x86: Fix guest_physmap_add_entry checks

guest_physmap_add_entry() checks to see if the given mfn and gpfn
range in the p2m and m2p tables is already mapped before overwriting
the maps, and attempts to do something reasonable so that we don't
have any "dangling" pointers.

Unfortunately, these checks got broken when the page_order argument
was added.  Each individual p2m and m2p entry needs to be checked, not
just the first page in a page order.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index bf97d45c00afe4d63ab852b366376f074a29c9a8..15d5297371b79ef9073c15ad09c9bc6662b36236 100644 (file)
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -953,38 +953,47 @@ guest_physmap_add_entry(struct domain *d, unsigned long gfn,
 
     P2M_DEBUG("adding gfn=%#lx mfn=%#lx\n", gfn, mfn);
 
-    omfn = gfn_to_mfn(d, gfn, &ot);
-    if ( p2m_is_ram(ot) )
+    /* First, remove m->p mappings for existing p->m mappings */
+    for ( i = 0; i < (1UL << page_order); i++ )
     {
-        ASSERT(mfn_valid(omfn));
-        for ( i = 0; i < (1UL << page_order); i++ )
+        omfn = gfn_to_mfn(d, gfn, &ot);
+        if ( p2m_is_ram(ot) )
+        {
+            ASSERT(mfn_valid(omfn));
             set_gpfn_from_mfn(mfn_x(omfn)+i, INVALID_M2P_ENTRY);
+        }
     }
 
-    ogfn = mfn_to_gfn(d, _mfn(mfn));
-    if (
+    /* Then, look for m->p mappings for this range and deal with them */
+    for ( i = 0; i < (1UL << page_order); i++ )
+    {
+        ogfn = mfn_to_gfn(d, _mfn(mfn));
+        if (
 #ifdef __x86_64__
-        (ogfn != 0x5555555555555555L)
+            (ogfn != 0x5555555555555555L)
 #else
-        (ogfn != 0x55555555L)
+            (ogfn != 0x55555555L)
 #endif
-        && (ogfn != INVALID_M2P_ENTRY)
-        && (ogfn != gfn) )
-    {
-        /* This machine frame is already mapped at another physical address */
-        P2M_DEBUG("aliased! mfn=%#lx, old gfn=%#lx, new gfn=%#lx\n",
-                  mfn, ogfn, gfn);
-        omfn = gfn_to_mfn(d, ogfn, &ot);
-        if ( p2m_is_ram(ot) )
+            && (ogfn != INVALID_M2P_ENTRY)
+            && (ogfn != gfn) )
         {
-            ASSERT(mfn_valid(omfn));
-            P2M_DEBUG("old gfn=%#lx -> mfn %#lx\n",
-                      ogfn , mfn_x(omfn));
-            if ( mfn_x(omfn) == mfn )
-                p2m_remove_page(d, ogfn, mfn, page_order);
+            /* This machine frame is already mapped at another physical
+             * address */
+            P2M_DEBUG("aliased! mfn=%#lx, old gfn=%#lx, new gfn=%#lx\n",
+                      mfn, ogfn, gfn);
+            omfn = gfn_to_mfn(d, ogfn, &ot);
+            if ( p2m_is_ram(ot) )
+            {
+                ASSERT(mfn_valid(omfn));
+                P2M_DEBUG("old gfn=%#lx -> mfn %#lx\n",
+                          ogfn , mfn_x(omfn));
+                if ( mfn_x(omfn) == mfn )
+                    p2m_remove_page(d, ogfn, mfn, 0);
+            }
         }
     }
 
+    /* Now, actually do the two-way mapping */
     if ( mfn_valid(_mfn(mfn)) ) 
     {
         if ( !set_p2m_entry(d, gfn, _mfn(mfn), page_order, t) )