xen/p2m: Mark INVALID_P2M_ENTRY the mfn_list past max_pfn.

In case the mfn_list does not have enough entries to fill
a p2m page we do not want the entries from max_pfn up to
the boundary to be filled with unknown values. Hence
set them to INVALID_P2M_ENTRY.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 6 insertions, 12 deletions

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index ddc81a06edb9..fd12d7ce7ff9 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -241,21 +241,15 @@ void __init xen_build_dynamic_phys_to_machine(void)
                  * 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];
+
+                        p2midx = max_pfn % P2M_PER_PAGE;
+                        for ( ; p2midx < P2M_PER_PAGE; p2midx++)
+                                mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
+                }
+                p2m_top[topidx][mididx] = &mfn_list[pfn];
         }
 
         m2p_override_init();