x86/shadow: slightly consolidate sh_unshadow_for_p2m_change() (part III)

In preparation for reactivating the presently dead 2M page path of the
function, also deal with the case of replacing an L1 page table all in
one go. Note that the prior comparing of MFNs to bypass the removal of
shadows was insufficient (but kind of benign, for being dead code so
far) - at the very least the R/W bit also needs considering there (to be
on the safe side, compare the full [virtual] PTEs).

While adjusting the first conditional in the loop for the use of the new
local variable "nflags", also drop mfn_valid(): If anything we'd need to
compare against INVALID_MFN, but that won't come out of l1e_get_mfn().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tim Deegan <tim@xen.org>

diff --git a/xen/arch/x86/mm/shadow/hvm.c b/xen/arch/x86/mm/shadow/hvm.c
index 0c670551f765dc91a252829f1f4020d1d5f26809..c084bc8ed71f2e230b748322fcf1629c554ca9e5 100644 (file)
--- a/xen/arch/x86/mm/shadow/hvm.c
+++ b/xen/arch/x86/mm/shadow/hvm.c
@@ -844,40 +844,65 @@ static void cf_check sh_unshadow_for_p2m_change(
      * scheme, that's OK, but otherwise they must be unshadowed.
      */
     case 2:
-        if ( !(oflags & _PAGE_PSE) )
-            break;
-
-        ASSERT(!p2m_is_grant(p2mt));
-
         {
             unsigned int i;
             mfn_t nmfn = l1e_get_mfn(new);
-            l1_pgentry_t *npte = NULL;
+            unsigned int nflags = l1e_get_flags(new);
+            l1_pgentry_t *npte = NULL, *opte = NULL;
 
+            BUILD_BUG_ON(_PAGE_PAT != _PAGE_PSE);
+
+            if ( !(nflags & _PAGE_PRESENT) )
+                nmfn = INVALID_MFN;
             /* If we're replacing a superpage with a normal L1 page, map it */
-            if ( (l1e_get_flags(new) & _PAGE_PRESENT) &&
-                 !(l1e_get_flags(new) & _PAGE_PSE) &&
-                 mfn_valid(nmfn) )
+            else if ( !(nflags & _PAGE_PSE) )
                 npte = map_domain_page(nmfn);
+            else if ( !(mfn_x(nmfn) & (_PAGE_PSE_PAT >> PAGE_SHIFT)) )
+                nflags &= ~_PAGE_PSE;
+            else
+                nmfn = mfn_add(nmfn, -(long)(_PAGE_PSE_PAT >> PAGE_SHIFT));
+
+            /* If we're replacing a normal L1 page, map it as well. */
+            if ( !(oflags & _PAGE_PSE) )
+                opte = map_domain_page(omfn);
+            else if ( !(mfn_x(omfn) & (_PAGE_PSE_PAT >> PAGE_SHIFT)) )
+                oflags &= ~_PAGE_PSE;
+            else
+                omfn = mfn_add(omfn, -(long)(_PAGE_PSE_PAT >> PAGE_SHIFT));
 
             gfn &= ~(L1_PAGETABLE_ENTRIES - 1);
 
             for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
             {
-                if ( !npte ||
-                     !(l1e_get_flags(npte[i]) & _PAGE_PRESENT) ||
-                     !mfn_eq(l1e_get_mfn(npte[i]), omfn) )
+                if ( opte )
+                {
+                    oflags = l1e_get_flags(opte[i]);
+                    if ( !(oflags & _PAGE_PRESENT) )
+                        continue;
+                    omfn = l1e_get_mfn(opte[i]);
+                }
+
+                if ( npte )
+                {
+                    nflags = l1e_get_flags(npte[i]);
+                    nmfn = nflags & _PAGE_PRESENT
+                           ? l1e_get_mfn(npte[i]) : INVALID_MFN;
+                }
+
+                if ( !mfn_eq(nmfn, omfn) || nflags != oflags )
                 {
                     /* This GFN->MFN mapping has gone away */
                     sh_remove_all_shadows_and_parents(d, omfn);
                     if ( sh_remove_all_mappings(d, omfn, _gfn(gfn + i)) )
                         flush = true;
                 }
+
                 omfn = mfn_add(omfn, 1);
+                nmfn = mfn_add(nmfn, !mfn_eq(nmfn, INVALID_MFN));
             }
 
-            if ( npte )
-                unmap_domain_page(npte);
+            unmap_domain_page(opte);
+            unmap_domain_page(npte);
         }
 
         break;