[PATCH 2/2] xen/p2m: Mark INVALID_P2M_ENTRY the mfn_list past max_pfn.

[Stefan Bader]

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@xxxxxxxxxx>

[backported to 2.6.37]
Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   18 ++++++------------
 1 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 468c9e2..198df8d 100644
--- 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];
 	}
 }

-- 
1.7.0.4



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