# HG changeset patch
# User George Dunlap <george.dunlap@eu.citrix.com>
# Date 1295274541 0
# Node ID 3decd02e0b18ae21fb926c6bad96a4cd02c48272
# Parent  97ab84aca65cdcbce2ddccc51629fb24adb056cf
PoD,hap: Fix logdirty mode when using hardware assisted paging

When writing a writable p2m entry for a pfn, we need to mark the pfn
dirty to avoid corruption when doing live migration.

Marking the page dirty exposes another issue, where there are
excessive sweeps for zero pages if there's a mismatch between PoD
entries and cache entries.  Only sweep for zero pages if we actually
need more memory.

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

Index: xen-4.0.2-testing/xen/arch/x86/mm/p2m.c
===================================================================
--- xen-4.0.2-testing.orig/xen/arch/x86/mm/p2m.c
+++ xen-4.0.2-testing/xen/arch/x86/mm/p2m.c
@@ -1064,14 +1064,22 @@ p2m_pod_demand_populate(struct domain *d
     if ( unlikely(d->is_dying) )
         goto out_fail;
 
-    /* If we're low, start a sweep */
-    if ( order == 9 && page_list_empty(&p2md->pod.super) )
-        p2m_pod_emergency_sweep_super(d);
-
-    if ( page_list_empty(&p2md->pod.single) &&
-         ( ( order == 0 )
-           || (order == 9 && page_list_empty(&p2md->pod.super) ) ) )
-        p2m_pod_emergency_sweep(d);
+    /* Once we've ballooned down enough that we can fill the remaining
+     * PoD entries from the cache, don't sweep even if the particular
+     * list we want to use is empty: that can lead to thrashing zero pages
+     * through the cache for no good reason.  */
+    if ( p2md->pod.entry_count > p2md->pod.count )
+    {
+
+        /* If we're low, start a sweep */
+        if ( order == 9 && page_list_empty(&p2md->pod.super) )
+            p2m_pod_emergency_sweep_super(d);
+
+        if ( page_list_empty(&p2md->pod.single) &&
+             ( ( order == 0 )
+               || (order == 9 && page_list_empty(&p2md->pod.super) ) ) )
+            p2m_pod_emergency_sweep(d);
+    }
 
     /* Keep track of the highest gfn demand-populated by a guest fault */
     if ( q == p2m_guest && gfn > p2md->pod.max_guest )
@@ -1098,7 +1106,10 @@ p2m_pod_demand_populate(struct domain *d
     set_p2m_entry(d, gfn_aligned, mfn, order, p2m_ram_rw);
 
     for( i = 0 ; i < (1UL << order) ; i++ )
+    {
         set_gpfn_from_mfn(mfn_x(mfn) + i, gfn_aligned + i);
+        paging_mark_dirty(d, mfn_x(mfn) + i);
+    }
     
     p2md->pod.entry_count -= (1 << order); /* Lock: p2m */
     BUG_ON(p2md->pod.entry_count < 0);