xen/p2m: Mark INVALID_P2M_ENTRY the mfn_list past max_pfn.

commit cf04d120d9413de581437cf9a29f138ec1178f65 upstream.

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>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 468c9e2dde9ba540825c56c51cdb869a81b82805..198df8d5651f923a8e685093158ab1b130801d4b 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -399,21 +399,15 @@ 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];
        }
 }