[S390] 1K/2K page table pages.

This patch implements 1K/2K page table pages for s390.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 81 insertions, 21 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 019f518cd5a..809e7789303 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -26,8 +26,14 @@
 
 #ifndef CONFIG_64BIT
 #define ALLOC_ORDER     1
+#define TABLES_PER_PAGE 4
+#define FRAG_MASK       15UL
+#define SECOND_HALVES   10UL
 #else
 #define ALLOC_ORDER     2
+#define TABLES_PER_PAGE 2
+#define FRAG_MASK       3UL
+#define SECOND_HALVES   2UL
 #endif
 
 unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
@@ -45,13 +51,20 @@ unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
                 }
                 page->index = page_to_phys(shadow);
         }
+        spin_lock(&mm->page_table_lock);
+        list_add(&page->lru, &mm->context.crst_list);
+        spin_unlock(&mm->page_table_lock);
         return (unsigned long *) page_to_phys(page);
 }
 
-void crst_table_free(unsigned long *table)
+void crst_table_free(struct mm_struct *mm, unsigned long *table)
 {
         unsigned long *shadow = get_shadow_table(table);
+        struct page *page = virt_to_page(table);
 
+        spin_lock(&mm->page_table_lock);
+        list_del(&page->lru);
+        spin_unlock(&mm->page_table_lock);
         if (shadow)
                 free_pages((unsigned long) shadow, ALLOC_ORDER);
         free_pages((unsigned long) table, ALLOC_ORDER);
@@ -60,37 +73,84 @@ void crst_table_free(unsigned long *table)
 /*
  * page table entry allocation/free routines.
  */
-unsigned long *page_table_alloc(int noexec)
+unsigned long *page_table_alloc(struct mm_struct *mm)
 {
-        struct page *page = alloc_page(GFP_KERNEL);
+        struct page *page;
         unsigned long *table;
+        unsigned long bits;
 
-        if (!page)
-                return NULL;
-        page->index = 0;
-        if (noexec) {
-                struct page *shadow = alloc_page(GFP_KERNEL);
-                if (!shadow) {
-                        __free_page(page);
+        bits = mm->context.noexec ? 3UL : 1UL;
+        spin_lock(&mm->page_table_lock);
+        page = NULL;
+        if (!list_empty(&mm->context.pgtable_list)) {
+                page = list_first_entry(&mm->context.pgtable_list,
+                                        struct page, lru);
+                if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
+                        page = NULL;
+        }
+        if (!page) {
+                spin_unlock(&mm->page_table_lock);
+                page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
+                if (!page)
                         return NULL;
-                }
-                table = (unsigned long *) page_to_phys(shadow);
+                pgtable_page_ctor(page);
+                page->flags &= ~FRAG_MASK;
+                table = (unsigned long *) page_to_phys(page);
                 clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
-                page->index = (addr_t) table;
+                spin_lock(&mm->page_table_lock);
+                list_add(&page->lru, &mm->context.pgtable_list);
         }
-        pgtable_page_ctor(page);
         table = (unsigned long *) page_to_phys(page);
-        clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
+        while (page->flags & bits) {
+                table += 256;
+                bits <<= 1;
+        }
+        page->flags |= bits;
+        if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
+                list_move_tail(&page->lru, &mm->context.pgtable_list);
+        spin_unlock(&mm->page_table_lock);
         return table;
 }
 
-void page_table_free(unsigned long *table)
+void page_table_free(struct mm_struct *mm, unsigned long *table)
 {
-        unsigned long *shadow = get_shadow_pte(table);
+        struct page *page;
+        unsigned long bits;
 
-        pgtable_page_dtor(virt_to_page(table));
-        if (shadow)
-                free_page((unsigned long) shadow);
-        free_page((unsigned long) table);
+        bits = mm->context.noexec ? 3UL : 1UL;
+        bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
+        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+        spin_lock(&mm->page_table_lock);
+        page->flags ^= bits;
+        if (page->flags & FRAG_MASK) {
+                /* Page now has some free pgtable fragments. */
+                list_move(&page->lru, &mm->context.pgtable_list);
+                page = NULL;
+        } else
+                /* All fragments of the 4K page have been freed. */
+                list_del(&page->lru);
+        spin_unlock(&mm->page_table_lock);
+        if (page) {
+                pgtable_page_dtor(page);
+                __free_page(page);
+        }
+}
 
+void disable_noexec(struct mm_struct *mm, struct task_struct *tsk)
+{
+        struct page *page;
+
+        spin_lock(&mm->page_table_lock);
+        /* Free shadow region and segment tables. */
+        list_for_each_entry(page, &mm->context.crst_list, lru)
+                if (page->index) {
+                        free_pages((unsigned long) page->index, ALLOC_ORDER);
+                        page->index = 0;
+                }
+        /* "Free" second halves of page tables. */
+        list_for_each_entry(page, &mm->context.pgtable_list, lru)
+                page->flags &= ~SECOND_HALVES;
+        spin_unlock(&mm->page_table_lock);
+        mm->context.noexec = 0;
+        update_mm(mm, tsk);
 }