Ignore pinning of other than root page directories. Disallow

creation of pagetables with 'va_unknown' page-directory backptrs.

Signed-off-by: Keir Fraser <keir@xensource.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index c5d958a8847b6c0ff66830d6b57f9e5c04fcc22d..e4af8e1263eeaecb63c4dca2e72634378611d4d5 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -777,9 +777,7 @@ static inline int l1_backptr(
     unsigned long *backptr, unsigned long offset_in_l2, unsigned long l2_type)
 {
     unsigned long l2_backptr = l2_type & PGT_va_mask;
-    BUG_ON(l2_backptr == PGT_va_unknown);
-    if ( l2_backptr == PGT_va_mutable )
-        return 0;
+    ASSERT(l2_backptr != PGT_va_unknown);
     *backptr = 
         ((l2_backptr >> PGT_va_shift) << L3_PAGETABLE_SHIFT) | 
         (offset_in_l2 << L2_PAGETABLE_SHIFT);
@@ -793,8 +791,7 @@ static inline int l1_backptr(
     unsigned long *backptr, unsigned long offset_in_l2, unsigned long l2_type)
 {
     unsigned long l2_backptr = l2_type & PGT_va_mask;
-    BUG_ON(l2_backptr == PGT_va_unknown);
-
+    ASSERT(l2_backptr != PGT_va_unknown);
     *backptr = ((l2_backptr >> PGT_va_shift) << L3_PAGETABLE_SHIFT) | 
         (offset_in_l2 << L2_PAGETABLE_SHIFT);
     return 1;
@@ -804,8 +801,7 @@ static inline int l2_backptr(
     unsigned long *backptr, unsigned long offset_in_l3, unsigned long l3_type)
 {
     unsigned long l3_backptr = l3_type & PGT_va_mask;
-    BUG_ON(l3_backptr == PGT_va_unknown);
-
+    ASSERT(l3_backptr != PGT_va_unknown);
     *backptr = ((l3_backptr >> PGT_va_shift) << L4_PAGETABLE_SHIFT) | 
         (offset_in_l3 << L3_PAGETABLE_SHIFT);
     return 1;
@@ -814,9 +810,6 @@ static inline int l2_backptr(
 static inline int l3_backptr(
     unsigned long *backptr, unsigned long offset_in_l4, unsigned long l4_type)
 {
-    unsigned long l4_backptr = l4_type & PGT_va_mask;
-    BUG_ON(l4_backptr == PGT_va_unknown);
-
     *backptr = (offset_in_l4 << L4_PAGETABLE_SHIFT);
     return 1;
 }
@@ -1438,13 +1431,6 @@ void put_page_type(struct page_info *page)
                 nx &= ~PGT_validated;
             }
         }
-        else if ( unlikely(((nx & (PGT_pinned | PGT_count_mask)) == 
-                            (PGT_pinned | 1)) &&
-                           ((nx & PGT_type_mask) != PGT_writable_page)) )
-        {
-            /* Page is now only pinned. Make the back pointer mutable again. */
-            nx |= PGT_va_mutable;
-        }
     }
     while ( unlikely((y = cmpxchg(&page->u.inuse.type_info, x, nx)) != x) );
 }
@@ -1527,20 +1513,17 @@ int get_page_type(struct page_info *page, unsigned long type)
                                 get_gpfn_from_mfn(page_to_mfn(page)));
                     return 0;
                 }
-                else if ( (x & PGT_va_mask) == PGT_va_mutable )
-                {
-                    /* The va backpointer is mutable, hence we update it. */
-                    nx &= ~PGT_va_mask;
-                    nx |= type; /* we know the actual type is correct */
-                }
-                else if ( ((type & PGT_va_mask) != PGT_va_mutable) &&
-                          ((type & PGT_va_mask) != (x & PGT_va_mask)) )
+                else
                 {
+                    ASSERT((type & PGT_va_mask) != (x & PGT_va_mask));
 #ifdef CONFIG_X86_PAE
                     /* We use backptr as extra typing. Cannot be unknown. */
                     if ( (type & PGT_type_mask) == PGT_l2_page_table )
                         return 0;
 #endif
+                    /* Fixme: add code to propagate va_unknown to subtables. */
+                    if ( (type & PGT_type_mask) >= PGT_l2_page_table )
+                        return 0;
                     /* This table is possibly mapped at multiple locations. */
                     nx &= ~PGT_va_mask;
                     nx |= PGT_va_unknown;
@@ -1818,12 +1801,17 @@ int do_mmuext_op(
         switch ( op.cmd )
         {
         case MMUEXT_PIN_L1_TABLE:
-            type = PGT_l1_page_table | PGT_va_mutable;
+        case MMUEXT_PIN_L2_TABLE:
+        case MMUEXT_PIN_L3_TABLE:
+        case MMUEXT_PIN_L4_TABLE:
+            if ( (op.cmd - MMUEXT_PIN_L1_TABLE) != (CONFIG_PAGING_LEVELS - 1) )
+                break;
 
-        pin_page:
             if ( shadow_mode_refcounts(FOREIGNDOM) )
                 break;
 
+            type = PGT_root_page_table;
+
             okay = get_page_and_type_from_pagenr(mfn, type, FOREIGNDOM);
             if ( unlikely(!okay) )
             {
@@ -1842,20 +1830,6 @@ int do_mmuext_op(
             
             break;
 
-#ifndef CONFIG_X86_PAE /* Unsafe on PAE because of Xen-private mappings. */
-        case MMUEXT_PIN_L2_TABLE:
-            type = PGT_l2_page_table | PGT_va_mutable;
-            goto pin_page;
-#endif
-
-        case MMUEXT_PIN_L3_TABLE:
-            type = PGT_l3_page_table | PGT_va_mutable;
-            goto pin_page;
-
-        case MMUEXT_PIN_L4_TABLE:
-            type = PGT_l4_page_table | PGT_va_mutable;
-            goto pin_page;
-
         case MMUEXT_UNPIN_TABLE:
             if ( shadow_mode_refcounts(d) )
                 break;
@@ -3376,7 +3350,7 @@ int ptwr_do_page_fault(struct domain *d, unsigned long addr,
     
     /* Get the L2 index at which this L1 p.t. is always mapped. */
     l2_idx = page->u.inuse.type_info & PGT_va_mask;
-    if ( unlikely(l2_idx >= PGT_va_unknown) )
+    if ( unlikely(l2_idx == PGT_va_unknown) )
         goto emulate; /* Urk! This L1 is mapped in multiple L2 slots! */
     l2_idx >>= PGT_va_shift;
 

diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 8cfe942e8e202cc882106b76220f22e59ad0305b..74917fd2266bf2f688ea6e30d3b4363f82467315 100644 (file)
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -81,18 +81,14 @@ struct page_info
  /* The 11 most significant bits of virt address if this is a page table. */
 #define PGT_va_shift        16
 #define PGT_va_mask         (((1U<<11)-1)<<PGT_va_shift)
- /* Is the back pointer still mutable (i.e. not fixed yet)? */
-#define PGT_va_mutable      (((1U<<11)-1)<<PGT_va_shift)
  /* Is the back pointer unknown (e.g., p.t. is mapped at multiple VAs)? */
-#define PGT_va_unknown      (((1U<<11)-2)<<PGT_va_shift)
+#define PGT_va_unknown      (((1U<<11)-1)<<PGT_va_shift)
 #elif defined(__x86_64__)
  /* The 27 most significant bits of virt address if this is a page table. */
 #define PGT_va_shift        32
 #define PGT_va_mask         ((unsigned long)((1U<<28)-1)<<PGT_va_shift)
- /* Is the back pointer still mutable (i.e. not fixed yet)? */
-#define PGT_va_mutable      ((unsigned long)((1U<<28)-1)<<PGT_va_shift)
  /* Is the back pointer unknown (e.g., p.t. is mapped at multiple VAs)? */
-#define PGT_va_unknown      ((unsigned long)((1U<<28)-2)<<PGT_va_shift)
+#define PGT_va_unknown      ((unsigned long)((1U<<28)-1)<<PGT_va_shift)
 #endif
 
  /* 16-bit count of uses of this frame as its current type. */