3 files changed, 22 insertions, 8 deletions

diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 5dd5e7b3476f..d2b4ff831477 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -7,7 +7,8 @@ typedef struct {
         unsigned long asce_bits;
         unsigned long asce_limit;
         int noexec;
-        int pgstes;
+        int has_pgste;   /* The mmu context has extended page tables */
+        int alloc_pgste; /* cloned contexts will have extended page tables */
 } mm_context_t;
 
 #endif
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 4c2fbf48c9c4..28ec870655af 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -20,12 +20,25 @@ static inline int init_new_context(struct task_struct *tsk,
 #ifdef CONFIG_64BIT
         mm->context.asce_bits |= _ASCE_TYPE_REGION3;
 #endif
-        if (current->mm->context.pgstes) {
+        if (current->mm->context.alloc_pgste) {
+                /*
+                 * alloc_pgste indicates, that any NEW context will be created
+                 * with extended page tables. The old context is unchanged. The
+                 * page table allocation and the page table operations will
+                 * look at has_pgste to distinguish normal and extended page
+                 * tables. The only way to create extended page tables is to
+                 * set alloc_pgste and then create a new context (e.g. dup_mm).
+                 * The page table allocation is called after init_new_context
+                 * and if has_pgste is set, it will create extended page
+                 * tables.
+                 */
                 mm->context.noexec = 0;
-                mm->context.pgstes = 1;
+                mm->context.has_pgste = 1;
+                mm->context.alloc_pgste = 1;
         } else {
                 mm->context.noexec = s390_noexec;
-                mm->context.pgstes = 0;
+                mm->context.has_pgste = 0;
+                mm->context.alloc_pgste = 0;
         }
         mm->context.asce_limit = STACK_TOP_MAX;
         crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 1a928f84afd6..7fc76133b3e4 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -679,7 +679,7 @@ static inline void pmd_clear(pmd_t *pmd)
 
 static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
-        if (mm->context.pgstes)
+        if (mm->context.has_pgste)
                 ptep_rcp_copy(ptep);
         pte_val(*ptep) = _PAGE_TYPE_EMPTY;
         if (mm->context.noexec)
@@ -763,7 +763,7 @@ static inline int kvm_s390_test_and_clear_page_dirty(struct mm_struct *mm,
         struct page *page;
         unsigned int skey;
 
-        if (!mm->context.pgstes)
+        if (!mm->context.has_pgste)
                 return -EINVAL;
         rcp_lock(ptep);
         pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
@@ -794,7 +794,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
         int young;
         unsigned long *pgste;
 
-        if (!vma->vm_mm->context.pgstes)
+        if (!vma->vm_mm->context.has_pgste)
                 return 0;
         physpage = pte_val(*ptep) & PAGE_MASK;
         pgste = (unsigned long *) (ptep + PTRS_PER_PTE);
@@ -844,7 +844,7 @@ static inline void __ptep_ipte(unsigned long address, pte_t *ptep)
 static inline void ptep_invalidate(struct mm_struct *mm,
                                    unsigned long address, pte_t *ptep)
 {
-        if (mm->context.pgstes) {
+        if (mm->context.has_pgste) {
                 rcp_lock(ptep);
                 __ptep_ipte(address, ptep);
                 ptep_rcp_copy(ptep);