {
+        if (!pgtable_l5_enabled)
+                return (p4d_t *)pgd;
         return (p4d_t *)pgd_page_vaddr(*pgd) + p4d_index(address);
 }
 
@@ -883,6 +887,9 @@ static inline int pgd_bad(pgd_t pgd)
 {
         unsigned long ignore_flags = _PAGE_USER;
 
+        if (!pgtable_l5_enabled)
+                return 0;
+
         if (IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION))
                 ignore_flags |= _PAGE_NX;
 
@@ -891,6 +898,8 @@ static inline int pgd_bad(pgd_t pgd)
 
 static inline int pgd_none(pgd_t pgd)
 {
+        if (!pgtable_l5_enabled)
+                return 0;
         /*
          * There is no need to do a workaround for the KNL stray
          * A/D bit erratum here.  PGDs only point to page tables