Merge tag 'stable/for-linus-3.6-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull Xen fix from Konrad Rzeszutek Wilk:
 "Way back in v3.5 we added a mechanism to populate back pages that were
  released (they overlapped with MMIO regions), but neglected to reserve
  the proper amount of virtual space for extend_brk to work properly.

  Coincidentally some other commit aligned the _brk space to larger area
  so I didn't trigger this until it was run on a machine with more than
  2GB of MMIO space."

 * On machines with large MMIO/PCI E820 spaces we fail to boot b/c
   we failed to pre-allocate large enough virtual space for extend_brk.

* tag 'stable/for-linus-3.6-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back.

arch/x86/xen/p2m.c

@@ -194,6 +194,11 @@ RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID
  * boundary violation will require three middle nodes. */
 RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
 
+/* When we populate back during bootup, the amount of pages can vary. The
+ * max we have is seen is 395979, but that does not mean it can't be more.
+ * But some machines can have 3GB I/O holes even. So lets reserve enough
+ * for 4GB of I/O and E820 holes. */
+RESERVE_BRK(p2m_populated, PMD_SIZE * 4);
 static inline unsigned p2m_top_index(unsigned long pfn)
 {
 	BUG_ON(pfn >= MAX_P2M_PFN);