[Xen-changelog] Fix writable pagetables when a flush happens in a different

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 0c5980d0bf20f3806a3aaaeb0e0bf87ac1671f38
# Parent  026e5ef0aa3c8e1af5d70ab01ca4cbeb9c72a64d
Fix writable pagetables when a flush happens in a different
domain, which is temporarily made to run on the wrong
pagetables.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 026e5ef0aa3c -r 0c5980d0bf20 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Fri Jan 13 15:09:45 2006
+++ b/xen/arch/x86/mm.c Fri Jan 13 15:27:45 2006
@@ -3023,12 +3023,25 @@
      * STEP 2. Validate any modified PTEs.
      */
 
-    pl1e = map_domain_page(l1e_get_pfn(pte));
-    modified = revalidate_l1(d, pl1e, d->arch.ptwr[which].page);
-    unmap_domain_page(pl1e);
-    perfc_incr_histo(wpt_updates, modified, PT_UPDATES);
-    ptwr_eip_stat_update(d->arch.ptwr[which].eip, d->domain_id, modified);
-    d->arch.ptwr[which].prev_nr_updates = modified;
+    if ( likely(d == current->domain) )
+    {
+        pl1e = map_domain_page(l1e_get_pfn(pte));
+        modified = revalidate_l1(d, pl1e, d->arch.ptwr[which].page);
+        unmap_domain_page(pl1e);
+        perfc_incr_histo(wpt_updates, modified, PT_UPDATES);
+        ptwr_eip_stat_update(d->arch.ptwr[which].eip, d->domain_id, modified);
+        d->arch.ptwr[which].prev_nr_updates = modified;
+    }
+    else
+    {
+        /*
+         * Must make a temporary global mapping, since we are running in the
+         * wrong address space, so no access to our own mapcache.
+         */
+        pl1e = map_domain_page_global(l1e_get_pfn(pte));
+        modified = revalidate_l1(d, pl1e, d->arch.ptwr[which].page);
+        unmap_domain_page_global(pl1e);
+    }
 
     /*
      * STEP 3. Reattach the L1 p.t. page into the current address space.

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