[Xen-changelog] Remember min and max indices for valid entries in shadow L1 tables.

[BitKeeper Bot <riel@xxxxxxxxxxx>]

ChangeSet 1.1258, 2005/03/23 16:55:23+00:00, mafetter@xxxxxxxxxxxxxxxx

        Remember min and max indices for valid entries in shadow L1 tables.
        Use these to minimize the revalidation effort.
        
        Signed-off-by: michael.fetterman@xxxxxxxxxxxx



 arch/x86/shadow.c        |   39 +++++++++++++++++++++++++++------------
 include/asm-x86/shadow.h |   35 ++++++++++++++++++++++++++++++-----
 2 files changed, 57 insertions(+), 17 deletions(-)


diff -Nru a/xen/arch/x86/shadow.c b/xen/arch/x86/shadow.c
--- a/xen/arch/x86/shadow.c     2005-04-05 12:17:39 -04:00
+++ b/xen/arch/x86/shadow.c     2005-04-05 12:17:39 -04:00
@@ -174,7 +174,8 @@
  * don't want to let those disappear just because no CR3 is currently pointing
  * at it.
  *
- * tlbflush_timestamp holds a pickled pointer to the domain.
+ * tlbflush_timestamp holds a min & max index of valid page table entries
+ * within the shadow page.
  */
 
 static inline unsigned long
@@ -204,7 +205,7 @@
     ASSERT( (gmfn & ~PGT_mfn_mask) == 0 );
     page->u.inuse.type_info = psh_type | gmfn;
     page->count_info = 0;
-    page->tlbflush_timestamp = pickle_domptr(d);
+    page->tlbflush_timestamp = 0;
 
     switch ( psh_type )
     {
@@ -325,8 +326,8 @@
 void free_shadow_page(unsigned long smfn)
 {
     struct pfn_info *page = &frame_table[smfn];
-    struct domain *d = unpickle_domptr(page->tlbflush_timestamp);
     unsigned long gmfn = page->u.inuse.type_info & PGT_mfn_mask;
+    struct domain *d = page_get_owner(pfn_to_page(gmfn));
     unsigned long gpfn = __mfn_to_gpfn(d, gmfn);
     unsigned long type = page->u.inuse.type_info & PGT_type_mask;
 
@@ -1431,25 +1432,34 @@
 
         unsigned long sl1e;
         int index = l1_table_offset(va);
-
-        l1pte_propagate_from_guest(d, gpl1e[index], &sl1e);
-        if ( (sl1e & _PAGE_PRESENT) &&
-             !shadow_get_page_from_l1e(mk_l1_pgentry(sl1e), d) )
-            sl1e = 0;
-        spl1e[index] = sl1e;
+        int min = 1, max = 0;
 
         for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
         {
-            if ( i == index )
-                continue;
             l1pte_propagate_from_guest(d, gpl1e[i], &sl1e);
             if ( (sl1e & _PAGE_PRESENT) &&
                  !shadow_get_page_from_l1e(mk_l1_pgentry(sl1e), d) )
                 sl1e = 0;
             if ( sl1e == 0 )
+            {
+                // First copy entries from 0 until first invalid.
+                // Then copy entries from index until first invalid.
+                //
+                if ( i < index ) {
+                    i = index - 1;
+                    continue;
+                }
                 break;
+            }
             spl1e[i] = sl1e;
+            if ( unlikely(i < min) )
+                min = i;
+            if ( likely(i > max) )
+                max = i;
         }
+
+        frame_table[sl1mfn].tlbflush_timestamp =
+            SHADOW_ENCODE_MIN_MAX(min, max);
     }
 }
 
@@ -1996,6 +2006,8 @@
     unsigned long *guest, *shadow, *snapshot;
     int need_flush = 0, external = shadow_mode_external(d);
     int unshadow;
+    unsigned long min_max;
+    int min, max;
 
     ASSERT(spin_is_locked(&d->arch.shadow_lock));
 
@@ -2020,7 +2032,10 @@
 
         switch ( stype ) {
         case PGT_l1_shadow:
-            for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
+            min_max = pfn_to_page(smfn)->tlbflush_timestamp;
+            min = SHADOW_MIN(min_max);
+            max = SHADOW_MAX(min_max);
+            for ( i = min; i <= max; i++ )
             {
                 unsigned new_pte = guest[i];
                 if ( new_pte != snapshot[i] )
diff -Nru a/xen/include/asm-x86/shadow.h b/xen/include/asm-x86/shadow.h
--- a/xen/include/asm-x86/shadow.h      2005-04-05 12:17:39 -04:00
+++ b/xen/include/asm-x86/shadow.h      2005-04-05 12:17:39 -04:00
@@ -52,6 +52,10 @@
 #define shadow_lock(_d)      do { 
ASSERT(!spin_is_locked(&(_d)->arch.shadow_lock)); 
spin_lock(&(_d)->arch.shadow_lock); } while (0)
 #define shadow_unlock(_d)    spin_unlock(&(_d)->arch.shadow_lock)
 
+#define SHADOW_ENCODE_MIN_MAX(_min, _max) (((L1_PAGETABLE_ENTRIES - (_max)) << 
16) | (_min))
+#define SHADOW_MIN(_encoded) ((_encoded) & ((1u<<16) - 1))
+#define SHADOW_MAX(_encoded) (L1_PAGETABLE_ENTRIES - ((_encoded) >> 16))
+
 extern void shadow_mode_init(void);
 extern int shadow_mode_control(struct domain *p, dom0_shadow_control_t *sc);
 extern int shadow_fault(unsigned long va, struct xen_regs *regs);
@@ -187,13 +191,9 @@
 /************************************************************************/
 
 struct shadow_status {
-    unsigned long gpfn_and_flags; /* Guest pfn plus flags. */
     struct shadow_status *next;   /* Pull-to-front list per hash bucket. */
+    unsigned long gpfn_and_flags; /* Guest pfn plus flags. */
     unsigned long smfn;           /* Shadow mfn.           */
-
-    // Pull-to-front list of L1s/L2s from which we check when removing
-    // write access to a page.
-    //struct list_head next_to_check;
 };
 
 #define shadow_ht_extra_size 128
@@ -1290,6 +1290,29 @@
 
 /************************************************************************/
 
+void static inline
+shadow_update_min_max(unsigned long smfn, int index)
+{
+    struct pfn_info *sl1page = pfn_to_page(smfn);
+    unsigned long min_max = sl1page->tlbflush_timestamp;
+    int min = SHADOW_MIN(min_max);
+    int max = SHADOW_MAX(min_max);
+    int update = 0;
+
+    if ( index < min )
+    {
+        min = index;
+        update = 1;
+    }
+    if ( index > max )
+    {
+        max = index;
+        update = 1;
+    }
+    if ( update )
+        sl1page->tlbflush_timestamp = SHADOW_ENCODE_MIN_MAX(min, max);
+}
+
 extern void shadow_map_l1_into_current_l2(unsigned long va);
 
 void static inline
@@ -1357,6 +1380,8 @@
     }
 
     shadow_linear_pg_table[l1_linear_offset(va)] = mk_l1_pgentry(new_spte);
+
+    shadow_update_min_max(sl2e >> PAGE_SHIFT, l1_table_offset(va));
 }
 
 /************************************************************************/

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