2 files changed, 20 insertions, 2 deletions

diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index 9d30105a0c4a..6a6fe8939645 100644
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -126,7 +126,7 @@ static const struct pv_irq_ops xen_irq_ops __initdata = {
 #endif
 };
 
-void __init xen_init_irq_ops()
+void __init xen_init_irq_ops(void)
 {
         pv_irq_ops = xen_irq_ops;
         x86_init.irqs.intr_init = xen_init_IRQ;
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8f2251d2a3f8..ddc81a06edb9 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -237,7 +237,25 @@ void __init xen_build_dynamic_phys_to_machine(void)
                         p2m_top[topidx] = mid;
                 }
 
-                p2m_top[topidx][mididx] = &mfn_list[pfn];
+                /*
+                 * As long as the mfn_list has enough entries to completely
+                 * fill a p2m page, pointing into the array is ok. But if
+                 * not the entries beyond the last pfn will be undefined.
+                 * And guessing that the 'what-ever-there-is' does not take it
+                 * too kindly when changing it to invalid markers, a new page
+                 * is allocated, initialized and filled with the valid part.
+                 */
+                if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
+                        unsigned long p2midx;
+                        unsigned long *p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
+                        p2m_init(p2m);
+
+                        for (p2midx = 0; pfn + p2midx < max_pfn; p2midx++) {
+                                p2m[p2midx] = mfn_list[pfn + p2midx];
+                        }
+                        p2m_top[topidx][mididx] = p2m;
+                } else
+                        p2m_top[topidx][mididx] = &mfn_list[pfn];
         }
 
         m2p_override_init();